eChapters

Meat is considered as well balanced diet because it is good source of macro and micro nutrients.

Macronutrients-required in large quantity in body i.e proteins, fat and carbohydrates.

Micronutrients-required in lesser quantity by human body i.e vitamins, minerals and fibers.

Organ meat like liver is a good source of glycogen, viatm-A, B1 and nicotinic acid.

Fresh meat is unprocessed.

Raw meat is a fresh meat undergone chilling and freezing.

Refrigeration and rapid cooling can delay the onset of rigor mortis

General Terminologies in Livestock Production

Embry Transfer Technology (ETT)

Definition: The process of removing one or more embryos from the reproductive tract of a donor female and transferring them to one or more recipient females.

Farming System of India

Based on how income is derived from a farming enterprise: Specialized farming, diversified farming and mixed farming.

Based on mode of ownership and organization of farms: Individually owned, co-operative farming and collective farming

Based on scale of operations: Small scale farming and Large scale farming.

Animal Biotechnology

Biotechnology is defined as “the application of biological organisms, systems or processes to manufacturing and service industries” (Coombs, 1984).

It is also defined as “the application of scientific and engineering principles to the processing of materials by biological agents to produce goods and services” (Coleman, 1986).

Animalbiotechnologyis the application of scientific and engineeringprinciples to the processing or production of materials by animals to provide goods and services to human kind.

1665 Robert Hooke had successfully invented the microscope. Because of this discovery, Robert Hooke was the first one to have a close look of a cell appears to be. His description of these cells was published in Micrographia. However, the cell walls observed by Hooke gave no indication of the nucleus and other organelles found in most living cells.

1674 Anton van Leeuwenhoek witnessed a live cell (plant) under a microscope.

1775 Antoine Lavoisier first proposed a mechanism for photosynthesis, a process wherein plants plants take in carbon dioxide and release oxygen. Lavoisier was also the first to investigate cell respiration in animals.

1777-83 Chemistry became dominated by the phlogiston theory, or the hypothetical principle of fire wherein all the combustible material was part composed. In this principle, burning (oxidation) was caused by liberating phlogiston, with ash as the dephlogistigated substance.

1836 The proponent of the cell theory in Biology, Theodore Schwann, proposed that the process of fermentation is solely limited to living yeast cells in 1836. Liebig did not agree to this and instead, he proposed another alternative theory of fermentation.

1856 Louis Pasteur opposed Liebig’s chemical theory. In his experiment, he showed that fermentation depends highly on the physiological functions that occur in bacteria and in living yeast cells. This work of Pasteur in 1856 received general recognition.

1860s The view on the chemistry of life highly different from the chemistry of nonliving things. During this period, the view is that the gelatinous and homogenous form of matter in organisms or more commonly known as the protoplasm carries out all the intracellular processes. These include respiration, biosynthesis of molecules, and the breakdown of matter.

Partitioning of Energy in Livestock

Energy Partitioning

Partitioning of energy involves loss and distribution of feed energy into different body functions.

Gross energy is calculated from the heat produced when a sample of feed or feces is subjected to complete combustion in a bomb calorimeter under a pressurized oxygen atmosphere.

Apparent digestible energy is the difference between the gross energy of the feed consumed and the gross energy of the feces excreted. Digestion is accompanied by the production of gases in both fore- and hindgut and by the urinary excretion of metabolites.

Metabolizable energy is the difference between digestible energy and energy lost to gases and urine. Metabolic processes and physical activity produce heat (heat of production) which may warm the animal in cold weather. In hot weather, energy may be required to expel excess heat of production, through panting and increased respiratory rate.

Net energy is the remaining energy available for maintenance, reproduction and production. The diagram on the left illustrates energy partitioning for a particular cow near the end of her lactation. Energetic efficiency of this cow is about 29%, expressed as output in the form of milk, gain and fetal growth divided by gross energy input. Although their energy requirements are significantly greater, higher producing cows are also more energetically efficient.

Histology

Cell: Structural and functional unit of an organism

M. Schleiden & Theodor Schwan – proposed cell theory

- All living being made up of cell

Tissue: Group of cell and their extracellular product organized to perform a particular function

M. Malpighii – Father of histology

Sites for surgical interventions

Luxation of patella in cattle and horses

The luxation of patella is a condition wherein the patella of the stifle joint (femoropatellar articulation) is locked above the medial ridge of the trochlea of the femur.

Anatomy of femoropatellar articulation of the stifle joint

The stifle joint is a composite joint formed in two parts. One of these is an articulation between the condyles of distal extremity of femur and the condyles of the proximal extremity of tibia (femoro-tibial articulation) and the other is the articulation between the trochlea of the distal extremity of the femur and the articular surface of the patella (femoro-patellar articulation).

The trochlea of the femur consists of two asymmetrical ridges separated by a groove. The medial ridge is more prominent, wider and a little more extended dorsally than the lateral ridge. The two ridges converge ventrally. The articular surface of the patella is more or less quadrilateral or triangular with the base above and apex below. It has a vertical ridge in the middle and it separates the two concave areas of which the medial one is larger than the lateral. The patella is fastened against the trochlea with the help of three types of ligaments. One of these is the capsular ligament which is attached to the periphery of the articular areas of the two segments of the joint. The other one is the medial and lateral collateral ligaments. The third set of ligaments is the patellar (straight) ligaments.

Horse

The lumbosacral plexus in horse is formed by last three lumbar and first two sacral nerves, similar to that in ox. The caudal gluteal nerve divides into two branches. The medial branch supplies the superficial gluteal muscle in addition to the middle and deep gluteal and biceps femoris muscles. The lateral branch reaches the level of tuber ischii and terminates into the semitendinosus muscle at the perineal region. The sciatic nerve is almost similar to that of ox in the disposition and distribution of its branches. The superficial and deep peroneal nerves are also similar to those of ox. The tibial nerve divides at the distal third of the leg into medial and lateral plantar nerves. Each plantar nerve divides at the fetlock into cranial, middle and caudal digital nerves.

Dog

The lumbosacral plexus in dog is formed by the last four or five lumbar and first two or three sacral nerves. The cranial gluteal nerve receives fibres from sixth and seventh lumbar and first and second sacral nerves. The caudal gluteal nerve arises from sixth and seventh lumbar and first sacral nerves. The sciatic nerve derives fibres from sixth and seventh lumbar and first and second sacral nerves. The lateral cutaneous nerve arises either from sciatic or from the peroneal nerve. The peroneal nerve divides into superficial and deep branches, similar to those of ox. The tibial nerve divides into medial and lateral plantar nerves at the level of distal third of the leg. The medial plantar nerve divides at the metatarsus into medial and lateral branches. The medial branch becomes the first plantar common digital nerve. It divides to form the plantar proper digital nerves of the first and second digits. The lateral branch divides into three plantar metatarsal nerves which unite, in the intermetatarsal space with the three plantar common digital nerves of the lateral plantar nerve. Each of these united plantar common digital nerves descends and after reaching at the metatarso-phalangeal articulation into three plantar proper digital nerves. The lateral plantar nerve, divides into three plantar common digital nerves which join the three plantar metatarsal nerves and form the plantar (caudal) proper digital nerves. The united proper digital nerves supply the second to fifth digit and terminate into the corresponding intermetatarsal space.

Pelvic (Lumbosacral) plexus

The hind limb is supplied by the nerve branches extending from the Pelvic (lumbosacral) plexus (Fig. 6-4 A and B) which is formed by the convergence of the ventral divisions of the last three lumbar and first two sacral nerves. It is formed in two parts, the cranial and caudal. The two parts are connected by anastomotic branches. The cranial (lumbar) part is formed by the fourth and fifth lumbar nerves and lies between the psoas major and psoas minor muscles while the caudal (sacral) part is formed by the sixth lumbar and first and second sacral nerves. Some times a root from third sacral also joins this part. It lies on the pelvic surface of the sacrosciatic (ischial) ligament. The nerves extending from the cranial part of the plexus are the lateral cutaneous femoral, the femoral and the obturator. The nerves extending from the caudal part are the cranial gluteal, caudal gluteal and the sciatic (ischiatic).

Lateral cutaneous femoral nerve

The lateral cutaneous femoral nerve while leaving the cranial part of the plexus, receives fibres from the fourth lumbar nerve, passes caudally between the psoas major and psoas minor muscles and reaches the tuber coxae. Here it perforates the obliquus abdominis externus muscle in company with the circumflex iliac artery and reaches the skin of the lateral aspect of the thigh. In this course, the nerve supplies the psoas major, psoas minor, iliacus and external oblique muscles of the abdomen and the skin and cutaneous muscle on the lateral face of the thigh.

Horse

The arteries of the hind limb of horse have in general similar architecture as that of ox except the special features mentioned below.

The deep circumflex iliac artery which is a branch of the external iliac artery in ox has a variable origin in horse. It may originate directly from the aorta or the common iliac trunk just prior to the origin of the external iliac artery. The prepubic and deep femoral arteries arise either by a common trunk or separately from the femoral artery. The obturator artery is a well developed independent branch of the femoral artery in horse as against its origin as a branch of deep femoral artery in ox. The saphenous artery is a small branch of femoral artery and it supplies the skin on the medial aspect of the thigh and leg. The popliteal artery terminates by its division into cranial and caudal tibial arteries at a lower level in horse than that in ox. The caudal tibial artery is larger and longer in horse than that in ox. From the proximal plantar arch extend four caudal metatarsal arteries instead of four, two of them are superficial and the other two deep branches. The large metatarsal artery descends along the groove between the large and lateral small metatarsal bone and divides just above the fetlock into lateral and medial digital arteries. Each digital artery divides at the middle of the wing of the third phalanx into preplantar and plantar digital arteries. The preplantar digital arteries supply the sensitive laminae of the sole. The plantar digital arteries of the opposite sides form anastomosis. Small laminar branches from the anastomosis form the circumflex artery of the toe which supplies branches to the sole.

The lymphatics of hind limb is comprised of four lymph nodes namely the deep inguinal, epigastric, coxal and popliteal lymph nodes and the afferents and efferent ducts joining and leaving these lymph nodes.

Deep inguinal lymph node

The deep inguinal lymph node is located in the region of deep femoral artery near the origin of the caudal epigastric and the pudic branches from it. The lymph node receives afferents from the muscles in the prepubic and the thigh regions. The efferent vessel from this lymph node joins and opens in the medial iliac lymph node.

Epigastric lymph node

The epigastric lymph node is inconstant. When present, it is located on the course of the caudal epigastric artery near the pubis on the medial surface of the rectus abdominis muscle. The afferents for this lymph node are received from the abdominal muscles and the peritoneum in the vicinity. The efferent vessel of this lymph node joins the medial iliac lymph node.

The venous drainage of hind limb begins from two digital venous plexuses, one for each digit, situated in the corium of the foot. From each of these plexuses extend three digital veins namely the dorsal common digital vein, the medial digital vein and the lateral digital vein. The digital veins in their upward course converge and form the metatarsal veins which in their turn continue upward in the leg region as tibial and popliteal veins and then in the thigh region as femoral vein which finally joins the external iliac vein as the chief vein of the hind limb.

Digital veins

The dorsal common digital vein arises from the corresponding digital plexus in the form of proper digital vein.The two proper digital veins ascend along the medial face of the corresponding digit and unite at about the middle of the interdigital space below the metatarso-phalangeal articulation (fetlock joint) and form the dorsal common digital vein. The later, thus formed, ascends through the interdigital space, crosses vertically the metatarso-phalangeal articulation and after reaching the distal extremity of the metatarsal bone continues upward as dorsal metatarsal vein.

The medial digital vein after arising from the digital venous plexus ascends along the caudomedial aspect of the medial digit in company with the satellite artery, shares a branch each from the dorsal common digital and lateral digital veins, ascends the medial face of the fetlock joint and is then continued up as the medial plantar metatarsal vein.

The lateral digital vein after arising from the digital venous plexus of the lateral digit passes upward in the interdigital space, communicates a branch to the dorsal common digital and medial digital veins and then ascends the lateral face of the fetlock joint and then is continued up as the lateral plantar metatarsal vein.

The main arterial trunk that supplies blood to the hind limb is the external iliac artery. As this trunk passes down through different segments (regions) of the limb it is differently named according to that segment or the region. In the abdomen it is named as iliac, in the thigh region as femoral, in the leg region as tibial and popliteal and down that the metatarsal artery and lastly the digital.

External iliac artery

The external iliac artery arises from the abdominal aorta ventral to the fifth or sixth lumbar vertebra. It descends at the side of the pelvic inlet ventrally and caudally along the tendon of psoas minor, crosses the tendon, reaches the cranial border of the pubis, gains the space between the sartorius and pectineus muscles and then continues in the thigh (femoral region) as the femoral artery. In this course it is covered by peritoneum and is related laterally to the psoas minor, sartorius and iliacus muscles, medially to the common iliac vein and caudally to the external iliac vein. The following are the collateral branches of the external iliac artery.

Horse

The tensor fasciae latae is less extensive.

The superficial gluteus exists separately. It is ‘V’ shaped. It originates from the lateral angle of ilium (tuber coxae) and gluteal fascia and is inserted to the third trochanter. The middle gluteus is the largest of the three gluteal muscles and is very extensive. It originates from the aponeurosis of the longissimus dorsi, extends as far forwards up to first lumbar vertebra and is inserted in three heads, to the trochanter major, the crest ventral to trochanter major and the trochanteric ridge. The deep gluteus is smaller than the middle gluteus and is inserted to the convexity of the trochanter major.

The biceps femoris has an additional insertion to the femur on the rough surface near the trochanter tertius.

The semitendinosus arises from the transverse processes of the first two or three coccygeal vertebrae. The semimembranosus is larger and arises from the sacrosciatic ligament also.

The sartorius does not arise from the shaft of the ilium. The gracilis is not so extensively fused to its fellow at the origin.

The obturator internus has an iliac part- the pisiformis. Its tendon passes through the lesser sciatic foramen and hence does not unite with that of the obturator externus.

Articularis genu is absent

The fascia covering the hind limb is the superficial and deep fascia. The superficial fascia is very scanty lies beneath the skin. It has the same general disposition as in other regions of the body. The deep fascia is in the form of a thick strong sheet covering the superficial layer of muscles over the medial aspect of the hind limb. From this sheet extend several septa that pass between different muscles or muscle groups in the thigh region. The deep fascia of the leg region continues cranially with the fascia of the thoracolumbar region. Caudally it is attached to the aponeurotic tendon of insertion of sartorius and gracilis muscles. The part of the deep fascia that continues on the lateral aspect of the thigh is the fascia lata which is continuous with the gluteal fascia dorsally.

The muscles of the hind limb (Fig. 6-3 A and B) are arranged into different regional, positional as well as functional groups. The muscles of hip and thigh region are arranged in the lateral, medial and cranial groups. The muscles of leg and foot are arranged in dorsolateral and plantar groups. The dorsolateral muscles are generally the extensors of tarsus and digits while the plantar muscles are the flexors of tarsus and digits.

Horse

The hip joint has an additional ligament called the pubio-femoral ligament. It arises from the prepubic tendon, passes dorsally and laterally and then caudally and lodges into the subpubic (pubio-femoral) groove, penetrates the capsular ligament, passes through the acetabular notch and is inserted into the fovea capitis behind the round ligament on the head of femur. This ligament is peculiar to solipeds and it prevents the side kicking. The absence of this ligament in ruminants allows them abduction freely and that is how the ruminants can kick sideways. As against this, the equines can kick only back way. The other difference about the hip joint in horse is that the cotyloid ligament is narrower because of the deeper acetabulum.

The stifle joint of horse in general resembles that of ox except that the middle patellar ligament is not so prominent as that in ox.

The tibio-fibular articulation in horse is a diarthrosis and an amphiarthrosis. The diarthrosis is formed between the lateral condyle of tibia and the head of the fibula. It has intimate capsular ligament. The amphiarthrosis is formed between the shafts of the tibia and the fibula. The shafts of the two bones are binded by the proximal and distal interosseous ligaments.

The hock joint of horse has minor differences with those of ox owing to the difference in the number of tarsal bones and their arrangement. The synovial membrane is supported everywhere except at the dorsomedial (craniomedial) aspect where it bulges out in the cases of bog-spavin. If there is a distension of tarsal sheath, it bulges out as two rounded swellings on either sides of the tendon of deep digital flexor. The movements at the hock joint are very limited.

The articulations of hind limb (pelvic limb) comprises the joints of pelvic region which include the sacro-iliac articulation, pelvic symphysis and the hip joint; the articulation of thigh region named as stifle joint; the articulation of tarsal or hock joint and the articulations of digits which include the metatarso-phalangeal joint (fetlock) joint, the proximal interphalangeal joint (pastern joint) and the distal interphalangeal joint (coffin joint). The joints of pelvic region especially the sacro-iliac joint and the pelvic symphysis have been described with the articulations of abdomen and pelvis.

Horse

The femur of horse is more massive than that in ox. The proximal third of the caudal surface of shaft of femur presents a rough eminence for attachment of biceps femoris muscle. The trochanter minor is a rough ridge like structure. The proximal third of the lateral border of shaft presents trochanter tertius for attachment of superficial gluteus muscle. The trochanter major is comprised of a convexity, a summit and a crest. The trochanteric ridge is vertical and it connects the trochanter major with the third trochanter. The lateral supracondyloid crest and the supracondyloid fossa are better developed in horse than that in ox. The patella of horse is wider and longer than that of ox.

The tibia in horse is relatively longer than that in ox. The popliteal line is prominent. It extends from the proximal third of the medial border, obliquely crosses the caudal surface and ends at the middle of the lateral border of the shaft of tibia. The medial border in its proximal third bears a small popliteal tubercle for attachment of popliteus muscle. The lateral border is attached to the shaft of the fibula and encloses an interosseous tibiofibular arch with the fibula. At the proximal extremity, the cranial tuberosity is vertically grooved. The lateral condyle on its lateral side presents facet for articulation with the proximal extremity of fibula. At the distal extremity, the grooves are oblique. The lateral malleolus is fused with the distal extremity of tibia, The medial malleolus is more prominent than the lateral one.

The hind limb (Fig. 6-1) is termed as pelvic limb and it consists of four segments-the pelvic or hip region, thigh, leg and the pes region. The skeleton of pelvic region is formed by the pelvic girdle (os coxae). The skeleton of thigh region is mainly formed by a long bone (thigh bone) the femur and at its lower extremity is a short sesamoid bone, the patella. The leg region is formed by two long bones, the larger one the tibia and the smaller one the fibula. The last segment, the pes has three subdivisions as tarsus, metatarsus and digits. The tarsus has five short bones arranged in two rows on par with the carpus of fore limb. The metatarsus is constituted by two bones of which one is a long bone called the large metatarsal and the other a short small rudimentary bone the small metatarsal bone. The last part of the hind limb is the digits which are constituted by six phalanges and six sesamoids like those of the forelimb.

Site for nerve block

Brachial plexus block

The brachial plexus is the key source of nerve supply to the fore limb. Loss of sensation below the elbow is achieved by blocking the nerve roots contributing to this plexus. In ox it is formed by the ventral branches of 6th to 8th cervical and 1st and 2nd thoracic spinal nerves. These nerve roots pass over the lateral aspect of the middle third of the first rib before anastomosing to form the plexus. All these nerve roots can be blocked by injecting anaesthetic solution on these nerves at the middle third of the lateral surface of the first rib. To reach this site, the needle is inserted between the thoracic wall and the medial face of the shoulder at the level of acromion process of the scapula about 12 to 14 cm cranial to it horizontally in the caudal direction.

The blocking of brachial plexus is indicated for operations for reducing the fractures of the bones of fore arm and manus.

Horse

The brachial plexus in horse is formed by ventral branches of the last three thoracic and first two thoracic spinal nerves similar to that in ox. The disposition and distribution of nerve branches extending from the plexus is almost similar to that of the ox except the following two.

The radial nerve after reaching the musculospiral groove gives out a cutaneous branch that passes through the lateral head of triceps and is distributed to the skin on the lateral aspect of forearm.

The main trunk of the radial nerve after crossing the carpus descends along the medial aspect of the palmer surface of metacarpus as palmer medial metacarpal nerve and further down on the medial digit as palmer medial digital nerve.

The ulnar nerve descends the carpus and after reaching the metacarpal region joins the lateral branch of the median nerve, descends first along the lateral aspect of the palmer surface of metacarpus as palmer lateral metacarpal nerve and then along the lateral (abaxial) aspect of the lateral digit as palmer lateral digital nerve.

Brachial plexus (FIG. 5-5 A)

The fore limb is supplied by nerves that extend from the brachial plexus. The brachial plexus is a large wide, flat and thick fascicular anastomosis of nerves formed by the convergence of ventral branches of last three cervical and first two thoracic spinal nerves in ox. It is placed between the scalenus muscle on the lateral wall of thorax and subscapularis and deep pectoral muscles on the costal (medial) surface of the scapula. From this plexus extend the following eleven branches (nerves) which are distributed mainly to the fore limb (thoracic limb) and most of the muscles of the thoracic girdle.

Horse

The arteries of fore limb of horse are more or less similar in their course and distribution. However, there are some special features in respect of some of these arteries as described below.

The brachial artery descends vertically on the medial aspect of humerus to its distal extremity, crosses it obliquely and descends along the joint capsule and medial lateral ligament of elbow joint, gives off common interosseous artery at the proximal third of the forearm and then continues distally as median artery.

The median artery descends along the caudomedial aspect of the radius covered by flexor carpi radialis muscle and divides just proximal to medial condyle into radial and collateral ulnar (ulnar) arteries.

The collateral ulnar artery is smaller of the two terminal branches of median artery. It descends along the cranial surface of radius under cover of the extensor carpi radialis and terminates a little above the carpus by anastomosing with a branch of radial artery.

The lymph from the fore limb is collected and carried into the circulation through two main lymph nodes, the prescapular and the axillary lymph nodes. There may be two more lymph nodes in fore limb but those are inconsistent and only occasionally found in ox. These include the accessory axillary lymph node and infraspinous lymph nodes and their afferents are mostly from the thoracic wall.

The venous drainage of the fore limb of ox is conducted by two independent routes, the superficial and deep routes, in the fore limb. The major vein of the superficial route is the cephalic vein and that of the deep route is the axillary vein. The venous drainage of the fore limb begins at the digits and is carried by branches of both the routes intermingling or confluent with each other up to the level of elbow joint. From the elbow upwards the journey of the two paths is completely independent of each other. The superficial veins join the cephalic vein while the deep veins join the axillary vein to open into the cranial vena cava.

Superficial veins

The superficial veins begin in the form of distal deep and distal superficial palmer arch just above the fetlock joint. These venous arches are formed by the union of axial and abaxial digital veins. From these venous arches extend the dorsal metacarpal vein ascending first through the interdigital space and then winding around the large metacarpal bone. In this course it anastomoses with the branches of radial vein on the dorsomedial aspect of the carpometacarpal region and passes further upward as accessory cephalic vein.

Subclavian artery

The fore limb is chiefly supplied by the subclavian artery (Fig. 5-4 A). It originates from the brachiocephalic trunk within the thoracic cavity. The left subclavian detaches from the brachiocephalic trunk opposite the second rib, passes craniodorsally towards the thoracic inlet winds around the cranial border of the first rib and then courses caudoventrally through the axillary space between the subscapular and teres major muscles as the axillary artery. It gives off the subscapular branch and continues as the brachial artery. The right subclavian is the direct continuation of the brachiocephalic trunk after the later gives off the bicarotid trunk opposite the first rib. It gets exit through the thoracic inlet, winds around the cranial border of the first rib and then continues as the right axillary artery and thereafter as the brachial artery similar to the artery of the left side.

Horse

The muscles of shoulder region namely the supraspinatus, infraspinatus, teres major, teres minor and coracobrachialis in horse resemble those of ox. The subscapularis muscle has only a single head of origin in horse as against three heads in ox. The deltoideus muscle has two parts of origin as that of ox but in horse its acromial part is named as cranial part and it arises from scapular spine and the scapular fascia instead of the acromion process. In addition to these muscles, the shoulder in horse is composed of one more muscle named as capsularis. The capsularis is a very fine narrow muscle arising from the caudal part of the rim of the glenoid cavity of scapula and is inserted on the caudal part of the neck below the head of the humerus by insinuating itself between the fibres of brachialis muscle. This muscle is peculiar to solipeds and it raises the capsular ligament of shoulder joint during flexion of the joint.

The muscles of arm in horse are in general similar to those of ox except the following minor differences. The tendon of origin of biceps brachii is adapted to the intertuberal (bisipital) groove. The tensor fasciae antibrachii is thin in front and wide below. The medial head of triceps brachii is less developed and extends from the middle of the medial surface of shaft of humerus. The anconeus is smaller and less voluminous.

Amongst the muscles of forearm and manus, the flexors of carpus especially the flexor carpi radialis, flexor carpi ulnaris and the ulnaris lateralis resemble those of ox. The pronator teres is either vestigial or completely absent. The medial digital extensor is absent. The extensor carpi radialis resembles that of ox. The common digital extensor arises in common with the extensor carpi radialis. Its tendon descends over the synovial capsule of the carpus, passes down the metacarpus and at the fetlock it receives two slips from suspensory ligament to form the broad ligament which is inserted to the pyramidal extensor process of the distal phalanx. The lateral digital extensor is smaller. It arises from humerus and radius. Its tendon is inserted to the prominence on the dorsal (cranial) aspect of the proximal extremity of the proximal phalanx. The extensor carpi obliquus is inserted to the head of the medial small metacarpal bone. The superficial digital flexor does not divide into two parts. Its tendon is reinforced above the carpus by a strong fibrous band- the superior check ligament. The ring for the deep digital flexor is formed entirely by the tendon of superficial digital flexor. The deep digital flexor has same heads of origin as those of ox. Its tendon receives about half way down the metacarpus the inferior check ligament. It is inserted to the semilunar crest and tendinous surface of the distal phalanx.

The muscles of fore limb (Fig. 5-3 A and B) are distributed in different regions of fore limb as muscles of shoulder girdle, shoulder, arm and those of forearm and manus. By means of the muscles of shoulder girdle the forelimb is attached with the trunk of the body by synsarcosis and bears the weight of the body. The rest of the groups of muscles act on different joints of the fore limb as extensors or flexors of these joints. The group of muscles acting on these joints originates on the bone of the proximal segment and insert on the bone of distal segment of the concerned joint.

Muscles of shoulder girdle

The muscles of shoulder girdle have been described with the muscles of thorax.

Muscles of shoulder

The muscles of shoulder arise on the scapula, act on shoulder joint and end on the humerus. These muscles are in two groups as the lateral group of muscles and the medial group of muscles.

Horse

The shoulder joint of horse has same features as those of ox. However, this joint in horse exhibits greater degree of mobility.

The elbow joint of horse is almost similar to that of ox except that there is only one interosseous ligament in horse against two in ox.

The carpal joint of horse has only minor differences from that of ox. The special feature of the joint in horse is that it has two additional ligaments, the superior check ligament and the inferior check ligament. The superior check ligament starts from the rough elevation on the distal third of the caudal surface, close to the medial border of the radius and is inserted to the tendon of superficial digital flexor above the carpus. The inferior check ligament is the continuation of the caudal (palmer) capsular ligament of the carpus. It joins the tendon of deep digital flexor at about midway on the palmer surface of the metacarpus. The check ligaments assist the tendons of flexor muscles of the digits after severe exertion to keep then tight and prevent flexion.

Shoulder joint

The shoulder joint (Fig. 5-2 A) is an enarthrosis formed between the glenoid cavity of scapula and head of humerus.

Ligaments: The shoulder joint is enclosed by the capsular ligament which is loose enough to accommodate the wide range of movements of the joint and is attached about 1.25 cm away from the periarticular area of the two segments of the joint. The capsular ligament is supported externally by the muscles of the shoulder region.

Movements: The shoulder joint performs all kinds of movements but the extension and flexion are best marked.

Horse

The scapula of horse is a flat triangular bone placed at the shoulder region applied against the cranial part of the lateral wall of thorax similar to that in ox. The scapular spine is placed a little further caudad from the cranial border so that the proportion of the area of supraspinous to infraspinous fossa is one third to two third of the lateral surface of the scapula. The subscapular fossa is deeper and presents well marked vascular impressions. The nutrient foramen is placed at the distal third of the infraspinous fossa. The tuber scapulae and the glenoid cavity are placed further apart. The glenoid cavity is oval in outline and its rim has a distinct notch on its craniomedial aspect. The coronoid process is better developed and the acromion process is absent.

The humerus in horse is directed obliquely distally and caudally forming an angle of about 55 degrees with the horizontal plane almost equaling to that in ox. The musculospiral groove on the shaft is deeper and more spirally curved. The nutrient foramen is placed on the distal third of the medial surface. The deltoid tuberosity is better developed. The medial and lateral tuberosities of the proximal extremity are more prominent. The intertuberal (bisipital) groove is divided by an intermediate ridge. The summit of the lateral tuberosity does not arch inward. The head is smaller than that in ox. The coronoid and olecranon fossae of the distal extremity are shallower than those in ox.

The radius of the horse is larger and longer of the two bones of the forearm. Close to the medial border of the caudal surface in the lower third of the shaft is a rough elevation for attachment of the superior check ligament (an accessory ligament of the superficial digital flexor). The caudal surface of the shaft towards its lateral border presents a rough triangular area which tapers to a point in the distal third of this surface. This is for attachment of the ulna. The distal interosseous space is absent because the shaft of ulna is shorter and does not reach to the distal part of the shaft of radius. The grooves on the cranial surface of the distal part of the shaft are better marked. The radial tuberosity at the craniomedial aspect of the proximal extremity is larger and more prominent than in ox. The distal articular surfaces are not oblique. It presents two tubercles one on each side, for ligamentous attachment. The tubercle on the lateral aspect is grooved for passage of tendon of lateral digital extensor.

The fore limb is termed as pectoral limb or thoracic limb (Fig. 5-1). It is attached to the thorax by means of muscles of pectoral girdle (shoulder girdle). It is composed of four major segments, the shoulder girdle, arm, forearm and manus. The skeleton of shoulder girdle is formed by the shoulder bone, the scapula. The arm is formed by the arm bone the humerus. The forearm is formed by two bones the radius and ulna; and the manus is formed by the carpus consisting of six short bones –the carpal bones arranged in two layers, the metacarpus consisting of one large and one small metacarpal bones and the digits consisting of six short bones the phalanges and six small sesamoids arranged in two rows for each limb.

Shoulder girdle

The shoulder girdle (thoracic girdle or pectoral girdle) in general is composed of the scapula, coracoid and clavicle. In ruminants the scapula is well developed, the coracoid is in the form of a small rounded process fused with the ventral end of the scapula and the clavicle is absent or in some subjects it occurs embedded in the brachiocephalicus muscle cranial to the point of the shoulder. But this possibility is very rare. Hence, in ox only scapula is considered as the bone of shoulder girdle.

Scapula

The scapula is a flat triangular bone applied obliquely ventrad and craniad against the cranial part of the lateral wall of thorax. Its long axis extends from the fourth thoracic spine to the sternal end of the first rib. It presents two surfaces, three borders and three angles.

Surface anatomy of the organs of left side of abdominal cavity

Rumen

Topography of the rumen: The left side of the abdomen in cow is completely occupied by the rumen except for a small area occupied by the reticulum at its cranial end and the spleen on the craniodorsal aspect sandwiched between the dorsal border of rumen and the diaphragm. The rumen lies in contact with the left abdominal wall extending from seventh or eight intercostal space where it touches the diaphragm to the transverse plane of the tuber coxae where it almost touches the pelvic inlet.

Palpation of rumen: The rumen can be palpated in the left flank of the abdomen and is usually palpated in the dorsal third of the flank region. In ruminants, the contraction begins at reticulum and it continues in rumen in succession and hence is considered as ruminoreticular contraction cycle. It begins with double contraction of reticulum followed immediately by the contraction of rumen. The rumen contraction begins in the cranial sac and progresses to the dorsal sac and then to the ventral sac. During the contraction of the ventral sac, the dorsal sac is forced out which appears as a bulging at the paralumbar fossa. After this, there is a pause of 30 seconds and thereafter the second ruminal contraction begins which is usually associated with eructation. The ruminoreticular contraction cycle ends with the end of second ruminal contraction. Following this, the second cycle begins. Thus there are two palpable rumen contractions per minute. This rate of contraction increases to 2.8 contractions per minute during the act of feeding of the animal.

Horse

There are six pairs of lumbar, five pairs of sacral and five pairs of coccygeal spinal nerves in horse. Their origin, course and distribution is in general similar to those in ox.

The number of sympathetic lumbar and coccygeal ganglia is just the same in horse as that of ox. However, the number of sacral sympathetic ganglia is four in horse as against five ganglia of ox.

The greater (major) splanchnic nerve in horse is formed by the fibres received from sixth or seventh to fourteenth or fifteenth thoracic sympathetic ganglia. It is smaller in its cranial thoracic part but as it proceeds caudally it gradually increases in size so much that it becomes larger than the thoracic sympathetic trunk in the caudal thoracic part. It receives a communicating branch from the lesser splanchnic nerve before terminating in the coeliacomesenteric ganglion.

The lesser (minor) splanchnic nerve is formed by fibres received from the last three or four thoracic and the first two lumbar sympathetic ganglia. It communicates with the greater splanchnic nerve and the renal and adrenal plexuses and terminates in the coeliac plexus and ganglion.

The rest of the features of spinal nerves and autonomic plexuses of the abdomen and pelvis in horse are almost similar to those of ox except those related to the distribution of fibres to the parts of ruminant versus simple stomach.

Abdominal part

The sympathetic trunks enter the abdominal cavity between the psoas minor and the crus of the diaphragm of the corresponding side. They run caudally on the ventrolateral surfaces of the lumbar vertebrae and the ventral common vertebral ligament. The left trunk is ventrally related to the abdominal aorta and the right trunk to the caudal vena cava. The sympathetic trunks of the opposite sides in the cranial half of the lumbar part lie rather close to each other and as they pass caudally, they gradually divert from each other. The lumbar sympathetic ganglia are small spindle shaped usually six in number and are present one in each lumbar segment. The first two are larger than the rests. Each is connected with the ventral division of the corresponding lumbar spinal nerve by the ramus communicans. The interganglionic segments of the sympathetic trunk are usually single but some times they split.

Splanchnic nerves

The greater (major) splanchnic nerve is formed by the contribution of sympathetic nerve fibres from fifth or sixth thoracic to thirteenth thoracic sympathetic ganglia. It becomes larger and larger as it passes caudally along with the sympathetic trunk. It enters the abdomen at the level of the first lumbar vertebra gets separated from it, passes ventrally and laterally across the aorta (left trunk) and vena cava (right trunk) to join the coeliacomesenteric autonomic plexus on and around the coeliac and cranial mesenteric arteries.

Lumbar nerves

There are six pairs of lumbar spinal nerves. Each of these, after emerging out of the intervertebral foramen, gives out firstly a meningeal branch which reenters the vertebral canal through the intervertebral foramen and supplies the meninges. Next to this it furnishes the ramus communicans to the sympathetic chain ganglion. After this, the lumbar spinal nerves divide into dorsal and ventral branches. The dorsal branches are smaller and they supply the muscles and skin on the loins and croup. The ventral branches are larger and they slightly differ from each other in their course and distribution. In their initial course, they pass under the psoas minor and psoas major muscles emerge at the lateral border of the psoas major and supply branches to the sublumbar muscles. Hereafter, they differ in their course and distribution.

The ventral branch of the first lumbar nerve passes on the medial face of the quadratus lumborum, runs down the medial face of the transversus abdominis, the obliquus abdominis internus and externus and finally reaches the rectus abdominis, supply all these muscles and the skin on the lateral wall and the floor of the abdomen.

The ventral branch of the second lumbar nerve has two divisions. The cranial division passes ventrally and caudally to reach the external angle of the ilium, supplies branches to the oblique muscles of the abdomen and the skin over this region and terminates in the rectus abdominis muscle. The caudal division passes caudally and laterally under the quadratus lumborum, supplies branches to the muscles and skin at the flank region and then crosses the circumflex iliac vessels. Here it joins a similar branch of the third lumbar nerve and forms the genitofemoral nerve.

Horse

Lymph nodes of the wall of abdomen and pelvis

The lumbar aortic lymph nodes extend from kidneys to the deep circumflex iliac vessels. These are not clearly distinguishable from the cranial and caudal mesenteric, renal, testicular or ovarian, uterine and iliac lymph nodes.

The internal iliac lymph nodes are placed at about the origin of the iliac arteries. The external iliac lymph nodes are several small nodes situated in the triangular space between the cranial and caudal branches of the circumflex iliac artery.

The deep (internal) inguinal lymph node is not abdominal in position. It is not situated at the pelvic brim. It is one of the group of the lymph nodes of the hind limb.

The superficial (external) inguinal lymph nodes are on either side of the penis and in front of the superficial inguinal ring in male and above the mammary glands as the supramammary lymph nodes in female.

The prefemoral lymph nodes are about a dozen small glands arranged in an elongated mass placed on the medial aspect of the cranial border of tensor fasciae lata and on the caudal branch of circumflex iliac artery.

The lymph nodes of the abdomen and pelvis are in two major divisions, lymph nodes of the wall of the abdomen and pelvis and those of the viscera of abdomen and pelvis. The lymph from all the lymph nodes is collected by different lymph ducts which carry and pour their contents (lymph) in the cisterna chyli near the hiatus aorticus on the abdominal surface of the diaphragm.

Lymph nodes of the wall of abdomen and pelvis

The lumbar aortic lymph nodes are a chain of small lymph nodes situated along the caudal part of the abdominal aorta. These lymph nodes receive afferents from the peritoneum, sublumbar, spinal and abdominal muscles and the lumbar vertebrae. The efferents from these lymph nodes join each other and form two lumbar trunks which later on unite in a single lumbar lymphatic trunk that opens into the cisterna chyli.

The medial iliac lymph nodes are situated near the origins of the deep circumflex iliac and the internal external iliac arteries. The afferents for these lymph nodes are received from the internal iliac, tuberal, gluteal coxal, lateral iliac, subiliac, superficial inguinal and popliteal lymph nodes. The efferents from these lymph nodes either form a lumbar trunk or join any of the lumbar aortic lymph nodes.

Horse

The caudal vena cava in horse is largely embedded in the substance of the liver on its diaphragmatic surface. Here its free surface is covered only by the peritoneum. After crossing the liver, the caudal vena cava continues caudally along the right side of the abdominal aorta. During its course it gives off several branches from the dorsal and lateral surface.

The lumbar veins (parietal) are five or six pairs in number. The last one or two of these often join the internal iliac veins.

The renal veins are thin walled. The right renal vein is shorter than the left one.

The phrenic veins are two or three in number. The circumflex iliac veins join either the caudal vena cava or the internal iliac vein.

The portal vein is formed by the union of cranial and caudal mesenteric and the splenic veins in the cranial part of the sublumbar region at about the level of second lumbar vertebra. It passes cranially and to the right of the median plane continues through the portal ring of the pancreas and reaches to the portal fissure of the liver. Before entering the portal ring of the pancreas, the portal vein receives right gastroepiploic vein, right gastric vein and cranial pancreaticoduodenal vein. The cranial mesenteric, caudal mesenteric and the splenic veins are formed by the tributaries from the veins which are satellites of the branches of the respective arteries. After its entry into the hepatic portal, the portal vein divides into three principal branches. These include the right branch for right lobe, the middle branch also for the right lobe and the left branch for the left and the quadrate lobe.

The caudal vena cava is a large unpaired vein which receives blood from the pelvis, pelvic limbs, mammary glands (in females) and scrotum (in males), the abdominal walls, and the viscera of the abdomen and pelvis. It is formed under the body of the fifth or sixth lumbar vertebra by the union of two common iliac veins which in their turn are formed by the union of the internal iliac and external iliac veins of the corresponding side. It passes cranially in the sublumbar region lying slightly to the right of the median plane and to the right of the abdominal aorta. In the cranial part of the abdomen, it follows the abdominal surface of the diaphragm and is embedded in the liver prior to its entry into the thorax through the foramen vena cava in the diaphragm.

In its abdominal course, the caudal vena cava is related dorsally to the sublumbar muscles and right crus of the diaphragm, ventrally to the colon, pancreas and the liver, on its right to the right kidney and the right adrenal and on its left to the abdominal part of the aorta.

Tributaries of caudal vena cava

The common iliac veins are short vessels formed by the union of the internal and the external iliac veins. These are located at the level of the fifth or sixth lumbar vertebra. The left vein crosses the dorsal surface of the aorta to reach the vena cava.