(a) Enlist the major sources of Vitamin A and its deficiency symptoms in newborn calves, lambs and piglets. What are the factors…

(a) Vitamin A: sources, deficiency in newborn calves, lambs and piglets, and factors interfering with its use (20 marks)

Major sources:

1. Preformed vitamin A (retinol and its esters): fish liver oils, animal liver, egg yolk, milk and butter, and especially colostrum, which is the main source for newborn calves, lambs and piglets, since little crosses the placenta.
2. Provitamin A carotenoids, chiefly β-carotene, which the intestinal wall converts to retinol: fresh green fodder and pasture, lucerne, good-quality green hay and silage, carrots, yellow maize, and palm and other coloured plant oils. Bleached or old fodder has lost its carotene, and white maize has almost none.
3. Vitamin A premixes and supplements.

Deficiency symptoms:

• Newborn calves: night blindness, then blindness (xerophthalmia and corneal opacity), poor growth, weakness, diarrhoea, pneumonia, convulsions and, in the dam's deficiency, weak or dead calves.
• Lambs: night blindness, poor growth, weak or stillborn lambs, and susceptibility to infection.
• Piglets: eye defects and blindness, poor growth, incoordination, and hind-leg paralysis, with diarrhoea and respiratory infections; sows may abort or produce malformed piglets (small eyes, cleft palate).

The common cause is the failure of epithelia (keratinisation of the eye, respiratory and gut linings), together with impaired vision, immunity and bone remodelling.

Factors interfering with vitamin A utilisation:

• Poor conversion of carotene, and low conversion in some species (cattle convert poorly, and cats do not); thyroid deficiency also reduces it.
• Destruction of carotene and vitamin A by oxidation, heat, light and long storage of feeds, and by rancid fat; lack of vitamin E and other antioxidants.
• High dietary nitrate and nitrite, which inhibit conversion and destroy carotene.
• Poor absorption: low dietary fat, bile or pancreatic disease, diarrhoea and intestinal parasites.
• Protein and zinc deficiency, which reduce retinol-binding protein and transport from the liver.
• Liver disease, infections and stress.

(b) Digestive system of the fowl with diagram; functional anatomy of the crop and gizzard (20 marks)

The digestive tract of the fowl is short and adapted to rapid processing of food. Parts in order:

1. Beak and mouth: there are no teeth, lips or soft palate. The tongue is pointed, and the saliva is scant with mucus and amylase, so food is swallowed quickly.
2. Pharynx and oesophagus, a distensible tube that enlarges into the crop.
3. Crop (ingluvies): an outpouching of the oesophagus at the thoracic inlet.
4. Proventriculus (glandular stomach).
5. Gizzard (ventriculus, muscular stomach).
6. Small intestine: duodenum (in a loop enclosing the pancreas), jejunum and ileum (with Meckel's diverticulum). The bile and pancreatic ducts open in the distal duodenum.
7. Two caeca at the junction of the ileum and rectum.
8. Short rectum (colon), and the cloaca, which is divided into the coprodeum, urodeum and proctodeum and opens at the vent.

Accessory organs are the liver (two lobes, with a gall bladder in the fowl) and the three-lobed pancreas.

Crop: the crop is a thin-walled, distensible sac, lined by stratified squamous epithelium with mucous glands, that lies on the right of the base of the neck. Its function is to store feed while the gizzard is full or when the bird eats fast; to moisten and soften the feed with mucus and water; to begin digestion by salivary and feed enzymes and by lactic acid bacteria; and to regulate the passage of feed to the stomach by contractions. In pigeons the crop makes "crop milk" under prolactin.

Gizzard: the gizzard is a rounded, flattened, powerful muscular organ, with two pairs of strong muscles (thick lateral and thin intermediate). Its inner surface is lined by koilin, a hard keratin-like layer, which is continually worn and renewed, and which protects the wall from acid and grit. The proventricular opening and the duodenal opening lie close together. Its functions are: grinding and crushing feed (in place of teeth), helped by grit (small stones) in the lumen; mixing feed with the hydrochloric acid and pepsin from the proventriculus, so that gastric digestion takes place there (pH about 2 to 3); and regulating the passage of feed to the duodenum. Reverse movements return material from the duodenum to the gizzard. Whole grain and fibre enlarge the gizzard, and finely ground feed reduces it.

(c) Requirements for establishing an animal health centre in a rural area (10 marks)

• Need assessment and site: the livestock population, the disease burden and the distance from existing facilities. The centre should be on a central, road-accessible site in a cluster of villages, with water and electricity.
• Building and space: a consultation and examination room, a treatment and minor surgery room, a pharmacy and drug store, a room for artificial insemination, a laboratory corner, an office and records, a farmer waiting area, and a crush or restraint area for animals, with a separate isolation pen.
• Equipment: a surgical set, stethoscope, thermometers, microscope, autoclave or sterilizer, an insemination gun and liquid nitrogen container, a refrigerator and cold chain for vaccines, a generator or solar power, and a weighing device.
• Medicines and vaccines: an essential list of drugs, dewormers, vaccines and mineral mixtures, with a cold chain and regular supply.
• Staff: a veterinary officer, a livestock inspector or para-veterinarian, and an attendant, with training.
• Services: treatment, vaccination, deworming, artificial insemination, castration, disease surveillance and reporting, extension and health camps, and referral to a polyclinic, a diagnostic laboratory and a district hospital.
• Funds, management and linkages: government schemes, panchayat, cooperatives and user charges for sustainability; community participation; and registration of the veterinary staff and proper disposal of biomedical waste.