Last update: November 24, 2010 12:19:25 PM E-mail Print

 

PRELIMINARY RESULTS ON THE INFLUENCE OF VITAMIN A ON THE REPRODUCTION OF

SHEEP AND GOATSIN DIFFERENT PRODUCTION AREAS OF SOUTH AFRICA

 

P G Marais

Grootfontein Agricultural Development Institute, Private Bag X529, Middelburg, Eastern Cape, 5900

 


Since 1922, researchers have known that vitamin A is crucial in the reproductive health of higher animals. Beta-carotene also has a specific role in fertility and reproduction apart from its functions as a precursor to vitamin A. Vitamin A assists in normal pregnancy and lactation possibly by encouraging the activity of specific hormones and assisting in the normal changes in cells characteristic of early growth in the developing fetus. Deficiency of vitamin A may be caused by inadequate dietary intake or by factors that interfere with the absorption, transportation, or storage of vitamin A. Vitamin A deficiency impairs the immune system response, and individuals deficient in vitamin A are more susceptible to infectious diseases and have higher mortality rates. Vitamin A supply to farm animals is more critical than that of any other vitamins. Usually grazing animals such as sheep obtain vitamin A as provitamin, chiefly Beta-carotene, from the consumption of green herbage (McDowell, 1989). Due to the high degree of vitamin A degradation occurring in the rumen, with some diets, it may be desirable to administer vitamin A in certain cases to animals by intramuscular injection. Injectable vitamin A provides economic insurance against marginal or frank vitamin A deficiency in livestock. Up till now no literature concerning the effect of the supplementation of Vitamin A on reproduction could be traced. At the present moment Angora goat farmers in the Eastern Cape inject Vitamin A on the basis of half that of the dosage of cattle per goat. Variable results were obtained, therefore, no definite recommendations are possible. The aim of this study is therefore to investigate the effect of PROVIT A injections on the production and reproduction rate of sheep and goats. This study is currently carried out on 5 farms (2 Boer goats, 2 Dorper, 1 Merino and 2 Angora goat flocks). Between 100 and 200 reproductive ewes will be randomly assigned to one of two experimental groups (Control, Experimental group). Each ewe in the Experimental group will be injected intramuscularly with 0.25 ml of PROVIT A between 4 - 6 weeks before mating. Between 4-6 weeks before birth each ewe in the Experimental group will received a second injection of 0.25 ml. Between 42 - 49 days after mating the total number of ewes in the trial will be scanned to identify pregnancy. The normal farming practices at the respective

experimental sites will be implemented. The following data are collected: conception rate and fecundity, weaning percentage, Iamb mortality rates, body weight of Iambs at 42 days of age and at weaning, body weight of ewes at mating and at 42 day Iamb age. Preliminary results indicate very small or no differences with regard to conception and scanning percentage between the control and experimental group. The high rainfall that occurred in most of the summer rainfall areas during the mating season, with the resulting good grazing conditions, probably contributed to the small differences between the groups. This project will be expand to the more drier areas in the Northern Cape.