The effect of dietary protein on reproduction in the mare. VI. Serum progestagen concentrations during pregnancy.
Sixty-four Thoroughbred and Anglo-Arab mares aged 6-12 years were used, of which 40 were non-lactating and 24 lactating. Foals from these 24 mares were weaned at the age of 6 months. Non-lactating and lactating mares were divided into 4 dietary groups each. The total daily protein intake and the protein quality (essential amino-acid content) differed in the 4 groups of non-lactating and 4 groups of lactating mares. The mares were covered and the effect of the quantity and quality of dietary protein on serum progestagen concentrations during pregnancy was studied. A sharp decline in serum progestagen concentrations was recorded in all dietary groups from Days 18 to 40 of pregnancy, with some individual mares reaching values of less than 4 ng/ml. Serum progestagen concentrations recorded in some of the non-lactating mares on the low-quality protein diet increased to higher values (p < 0.05) than those of mares in the other 3 dietary groups at 35-140 days of pregnancy. A similar trend was observed for the lactating mares on a low-quality protein diet at 30-84 days of pregnancy. No such trends were observed in any of the other dietary groups. High-quality protein supplementation increased serum progestagen concentrations during the 1st 30 days of pregnancy. Lactation depressed serum progestagen concentrations until after the foals were weaned.
van Niekerk
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FE
Department of Human and Animal Physiology, University of Stellenbosch, Matieland, South Africa.
van Niekerk
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CH
D000818:Animals; D003627:Data Interpretation, Statistical; D004044:Dietary Proteins / Q000008:administration & dosage* / Q000592:standards*; D005260:Female; D007774:Lactation / Q000097:blood; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000097:blood*; D011372:Progestins / Q000097:blood*; D012098:Reproduction / Q000502:physiology
D004044:Dietary Proteins; D011372:Progestins