Abstract
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.
Highlights
Conception and maintenance of pregnancy in mammals involves complex interactions of biochemical, endocrine and immunological factors between the embryo, placenta and mother
LH concentrations are very similar to concentrations that are normally found during dioestrus[10]
Owing to the importance of progesterone production in maintenance of pregnancy, the purpose of this study was to investigate the effect of dietary protein quality on serum progestagen concentrations in both lactating and non-lactating mares during pregnancy
Summary
Conception and maintenance of pregnancy in mammals involves complex interactions of biochemical, endocrine and immunological factors between the embryo, placenta and mother. After fertilisation the embryo is transported through the fallopian tube to the uterine environment where a wide range of proteins and other nutrients are secreted by the endometrial glands to meet the nutritional demands of the embryo before implantation. The cyclical endocrine changes associated with reproduction resume a secretory pattern necessary to maintain pregnancy. Progesterone, play an important role in the maintenance of pregnancy. LH concentrations are very similar to concentrations that are normally found during dioestrus[10]. LH concentrations do not increase in response to rising aDepartment of Human and Animal Physiology, University of Stellenbosch, Private Bag X1, Matieland, 7602 South Africa
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