Effects of dietary crude proteins on constituents of plasma and uterine secretions were examined at various stages of the estrous cycle of high producing Holstein cows. Eighteen cows were assigned randomly to isocaloric diets (74% total digestible nutrients) containing either 12 or 23% crude protein (dry matter) on day 40 postpartum. Uterine secretion and coccygeal blood samples were collected at estrus, days 5 and 15 of the first estrous cycle after day 50 postpartum, and at the subsequent estrus. The 23% crude protein diet resulted in higher concentrations of ammonia in blood, urea in blood plasma and uterine secretion, and phosphorus and potassium in plasma. Zinc increased during the estrous cycle in plasma of cows fed 23% crude protein and decreased in cows fed 12% crude protein. Magnesium concentrations in uterine secretions were lower in cows on 23% crude protein. Potassium and phosphorus also were lower in uterine secretions of cows fed 23% crude protein but only during the luteal phase of the estrous cycle. Zinc concentrations in uterine secretions decreased faster during the estrous cycle in cows fed 12% crude protein than in cows fed 23% crude protein. Thus, the crude protein content of the diet altered concentrations in blood of ammonia and concentrations in plasma of urea, phosphorus, potassium, and zinc. Crude protein content of the diet altered concentrations in uterine secretion of urea, magnesium, potassium, phosphorus, and zinc.

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The objective of this study was to establish optimal conditions for the primary culture of pig preadipocytes. We cultured pig preadipocytes for 10 d and studied the effects of insulin, hydrocortisone, and triiodothyronine (T3) added to serum-free basal medium on differentiation and gene expression of lipoprotein lipase an early marker, and adipsin, a late marker of preadipocyte differentiation. Insulin alone and hydrocortisone alone stimulated a low level of cell differentiation, as indicated by an increase in glycerol-3-phosphate dehydrogenase activity. When added together, insulin and hydrocortisone had a synergistic effect on cell differentiation. When combined with insulin or hydrocortisone, T3 had no effect on cell differentiation, indicating that T3 is not required in porcine preadipocyte culture. Gene expression studies also showed that removal of insulin or hydrocortisone from complete serum-free medium reduced both early and late marker mRNA. As expected, removal of T3 had no effect on the gene expression of early and late marker mRNA. We conclude that insulin and hydrocortisone, but not T3, are required for the differentiation of pig preadipocytes in primary culture.

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