Effect of nutrient intake during gestation on estrus of beef cows and postnatal growth and development of calves

Abstract

Scope and Method of Study: Effects of treatment of anestrous beef cows with estradiol cypionate at 25 of 50 d after calving on onset of estrus and luteal activity was evaluated in cows that calved with a BCS < 5 or ? 5. Effects of nutrient restriction from d 32 to 115 of gestation on the growth, carcass characteristics, and organ composition of calves were evaluated over 2 yr. Heifers (15 mo of age) were AI to a common sire, confirmed pregnant with transrectal ultrasonography stratified by BW and BCS and allotted to either low (L; 56 % of NRC recommended NEm) or moderate (M; fed in excess of NRC requirements) nutritional treatment. Birth weight, weaning weight and postweaning growth of calves were recorded. Feedlot growth, carcass composition and organ composition were determined for L and M steers in yr 1. In yr 2 plasma glucose regulation was evaluated using intravenous glucose tolerance test and also response to intravenous injection of bovine insulin.

Findings and Conclusions: Treatment of suckled postpartum anestrous beef cows with estradiol at either 25 or 50 d postpartum increased the percentage of cows in estrus, however, the percentage of cows with luteal activity by 10 d after treatment was not influenced. Cows that calved with a greater BCS have a shorter period from calving to resumption of normal luteal activity. Treatment of anestrous beef cows with estradiol cypionate increased the days from parturition to normal luteal activity. Maternal nutrient restriction from d 32 to 115 of gestation decreased maternal BW and BCS of heifers. Gestation length was reduced in yr 1 but was not effected by nutritional treatment in yr 2. Weaning weights, postweaning weights, and ADG were not influenced by prenatal nutritional treatment. Lungs and trachea of L steers were lighter then the lungs and trachea of M steers. The complexus muscle from L steers had increased concentration of DNA per gram of muscle, the DNA to protein ratio tended to be reduced and increased muscle fiber area was increased compared with muscle from M steers. Abundance of fatty acid binding protein 4, fatty acid translocase and GLUT 4 mRNA were decreased in kidney pelvic fat of L steers compared with KPH of M steers. Low and M calves responded similar to intravenous glucose tolerance test. Nutrient restriction during early gestation changes muscle development and metabolism of KPH in steers at 22 mo of age.