Effects of Protein Supplementation on Reproductive Performance of Fall Calving Cows, and Prenatal and Postnatal Growth, and Carcass Characteristics of Calves

Abstract

Fall calving cows were used to determine the effects of protein supplementation on reproduction, and growth and carcass characteristics of calves. Cows were individually supplemented from mid-November to mid-March for four years with either a control diet (Con; 1.82 kg/d of 38 % CP) or low diet (L; 0.2 kg/d of 8% CP). During each year, cows were reassigned dietary treatments according to calving date and BCS, with half of Con and L cows remaining on the same diets as the previous year and the other half assigned to the other diet. Cows were exposed to bulls for 60 d beginning December 1. Statistical analyses were performed with a 2 x 2 factorial design with PROC GLM and PROC FREQ. Cows on Con diets lost less BW from November to January compared with L cows (-29.8 ± 2.8 and -49.7 ± 2.8 kg, P < 0.001). Control cows had greater BCS compared with L cows in May (4.1 ± 0.1 and 3.9 ± 0.1, P = 0.03). Prenatal supplementation did not influence birth weight of calves ( P = 0.86). Concentrations of IGF-I were greater in plasma of calves suckling Con cows compared with calves from L cows (21.4 ± 2.1 and 14.8 ± 2.1ng/ml, respectively; P = 0.03). There was a prenatal x postnatal effect for BW of calves; prenatal Low and postnatal Control (LCon) calves (186.1 ± 4.4, P = 0.02) had greater 205 d adjusted weaning weights compared with prenatal Low and postnatal Low (LL), prenatal Control and postnatal Low (ConL), and prenatal Control and postnatal Control (ConCon) calves (154.9 ± 4.0, 172.4 ± 4.1, and 180.1 ± 4.2 kg, respectively). Calves from cows on Con diets during prenatal and postnatal growth had greater hot carcass weights (393.6 ± 9.1 kg) compared with LL calves (362.6 ± 9.1 kg, P = 0.02), however, other carcass characteristics were not influenced by treatment ( P < 0.17). Feeding supplemental protein that decreased BW loss and increased BCS, increased ADG of calves prior to weaning, increased IGF-I in plasma, and increased BW until harvest, but did not influence carcass characteristics of calves.