PSVI-22 Effects of supplementation of beef cows during gestation on progeny backgrounding frame size and performance

Abstract The implications of supplementation during gestation on growth and efficiency of offspring have gained interest worldwide. The hypothesis of this study was that supplementation of cows during gestation results in favorable progeny growth and nutrient utilization. Our objectives were to assess the impacts of providing supplementation to pregnant beef cows during the dry grazing period on progeny backgrounding performance. During a 2-yr period, Tabapuã cows (n = 36) were managed on Brachiaria pastures, which were assigned to 1 of 3 treatments as follows: no application of N on pasture and cows supplemented with mineral mix (CON), application of 165 kg of Nּ ha-1ּ yr-1 and cows supplemented with a commercial product containing 40% of CP, macro and micro minerals, and vitamins (SUP), and application of 165 kg of Nּ ha-1ּ yr-1 and cows supplemented with grass silage (GS). At the beginning of the dry period, the commercial supplement and silage were fed for 140 d (from 116 ± 27 to 256 ± 27 d of gestation). The mineral mix was offered all year round. Bull (n = 18 in yr 1 and 12 in yr 2) and heifer progeny (n = 13 in yr 1 and 17 in yr 2) were weaned with average age of 203 ± 18 d in yr 1 and 229 ± 15 d in yr 2. After weaning, progeny were weighed and allocated in individual pens and adapted to a growing diet over 90 in yr 1 and 89 d in yr 2. For both years, rations were formulated to provide 0.9 kg/d (Dietary NEm = 1.68 Mcal/kg and dietary Neg = 1.07 Mcal/kg, on average). The PROC MIXED procedure of SAS was used to analyze all variables. The statistical model included supplementation program as a fixed effect and sex (male or female) as a random variable. Initial BW, weaning age, estimated progeny difference, and d on feed were included as covariates. No differences were obtained for initial BW, final BW, ADG, DM intake, and G:F. Frame size (e.g., heart girth, hip height) was also unaffected by dam supplementation. Overall, supplementing pregnant beef cows, during the dry grazing period, with a commercial supplement or silage does not affect progeny performance during backgrounding.