Effects of undegraded intake protein supplementation on milk production, calf weight gain and reproductive performance in Brahman cows

Abstract

Eighty multiparous and 51 primiparous Brahman females were allotted to one of three diets based on; parity, sex of calf and breed of calf sire (Angus, Brahman or Tuli). Diets contained either 38.1% Undegraded Intake Protein (UIP) (Low), 56.3% UIP (Medium), or 75.6% UIP (High). Cows received UIP supplements from days 7 to 119 after calving. Cow and calf BW and cow body condition score were recorded on days 7, 35, 63, 91 and 119 after calving. Four hour milk production was recorded on the above days for 18 Low, 19 Medium and 18 High treatment animals, and on days 7 and 35 for the entire group. Blood was sampled weekly for progesterone, blood urea nitrogen and glucose. Additional blood samples were drawn for progesterone analysis on days 6, 8, 10 and 12 after an observed estrus. Mean milk production was greater for mature cows (1.27 .03 kg/4h) than for heifers (1.06 .︢04 kg/4h) (P <.Ol). Medium heifers produced more (Treatment x Parity, P <.02) milk (1.18 .07 kg/4h) than Low (1.06 .︢08 kg/4h) or High heifers (.94 .︢07 kg/4h), but milk production in mature cows was not influenced by diet. Medium calves tended (P <.08) to have higher ADG from birth to weaning (.96 .︢02 kg) than Low (.92 .︢02 kg) or High (.89 .︢02 kg) calves. Low animals had lower (P <.04) first service conception rates (2 9.17%) than Medium animals (5 7.5 8%) and tended to have lower first service conception rates than High animals (54.55%). The Low group had more animals (P <.05) which failed to return to estrus during the breeding season (3 5.14%) than the Medium or High treatment groups (1 5.3 8%). Overall pregnancy rates did not differ (P > . 1 0) among the three treatments, but trended to be higher in the Medium (61.54%) and High (56.41%) treatment groups than in the Low treatment (43.24%) group. Supplementing UIP at the Medium rate improved milk production in heifers, trended to improve pregnancy rates and improved first service conception rates.