U.S. Department of Agriculture: Agricultural Research Service, Lincoln, Nebraska
Date of this Version
2009
Citation
Published in Proceeding, Western Section, American Society of Animal Science (2009) 60:
Abstract
Reproductive efficiency in young beef cows is often compromised due to a mismatch of physiological demands and suboptimal environmental conditions. Studies conducted at the Corona Range and Livestock Research Center from 2000 to 2007 evaluated 3 postpartum supplement strategies increasing in glucogenic precursors (GP). Reproductive variables, milk production, and serum metabolites were used to assess supplement effectiveness and economics associated with young beef cow production (n = 379) on native range. Supplements were individually fed 2×/wk at 1135 g/d (2003-2004) or 908 g/d (all other yr) and provided: 1) 327 g CP, 109-118 g undegradable intake protein (UIP), 44-47 g GP (CON); 2) 327-341 g CP, 142- 157 g UIP, 57-70 g GP (BP); 3) 327 g CP, 151-173 g UIP + 40 – 100 g of propionate salt (NutroCal, Kemin Industries, Inc.), 93-141 g GP (P). Blood samples were collected 1×/wk (2000) or 2×/wk (2001-2007) for progesterone analysis to estimate days to first estrus. Cows were exposed to bulls for 60 d or less and pregnancy was confirmed by rectal palpation at weaning. Number of days to first estrus after calving decreased and pregnancy rates increased linearly (P ≤ 0.02) with increasing supplemental GP. Milk production exhibited a quadratic (P = 0.04) response to increasing GP with cows fed BP producing the most amount of milk (5920, 6812, and 6217 ± 421 g/d for CON, BP, and P, respectively). Total kg of calf weaned per cow exposed for the supplemental year and subsequent year was greater (P = 0.07) for cows fed P than the other supplements (418, 410, and 435 ± 40 kg for CON, BP, and P, respectively). These data suggest feeding young cows additional GP in the form of propionate salts allows for repartitioning of nutrients away from milk production and towards reproduction.