|Mulliniks, J -|
|Kemp, M -|
|Cox, S -|
|Hawkins, D -|
|Cibils, A -|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 30, 2011
Publication Date: April 15, 2011
Citation: Mulliniks, J.T., Kemp, M.E., Cox, S.H., Hawkins, D.E., Cibils, A.F., Petersen, M.K. 2011. The Effect of Increasing Amount of Glucogenic Precursors on Reproductive Performance in Young Postpartum Range Cows. Journal of Animal Science 89(9):2932-2943. Interpretive Summary: Supplementing young cows grazing native range with a higher proportion of supplemental protein in the form of ruminally undegradable protein with glucogenic precursors in the form of calcium propionate decreased days to first estrus and increased pregnancy rates in 2- and 3-year-old range cows. Cows fed additional glucogenic precursors appear to wean heavier calves the following year, which increased returns beyond the expense of the higher cost supplement ingredients. Diets that supply additional glucogenic precursors may decrease serum ketone concentrations and increase serum acetate disappearance rate indicating more efficient energy metabolism and better use of forage energy. These indicators of changes in metabolism would be associated with more efficient overall energy metabolism, animal well-being, and reproduction.
Technical Abstract: Supplementing CP and propionate salts (PS) may improve returns in young range beef cows by increasing the dietary supply of glucogenic precursors which may have the effect of improving sensitivity to insulin. A 3-yr study conducted at Corona Range and Livestock Research Center from February to mid-July in 2005 (n = 80), 2006 (n = 81), and 2007 (n = 80) evaluated days to first estrus, kg of calf weaned, BW change, and metabolic responses in 2- and 3-yr-old postpartum cows grazing native range and individually fed 1 of 3, 36% CP supplements after parturition with increasing glucogenic potential (GP) supplied by undegradable intake protein (UIP) and PS. Supplements were isoenergetic and were fed at 908 g•cow-1•d-1 2× weekly. Supplementation was initiated 7 d after calving and continued for an average of 95 d. Supplements provided 1) 328 g CP, 110 g UIP + 0 g PS (NutroCALTM, Kemin Industries, Inc.), 44 g GP (0), 2) 328 g CP, 157 g UIP + 40 g PS, 93 g GP (40), or 3) 329 g CP, 158 g UIP + 80 g PS, 124 g GP (80). Body wt was recorded weekly and serum collected 2x weekly for progesterone analysis to estimate days to first estrus. Supplementation was terminated each year when cows reached BW nadir. Cows were exposed to bulls for 60 d or less starting mid-May and were determined pregnant by rectal palpation at weaning. Supplement and yr did not interact to influence days to first estrus or days and magnitude to BW nadir (P > 0.18). Days to first estrus exhibited a quadratic (P = 0.06) response to GP (77, 71, and 74 ± 2 d for 0, 40, 80, respectively). Pregnancy rates were 88, 96, 94% for 0, 40, and 80 fed cows, respectively (P = 0.12). Total kg of calf weaned per cow exposed to bulls (a measure of reproductive success) for the supplementation and following yr was greater (P = 0.05) for those fed 40 or 80 (378, 406, and 396 ± 10 kg for 0, 40, and 80, respectively). A supplement × year interaction was observed for predicted economic margins of 2- and 3-yr-old cows (P = 0.10). Cows fed 40 and 80 had increased margins over cows fed 0 in 2 out of 3 yr. However, supplement did not affect milk composition or yield (P > 0.53). Serum acetate half-life decreased linearly (P = 0.08) with increasing GP (35, 29, and 27 ± 3 min for 0, 40, and 80, respectively). Serum glucose half-life was similar among treatments (P = 0.88; 88, 97, 97 ± 15 min for 0, 40, and 80, respectively). This study implies that young postpartum cows fed additional glucogenic precursors may have improved reproductive efficiency and wean more calf weight per cow exposed to breeding.