Effect of Omnigen-AF on the Pre-Weaning Performance of Beef Calves

The objective of this research was to determine the effects of feeding OmniGen-AF, (OG, Phibro Animal Health Corp., Teaneck, NJ) to mature cows (n = 112) and primiparous heifers (n = 48) from 60-d pre-calving to breeding and to their calves in creep feeds for 90-d pre-weaning on calf performance. Mature cows were randomized into 16 pasture groups by age and heifers were randomized into 4 pasture groups at the University of Arkansas Southwest Research & Extension Center from 60 d prior projected calving to breeding (December 15, 2015-May 2, 2016). Corn gluten feed was supplemented to all cows at 1.4 kg·cow^-1·d^-1, prorated for 5-d per week feeding (2.5 kg/cow). Cows were fed OG a daily rate of 4g/45.4 kg. Calves (n = 146) were born between February 10 and April 15, with an average calving date of March 1. Creep feed (67% soybean hulls and 33% corn gluten feed, as fed basis) was offered at 1% BW from July 14-October 7, 2016. Calves were offered OG at a daily rate of 4g/45.4 kg in the creep feed. A subset of heifer calves in each pasture (n = 3/pasture) were inserted with an intravaginal device containing a temperature data recorder for a 9-d period during September, and core body temperatures (CBT) were recorded every 20 minutes. Birth date, birthweight, BW and BW change of calves were recorded and analyzed as CRD by ANOVA, using the mixed procedure of SAS. Fixed effects included treatment, parity group, the treatment by parity interaction; with sire (AI vs. natural service) and birth date included as covariables and pasture within treatment as the random effect. Analysis of CBT was conducted as a repeated measures analysis by hour with day as the repeated and calf the subject. Calves supplemented with OG gained more BW (P = 0.03) than CON calves during the creep feeding period (80.7 kg vs 72.5 kg, respectively), however BW at weaning did not differ (P = 0.27). A treatment by hour interaction (P < 0.01) for CBT was observed, with OG supplemented heifers having numerically lower CBT (-0.7 °C, P=0.19) at 1400 hr than CON heifers. Providing OG in the creep diet of calves was shown to have a positive influence on BW gain pre-weaning. Numerically lower CBT may indicate less heat stress in OG supplemented calves, but more research is needed to further substantiate these effects.