Effects of feeding lubabegron on gas emissions, growth performance, and carcass characteristics of beef cattle housed in small-pen environmentally monitored enclosures during the last 3 mo of the finishing period.

The development of technologies that promote environmental stewardship while maintaining or improving the efficiency of food animal production is essential to the sustainability of producing a food supply to meet the demands of a growing population. As such, Elanco (Greenfield, IN) pursued an environmental indication for a selective ß-modulator (lubabegron; LUB). LUB was recently approved by the United States Food and Drug Administration (FDA) to be fed to feedlot cattle during the last 14 to 91 d of the feeding period for reductions in gas emissions/kg of unshrunk final BW and HCW. A 4 × 2 factorial arrangement of treatments was used with the factors of dose (0.0, 1.38, 5.5, or 22.0 mg·kg-1 DM basis) and sex (steers or heifers). Three 91-d cycles were conducted (112 cattle/cycle) with each dose × sex combination being represented by a single cattle pen enclosure (CPE; 14 cattle/CPE) resulting in a total of 168 steers and 168 heifers (n = 6 replicates/dose). There were no interactions observed between dose and sex for any variable measured in the study (P ≥ 0.063). Five gases were evaluated for all pens based on CPE concentrations relative to ambient air: NH3, CH4, N2O, H2S, and CO2. Cumulative NH3 gas emissions were reduced by feeding cattle 5.5 and 22.0 mg·kg-1 LUB (P ≤ 0.023) and tended (P = 0.076) to be lower for the cattle fed 1.38 mg·kg-1 LUB compared with the negative controls (CON). The cumulative NH3 gas emission reductions of 960 to 1032 g, coupled with HCW increases (P ≤ 0.019) of 15 to 16 kg for all LUB doses vs. CON, led to reductions in NH3 gas emissions/kg HCW for all three LUB treatments (P ≤ 0.004). Similar to HCW, reductions in NH3 gas emissions/kg of unshrunk final BW were observed for all LUB doses (P ≤ 0.009) and were attributable to both decreases in NH3 gas emissions and numerical increases in BW. Dose had no effect on cumulative emissions or emissions standardized by BW or HCW for the other four gases (P ≥ 0.268). LUB is a novel tool to reduce emissions of NH3 gas per kilogram of unshrunk live BW and hot carcass weight.

Effects of Zeranol upon luteal maintenance and fetal development in peripubertal gilts.

Eighty gilts were utilized to determine whether zeranol implants could maintain hCG-induced corpora lutea (CL) in peripubertal gilts and to examine the effects of a Zeranol implant on fetal development. Crossbred gilts (171+/-0.3 days of age, 109.1+1.4 kg) were blocked by weight and ancestry to control (n=40) or treatment (n=40) groups. To induce ovulation and CL maintenance, treated gilts received 500 IU of hCG i.m. and a Zeranol ear implant (Ralgro, 36 mg; day 0). All gilts were checked once daily for estrus with a mature boar from days 3-58 of the experiment. On day 42, treated gilts received two 10 mg injections of Lutalyse (PGF(2)alpha) spaced 6 h apart. Treated gilts not displaying estrus within 7 days of PGF(2)alpha received two additional 10 mg of PGF(2)alpha spaced 6 h apart on day 49. On days 44-58, gilts detected in estrus were inseminated twice, 24 h apart with pooled semen via AI. Blood samples were obtained on days 0, 7, 18 and 42 and analyzed for serum progesterone (P(4)). Bred gilts were slaughtered on days 58-62 of gestation. Ovulation, as determined by serum concentrations of P(4) on day 7 of the experiment, was induced by hCG in 79.5% of treated gilts. Zeranol implants, however, failed to increase (P>0.05) the proportion of gilts available for breeding (treated, 21/39; control, 18/40). Of gilts inseminated on days 44-58, 16/21 treated gilts and 16/18 control gilts were pregnant at slaughter on days 58-62 of gestation. Number of fetuses (7.5 versus 12), fetal weight (83 versus 121 g), fetal length (117 versus 132 mm) and fetal survival (45% versus 78%) were reduced (P<0.001) by Zeranol implants. These data indicate that treatment of peripubertal gilts with a 36 mg Zeranol implant did not increase the proportion of gilts available for breeding while causing deleterious effects upon the fetuses.