| Abstrakt: |
Increased animal productivity has the potential to reduce the environmental impact per unit of consumable product and is believed to be the most promising and sustainable mitigation technique to meet increasing demand for high quality protein. The feedlot industry uses ionophores, antibiotics, growth implants, and β2-adrenergic agonists to improve health and growth performance of cattle. These technologies not only increase productivity but also alter microbes in the rumen and increase nitrogen retention in the animal, which may lead to changes in greenhouse gas (GHG), volatile organic compound (VOC), and ammonia (NH3) emissions from feedlot cattle. The present study investigated GHG, VOC, and NH3 emissions from 160 Angus crossbred steers. Steers were blocked by weight in a randomized block design and assigned to 16 pens of 10 animals each. Treatments applied were 1) control (CON; no technology application), 2) monensin and tylosin phosphate (MON), 3) monensin, tylosin phosphate, and growth implant (IMP), and 4) monensin, tylosin phosphate, growth implant, and zilpaterol hydrochloride (fed during the last 20 d of the feeding period; BAA). Cattle were on feed for an average of 107 d. Performance variables (DMI, BW, ADG, and G:F) and carcass traits (HCW, dressing percent, KPH, LM area, fat thickness, marbling score, yield grade, and quality grade) were measured. Gaseous emissions were measured during the last 10 d of the feeding period when animals were housed in 4 totally enclosed identical cattle pen enclosures. To quantify gaseous emissions a 4×4 Latin square design (n=4) was used. Gaseous emissions were analyzed using Proc Mixed in SAS and reported in grams per kilogram HCW per day and grams per kilogram per animal per hour. Treatment with IMP and BAA increased (P<0.05) ADG, final BW, and HCW. Cattle on BAA had greater HCW and LM area (P<0.05) and had lower (P<0.05) CH4, methanol, and NH3 emissions per kilogram HCW than cattle on the remaining treatments. Methane emissions were similar for CON and IMP treated cattle. Nitrous oxide emissions were similar across CON, MON, and IMP treated cattle and were higher in BAA treated cattle (P<0.05). The present study provides a better understanding of how application of growth promoting technologies to feedlot steers affects GHG, VOC, and NH3 emissions per kilogram of product. |
