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Both dietary ingredients and technology used in the feedlot cattle industry have evolved in the past 30 years. As consumer concern for the sustainability of the feedlot cattle production increases, it is important to understand how production efficiency and greenhouse gas emissions have changed in this period. For this study, a model was developed to represent feedlot diets and technologies used in 1990 vs. 2020 and evaluate changes in growth performance and carbon footprint. Dietary changes from 1990 to 2020 included the use of byproduct feeds while decreasing corn and dry roughage inclusion rates. In 1990, available technologies included estradiol-only implants and monensin as a feed additive; whereas in 2020 use of combination implants including both trenbolone acetate and estradiol, monensin, and ractopamine hydrochloride (in the final 28 to 42 d) were common. In both 1990 and 2020 use of available technologies increased final body weight (BW), average daily gain (ADG), feed efficiency, and hot carcass weight (HCW) compared to no technology. From 1990 to 2020 initial BW, final BW, ADG, gain to feed ratio, and HCW increased, and dry matter intake decreased. Total days on feed (DOF) also increased by 43 days from 1990 to 2020. Compared to no technology, use of technologies in both 1990 and 2020 decreased total greenhouse gas emissions per animal (CO2e). Because cattle had greater DOF in 2020 than 1990, all sources of greenhouse gas emissions per animal increased. However, when expressed as CO2e/kg BW gain, emissions have decreased by 12.6% because of greater total BW gain in 2020. Feedlots in 2020 produced 48.15% more BW gain with 6.7% less cattle, while only increasing total CO2e by 23.42%, indicating changes in technologies and diet formulations have improved efficiency and reduced the carbon footprint of feedlot cattle production in the past 30 years. [ABSTRACT FROM AUTHOR]

This study evaluated impacts of feeding a finishing diet throughout both the receiving and finishing period compared to a receiving diet with adaptation to the finishing diet on health, performance, ruminal pH, and rumination of high-risk feedlot cattle. Five truck-load blocks of steers and bulls (n = 400) were used in a generalized complete block design and assigned to receive: 1) finishing diet for the entire feeding period (FIN) or 2) receiving diet for the first 56 d, followed by transition to the finishing diet (REC). All cattle were consuming the same diet on d 74. A subset of cattle (n = 48) were randomly selected to quantify ruminal pH, temperature, and rumination time. Ultrasounds were completed on d 0, 74, and 146 to determine fat thickness. Cattle fed REC had greater (treatment × day; P < 0.01) DMI from d 1 to 67 but less DMI from d 74 to 82, and DMI did not differ from d 83 to 174. Energy intake (treatment × day; P < 0.01) was greater for FIN from d 14 to 75. Cattle consuming FIN had greater (P ≤ 0.01) ADG and BW and improved (P < 0.01) gain:feed from day 0 to 74. At d 174, BW of FIN was 9.6 kg greater (P = 0.02). On d 74, FIN had greater (P ≤ 0.05) fat thickness but did not differ (P ≥ 0.61) at d 146. There was no difference (P ≥ 0.31) in health outcomes. Ruminal pH (treatment × day; P < 0.01) was greater for FIN on d 2 and 61, and rumination time was less (P < 0.01) for FIN from d 0 to 28. Overall, these results suggest providing a finishing diet to high-risk calves upon arrival may be a viable alternative to a traditional receiving diet. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of a single slow-release implant compared to two re-implant programs administered at either 120 days on feed (DOF) or 80 days from harvest on performance, carcass characteristics, and activity of serially harvested feedlot cattle. Using a randomized complete block design, steers (n = 4,680) were randomly assigned to 72 pens and 1 of 12 treatments in a 3 × 4 factorial arrangement. Treatments were either a slow-release implant (SR), an initial slow-release implant followed by re-implant at 120 DOF (SR+RI-120), or an initial slow-release implant followed by re-implant 80 days from harvest (SR+RI-80) administered to cattle harvested at 166, 180, 194, or 208 DOF. A 3-axis accelerometer ear-tag was used in a subset (n =1,080) of animals to quantify rumination time and activity. No interactions (P = 0.09) were observed for implant × DOF. Implant did not affect (P = 0.25) final BW, ADG, or DMI, but re-implanted steers had a greater (P < 0.01) G:F ratio than SR. Re-implanted steers also had greater (P = 0.03) HCW, dressed yield, and ribeye area, but less (P < 0.01) backfat, marbling, and empty body fat (EBF) compared to SR. Re-implanted steers had less (P < 0.01) choice and yield grade 4 and 5 carcasses than SR steers. As DOF increased, HCW, dressed yield, backfat, marbling, and EBF increased linearly (P < 0.01). The percentage of choice and yield grade 4 and 5 carcasses also increased (P < 0.01) linearly with additional DOF. An implant × day effect (P < 0.01) for weekly activity minutes suggests re-implanted steers had greater activity after re-implant administration. Re-implanting within the payout period of a slowrelease implant increases feed efficiency, HCW, dressed yield, and activity minutes, but decreases carcass fatness and reduces quality grade regardless of timing of secondary implant administration. [ABSTRACT FROM AUTHOR]