Feeding a high-energy finishing diet upon arrival to high-risk feedlot calves: effects on health, performance, ruminal pH, rumination, serum metabolites, and carcass traits

This study evaluated the impacts of feeding a high-energy finishing diet during both the receiving and finishing period compared with a lower-energy receiving diet with adaptation to the finishing diet on health, performance, serum chemistry, ruminal pH, rumination, and carcass characteristics of high-risk feedlot cattle. Five truck-load blocks of steers (n= 101) and bulls (n= 299) were used in a generalized complete block design and randomly assigned to receive: 1) finishing diet for the entire feeding period (FIN) or 2) receiving diet for the first 56 d, followed by a transition to the finishing diet (REC). All cattle were fed ad libitum and consumed the same diet by day 74. A subset of cattle (n= 48) was randomly selected to quantify ruminal pH, temperature, and rumination time. Ultrasound images were collected on days 0, 74, and 146 to determine fat thickness over the 12th rib and rump, and carcass characteristics were determined after slaughter. Cattle fed FIN had less (P< 0.01) dry matter intake (DMI) from days 0 to 74, but DMI did not differ (P= 0.80) after day 74. From days 0 to final, DMI was 0.26 kg less for FIN compared with REC (P= 0.01). However, calculated metabolizable energy intake was not different from days 0 to 74 (P= 0.19), days 74 to final (P= 0.80), or overall (P= 0.78). Body weight (BW) on day 74 was greater (P< 0.01) and final BW tended to be greater (P= 0.10) for FIN compared with REC. Cattle consuming FIN had greater (P< 0.01) average daily gain and increased (P< 0.01) gain:feed from days 0 to 74. There were no differences (P≥ 0.31) in health outcomes. On day 74, FIN had greater (P= 0.04) fat thickness over the rump and rib but did not differ (P≥ 0.52) on day 146. Carcasses of FIN had greater (P= 0.04) hot carcass weight with no difference (P≥ 0.11) in ribeye area, 12th rib fat thickness, yield grade, or quality grade. There was no difference (P= 0.18) in liver abscess rate. There was a diet × day interaction for blood urea nitrogen (P= 0.02) such that concentration decreased from days 0 to 28 in both treatments, but was less on day 28 for FIN. Ruminal pH was greater on days 2 and 61 and rumination time was less from days 0 to 28 for FIN (diet × day interaction; P< 0.01). Overall, these results suggest that providing a finishing diet fed ad libitum to high-risk calves upon arrival may be a viable alternative to a low-energy receiving diet.High-risk cattle may not require a low-energy receiving diet containing high proportions of roughage upon arrival to the feedlot.When high-risk cattle arrive at the feedlot, they have low feed consumption and a greater risk for disease because of stress, inflammation, and exposure to pathogens. Because of reduced feed consumption, newly arrived cattle may not be able to meet their energy requirement for growth during the first several weeks after feedlot arrival. Therefore, providing a high-energy finishing diet (FIN) when stressed cattle arrive at the feedlot may allow for greater growth performance and improved health when compared with a traditional, low-energy receiving diet that contains more roughage (REC). Our study evaluated this concept and we observed that cattle fed FIN had greater body weight, average daily gain, and gain:feed (G:F) within the first 56 d when the different diets were fed, with no difference in growth performance after the cattle consuming REC transitioned to FIN on day 74. However, cattle consuming FIN had greater hot carcass weight and G:F over the entire feeding period. There were no differences in health outcomes among treatments. Overall, providing a high-energy finishing diet to high-risk cattle upon arrival to the feedlot improved growth performance with no impact on health.