PS3-26. Impact of Hydration Strategies During a 48-hour Feed Deprivation Period on the Performance of Newly Received Feedlot Calves.

Abstract The objective of this study was to evaluate the effects of different hydration strategies during a 48-h fasting period on the performance of newly received Nellore calves in a feedlot system. Sixty-nine non-castrated Nellore males [270 kg ± 44 kg of body weight (BW); 12 months of age] were randomly assigned to the following treatments : 1) animals with restricted access to both water and feed for 48 h (CON); 2) animals with ad libitum access to water but restricted access to feed for 48 h (WTR); and 3) animals receiving an electrolyte replacement solution (BoviUp®, Salus Animal Nutrition, Brazil) ad libitum but with restricted access to feed for 48 h (HDT). The stock tank in the WTR and HDT treatments were refilled every 12 h. The HDT solution was diluted at a rate of 30 g/L. After the 48-h fasting period, animals were allocated to 12 experimental pens, where they remained for 28 d receiving the experimental diet (Table 1) and water ad libitum. Between days -2 and 0, treatments were applied, and BW was measured at 0, 4, 8, 12, 18, 24, 30, 36, and 48 h relative to the beginning of treatment application. Subsequently, animals were weighed on days 2, 7, 14, and 28. Data were analyzed using the PROC MIXED procedure of SAS. The model included the effects of treatment, experimental period, and their interactions as a fixed effect, with initial BW used as a covariate. Significance was declared at P ≤ 0.05 and tendencies at 0.05 < P ≤ 0.10. Treatment × period interaction was observed for BW (P < 0.001). During the first 4 h, BW was not affected by treatments (P ≥ 0.731). After 18 h, CON and WTR showed similar BW (P = 0.188), but both were approximately 10 kg lighter than HDT (P < 0.001). At the end of the 48-h fasting period, the greatest BW reduction was observed for CON (−35 kg), followed by WTR (−22 kg), whereas HDT showed the smallest loss (-3 kg; P < 0.001). Although average daily gain (ADG) from days -2 to 14 and 14 to 28 was not affected by treatments (P ≥ 0.118), HDT tended to show greater overall ADG (days - 2 to 28) compared with CON and WTR (+ 0.233 kg/day; P = 0.066). Consequently, greater BW was observed for HDT on days 7 (+ 4.8 kg), 14 (+ 5.5 kg), and 28 (+ 7.3 kg) compared with CON and WTR (P ≤ 0.046). In conclusion, providing an electrolyte solution during the fasting period is an effective strategy to reduce body weight loss and improve the performance of newly received feedlot cattle. For image description, please refer to the figure legend and surrounding text. For image description, please refer to the figure legend and surrounding text.