Effects of cottonseed meal supplementation time on ruminal fermentation and forage intake by Holstein steers fed fescue hay

Abstract

Four ruminally cannulated Holstein steers (average BW 303 kg) were used in a 4 × 4 Latin square design digestion trial to study the influence of daily cottonseed meal (CSM; 1.6 g of CP/kg of BW) supplementation time on forage intake and ruminai fluid kinetics and fermentation. Steers were housed individually in tie stalls and were fed chopped fescue hay on an ad libitum basis at 0600 and 1400. Treatments were 1) control, grass hay only (CON) and grass hay and CSM fed once daily at 2) 0600 (EAM) 3) 1000 (MAM), or 4) 1400 (PM). Ruminai NH3 N concentrations reflected a time of supplementation × sampling time interaction (P < .05); CON steers had the lowest (P < .05) ruminai NH3 N concentrations at all times other than at 0600, 1000, 1200, and 2400, when they did not differ (P > .05) from at least one of the supplemented groups. Forage intake, ratio of bacterial purine:N, rate of DM and NDF disappearance, and ruminai fluid kinetics were not influenced (P > .05) by supplementation time. Total ruminai VFA differed (P < .05) between CON and supplemented steers, as well as among supplemented steers (linear and quadratic effects P < .05). Acetate, propionate, and valerate proportions were influenced (P < .05) by a sampling time × supplementation time interaction. Under the conditions of this study, greater peak ammonia concentrations with morning supplementation than with afternoon supplementation did not stimulate ruminai fermentation or rate of NDF disappearance.