Effects of Offering Different Amounts and Types of Supplemental Feeds to Growing Dairy Steers Fed Endophyte-Infected Fescue Hay Ad Libitum on Intake, Digestion, Passage Rate and Serum Prolactin Concentration

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Abstract
Ten Holstein steers (141 kg) were used in two 5×5 Latin-square experiments conducted simultaneously to determine the effects of offering different levels and types of feeds with endophyte-infected fescue given ad libitum. In Exp. 1, steers were given ad libitum access to infected fescue hay in the afternoon; in the morning fescue was given ad libitum (basal) or bermudagrass or clover hays were fed at .5 or 1.0% of body weight (BW). Supplementation did not affect total dry matter intake (P>.10), but supplementation at 1.0% of BW yielded total intake greater than supplementation at .5% of BW (P<.05). Supplementation did not change digestibilities of dry or organic matter (P>.10). Particulate passage rate was greater (P<.10) with supplementation at 1.0 than at .5% of BW, and increasing the level of supplementation from .5 to 1.0% of BW affected fluid passage rate positively with clover but negatively with bermudagrass (interaction, P<.05). Serum prolactin increased (P<.05) with all supplementation treatments, although no differences were observed between supplement type-supplementation level combinations (P>.10). Ground corn and wheat hay were supplements in Exp. 2. Total intake of dry matter was greater with supplements provided at 1.0 rather than at .5% of BW and for corn rather than wheat hay (P<.05). Neutral detergent fiber digestion (percent of intake and grams per day) rose when wheat hay was offered at 1.0 vs .5% of BW but declined when the level of supplemental corn increased from .5 to 1.0% of BW (interaction, P<.05). There were no differences among diets in particulate and fluid passage rates and serum prolactin concentration. Supplementation with nontoxic forage of a basal diet of infected fescue yielded intake substitution when forage was offered at .5% of BW, although incomplete substitution occurred with 1.0% of BW of supplemental forage such that total intake increased as compared to the lower level of supplementation. Copyright © 1987. American Society of Animal Science . Copyright 1987 by American Society of Animal Science