Short‐term fasts and the ingestive behaviour of grazing cattle

Abstract

Abstract Twelve tethered Angus cows (Bos taurus) weighing 471 ± 18 kg were used in a balanced changeover design to estimate the direct (D), residual (R), and permanent (P) effects of 1,2, and 3 h fasts following 2 h grazing sessions on the ingestive behaviour of cattle grazing swards of endophyte‐ (Acremonium coenophialum Morgan‐Jones and Gams)‐free tall fescue (Festuca arundinacea Schreb. cv Kentucky 31) (Exp I) and lucerne (Medicago sativa L. cv Arc) (Exp II). Herbage dry‐matter (DM) mass (> 5 cm) and individual herbage DM allowances were 1‐16 t ha‐1 and 50 kg per hour in Exp I and 1‐861 ha‐1 and 78 kg per hour in Exp II, respectively. In Exp I, P effects of fasting followed trends of R effects since the D effects were small. Mean DM intake rates (P) were 2‐2., 1‐8, and 1‐3 kg h‐1 for cows given 1, 2, and 3 h fasts, respectively. Mean intakes (DM) per bite (P) were 082, 071, and 045 g bite‐1 for cows assigned 1, 2, and 3 h fasts, respectively. Rates of biting were not affected by fasting and averaged 45 bites min”’. In Exp II, P effects followed trends in D effects since R effects were small. Mean DM intake rates (P) were 20 , 22, and 3‐0 kg for cows subjected to 1,2, and 3 h of fast, respectively. Rates of biting (P) were 24, 27, and 32 bites min‐1 for cows after 1, 2, and 3 h fasts, respectively. DM intakes per bite (P) were not affected by fasts and averaged 1‐46 g bite‐1. The behavioural responses of cattle to interval between meals were attributed to differences in flow characteristics of ingesta of lucerne and tall fescue in the gastrointestinal tract.