Frequency of concentrate supplementation for cattle fed barley straw. 1. Effect on voluntary intake, ruminal straw disappearance, apparent digestibility and heat production

Abstract

Five ruminally cannulated crossbred steers (474 ± 30 kg) were fed diets containing 70% barley straw and 30% concentrate in an unbalanced 5 × 5 Latin square design experiment to investigate the effects of frequency of feeding barley grain-based concentrates (daily, alternate days or every third day) with different dietary protein (7.9 and 11.5%) on voluntary intake of straw, ruminal disappearance of straw, apparent digestibility, and heat production. Neither frequency of feeding nor dietary protein concentration influenced voluntary intake of straw, nor did cattle eat differing amounts of straw on days when concentrate was fed in comparison with days when concentrate was not fed. Protein supplementation increased (P < 0.01) 24-h ruminal straw disappearance, but did not affect disappearances at other times. Concentrate feeding frequency had no influence on rate of ruminal disappearance of straw. Apparent digestibilities of dry matter, gross energy, acid detergent fibre (ADF) and crude protein were 5, 6, 8 and 33% higher (P < 0.05), respectively, in diets containing the high-protein concentrate, but were not affected by frequency of concentrate feeding. Heat production (kJ kg-0.75) tended to be reduced (P = 0.06) by 4% in steers fed concentrate on alternate days in comparison with steers fed concentrate daily. Dietary protein concentration had no influence on heat production even though digestible energy intake was 10% higher when the high protein concentrate diet was fed. It was concluded that concentrate can be fed every second day without any negative impact on intake and digestibility, with a possible benefit of a reduction in energy lost as heat. More research, however, is required to study the feasibility of feeding concentrate every third day. Key words: Cattle, straw, protein, feeding frequency, digestion, heat production