Effects of concentrate type and level on the performance and health of finishing Hereford bulls given a grass silage-based diet and reared in cold conditions

A 2 × 2 factorial design with 32 Hereford bulls with an initial live weight (LW) of 307 kg was used to study the effects of (1) concentrate type and (2) concentrate feeding intensity on animal performance and health in cold conditions. The experiment included periods P1 (140 d) and P2 (on average 87 d) and consisted of two types of concentrate during P1–P2 (farm-made concentrate mixture, F; commercial compound, C) and two intensities of concentrate feeding pre slaughter during P2 (restricted, R; adlibitum, A). Concentrate was offered on average 2.3 kg dry matter (DM)/d during P1. During P2, concentrate was offered 3.0 kg DM/d on diet R and ad libitum on diet A. Grass silage (GS) was offered ad libitum.The proportion of concentrate in the daily DM intake was 0.29, 0.44, 0.29 and 0.50 during the entire experiment for diets FR, FA, CR and CA, respectively. On average, the intake of GS was lower on diet A than on diet R (P < 0.01, 5.1 vs. 6.2 kg DM/d). During P2, the intake of concentrate was 8.8 and 7.0 kg DM/d (P< 0.10) on diets CA and FA, respectively. The digestibility of diet neutral detergent fibre during P1 was lower on diet F than on diet C (P< 0.05, 0.674 vs. 0.748) and during P2 it was lower on diet A than on diet R (P< 0.01, 0.515 vs. 0.691). Animals on diet A consumed on average 0.28 kg/d less (P< 0.05) feed DM for LW gain than those on diet R. Comparing A and R during P2, the substitution rate was 0.71 kg silage DM per kg DM of concentrate with diet F, the corresponding value with C being 0.53. The LW gain during the entire experiment was 1580 and 1413 g/d (P< 0.01) on diets A and R, respectively. Treatments had no effect on the kill-out rate, EUROP carcass conformation and carcass fat classification, averaging 571 g/kg, 7.9 and 4.5, respectively. Beef flavour, meat tenderness and juiciness as well as serum cortisol and blood lactate were unaffected by the treatments. One bull on diet FA was removed from the experiment due to recurrent bloat. No other signs of disease were observed. It is concluded that production traits were unaffected by the concentrate type, but the ad libitum concentrate feeding improved the growth rate of the bulls.