Chromium and protein supplements for growing-finishing beef steers fed barley-based diets

Abstract

The effect of chromium supplementation on rate and efficiency of gain and morbidity in normally managed calves and calves with additional imposed stress was assessed in a 28-d trial involving 192 crossbred steer calves (262 ± 20 kg) in exp. 1. Imposed stress consisted of withholding of feed and water for an additional 12 h after arrival in the feedlot and mixing cattle 12 and 72 h after arrival. Chromium supplementation had no influence on rate of gain or efficiency of gain or on morbidity during the initial 28 d in the feedlot. Additional imposed stress increased weight loss from 7.0 kg to 14 kg during first 10 d in the feedlot and was associated with a 19% reduction (P < 0.001) in feed dry matter (DM) intake during the first 10 d. However, by 28 d no differences in daily gain or feed conversion due to imposed stress were detected. Morbidities during exp. 1 were 31% for normally managed calves and 44% for stressed steers (P = 0.05). In exp. 2, the effect of chromium supplementation, maturity of barley silage, and type of protein supplement [control, urea, canola meal, and blood meal/corn gluten meal (bypass protein)], on rate and efficiency of gain and carcass characteristics was determined in a growing-finishing experiment using the calves from exp. 1. Supplemental chromium had no detectable effect on any measured parameter when a barley silage-based diet (silage 68% of DM) was fed for 70 d or when a high concentrate diet (concentrate 86% of DM) diet was fed for 91 d. Maturity of silage did not affect rate or efficiency of gain in the growing period however fewer steers (P = 0.03) fed the more mature silage were sick than when silage harvested 10 d earlier was fed (morbidity of 3 vs. 12%). During the 70-d growing period steers supplemented with canola meal tended (P = 0.06) to consume more DM than those fed the control or bypass protein supplements (7.84 vs. 7.37 and 7.38 kg d −1 ). However, no differences in rate or efficiency of gain were detected in this period. During the 91 d finishing period steers fed canola meal supplement consumed more DM (P = 0.004) than those fed control or bypass supplements. The amounts of DM consumed per kg gain during this period were 6.07, 6.05, 6.09, and 5.79 kg (P = 0.09) for steers fed the control, urea, canola, and bypass supplements, respectively. It was concluded that rate and efficiency of gain and incidence of sickness were not influenced by chromium supplementation either in the first 28 d in the feedlot or throughout the total feeding period. Protein supplementation had no detectable influence on rate or efficiency of gain in either the growing or finishing penods. Key words: Chromium, stress, protein, calves, gain, feed efficiency