Effect of crude protein level in high grain diets on calf growth and feed utilization

Keywords: calves, early weaning, growth, intake, N utilization


This study assessed the effect of crude protein level in the diet on animal performance, feed conversion ratio and N utilization, in early-weaned lot-fed calves. Four iso-energetic rations were formulated (ME: 12.0 MJ/kg dm) differing in the crude protein content (CP: 12%, 15%, 17% and 21%, DM basis), and offered in a random experimental design to 24 Hereford calves (107.2 ± 21.5 kg). Animals were individually housed and fed ad libitum twice a day for 84 days. Increasing CP levels in the diet promoted a quadratic response (P<0.01) for dry matter intake (kg/d) and liveweight gain (LWG, kg/d), with maximum LWG of 1.36 kg/d for CP= 17.5%, without differences in subcutaneous back fat thickness (3.70 ± 0.73 mm, P = 0.25) or feed conversion ratio (4.44 ± 0.26, P> 0.10). As CP increased in the diet, N consumption increased quadratically (P <0.01), and an improvement was observed for CP (P = 0.053) and ndf (P = 0.020) apparent digestibility. Daily excretion of N in feces tended to decrease (P = 0.06), while urea-N concentration both in blood (P = 0.013) and urine (P = 0.046) increased. These results show that a level of 17% CP in the diet would optimize the performance of lot-fed early-weaned beef calves while controlling the excretion of N to the environment.

How to Cite
Beretta V, Simeone A, Morteiro I, Young I. Effect of crude protein level in high grain diets on calf growth and feed utilization. Agrociencia Uruguay [Internet]. 16Nov.2020 [cited 27Jan.2021];24(2):1-12. Available from: http://agrocienciauruguay.uy/ojs/index.php/agrociencia/article/view/111
Animal production and pastures