Feeding value of supplemental fat as a partial replacement for steam-flaked corn in diets for Holstein calves during the early growing phase

In calf-fed Holstein steers, the early growing phase is characterized by very high relative dry matter intake (DMI) accompanied with lower-than-expected efficiency of energy utilization. Although fat is commonly supplemented in growing-finishing diets, the comparative feeding value has not been investigated during the initial receiving-growing period. Eighty-four Holstein calves (127.7 ± 2.1 kg body weight) were used to evaluate the effects of including 3.5% of supplemental yellow grease (YG) in the diet on characteristics of growth performance and dietary energy utilization of calves during the early growth phase. Morbidity and mortality were not affected by dietary treatments. Yellow grease supplementation did not affect DMI, but tended to increase average daily gain (4.6%; P = 0.07), and increased (P ≤ 0.03) gain efficiency (5.8%) and dietary net energy for maintenance (NE_m) and gain (NE_g) by 4.1% and 5.3%, respectively. Based on performance data, the estimated NE value of supplemental YG was 4.67 and 3.68 Mcal/kg for NE_m and NE_g, respectively. These values are consistent with current tabular values assigned for vegetable oils (4.75 and 3.51 Mcal/kg), but markedly less (16.6%) than NE_m value assigned for YG (5.60 Mcal NEm/kg; NASEM, 2016. Nutrient requirements of beef cattle. 8th ed. Washington (DC): National Academy Press.).