Energy and Protein Requirements of Growing Lambs in Colombian Highlands.

Determining the nutritional requirements of lambs is necessary to formulate balanced rations and contribute to sustainable sheep production systems. However, limited information is available regarding the nutritional requirements of growing lambs in the Colombian highlands. Twenty-two Romney Marsh males were used. Initially, four lambs were slaughtered at 20 kg body weight (BW). The remaining 18 lambs were distributed into two groups, according to BW (light: 20 BW and heavy: 30 kg BW). Lambs were randomly allocated into one of three different nutritional schemes, according to voluntary intake (no restriction, and 25 and 50% restriction). All the animals received a totally mixed ration. When a voluntary-fed lamb gained 10 kg BW, the two other lambs restricted to 25 and 50% were slaughtered and dissected into components to determine protein and gross energy concentration. Energy and protein accumulation were analyzed through regression analysis. The net energy for maintenance was 82.3 kcal/kg BW, while the energy efficiencies for maintenance and gain were 0.72 and 0.29, respectively. Crude protein for maintenance was 1.78 g/kg BW, and the nitrogen efficiencies for maintenance and gain were 0.41 and 0.27, respectively. The maintenance requirement of energy was greater, while protein was similarly related to values reported in the literature; however, the efficiency of energy and protein use was lower in growing lambs. These results suggested that estimating energy and nitrogen requirements for growing lambs must be adjusted in Colombian highland conditions.