Influence of dietary cobalt on performance, nutrient digestibility and plasma metabolites in lambs

Two experiments were conducted to study the effects of different inclusion levels of dietary cobalt (Co) on performance, nutrient digestibility and plasma metabolites in lambs. Experiment 1: sixty, 12-week-old weaned lambs (Chinese Poll Dorset × Small Tailed Han) were randomly divided into five groups which were fed with the basal diet containing 0.086 mg Co/kg DM, the basal diet supplied, respectively, with 0.25, 0.50, 0.75 and 1.00 mg Co/kg DM as reagent grade CoSO4·7H2O for 10 weeks. Experiment 2: four lambs from each group in Experiment 1 were randomly allocated to the individual metabolic crates to measure the effects of dietary Co on apparent nutrient digestibility. Average daily gain and average daily feed intake were highest at the intermediate level (total diet Co of 0.586 mg/kg DM) (P<0.05). However, there was no difference in gain/feed. Supplemental 0.50 mg Co/kg DM resulted in highest digestibility of dry matter, organic matter, crude protein and acid detergent fiber and metabolizable energy intake (P<0.05). Neutral detergent fiber digestibility was increased at an increasing rate (P<0.05). Co supplementation at the intermediate level showed highest plasma vitamin B12 concentration and lowest plasma methylmalonic acid concentration (P<0.05), whereas there were no differences in plasma concentrations of folate and homocysteine. Plasma glucose concentration was linearly increased (P<0.05). In conclusion, the growth of Chinese Poll Dorset × Small Tailed Han lambs is compromised when fed a Chinese wildrye hay based diet containing 0.086 mg Co/kg DM. The recommended level of dietary Co for such lambs is between 0.336 and 0.586 mg/kg DM.