A comparison of different metabolic types between goat kids and lambs: Key blood constituents at different times in the first two months after birth

Abstract

With the aim of establishing the metabolic causes of the differences in the corporal development of goat kids vs. lambs, diurnal patterns of serum concentrations of some key metabolites in relation to the energy and protein utilization were determined. For this, every 5 days from the 10th until the 60th day after birth, the pre-feeding and 1, 2, 4 and 8 h post-feeding levels of glucose, non-esterified and esterified fatty acids, urea and total protein were determined. Between goat kids and lambs, there were no outstanding differences for the diurnal mean values of glucose, urea and total protein concentrations in the serum. With the exception of the values measured at 0 and 8 h post-feeding and at 10 and 45 days of age, mean values of serum non-esterified fatty acid concentrations in kids were higher ( p<0.05) than in lambs. Mean values of esterified fatty acid concentrations measured at 35 and 40 days of age and at 1, 2 and overall at 4 h post-feeding, were generally higher ( p<0.05) in kids' serum than in lambs' serum. Pre-feeding mean levels of non-esterified fatty acids for kids and lambs were very similar, resulting at the same time values, two and seven times higher than those measured 1 h post-feeding; 419 vs. 235 μmol/l for kids and 386 vs. 56 μmol/l for lambs, respectively. From these results it is concluded that goat kids may have a higher rate of fat mobilization than lambs, understanding this as the net result of the balance between the processes of lipogenesis, lipolysis and re-esterification of the fatty acids released during lipolysis. At the same time, and in spite of that, goat kids utilize dietary protein with a higher efficiency than lambs; this difference was not supported by blood levels of nitrogenous metabolites.