Nutrient Balance and Glucose Metabolism of Female Growing, Late Pregnant and Lactating Etawah Crossbred Goats

A study involving nutrient balances and radioisotope labeling techniques was undertaken to study energy and protein metabolism, and glucose kinetics of female crossbred Etawah goats, using 12 weaned (BW $14.0{\pm}2.0kg$), 12 late pregnant (BW $27.8{\pm}1.8kg$) and 12 first lactation does (BW $25.0{\pm}5.0kg$). Each class of animal was randomly allotted into 3 dietary treatment groups R1, R2 and R3, that received 100%, 85%, and 70% of ad libitum feed. The rations offered were pellets containing 21.8% CP and 19.3 MJ GE/kg, except for the lactating does who received pellets (17.2% CP and 18.9 MJ GE/kg) and fresh Penisetum purpureum grass. Energy and nitrogen balance studies were conducted during a two-week trial. Daily heat production (HP, estimated by the carbon dioxide entry rate technique), glucose pool and flux were measured. Equations were found for metabolizable energy (ME) and protein intake (IP) requirements for growing goats: ME (MJ/d)=1.87+0.55 RE-0.001 ADG+0.044 RP $(R^2=0.89)$ and IP (g/d)=48.47+2.99 RE+0.029 ADG+0.79 RP $(R^2=0.90)$; for pregnant does: ME (MJ/d)=5.92+0.96 RE-0.002 ADG+0.003 RP $(R^2=0.99)$ and IP (g/d)=58.34+5.41 RE+0.625 ADG-0.30 RP $(R^2=0.98)$; and for lactating does: ME (MJ/d)=4.23+0.713 RE+0.003 ADG+0.006 RP+0.002 MY $(R^2=0.86)$; IP (g/d)=84.05-5.36 RE+0.055 ADG-0.16 RP+0.068 MY $(R^2=0.45)$, where RE is retained energy (MJ/d), ADG is average daily gain in weight (g/d), RP is retained protein (g/d) and MY is milk yield (ml/d). ME and IP requirements for maintenance for growing goats were 0.46 MJ/d.kg $BW^{0.75}$ and 7.43 g/d.kg $BW^{0.75}$, respectively. Values for the pregnant and lactating does were in the same order, 0.55 MJ/d.kg $BW^{0.75}$ and 11.7 g/d.kg $BW^{0.75}$, and 0.50 MJ/d.kg $BW^{0.75}$ and 10.8 g/d.kg $BW^{0.75}$, respectively. Milk protein ranged from 3.06 to 3.5% and milk fat averaged 5.2%. Glucose metabolism in Etawah crossbred female goat is active, but glucose flux is low compared to temperate ruminant breeds which may implicate its role to support production.