Evaluation of Models to Predict Energy Efficiency of Ewes During the Late gestation

This study compared the six non-linear functions namely exponential, hyperbolic, power, incomplete Gamma, Gamma, and Weibull using fat mobilization and energy efficiency percentage in Iranian native ewes during the late gestation. Twenty ewes were distributed into five equal treatments through the late gestation adopting restricted feeding. The treatments comprised of: corn silage fed alone (T1) or along with chopped alfalfa (T2), un-chopped alfalfa (T3), chopped wheat straw (T4) and un-chopped wheat straw (T5). Due to restricted feeding, all ewes lost their body weight (BW) but it did not have any effect on their health condition. Pooled data gathered from all ewes made the data set and the boot strapping procedure was used for re-sampling up to 1200 times. Different mathematical functions consisted of exponential, hyperbolic, power, incomplete Gamma, Gamma, and Weibull were evaluated with regard to their ability to describe the relationship between fat mobilization and energy efficiency percentage. Based on the goodness of the fit of different criteria and statistical performance, convergence percentage of the three two-parameter functions along with the Gamma function were considerably higher (100%) than the Weibull (75.33%) and incomplete Gamma (99.08%) functions, suggesting that these functions would be the best models. However, based the t-test carried out for predicted and observed values (n=24000), the hyperbolic function showed to be superior to other functions (P=1.000) with 100% convergence and lower parameter. The results of all functions revealed the fact that decreased energy efficiency percentage was the consequence of higher fat mobilization in ewes at the late of pregnancy.