Shahrekord University, Iran
Title: Bootstrapping method, and it's using for evaluation of models to predict energy efficiency in pregnant ewes
Biography: Ali Moharrery
Twenty pregnant, native fat-tailed ewes aged approximately 36 ± 1.5 months, with body weights (BWs) of 55 ± 6 kg and totally 100 ± 9 days of pregnancy period, were selected for the experiment. Restricted feeding was applied approximately up to 33% of their requirements for all ewes according to NRC (2007). All data from calculated of the total fat mobilization (g/day) and energy efficiency percentage has been used for evaluation of the models. Due to limited size of data set, the validity of variance estimates and normality assumptions as well as confidence interval estimates may be questionable. Hence, bootstrapping technique was used for re-sampling up to 1200 times. Different mathematical functions consisted of exponential, hyperbolic, power, incomplete gamma, and gamma 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 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.