Development of a predictive model for daughter pregnancy rate and standardization of voluntary waiting period

A predictive model for daughter pregnancy rate (DPR) in Indian Murrah buffaloes has been developed. The data pertaining to first lactation reproduction traits, viz., age at first calving (AFC), first service period (FSP), and number of services per first conception (NS/FCON) of 719 Murrah buf- faloes calved from 1985 to 2010 at the National Dairy Research Institute (NDRI), Karnal (Haryana), India were ad- justed against significant environmental influence. First lacta- tion reproduction records of 474 Murrah buffaloes were used for determining voluntary waiting period (VWP) and estimat- ing DPR. Seven simple and multiple regression models in each case were developed where the buffaloes had their first insemination after 63 days (DPR 63), 84 days (DPR 84), and 105 days(DPR 105)offirst calving.Among the seven models (ItoVII)forDPR63,DPR84,andDPR105,modelII,having only FSP as an independent reproduction variable, was found to be the best prediction model, based on the four statistical criterions (high coefficient of determination (R 2 ), low mean sum of squares due to error (MSSe), conceptual predictive (CP) value, and Bayesian information criterion (BIC)). Three linear equations were developed using model II, viz., DPR 63=0.0033 (274−FSP), DPR 84=0.0027 (332−FSP), and DPR 105=0.0027 (310−FSP). The average errors for the prediction of DPR 63, DPR 84, and DPR 105 were 1, 13, and 8 %, respectively. Therefore, 63 days of VWP is the optimum period for getting the best DPR in Indian Murrah buffaloes.