Efficiency of various measures of persistency of milk yield in Sahiwal cattle

The first lactation production records of 351 Sahiwal cows maintained at National Dairy Research Institute, Karnal over a period of 52 years (1961-2012) were used to estimate the persistency measures using different methods viz. Rao and Sundaresan method, 1982 (P-1), P-TOMAX2 (P-2), P-TOMAX3 (P-3), P-SD2 (P-4), P-SD3 (P-5), P-YV (P-6) and Wood's function (P-7). The average persistency of milk yield estimated by above different methods viz. was 194 +/- 1.10, 145.10 +/- 0.81, 156.71 +/- 1.01, 2.29 +/- 0.04, 2.20 +/- 0.03, 1.00 +/- 0.03 and 0.14 +/- 0.02, respectively. The TOMAX(2) method was found to be most efficient out of all ratio methods and P-SD3 method was observed to be most efficient amongst variation of yields method. However, mathematical lactation curve model was found to be least efficient as compared to other methods for estimation of persistency.