A total of 618 lactational milk yield records of first four parities at weekly interval from
1990 to 2001 (12 years) were collected for 284 Karan Fries cows sired by 53 bulls maintained
at Dairy Cattle Breeding Division, NDRI, Karnal. The persistency indices were estimated by five
different measures viz. Johansson and Hanson method (P1 and P2), Mahadevan method (P3),
Ratio method (P4) and Prasad method (P-5). The overall least square means for P1, P2, P3, P4 and
P5 were 87.34±1.27, 52.80±1.16, 1.46±0.02, 204.03±1.56 and 0.68±0.00 respectively.
The first calvers had the highest persistency of lactation across all the methods followed by
second calvers. The rainy calvers were most persistent whereas the winter calvers were least
persistent. The correlation between peak yield and lactation milk yield (0.610) was positive and
highly significant. There was significant and negative correlation of peak yield with all the
persistency indices across all the four parities. In general, the heritability estimates were very
low (0.01 to 0.17) with high standard errors. Johansson and Hanson’s measures of persistency
(P1 and P2) were found to be more reliable with values of their repeatability being 0.190 and
0.200 respectively. The lactational milk yield was predicted with around 62% accuracy using
the peak yield as a predictor.