Factors affecting first lactation traits, expected breeding value and breeding efficiency in karan fries cattle

The present study was carried out in Karan Fries strain of cattle maintained at the NDRI, Karnal. Data were classified on the basis of sire, level of inbreeding, season and period. The effect of sire was significant on FLY, TFLY, MY/FLL, MY/FCI AND EBV (P0.01) and 10 and 15% sires had superiority over herd average of 11 and 7% for FLY and 25 and 15% for TLFY. The effect of level of inbreeding was significantly on FLY, TLFY,MY/FLL and MY/FCI (P0.05). Decrease in production performance of above these traits were recorded with the increase in level of inbreeding, though the effect was significantly adverse in highly inbred (F12%) group of animals. Deterioration in reproductive performance was also recorded in highly inbred cows. Inbreeding had more effect on first lactation performance than later lactations. The regression analysis, however, showed adverse but nonsignificant effect of inbreeding in most of the production traits and significant on FSP, FCI and MY/FCI (P0.05). The effect of season of calving was significant on FLL,FSP and FCI(P0.05). Summer calvers had maximum lactation length, whereas, autumn calvers had minimum FSP AND FCI. The FSP,FCI,MY/FLL and MY/FCI were significantly influenced by period of calving. Significantly consistent increase in milk production efficiency traits was observed over the periods and availability of daughters of some progeny tested sires in last period might be the reason of it. The overall findings revealed large variation in transmitting ability of sires for production traits, adverse effect of high level of inbreeding on performance and fluctuation in performance due to both genetic and non-genetic factors, therefore study suggests use of progeny tested sires, keeping of inbreeding under safer limit and management intervention for consistent improvement of herd.