CONTRIBUTIONS REGARDING THE STUDY OF PRODUCTIVE LONGEVITY OF A BNR POPULATION FROM DOAGA FARM, VRANCEA COUNTY

D. Cozma, V. Ujică, C.E. Nistor Ioana Raluca Pântia, I. Nistor, Ancuţa Elena Coşuleanu

Abstract
From the analysis of literature regarding the cattle's longevity resulted that the research, with implications of genetic and economic aspects in dairy cows exploitation, is still a poor chapter, so the theme it is well motivated and very actual. Regarding the productive longevity study at BNR breed from Doaga Farm, Vrancea County, resulted that the duration of productive life (productive longevity) at those 167 cows which finished their productive career was of 997.12 days. The cows from this farm were exploited, in average, only 3.26 normal lactations and did not give the maximum potential of production in exploitation period. At the studied population the production usage index of the cows had a mean value of 83.83% close to the one for a dairy cow farm. Average production was of 22,927.96 kg of milk, with limits of 28,175.58 kg at cows from at indigenous bulls and 21,485.86 kg at the ones from imported bulls. Having in view the productive lifetime at the studied population we obtain a quantity of 22.93 kg milk per day of productive life, respectively 22.09 kg/day at the daughters of indigenous bulls and 23.26 kg milk/day at the daughters of imported bulls. From the analysis of survival percentage through "Survival Analysis" resulted that after first lactation remain only 76.1% from initial herd, and after first four lactations 14.4%. Survived till lactation sixth only 6 cows (3.6%) from the initial herd and a descendant cow from an imported bull survived seven lactations. A detailed analysis of the out of herd exists enlightened on the first place the alteration of reproductive function followed by the alteration of udder and members, as imperious consequence of the influence of technological exploitation factors, poor management and in a low measure by the genetic factors.

Key words: productive longevity, BNR, milk production