Multivariate Characterization of Biological Efficiency in Dairy Cows in Grazing Systems

Retrospective data was used corresponding to the lactation of 216 first and multi-pregnancy cows, American-Canadian Holstein with registers of their whole productive life, from their entrance to the system till their sale or death, registers were gathered from1992-2012 in the Argentinian Holstein farm located in Casilda, province of Santa –Argentina. During the mentioned time, all the cows were managed in the same dairy premises. The animals were divided into two categories: pure cows (VP,n=88) and cows with breeding registers (VRC,n = 128). The variables under use were: age at first calving, in days (EPP), first calving – conception interval in days (IPP), milk production adapted to 305 lactation days, in litres (PL), the amount of butyric fat produced, in kilograms (GB), the number of calvings registered throughout its reproductive life (NP), milk index in litres (IL) and the fat index in kilograms (IG). There were statistically significant differences as regards the productive characteristics PL and GB. N average, throughout the cycle under study, the VP produced 591 litres of milk and 161 kg of fat more. There were no significant differences when considering the age of first calving or the calving – conception interval. VP cows registered higher IL and IG than VRC cows, with significant differences which favoured the former, in both cases. The four components generated by the multivariate analysis explained important portions of the total variance which lead to consider all of them when interpreting the joint relations between productive performance indicators and reproductive achievement. It is concluded that even though the biotypes under study behave differently, both coincide at the point of stating that those cows which belong to quadrant IV were those which presented the best adaptation to the environment, being the ones who live longer and with an intermediate reproductive efficiency, regardless their biotype.