Relationship between productive and reproductive parameters of dairy cows in different production systems
Abstract
The majority of the milk producing systems in Argentina are based on the use of perennial and annual pastures plus supplementation with cereal grains and conserved forages. The genetic change that occurred in Argentine dairy cattle was due principally to the importation of semen from the USA and Canada. In those countries the Holstein breed was selected over many years for milk yield and body size under conditions of intensive management. It has been observed that upon increasing milk producing potential as a result of genetic selection, reproductive indexes deteriorate. Under grazing conditions it is impossible to control environmental conditions to the same or nearly the same degree as in intensive systems. Therefore, the use of animals originating from intensive systems under grazing conditions results in a mismatch between the requirements of the new genotype and those that the environment can provide. Thus the increase in individual production potential could be detrimental to the overall productivity of the grazing system, since this system cannot sustain those high levels of production