PRODUCTIVE LIFETIME AND LIFETIME EFFICIENCY IN HOLSTEIN COWS.

The lifetime performance of dairy cows affects herd profit margins. Although it is important for cows to have a long life (from birth to culling), their lifetime efficiency is strongly affected by their productive life (number of days in milk). In the performance evaluation systems in South Africa, the genetic evaluation of cows and sires do not include lifetime performance as a genetic trait. Therefore, as a consequence the importance and implications were studied by the authors cited below. They studied the effect of non-genetic factors on the lifetime performance of Holstein cows as indicated by productive life efficiency and lifetime efficiency.  

The lifetime efficiency for each cow was calculated by dividing the total lifetime milk, fat and protein yield of cows by their total lifetime as indicated by the interval (number of days) between birth date and age at the end of the last lactation. The productive life efficiency for each cow was calculated by dividing the total lifetime milk, fat and protein yield of cows by their productive life.  Holstein cows born between 1980 and 2008 were included in the study. Cows calving down before 18 months of age and herds with fewer than 30 records over the 28 year period were removed. The non-genetic factors investigated included year of birth, season of birth, month of birth, year of calving, season of calving, month of calving, parity and age at first calving.

As expected, lifetime efficiency for milk, fat and protein production increased with lactation number.  All non-genetic factors affected lifetime efficiency and productive life efficiency significantly. The two parameters increased up to the 24^th month of age at first calving, where after it decreased.  Cows born in summer had a higher lifetime efficiency and productive life efficiency compared to winter born cows. The two parameters also increased as lactation number increased up to 4^th lactation after which it stabilized.  Cows which calved in summer had a higher lifetime efficiency and productive life efficiency compared to cows which calved in winter. As longevity is primarily affected by reproduction performance, improving the fertility of cows is vital towards improving lifetime production and lifetime efficiency.

Reference:

H.L. de Waal, C.J.C. Muller, M. van der Rijst& M.M Scholtz, 2017. Productive lifetime and lifetime efficiency in Holstein cows as affected by non-genetic factors. In: Proc. Of the 50th Annual SASAS Congress, Port Elizabeth, 18-20 September 2017.