EASY TO USE APPROACHES TO CULL COWS.

In general, to improve the efficiency of milk production requires application of specific feeding, reproduction and breeding programmes simultaneously. As nutritional requirements differ, feeding management should emphasize the correct diets to replacement heifers and lactating and dry cows. Reproduction management should ensure a short interval from calving to first service, few services per conception for a short open period, and maintaining pregnancy to the next calving. Top performing cows should be identified annually to stay in the herd, whereas poor performing cows should be culled to improve the production and genetic base of the herd. This is normally done in heifers (based on estimated breeding values) or during first lactation, based on partial (105-day) or completed lactation records. However, there are easy to implement measures which can be used as well, which were pursued by the authors referenced below. Their studies investigated different easy ways of identifying poor performing cows based on production performance and efficiency measures.  

Milk production and live weight records of 221 first lactation Holstein cows were used to estimate partial (105-day) milk, fat and protein yields as well as alternative production indicators such as the Component Value [(6xfat yield + 13xprotein yield)/2)], and efficiency measures such as an alternative Kleiber Ratio [Net Energy requirement for milk production (NEL) divided by metabolic live weight (LW^0.75)] and the ratio between 105-day 4% fat corrected milk yield and the average live weight of the cows (Gaines formula). For the Component Value, 41 cows were below the threshold culling levels being 0.85 of the mean of all cows. Although 46, 40 and 32 cows were identified to be culled using the 105-d milk production, Kleiber Ratio and Gaines culling strategies, 89, 98 and 78%, respectively of these cows were identified as for the Component Value culling system. Thus, whereas it could be expected that these culling measures may identify different cows, a large percentage overlapping cows were identified resulting in small differences in the average milk yield and live weight for the cows remaining in the herd.  

For farmers with access to automatic recorded information on daily milk yield and live weight of cows, partial (105day) or completed first lactation milk yields divided by average live weight, provide an indication of the efficiency of production. Using this easy system, 95% of the same cows were identified to be culled when using more elaborate efficiency measures such as the Gaines formula, or the alternative Kleiber ratio, or the Component Value.

References:

C.J.C. Muller & M. Burger, 2017. Improving the efficiency of milk production in a dairy herd using different strategies. In: Proc. of the SALHC, Champagne Sports Resort, KZN, 5-7 June 2017.                                                                                                 

C.J.C. Muller, M. Burger & J.A. Botha, 2017. The effect of culling system on the milk yield and live weight of dairy cows. In: Proc. of the SALHC, Champagne Sports Resort, KZN, 5-7 June 2017.