A systems analysis of dual dairy and beef production herds

Abstract

The milk and beef offtake of a herd of Colombia's North coast was predicted by simulation with the Texas A&M Cattle Production System Model. Basic response surfaces were established for genetic potentials of milk yield of 6, 9, 12, 15 and 18 kg/day at the peak of milk yield curve and each of four extractions of milk for sale of 0, 25, 50 and 75% of the actual yield. The optimal level of potential milk yield and milk extraction for sale was evaluated in terms of milk equivalents. The sensitivity of the response surface to changes in genetic potential for mature weight and changes in feeding during the dry season was studied. In general, an increase in genotype for milk yield increased the milk equivalents up to 33.3% within a given level of milk extraction. The milk extraction rate increased the milk equivalents up to 17.6% in the highest level of milk potential and decreased them to 15.3% for the lowest level of potential milk yield indicating that the optimal level of potential milk yield was in the range of 12 to 15 kg and the optimal milk extraction rate was approximately 50%. This conclusion was valid for a ratio of prices of beef to milk of 6, 8 and 10 used to calculate the milk equivalents. Adjustment of the milk equivalents to an equal grazing pressure changed the optimum level of milk potential to 18 kg. An increase of mature weight of cattle from the 432 kg, used to establish the basic response surface, to 480 kg decreased the milk equivalents slightly. The absolute response was more sensitive to lower values of the digestibility and crude protein of the dry matter than to high values of these parameters. The relative ranking of the potential milk yield and milk extraction remained the same. Milking the herd has to be limited to cows that have a moderate milking potential and the effect of this may be marginal when the price of beef to milk is high. For price ratios of beef to milk lower than 6, milking can be practiced gainfully. The optimal level of milk extraction increases to approximately 75% for price ratios of 4 and 2. Additional simulations are required for economic conditions where the price ratio is below 5 in order to gain further precision in determining optimal potential milk production and milk extraction...