Evaluating rations offered to a group of cattle as a component of ration formulation software

Abstract Text: Rations are typically formulated for a target cow representing a group of cows. Lead factors may be used to select the target milk production for the group. Body weight, lactation number and milk composition are chosen based on mean values for the group of cows to be offered the ration. It is often not known how the offered ration impacts the ME and MP across all cows in the group. To provide an assessment of ME and MP balance for a ration fed to a group of cows, the UPenn Ration Analyzer incorporated a group model within its software program. Records from DHIA milk production (more than 1,000,000)  from  2,000 farms and five breeds were used to construct production curves based on rolling herd averages (RHA) for parities 1, 2, and 3+. The user inputs breed, lactation number, the mean BW for parities 1, 2, 3, 4+, the range in DIM for the group, and the herd RHA. The group model constructs a production profile of cows based on the user inputs and assigns stochastic variation to production and DIM for the group. Intake of DM for each cow in the group is predicted using the NRC. The ME and MP balance for each cow in the group is calculated based on the formulated diet and plotted by DIM. The user can view graphs of the predicted range in milk production, ME and MP balance by DIM and a table with mean DMI, milk volume, and fat, protein content for the group. The user can adjust the scale of the variance in milk production, the mean milk production, DMI, and fat and protein content if the actual values in the herd differ from predicted. A second model allows imported DHIA milk production records for the group to be fed the formulated diet to compare with the model predicted values. A third model allows the user to least cost the diet for the group within constraints on ME and MP balance for the group of cows. The user can reformulate the ration to better meet the ME and MP needs of the group. Preliminary validation from farms suggests that the group evaluator model provides a useful tool for regrouping cows and evaluating rations for improved ME and MP balances, particularly avoiding excesses in MP.     

Keywords: Ration Formulation, Production, Cattle Groups