Changes in animal performance and profitability of Holstein dairy operations after introduction of crossbreeding with Montbéliarde, Normande, and Scandinavian Red.

An individual-based mechanistic, stochastic, and dynamic simulation model was developed to assess economic effects resulting from changes in performance for milk yield and solid contents, reproduction, health, and replacement, induced by the introduction of crossbreeding in Holstein dairy operations. Three crossbreeding schemes, Holstein × Montbéliarde, Holstein × Montbéliarde × Normande, and Holstein × Montbéliarde × Scandinavian Red, were implemented in Holstein dairy operations and compared with Holstein pure breeding. Sires were selected based on their estimated breeding value for milk. Two initial operations were simulated according to the prevalence (average or high) of reproductive and health disorders in the lactating herd. Evolution of operations was simulated during 15 yr under 2 alternative managerial goals (constant number of cows or constant volume of milk sold). After 15 yr, breed percentages reached equilibrium for the 2-breed but not for the 3-breed schemes. After 5 yr of simulation, all 3 crossbreeding schemes reduced average milk yield per cow-year compared with the pure Holstein scheme. Changes in other animal performance (milk solid contents, reproduction, udder health, and longevity) were always in favor of crossbreeding schemes. Under an objective of constant number of cows, margin over variable costs in average discounted value over the 15 yr of simulation was slightly increased by crossbreeding schemes, with an average prevalence of disorders up to €32/cow-year. In operations with a high prevalence of disorders, crossbreeding schemes increased the margin over variable costs up to €91/cow-year. Under an objective of constant volume of milk sold, crossbreeding schemes improved margin over variable costs up to €10/1,000L (corresponding to around €96/cow-year) for average prevalence of disorders, and up to €13/1,000L (corresponding to around €117/cow-year) for high prevalence of disorders. Under an objective of constant number of cows, an unfavorable pricing context (milk price vs. concentrates price) increased slightly crossbreeding positive effects on margin over variable costs. Under an objective of constant volume of milk, only very limited changes in differences of margins were found between the breeding schemes. Our results, obtained conditionally to the parameterization values used here, suggest that dairy crossbreeding should be considered as a relevant option for Holstein dairy operations with a production level until 9,000 kg/cow-year in France, and possibly in other countries.

Assessment of risk factors for culling dairy cows using logistic regression. Definition of outcome and explanatory variables.

The culling of dairy cows can occur either early or late during lactation. Furthermore, the farmers decision-making process is probably not identical for cows culled early in lactation and for cows culled later. Most of the studies investigating associations between diseases and culling were performed without considering the time of culling during lactation. The present study defines d 45 post partum as a threshold between early and late cullings, and proposes 2 lists of possible risk factors, whether cows were culled early or late during lactation.