Simulating consequences of choosing a breeding goal for organic dairy production

Summary

Six different breeding goal (BG) scenarios were developed and simulated for organic and conventional dairy production, to study the effect on genetic change for specific traits. The first two BGs (BG1 and BG2) were based on economic weights from SimHerd simulations for a conventional and an organic dairy system in Denmark. The third BG (BG3) was based on weights derived from a farmer preference survey for organic farmers. The fourth BG (BG4) was based on the four organic principles defined by the IFOAM, and on the results of a questionnaire that was sent out to farmers, researchers and experts in the area of organic dairy husbandry. The fifth and sixth BGs (BG5 and BG6) were based on BG4, but altered to put more emphasis on roughage consumption and disease resistance, respectively. Each BG was simulated for 30 years using a stochastic simulation. A genomic breeding scheme using 100 young bulls yearly were simulated. Animals were selected based on a total merit index, including all 12 traits with different economic weights per scenario. The best animals were selected for breeding. Preliminary results show that some overall genetic gain in monetary units is lost when using BG3 (based on organic farmers’ preferences) compared to using BG1 and BG2 (based on objectively derived economic weights). BG3 caused the least genetic decline in genetic standard deviation units in beef production, calving difficulty, cow and heifer fertility and cow mortality, but also the least genetic progress in genetic standard deviation units in milk production, roughage consumption and feed efficiency compared to BG1 and BG2.