Breed and management interaction for production and reproduction in Swedish dairy cows

The effects of grazing during summer and possible interaction effects betwe en breed and management system on milk production and postpartum reproducti ve performance were studied in 93 Swedish Red and White (SRB), Swedish Hols tein (SLB) and Swedish Jersey (SJB) cows with 214 initiated lactations. The cows were divided into two groups: zero-grazing with tiestalls, or grazing during summer. Effects were studied by mixed-model analysis. The results i ndicated that grazing (rather than zero-grazing) can reduce the milk yield in the following lactation in SLB cows, whereas it had little effect on the production of SRB cows. Grazing SJB cows produced more milk, but with a si gnificantly lower fat content. Grazing before or during the postpartum peri od stimulated reproductive performance, indicating a higher conception rate in all breeds and a 13-27-day shorter interval from calving to conception in the SRB and SLB cows, whereas in the limited number of SJB cows, the tre nd was the converse.