The impact of different management systems on behaviour and milk production of dairy ewes in different stages of lactation: a case study

Comparisons of New Zealand dairy sheep farm systems are currently lacking. The aim of this preliminary study was to evaluate the effects of different management systems on the behaviour and milk production of East Friesian cross-bred sheep at different stages of lactation. Two study groups were evaluated. In study group 1, a mob of 479 mixed-age, mid-lactation ewes were housed 24 h/day, and a separate mob of 473 mixed-age, mid-lactation ewes were managed in a hybrid system (housed between morning and afternoon milkings; grazed lucerne overnight). Both received a total mixed ration (TMR) indoors. In study group 2, a mob of 604 mixed-age, late-lactation ewes grazed pasture 24 h/day, and a separate mob of 452 mixed-age late-lactation ewes were in a hybrid system, grazing pasture overnight. For both study groups, individual milk yield, walking distance, lying time, live weight (LW), and body condition score (BCS) were recorded. All sheep gained BCS and LW except fully grazed late-lactation ewes. For study group 1, fully housed ewes in mid-lactation lay down less during the day, but more overnight compared to those in the hybrid system, likely due to the latter grazing overnight. Lying bout times were similar between groups, while milk yield was 29% less in housed ewes compared to the hybrid ewes. For study group 2, grazing ewes in late-lactation lay down more, had longer lying bouts, and walked further daily than those in the hybrid system, but both late-lactation treatment groups had similar milk yields. In summary, the hybrid management system seems to improve milk yield in mid-lactation compared to the fully housed system, whereas there was no difference between the hybrid and fully grazed systems in late-lactation. Lying behaviour and walking distances (group 2 only) differed among different systems, however, it is unclear what this means in terms of animal welfare, and warrants further investigation.