Effects of grazing on welfare and production traits of organic dairy cows

Abstract

In organic livestock systems, grazing is the preferred feeding source, especially for animal welfare and health implications, but it is not an obliged practice. In order to contribute on this topic, in an organic dairy farm, grazing was compared with permanent free-stall housing using two homogeneous groups of eight Bruna cows allocated to the following regimes: (G) grazing on barley grass for 5 h/d, and then kept in a free-stall structure and fed with unifeed, composed of hay and concentrate; (S) kept in a free-stall building for 24 h/d and fed with a diet based on the same unifeed. Comparison was based on milk production, behaviour, immune responses, metabolic status and oxidative stress of animals, observed 4 times during a 64-day period. Grazing barley pasture did not affect milk yield, whereas led to an improvement in milk quality in terms of fat increase and reduction in urea, somatic cells count and total microbial count. Regarding behaviour, S cows spent more time inactive, whereas G cows better interacted socially, devoting more time to sniff, lick or rub between them in non-aggressive forms, thus giving indications of their higher level of comfort and relax. The skin test, performed with PHA at the end of trial, resulted in a higher skin thickness in cows G, index of a better immune response, than S cows. The regime had an effect on Oxidative Stress (OS), since G group exhibited higher ROMs and lower BAP concentration than S group, indicating a moderate OS in G group as result of grazing activity, which can increase free radical production and decrease antioxidant capacity. However, in the first period of grazing, G group showed a higher content of polyphenols in plasma than S group. In both regimes, low NEFA and BHBA concentration indicates that cows did not display a state of metabolic stress. In conclusion, grazing of dairy cows in an organic farming system did not reduce milk yield and contributed to improve milk quality. Moreover, grazing would seem to induce a better welfare status and a more intense immune response in the cows.