Effect of ruminal mechanical stimulating brushes on rumen fermentation and plasma oxidative stress and subsequent milk yield and composition in lactating dairy cattle

The objective of this study was to investigate the effect of ruminal mechanical stimulating brushes (RMS brush) on rumen fermentation and plasma oxidative stress and subsequent milk production in early lactation dairy cattle in the Australian spring and summer. Two hundred pasture-fed Holstein, Jersey, and Holstein × Jersey multiparous cows were enrolled into Control (no treatment; n = 103) or RMS brush (n = 97) groups in a randomised controlled trial at 26 ± 15 days before calving. The RMS brush group had three brushes/cow administered orally. Each RMS brush consisted of synthetic polymer bristles held in place with a metal component and was enclosed in a paper capsule that dissolved after insertion. Milk yield (MY), bodyweight, and weather data were recorded daily for the first 30 weeks of lactation. Stomach tube rumen fluid samples and plasma were collected monthly for the first 3 months of lactation from a minimum subset of 14 cows from each group. A total of 182 cows calved successfully and 34 cows were removed during the first 30 weeks of lactation. There was no difference in survival between the groups (hazard ratio = 0.952, confidence interval = 0.481–1.88). Rumen, plasma oxidative stress, and milk production measures were not affected by group or the interaction between group and time, with the exception of a mean increase of 304 µM of biological antioxidant potential in the RMS brush cows. The mean temperature humidity index for the first 30 weeks of lactation was