Abstract/Summary

Background: Wheat distillers’ grains (WDG) and seaweeds are recommended as alternative protein sources and enteric methane mitigators in dairy cow diets, respectively, but little is known about their impact on milk quality and safety. In the present study, 16 cows in four 4×4 latin squares were fed iso-nitrogenous diets (50:50 forage:concentrate ratio), with rapeseed meal (RSM)-based or WDG-based concentrate (230 and 205 g kg-1 DM) and supplemented with or without Saccharina latissima. Results: Replacement of RSM with WDG enhanced milk nutritional profile by decreasing milk atherogenicity (P=0.002) and thrombogenicity (P=0.019) indices and the concentrations of the nutritionally undesirable saturated fatty acids, specifically lauric (P=0.045), myristic (P=0.022) and palmitic (P=0.007) acids. It also increased milk concentrations of the nutritionally beneficial vaccenic (P<0.001), oleic (P=0.030), linoleic (P<0.001), rumenic (P<0.001), α-linolenic (P=0.012) acids and total monounsaturated (P=0.044), polyunsaturated (P<0.001), and n-6 (P<0.001) fatty acids. Feeding Saccharina latissima at 35.7 g/cow/d did not affect the nutritionally relevant milk fatty acids or pose any risk on milk safety, as bromoform concentrations in milk were negligible and unaffected by the dietary treatments. It however slightly reduced milk concentrations of pantothenate. Conclusion: Feeding WDG to dairy cows improved the milk FA profiles, by increasing the concentrations of the nutritionally beneficial fatty acids and reducing the concentration of the nutritionally undesirable saturated fatty acids; while feeding seaweed slightly reduced pantothenate concentrations. However, when considering the current average milk intakes in the population, the milk compositional differences between treatments in this study appear relatively small to affect human health.