Increasing concentrations of low SMCO swedes in the diet of dairy cows improves performance and ruminal metabolism without affecting dairy cow health

This study aimed to determine dry matter intake, ruminal fermentation, health-related blood metabolites, and production responses of early-lactation dairy cows fed two inclusion levels (30 and 45 %) of low SMCO swedes in the diet. Twelve pregnant multiparous lactating Holstein-Friesian dairy cows (24.1 ± 0.72 kg milk/d, 540 ± 7.3 kg BW, and 142 ± 3.9 DIM at the start of the study) were used in this study. Cows were randomly allocated to three dietary treatments in a replicated 3 ×3 Latin square design. The experiment lasted 63 d and was divided into three 21-d periods. Inclusion of swedes at 30 and 45 % in the diet had no effect on DMI, but increased milk, protein and fat yields, as well as CP concentration in milk. This was due to changes in VFA patterns with greater molar proportions of propionate and butyrate, as well as a greater utilisation of dietary N that was converted to microbial N. No negative effects on haematological and biochemical blood parameters, except for increased BHB concentrations. Fatty acids composition in milk was modified, with a greater proportion of saturated FA and lower n-3 FA. Overall, low SMCO swedes can be included up to 45 % in the diet of pasture fed dairy cows during winter.