VFA are produced are influenced by several factors, including substrate composition, substrate availability and degradabil- ity, and microbial species present. Interactions between these factors may hamper conclusions with respect to the ef- fect of a single factor. In this study, the total VFA concentra- tion and fermentation pattern were not affected by in- creased inclusion of oats in the diet. But the researchers expected a difference in VFA production since the OM digest- ibility between barley and oats differed. “However, given the relatively high standard error of the mean in the current study, it is likely that the means for total VFA concentration are not fully accurate. Once-a-day sampling method with a stomach tube can increase random variation in the data due to salivary contamination and time elapsed after the last meal,” they concluded.
Milk production The researchers recorded a numerical increase in milk yield and ECM/DMI ratio following complete substitution of barley with oats. However, the yield of milk constituents was not sig- nificantly affected by the gradual replacement of barley with oats in the diet. They attributed the increase in milk yield to the increase in dietary fat concentration when barley is re- placed by oats in the diet, which probably provides additional DE for the animal. “Compared with barley-based diets, the increase or maintenance of milk yield by dairy cows on
oat-based diets could be the result of differences in energy partitioning, whereby less energy is partitioned into body fat reserves, as we observed in our study,” they said.
Digestibility and energy utilisation Digestibility of OM, NDF, and potentially digestible NDF de- creased linearly with increasing inclusion of oats. This resulted in a linear decrease in ME intake. However, increased levels of oat in the diet did not significantly affect the energy balance or the efficiency of ME utilisation for lactation. The researchers mentioned that similar production despite lower ME intake may suggest that incremental energy supply from barley fa- voured body fat production instead of milk production, or that cows mobilise body fat to support milk production when oats are fully included in the diet.
What could cause differences? This study concludes that replacing barley with oats in the diet of dairy cows fed a grass silage-based diet could be used as a sustainable strategy which can easily be adopted by farmers to mitigate enteric CH4
emissions without compromising animal
performance. They also highlighted the fact that differences in methane emissions and milk production could be expected due to differences in silage to concentrate ratio, the level of inclusion of oats and barley in the concentrate fraction, and silage type and quality.
▶ ALL ABOUT FEED | Volume 29, No. 7, 2021 13
The study shows that replacing barley with oats in the diet of dairy cows fed a grass silage- based diet can be used to miti-
gate enteric CH4 emissions.
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