Interpretive Summary: Interaction between feed use efficiency and level of dietary crude protein on enteric methane emission and apparent nitrogen use efficiency with Norwegian Red dairy cows.
By: Surely Wallace
Changing dietary composition of feed may improve herd efficiency and reduce livestock greenhouse gas emissions. Therefore, finding ways to effectively reduce methane emissions is an important area of study. The authors of this September 2018 Journal of Animal Science article studied Norwegian Red dairy (NRD) cows and impacts of dietary crude protein (CP) intake on methane production. They hypothesized that higher gross feed use efficiency (FUE) animals would use nitrogen from dietary treatments to produce more milk, with less methane production and better dietary nitrogen use efficiency (NUE), compared to lower efficiency animals.
In this study, eight NRD cows previously categorized as high FUE (HEFF, n=4) or low FUE (LEFF, n=4) were selected. Efficiency was determined by calculating milk yield per kilogram of dry matter intake (DMI). Cows were housed in 4x4 Latin square pens and given one of 4 isocaloric dietary treatments over four periods, each lasting 28 days. Cows were fed ad lib with each treatment varying by dietary CP, as follows: 130, 145, 160, and 175 g/kg dry matter.
Although HEFF cows in this study had higher milk yield, lower methane emission intensity (methane production in grams per kg of milk produced), and lower urinary nitrogen excretion than LEFF cows, the authors reported no significant interaction between dietary CP levels and high/low FUE cows on methane emission or methane intensity.
This small study suggests that selecting for HEFF cows may be an important factor in determining how to best reduce enteric methane emissions. Considering the study size (8 cows total), larger studies looking at the potential impacts of not only dietary CP, but potentially other dietary factors that may effect efficiency, rumen gut fermentation and/or DMI should be considered. This could include other macronutrients e.g. fat or carbohydrates, crude fiber, prebiotics, probiotics, or phytochemicals.
To view the full article, “Interaction between feed use efficiency and level of dietary crude protein on enteric methane emission and apparent nitrogen use efficiency with Norwegian Red dairy cows,” visit the Journal of Animal Science (https://academic.oup.com/jas/article/96/9/3967/5045195).