Use of the Cornell Net Carbohydrate and Protein System and rumen-protected methionine to maintain milk production in cows receiving reduced protein diets

Twenty-two primiparous and forty-eight multiparous lactating Holstein cows were used in a production trial. Cows were randomly assigned to two treatments to assess the effects of formulating a lower crude protein (CP) diet using the Cornell Net Carbohydrate and Protein Model (CNCPS), which included rumen-protected methionine and a bypass protein on group feed intake, milk yield, milk composition and blood urea nitrogen (BUN) status. Those animals receiving the lower CP diet were able to maintain milk production (P > 0.05) and milk component yield (P > 0,05) when compared with the animals receiving the control diet Although no statistical analysis could be undertaken on the dry matter intake data, due to insufficient degrees of freedom, group intakes appeared to be similar. Multiparous cows were also observed with the cows receiving the diet supplemented with bypass methionine and bypass protein had significantly lower BUN levels when compared with the control cows. These results indicate that the CNCPS model can be used as a tool for formulating lower CP diets since cows receiving the bypass methionine and bypass protein were able to maintain milk production.