Replacing silage with large amounts of concentrate and straw affects milk production, economics and climate differently in Holstein and Jersey Cows

Abstract

With droughts becoming more frequent due to climate changes alternative feeding strategies are required. The aim of this study was to examine the effects of replacing all or part of the silage component with barley straw and concentrates for Holstein and Jersey cows. Forty-nine Holstein and 43 Jersey cows were fed either the C49 diet (Roughage-to-concentrate ratio [% of DM; dry matter] of 51:49), a diet where concentrate constituted 70% of DM (i.e., diet C70; 30:70), or the extreme diet (i.e., C91; 9:91), where 91% of DM was concentrate and 9% of DM was barley straw. Cows were allowed up to 2.65 kg DM per day from concentrate in the automatic milking system (AMS). Cows were fed their diets for 5 weeks. All diets were formulated to provide the same daily net energy intake. Daily feed intake and milk production responses were recorded. Volatile fatty acid profiles in rumen fluid were measured for Holstein cows. Impact on economy and carbon footprint were calculated. Data were analyzed using a general linear mixed model. For both breeds, total dry matter intake (i.e., AMS concentrate + partially mixed ration) decreased with increasing concentrate proportion. In neither Holstein nor Jersey, experimental diet affected milk yield. A decrease in fat percentage and ECM was observed for both breeds, when the level of concentrate was increased. However, there was an interaction between diet and breed for fat percentage and for energy-corrected milk yield (ECM), and there was an interaction for feed efficiency expressed as kg of ECM/kg of DM intake. For Holstein cows, acetate molar proportion in rumen liquid decreased and propionate molar proportion increased when silage was reduced. Regardless of breed, increasing concentrate in the ration did not affect carbon footprint per kg ECM, but caused a decrease per cow per day, and per kg DM intake. However, if the contribution from direct land use changes and soil C were taken into account, increasing concentrate in the ration reduced carbon footprint per kg ECM due to decreased proportion of soybean meal in C75 and C91 diets. Production of milk from predominantly concentrate based diets containing no grass silage reduced income over feed cost for both breeds but more for Holsteins. In conclusion, results showed that it is possible to keep dairy herds and produce milk even during extreme drought, when availability of silage is minimal, whereas such ration decreased income over feed cost.