The impact of field bean inclusion level in dairy cow diets on cow performance and nutrient utilisation

Within Europe field bean (Vicia Faba) (FB) has been identified as a crop with potential to partially replace imported protein feeds in dairy cow rations. The current study was designed to examine the impact of FB inclusion level in dairy cow diets on performance and nutrient utilisation. Sixty mid-lactation dairy cows were used in a four treatment continuous design (ten weeks duration) experiment. All cows were given ad libitum access to grass silage, and were supplemented with 10.0 kg concentrate/cow/day. Concentrates offered contained 0, 166, 333 or 473 g FB/kg concentrate (treatments FB0, FB1.7, FB3.3 and FB4.7, respectively), with the FB partially replacing soya bean meal and rapeseed meal. On completion of the 10 week experiment, ration digestibility was measured using four cows from each treatment.While there was a trend for milk protein content (linear: P = 0.081) to decrease with increasing FB inclusion levels, FB inclusion had no effect on silage dry matter (DM) intake, total DM intake, milk yield, milk fat content, milk fat yield, milk protein yield, milk fat + protein yield, live-weight change and body condition score change. Similarly, FB inclusion had no effect on DM, organic matter and gross energy digestibility coefficients, although there was a linear increase in nitrogen (N) digestibility (P < 0.041) with increasing FB inclusion levels. Faecal N/N intake (P < 0.042) and milk N/N intake (P < 0.047) decreased with FB inclusion, while energy utilisation was unaffected. Field bean inclusion had no effect on any of the methane production parameters measured. The results of this study demonstrate that FB can be included in dairy cow diets at levels up to 4.7 kg/day with few negative effects on cow performance, and as such may have potential to replace imported protein feeds in dairy cow diets. However, total diet crude protein levels were relatively high in this study, and different responses might have been observed if diet crude protein levels had been lower.