Nutritional evaluation of wet brewers’ grains as substitute for common vetch in ensiled total mixed ration

Abstract

The interest of ensiling total mixed ration for ruminants re-emerged in the last decades. In many situations, ensiled total mixed ration (ETMR) has been a sustainable alternative to efficiently handle wet by-products in ruminant diets. The purpose of this study was to assess the effect of replacing common vetch with wet brewers’ grains (WBG) at different proportions on the fermentation quality, nutritive value, aerobic stability, in vitro gas production kinetics and digestibility of ETMR. Four ETMR formulations were designed according to the varied ratios on fresh weight basis: (i) 45% common vetch (Control); (ii) 35% common vetch +10% WBG; (iii) 25% common vetch +20% WBG; (iv) 15% common vetch +30% WBG. The laboratory silos (10 L) were opened after 70 days of ensiling, then the 70-day silages were subjected to aerobic stability for 14 days and changes in ETMR temperature were recorded. Replacing common vetch with WBG linearly increased the ratio of lactic acid to acetic acid, ethanol, water soluble carbohydrate contents and dry matter recovery, and decreased pH, volatile fatty acids and ammonia nitrogen contents. When exposed to air, no ETMR deteriorated and their temperature appeared stable during the 14 days test. With the WBG levels increasing, the organic matter digestibility, metabolisable energy, 72-h net gas production and the average gas production rate were linearly decreased, whereas no obvious differences were observed among the control, 10% and 20% WBG silages. Therefore, 20% WBG can be used effectively in ETMR, reducing the need for common vetch without negative effects. Highlights Ensiling total mixed ration is a good way to use wet brewers’ grains Reducing the need for legume and feed cost 20% wet brewers’ grains replacement had no adverse effect on in vitro gas production kinetics and digestibility