Digestibility and performance of feeder lambs fed mixed barley grain–barley silage diets with varieties of barley silage selected on the basis of in vitro neutral detergent fibre degradability

Barley silage varieties ranked based on in vitro neutral detergent fibre digestibility (NDFD) of commercial silage samples were designated as high-NDFD (H-NDFD, 'CDC Cowboy'), intermediate-NDFD (I-NDFD, 'CDC Copeland'), and low-NDFD (L-NDFD, 'Xena') and assessed in digestibility and lamb performance experiments. A replicated 3 x 3 Latin square digestibility experiment fed 50:50 silage:concentrate diets [dry matter (DM) basis] to nine rumen fistulated wethers. A growth study used 42 lambs fed 40:60 silage: concentrate diets (DM basis) with carcass traits being assessed in 21 ram lambs. In vitro NDFD of silages did not coincide with the ranking of field silage samples. Intake and digestibility in wethers did not differ (P > 0.05) among varieties. Mean rumen pH was lower (P > 0.05) for wethers fed L-NDFD than H-NDFD, with rumen pH of wethers fed L-NDFD spending more (P < 0.01) time below 6.2, 6.0, and 5.8. Growing lambs fed L-NDFD had lower (P < 0.01) dry matter intake (DMI) than lambs fed I-NDFD. Dressing percentage was higher (P < 0.05) for ram lambs fed L-NDFD than I-NDFD. Selecting barley silage varieties based on improved in vitro NDFD to improve digestibility and lamb performance is difficult due to yearly differences in forage growing conditions and ensiling dynamics.