Document Type : Original Research Article (Regular Paper)
Department of Animal Science, College of Agriculture, Isfahan University of Technology, 84156–83111, Isfahan, Iran.
This study assessed the substitution effects of barley silage (BS) for corn silage (CS) on nutrient utilization, feeding behavior, and performance of dairy cows. Eight Holstein lactating cows were used in a replicated 4 × 4 Latin square design, and the cows were offered diets containing different ratios of CS to BS (22% of DM) as 1) 3:0 (CS3BS0); 2) 2:1 (CS2BS1); 3) 1:2 (CS1BS2); and 4) 0:3 (CS0BS3). The diets were iso-energetic and iso-nitrogenous, but the dietary concentration of indigestible neutral detergent fiber (iNDF) and proportion of long particles (>19 mm) were increased with increasing BS proportion in the diets. The degradability characteristics of the silages were evaluated by in situ technique. Both silages were similar in predicted total tract NDF digestibility (TTNDFD = 35 %), 30-h undegradable NDF (uNDF30h = 32 %), NDF digestion rate (kd = 1.8 %/h), but CS was lower in iNDF and higher non fibrous carbohydrates (NFC). Intake of DM was unchanged, but NDF intake was linearly increased with increasing BS levels. Total tract NDF digestibility did not differ among treatments, but DM digestibility linearly decreased with increasing BS proportion. Feeding different ratios of CS: BS did not affect milk yield or milk fat and protein concentration. Furthermore, ruminating time was unaffected by dietary treatments but increasing BS level decreased quadratically the eating and total chewing times. The experimental treatments did not affect plasma β-hydroxybutyric acid and glucose concentrations, but BS increased linearly ruminal ammonia and blood urea nitrogen concentration. The results indicated that BS had a higher iNDF content and a negative impact on DM digestibility and N utilization. However, partial or total substitution of CS with BS led to similar DM intake and milk yield, possibly as a result of similar fiber digestion rate and uNDF30h.