Supplementation strategies for lactating dairy cows offered very high quality grass silages: Starch-based or fibre-based concentrates offered with or without straw

摘要

A three-period change-over design study using 24 mid-lactation multiparous Holstein-Friesian dairy cows, examined supplementation strategies for a high quality grass silage (dry matter (DM), 418 g/kg; crude protein (CP), 170 g/kg DM; metabolisable energy (ME), 12.1 MJ/kg DM). Four treatments, in a 2 x 2 factorial arrangement, compared concentrate type (High-starch or High-fibre) and straw inclusion (Straw or No-straw). Concentrates had a starch and neutral detergent fibre content of 373 and 258 g/kg DM, respectively (Highstarch), and 237 and 339 g/kg DM, respectively (High-fibre). In the No-straw treatments, silage and concentrates were offered as a total mixed ration in a 57:43 DM ratio. In the Straw treatments, chopped straw was added at 4% of total DM, replacing part of the silage component of the diet. Following this study, the effect of diet on nutrient utilisation efficiency was examined using four cows/treatment. There were no interactions between concentrate type and straw inclusion for any cow performance or digestibility parameters. Silage dry matter intake (DMI) and total DMI were reduced with the High-fibre concentrate (P = 0.001 and P = 0.006, respectively) and straw inclusion (P < 0.001 and P = 0.014, respectively). Neither concentrate type nor straw inclusion had a significant effect on milk yield or milk fat content. The High-starch concentrate increased milk protein content (P < 0.001), while straw inclusion decreased milk protein content (P = 0.036). Treatment had no effect on cow body weight, condition score, faecal scores, digestibility coefficients or nitrogen and energy utilisation efficiency. In conclusion, supplementing a high quality grass silage with a carefully formulated `high starch' concentrate improved DMI and milk protein content with no adverse effects on cow performance. Straw inclusion in the diet had no beneficial effects on DMI, milk production or nutrient utilisation efficiency.