Performance of Dairy Cows Offered Grass Silage Produced within Either a Three- or Four-Harvest System When Supplemented with Concentrates on a Feed-to-Yield Basis

SIMPLE SUMMARY: Harvesting grass for silage at an earlier growth stage can improve silage quality and subsequent dairy cow performance. This study investigated the impact of more frequent harvesting of grass for silage production on dairy cow performance in a system offering concentrates on a feed-to-yield basis. Grass silage was harvested either three- (3H) or four- (4H) times during the summer and then offered to lactating cows for 25 weeks post-calving. Cows were offered their respective silage treatment as part of a mixed ration containing 8 kg of concentrate per cow per day. Cows were also offered additional concentrate on a feed-to-yield basis according to individual cow milk yields. The silage produced under 4H had higher energy and protein content than silage harvested within the traditional 3H system. The increase in silage quality with 4H resulted in an increase in silage intake, milk yield and milk protein content. This study has demonstrated that increasing silage harvesting frequency can improve silage quality and subsequent animal performance. ABSTRACT: More frequent harvesting of grass swards provides an opportunity to improve the nutritive value of grass silage. This study investigated the effect of offering silages produced within either a three- (3H) or four-harvest (4H) system on dairy cow performance when concentrate supplements were offered according to the individual cow’s milk yield (feed-to-yield). Cows (n = 80) were allocated to either 3H or 4H at calving and remained on experiment for 25 weeks. Within both treatments, cows were offered silage from each harvest consecutively in proportion to the dry matter (DM) yield for each harvest. Silage was offered as a mixed ration with concentrate added at a rate of 8 kg/cow/day. Additional concentrates were offered on a feed-to-yield basis. Herbage yields were reduced in the 4H system, but 4H silage contained higher metabolisable energy and crude protein content compared to 3H. Cows offered the 4H silage had greater silage DM intake, milk yield and milk protein content, while milk fat content was greater in cows offered 3H silages. In conclusion, increasing harvesting frequency from three to four harvests per year can improve silage feed value, silage intakes and milk yields when concentrates are offered on a feed-to-yield basis.