Milk production from diets of silage and dried forage. 2. Effect of ensiling ryegrass cut at two levels of digestibility and given ad libitum with supplements of dried grass pellets

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Abstract
SUMMARY: 1. Young adult and adult British Friesian female cattle (heifers and cows) which were lactating were individually fed ad libitum on ryegrass silage of high (HS) or low (LS) digestibility with one of two levels of a supplement of pellets of dried grass (H or L) in a 2 × 2 factorial experiment with three heifer and seven cow replicates.2. The percentages of digestible organic matters in the dry matter (DM) in vitro were respectively 64·4, 57·5 and 69·0 for forages HS, LS and and the dried grass. The HS crop, however, was significantly lower in DM content, and after ensiling with formic acid additive had a higher lactic and total acid content than the LS crop.3. The dry-matter intake of the less acid silage LS was greater than that of HS (P<0·05) although the dry-matter digestibility of the LS diets was on average 6 units lower than the HS diets. The intakes of digestible dry matter (DDM) and digestible organic matter were greater (P<0·05) in mid lactation when HS was fed. DM and DDM intakes were significantly increased by the higher level of feeding of the dried grass supplement.4. The yield, composition and energy content of milk did not differ between silages but the yield and protein content of the milk increased significantly at the higher level of supplement feeding. The milk yields were respectively 19·35, 17·54, 19·49 and 17·97 ± 0·505 kg/head per day for treatments HSH, HSL, LSH and LSL on these all-grass diets over lactation weeks 4 to 20. Live-weight loss was greater (P<0·01) on the LS diets. Blood composition was normal and did not differ markedly between treatments.