TIMOTHY GRASS OR ALFALFA SILAGE FOR COWS IN MIDLACTATION - EFFECT OF SUPPLEMENTARY BARLEY

Twenty-four multiparous Holstein cows averaging 104 d of lactation wer e used in a trial with a split-plot design to evaluate the nutritive v alue of two silages, timothy grass or alfalfa, both treated with formi c acid and stored in plastic bag silos. Silages were offered for ad li bitum intake either alone or with 17 or 34% (dry matter basis) dry-rol led barley. Both silages contained similar amounts of acid detergent f iber (ADF) (27.5 and 26.7% for timothy grass and alfalfa, respectively ). After 110 d of storage, alfalfa silage contained higher amounts of organic acids and NH3 N but had lower soluble N. Total dry matter inta ke (DMI) and silage DMI were similar between cows fed both silages. In creased barley proportion decreased silage DMI (19.2 to 14.2 kg/d). Ap parent total tract digestibility of dry matter was unaffected by treat ment. The digestibility of neutral detergent fiber and ADF was higher for the timothy grass silage than for alfalfa silage and was unaffecte d by the barley percentage added to either silage. Milk yield was lowe r (23.9 to 22.6 kg/d) for cows fed the highest proportion of barley. T he 4% fat-corrected milk yield was unaffected by treatment. Percentage s of fat, protein, and total solids in milk were higher for cows fed d iets with the higher barley content. Milk fat and protein yields were similar among treatments. Urea in blood was lower for cows fed timothy grass silage than for cows fed alfalfa silage (4.68 vs. 6.23 mg/100 m l). These results suggest that timothy grass silage and alfalfa silage , when stored at a similar ADF content, have comparable nutritive valu e for midlactation cows.