Whole-crop wheat for dairy cows: effects of crop maturity, a silage inoculant and an enzyme added before feeding on food intake and digestibility and milk production

Abstract

AbstractTo measure the effect of stage of maturity of whole-crop (WCW) on its composition, digestibility and feeding value winter wheat was harvested at different maturities in two successive years. In year 1 WCW was harvested at 301(low dry matter (DM)) and 511(high DM) g DM per kg and ensiled and at 584 g DM per kg and treated with 40 kg urea per t DM before being stored (urea-treated WCW). Part of the high DM WCW was treated with an additive containing Lactobacillus buchneri at harvest. In year 2 WCW was harvested at 321 (low DM) and 496 (high DM) g DM per kg and ensiled before both crops were offered to the cows with or without a fibrolytic enzyme sprayed on the forage just before feeding. In both years the WCW was offered ad libitum in a 2: 1 WCW: grass silage DM ratio with 10 kg fresh weight concentrates per day to 40 early-lactation Holstein-Friesian cows in a 13-or 15-week production study with a continuous design and to four fistulated lactating cows in a 4 ✕ 4 Latin-square experiment for measurement of diet digestibility. In both years neutral-detergent fibre (NDF) content decreased and starch content increased with advancing maturity. In the production trials, DM intake increased (P 0·01) with advancing maturity but milk yield was not significantly affected. Milk protein yield was increased by urea-treated WCW. The additives had no effect on food intake or milk production. In year 1, digestibility of all fractions except starch was lower for high DM WCW than low DM WCW but for urea-treated WCW only the digestibility of starch and energy was lower than digestibility of the low DM WCW fractions. The inoculant had no significant effect. In year 2 crop maturity had no significant effect on digestibility but the enzyme reduced the digestibility of neutraland acid-detergent fibre (NDF and ADF, P 0·05). In year 1, each of the forage mixtures was offered to sheep at 12 g DM per kg live weight per day. There were significant treatment effects on the digestibility of DM (P 0·05) and organic matter (OM) (P 0·01) and on DOMD (digestible OM in the DM) (P 0·01) with the highest values being obtained for urea-treated WCW and the lowest for the inoculant-treated high DM WCW. Digestibility coefficients for NDF and ADF were highest for the urea-treated WCW while starch digestibility was essentially complete for all the WCW treatments. The metabolizable energy value (MJ/kg corrected DM) of the WCW decreased with advancing maturity when measured with both the lactating cows (10·4, 9·3 and 9·0) and the sheep (11·4, 10·8 and 10·3) in contrast to the predictions based on the chemical composition (9·6, 10·4 and 12·4). It is concluded that food intake increases with advancing crop maturity but milk production responses are small. Effects on digestibility were inconsistent but the energy value measured in the cows fell with advancing maturity in both years. The increase in crop yield per ha with advancing maturity is likely to be the most important factor influencing the decision to harvest later. The silage additives tested were not beneficial.