The development of plant components and their effects on the composition of fresh and ensiled forage maize: 3. The effect of grain content on milk production

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Abstract
Summary: Maize (Anjou 210), a density-sensitive genotype, was established at 5 and 15 plants/m2 and produced crops containing 50 and 26% grain respectively. Prior to ensiling, the high and low grain crops contained 6·9 and 20·4% water-soluble carbohydrates in the dry matter respectively and were reduced to 0·4 and 1·6% of the dry matter in the silage. The high grain silage contained a lower concentration of acid-detergent fibre, cellulose, lignin, cell-wall constituents and organic acids than the low grain silage. These differences were not reflected in the in vitro digestible organic matter in the dry matter values which were similar in both silages.Two groups of autumn-calving Freisian cows were offered either the high or low grain silage ad libitum as the sole forage plus an 18% crude protein concentrate during a 14-week experimental period. The cows which received the high grain silage produced significantly more milk of a significantly lower milk fat content than the cows which received the low grain silage.The increased milk production coupled with the smaller loss of water-soluble carbohydrates during ensiling show that a high grain content in forage maize is a desirable attribute. It is suggested that density tolerance should be one of the selection criteria used by plant breeders to allow crops to be established at high plant densities from which near maximum dry-matter yields could be obtained, while still containing a high proportion of grain.