THE EFFECT OF TYPE OF SILO AND FORMIC ACID PRESERVATION ON THE NUTRITIVE VALUE OF BARLEY, WHEAT AND OAT SILAGES FOR GROWING HEREFORD STEERS

Two experiments with growing Hereford steers were conducted to evaluate four varieties of cereals preserved as plain silage, formic-acid-treated silage or ground and pelleted field-cured forage; and to compare farm-scale bunker silos with experimental, 1.1-m diam. steel culvert silos. In the first experiment, Bonanza barley, Glenlea and Wascana wheats, and Fraser oats were harvested at the mid-dough stage and stored as whole plant silage in steel culvert silos or were field-dried, baled and subsequently hammer-milled and pelleted. Bonanza barley, Wascana durum and Glenlea wheat silages had similar energy and protein digestibilities, while Fraser oat silages had less. Grinding and pelleting of the sun-cured cereal forages reduced digestibility by 9% but increased voluntary intakes of dry matter and digestible energy by over 40% and 25%, respectively. Grinding and pelleting removed almost all variation in intake due to cultivars. The addition of formic acid resulted in lower maximum silo temperatures, lower pH and increased nutrient recoveries from the silos. However, cereal silages treated with formic acid did not have significantly different nutrient digestibilities compared with the untreated silages. In the second experiment, Bonanza barley, Wascana wheat and Fraser oats were ensiled in steel culvert experimental silos or in 100-tonne capacity wooden bunker silos. These six silages were each fed to four 200-kg steers. As in exp. 1, Fraser oat silages had significantly lower protein and energy digestibilities; however, Fraser oat silages also had the highest dry mater intakes resulting in equal digestible energy intakes for the three cultivars of silage. Differences between silo types in digestibility and intake were not significant. There was a lower crude protein digestibility of Wascana wheat silage stored in a bunker silo, which was probably due to the high temperature in the Wascana bunker silo which may be attributed to its low moisture content. It was concluded, however, that the experimental silos were useful for purposes of silage evaluation and would produce silage similar to good quality farm-produced silage. Key words: Cattle, cereal silage, formic acid, silo type