Improving the nutritive value of whole-crop wheat for dairy cows

Jackson, Marie Ann (2005). Improving the nutritive value of whole-crop wheat for dairy cows. PhD thesis The Open University.



A series of experiments was carried out to investigate ways of improving the nutritive value of whole-crop wheat (WCW) for dairy cows. Experiment One examined the effects of mechanical processing and alteration of forage cutting height at harvest. Digestibility was improved when urea-treated WCW was mechanically processed at harvest with no effect on milk yield and composition. Increasing forage cutting height decreased dry matter intake (kg/day), increased condition score and reduced milk fat content. Experiment Two investigated the effects of carbohydrate supplementation to mechanically processed urea-treated WCW and included a comparison between maize silage and mechanically processed urea-treated WCW. Cows fed lactose supplemented WCW had numerically higher milk yields than those supplemented with wheat or molasses with no effect on milk component yield (kg/day). Dairy cows fed mechanically processed urea-treated WCW and maize silage performed similarly but animals fed WCW ate proportionally 0.24 more than those fed maize. Experiment Three comprised two parts; the first examining the effects of form of urea applied at ensiling at two stages of maturity. All forages harvested at 550 g DM/kg (except those receiving the urea + urease additive), fermented, indicated by their low pH (< 4.5). At 800 g DM/kg all forms of urea were released resulting in an alkaline pH. Part two of the experiment examined the effects of three stages of maturity and additive treatment to WCW. All forages were aerobically stable with additive application reducing microbial numbers. Additive application is necessary at dry matter contents of 600-700 g DM/kg to prevent microbial growth and additional urease is required at ensiling to promote rapid, extensive hydrolysis of urea and an enhanced NDF digestibility. The production of high DM urea-treated WCW without a reduction in starch digestibility is now possible through the use of mechanical processing. There is also potential to improve performance through the development of appropriate supplementation strategies.

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