Digestion characteristics of forages, including perennial ryegrass at different stages of maturity, and supplementary feeding for dairy cows grazing pasture : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science, Institute of Food Nutrition and Human Health, Massey University, Palmerston North, New Zealand

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dc.contributor.authorChaves, Alexandre Vieira
dc.date2003
dc.date.accessioned2010-01-28T02:14:49Z
dc.date.available2010-01-28T02:14:49Z
dc.date.issued2003
dc.description.abstractThis thesis defines digestion kinetics for perennial ryegrass (Lolium perenne L.), which is the main component of diets fed to dairy cows in New Zealand. Chemical composition and digestion kinetics were measured in fresh minced ryegrass as it matured and leaf, stem and inflorescence of several grass species. In sacco and in vitro incubations were used to define rates of degradation and nutrient release. Two short-term grazing trials were used to evaluate contrasting silages as supplements for cows fed restricted amounts of summer pasture. The minced preparation of ryegrass resulted in a similar distribution of dry matter (DM) between particle size fraction and rumen digesta from cows fed pasture. Mincing released 0.46 – 0.80 of crude protein into the soluble fraction, with highest proportions for mature grasses which had low CP concentrations (about 8 g CP/100 g DM). In contrast, the majority of fibre remained in the insoluble fraction but rates of degradation (k) approximately halved as grass matured. In vitro yield of VFA was similar for immature and mature minced ryegrass (after 12 hours VFA was equivalent to about 30% of DM), even though ammonia concentration declined to very low values for stem and mature grass. This suggests the rapid initial microbial growth was able to sustain a high level of DM degradation to VFA with mature grass. The summer pasture used for silage supplementation was of uncharacteristically good quality so the expected contrasts between maize, pasture, sulla (Hedysarum coronarium), lotus (Lotus corniculatus) and sulla/maize silage mixtures were less than expected. Milk responses to lotus silage supplements were greater than other silages (e.g.: 290 g milksolids from 54 MJ ME by lotus versus 110 g milksolids from about 50 MJ ME supplied by other silages). Pasture substitution was low (0.06 – 0.33). The Cornell Net Carbohydrate and Protein System (CNCPS) was chosen for evaluation of cow trial data because it uses feed degradation parameters as input variables to estimate nutrient supply. Model prediction of milk yield matched observed values when cows maintained liveweight. Milk yield was underestimated at low intakes and overestimated at high intakes because no allowance is made for nutrient partitioning between milk production and liveweight change.en_US
dc.identifier.urihttp://hdl.handle.net/10179/1160
dc.language.isoenen_US
dc.publisherMassey Universityen_US
dc.rightsThe Authoren_US
dc.subjectForage plantsen_US
dc.subjectLolium perenneen_US
dc.subjectDigestionen_US
dc.subjectFeed utilisation efficiencyen_US
dc.subjectDairy cattleen_US
dc.subjectNew Zealanden_US
dc.subjectFeeding and feedsen_US
dc.subject.otherFields of Research::300000 Agricultural, Veterinary and Environmental Sciences::300400 Animal Production::300403 Animal nutritionen_US
dc.titleDigestion characteristics of forages, including perennial ryegrass at different stages of maturity, and supplementary feeding for dairy cows grazing pasture : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science, Institute of Food Nutrition and Human Health, Massey University, Palmerston North, New Zealanden_US
dc.typeThesisen_US
massey.contributor.authorChaves, Alexandre Vieira
thesis.degree.disciplineAnimal Scienceen_US
thesis.degree.grantorMassey Universityen_US
thesis.degree.levelDoctoralen_US
thesis.degree.nameDoctor of Philosophy (Ph.D.)en_US
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