Digitized by Kansas Correctional Industries

Typescript. / Digitized by Kansas Correctional Industries

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Thesis (Ing. Agrónomo)--Universidad Técnica de Oruro, Facultad de Ciencias Agrícolas Pecuarias y Veterinarias, Departamento de Zootecnía y Veterinaía, 2005. / Reproduced from copy at BYU's Benson Institute. Includes bibliographical references (leaves [63]-67).

This study was designed to provide information on some of the factors affecting voluntary consumption and digestibility of forages by sheep. A wet sieving procedure was used to determine particle size distribution in the reticulo-rumen, omasum and abomasum of sheep fed 100 % prebloom alfalfa or 100 % second-cut Altai wild ryegrass hays or mixtures of these with tall wheatgrass or Altai wild ryegrass straws. The study also compared second-cut Altai wild ryegrass and prebloom alfalfa as components in an all forage diet for sheep. Each diet was fed ad libitum to eight Romanov x Western whiteface wether lambs weighing 22 to 25 kg during the intake and digestibility trials. For the determination of particle size distribution, the animals were slaughtered at 12, 24, 36, and 48 hours after feed removal and the contents of the reticulo-rumen, omasum and abomasum sampled. Five different methods of describing digesta particle size distribution were compared as to their ability to predict voluntary intake and digestibility of the forages by sheep. The best method for expressing particle size distribution in the reticulo-rumen in terms of ability to predict dry matter digestibility (DMD) was the proportion of soluble dry matter in total dry matter (PSDM). A significant (P< 0.05) correlation (r = 0.84) between PSDM and dry matter digestibility, 12 hours after feed removal was obtained. PSDM in omasal digesta 24 hours after feed removal was also highly correlated with DMD and energy digestibility (r = 0.97, 0.91, respectively). Very high correlations were obtained between PSDM in abomasal digesta 24 hours after feed removal and digestibility of cellulose, NDF and ADF (r = 0.99, 0.97 and 0.97 respectively). The proportion of particles less than 1mm to the total particles (PIP) in the reticulo-rumen gave the most consistent correlations with intake of dry matter and energy. Voluntary intake of dry matter by the animals on the alfalfa-based diets were significantly higher (P< 0.05) than those on the second-cut Altai wild ryegrass-based diets. However, the apparent digestibility coefficients of the proximate fractions in the Altai wild ryegrass diets were significantly higher (P< 0.05) than those of diets containing alfalfa. Daily intake of digestible energy by animals on 100 % alfalfa was not significantly different from that of animals on 100 % second-cut Altai wild ryegrass. The difference between their respective combinations with tall wheatgrass and Altai wild ryegrass straws were also not significant. It was concluded that PIP and PSDM are indeces based on biologically significant fractions and may therefore have greater relevance than purely mathematical or statistical descriptions of particle size distribution in digesta. In this regard, the relationship between PSDM and digestibility and, PIP and intake are consistent with published theory and can be used in mathematical models to examine control processes in feed intake, rate of passage and digestion. The study also indicated that second-cut Altai wild ryegrass harvested at the prebloom stage can be used as a substitute for alfalfa in an all-forage diet for winter feeding of sheep. / Land and Food Systems, Faculty of / Graduate

A controlled feeding experiment was conducted to compare the influence of barn-cured and field-cured alfalfa hay out from the same field on milk production and liveweight of dairy cows. Twelve Holstein cows were used in this trial. The double-reversal feeding method was followed. Grain was fed at the same rate to each group of cows. Hay was fed as the only source of roughage, and equal amounts of the two kinds of hay were fed to the two groups of cows. There was practically no difference in the total consumption of the two kinds of hay. Analysis of variance on the amounts of four per cent fat-corrected milk produced revealed highly significant differences at the one per cent level in favor of the barn-cured hay. The hays were sampled at regular intervals for proximate analysis. At the time of feeding the barn-cured hay contained .36 per cent more moisture, 2.63 per cent more protein, .26 per cent more fat, 1.20 per cent less fiber, 2.26 per cent less nitrogen-free extract, and .66 per cent more ash. The cows gained slightly in liveweight when they received the field-cured hay and lost slightly in liveweight when they received the barn-cured hay. Liveweight changes were not significant when analyzed statistically. / Master of Science

Call number: LD2668 .T4 1932 B43

Call number: LD2668 .T4 1958 S79

Call number: LD2668 .T4 1928 W32

Call number: LD2668 .T4 1929 B71