Masters Theses

Date of Award

8-1979

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Science

Major Professor

J. W. Holloway

Committee Members

W. T. Butts Jr., F. D. Kirkpatrick

Abstract

Seventy-eight mature Angus cows were evaluated for rumen fluid volume using a 2.5% lithium sulfate (Li2SO4 * H2O) solution as a marker substance. At this time all cows were weighed and ultrasonic fatness over the twelfth rib was estimated. Cows were then photographed and height at the withers, length from point of shoulder to hooks, depth of heart and hook width were estimated from slides. Each cow was fed 4.75 grams of Cr2O3 in 249 grams of feed at each of two feedings (8:00 a.m. and 5:00 p.m.) per day for 158 days (April 20 - October 5). Fecal samples collected were analyzed for chromium and acid detergent lignin (ADL). Forage ADL was estimated by the cage and strip method simultaneously. Regression was used to predict dry matter intake per day (DMI), digestibility (DIG) and digestible dry matter intake per day (DMD) for each cow (mean values for period). Digestibility of the high quality pasture was 59% compared to 55% for the low quality pasture. DM intake, digestibility, and digestible DM intake as averages of grazing season for cows grazing high quality pasture was not significantly affected by rumen fluid volume (P > .05). Average DM intake and average digestibility intake were influenced (P < .06 and P < .08 respectively) by rumen fluid volume for cows grazing low quality pasture. Body weight (kg), height at the withers (cm), length from point of shoulder to hooks (cm), depth of heart (cm), and hook width (cm) all significantly affected rumen fluid volume positively (P < .05). Fat thickness (mm) had no significant effect on rumen fluid volume (P > .05). However, fat thickness did have a significant negative effect on rumen fluid volume as a percent of body weight (P < .05). Body weight also had a significant negative effect on rumen fluid volume as a percent of body weight (P < .05). Mean milk production, milk solids non-fat and weaning weight of the calves were not significantly affected by rumen fluid volume or rumen fluid volume as a percent of body weight (P > .05 and P > .05 respectively). However, rumen fluid volume and rumen fluid volume as a percent of body weight did have a significant negative effect on milk butterfat percent (P < .05 and P < .05 respectively) which was possibly due to chance.

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