Robyn Beck

Document Type

Thesis - University Access Only

Award Date

2011

Degree Name

Master of Science (MS)

Department / School

Animal Science

Abstract

Two experiments were conducted to determine the effects of replacing com with increasing amounts of glycerol on growth performance, carcass characteristics, nutrient digestibility, and rumen function of finishing wethers. The first experiment was designed to evaluate growth performance and carcass traits of finishing lambs of two different sire breeds fed treatment diets containing 0, 4, or 8% glycerol. Glycerol inclusion decreased average DMI for the third period (P = 0.03), but otherwise did not influence growth or feed efficiency. Sire breed had a significant effect on growth and carcass characteristics in finishing lambs, however, inclusion of glycerol at up to 8% of the diet DM did not alter growth or carcass traits. Carcass traits also were not significantly affected by replacing com with glycerol at up to 8% of the diet DM. Sire breed did have a significant effect on growth performance and carcass characteristics. Hampshire-sired wethers had heavier BW (P < 0.05), and better cumulative ADG (P = 0.03) when compared with Southdown-sired wethers. Hampshire-sired lambs also tended (P = 0.09) to have larger LM area than Southdown-sired lambs, whereas Southdown-sired lambs had more fat (P =0.01) and higher yield grades (P = 0.02) but tended to have higher DP (P = 0.09). Chi Square analysis also showed that Southdown-sired lambs also had a greater incidence (P= 0.02) of USDA Prime carcasses than Hampshire-sired lambs. Sire breed had a significant effect on growth and carcass characteristics in finishing lambs; however inclusion of glycerol at up to 8% of the diet DM did not alter growth or carcass traits. The second experiment was designed to determine the effect of feeding increasing amounts of glycerol on nutrient digestibility, rumen pH, rumen ammonia concentrations, PUN concentrations, and volatile fatty acid concentrations in finishing wethers. Glycerol replaced com at 0, 4, 8, or 12% of the treatment diets. Increasing the amount of glycerol had a tendency (P = 0.10) to decrease DMI in a quadratic manner (P = 0.03). Additionally, DE (Meal/kg) tended (P = 0.07) to increase linearly (P = 0.01) as glycerol concentration increased in the diet. Glycerol inclusion had no effect on DMD, OMD, DCP, MCP, DADF, DNDF, or ME. Glycerol inclusion did not affect acetate, propionate, butyrate, or total VF A concentrations. The acetate:propionate ratio and rumen pH were also unaffected by increasing glycerol concentration in the diet. Increasing glycerol concentration did tend (P = 0.10) to cause a quadratic (P = 0.04) response in rumen ammonia nitrogen levels. Time had a significant effect on all VFA and total VFA levels, acetate:propionate ratio, rumen pH, rumen ammonia nitrogen concentrations. The PUN concentrations were not affected by glycerol inclusion or time. An interaction between dietary treatment and time was observed for acetate, propionate, butyrate, and total VF A levels, but it was observed that all VFA concentrations followed a similar pattern over.

Key Words: glycerol, lambs, digestibility

Library of Congress Subject Headings

Lambs--Feeding and feeds

Glycerin

Format

application/pdf

Number of Pages

91

Publisher

South Dakota State University

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