Effect of manipulation of growth and fermentation patterns on nutrient availability and performance of feedlot cattle

Abstract

Alteration of ruminal environment by nutritional strategy presents opportunities for manipulating beef cattle growth. Changing fermentation patterns by altering feed type can impact both the composition and rate of gain in beef cattle. Three experiments were conducted to examine the effect of manipulation of growth and fermentation patterns on nutrient availability and performance of feedlot cattle. Experiment 1 studied the impact of ruminal environment on the passage of omega-3 fatty acids through the rumen of grass-fed verses grain-fed cattle. Omasal samples were collected from steers fed either fresh green chop, a high grain diet supplemented with flaxseed oil, or a high grain diet supplemented with corn oil. Regardless of diet, fatty acids with the greatest number of unsaturated bonds found in the highest abundance were transformed preferentially. Despite no differences (P = 0.88) in omega-3 transformation across treatments, grain-fed cattle with a flaxseed oil supplement demonstrated the greatest (P < 0.01) g of omega-3 fatty acid flow escaping biohydrogenation due to an increase in intake of dietary omega-3 fatty acids. Experiment 2 evaluated how utilization of bio-fuel coproducts impacts rumen environment and fatty acid profile at end point of fermentation. Omasal samples were collected from steers fed a steam flaked corn (SFC) basal diet with a portion of corn replaced by distillers grains (DGS) (40%), crude glycerin (GLY) (10%) or both. Total unsaturated fatty acids concentration in digesta were not different (P = 0.43) for the main effect of GLY, which indicates GLY is an effective alternative to corn when provided at the dietary concentrations evaluated in this study. The decrease (P < 0.01) in unsaturated fatty acids in digesta for main effect of DGS may be beneficial for shelf life stability of meat. Experiment 3 used a meta-analysis approach to examine how nutritional strategy and performance during a post-weaning growing phase can be used to predict finishing performance and carcass characteristics. When examining feedlot and carcass performance attributes by growing strategy factors, like ADGgrowing, DOFgrowing, and initial BWfinishing, interacted to create the most optimal compensatory gain response. Optimal combinations of DOFgrowing and initial BWgrowing differed between performance characteristics (Table 4.6) but as an average across dressing percent, LMA, Final BWfinishing, and HCW it was identified that maximized performance occurred when cattle began the growing phase around 240 kg.