摘要
The objective of this research was to evaluate if the decline in gain-to-feed ratio (G:F) during finishing in beef cattle could be due to a reduction in nutrient digestion, short chain fatty acid absorption, or post-absorptive nutrient utilization, and those responses were influenced by the dietary energy source or timing of provision. A high-lipid byproduct pellet (HLP) was used as a partial replacement for barley grain in a high concentrate finishing diet to partially replace starch with lipid as the energy source. Yearling steers were used for performance evaluations and ruminally cannulated Hereford crossbred heifers were used for nutrient metabolism studies. The dry matter (DM), organic matter (OM), crude protein (CP) and neutral detergent fibre (NDF) digestibility of HLP diets were lower than the barley-based control diet (CON). Utilizing a phase-feeding strategy and partially replacing barley grain and canola meal with a high-fibre high-lipid byproduct pellet in the latter part of the finishing period may improve carcass yield grade without affecting average daily gain and G:F. With advancing days on feed, diet DM digestibility (P = 0.02) and insulin resistance (P = 0.04) increase without changes in ruminal pH and plasma metabolite clearance rates. A marginal increase in forage inclusion with the HLP diet increased ADG (P = 0.04). Increasing dietary lipid supply up to 6% of DM using HLP did not affect the digesta flow and rumen fermentation parameters, therefore, increased lipid content is not associated with reduced feed efficiency of the HLP diet. In conclusion, decreasing feed efficiency in the later stages of finishing in beef cattle is most likely due to changes in the post absorptive nutrient metabolism, and these changes are not influenced by the dietary energy source. The small particle size of feed ingredients within the byproduct pellet may be the factor associated with decreased feed efficiency of HLP pellet rather than lipid content.
摘要译文
本研究的目的是评估牛肉牛完成过程中增益比率（g：f）的下降可能是由于营养消化，短链脂肪酸吸收或吸收后营养利用率的降低并且这些反应受到饮食能源或规定的影响。高脂质的副产物沉淀（HLP）用作大浓浓缩液的大麦籽粒的部分替代，以部分替代脂质作为能量源的淀粉。一岁渐次阉牛用于绩效评估，尤为ruminally插管符合杂交的杂交母牛用于营养代谢研究。 HLP饮食的干物质（DM），有机物（OM），粗蛋白（CP）和中性清洁剂（NDF）消化率低于基于大麦的对照饮食（CON）。在整理周期的后半部分中利用相馈策略和部分更换大麦谷物和油菜粉，可以改善胴体产量等级，而不会影响平均日益增长和G：F。随着饲料的推进日，饮食DM消化率（P = 0.02）和胰岛素抵抗（P = 0.04）增加而不会变化瘤胃pH和血浆代谢物间隙率。与HLP饮食的饲料含有边际增加增加ADG（P = 0.04）。使用HLP增加膳食脂质供应高达6％的DM不影响DIGESTA流量和瘤胃发酵参数，因此，增加的脂质含量与HLP饮食的饲料效率降低无关。总之，由于后吸收营养代谢的变化，降低了牛肉牛的后期阶段的饲料效率，并且这些变化不受膳食能源的影响。副产物颗粒内的饲料成分的小粒径可以是与HLP颗粒的饲料效率降低而不是脂质含量相关的因子。
Joy, Faustin. Effect of energy source, timing of provision, and days on feed on feed efficiency of finishing beef cattle[D]. CA: University of Saskatchewan, 2020