Weld K A, Armentano L E
Department of Dairy Science, University of Wisconsin-Madison, Madison 53706.
Department of Dairy Science, University of Wisconsin-Madison, Madison 53706.
J Dairy Sci. 2017 Mar;100(3):1766-1779. doi: 10.3168/jds.2016-11500. Epub 2017 Jan 11.
The objective of this meta-analysis was to determine the effects of supplemental fat on fiber digestibility in lactating dairy cattle. Published papers that evaluated the effects of adding fat to the diets of lactating dairy cattle on total-tract neutral detergent fiber digestibility (ttNDFd) and dry matter intake (DMI) were compiled. The final data set included 108 fat-supplemented treatment means, not including low-fat controls, from 38 publications. The fat-supplemented treatment means exhibited a wide range of ttNDFd (49.4% ± 9.3, mean ± standard deviation) and DMI (21.3 kg/d ± 3.5). Observations were summarized as the difference between the treatment means for fat-supplemented diets minus their respective low-fat control means. Additionally, those differences were divided by the difference in diet fatty acid (FA) concentration between the treatment and control diets. Treatment means were categorized by the type of fat supplement. Supplementing 3% FA in the diet as medium-chain fats (containing predominately 12- and 14-carbon saturated FA) or unsaturated vegetable oil decreased ttNDFd by 8.0 and 1.2 percentage units, respectively. Adding 3% calcium salts of long-chain FA or saturated fats increased ttNDFd by 3.2 and 1.3 percentage units, respectively. No other fat supplement type affected ttNDFd. Except for saturated fats and animal-vegetable fats, supplementing dietary fat decreased DMI. When the values for changes in ttNDFd are regressed on changes in DMI there was a positive relationship, though the coefficient of determination is only 0.20. When changes in ttNDFd were regressed on changes in DMI, within individual fat supplement types, there was no relationship within calcium salt supplements. There was a positive relationship between changes in ttNDFd and changes in DMI for saturated fats. Neither relationship suggested that the increased ttNDFd with calcium salts or saturated FA was due to decreased DMI for these fat sources. A subset of the means included measured ruminal neutral detergent fiber digestion. Analysis of this smaller data set did not suggest that ruminal neutral detergent fiber digestibility is depressed by fat supplementation more than ttNDFd. Adding fats, other than those with medium-chain FA, consistently increased digestible energy density of the diet. However, due to reduced DMI, this increased energy density may not result in increased digestible nutrient intake.
本荟萃分析的目的是确定补充脂肪对泌乳奶牛纤维消化率的影响。我们收集了已发表的评估在泌乳奶牛日粮中添加脂肪对全消化道中性洗涤纤维消化率（ttNDFd）和干物质采食量（DMI）影响的论文。最终数据集包括来自38篇出版物的108个补充脂肪处理均值，不包括低脂对照。补充脂肪处理均值的ttNDFd（49.4%±9.3，均值±标准差）和DMI（21.3 kg/d±3.5）呈现出广泛的范围。观察结果总结为补充脂肪日粮的处理均值与其各自低脂对照均值之间的差异。此外，这些差异除以处理日粮和对照日粮之间的日粮脂肪酸（FA）浓度差异。处理均值按脂肪补充剂类型分类。在日粮中补充3%的中链脂肪（主要含12碳和14碳饱和FA）或不饱和植物油分别使ttNDFd降低8.0和1.2个百分点。添加3%的长链FA钙盐或饱和脂肪分别使ttNDFd提高3.2和1.3个百分点。没有其他脂肪补充剂类型影响ttNDFd。除饱和脂肪和动植物脂肪外，补充日粮脂肪会降低DMI。当ttNDFd的变化值与DMI的变化值进行回归分析时，存在正相关关系，尽管决定系数仅为0.20。当在个体脂肪补充剂类型内将ttNDFd的变化与DMI的变化进行回归分析时，钙盐补充剂内不存在关系。饱和脂肪的ttNDFd变化与DMI变化之间存在正相关关系。两种关系均未表明钙盐或饱和FA使ttNDFd增加是由于这些脂肪来源的DMI降低所致。部分均值包括测定的瘤胃中性洗涤纤维消化率。对这个较小数据集的分析并未表明瘤胃中性洗涤纤维消化率因补充脂肪而比ttNDFd受到更严重的抑制。添加除中链FA以外的脂肪持续增加日粮的可消化能量密度。然而，由于DMI降低, 这种增加的能量密度可能不会导致可消化养分摄入量增加。
