Hu Wenping, Boerman Jacquelyn P, Aldrich James M
Nurture Research Center, Provimi, Brookville, OH 45309, USA.
Asian-Australas J Anim Sci. 2017 Aug;30(8):1105-1116. doi: 10.5713/ajas.16.0611. Epub 2017 Feb 1.
A meta-analysis was conducted to evaluate the effects of supplemental fat containing saturated free fatty acids (FA) on milk performance of Holstein dairy cows.
A database was developed from 21 studies published between 1991 and 2016 that included 502 dairy cows and a total of 29 to 30 comparisons between dietary treatment and control without fat supplementation. Only saturated free FA (>80% of total FA) was considered as the supplemental fat. Concentration of the supplemental fat was not higher than 3.5% of diet dry matter (DM). Dairy cows were offered total mixed ration, and fed individually. Statistical analysis was conducted using random- or mixed-effects models with Metafor package in R.
Sub-group analysis showed that there were no differences in studies between randomized block design and Latin square/crossover design for dry matter intake (DMI) and milk production responses to the supplemental fat (all response variables, p≥0.344). The supplemental fat across all studies improved milk yield, milk fat concentration and yield, and milk protein yield by 1.684 kg/d (p<0.001), 0.095 percent unit (p = 0.003), 0.072 kg/d (p<0.001), and 0.036 kg/d (p<0.001), respectively, but tended to decrease milk protein concentration (mean difference = -0.022 percent unit; p = 0.063) while DMI (mean difference = 0.061 kg/d; p = 0.768) remained unchanged. The assessment of heterogeneity suggested that no substantial heterogeneity occurred among all studies for DMI and milk production responses to the supplemental fat (all response variables, ≤24.1%; p≥0.166).
The effects of saturated free FA were quantitatively evaluated. Higher milk production and yields of milk fat and protein, with DMI remaining unchanged, indicated that saturated free FA, supplemented at ≤3.5% dietary DM from commercially available fat sources, likely improved the efficiency of milk production. Nevertheless, more studies are needed to assess the variation of production responses to different saturated free FA, either C16:0 or C18:0 alone, or in combination with potentially optimal ratio, when supplemented in dairy cow diets.
进行一项荟萃分析，以评估补充含饱和游离脂肪酸（FA）的脂肪对荷斯坦奶牛产奶性能的影响。
从1991年至2016年发表的21项研究中建立一个数据库，这些研究包括502头奶牛，以及在不补充脂肪的饮食处理组和对照组之间总共29至30次的比较。仅将饱和游离脂肪酸（占总脂肪酸的>80%）视为补充脂肪。补充脂肪的浓度不高于日粮干物质（DM）的3.5%。给奶牛提供全混合日粮，并单独饲养。使用R语言中的Metafor软件包，采用随机或混合效应模型进行统计分析。
亚组分析表明，在随机区组设计和拉丁方/交叉设计的研究之间，干物质摄入量（DMI）和补充脂肪后的产奶反应没有差异（所有反应变量，p≥0.344）。所有研究中的补充脂肪使产奶量、乳脂浓度和产量、乳蛋白产量分别提高了1.684千克/天（p<0.001）、0.095个百分点（p = 0.003）、0.072千克/天（p<0.001）和0.036千克/天（p<0.001），但乳蛋白浓度有下降趋势（平均差异=-0.022个百分点；p = 0.063），而DMI（平均差异=0.061千克/天；p = 0.768）保持不变。异质性评估表明，在所有研究中，DMI和补充脂肪后的产奶反应之间没有显著异质性（所有反应变量，≤24.1%；p≥0.166）。
对饱和游离脂肪酸的作用进行了定量评估。产奶量以及乳脂和乳蛋白产量提高，而DMI保持不变，这表明从市售脂肪来源补充占日粮DM≤3.5%的饱和游离脂肪酸可能提高了产奶效率。然而，当在奶牛日粮中补充时，需要更多研究来评估对不同饱和游离脂肪酸（单独的C16:0或C18:0，或与潜在最佳比例组合）的生产反应变化。
