Torres Rodrigo N S, Bertoco João P A, de Arruda Maria C G, Rodrigues Julia L, Coelho Larissa M, Paschoaloto Josimari R, de Almeida Júnior Gercílio A, Ezequiel Jane M B, Almeida Marco T C
Animal Unit of Digestive and Metabolic Studies, Department of Animal Science, School of Agricultural and Veterinarian Sciences, São Paulo State University (UNESP), Jaboticabal, SP, Brazil.
Department of Animal Science, Federal University of Espírito Santo, Vitoria, ES, Brazil.
Transl Anim Sci. 2021 Jan 27;5(1):txab012. doi: 10.1093/tas/txab012. eCollection 2021 Jan.
The use of glycerin in diets for dairy cows initially emerged as an alternative for the prevention and control of ketosis. However, despite some controversy, there are still several studies associating glycerin with increases in daily milk yield, with possible changes in its constituents. Therefore, the objective of this study was to evaluate, using a meta-analysis approach, the effect of glycerin inclusion in dairy cow diets on milk fatty acid. Twenty-two peer-reviewed publications with 66 treatment means were included in data set. The effect of glycerin inclusion in diet (treatment) were evaluated using random-effect models to examine the weighted mean differences (WMD) between a control diet (without glycerin in the diet) and the treatment diet. Heterogeneity was explored by meta-regression and subgroup analysis performed for: genetic type; days in milk; experimental period; glycerin in diet; glycerin type and concentrate in diet. Inclusion of glycerin in the diet increased the digestibility of dry matter and protein, as well as ruminal propionate. It did not affect dry matter intake ( = 0.351) and milk yield ( = 0.730). The effect of glycerin inclusion on the milk fat yield is dependent on the genetic group, in which Holstein (WMD = -0.04 kg/d; = 0.010) and Holstein-crossbreed (WMD = -0.10 kg/d; < 0.0001) cows produced less fat in milk compared to Jersey cows, when glycerin was included in the diets. Glycine inclusions of up to 100 g/kg in the diet of dairy cows did not negatively affect milk production and composition. However, inclusions above 150 g/kg of glycerin in the diet reduced the concentration of fat, and of unsaturated, monounsaturated, polyunsaturated fatty acids and conjugated linoleic acid (CLA C18: 2 cis-9 and trans-11) in milk. The results reported in our meta-analysis does not demonstrate the effectiveness of glycerin in improving the composition of milk and a group of fatty acids of importance for human health such as C18: 2 cis-9, trans-11 CLA.
在奶牛日粮中使用甘油最初是作为预防和控制酮病的一种替代方法出现的。然而，尽管存在一些争议，但仍有多项研究将甘油与日产奶量增加相关联，且其成分可能会发生变化。因此，本研究的目的是采用荟萃分析方法，评估在奶牛日粮中添加甘油对乳脂肪酸的影响。数据集中纳入了22篇经同行评审的出版物，包含66个处理均值。使用随机效应模型评估日粮中添加甘油（处理）的效果，以检验对照日粮（日粮中不含甘油）与处理日粮之间的加权平均差异（WMD）。通过荟萃回归和亚组分析探讨异质性，亚组分析针对以下因素进行：遗传类型；泌乳天数；试验期；日粮中的甘油；甘油类型和日粮中的精料。日粮中添加甘油可提高干物质和蛋白质的消化率，以及瘤胃丙酸水平。它不影响干物质摄入量（P = 0.351）和产奶量（P = 0.730）。添加甘油对乳脂肪产量的影响取决于遗传群体，当日粮中添加甘油时，荷斯坦奶牛（WMD = -0.04 kg/d；P = 0.010）和荷斯坦杂交奶牛（WMD = -0.10 kg/d；P < 0.0001）的乳脂肪产量低于泽西奶牛。在奶牛日粮中添加高达100 g/kg的甘油不会对产奶量和乳成分产生负面影响。然而，日粮中甘油添加量超过150 g/kg会降低乳中脂肪、不饱和脂肪酸、单不饱和脂肪酸、多不饱和脂肪酸和共轭亚油酸（CLA C18: 2顺-9和反-11）的浓度。我们的荟萃分析结果并未证明甘油在改善乳成分以及对人类健康重要的一组脂肪酸（如C18: 2顺-9，反-11 CLA）方面的有效性。
