Ruminants have a unique metabolism and digestion of unsaturated fatty acids (UFA). Unlike monogastric animals, the fatty acid (FA) profile ingested by ruminants is not the same as that reaching the small intestine. The objective of this study was to evaluate whole raw soybeans (WS) in diets as a replacer for calcium salts of fatty acids (CSFA) in terms of UFA profile in the abomasal digesta of early- to mid-lactation cows. Eight Holstein cows (80 ± 20 d in milk, 22.9 ± 0.69 kg/d of milk yield, and 580 ± 20 kg of body weight; mean ± standard deviation) with ruminal and abomasal cannulas were used in a 4 × 4 Latin square experiment with 22-d periods. The experiment evaluated different fat sources rich in linoleic acid on ruminal kinetics, ruminal fermentation, FA abomasal flow, and milk FA profile of cows assigned to treatment sequences containing a control (CON), with no fat source; soybean oil, added at 2.68% of diet dry matter (DM); WS, addition of WS at 14.3% of diet DM; and CSFA, addition of CSFA at 2.68% of diet DM. Dietary fat supplementation had no effect on nutrient intake and digestibility, with the exception of ether extract. Cows fed fat sources tended to have lower milk fat concentration than those fed CON. In general, diets containing fat sources tended to decrease ruminal neutral detergent fiber digestibility in relation to CON. Cows fed WS had lower ruminal digestibility of DM and higher abomasal flow of DM in comparison to cows fed CSFA. As expected, diets containing fat supplements increased FA abomasal flow of C18:0 and total FA. Cows fed WS tended to present a higher concentration of UFA in milk when compared with those fed CSFA. This study suggests that under some circumstances, abomasal flow of UFA in early lactation cows can be increased by supplementing their diet with fat supplements rich in linoleic acid, regardless of rumen protection, with small effects on ruminal DM digestibility.

反刍动物具有独特的不饱和脂肪酸（UFA）代谢和消化能力。与单胃动物不同，反刍动物摄入的脂肪酸 (FA) 谱与到达小肠的脂肪酸 (FA) 谱不同。本研究的目的是评估日粮中的全生大豆 (WS) 作为脂肪酸钙盐 (CSFA) 替代品的泌乳早至中期奶牛皱胃食糜中的 UFA 分布。在 4 × 4 拉丁方实验中使用 8 头带有瘤胃和真胃插管的荷斯坦奶牛（产奶 80 ± 20 天，产奶量 22.9 ± 0.69 kg/d，体重 580 ± 20 kg；平均值 ± 标准差）。具有 22 天的周期。该实验评估了富含亚油酸的不同脂肪源对奶牛的瘤胃动力学、瘤胃发酵、FA 真胃流和牛奶 FA 谱的影响，这些奶牛分配给含有对照 (CON) 的处理序列，但不含脂肪源；大豆油，添加量为日粮干物质 (DM) 的 2.68%； WS，WS的添加量为饮食DM的14.3%；和CSFA，CSFA的添加量为饮食干物质的2.68%。除乙醚提取物外，膳食脂肪补充对营养摄入和消化率没有影响。饲喂脂肪来源的奶牛的乳脂浓度往往低于饲喂 CON 的奶牛。一般来说，含有脂肪源的日粮往往会降低瘤胃中性洗涤纤维的消化率（与 CON 相关）。与饲喂CSFA的奶牛相比，饲喂WS的奶牛具有较低的瘤胃消化率和较高的皱胃流量。正如预期的那样，含有脂肪补充剂的饮食增加了 C18:0 的 FA 皱胃流量和总 FA。与饲喂 CSFA 的奶牛相比，饲喂 WS 的奶牛在牛奶中往往呈现出更高浓度的 UFA。 这项研究表明，在某些情况下，无论瘤胃保护如何，通过在饮食中添加富含亚油酸的脂肪补充剂，可以增加泌乳早期奶牛的皱胃尿素流量，而对瘤胃干物质消化率的影响很小。