Frank Eyal, Livshitz Lilya, Portnick Yuri, Kamer Hadar, Alon Tamir, Moallem Uzi
Department of Ruminant Science, Institute of Animal Sciences, The Volcani Institute, 68 HaMaccabim Road, P.O. Box 15159, Rishon LeZion 7505101, Israel.
Department of Animal Science, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel.
Animals (Basel). 2022 Aug 15;12(16):2081. doi: 10.3390/ani12162081.
Instability in grain prices led to continuing worldwide growth in the proportion of fat supplements in lactating cows’ rations. However, fat supplementation was associated with decreases in feed intake, rumen fermentation, and feed digestibility. The present objectives were to test the effects of high-fat diets from calcium salts of palm oil fatty acids (CS-PFA) in lactating cow rations containing high proportions of concentrate, on feed intake, milk yields, rumen environment, and digestibility. Forty-two multiparous mid-lactation dairy cows were assigned to three treatments, designated as low fat (LF), moderate fat (MF), and high fat (HF) that contained (on DM basis), respectively, (i) 4.7% total fat with 1.7% CS-PFA, (ii) 5.8% total fat with 2.8% CS-PFA, and (iii) 6.8% total fat with 3.9% CS-PFA. Rumen samples were collected for pH, ammonia, and volatile fatty acid (VFA) measurements, and fecal grab samples were collected for digestibility measurements. A numerical trend of decreasing dry matter intake with increasing CS-PFA in diet was observed: 28.7, 28.5, and 28.1 kg/day in LF, MF, and HF, respectively (p < 0.20). No differences between treatments were observed in milk yields and milk-fat percentages, but protein percentage in milk tended to fall with increasing dietary CS-PFA content (p < 0.08), which resulted in 6.4% smaller protein yields in the HF than in the LF group (p < 0.01). Milk urea nitrogen was 15.3% higher in HF than in LF cows (p < 0.05). Rumen pH was higher at all sampling times in the MF and HF than in the LF cows. Concentrations of propionic acid and total VFA were higher in LF than in MF and HF cows. The apparent total-tract digestibility of dry matter was higher with LF than with HF (p < 0.002), and that of organic matter was lowest with the HF diet (p < 0.005). The apparent NDF digestibility declined with increasing dietary fat content, and it was 8.5 percentage points lower in HF than in LF cows (p < 0.009). Apparent fat digestibility increased with increasing dietary fat content, and it was higher by 10.4 percentage points in the HF than in the LF group (p < 0.004). In conclusion, diets with high concentrate-to-forage ratios, containing up to 6.8% total fat and 3.9% CS-PFA, negatively affected rumen fermentation and NDF digestibility in high-yielding dairy cows; however, the effects on yields were minor, indicating that, under specific circumstances, the inclusion of large amounts of CS-PFA in dairy cows’ rations with low fiber content is feasible.
谷物价格的不稳定导致泌乳奶牛日粮中脂肪补充剂的比例在全球范围内持续增加。然而，补充脂肪会导致采食量、瘤胃发酵和饲料消化率下降。本研究的目的是测试在高比例精料的泌乳奶牛日粮中，添加棕榈油脂肪酸钙盐（CS-PFA）的高脂日粮对采食量、产奶量、瘤胃环境和消化率的影响。将42头经产中期泌乳奶牛分为三个处理组，分别为低脂（LF）、中脂（MF）和高脂（HF）组，日粮（基于干物质）中分别含有：（i）总脂肪4.7%，CS-PFA 1.7%；（ii）总脂肪5.8%，CS-PFA 2.8%；（iii）总脂肪6.8%，CS-PFA 3.9%。采集瘤胃样本用于测量pH值、氨和挥发性脂肪酸（VFA），采集粪便样本用于测量消化率。观察到随着日粮中CS-PFA含量增加，干物质采食量呈下降趋势：LF组、MF组和HF组分别为28.7、28.5和28.1千克/天（p<0.20）。各处理组之间的产奶量和乳脂率没有差异，但乳蛋白率随着日粮中CS-PFA含量的增加而呈下降趋势（p<0.08），导致HF组的蛋白产量比LF组低6.4%（p<0.01）。HF组奶牛的乳尿素氮比LF组高15.3%（p<0.05）。MF组和HF组在所有采样时间的瘤胃pH值均高于LF组奶牛。LF组奶牛的丙酸和总VFA浓度高于MF组和HF组。LF组的干物质表观全肠道消化率高于HF组（p<0.002），HF组日粮的有机物表观全肠道消化率最低（p<0.005）。中性洗涤纤维（NDF）的表观消化率随着日粮脂肪含量的增加而下降，HF组比LF组低8.5个百分点（p<0.009）。脂肪表观消化率随着日粮脂肪含量的增加而增加，HF组比LF组高10.4个百分点（p<0.004）。总之，精粗比高、总脂肪含量高达6.8%且CS-PFA含量为3.9%的日粮对高产奶牛的瘤胃发酵和NDF消化率有负面影响；然而，对产奶量的影响较小，这表明在特定情况下，在低纤维含量的奶牛日粮中添加大量CS-PFA是可行的。
