Department of Research & Development, Trouw Nutrition, Stationsstraat 77, 3800 AGAmersfoort, The Netherlands.
Animal Nutrition Group, Wageningen University, P.O. Box 338, 6700 AHWageningen, The Netherlands.
Animal. 2020 Jul;14(7):1402-1412. doi: 10.1017/S1751731119002945. Epub 2019 Dec 19.
Current feed evaluation systems often assume that fermented starch (i.e. resistant starch (RS)) yields less energy than digested starch. However, growth rates of pigs fed low and high RS diets are often the same when feed is available ad libitum. This may be explained by its effect on digestive processes changing feeding behavior, and consequently energy utilization. This study aims to investigate the effect of RS on nutrient digestion and digesta passage rate in pigs, in combination with its effect on feeding behavior and growth performance under ad libitum conditions. In experiment 1, 20 male pigs (40 ± 2.82 kg) were fed diets containing either 50% waxy maize starch (low in RS (LRS)) or high-amylose maize starch (high in RS (HRS)), and soluble and insoluble indigestible markers. After 14 days of adaptation to the diets, pigs were fed hourly to reach steady state (6 h), dissected, and digesta were collected from eight segments. From the collected samples, nutrient digestion and passage rate of the solid and liquid digesta fraction were determined. In experiment 2, 288 pigs (80 ± 0.48 kg; sex ratio per pen 1 : 1; boar : gilt) were housed in groups of 6. Pigs were ad libitum-fed one of the experimental diets, and slaughtered at approximately 115 kg. Feed intake, growth and carcass parameters were measured. Ileal starch digestibility was greater for LRS-fed than for HRS-fed pigs (98.0% v. 74.0%; P < 0.001), where the additional undigested starch in HRS-fed pigs was fermented in the large intestine. No effects of RS on digesta passage rate of the solid or liquid digesta fraction and on feeding behavior were observed. Growth rate and feed intake did not differ between diets, whereas feed efficiency of HRS-fed pigs was 1%-unit higher than that of LRS-fed pigs (P = 0.041). The efficiency of feed used for carcass gain did not differ between diets indicating that the difference in feed efficiency was determined by the non-carcass fraction. Despite a 30% greater RS intake (of total starch) with HRS than with LRS, carcass gain and feed efficiency used for carcass gain were unaffected. RS did not affect digesta passage rate nor feeding behavior suggesting that the difference in energy intake between fermented and digested starch is compensated for post-absorptively. Our results indicate that the net energy value of fermented starch currently used in pig feed evaluation systems is underestimated and should be reconsidered.
当前的饲料评估系统通常假设发酵淀粉（即抗性淀粉（RS））比消化淀粉产生的能量更少。然而，当自由采食时，饲喂低 RS 和高 RS 日粮的猪的生长速度往往相同。这可以通过 RS 对消化过程的影响来解释，这种影响改变了采食行为，进而影响了能量利用。本研究旨在研究 RS 对猪养分消化和食糜通过速率的影响，并结合其在自由采食条件下对采食行为和生长性能的影响。在试验 1 中，20 头雄性猪（40 ± 2.82 kg）分别饲喂含有 50%蜡质玉米淀粉（RS 含量低（LRS））或高直链淀粉玉米淀粉（RS 含量高（HRS））和可溶性及不可消化标记物的日粮。适应日粮 14 天后，猪每小时饲喂一次以达到稳态（6 h），然后解剖，从 8 个部位收集食糜。从收集的样品中，确定了固体和液体食糜部分的养分消化和通过速率。在试验 2 中，288 头猪（80 ± 0.48 kg；每栏性别比例 1:1；公猪：母猪）分组饲养。猪自由采食一种试验日粮，体重约 115 kg 时屠宰。测定采食量、生长和胴体参数。LRS 组猪的回肠淀粉消化率高于 HRS 组猪（98.0%比 74.0%；P < 0.001），HRS 组猪未消化的淀粉在大肠中发酵。RS 对固体或液体食糜部分的食糜通过速率和采食行为没有影响。日粮间生长速度和采食量无差异，而 HRS 组猪的饲料效率比 LRS 组猪高 1%（P = 0.041）。用于胴体增重的饲料效率无差异，表明饲料效率的差异取决于非胴体部分。尽管 HRS 组猪的 RS 摄入量（总淀粉的 30%）比 LRS 组猪高，但胴体增重和用于胴体增重的饲料效率不受影响。RS 不影响食糜通过速率或采食行为，表明发酵淀粉和消化淀粉之间的能量摄入差异在吸收后得到了补偿。我们的结果表明，目前用于猪饲料评估系统的发酵淀粉的净能值被低估，应重新考虑。
