Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5A8, Canada.
J Anim Sci. 2012 Apr;90(4):1233-41. doi: 10.2527/jas.2010-3458. Epub 2011 Oct 7.
Three studies were performed to examine the effect of starch and protein digestion rates on N retention in grower pigs. In Exp. 1, the glycemic index (GI) of corn, a malting barley, and a slow-rumen-degradable barley (SRD-barley) were measured using 6 barrows (BW = 18.0 ± 0.5 kg). The GI of malting barley was greater (P < 0.05) than that of SRD-barley (71.1 vs. 49.4), and the GI of both barley cultivars was less (P < 0.05) than that of corn (104.8). In Exp. 2, the standardized ileal digestibility of AA and DE content of the 3 ingredients were determined using 5 ileal-cannulated barrows (BW = 20.7 ± 2.3). The apparent total-tract energy digestibility values of corn (86.1%) and malting barley (85.7%) were greater (P < 0.05) than that of SRD-barley (82.3%). The standardized ileal digestibility of Lys was 94.0, 92.6, and 92.4% for corn, malting barley, and SRD-barley, respectively, and did not differ among grains. In Exp. 3, 6 diets were formulated to equal DE (3.40 Mcal/kg), standardized ileal digestibility of Lys (8.6 g/kg), starch (424.9 g/kg), and digestible CP (180.0 g/kg) using the values obtained in Exp. 2. Three GI [high (corn), medium (malting barley), and low (SRD-barley)] and 2 rates of protein digestion [rapid (soy protein hydrolysate) and slow (soy protein isolate)] were tested in a 3 × 2 factorial arrangement with 36 barrows (BW = 32.2 ± 2.5 kg). Pigs were fed 3.0 times the maintenance energy requirement daily in 2 meals for 2 wk and were housed in metabolic crates to collect feces and urine separately. At the end of the study, intestinal contents were collected from 4 equal-length segments of the small intestine. The percentage of unabsorbed CP in segment 1 relative to dietary CP was greater (P < 0.05) for the soy protein isolate diet than for the soy protein hydrolysate diet (170.3 vs. 116.5%). The percentages of unabsorbed starch in segments 1 and 2 were greater (P < 0.05) for the SRD-barley diet than for the malting barley or corn diet. Nitrogen intake and fecal N excretion were greater (P < 0.05) for pigs fed the malting barley and SRD-barley diets than for pigs fed the corn diet. Urinary N excretion was greater (P < 0.05) for pigs fed the SRD-barley diet than for pigs fed the corn or malting barley diet. Pigs fed slowly digestible starch (SRD-barley; 46.6%) had less (P < 0.05) net N retention than pigs fed corn or malting barley (54.7 and 54.1%, respectively). In conclusion, slowly digestible starch sources such as SRD-barley may not be suitable to support maximum protein deposition in restricted-fed grower pigs.
三项研究旨在探讨淀粉和蛋白质消化率对生长猪氮保留的影响。在实验 1 中，使用 6 头阉公猪（BW=18.0±0.5kg）测定玉米、发芽大麦和缓慢瘤胃降解大麦（SRD-大麦）的血糖指数（GI）。发芽大麦的 GI 高于 SRD-大麦（71.1 对 49.4），且两种大麦品种的 GI 均低于玉米（104.8）。在实验 2 中，使用 5 头回肠结扎阉公猪（BW=20.7±2.3kg）确定 3 种原料的 AA 标准回肠可消化性和 DE 含量。玉米（86.1%）和发芽大麦（85.7%）的表观全肠道能量消化率高于 SRD-大麦（82.3%）。玉米、发芽大麦和 SRD-大麦的 Lys 标准回肠可消化率分别为 94.0%、92.6%和 92.4%，且在谷物间无差异。在实验 3 中，使用实验 2 获得的值，通过 3.40 Mcal/kg 的 DE、8.6g/kg 的 Lys 标准回肠可消化性、424.9g/kg 的淀粉和 180.0g/kg 的可消化 CP，配制 6 种日粮，使 GI（高[玉米]、中[发芽大麦]和低[SRD-大麦]）和 2 种蛋白质消化率（快速[大豆蛋白水解物]和缓慢[大豆蛋白分离物]）在 3×2 因子设计中进行测试，共有 36 头阉公猪（BW=32.2±2.5kg）。猪每天按照维持能量需要量的 3 倍投喂 2 次，在代谢笼中饲养 2 周，单独收集粪便和尿液。研究结束时，从小肠 4 个等长段中采集肠道内容物。与大豆蛋白水解物日粮相比，大豆蛋白分离物日粮第 1 段未吸收 CP 占日粮 CP 的比例更高（P<0.05）（170.3%对 116.5%）。第 1 段和第 2 段未吸收淀粉的比例，SRD-大麦日粮高于发芽大麦或玉米日粮（P<0.05）。与玉米日粮相比，饲喂发芽大麦和 SRD-大麦日粮的猪氮摄入量和粪氮排泄量更高（P<0.05）。与玉米或发芽大麦日粮相比，饲喂 SRD-大麦日粮的猪尿氮排泄量更高（P<0.05）。饲喂缓慢消化淀粉（SRD-大麦；46.6%）的猪的净氮保留量低于饲喂玉米或发芽大麦的猪（分别为 54.7%和 54.1%）。总之，SRD-大麦等缓慢消化淀粉源可能不适合支持限制饲养生长猪的最大蛋白质沉积。
