颗粒全混合日粮(P-TMR)饲喂,这已经成为为育肥绵羊提供营养的普遍做法,需要仔细考虑牧草中性洗涤纤维(FNDF)和瘤胃可降解淀粉(RDS)之间的平衡,以保持适当的瘤胃功能。本研究旨在探讨饮食FNDF/RDS比值(FRR)对咀嚼活动的影响,瘤胃发酵,饲喂P-TMR日粮的湖羊的瘤胃微生物和养分消化率。这项研究利用了八只雄性虎羊,遵循4×4拉丁正方形设计,每期31天。饮食包括四个FRR水平:1.0(高FNDF/RDS比率,HFRR),0.8(中高FNDF/RDS比,MHFRR),0.6(中低FNDF/RDS比率,MLFRR)和0.4(低FNDF/RDS比率,LFRR)。降低饮食FRR水平导致瘤胃最小pH和平均pH线性降低,同时线性增加pH值低于5.8和5.6的持续时间和面积,以及酸中毒指数。HFRR和MHFRR组的绵羊没有出现亚急性瘤胃酸中毒(SARA),而另外两组的绵羊则这样做。总挥发性脂肪酸的浓度以及丙酸和戊酸的摩尔比,以及瘤胃中的乳酸浓度随着饮食FRR的降低而线性增加,乙酸盐的摩尔比和乙酸盐与丙酸盐的摩尔比线性下降。NDF和ADF对苜蓿干草的降解具有降低饮食FRR的二次响应。DM的表观消化率,有机质(OM),当饮食FRR降低时,NDF和ADF线性降低。此外,降低饮食FRR导致OTU线性减少,瘤胃微生物区系的Chao1和Ace指数。降低饮食中的FRR会增加分配为Firmicutes的读数百分比,但它降低了瘤胃中指定为拟杆菌的读数百分比。在属一级,分配为Prevotella的读数百分比,Ruminococus,丁氏弧菌,当饮食FRR降低时,丁酸弧菌线性降低。这项研究的这些结果表明,0.8的饮食FRR对于预防SARA的发作至关重要,并促进瘤胃微生物的丰富度增加,还可以提高纤维的消化率。这是配制绵羊P-TMR日粮时推荐的饮食FRR参考。
Pelleted total mixed ration (P-TMR) feeding, which has become a common practice in providing nutrition for fattening sheep, requires careful consideration of the balance between forage neutral detergent fiber (FNDF) and rumen degradable starch (RDS) to maintain proper rumen functions. The present study aimed to investigate the effects of the dietary FNDF/RDS ratio (FRR) on chewing activity, ruminal fermentation, ruminal microbes, and nutrient digestibility in Hu sheep fed a P-TMR diet. This study utilized eight ruminally cannulated male Hu sheep, following a 4 × 4 Latin square design with 31 d each period. Diets consisted of four FRR levels: 1.0 (high FNDF/RDS ratio, HFRR), 0.8 (middle high FNDF/RDS ratio, MHFRR), 0.6 (middle low FNDF/RDS ratio, MLFRR), and 0.4 (low FNDF/RDS ratio, LFRR). Reducing the dietary FRR levels resulted in a linear decrease in ruminal minimum pH and mean pH, while linearly increasing the duration and area of pH below 5.8 and 5.6, as well as the
acidosis index. Sheep in the HFRR and MHFRR groups did not experience subacute ruminal
acidosis (SARA), whereas sheep in another two groups did. The concentration of total volatile fatty acid and the molar ratios of propionate and valerate, as well as the concentrate of lactate in the rumen linearly increased with reducing dietary FRR, while the molar ratio of acetate and acetate to propionate ratio linearly decreased. The degradability of NDF and ADF for alfalfa hay has a quadratic response with reducing the dietary FRR. The apparent digestibility of dry matter, organic matter, neutral detergent fiber, and acid detergent fiber linearly decreased when the dietary FRR was reduced. In addition, reducing the dietary FRR caused a linear decrease in OTUs, Chao1, and Ace index of ruminal microflora. Reducing FRR in the diet increased the percentage of reads assigned as Firmicutes, but it decreased the percentage of reads assigned as Bacteroidetes in the rumen. At genus level, the percentage of reads assigned as Prevotella, Ruminococcus, Succinivibrio, and Butyrivibrio linearly decreased when the dietary FRR was reduced. The results of this study demonstrate that the dietary FRR of 0.8 is crucial in preventing the onset of SARA and promotes an enhanced richness of ruminal microbes and also improves fiber digestibility, which is a recommended dietary FRR reference when formulating P-TMR diets for sheep.
Forage neutral detergent fiber (FNDF) and rumen degradable starch (RDS) are key components of carbohydrates in the diet for ruminants, which would reflect saliva secretion and the acid production potential of feed. However, appropriate FNDF to RDS ratios (FRR) applicable to ruminants under the condition of pelleted total mixed ration (P-TMR) feeding have not been reported. In this study, we investigated the effects of the dietary FRR on chewing activity, ruminal fermentation, ruminal microbial communities, and nutrient digestibility of Hu sheep under P-TMR feeding. The results indicate that reducing dietary FRR levels would induce
acidosis in sheep, which negatively affected fiber utilization and ruminal bacterial communities. The FRR of 0.8 was a recommended dietary FRR when formulating a P-TMR diet for fattening sheep, as indicated by decreased ruminal
acidosis risk and increased richness of ruminal microbes in the rumen as well as nutrient digestibility.