Effects of tributyrin supplementation on ruminal microbial protein yield,fermentation characteristics and nutrients degradability in adult Small Tail ewes

Two trials were conducted to assess the effects of tributyrin (TB) supplementation on ruminal microbial protein yield and fermentation characteristics in adult sheep. In an in vitro trial, substrate was made to offer TB at 0, 2, 4, 6, and 8 g/kg on a dry matter (DM) basis and incubated for 48 hr. In an in vivo trial, 45 adult ewes were randomly assigned by initial body weight (55 ± 5 kg) to five treatments of nine animals over an 18‐day period. Total mixed ration was made to offer TB to ewes at 0, 2, 4, 6, and 8 g/kg on a DM basis. The in vitro trial showed that TB enhanced apparent degradation of DM (p = .009), crude protein (p < .001), neutral detergent fiber (p = .007) and acid detergent fiber (p = .010) and increased methanogenesis (p < .001), respectively. The in vivo trial showed that TB decreased DM intake (p < .001) and enhanced rumen microbial N synthesis (p < .001), respectively. Both in vitro and in vivo trials showed that TB increased total volatile fatty acid concentration and enhanced fibrolytic enzyme activity. The results indicated that TB might exert positive effects on microbial protein yield and fermentation in the rumen.     

内蒙古草原不同土壤pH条件下植物生物量和多样性的关系:样带调查和控制实验的比较研究

生物量与多样性的关系一直是生态学研究的热点问题,已有研究显示二者的关系受环境因子的影响,但是关于土壤pH变化对草原植物群落生物量和多样性的影响及其在样带空间调查实验与定点控制实验之间差异的研究还无报道。采用样带调查实验和控制实验相结合的方法,研究了在自然条件下内蒙古草原样带上植物群落生物量和多样性的关系变化及其与土壤pH的关系,同时通过外源添加硫酸或氢氧化钠溶液,研究人为改变土壤pH后草原植物群落生物量和多样性的关系变化,并比较样带调查实验和控制实验两种方法所得结果的差异及机制。研究结果表明:1)在样带空间梯度上,土壤pH变化主要受土壤类型、植被类型及干旱指数的影响。沿天然的pH梯度,地上生物量与土壤pH间呈现为显著的U型曲线关系,物种丰富度与土壤pH也呈显著的U型曲线关系,生物量与多样性二者之间为显著正相关关系;2)在定位的酸碱控制实验中,地上生物量与土壤pH间呈显著的上凸单峰曲线关系,物种丰富度与土壤pH之间也呈显著的单峰曲线关系,生物量与多样性的关系因植被类型而异:在荒漠草原二者为正相关,而在典型草原二者无显著相关性。可以看出,草原生物量和多样性与土壤pH密切相关,并且在样带上和控制实验中呈现出相反的结果,多样性和生物量的关系也不完全相同。两种研究方法出现差异的原因是样带观察反映的是生态系统长期适应的结果,而控制实验结果反映的是生态系统对环境变化的短期响应,这种时空尺度的差异造成了两种研究方法所得结果的不同。