Changes of rumen pH, fermentation and microbial population as influenced by different ratios of roughage (rice straw) to concentrate in dairy steers

Abstract

SUMMARYThe current study was designed to determine the effect of roughage to concentrate ratio (R : C) on rumen pH, fermentation and bacterial population in dairy steers. Four rumen fistulated dairy steers (170±20 kg) were randomly assigned according to a 4×4 Latin square design, in which the steers were fed with four dietary treatments with different R : C ratios of 0·8 : 0·2, 0·6 : 0·4, 0·4 : 0·6 and 0·2 : 0·8, respectively. All animals were kept in individual pens and received feed according to the respective R : C ratios at 0·025 body weight (BW)/d; urea-treated rice straw (prepared using 3·5 kg urea+100 kg water sprayed onto 100 kg of rice straw) was used as a roughage source. The experiment was conducted for four periods of 21 days each. During the first 14 days, feed intake was measured and the animals were then moved to metabolism crates for total urine and faecal collection for 7 days. Total dry matter intake (DMI) was similar among treatments. Energy intake increased as the proportion of concentrate in the diet increased. Apparent digestibilities of dry matter (DM), organic matter (OM) and crude protein (CP) were improved, while neutral detergent fibre (NDF) and acid detergent fibre (ADF) were reduced when the levels of concentrate increased. A decreasing ratio of R : C reduced rumen pH linearly, from 6·4 to 5·9 at 0·2 : 0·8. High levels of concentrate impacted on volatile fatty acids (VFA) molar proportions and decreased acetate (C2) linearly, while propionate (C3) was increased, leading to decreased C2 : C3 ratio. Numbers of protozoa, fungi and proteolytic bacteria were not affected by R : C ratio. Cellulolytic bacteria decreased linearly while amylolytic bacteria increased linearly with 0·60 and 0·80 concentrates. Quantitative polymerase chain reaction (qPCR) based on 16S RNA revealed that Fibrobacter succinogenes numbers were increased when steers were fed with R : C ratio of 0·8 : 0·2. Conjugated linoleic acid (CLA)-producing bacteria, especially those of Butyrivibrio fibrisolvens, increased linearly with R : C ratios of 0·8 : 0·2 and 0·6 : 0·4, while Megasphaera elsdenii, a lactate-utilizing bacterium and reported producer of trans-10, cis-12 CLA increased linearly with R : C ratio of 0·8 : 0·2. In addition, microbial CP synthesis increased quadratically when steers were fed high levels of concentrate. However, the efficiency microbial N synthesis (EMNS) based on OM, truly digested in the rumen, was not affected by different R : C ratios. From the current study, it can be concluded that roughage to concentrate ratio of 0·4 : 0·6 had positive effects for the creation of healthy rumen (rumen pH and ecology), and improved energy intake and rumen fermentation, particularly propionic acid and microbial protein synthesis, in dairy steers fed urea-treated rice straw as a roughage source.

Effects of Antidesma thwaitesianum Muell. Arg. pomace as a source of plant secondary compounds on digestibility, rumen environment, hematology, and milk production in dairy cows

“…The ruminal NH 3 ‐N concentration increased after feeding (Gunun et al., ; Wanapat, Gunun, Anantasook, & Kang, ). The feeding of concentrate, roughage and protein supplements effects on ruminants is based on the knowledge that NH 3 is the major end‐product of protein degradation in the rumen, which appears to have been generally accepted, that most of the N utilized by rumen microbes comes from the NH 3 pool in the rumen (Supapong, Cherdthong, Seankamsorn, Khonkhaeng, Wanapat, Gunun, et al., 2017).…”

“…Ruminal fermentation products were affected by sampling time The ruminal NH 3 -N concentration increased after feeding Wanapat, Gunun, Anantasook, & Kang, 2014).…”

Effect of replacing alfalfa hay with a mixture of cassava foliage silage and sweet potato vine silage on ruminal and intestinal digestion in sheep

“…However, ruminal OM and NDF digestibility decreased with an increase in the CSP silage substitution. Furthermore, as an extrinsic factor, slightly lower pH at 6 h after feeding for the CSP diets may have reduced the population of ruminal fibrolytic bacteria and their attachment to feed particles (Wanapat et al 2014). Replacing AH with high moisture CSP silage may have increased passage rate of feed particles, which would consequently reduce ruminal fiber digestibility (Pasha et al 1994;Obitsu et al 2009).…”

“…Replacing AH with high moisture CSP silage may have increased passage rate of feed particles, which would consequently reduce ruminal fiber digestibility (Pasha et al 1994;Obitsu et al 2009). Furthermore, as an extrinsic factor, slightly lower pH at 6 h after feeding for the CSP diets may have reduced the population of ruminal fibrolytic bacteria and their attachment to feed particles (Wanapat et al 2014). However, such reduced ruminal NDF digestion for the CSP diets was compensated by the higher intestinal NDF digestion due to the entry of the potentially digestible NDF into the large intestine in sheep (Huhtanen & Vanhatalo 1997).…”

Effects of rumen-protected folic acid on ruminal fermentation, microbial enzyme activity, cellulolytic bacteria and urinary excretion of purine derivatives in growing beef steers

“…As the predominant cellulolytic bacteria in the rumen, R. albus, R. flavefaciens, F. succinogenes and B. fibrisolvens (Wanapat et al, 2014), whose adhesion and digestion ability to fibrous plant particles has been extensively studied over the last decade (Miron et al, 2001). The growth and multiplication of these ruminal cellulolytic bacteria contributes to secrete fibrolytic enzymes to digest fiber material.…”