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.

The objective of this study was to determine the roughage to concentrate (R:C) ratio with rain tree pod meal (RPM) supplementation on in vitro fermentation using gas production technique. The experiment design was a 6×4 factorial arrangement in a CRD. Factor A was 6 levels of R:C ratio (100:0, 80:20, 60:40, 40:60, 20:80 and 0:100) and factor B was 4 levels of RPM (0, 4, 8 and 12 mg). It was found that gas kinetic, extent rate (c) was linearly increased (p<0.01) with an increasing level of concentrate while cumulative gas production (96 h) was higher in R:C of 40:60. In addition, interaction of R:C ratio and RPM level affected NH3-N and IVDMD and were highest in R:C of 0:100 with 0, 4 mg of RPM and 40:60 with 8 mg of RPM, respectively. Moreover, interaction of R:C ratio and RPM level significantly increased total volatile fatty acids and propionate concentration whereas lower acetate, acetate to propionate ratios and CH4 production in R:C of 20:80 with 8 mg of RPM. Moreover, the two factors, R:C ratio and RPM level influenced the protozoal population and the percentage of methanogens in the total bacteria population. In addition, the use of real-time PCR found that a high level of concentrate in the diet remarkably decreased three cellulolytic bacteria numbers (F. succinogenes, R. flavefaciens and R. albus). Based on this study, it is suggested that the ratio of R:C at 40:60 and RPM level at 12 mg could improve ruminal fluid fermentation in terms of reducing fermentation losses, thus improving VFA profiles and ruminal ecology.

This study was designed to determine the effect of physical form and urea treatment of rice straw on rumen fermentation, microbial protein synthesis and nutrient digestibility. Four rumen-fistulated dairy steers were randomly assigned according to a 2 (2 factorial arrangement in a 4 (4 Latin square design to receive four dietary treatments. Factor A was roughage source: untreated rice straw (RS) and urea-treated (3%) rice straw (UTRS), and factor B was type of physical form of rice straw: long form rice straw (LFR) and chopped (4 cm) rice straw (CHR). The steers were offered the concentrate at 0.5% body weight (BW) /d and rice straw was fed ad libitum. DM intake and nutrient digestibility were increased (p<0.05) by urea treatment. Ruminal pH were decreased (p<0.05) in UTRS fed group, while ruminal ammonia nitrogen (NH3-N) and blood urea nitrogen (BUN) were increased (p<0.01) by urea treatment. Total volatile fatty acid (VFA) concentrations increased (p<0.01) when steers were fed UTRS. Furthermore, VFA concentrations were not altered by treatments (p>0.05), except propionic acid (C3) was increased (p<0.05) in UTRS fed group. Nitrogen (N) balance was affected by urea treatment (p<0.05). Microbial protein synthesis (MCP) synthesis were greater by UTRS and CHR group (p<0.05). The efficiency of microbial N synthesis was greater for UTRS than for RS (p<0.05). From these results, it can be concluded that using the long form combined with urea treatment of rice straw improved feed intake, digestibility, rumen fermentation and efficiency of microbial N synthesis in crossbred dairy steers.

The objective of this study was to investigate the effects of tannins and saponins in Samanea saman on rumen fermentation, milk yield and milk composition in lactating dairy cows. Four multiparous early-lactating dairy cows (Holstein-Friesian cross-bred, 75%) with an initial body weight (BW) of 405 ± 40 kg and 36 ± 8 day in milk were randomly assigned to receive dietary treatments according to a 4 × 4 Latin square design. The four dietary treatments were unsupplemented (control), supplemented with rain tree pod (S. saman) meal (RPM) at 60 g/kg, supplemented with palm oil (PO) at 20 g/kg, and supplemented with RPM at 60 g/kg and PO at 20 g/kg (RPO), of total dry matter (DM) intake. Cows were fed with concentrate diets at a ratio of concentrate to milk yield of 1:2, and chopped 30 g/kg of urea-treated rice straw was fed ad libitum. The RPM contained condensed tannins and crude saponins at 88 and 141 g/kg of DM respectively. It was found that supplementation with RPM and/or PO to dairy cows diets did not show negative effect on ruminal pH, blood urea nitrogen and milk urea nitrogen concentration (p > 0.05). However, supplementation with RPM resulted in lower ammonia nitrogen (NH3 -N) concentration (p < 0.05). In addition, propionic acid and milk production increased while acetic acid, acetic to propionic ratio, methane production, methanogens and protozoal population decreased with RPM and/or PO supplementation. Furthermore, addition of PO and RPO in the diets increased milk fat while supplementation of RPM resulted in greater milk protein and Fibrobacter succinogenes numbers (p < 0.05). The population of Ruminococcus flavefaciens and Ruminococcus albus were not affected by any treatments. The findings on the present study showed that supplementation with RPM and RPO to diets of cows improved the rumen environment and increased milk yield, content of milk protein and milk fat.