Effect of different levels of concentrate on ruminal microorganisms and rumen fermentation in Nellore steers

Abstract

The aim of this study was to investigate the effect of different dietary levels of concentrate on feed intake, digestibility, ruminal fermentation and microbial population in steers. Eight Nellore steers fitted with ruminal cannulas were used in a double 4 × 4 Latin square design experiment. The dietary treatments consist of four different proportions of concentrate to roughage: 30:70, 40:60, 60:40 and 80:20% in the dry matter, resulting in Diets 30, 40, 60 and 80, respectively. The roughage was corn silage, and the concentrate was composed of corn, soybean meal and urea. Apparent digestibility of organic matter and crude protein showed a linear association with concentrate proportion (p = 0.01), but the increased concentrate levels did not affect the digestibility of fibre. The lowest ruminal pH-values were observed in animals fed with Diet 80, remaining below pH 6.0 from 6 h after feeding, while in the other diets, the ruminal pH was below 6.0 not before 12 h after feeding. After feeding Diet 80, the ammonia concentration in the rumen was significantly the highest. Higher dietary concentrate levels resulted in a linear increase of propionic acid concentrations, a linear reduction of the ratio acetic acid to propionic acid (p < 0.01) and a linear increased synthesis of microbial nitrogen (p < 0.001). The predicted production of methane was lower in diets with greater amounts of concentrate (p = 0.032). The population of methanogens, R. flavefaciens and R. albus decreased with higher concentrate levels, while the population of S. ruminantium increased (p < 0.05). The results indicate that greater amounts of concentrate do not decrease ruminal pH-values as much as expected and inhibit some cellulolytic bacteria without impairing the dry matter intake and fibre digestibility in Nellore steers.

Effects of different forage combinations in total mixed rations on in vitro gas production kinetics, ruminal and milk fatty acid profiles of lactating cows

“…In the present study, NDF:NFC was 0.77, 1.01 and 1.07 for TMR1, 2 and 3 of different forage combinations, and lower acetate and greater propionate in the rumen were found for TMR1 with forage combinations of alfalfa hay, Chinese wild ryegrass hay and whole corn silage than those for TMR2 and TMR3 containing corn stover and rice straw, respectively. The results were consistent with a previous study which showed that lower acetate and greater propionate occurred in the rumen of ruminants fed lower NDF:NFC diet than those with greater NDF:NFC diet (Granja‐Salcedo et al., ; Sievert & Shaver, ). Differences among TMR1–3 in the present study were observed in volatile fatty acid content, suggesting that even and odd chain volatile fatty acid contents in the rumen fluid depended on the different forage combinations under the same ratio of concentrate to forage in TMRs.…”

“…In the present study, NDF:NFC was 0.77, 1.01 and 1.07 for TMR1, 2 and 3 of different forage combinations, and lower acetate and greater propionate in the rumen were found for TMR1 with forage combinations of alfalfa hay, Chinese wild ryegrass hay and whole corn silage than those for TMR2 and TMR3 containing corn stover and rice straw, respectively. The results were consistent with a previous study which showed that lower acetate and greater propionate occurred in the rumen of ruminants fed lower NDF:NFC diet than those with greater NDF:NFC diet (Granja-Salcedo et al, 2016;Sievert & Shaver, 1993). Differences among TMR1-3 in the present study were observed in volatile fatty acid content, suggesting that TFA (total fatty acid in milk) = C8:0 + C10:0 + C12:0 + C14:0 + C14:1 cis-9 + C16:0 + C16:1 cis-9 + C18:0 + C18:1 trans-11 + C18:1 cis-9 + C18:2n-6 + C18:3n-3 + C20:0 + C20:3n-6 + C20:4n-6 + C22:0; UFA (unsaturated fatty acid) = C14:1 cis-9 + C16:1 cis-9 + C18:1 trans-11 + C18:1 cis-9 + C18:2n-6 + C18:3n-3 + C20:3n-6 + C20:4n-6; SFA (saturated fatty acid) = C8:0 + C10:0 + C12:0 + C14:0 + C16:0 + C18:0 + C20:0 + C22:0; SEM, standard error of least square means; DMI, dry matter intake.…”

The Effect of Live Yeast Supplementation on Beef Cattle Performance: A Systematic Review and Meta-Analysis

“…In high-concentrate diets, the protozoa population is reduced because it is very sensitive to the fluctuations and decreases in ruminal pH (Granja-Salcedo et al, 2016). Thus, the benefits of yeast are not observed (i.e., protozoa population growth; Arakaki, Stahringer, Garrett, & Dehority, 2010) because of the changes in the starch and lactate intakes by protozoa (Kozloski, 2011).…”

Effect of sugarcane fiber digestibility, conservation method and concentrate level on the ruminal ecosystem of beef cattle

“…Moreover, the relative abundance of the Streptococcaceae and Veillonellaceae families was increased when heifers received fructose. Other studies found similar results, where the population of S. bovis was not increased with the increment of concentrate in the diet of Nellore steers, using corn silage as the roughage source (Granja-Salcedo et al 2016) or freshly-cut sugarcane (Ribeiro Junior et al 2016). Sun et al (2015) report an increase of S. bovis population by replacing cornstarch in a high-concentrate diet (forage to concentrate ratio = 40:60) with 3% sucrose after 24 h in vitro incubation.…”

“…The substitution of roughage for concentrate, rich in rapidly fermentable carbohydrates, promoted a decline in particle size of the diet, with less physically effective NDF, reducing salivation and rumen motility and, consequently, rumen buffering. Several other studies demonstrate the reduction in cellulolytic bacteria due to the increase in concentrate in the diet (Tajima et al 2001; Singh et al 2014; Granja-Salcedo et al 2016). …”