Llama and sheep ruminal fluid digestive capacity by in vitro gas production technique.

BACKGROUND: The in vitro gas production technique has been used to evaluate forage fermentation kinetics. However, individual and animal species variation can change fermentation patterns due to differences in ruminal environment and microbiota. The aim was to verify whether rumen inoculum (RI) of llama had superior intrinsic digestion capacity and reduced methane (CH4 ) production compared to sheep RI using fescue and paspalum hay as substrates. RESULTS: Dry and organic matter (OM) digestibility produced with llama RI tended to exceed that of sheep (P = 0.099 and 0.074, respectively) at 24 h of incubation. However, at 48 h, the sheep RI presented higher substrate digestibility and asymptotic value of gas production than that of llama (P < 0.010). CH4 production showed no differences between RI or substrates (P > 0.050). The NH3 -N and total volatile fatty acid concentrations were greater in the RI of llamas compared to those of sheep (P < 0.050). Acetate and butyrate proportions and acetate-to-propionate ratio were greater in the RI of llamas compared to those of sheep (P < 0.001) at 24 and 48 h. However, propionate proportion was greater in sheep compared with llama (P < 0.001). CONCLUSION: Llama RI tended to surpass that of sheep in dry and OM digestibility at 24 h of incubation, but sheep RI at 48 h presented a higher digestibility and gas production value than llama RI. No differences between the two species were detected for CH4 production. This study showed that llama RI did not perform better than sheep RI in digesting low-quality forages. © 2022 Society of Chemical Industry.

Ruminal effects of excessive dietary sulphur in feedlot cattle.

Sulphur (S) dietary excess can limit productive performance and increase polioencephalomalacia (PEM) incidence in feedlot cattle (FC). Sulphur excess ingested is transformed to hydrogen sulphide (H2 S) by sulfo-reducing ruminal bacteria (SRB), being high ruminal H2 S concentration responsible for aforementioned damages. As the ruminal mechanisms involved in H2 S concentrations increase have not been elucidated, this study aimed to evaluate the ruminal environment, and the association between ruminal H2 S and dissimilatory SRB (DSRB) concentration in FC experimentally subjected to S dietary excess. Twelve crossbred steers were randomly assigned to one of two dietary S levels (6 animals per treatment): low (LS, 0.19% S) and high (HS, 0.39% S obtained by sodium sulfate inclusion at 0.86%). The study lasted 38 days, and on days 0, 22 and 38, ruminal gas samples were taken to quantify H2 S concentration, and ruminal fluid to determine total bacteria, DSRB, protozoa, volatile fatty acid and ammonia nitrogen concentration. For ruminal H2 S concentration, S dietary × sampling day interaction was significant (p < 0.001), so that the greater concentration was observed on days 22 and 38 with the HS diet. The remaining ruminal parameters were not affected by dietary S level, and no significant correlation between H2 S and DSRB concentrations was observed. The ruminal adaptation that maximizes H2 S production in FC consuming S excess does not seem to be associated with biological or biochemical alterations, nor DSRB concentration changes. The microbial diversity and ruminal environment were resilient to the S excess evaluated, suggesting that 0.39% of dietary S achieved by 0.86% sodium sulfate addition, could be used without disturbances on digestion nor health of FC.

Dynamics of the ruminal microbial ecosystem, and inhibition of methanogenesis and propiogenesis in response to nitrate feeding to Holstein calves.

It is known that nitrate inhibits ruminal methanogenesis, mainly through competition with hydrogenotrophic methanogens for available hydrogen (H2) and also through toxic effects on the methanogens. However, there is limited knowledge about its effects on the others members of ruminal microbiota and their metabolites. In this study, we investigated the effects of dietary nitrate inclusion on enteric methane (CH4) emission, temporal changes in ruminal microbiota, and fermentation in Holstein calves. Eighteen animals were maintained in individual pens for 45 d. Animals were randomly allocated to either a control (CTR) or nitrate (NIT, containing 15 g of calcium nitrate/kg dry matter) diets. Methane emissions were estimated using the sulfur hexafluoride (SF6) tracer method. Ruminal microbiota changes and ruminal fermentation were evaluated at 0, 4, and 8 h post-feeding. In this study, feed dry matter intake (DMI) did not differ between dietary treatments (P > 0.05). Diets containing NIT reduced CH4 emissions by 27% (g/d) and yield by 21% (g/kg DMI) compared to the CTR (P < 0.05). The pH values and total volatile fatty acids (VFA) concentration did not differ between dietary treatments (P > 0.05) but differed with time, and post-feeding (P < 0.05). Increases in the concentrations of ruminal ammonia nitrogen (NH3-N) and acetate were observed, whereas propionate decreased at 4 h post-feeding with the NIT diet (P < 0.05). Feeding the NIT diet reduced the populations of total bacteria, total methanogens, Ruminococcus albus and Ruminococcus flavefaciens, and the abundance of Succiniclasticum, Coprococcus, Treponema, Shuttlewortia, Succinivibrio, Sharpea, Pseudobutyrivibrio, and Selenomona (P < 0.05); whereas, the population of total fungi, protozoa, Fibrobacter succinogenes, Atopobium and Erysipelotrichaceae L7A_E11 increased (P < 0.05). In conclusion, feeding nitrate reduces enteric CH4 emissions and the methanogens population, whereas it decreases the propionate concentration and the abundance of bacteria involved in the succinate and acrylate pathways. Despite the altered fermentation profile and ruminal microbiota, DMI was not influenced by dietary nitrate. These findings suggest that nitrate has a predominantly direct effect on the reduction of methanogenesis and propionate synthesis.

Changes in hematological, biochemical, and blood gases parameters in response to progressive inclusion of nitrate in the diet of Holstein calves.

BACKGROUND AND AIM: Nitrate (NO3 -) reduces enteric methane emissions and could be a source of non-protein nitrogen in ruminant feeds. Nonetheless, it has a potential toxic effect that could compromise animal health and production. The purpose of this study was to determine the effects of progressive inclusion of NO3 - in the diet on the hematological, biochemical, and blood gases parameters, in turn, the effects on feed intake and live weight gain (LWG) in Holstein calves. MATERIALS AND METHODS: Eighteen Holstein heifers and steers (nine animals/treatment) were maintained in individual pens for 45 days. Animals were randomly allocated to either a control or nitrate diet (ND) (containing 15 g of NO3 -/kg of dry matter [DM]). The biochemical parameters and blood gases were analyzed only in the NO3 - group on days: -1, 1, 7, 13, 19, and 25 corresponding to 0, 20, 40, 60, 80, and 100% of the total inclusion of NO3 - in the diet, respectively. In addition, DM intake (DMI) and LWG were evaluated among dietary treatments. RESULTS: Feeding the ND did not influence DMI or LWG (p>0.05). Methemoglobin (MetHb) and deoxyhemoglobin increased according to the NO3 - concentrations in the diet (p<0.05), while an opposite effect was observed for oxyhemoglobin and carboxyhemoglobin (p<0.05). Hematocrit levels decreased (p<0.05), while albumin, alanine aminotransferase, and gamma-glutamyl transpeptidase concentrations were not modified (p>0.05). However, glucose, urea, aspartate aminotransferase (AST), and retinol concentrations increased (p<0.05) according to the NO3 - concentrations in the diet. CONCLUSION: This study confirmed that the progressive inclusion of 123 g of NO3 -/animal/day in the diet could be safe without affecting DMI and LWG of Holstein calves. In turn, a dose-response effect of the MetHb, glucose, urea, AST, and retinol was observed, but these values did not exceed reference values. These results highlighted the importance of using a scheme of progressive inclusion of NO3 - in the diet of calves to reduce the risks of NO3 - toxicity.