The activity of the calpains/calpastatin proteolytic system is closely related to the postmortem tenderization of meat. We investigated the association between beef tenderness and single nucleotide polymorphism (SNP) markers on the CAPN1 gene (SNP316, alleles C/G; SNP530 alleles A/G) and the CAST gene 3' untranslated region (SNP2870, alleles A/G). We sampled nine slaughter groups comprising 313 steers which had been reared in beef production systems in Argentina between 2002 and 2004 from crosses between Angus, Hereford and Limousin cattle. Minor allele frequencies for the markers were 0.27 to 0.46 (C), 0.02 to 0.18 (A), and 0.24 to 0.53 (A), respectively. The presence of CAPN1 markers had significant effects on meat shear force but no detectable effects were demonstrated for the CAST marker. The shear force of meat from steers with the SNP316 CC genotype was 11% lower than for the SNP316 CG genotype and 17% lower than for the SNP316 GG genotype. There were very few steers with the SNP530 AA genotype and, contrary to previous studies, meat from steers with the SNP530 GG genotype showed an 11.5% higher shear force than that from steers with the SNP530 GA genotype. Final body weight, carcass weight and rib eye area were not affected by any of the markers. These results support the concept that CAPN1 variants are associated with tenderness across a wide range of beef production systems.

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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 (H2S) by sulfo‐reducing ruminal bacteria (SRB), being high ruminal H2S concentration responsible for aforementioned damages. As the ruminal mechanisms involved in H2S concentrations increase have not been elucidated, this study aimed to evaluate the ruminal environment, and the association between ruminal H2S 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 H2S concentration, and ruminal fluid to determine total bacteria, DSRB, protozoa, volatile fatty acid and ammonia nitrogen concentration. For ruminal H2S 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 H2S and DSRB concentrations was observed. The ruminal adaptation that maximizes H2S 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.

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.