An updated meta-analysis of the anti-methanogenic effects of monensin in beef cattle.

Meta-analyses were performed to quantitatively summarize the effects of monensin on in vivo methane (CH4) production in beef cattle, and differentiate these outcomes according to dietary management, dose of monensin, and length of monensin supplementation. Data from 11 manuscripts describing 20 individual studies were used, and CH4 was converted to g/d when required. Studies were classified according to dose of monensin (mg/kg of diet dry matter), length of monensin supplementation prior to the last CH4 measurement, feeding management (ad libitum vs. limited-fed), and diet profile (high-forage or high-concentrate diets). Variance among studies were assessed using a χ² test of heterogeneity and calculated using I² statistics. The inclusion of monensin decreased (P < 0.01) CH4 production by 17.5 g/d when all studies were analyzed together. A moderate (P < 0.01) heterogeneity (I²â€…= 55%) was detected for CH4 production estimates between studies; thus, meta-analyses were performed within classes. The reduction in CH4 differed (P < 0.01) according to dose of monensin, as it decreased (P < 0.01) by 25.6 g/d when the high recommended dose range was used (32 to 44 mg/kg), and tended to decrease (P ≤ 0.07) by 9.7 and 13.5 g/d when the moderate (≤31 mg/kg) and above recommended (≥45 mg/kg) doses were used, respectively. The reduction in CH4 also differed (P < 0.01) according to the length of monensin supplementation. Monensin decreased (P ≤ 0.05) CH4 production by 24.3 g/d when supplemented for <15 d, by 15.4 g/d when supplemented from 23 to 33 d, by 24.3 g/d when supplemented from 52 to 79 d, and tended to decrease (P = 0.06) CH4 production by 3.21 g/d when supplemented from 94 to 161 d. The reduction in CH4 did not differ (P = 0.37) according to diet profile, despite a 30% difference in reduction when monensin was added to high-forage (20.89 g/d) compared with high-concentrate diets (14.6 g/d). The reduction in CH4 tended to differ according to feeding management (P = 0.08), decreasing by 22.9 g/d (P < 0.01) when monensin was added to diets offered ad libitum, and by 11.5 g/d (P = 0.05) in limit-fed diets. Collectively, this study provides novel insights and further corroborates monensin as CH4 mitigation strategy in beef cattle operations. The most effective responses were observed during the first 79 d of monensin supplementation, and when monensin was included between 32 to 44 mg/kg of diet, was added to high-forage diets, and added to diets fed ad libitum.

Genomic structure and marker-derived gene networks for growth and meat quality traits of Brazilian Nelore beef cattle.

BACKGROUND: Nelore is the major beef cattle breed in Brazil with more than 130 million heads. Genome-wide association studies (GWAS) are often used to associate markers and genomic regions to growth and meat quality traits that can be used to assist selection programs. An alternative methodology to traditional GWAS that involves the construction of gene network interactions, derived from results of several GWAS is the AWM (Association Weight Matrices)/PCIT (Partial Correlation and Information Theory). With the aim of evaluating the genetic architecture of Brazilian Nelore cattle, we used high-density SNP genotyping data (~770,000 SNP) from 780 Nelore animals comprising 34 half-sibling families derived from highly disseminated and unrelated sires from across Brazil. The AWM/PCIT methodology was employed to evaluate the genes that participate in a series of eight phenotypes related to growth and meat quality obtained from this Nelore sample. RESULTS: Our results indicate a lack of structuring between the individuals studied since principal component analyses were not able to differentiate families by its sires or by its ancestral lineages. The application of the AWM/PCIT methodology revealed a trio of transcription factors (comprising VDR, LHX9 and ZEB1) which in combination connected 66 genes through 359 edges and whose biological functions were inspected, some revealing to participate in biological growth processes in literature searches. CONCLUSIONS: The diversity of the Nelore sample studied is not high enough to differentiate among families neither by sires nor by using the available ancestral lineage information. The gene networks constructed from the AWM/PCIT methodology were a useful alternative in characterizing genes and gene networks that were allegedly influential in growth and meat quality traits in Nelore cattle.

Identification of KCNJ11 as a functional candidate gene for bovine meat tenderness.

The potassium inwardly rectifying channel, subfamily J, member 11 (KCNJ11) gene was investigated as a candidate for meat tenderness based on the effects reported on muscle for KCNJ11 gene knockout in rat models and its position in a quantitative trait locus (QTL) for meat tenderness in the bovine genome. Sequence variations in the KCNJ11 gene were described by sequencing six amplified fragments, covering almost the entire gene. We identified single nucleotide polymorphisms (SNP) and validated them by different approaches, taking advantage of simultaneous projects that are being developed with the same Nelore population. By sequencing the KCNJ11 in Nelore steers representing extreme phenotypes for Warner-Bratzler shear force (WBSF), it was possible to identify 22 SNPs. We validated two of the identified markers by genotyping the whole population (n = 460). Analysis of association between genotypes and WBSF values revealed a significant additive effect of a SNP at different meat aging times (P ≤ 0.05). In addition, an association between the expression levels of KCNJ11 and WBSF was found, with lower expression levels of KCNJ11 associated with more tender meat (P ≤ 0.05). The results showed that the KCNJ11 gene is a candidate mapped to a QTL for meat tenderness previously identified on BTA15 and may be useful to identify animals with genetic potential to produce tender meat. The effect of KCNJ11 observed on muscle is potentially due to changes in activity of KATP channels, which in turn influence the flow of potassium in the intracellular space, allowing establishment of the membrane potential necessary for muscle contraction.