Automated head chamber systems (AHCS) are increasingly deployed to measure enteric emissions in vivo. However, guidance for AHCS-derived emissions data analyses pertains to confined settings, such as feedlots, with less instruction for grazing systems. Accordingly, our first objective in this experiment was to determine the utility of two data preprocessing approaches for grazing-based analyses. Using Pearson’s correlation, we compared “simple arithmetic” and “time-bin” averaging to arrive at a single estimate of daily gas flux. For our second objective, we evaluated test period length averaging at 1, 3, 7, and 14 d intervals to determine daily pasture-based emissions estimates under two experimental conditions: herd access to a single AHCS unit vs. two AHCS units. Unlike findings from the confinement-based literature, where slight improvements have been observed, time-bin averaging, compared to simple arithmetic averaging, did not improve gas flux estimation from grazing for CH₄ (p ≥ 0.46) or CO₂ (p ≥ 0.60). Irrespective of experimental condition, i.e., herd access to a single AHCS unit vs. two AHCS units, assessment of variability of diurnal emissions patterns revealed CH₄ flux on pasture had at least half as much variability for the same individuals acclimated in confinement. Using a 7-day test period length interval, aggregating gas flux data at 7 d at a time was adequate for capturing diurnal emissions variation in grazing steers, as no improvement was observed in the percentage of individuals with five of six time bins measured for a 14-day test period length interval. This analysis should provide insights into future research to standardize AHCS data preprocessing across experiments and research groups.

Accurate estimation of enteric CH₄ emissions (i.e., MJ or g of CH₄/ day) in the ruminant sector is necessary for properly determining greenhouse gas emissions and developing measuring, reporting, and verification programs. However, measuring enteric CH₄ emissions under commercial conditions presents challenges due to technical and economic constraints. Thus, using prediction models allows for estimating individual enteric CH₄ emissions according to animal and dietary characteristics. When evaluated in independent datasets, there is limited information regarding the accuracy and precision of the reported equations to predict enteric CH₄ emissions in steers fed a finishing diet. This study evaluated the predictive performance of various reported equations for estimating enteric CH₄ production in finishing steers. Data used to assess the prediction equations came from 446 steers from five experiments during the finishing phase. Gas flux, nutrient consumption, and animal growth performance were evaluated in each experiment. Seventy-two equations were compared based on the mean square prediction error (MSPE), the decomposition of the root MSPE (RMSPE), and the concordance correlation coefficient (CCC). Prediction equations for estimating enteric CH₄ emissions showed lower sensitivity with RMSPE (as a percentage of the observed mean) ranging from 17.79 to 99.21 and CCC ranging from -0.07 to 0.21. The decomposition of the RMSPE showed mean bias (as a percentage of the RMSPE) ranging from 0.14 to 94.87 and slope bias (as a percentage of the RMSPE) ranging from 0 to 25.24. In addition, 49 equations underpredicted (ranging from 0.6 to 50.1%) and 23 overpredicted (ranging from 3.7 to 96.1%) enteric CH₄ emissions. The prediction of enteric CH₄ production showed greater CCC and lower MSPE when the intake of DM and ether extract were included as predictors. These results suggest a limited ability to predict enteric CH₄ by steers during the finishing phase. Further efforts are required to generate sensitive models to accurately predict enteric CH₄ emissions in finishing steers.

Heat stress (HS) induced by global warming is a real welfare, productivity, and economic burden of cattle production. However, some cattle breeds have superior physiological adaptive traits to others, yet the underlying molecular mechanisms are not fully defined. The present study aimed, therefore, to determine the expression profile of stress-related molecular signatures in the blood of thermosensitive Angus (Bos taurus) and thermotolerant Brahman (Bos indicus) cattle breeds managed without (CON) or with growth-promoting technology (TRT) during the summer (April–October, 2023) season in Colorado, US. Body weight (BW) was significantly increased from April to October, and the amplitude was greater for the Angus compared to the Brahman breed. The TRT system slightly increased BW, mainly in the Angus breed. Molecular analyses showed that all tested genes were expressed in beef cattle blood. When comparing production systems, the expression of HSP1A1 was significantly upregulated, and HSP90 was downregulated in CON compared to TRT cattle. The expression of IL6, CCL20, and OCLN was induced by the CON system only in the Angus and not in the Brahman breed. At the breed level, Angus cattle exhibited greater expression of IL10, CCL20, and CLDN1 compared to their Brahman counterparts. There was a significant period by production system as well as period by breed interactions. The expression of HSP1A1 increased in both breeds during October. The expression of IL10, CXCL14, CXCR2, and CLDN1 was affected by the production systems in a period-dependent manner. However, the expression of IL6, CXCL14, CCL5, and CXCR2 was upregulated in Angus cattle in a period-sensitive manner. In summary, HSPs, (chemo)cytokines, and tight junction proteins are expressed in the whole blood of beef cattle, and their expression is regulated in a breed-, period-, and/or production system-dependent manner. This could open new vistas for future research to identify molecular signatures for non-invasive stress monitoring and/or marker-assisted genetic selection for robustness and resilience to HS.

Context: The crossbreeding of Bos taurus taurus × Bos taurus indicus cattle has become a valuable alternative for improving performance and carcass quality. In addition, the production system adopted and the diets provided cannot only improve animal performance but also generate a product with characteristics that are more attractive to consumers. Aims: The objectives of this study were to evaluate the dry-matter intake, performance, and meat quality of Nellore (purebred, NEL) and crossbred (Angus vs Nellore, AN) bulls fed with two levels of concentrate (65 and 85%). Methods: Forty-eight young bulls of similar age (18 ± 2 months) were separated in the following four groups on the basis of breed and diet: Group 1: NEL 65% (n = 12; initial bodyweight (IBW): 415.66 kg ± 21.82 kg); Group 2: NEL 85% (n = 11; IBW 416.23 kg ± 21.96 kg); Group 3: AN 65% (n = 12; IBW 458.13 kg ± 24.59 kg); and Group 4: AN 85% (n = 13; IBW 463.54 kg ± 26.06 kg). The young bulls stayed on trial for 105 days (21 days for adaptation and 84 finishing) and were all slaughtered at the same time. Key results: The crossbred animals showed greater average bodyweight, average daily gain, hot carcass weight, and average daily gain in carcass. There was no difference between breed or diet (P > 0.05) in dry-matter intake (DMI). The diet or breed did not affect the tenderness but did affect the color. Conclusions: Even though there was no difference between breeds in the DMI, crossbred animals presented better performance than did Nellore animals. Both breeds showed a lighter-color meat, although the meat of crossbred animals was lighter, in both diets, than was that of the NEL fed 85% diet. Moreover, the use of crossbreed Angus × Nellore is a valuable strategy to improve performance and meat quality in a tropical area. Implications: The superior growth performance and hot carcass weight of crossbred animals support crossbreeding as a strategy to improve beef production efficiency. Nellore animals’ meat was as tender as that of crossbred animals, which might be associated with a greater presence of proteolytic enzymes in the AN carcass owing to a genetic presence of Bos indicus in the evaluated F1 AN animals, resulting in no breed differences. However, diet and breed influenced meat color, a trait associated with favorable consumer perception, where AN animals presented a lighter meat. These findings suggest that performance can be achieved alongside desirable quality attributes. However, future research may search for a crossbreeding threshold level for meat tenderness.