Publications

The development of replacement heifers is crucial for breeding success and herd efficiency. Nutritional management can affect not only reproductive development but also the inflammatory status of the uterine environment, which may impact reproductive functions such as pregnancy establishment and development. The study herein evaluated the concentration of cytokines and chemokines in the uterus of heifers supplemented with different levels of protein. Angus heifers (n = 60) were blocked by body weight (BW) and randomly assigned to 1 of 3 treatments based on protein supplementation level: control of 10% crude protein (CON), 20% crude protein (P20), or 40% crude protein (P40). BW, body condition score, and blood samples were taken every 2 wk for 140 d to monitor development. Uterine flushes were performed monthly and concentrations of cytokines (IL-1α, IL-1β, TNF-α, IFN-γ, IL-10, VEGF-α, IL-17A, and IL-36RA) and chemokines (IL-8, MCP-1, MIP-1α, and MIP-1β) were quantified via ELISA multiplex. To test if there were mean differences in cytokines between the treatment groups or over time, PROC GLIMMIX (SAS v 9.4) was utilized. Concentrations of all cytokines and chemokines, except IL-1α, changed throughout heifer development (P < 0.05). Heifers in the P40 treatment group displayed reduced concentrations of MCP-1 (P = 0.007) and tended to have decreased concentrations of IFN-γ (P = 0.06). Cytokine IL-36RA tended (P = 0.06) to be affected by protein level, with the lowest concentrations observed in CON heifers. Most cytokines and chemokines increased following the initial month of supplementation (P < 0.05). The increase in concentrations after 1 mo may indicate an adaptive response in the uterus to diet change. Cytokines and chemokines fluctuated due to physiological changes occurring during development. Further research is needed to determine the influence of nutrition on uterine inflammation and long-term impacts on reproductive function.

Methane (CH4) gas released by cattle is a product of fermentation in the digestive tract. The 2 primary sites of CH4 production in ruminants are the reticulum-rumen complex and the cecum. Methane release from cattle represents a 2% to 12% loss of the energy intake. Reducing the proportion of feed energy lost as CH4 has the potential of improving feed efficiency as well as decreasing the contribution of cattle to greenhouse gas production. Feed intake and growth were measured on 132 fall-born steers for 70 d. Seven steers with extreme positive residual gain (RG) and 7 steers with extreme negative RG whose DMI was within 0.32 SD of the mean intake were selected for subsequent measurements. Enteric CH4 production was measured via indirect calorimetry. Rumen, cecum, and rectal contents were obtained from steers at slaughter for measurement of in vitro CH4 production and methanogen 16S rRNA levels. Enteric CH4 production did not differ (P = 0.11) between the positive RG (112 ± 13 L/d) and the negative RG (74 ± 13 L/d) steers. In vitro rumen methane production did not differ between positive RG (64.26 × 10−5 ± 10.85 × 10−5 mmol∙g−1 DM∙min−1) and negative RG (61.49 × 10−5 ± 10.85 × 10−5 mmol∙g−1 DM∙min−1; P = 0.86). In vitro cecum methane production did not differ between positive RG (4.24 × 10−5 ± 1.90 × 10−5 mmol∙g−1 DM∙min−1) and negative RG (4.35 × 10−5 ± 1.90 × 10−5 mmol∙g−1 DM∙min−1; P = 0.97). Methanogen 16S rRNA as a percentage of the total bacteria16S rRNA did not differ between RG groups (P = 0.18). The methanogen 16S rRNA as a percentage of rumen fluid total bacteria 16S rRNA (5.3% ± 3.1%) did not differ from the methanogen 16S rRNA as a percentage of cecum content total bacteria 16S rRNA (11.8% ± 3.1%; P = 0.14). The methanogen 16S rRNA as a percentage of the rectum content total bacteria 16S rRNA (0.7% ± 3.1%) was not different from the rumen content (P = 0.29) but was less than the cecum content (P = 0.01). Methanomicrobiales 16S rRNA as a percentage of total methanogen 16S rRNA did not differ across sample sites (P = 0.81); however, steers with positive RG (10.5% ± 1.6%) were more numerous than steers with negative RG (5.1% ± 1.6%; P = 0.02). Cattle that differ in RG at the same DMI do not differ in characteristics associated with CH4 production.

Improving beef production efficiency, sustainability, and food security is crucial for meeting the growing global demand for beef while minimizing environmental impact, conserving resources, ensuring economic viability, and promoting animal welfare. Beta-adrenergic agonists and dietary protein have been critical factors in beef cattle production. Beta-agonists enhance growth, improve feed efficiency, and influence carcass composition, while dietary protein provides the necessary nutrients for muscle development and overall health. A balanced approach to their use and incorporation into cattle diets can lead to more efficient and sustainable beef production. However, microbiome technologies play an increasingly important role in beef cattle production, particularly by optimizing rumen fermentation, enhancing nutrient utilization, supporting gut health, and enhancing feed efficiency. Therefore, optimizing rumen fermentation, diet, and growth-promoting technologies has the potential to increase energy capture and improve performance. This review addresses the interactions among beta-adrenergic agonists, protein level and source, and the ruminal microbiome. By adopting innovative technologies, sustainable practices, and responsible management strategies, the beef industry can contribute to a more secure and sustainable food future. Continued research and development in this field can lead to innovative solutions that benefit both producers and the environment.

The rumen microbiome is critical to nutrient utilization and feed efficiency in cattle. Consequently, the objective of this study was to identify microbial and biochemical factors in Angus steers affecting divergences in feed efficiency using 16S amplicon sequencing and untargeted metabolomics. Based on calculated average residual feed intake (RFI), steers were divided into high- and low-RFI groups. Features were ranked in relation to RFI through supervised machine learning on microbial and metabolite compositions. Residual feed intake was associated with several features of the bacterial community in the rumen. Decreased bacterial α- (P = 0.03) and β- diversity (P &lt; 0.001) was associated with Low-RFI steers. RFI was associated with several serum metabolites. Low-RFI steers had greater abundances of pantothenate (P = 0.02) based on fold change (high/low RFI). Machine learning on RFI was predictive of both rumen bacterial composition and serum metabolomic signature (AUC ≥ 0.7). Log-ratio proportions of the bacterial classes Flavobacteriia over Fusobacteriia were enriched in low-RFI steers (F = 6.8, P = 0.01). Reductions in Fusobacteriia and/or greater proportions of pantothenate-producing bacteria, such as Flavobacteriia, may result in improved nutrient utilization in low-RFI steers. Flavobacteriia and Pantothenate may potentially serve as novel biomarkers to predict or evaluate feed efficiency in Angus steers.

Short-read assembly MQ bin taxonomy. A tab-delimited text file that lists the taxonomic assignment of short-read assembly MQ bins as determined by the Blobtools/DIAMOND alignment pipeline. (GZ 49157 kb)

Local immune activity in the reproductive tract is crucial in the response to uterine diseases, normal reproductive functions, and establishing pregnancy. Few studies have evaluated the influence of the local immune environment of the reproductive tract on fertility outcomes. The objectives were to 1) evaluate reproductive cytokine concentrations in postpartum cows undergoing estrus synchronization followed by timed artificial insemination (TAI) and 2) correlate reproductive bacterial communities with cytokine concentrations. Angus cows (n = 20) were subjected to a 7-Day Co-Synch protocol with pre-synchronization beginning 21 days prior (d -21) to TAI (d 0). Uterine and vaginal flushes were collected on d -21 and -2. Pregnancy was determined by transrectal ultrasound on d 30. Bacterial community profiling and analyses were conducted targeting the V1 to V3 hypervariable regions of the 16S rRNA gene. Cytokine concentrations for interleukin (IL)-1b, IL-6, IL-10, and transforming growth factor beta (TGF-β) were determined by commercial ELISA kits. Concentration data were analyzed using PROC MIXED and correlations using Pearson correlation in SAS. No differences were detected in vaginal samples (P &amp;gt;0.05). No differences in IL-10 or IL-1b concentrations were detected in uterine samples (P &amp;gt;0.05). Uterine TGF-β concentrations were greater in resulting pregnant than non-pregnant cows (44.0 ± 13.4 pg/mL vs 14.7 ± 4.9 pg/mL; P = 0.05). Uterine TGF-β was negatively correlated with the relative abundance of genera Treponema (r = -0.668; P = 0.05) in resulting non-pregnant cows on d -21. Uterine IL-6 concentrations were greater in resulting non-pregnant than pregnant cows (198.7 ± 21.8 pg/mL vs 144.3 ± 16.1 pg/mL; P = 0.05). Uterine IL-6 and the relative abundance of genera Butyrivibrio were positively correlated (r = 0.742; P = 0.02) in resulting non-pregnant cows on d -21. These results suggest possible relationships between uterine bacterial communities and cytokines prior to TAI that may ultimately affect fertility outcomes in beef cattle.

Methane produced by cattle is one of the contributors of anthropogenic greenhouse gas. Methods to lessen methane emissions from cattle have been met with varying success; thus establishing consistent methods for decreasing methane production are imperative. Ferric iron may possibly act to decrease methane by acting as an alternative electron acceptor. The objective of this study was to assess the effect of ferric citrate on the rumen bacterial and archaeal communities and its impact on methane production. In this study, eight steers were used in a repeated Latin square design with 0, 250, 500 or 750 mg Fe/kg DM of ferric iron (as ferric citrate) in four different periods. Each period consisted of a 16 day adaptation period and 5 day sampling period. During each sampling period, methane production was measured, and rumen content was collected for bacterial and archaeal community analyses. Normally distributed data were analysed using a mixed model ANOVA using the GLIMMIX procedure of SAS, and non-normally distributed data were analysed in the same manner following ranking. Ferric citrate did not have any effect on bacterial community composition, methanogenic archaea nor methane production ( P &gt;0.05). Ferric citrate may not be a viable option to observe a ruminal response for decreases in enteric methane production.

Replacement heifer development is one of the most critical components in beef production. The composition of the ideal uterine environment could maximize fertility and reproductive efficiency. Our hypothesis was that protein supplementation would affect the uterine environment of beef heifers without inhibiting development or reproduction. To test the effects of dietary supplementation on these outcomes, a randomized complete block design with repeated measures was implemented. Angus heifers (n = 60) were blocked by body weight (BW) and randomly assigned to one of three supplemental protein treatment groups (10% (CON), 20% (P20), and 40% (P40)). Mixed model ANOVAs were used to determine whether protein supplementation treatments, time, and the interaction or protein supplementation, semen exposure, and the interaction influenced uterine luminal fluid (ULF) and pregnancy outcomes. Amino acids (AAs) were impacted (p < 0.001), specifically, the essential AAs: Arg, Iso, Leu, Val, His, Lys, Met, Phe, Trp. Protein supplementation influenced multiple AAs post-insemination: Arg (p = 0.03), CC (p = 0.05), 1-MH (p = 0.001), and Orn (p = 0.03). In conclusion, protein supplementation did not affect the reproductive development via puberty attainment or the timing of conception even with alterations in growth. However, uterine AA concentrations did change throughout development and protein supplementation influenced ULF d 14 post-insemination, which may affect the conception rates.