Search Results (151)

Early diagnosis of heat load in beef cattle remains a challenge due to the limited understanding of behaviour-based indicators. This preliminary longitudinal study aimed to validate behavioural and physiological responses previously identified as heat load indicators. Black Angus steers were exposed to high environmental temperatures expected to cause heat load in the following sequence: an initial thermoneutral period, a hot period, and a recovery period. Changes in the positioning of key body parts, feeding behaviour, body maintenance, respiratory dynamics, and eye temperature were monitored. In the hot period, cattle increased their respiration rate, panting, and infrared eye temperature. Increased stepping by their left limbs suggested involvement of the right brain hemisphere in a stress response to high environmental temperatures. Cattle also held their heads more downward, ears backward, and their tail vertical, and reduced eating, grooming, and scratching during the hot period. Cattle responses to hot conditions were persistent in the recovery period, reflecting diagnostic relevance of the head, ear, and tail movements, stepping, especially by left limbs, and infrared eye temperature as non-invasive tools to identify heat load condition in cattle. The study reinforces our understanding of the specific behavioural and physiological responses to heat load condition, especially those involving left-limb stepping, ear and tail posture, and infrared eye temperature, are reliable indicators for identifying cattle experiencing high environmental temperature. Full article

Integrated crop grazing systems can improve farm profitability due to enterprise complementarity. Utilizing the supply of N from legumes, livestock manure, and plant residues will result in improving grain yield and quality. A long-term 12-year integrated systems study evaluated continuous spring wheat (HRSW-CTRL) with spring wheat (HRSW-ROT) grown in a five-crop rotation: (1) spring wheat, (2) seven-species cover crop, (3) forage corn, (4) field pea/forage barley mix, and (5) sunflower. Yearling beef cattle steers grazed the field pea/forage barley mix, unharvested corn, and a seven-species cover crop. Spring wheat was marketed as a cash crop. Contrary to expectations, HRSW-ROT did not significantly increase grain yield or improve quality over HRSW-CTRL. Improved soil fertility was observed in the HRSW-ROT plots throughout the study relative to SOM, N, P, and K. However, the rotation with grazing management significantly reduced input costs but resulted in negligible gross and net returns over the 12-year period. Year-to-year weather variability was the cause of the differences between the two production management methods. Full article

Thymol is an antimicrobial terpene with potential as a feed additive for cattle; however, in vivo data describing the response of forage-fed beef cattle to the increasing provision of thymol is limited. As thymol may affect palatability and exert antimicrobial effects on rumen microbes, defining its effects in vivo is critical to inform adoption. Accordingly, the objectives of this study were to evaluate cattle acceptance of thymol and characterize the effects of increasing thymol doses on diet utilization and ruminal fermentation, with the overarching goal of identifying a maximum tolerable dose for beef cattle. Two 4 × 4 Latin Square experiments were conducted using beef steers consuming forage and providing thymol dosed on alfalfa. Experiment 1 assessed acceptance of thymol at increasing concentrations (0, 110, 220, and 330 mg/kg intake), and experiment 2 assessed diet utilization and fermentation in response to one of four thymol doses: 0, 120, 240, and 480 mg/kg intake. For experiment 1, thymol dose did not affect treatment or forage intake (p ≥ 0.17). For experiment 2, thymol did not linearly or quadratically affect (p ≥ 0.28) forage organic matter (OM) intake or OM digestibility. There were also no linear or quadratic effects (p ≥ 0.09) on ruminal ammonia-N, volatile fatty acids, or pH. These data indicate that thymol can be provided to beef cattle at up to 330 mg/kg intake and 480 mg/kg intake without negatively impacting acceptance and diet utilization, respectively. Full article

Beef production in intensive systems requires optimal nutrition to maximize growth and profitability. While triglycerides contain twice the energy per unit weight compared to polysaccharides, they are not nearly as commonly used as a supplemental source of energy compared to starch, largely in part due to their negative effects on rumen physiology when their inclusion levels are too high. To gain further insights into the response of rumen microbial communities to elevated dietary lipid levels, we took advantage of rumen samples collected as part of a previously published study that tested high inclusion (4% and 8%) of tallow or linseed oil in beef cattle as part of a 5 × 5 Latin square design, with corn used as a base dietary ingredient. Using a 16S rRNA gene-based profiling approach, two uncharacterized candidate rumen bacterial Operational Taxonomic Units (OTUs), referred to as Bt-995 and Bt-1367, were found to be in higher abundance in rumen samples collected from steers when they were fed diets with higher inclusion of linseed oil. Using a metagenomics approach to assemble contigs corresponding to genomic regions of these OTUs, various predicted metabolic functions were found to be shared. Consistent with the dietary treatments of the original animal study, functions associated with starch utilization and triglyceride metabolism were identified. Unexpectedly, however, contig sets from both OTUs also encoded genes predicted to be involved in vitamin B₁₂ biosynthesis, as well as ethanolamine utilization, a function that is dependent on vitamin B₁₂ as a co-factor. Together, these results indicate that vitamin B₁₂-related functions may provide an advantage to rumen bacteria under conditions of high dietary triglyceride inclusion. Full article

Understanding the genetic regulatory mechanisms of fat accumulation is crucial for improving beef quality. Hanwoo (Korean native cattle) is renowned for its high intramuscular fat (marbling), yet the genetic regulation of adipose gene expression remains insufficiently understood. In this study, we performed expression quantitative trait loci (eQTL) analysis using RNA-Seq data and genotype data from backfat tissue of 75 Hanwoo steers to identify regulatory variants associated with adipose deposition. A total of 25,042 significant cis-eQTL associations (FDR < 0.05) were identified, and 5362 unique top cis-eQTL pairs were retained after gene-wise filtering. Key cis-regulated genes included AGBL1, CACNG1, MYO18B, and DUSP29, which are involved in cytoskeletal organization, muscle development and calcium signaling. Three major cis-regulatory hotspots were located on BTA15 (BTA15:50354741) and BTA21 (BTA21:21526143, and BTA21:21541921). Permutation-based analysis (100,000 iterations) was conducted to control false positives, identifying 12 statistically significant trans-eQTL hotspots (FDR q < 0.05), of which SNP 6:60512276 and SNP 21:17035557 exhibited extensive trans-regulatory activity influencing 429 and 161 genes, respectively. In particular, SNP 21:17035557 acted as a shared cis- and trans-regulatory hub, indicating hierarchical control of adipose gene networks. Functional enrichment analyses revealed significant involvement of cytoskeleton- and calcium-dependent pathways, highlighting the interplay between structural remodeling and metabolic regulation in adipose tissue. These findings provide a comprehensive, system-level view of adipose gene regulation in Hanwoo cattle and highlight candidate molecular targets for genome-assisted and precision breeding. Moreover, this study offers quantitative genomic resources that can support the development of prediction models and decision-support systems for improving carcass traits in Hanwoo breeding programs. Full article

Warm-season grasses are the main source of feed in tropical and subtropical beef cattle production systems. The objective was to assess cattle preference among three warm-season grasses and explore its relationship with forage yield and plant structural traits. The three species were cultivated in 2 × 2 m plots using a completely randomized design. Cattle preference was evaluated in spring (December 2016 and 2017), summer (March 2017), and autumn (May 2017) using six Braford steers that grazed the plots for 4 h on two consecutive days. Pre-grazing forage yield, plant height, leaf-blade length, leaf-blade width, and the proportions of five leaf tissues at three leaf regions were measured at each date. Cattle preference was variable among the three species and evaluation dates. Paspalum atratum exhibited the highest pre-grazing forage yield, and constituted the tallest plants with the longest leaves during the summer. Urochloa brizantha showed the greatest proportion of vascular bundle sheath (17–30% at the midrib region, 25–31% at the interveinal region and 14–23% at the margin region) and P. atratum exhibited the greatest number of primary vascular bundle. Cattle preference was negatively correlated with the number of primary vascular bundle, pre-grazing forage yield, plant height and leaf-blade length. Full article

One hundred thirty-three high-risk crossbred beef steers and bulls (178.2 ± 20.9 kg) were used to evaluate dietary inclusion of a tannin (BXA) blend pellet during a 63 d receiving period and a 126 d grazing period compared with no dietary treatment (CON). Data were analyzed using SAS 9.4 with pen as the experimental unit. During receiving, no differences were noted on average daily gain (ADG) on a deads-out (p > 0.25) or deads-in (p > 0.75) basis. There were tendencies for increased DMI associated with BXA from D0–21, D23–42, and D0–42 (p < 0.13). During the grazing period, cattle fed BXA had greater ADG from D0–56, and D0–84 (p ≤ 0.05), and tended to have greater ADG from D0–28, D0–112, and D0–126 (p ≤ 0.09). Total period ADG (deads-out) did not differ between treatments (p = 0.18) nor on a deads-in basis (p = 0.20). No differences were noted in the percentage of animals treated for bovine respiratory disease (p = 0.19), death loss (p = 0.62), or percentage of animals removed as chronically morbid/dead (p = 0.90). Results indicate that BXA did not improve performance or health during the receiving period. However, this additive had positive effects during the grazing period. Full article

Deposition of intramuscular fat (IM), also known as marbling, is the deciding factor of beef quality grade in the U.S. Defining molecular mechanisms underlying the differential deposition of adipose tissue in distinct anatomical areas in beef cattle is key to the development of strategies for marbling enhancement while limiting the accumulation of excessive subcutaneous adipose tissue (SAT). The objective of this exploratory study was to define the IM and SAT transcriptional heterogeneity at the whole tissue and single-nuclei levels in beef steers. Longissimus dorsi muscle samples (9–11th rib) were collected from two finished beef steers at harvest to dissect matched IM and adjacent SAT (backfat). Total RNA from IM and SAT was isolated and sequenced in an Illumina NovaSeq 6000. Nuclei from the same samples were isolated by dounce homogenization, libraries generated with 10× Genomics, and sequenced in an Illumina NovaSeq 6000, followed by analysis via Cell Ranger pipeline and Seurat in RStudio (v4.3.2) By the expression of signature marker genes, single-nuclei RNA sequencing (snRNAseq) analysis identified mature adipocytes (AD; ADIPOQ, LEP), adipose stromal and progenitor cells (ASPC; PDGFRA), endothelial cells (EC; VWF, PECAM1), smooth muscle cells (SMC; NOTCH3, MYL9) and immune cells (IMC; CD163, MRC1). We detected six cell clusters in SAT and nine in IM. Across IM and SAT, AD was the most abundant cell type, followed by ASPC, SMC, and IMC. In SAT, AD made up 50% of the cellular population, followed by ASPC (31%), EC (14%), IMC (1%), and SMC (4%). In IM depot, AD made up 23% of the cellular population, followed by ASPC at 19% of the population, EC at 28%, IMC at 7% and SMC at 12%. The abundance of ASPC and AD was lower in IM vs. SAT, while IMC was increased, suggesting a potential involvement of immune cells on IM deposition. Accordingly, both bulk RNAseq and snRNAseq analyses identified activated pathways of inflammation and metabolic function in IM. These results demonstrate distinct transcriptional cellular heterogeneity between SAT and IM depots in beef steers, which may underly the mechanisms by which fat deposits in each depot. The identification of depot-specific cell populations in IM and SAT via snRNAseq analysis has the potential to reveal target genes for the modulation of fat deposition in beef cattle. Full article

Deposition of intramuscular adipose tissue (IMAT) is the primary determinant for beef quality grade in the U.S. Accumulation of subcutaneous (SCAT) and visceral (VIAT) adipose tissue precedes that of IMAT and often leads to excessive adiposity in beef cattle. Approaches to increase marbling while limiting subcutaneous and visceral adiposity are limited. Our objective is to define the depot-specific transcriptome profile and adipocyte function in IMAT, SCAT, and VIAT in beef steers. Transcriptomics revealed the upregulation of adipogenic and lipogenic genes in SCAT and VIAT vs. IMAT. Functional transcriptome analysis demonstrated the activation of pathways for lipid metabolic processes and biosynthesis in SCAT, accompanied by increased preadipocyte proliferation, adipocyte size, and insulin responses of SCAT in vitro. While IMAT had a greater abundance of preadipocytes, they proliferated at a lower rate and differentiated into adipocytes that were smaller and less responsive to insulin compared to SCAT. The upregulation of extracellular matrix genes in IMAT suggests that fat accumulation may be limited by the muscle microenvironment. The activation of inflammatory and immune response pathways, combined with a higher abundance of immune cells, highlighted VIAT as an immune-responsive depot. Our findings reveal transcriptional and cellular profiles underlying fat deposition in SCAT, VIAT, and IMAT in beef cattle. Full article

This study evaluates the effects of a proprietary tannin blend (BX), supplemented with or without sodium monensin (MON), on beef cattle performance, carcass traits, and health. Steers (n = 2986; initial shrunk body weight (SBW) 254 ± 9.2 kg) were allocated into 48 pens (61–62 steers/pen; 12 pens/treatment) fed for 230 d. Treatments included: (1) no feed additives (CTL); (2) BX (7.95 g/animal daily); (3) MON + Tylosin phosphate (TYL; 437.52 mg MON/animal daily + 80 mg TYL/animal daily); or (4) MON + BX (437.52 mg MON/animal daily + 7.95 g BX/animal daily). Data were analyzed in R 4.2.1 using a randomized block design with pen as the experimental unit. Dry matter intake was lower (p < 0.001) in MON + TYL and MON + BX than in CTL. Steers fed MON + BX had greater carcass-adjusted final SBW (p = 0.002), average daily gain (p = 0.002), fat thickness (p = 0.035), and marbling score (p = 0.046) than BX. Feed conversion improved in MON + TYL and MON + BX (p < 0.001). CLT and BX had higher (p < 0.001) liver abscess prevalence compared to MON + BX and MON + TYL. The addition of BX did not improve the parameters measured. Steers fed MON + BX showed reduced liver abscesses and similar feed efficiency compared to MON + TYL. Full article

Summer turnips (Brassica rapa L.) have become one of the main supplementary crops in ruminant livestock systems in southern Chile because of accelerated forage growth as well as greater forage yield and nutritive value in the dry season. This study investigated the effects of forage turnip supplementation on the physicochemical and sensory quality of beef from steers. Twenty-seven Holstein–Friesian steers were allocated to one of three dietary treatments: pasture plus concentrate (Control), 50% turnip with a basal diet of pasture hay and rolled corn (T50), and 70% turnip with the same basal diet (T70). Carcass yields and physicochemical and sensory beef attributes, including fatty acid composition of intramuscular fat (IMF) in lean tissue, were measured. Compared to the Control diet, finishing steers on 50% or 70% turnips increased meat redness (a* > 25.9 vs. 22.9 in Control), IMF (1.79% in T50 vs. 1.12% in Control), polyunsaturated fatty acids (PUFAs) (especially n-3), cholesterol, and specific minerals (sodium, manganese and iron); this resulted in a reduction in the subcutaneous fat thickness (0.29 cm in T50, 0.25 cm in T70 vs. 0.51 cm in Control) and shear force of cooked meat (p < 0.05). However, no differences were found between diets in beef juiciness, flavor, and tenderness assessed by trained panelists (p > 0.05). Increasing forage turnip inclusion to 70% resulted in similar beef quality to the 50% inclusion level. Foraged turnips present a promising strategy for producing high-quality beef during periods of limited pasture growth. Full article

The objective of this study to evaluate the effects of two levels of concentrate supplementation (1 g/kg or 2 g/kg of body weight, BW) on the intake, apparent digestibility and performance of Girolando steers on tropical pastures during the post-weaning phase in the dry to rainy season transition. We used 20 Girolando steers (half Holstein x half Zebu), with an average initial BW of 151.15 ± 50 kg and 12 months of age. The steers grazed on Urochloa brizantha cv. Marandu pasture. The animals were randomly assigned supplementation with 1 g/kg of BW (SC1) or supplementation with 2 g/kg of BW (SC2) of a concentrate supplement. The forage dry matter intake (%BW), neutral detergent fiber intake (NDF) and NDF digestibility were higher (p < 0.05) for steers supplemented with a level of 1 g/kg of BW. Supplement intake (kg/day), non-fibrous carbohydrate (NFC) intake and NFC digestibility were higher (p < 0.05) for steers consuming 2 g/kg BW of the concentrated supplement. The body weight at slaughter (297 kg) and average daily gain (0.57 kg/day) were not influenced by the level of supplementation. The use of 1 g/kg BW of a concentrated supplement is recommended for post-weaning steers on tropical pastures during the dry to rainy season transition. Full article

Global beef demand will rise by 40 million tons in 30 years, increasing methane (CH₄) emissions. Pigweed (Amaranthus spinosus), an invasive weed abundant in southeastern U.S. pastures, may mitigate CH₄. Yet, its potential as a feed additive remains unexplored. The aim of this study was to evaluate the influence of pigweed and its extracts on ruminal fermentation and CH₄ production. For Exp 1, ruminal fluid from three American Aberdeen steers was incubated with 0, 2.5%, 5%, or 10% of diet dry matter (DM) of roots, stems, leaves, seeds, or the whole pigweed plant (WHO). In Exp 2, extracts from the leaves and WHO were incubated under the same conditions. For the first experiment, 2.5% of the roots, 5% of the leaves, and 10% of the WHO decreased acetate and butyrate concentrations (p < 0.01). In contrast, the WHO, leaves, and seeds at 2.5% of DM increased propionate concentration (p = 0.05). Increasing levels of WHO, leaves, and seeds quadratically reduced CH₄ (p < 0.001). The addition of 2.5 and 5% of leaves and WHO reduced in vitro CH4 production per gr of organic matter fermented (p < 0.01). In Exp 2, based on their CH₄ mitigation, the leaves and WHO were extracted, and their phenol (3.2 and 1.1 mg/g of DM, respectively) and flavonoid (19.7 and 1.9 mg/g of DM, respectively) contents were determined. Extracts from WHO (2.5%) decreased acetate and CH₄ (p < 0.05), while 5% inclusion decreased gas production and increased ruminal pH (p < 0.03). Leaf extracts (2.5%) increased propionate and reduced acetate: propionate (p < 0.05). The leaves and WHO extracts did not affect IVOMD at either inclusion level (p > 0.4). Extracts at 5% from WHO were more effective than that from leaves in reducing CH₄ (27% vs. 4%). The evidence suggests that the inclusion of 2.5 to 5% of WHO extracts shifts ruminal fermentation towards propionate-producing impairing methanogenesis, representing a sustainable strategy to mitigate CH₄. This hypothesis must be further assessed under in vivo supplementation of the extracts to beef cattle. Full article

To safeguard an agricultural landscape with high biodiversity, livestock grazing on semi-natural pastures is crucial, and steers are well suited to such production systems. This study compared meat quality, including technological traits, sensory attributes, and fatty acid composition, of purebred dairy steers (D) and dairy × beef crossbreed steers (C), reared in two distinct production systems. Sixty-four steers (thirty-two per breed type) were included. Half were kept in a production system that had relatively high feed intensity (H), with one grazing summer on semi-natural pastures and slaughtered at 21 months of age. The other half were kept in a production system that had low feed intensity (L), with two grazing summers on semi-natural pastures and slaughtered at 28 months. Colour, water holding capacity, Warner–Bratzler shear force, sensory attributes, and fatty acid profiles were measured on the Musculus longissimus lumborum. Meat from L steers with two grazing seasons was darker (p = 0.003) and contained a higher proportion of unsaturated fatty acids (p = 0.006) than meat from more intensively reared H steers. Meat from C steers was perceived as having a coarser fibre structure (p = 0.022) with an acidic odour (p = 0.040) compared to D steers. Additionally, cooked meat from L steers was evaluated as having a pinker appearance by an analytical sensory panel (p = 0.008). In summary, breed type and production system had no major effect on technological and sensory attributes for forage and pasture-fed steers, but fatty acid composition was improved with more unsaturated lipids in meat from L steers. Full article

Genetic polymorphisms have a great impact on enhancing quantitative traits in cattle. In this study, Fatty acid synthase (FASN) g. 16024 (A>G), Stearoyl-CoA desaturase (SCD) g. 10329 (C>T), and pleomorphic adenoma gene (PLAG1) g. 25003338 (C>G) genotypic and allelic polymorphisms were evaluated, along with their associations with fatty acid composition, adipogenic gene expression, and carcass characteristics (carcass weight, yield grade, backfat thickness, and marbling score) in Hanwoo steers. A total of 128 Hanwoo steers were selected for this study and the Polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP) method was used to identify polymorphism of these genes. The AG genotype and G allele in FASN g. 16024 (A>G), CT genotype and T allele in SCD g. 10329 (C>T), and GG genotype and G allele in PLAG1 g. 25003338 (C>G) showed higher frequency and positively correlated with carcass traits, yield, and quality grades. Fatty acid composition results indicate that C18:3n-6, C20:1, and C20:2n-6 were significantly higher in the AA genotype of FASN gene, C14:1 and C18:3n-6 in the CC genotype, and C16:1 in the TT genotype of SCD gene. C12:0, C14:0, C16:1, C18:0, and C20:0 were higher in the CC genotype of PLAG1 gene. Furthermore, RT-qPCR analysis of adipogenesis-related genes (AMP-activated protein kinase-α (AMPKα), Carnitine palmitoyl transferase-1β (CPT1), G-coupled protein receptor-43 (GPR43), and SCD) across different SNP genotypes suggests a systemic interaction between genetic factors and adipogenesis in beef cattle. This study emphasizes the significance of FASN g. 16024 (A>G), SCD g. 10329 (C>T), and PLAG1 g. 25003338 (C>G) SNPs for genetic selection to enhance beef quality and elucidate lipid metabolic pathways in Hanwoo cattle. Full article