An autosomal recessive variant in PYGM causes myophosphorylase deficiency in Red Angus composite cattle.

BACKGROUND: Between 2020 and 2022, eight calves in a Nebraska herd (composite Simmental, Red Angus, Gelbvieh) displayed exercise intolerance during forced activity. In some cases, the calves collapsed and did not recover. Available sire pedigrees contained a paternal ancestor within 2-4 generations in all affected calves. Pedigrees of the calves' dams were unavailable, however, the cows were ranch-raised and retained from prior breeding seasons, where bulls used for breeding occasionally had a common ancestor. Therefore, it was hypothesized that a de novo autosomal recessive variant was causative of exercise intolerance in these calves. RESULTS: A genome-wide association analysis utilizing SNP data from 6 affected calves and 715 herd mates, followed by whole-genome sequencing of 2 affected calves led to the identification of a variant in the gene PYGM (BTA29:g.42989581G > A). The variant, confirmed to be present in the skeletal muscle transcriptome, was predicted to produce a premature stop codon (p.Arg650*). The protein product of PYGM, myophosphorylase, breaks down glycogen in skeletal muscle. Glycogen concentrations were fluorometrically assayed as glucose residues demonstrating significantly elevated glycogen concentrations in affected calves compared to cattle carrying the variant and to wild-type controls. The absence of the PYGM protein product in skeletal muscle was confirmed by immunohistochemistry and label-free quantitative proteomics analysis; muscle degeneration was confirmed in biopsy and necropsy samples. Elevated skeletal muscle glycogen persisted after harvest, resulting in a high pH and dark-cutting beef, which is negatively perceived by consumers and results in an economic loss to the industry. Carriers of the variant did not exhibit differences in meat quality or any measures of animal well-being. CONCLUSIONS: Myophosphorylase deficiency poses welfare concerns for affected animals and negatively impacts the final product. The association of the recessive genotype with dark-cutting beef further demonstrates the importance of genetics to not only animal health but to the quality of their product. Although cattle heterozygous for the variant may not immediately affect the beef industry, identifying carriers will enable selection and breeding strategies to prevent the production of affected calves.

Estimating body weight and body condition score of mature beef cows using depth images.

Obtaining accurate body weight (BW) is crucial for management decisions yet can be a challenge for cow-calf producers. Fast-evolving technologies such as depth sensing have been identified as low-cost sensors for agricultural applications but have not been widely validated for U.S. beef cattle. This study aimed to (1) estimate the body volume of mature beef cows from depth images, (2) quantify BW and metabolic weight (MBW) from image-projected body volume, and (3) classify body condition scores (BCS) from image-obtained measurements using a machine-learning-based approach. Fifty-eight crossbred cows with a mean BW of 410.0 ±â€…60.3 kg and were between 4 and 6 yr of age were used for data collection between May and December 2021. A low-cost, commercially available depth sensor was used to collect top-view depth images. Images were processed to obtain cattle biometric measurements, including MBW, body length, average height, maximum body width, dorsal area, and projected body volume. The dataset was partitioned into training and testing datasets using an 80%:20% ratio. Using the training dataset, linear regression models were developed between image-projected body volume and BW measurements. Results were used to test BW predictions for the testing dataset. A machine-learning-based multivariate analysis was performed with 29 algorithms from eight classifiers to classify BCS using multiple inputs conveniently obtained from the cows and the depth images. A feature selection algorithm was performed to rank the relevance of each input to the BCS. Results demonstrated a strong positive correlation between the image-projected cow body volume and the measured BW (r = 0.9166). The regression between the cow body volume and the measured BW had a co-efficient of determination (R2) of 0.83 and a 19.2 ±â€…13.50 kg mean absolute error (MAE) of prediction. When applying the regression to the testing dataset, an increase in the MAE of the predicted BW (22.7 ±â€…13.44 kg) but a slightly improved R2 (0.8661) was noted. Among all algorithms, the Bagged Tree model in the Ensemble class had the best performance and was used to classify BCS. Classification results demonstrate the model failed to predict any BCS lower than 4.5, while it accurately classified the BCS with a true prediction rate of 60%, 63.6%, and 50% for BCS between 4.75 and 5, 5.25 and 5.5, and 5.75 and 6, respectively. This study validated using depth imaging to accurately predict BW and classify BCS of U.S. beef cow herds.

Effect of protein and glucogenic precursor supplementation on forage digestibility, serum metabolites, energy utilization, and rumen parameters in sheep.

Supplementation of glucogenic precursors in roughage diets may increase production responses due to improved efficiencies of nutrient utilization. Therefore, the objective of this study was to determine the effect of source of supplemental glucogenic potential (GP) on forage digestibility, serum metabolites, energy utilization, and rumen parameters of growing wethers consuming a roughage diet (8.8% crude protein, 71.4% ash-free neutral detergent fiber). Crossbred wethers (49.1 ± 4.7 kg initial BW; n = 16) were utilized in a 4 × 4 replicated Latin Square design with four periods of 21 d. Supplements were designed to supplement increasing amount of GP: 1) no supplementation (CON; 0 g), 2) 40 g of calcium propionate (CAP; 30 g of GP), 3) 70 g of blood meal + 100 g of feather meal (BF; 40 g of GP), or 4) combination of CAP and BF (COMBO; 70 g of GP). Total fecal and urine collection was conducted from days 13-17 to calculate digestibility estimates and urinary losses. An acetate tolerance test was administered on day 17 to determine the effect of GP on acetate clearance. Blood samples were collected on day 19 and were analyzed for serum concentrations of glucose, urea N (SUN), non-esterified fatty acids, and amino acids. Rumen fluid was collected on day 21 to determine supplementation effects on ruminal volatile fatty acid (VFA) and ammonia concentrations. Wethers receiving BF and COMBO supplementation had greatest (P ≤ 0.01) DM and OM total tract digestibility. Supplementation did not affect (P ≥ 0.37) NDF digestibility or digestible energy. Urinary nitrogen excretion was greatest (P = 0.02) for BF and COMBO. Circulating serum essential amino acid concentration was increased (P < 0.01) in BF and COMBO compared to CAP and CON. In addition, BF and COMBO had increased (P < 0.01) SUN concentrations compared to CAP and CON. Acetate half-life was not affected (P = 0.39) by supplementation strategy. However, area under the curve (AUC) for acetate was decreased (P = 0.04) with supplementation of BF and COMBO compared to CON-fed wethers. Ruminal propionate concentration was increased (P ≤ 0.01) for wethers fed CAP and COMBO supplementation, which resulted in decreased (P ≤ 0.01) A:P ratio. Overall, these results indicate that the increased propionate supply by providing propionate salts did not result in a protein sparing impact or increased N retention.

The impact of cow size on cow-calf and postweaning progeny performance in the Nebraska Sandhills.

Optimizing beef production system efficiency requires an understanding of genetic potential suitable for a given production environment. Therefore, the objective of this retrospective analysis was to determine the influence of cow body weight (BW) adjusted to a common body condition score (BCS) of 5 at weaning-influenced cow-calf performance and postweaning steer and heifer progeny performance. Data were collected at the Gudmundsen Sandhills Laboratory, Whitman, NE, on crossbred, mature cows (n = 1,607) from 2005 to 2017. Cow BCS at calving, prebreeding, and weaning were positively associated (P < 0.01) with greater cow BW. Increasing cow BW was positively associated (P < 0.01) with the percentage of cows that conceived during a 45-d breeding season. For every additional 100-kg increase in cow BW, calf BW increased (P < 0.01) at birth by 2.70 kg and adjusted 205-d weaning BW by 14.76 kg. Calf preweaning average daily gain (ADG) increased (P < 0.01) 0.06 kg/d for every additional 100-kg increase in cow BW. Heifer progeny BW increased (P < 0.01) postweaning with every additional 100-kg increase in dam BW. Dam BW did not influence (P ≥ 0.11) heifer puberty status prior to breeding, overall pregnancy rates, or the percentage of heifers calving in the first 21 d of the calving season. Steer initial feedlot BW increased by 7.20 kg, reimplant BW increased by 10.47 kg, and final BW increased by 10.29 kg (P ≤ 0.01) for every additional 100-kg increase in dam BW. However, steer feedlot ADG was not influenced (P > 0.67) by dam BW. Hot carcass weights of steers were increased (P = 0.01) by 6.48 kg with every additional 100-kg increase in cow BW. In a hypothetical model using the regression coefficients from this study, regardless of pricing method, cow-calf producers maximize the highest amount of profit by selecting smaller cows. Overall, larger-sized cows within this herd and production system of the current study had increased reproductive performance and offspring BW; however, total production output and economic returns would be potentially greater when utilizing smaller-sized cows.

Developmental Programming in a Beef Production System.

Beef production is a complex system, in which cows are expected to perform in varied environmental conditions. In cattle, the most commonly reported developmental programming influence is nutrient restriction during the prenatal period due to climatic conditions affecting forage availability and quality. Recent research has demonstrated maternal or prepartum nutrition can affect more than just subsequent pregnancy rates. Studies in different species report how maternal nutrition influences progeny performance, health, and reproduction. Better understanding of developmental programming and nutritional management within different environments may advance cowherd efficiency.

The effect of cow udder score on cow/calf performance in the Nebraska Sandhills.

Poor udder and teat confirmation decreases profitability due to decreased calf weaning weight, increased incidence of mastitis and labor, and decreased cow lifetime productivity. Therefore, the objective of this retrospective study was to evaluate the effect of beef cow udder score on cow performance and pre- and postweaning progeny performance. In a 5-yr study, crossbred cows at the Gudmundsen Sandhills Laboratory, Whitman, NE, were assigned an udder score each year at calving, from 1 to 5, using an udder and teat combination score. Cows were grouped by udder scores and classified as either low udder score (LUS, udder score 1 or 2; n = 223) or high udder score (HUS, udder score 3 or 4; n = 1,742). The udder score combines udder conformation and a teat scoring system. Low udder scores consisted of pendulous udders and large teats, whereas HUS consisted of tight udders and small, symmetrical teats. Mixed models were used to evaluate udder score on cow performance and calf pre- and postweaning performance. Cow body weight (BW) at prebreeding and weaning was greater (P < 0.01) in LUS cows compared with HUS counterparts. Pregnancy rate was not different (P = 0.35) between udder classification groups. Calf BW at birth (P = 0.95), weaning (P = 0.40), and adjusted 205-d BW (P = 0.28) were not different between udder groups. Cow udder score did not influence feedlot entry (P = 0.41) and final BW (P = 0.30), dry matter intake (P = 0.53), average daily gain (P = 0.60), and gain:feed ratio (P = 0.85) of steer progeny. However, steers from HUS dams had greater hot carcass weight (HCW; P = 0.04) and backfat thickness (P = 0.02) compared with LUS counterparts. Results from this study suggest cows with less desirable udder structure may not have a negative impact on calf preweaning growth and performance; however, backfat thickness and HCW in the finishing phase were lower in steers from cows with a lower udder score.

Effects of endophyte-infected tall fescue seed and red clover isoflavones on rumen microbial populations and physiological parameters of beef cattle.

Lolium arundinaceum [(Darbyshire) tall fescue] toxicosis is responsible for substantial beef production losses in the United States, due to its negative effects on reproduction, growth, and feed efficiency. These effects are consequences of toxic alkaloids within tall fescue. Interseeding legumes, such as Trifolium pratense (red clover), into pastures has been shown to mitigate a portion of these effects. Clovers contain isoflavones, which may play a role in tall fescue toxicosis mitigation. The present study utilized 36 Angus steers to determine the effects of daily supplementation with a red clover-isolated isoflavone feed additive on physiological symptoms of tall fescue toxicosis and the rumen microbial environment over a 21-d period. Angus steers were initially stratified based upon their single nucleotide polymorphism genotype at the DRD2 receptor. Treatments were then randomly assigned in a 2 × 2 factorial arrangement within a completely randomized design, where treatment factors consisted of tall fescue seed type (endophyte-infected tall fescue seed vs. endophyte-free tall fescue seed) supplemented with and without the isoflavone additive. Steers that consumed endophyte-infected tall fescue seed had lower serum prolactin concentrations (P = 0.0007), average daily gain (ADG; P = 0.003), final body weight (BW; P = 0.004), and feed efficiency (P = 0.018) when compared with steers that consumed endophyte-free tall fescue seed. Serum insulin-like growth factor-1 (IGF-1) tended to be reduced with supplementation of isoflavones (P = 0.06) but was unaffected by seed type (P ≥ 0.10) and seed by treatment interaction (P ≥ 0.10). Isoflavones reduced serum glucose levels (P = 0.023), but neither seed type, isoflavones, or their interaction affected serum urea nitrogen (SUN), nonesterified fatty acids (NEFA), or insulin (P ≥ 0.10). Volatile fatty acid concentrations, dry matter intake (DMI), ruminal pH, and overall feeding behaviors were also unaffected by seed type or isoflavone treatments (P ≥ 0.10). Twenty-eight ruminal bacteria taxa shifted as a result of seed type or isoflavone treatment (P < 0.05). In this experiment, feeding isoflavones to Angus cattle did not completely mitigate all symptoms of fescue toxicosis. However, dose-response trials may aid future research to determine if dietary supplementation with isoflavones alleviates fescue toxicosis symptoms and promotes livestock growth and performance.

Eimeria gilruthi-associated abomasitis in a group of ewes.

Nine of 23 (39%) research ewes with severe diarrhea and weight loss had histologic lesions consistent with Eimeria gilruthi infection in their abomasa. Gross anatomic lesions included hundreds of opaque 1-mm nodules in abomasal mucosa that corresponded microscopically to 200-300 µm diameter organisms surrounded by areas of necrosis. Analysis of fecal samples from 4 ewes demonstrated oocysts from typical ovine Eimeria species, none of which were E. gilruthi. Two separate PCR reactions were performed on abomasal tissue from 4 sheep to amplify the 18S ribosomal DNA (rDNA) and internal transcribed spacer (ITS) region of the rDNA, respectively. The resultant 18S rDNA nucleotide sequences shared 99% homology with multiple Eimeria species in GenBank. The ITS region shared 77% homology with E. ellipsoidalis in GenBank. Further studies are needed to understand the life cycle and pathogenicity of E. gilruthi. Our results underscore the inclusion of E. gilruthi in the differential diagnosis of diarrhea and weight loss in sheep.

BEEF SPECIES-RUMINANT NUTRITION CACTUS BEEF SYMPOSIUM: Sustainable and economically viable management options for cow/calf production through enhanced beef cow metabolic efficiency1.

Beef cow herds are expected to be metabolically and reproductively efficient in varied and ever changing environmental conditions. Therefore, selection and management of grazing beef cows provides unique and diverse challenges in achieving optimal production efficiency for any environment. Beef cows face dynamic and highly variable nutritional environments that periodically are inadequate in meeting nutrient and energy requirements. Nutritional management during high metabolically stressed and key physiological states can lead to increased or decreased metabolic efficiency. Conversely, cow metabolic efficiency may be reduced in many production systems due to surplus nutritional inputs and reduced exposure to environmental stressors. Alternatively, metabolically potent supplementation strategies targeting enhanced energy metabolism and endocrine mechanisms would increase beef cow metabolic and economic efficiency. Metabolic efficient beef cows adapt to environmental changes by adjusting their metabolic energy utilization in order to match current environmental conditions and remain reproductively competent. This mechanism involves adaptive processes that drive adjustments in nutrient partitioning and energy utilization efficiency. However, the variation in metabolic and reproductive efficiency among beef cows within cow/calf production systems is substantial, suggesting a lack of complete integration of nutrition, genetics, and reproduction with environmental constraints and conditions. Better integration and understanding of the interactions may lead to advancements in metabolic efficiency of the cowherd. Metabolic flexibility is recognized as an important trait in dairy production but has received little attention thus far in beef cattle. Overall, management and supplementation strategies in cow/calf systems from a mechanistic, targeted nutritional approach during key physiological periods would hasten improvements in metabolic efficiency.

Effects of red clover isoflavones on tall fescue seed fermentation and microbial populations in vitro.

Negative impacts of endophyte-infected Lolium arundinaceum (Darbyshire) (tall fescue) are responsible for over $2 billion in losses to livestock producers annually. While the influence of endophyte-infected tall fescue has been studied for decades, mitigation methods have not been clearly elucidated. Isoflavones found in Trifolium pratense (red clover) have been the subject of recent research regarding tall fescue toxicosis mitigation. Therefore, the aim of this study was to determine the effect of ergovaline and red clover isoflavones on rumen microbial populations, fiber degradation, and volatile fatty acids (VFA) in an in vitro system. Using a dose of 1.10 mg × L-1, endophyte-infected or endophyte-free tall fescue seed was added to ANKOM fiber bags with or without 2.19 mg of isoflavones in the form of a control, powder, or pulverized tablet, resulting in a 2 × 3 factorial arrangements of treatments. Measurements of pH, VFA, bacterial taxa, as well as the disappearance of neutral detergent fiber (aNDF), acid detergent fiber (ADF), and crude protein (CP) were taken after 48 h of incubation. aNDF disappearance values were significantly altered by seed type (P = 0.003) and isoflavone treatment (P = 0.005), and ADF disappearance values were significantly different in a seed × isoflavone treatment interaction (P ≤ 0.05). A seed × isoflavone treatment interaction was also observed with respect to CP disappearance (P ≤ 0.05). Eighteen bacterial taxa were significantly altered by seed × isoflavone treatment interaction groups (P ≤ 0.05), eight bacterial taxa were increased by isoflavones (P ≤ 0.05), and ten bacterial taxa were altered by seed type (P ≤ 0.05). Due to the beneficial effect of isoflavones on tall fescue seed fiber degradation, these compounds may be viable options for mitigating fescue toxicosis. Further research should be conducted to determine physiological implications as well as microbiological changes in vivo.

Winter grazing of stockpiled native forages during heifer development delays body weight gain without influencing final pregnancy rates.

The objective of this study was to test the effects of protein supplementation strategy and different stockpiled forage species on growth, nutritional status, and reproductive performance of yearling beef heifers. In a 5-yr study, yearling beef heifers (n = 266) were stratified by body weight (BW) at weaning to 1 of 3 stockpiled forages: 1) endophyte-infected tall fescue (TF, Schedonorus arundinaceus (Schreb.) Dumort; 7.21% crude protein [CP] and 67.13% neutral detergent fiber [NDF], dry matter [DM] basis), 2) big bluestem (Andropogon gerardi Vitman) and indiangrass (Sorghastrum nutans L.) combination (BI; 4.32% CP and 71.06% NDF, DM basis), or 3) switchgrass (SG,Panicum virgatum L.; 3.87% CP and 76.79% NDF, DM basis). Forage treatments were then randomly assigned to receive 1 of 2 supplement types: 1) 0.68 kg heifer-1 d-1 of dried distillers grains with solubles (DDGS: 28% CP and 108% total digestible nutrients [TDN]) or 2) 0.22 kg heifer-1 d-1 of blood meal and fish meal (BF: 72.5% CP and 77.5% TDN), resulting in a 3 × 2 factorial arrangement of treatments. Each year, twenty-one 1.2-ha pastures (7 pastures per forage type) were utilized with 2 to 3 heifers per pastures. Treatments were initiated in January and terminated in April at the initiation of breeding. Initial BW was not different (P ≥ 0.22) by forage or supplement type. During the rest of the grazing period, BW was greater (P < 0.01) for TF heifers. However, average daily gain (ADG) was greater (P < 0.01) for BI and SG heifers from breeding to final pregnancy diagnosis. Heifers grazing TF pastures had greater (P < 0.01) overall ADG than their counterparts. The percentage of mature BW (MBW) at breeding was greater (P < 0.01) for TF heifers. Heifer BW and ADG was not influenced (P ≥ 0.06) by supplementation strategy. Serum glucose concentrations were not different (P ≥ 0.44) among forage type or supplement strategy. Pregnancy rates at fixed timed-artificial insemination and overall pregnancy rates did not differ (P ≥ 0.38) by forage or supplement treatment. Owing to forage nutritive value differences, heifers grazing low-quality, warm season grasses lost BW prior to the initiation of the breeding season. However, a negative BW gain prior to breeding did not negatively impact overall pregnancy rates.

Beta-hydroxybutyrate infusion identifies acutely differentially expressed genes related to metabolism and reproduction in the hypothalamus and pituitary of castrated male sheep.

To identify molecular pathways that couple metabolic imbalances and reproduction, we randomly assigned 10 castrated male sheep to be centrally injected into the lateral ventricle through intracerebroventricular cannulas with 1 ml of ß-hydroxybutyric acid sodium salt solution (BHB; 12,800 µmol/l) or saline solution (CON; 0.9% NaCl). Approximately 2 h postinjection, sheep were humanely euthanized, and hypothalamus and pituitary tissues were harvested for transcriptome characterization by RNA sequencing. RNA was extracted from the hypothalamus and pituitary and sequenced at a high depth (hypothalamus: 468,912,732 reads; pituitary: 515,106,092 reads) with the Illumina Hi-Seq 2500 platform and aligned to Bos taurus and Ovis aries genomes. Of the total raw reads, 87% (hypothalamus) and 90.5% (pituitary) mapped to the reference O. aries genome. Within these read sets, ~56% in hypothalamus and 69% in pituitary mapped to either known or putative protein coding genes. Fragments per kilobase of transcripts per million normalized counts were averaged and ranked to identify the transcript expression level. Gene Ontology analysis (DAVID Bioinformatics Resources) was utilized to identify biological process functions related to genes shared between tissues, as well as functional categories with tissue-specific enrichment. Between CON- and BHB-treated sheep, 11 and 44 genes were differentially expressed (adj. P < 0.05) within the pituitary and hypothalamus, respectively. Functional enrichment analyses revealed BHB altered expression of genes in pathways related to stimulus perception, inflammation, and cell cycle control. The set of genes altered by BHB creates a foundation from which to identify the signaling pathways that impact reproduction during metabolic imbalances.