Zachary D. McFarlane

The metabolic impact of the breeding season on beef bulls has not been extensively studied. The change in plane of nutrition and intensive activity demands induce body weight loss and metabolic changes that may influence fertility and long-term management. The use of metabolomics to characterize the metabolic changes or adaptations during the breeding season will aid in developing hypotheses for future research in beef bulls. The objective of this study was to identify metabolites in both serum and seminal fluid (circulating vs. excretory) that were affected temporally throughout a 65-d breeding season and by bull workload (bull: cow). Over a two-year period, purebred Angus bulls (year 1: n = 8, year 2: n = 9) owned and housed by the Cal Poly beef unit were surveyed using serum (collected via the coccygeal vein) and seminal fluid (collected via electroejaculation) at the beginning (d0), middle (d30), and end (d65) of a 65-day, post-AI breeding season. Bulls were subjected to one of three workload groups: high (HIGH), moderate (MOD), or low (LOW). Samples underwent HPLC-MS to identify metabolites within the fluids. Data were stratified for sample day and workload and compared using ANOVA for sample day and workload in a 3 × 2 factorial design. Within seminal fluid and blood serum, purine and pyrimidine metabolism pathways were the most affected (P ≤0.02). Three purine metabolism metabolites showed significant (P ≤0.03) workload × sample day interactions within seminal fluid. Xanthine, hypoxanthine, and inosine showed an increase (P ≤0.03) in abundance in moderate workload bulls throughout the 65-d breeding season and a decrease in abundance in high workload bulls. However, we speculate that a higher workload, likely with more total ejaculates and higher sperm cell turnover, may lead to an increased purine concentration for DNA synthesis. These foundational metabolomic data indicated that an important supplementation strategy to consider may be folate because of the relationship with purine metabolism. Overall, bull workload, particularly a high workload inducing catabolism, may provide a benefit for metabolic health and reproductive performance during the breeding season. This study aimed to identify metabolites present in the blood serum and seminal fluid of actively breeding Angus beef bulls. Metabolites may serve as biological markers of physiological processes occurring at the time of collection. Samples were obtained throughout a 65-d breeding season and assessed for metabolite relative abundance using mass spectrometry. Metabolites found in clear abundances were analyzed for significant fluctuations throughout the breeding season based on the expected “workload” of those bulls. Ideally, these findings will serve as foundational data for future metabolomic studies concerning beef bull reproductive physiology. In this dataset, the most conclusive metabolites for further exploration were related to purine metabolism.

The egg industry continues to search for alternative feed ingredients that support production efficiency, enhance egg quality, and add nutritional value. Microalgae are rich in protein, pigments, and long-chain polyunsaturated fatty acids, making them promising candidates for poultry diets. This study evaluated the effects of dietary inclusion (1 and 2%) of four microalgae species, Arthrospira platensis (Spirulina), Hydrodictyon sp., Uronema sp., and Vaucheria sp., on laying hen performance, egg quality, yolk fatty acid composition, and bone strength. Seventy-six Lohmann LSL-Lite hens (92 weeks of age) were randomly assigned to nine treatments (control diet or one of eight microalgae diets). Feed intake, egg production, egg mass, feed conversion ratio, eggshell traits, yolk color, yolk fatty acids, and tibial breaking strength were measured. Inclusion of microalgae did not negatively affect hen performance, egg quality, nor bone strength. Spirulina significantly improved egg production and egg mass (p < 0.05). Increasing levels of Spirulina, Hydrodictyon sp., and Uronema sp. enhanced yolk color (all p < 0.05), while Vaucheria sp. showed no effect (p > 0.05). Yolk fatty acid profiles were only modestly altered, with increased docosahexaenoic acid observed in hens fed Hydrodictyon and Uronema (p < 0.05). In conclusion, low-level dietary inclusion of these microalgae species appears safe for laying hens and may provide added value through improved yolk pigmentation and modest omega-3 enrichment.

Our study objective was to determine the apparent metabolizable energy (AME) and apparent ileal amino acid digestibility (AIAAD) of spirulina fed to broiler chickens and laying hens using the difference method. In both experiments, birds were either fed corn-soybean meal basal diets, containing no spirulina and formulated to provide the nutrient requirements of either broilers or layers, or fed test diets consisting of 25% spirulina and 75% of the appropriate basal diet. Titanium dioxide was added to all diets as an indigestible marker. The diets were fed to 10 replicate cages/treatment of broilers and 15 replicate cages/treatment of laying hens. The AME of spirulina for broilers was significantly lower (p < 0.05) (2368 ± 104 kcal/kg, as fed) than for laying hens (3144 ± 173 kcal/kg, as fed), suggesting bird type and age may influence energy utilization. The AIAAD of spirulina fed to broiler chickens did not differ from that of laying hens (p > 0.05), except for valine, alanine, and glycine, which were all significantly higher in laying hens (p < 0.05). Overall, the AIAAD for nonessential amino acids averaged 81.1%, with no significant difference between essential and nonessential amino acids. Differences in spirulina nutrient content cited in the literature support further research to determine the optimal inclusion of this alternative ingredient in broiler and layer diets.

California’s approximately 660,000 head of beef cattle are highly dependent on range bulls used to produce offspring that can perform across the state’s diverse ecological regions. Bulls need to be functional on rugged coastal landscapes, rolling foothills, deserts, and in high-elevation terrain. Few data exist that indicate factors related to selection, maintenance, and longevity of bulls used in rangeland landscapes. Objectives herein, were to assess factors influencing bull purchasing, management, and culling decisions of California beef producers. Surveys were mailed to the California Cattlemen’s Association membership (N = 1,410) with ~ 16% response rate (N = 227). Mean age and years of bull selection experience of respondents was 61 ± 1 yr and 27 ± 1 yr, respectively. Respondents managed cattle on a total of 694,949 hectare of owned, private leased, and leased public rangelands in California and surrounding states. Cow–calf herd size was 333 ± 92 head and bull battery averaged 18 ± 2 head with average bull longevity of 5 ± 1.3 yr. The average price paid for bulls in the last 2 yr was $5007 ± 163.33, while the highest price paid in the last 5 yr was $7291 ± 335.40. Survey responses were used to define current factors driving management after purchase and for subsequent breeding seasons. After bull purchase, 48% of producers turned bulls out directly with females, while 52% held bulls until the following breeding season. Additionally, most producers (70%) did not manage bulls to reduce condition after purchase. Semen quality analysis, a major component of a breeding soundness exam, was evaluated annually by 45% of respondents, while 20% of respondents never evaluated semen quality. Respondents indicated bull age (35%) and structural soundness (29%) as the most common factors for culling bulls. This research shows that despite the variability in operation demographics, there were similarities in beef bull selection and management across the state. Additionally, these data suggest the need for additional research focused on bull selection and management to maximize producer investment in reproduction.

In the United States, rangelands account for roughly 161 million hectares out of the 336 million hectares that comprise of grazing land ( Schuman et al., 2002). In California, 23 million hectares of rangelands ( Schuman et al., 2002; CAL Fire, 2010) contain annual grasses that provide forage for 67% of livestock ( The Changing California Forest and Range 2003 Assessment, 2003). Beef producers must utilize bull selection and breeding genetics to meet California’s diverse terrain and unique Mediterranean climate. The California Cattlemen’s Association (CCA) membership was previously surveyed in 2011, which indicated that flexibility in management from producers, government agencies, and industry partners must occur to meet production goals, particularly sustainability goals ( Roche et al., 2015). Matching genetics and management to the environment, livestock water development, cross fencing, and supplemental feeding were some of the key management practices that respondents indicated as priorities ( Roche et al., 2015). Previous research evaluated factors that affected bull prices through an economic analysis of marketing factors such as performance records, ultrasound measurements, and phenotypic characteristics ( Atkinson et al., 2010; Bacon et al., 2017); however, these studies were conducted in the Midwest and did not evaluate bull management post-purchase. Therefore, the objective of this survey was to evaluate the factors that influence bull management and culling decisions of beef producers utilizing Californian rangelands.

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 pretense (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 x isoflavone treatment interaction ( P ≤ 0.05). A seed x isoflavone treatment interaction was also observed with respect to CP disappearance ( P ≤ 0.05). Seventeen bacterial taxa were significantly altered by seed x isoflavone treatment interaction groups ( P ≤ 0.05), six bacterial taxa were increased by isoflavones ( P ≤ 0.05), and eleven 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.