Z. D. McFarlane

Serum metabolites associated with feed efficiency in black angus steers

IntroductionImproving feed utilization in cattle is required to reduce input costs, increase production, and ultimately improve sustainability of the beef cattle industry. Characterizing metabolic differences between efficient and non-efficient animals will allow stakeholders to identify more efficient cattle during backgrounding.ObjectivesThis study used an untargeted metabolomics approach to determine differences in serum metabolites between animals of low and high residual feed intake.MethodsResidual feed intake was determined for 50 purebred Angus steers and 29 steers were selected for the study steers based on low versus high feed efficiency. Blood samples were collected from steers and analyzed using untargeted metabolomics via mass spectrometry. Metabolite data was analyzed using Metaboanalyst, visualized using orthogonal partial least squares discriminant analysis, and p-values derived from permutation testing. Non-esterified fatty acids, urea nitrogen, and glucose were measured using commercially available calorimetric assay kits. Differences in metabolites measured were grouped by residual feed intake was measured using one-way analysis of variance in SAS 9.4.ResultsFour metabolites were found to be associated with differences in feed efficiency. No differences were found in other serum metabolites, including serum urea nitrogen, non-esterified fatty acids, and glucose.ConclusionsFour metabolites that differed between low and high residual feed intake have important functions related to nutrient utilization, among other functions, in cattle. This information will allow identification of more efficient steers during backgrounding.

110 Effect of forage species and supplement type on rumen kinetics and serum metabolites in developing beef heifers grazing winter forage

The objective of this study was to determine the effect of stockpiled forage type and protein supplementation on VFA production, serum metabolites, and BW in yearling beef heifers. Over 2 yr, spring-born, Angus crossbred yearling beef heifers ( = 42; 305 ± 2.9 kg initial BW) were randomly assigned to 1 of 3 forage pasture types: 1) endophyte-infected tall fescue [TF; (Schreb.) Dumort], 2) a big bluestem ( Vitman) and indiangrass ( L.) combination (BI), or 3) switchgrass (SG; L.). Each pasture was then randomly assigned to receive either 1 of 2 isonitrogenous CP treatments: 1) 0.68 kg·heifer·d of dried distillers grains with solubles (DDGS; 28% CP and 88% TDN) or 2) 0.22 kg·heifer·d of blood meal and fish meal (BF; 72.5% CP and 69.5% TDN), resulting in a 3 × 2 factorial arrangement of treatments. Treatments were initiated in January and terminated in April in both years of the study. Body weights and blood samples were collected approximately every 28 d from initiation of grazing until the end of the trial. Heifer BW change from January to February and overall BW change were greater ( < 0.01) for TF heifers. However, BW change from March to April was not different ( = 0.84) among forage types. Supplement type did not influence ( ≥ 0.13) BW or BW change from January to February and from January to April; however, heifers fed DDGS had greater ( = 0.03) BW gain from March to April. Heifer BW change from February to March exhibited ( < 0.05) a forage type × supplement interaction, with BF-fed heifers gaining more BW on BI pastures than DDGS-fed heifers. Serum glucose concentrations, ruminal acetate, and the acetate:propionate ratio were greater ( ≤ 0.04) for SG heifers. However, circulating serum NEFA and urea N (SUN) concentrations were not different ( ≥ 0.85) among forage types. Serum glucose and NEFA concentrations were not influenced ( ≥ 0.61) by supplement type. Circulating SUN concentrations were greater ( < 0.01) in BF-supplemented heifers. Ruminal acetate tended to be greater ( = 0.09) and butyrate concentrations were greater ( < 0.01) for BF-supplemented heifers. The acetate:propionate ratio was not influenced ( = 0.15) by supplement type. These results suggest that a compensatory gain period prior to breeding would be needed for these native warm-season species to be a viable opportunity for growing and developing replacement heifers in the southeastern United States.

Effects of endophyte infected tall fescue seed and red clover isoflavones on rumen microbial populations, fiber fermentation, and volatile fatty acids in vitro

Negative impacts of endophyte-infected Lolium arundinaceum (Darbyshire) (tall fescue) are responsible for over

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

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.

Winter grazing of stockpiled native forages during heifer development delays body weight gain without influencing final pregnancy rates1

Negative impacts of endophyte-infected Lolium arundinaceum (Darbyshire) (tall fescue) are responsible for over

Circulating beta-hydroxybutyrate concentration may be a predictive measurement for young cows that have a greater probability to conceive at a fixed-time artificial insemination

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.

Heifer development using stockpiled, dormant native forages and protein supplementation delays body weight gain without altering reproductive performance

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.