Browsing by Author "Van Emon, Megan L."

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Evaluation of sustained release mineral boluses as a long-term nutrient delivery method for beef cattle
(2021-09) Carlisle, Tanner J.; Wyffels, Samuel A.; Stafford, Steve D.; Taylor, Anna R.; Van Emon, Megan L.; DelCurto, Timothy
Two studies were conducted to evaluate the efficacy of sustained release mineral boluses as an alternative nutrient delivery method for beef cattle. For both studies 16 ruminally-cannulated cows were used in a completely randomized design. In study 1, we evaluated degradation rates of two bolus prototypes and cow age (2-yr-old versus 3-yr-old cows) over an 87-d study period. In study 2, we evaluated two bolus types (90-d degradation target versus 180-d degradation target), as well as two diet qualities contrasting a low-quality high-fiber forage (> 600 g/kg neutral detergent fiber and < 80 g/kg crude protein, dry matter basis) and high-quality low-fiber forage (< 500 g/kg neutral detergent fiber and> 150 g/kg crude protein, dry matter basis). For both Study 1 & 2, intake and digestion periods were conducted to evaluate cow age (study 1) or diet quality (study 2) effects on intake and rumen/reticulum function. In study 1, models containing an asymptotic effect of day and an interaction between day and bolus type were the best supported of the candidate models for bolus degradation rate. Cow age did not affect (P= 0.48) bolus degradation rates ( = -0.81 ± 1.13) and degradation rates were greater (P < 0.01) for bolus prototype B compared to bolus A ( prototype B = -20.39 ± 1.13; prototype A = -9.64 ± 0.81). Bolus degradation rate displayed an asymptotic relationship (P < 0.01) to bolus surface area for prototype A ( = 5.83 ± 0.57) and a linear relationship (P < 0.01) for prototype B ( = 0.001 ± 0.0001). In study 2, models containing a linear effect of day and an interaction between day and diet were the best supported of the candidate models for the degradation rate of the 90-d and 180-d prototype. In addition, both bolus protoypes displayed a diet quality × time interaction (P < 0.01) for bolus degradation rate. Cattle treated with the 90-d bolus and fed a high-quality diet had a greater (P < 0.01) degradation rate ( High-quality = -2.64 ± 0.08; Low-quality = -1.97 ± 0.10) than the cows that were fed a low-quality diet. In contrast, cattle treated with the 180-d bolus had an inverse effect (P < 0.01), with bolus degradation rates greater ( Low-quality = -0.09 ± 0.007; High-quality = -0.04 ± 0.005) with cows on the low-quality diet versus the high-quality diet. Across both studies, two of four bolus prototypes met target release rates at 90 days. However, bolus prototype degradation characteristics varied and were influenced by diet quality.
Influences of increasing levels of sulfate in drinking water on the intake and use of low-quality forages by beef cattle
(American Registry of Professional Animal Scientists, 2023-02) Wyffels, Samuel A.; Van Emon, Megan L.; Nack, Makae F.; Manoukian, Marley K.; Carlisle, Tanner J.; Davis, Noah G.; Kluth, Janessa A.; DelCurto-Wyffels, Hannah M.; DelCurto, Timothy
Objective. This study evaluated the effects of varying sulfate concentrations of water on forage and water intake, digestibility, digestive kinetics, and rumen fermentation characteristics of cattle consuming low-quality forages provided a protein supplement, with and without salt. Materials and Methods. Eight ruminally cannulated cows (2 yr of age) were used in 2 concurrent 4 × 4 Latin squares (4 cows per square) to test the effects of increasing water sulfate concentrations on forage and water intake, digestibility, digestive kinetics, and rumen fermentation characteristics of cattle consuming low-quality forages provided protein supplement with and without salt. Within each square, cows were randomly assigned to the following treatments: (1) control (<10 mg/L sulfate); (2) 473 mg/L; (3) 946 mg/L; and (4) 1,420 mg/L. All cattle were provided a crude protein supplement at 0.18% of BW daily (0800 h daily); however, protein supplement NaCl composition differed by square (no NaCl vs. addition of 25% NaCl). Each period consisted of a 14-d adaptation period, followed by a 7-d intake and digestion period with ruminal profiles conducted on d 22 and complete ruminal evacuations on d 23, 5 h after feeding. Results and Discussion. There were no observed effects of sulfate (SO4) levels on forage intake, water intake, ruminal DM and liquid fill, ruminal DM and NDF digestibility, ruminal liquid passage rate, ruminal liquid turnover, ruminal liquid flow rate, ruminal pH, ruminal ammonia, ruminal total VFA concentrations, ruminal individual VFA concentrations, or the ruminal acetate-to-propionate ratio (P ≥ 0.16). Furthermore, the addition of 25% salt to supplement had no effect on forage intake, ruminal DM and liquid fill, DM and NDF digestibility, liquid passage rate, liquid turnover, liquid flow rate, ruminal pH, or the acetate-to-propionate ratio (P ≥ 0.24). Conversely, water intake was greater for animals provided 25% salt in supplement compared with animals not provided salt (P = 0.05). Implications and Applications. Sulfate water concentrations as high as 1,420 mg/L had minimal effects on intake, digestibility, and rumen fermentation characteristics of cattle consuming low-quality forage-based diets when provided a protein supplement containing up to 25% salt.
Loci associated with conception rate in crossbred beef heifers
(2020-04) Oliver, K. F.; Geary, T. W.; Kiser, J. N.; Galliou, J. M.; Van Emon, Megan L.; Seabury, C. M.; Spencer, T. E.; Neibergs, H. L.
The inability of beef cattle to maintain full term pregnancies has become an economic concern for the beef industry. Herd management and nutritional improvements have alleviated environmental impacts on embryonic and fetal loss, yet additional gains can be made through genomic selection. The objectives of this study were to identify loci and gene-sets in crossbred beef heifers associated with the number of services required to become pregnant (TBRD) and heifer conception rate at first service (HCR1). Heifers (n = 709) from a commercial beef operation underwent one round of artificial insemination, before exposure to bulls for natural service for 50 days. Pregnancy and time of conception was determined by ultrasound 35 days after the breeding season. Heifers were genotyped using the GeneSeek (Lincoln, NE) Bovine GGP50K BeadChip prior to genome-wide association analyses (GWAA) conducted using an EIGENSTRAT-like model to identify loci associated (P < 1 × 10−5) with TBRD and HCR1. One locus was associated (P = 8.97 × 10−6) with TBRD on BTA19 and included the positional candidate gene ASIC2, which is differentially expressed in the endometrium of fertility classified heifers, and the positional candidate gene, SPACA3. Gene-set enrichment analyses using SNP (GSEA-SNP) data, was performed and identified one gene-set, oxidoreductase activity, acting on paired donors, with incorporation or reduction of molecular oxygen as enriched (NES = 3.15) with TBRD and contained nine leading edge genes that contributed to the enrichment of the gene set. The enriched gene-set is involved in catalyzing oxidation-reduction reactions, which have been associated with oxidative stressors impacting pregnancy success. No loci were associated nor gene-sets enriched with HCR1. Identification of loci, positional candidate genes, gene-sets and leading edge genes enriched for fertility facilitate genomic selection that allows producers to select for reproductively superior cattle, reduce costs associated with infertility, and increase percent calf crop.
Relationships among intramammary health, udder and teat characteristics, and productivity of extensively managed ewes
(Oxford University Press, 2021-02) Knuth, Ryan M.; Stewart, Whit C.; Taylor, Joshua B.; Bisha, Bledar; Yeoman, Carl J.; Van Emon, Megan L.; Murphy, Thomas W.
Mastitis is an economically important disease and its subclinical state is difficult to diagnose, which makes mitigation more challenging. The objectives of this study were to screen clinically healthy ewes in order to 1) identify cultivable microbial species in milk, 2) evaluate somatic cell count (SCC) thresholds associated with intramammary infection, and 3) estimate relationships between udder and teat morphometric traits, SCC, and ewe productivity. Milk was collected from two flocks in early (<5 d) and peak (30 to 45 d) lactation to quantify SCC (n = 530) and numerate cultivable microbial species by culture-based isolation followed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS; n = 243) identification. Within flock and lactation stage, 11% to 74% (mean = 36%) of samples were culture positive. More than 50 unique identifications were classified by MALDI-TOF MS analysis, and Bacillus licheniformis (18% to 27%), Micrococcus flavus (25%), Bacillus amyloliquefaciens (7% to 18%), and Staphylococcus epidermidis (26%) were among the most common within flock and across lactation stage. Optimum SCC thresholds to identify culture-positive samples ranged from 175 × 103 to 1,675 × 103 cells/mL. Ewe productivity was assessed as total 120-d adjusted litter weight (LW120) and analyzed within flock with breed, parity, year, and the linear covariate of log10 SCC (LSCC) at early or peak lactation. Although dependent on lactation stage and year, each 1-unit increase in LSCC (e.g., an increase in SCC from 100 × 103 to 1,000 × 103 cells/mL) was predicted to decrease LW120 between 9.5 and 16.1 kg when significant. Udder and teat traits included udder circumference, teat length, teat placement, and degree of separation of the udder halves. Correlations between traits were generally low to moderate within and across lactation stage and most were not consistently predictive of ewe LSCC. Overall, the frequencies of bacteria-positive milk samples indicated that subclinical mastitis (SCM) is common in these flocks and can impact ewe productivity. Therefore, future research is warranted to investigate pathways and timing of microbial invasion, genomic regions associated with susceptibility, and husbandry to mitigate the impact of SCM in extensively managed ewes.