Publications by authors named "Megan L Van Emon"

13 Publications

  • Page 1 of 1

Effects of maternal nutrition and rumen-protected arginine supplementation on maternal carotid artery hemodynamics and circulating amino acids of ewes and offspring.

J Anim Sci 2021 Nov;99(11)

Department of Animal Sciences and Center for Nutrition and Pregnancy, North Dakota State University, Fargo, ND 58108,USA.

Multiparous Rambouillet ewes (n = 32) were allocated in a completely randomized design to determine if rumen-protected L-arginine (RP-Arg) supplementation during mid- and late gestation would 1) alter maternal carotid artery hemodynamics and 2) affect circulating amino acids associated with arginine metabolism in dams from day 54 of gestation to parturition and in their offspring from birth to 54 d of age. Ewes were assigned to one of three treatments from day 54 ± 3.9 to parturition: control (CON; 100% nutrient requirements), restricted (RES; 60% of CON), and RES plus 180 mg RP-Arg•kg BW-1•d1 (RES-ARG). Ewes were penned individually in a temperature-controlled facility. Carotid artery hemodynamics was measured via Doppler ultrasound at day 50 and 130 of gestation. Maternal serum was collected at day 54 and 138 of gestation and at parturition. At parturition, lambs were immediately removed from their dams and reared independently. Lamb serum samples were collected at birth and 1, 3, 7, 33, and 54 d of age. Pulsatility index was the only hemodynamic measurement altered by dietary treatment, where day 130 measurements were greater (P ≤ 0.04) for RES and RES-ARG compared with CON. The change in pulsatility index was greater (P < 0.01) for RES compared with CON but tended to be intermediate (P ≥ 0.12) for RES-ARG. Maternal serum Arg, Cit, and Asp at day 138 were greater (P < 0.01) for CON compared with RES and RES-ARG; serum Orn at day 138 was greater (P = 0.04) for CON compared with RES. Maternal serum Cit at parturition was greater (P ≤ 0.03) for CON and RES-ARG compared with RES. Offspring serum Arg was affected by a maternal treatment by day of age interaction (P = 0.03), where at day 3, CON and RES-ARG had greater (P ≤ 0.03) serum Arg concentrations than RES, and at day 54, RES-ARG was greater than (P = 0.002) CON and RES was intermediate and did not differ from (P ≥ 0.09) CON and RES-ARG. Offspring serum Orn and Cit were less (P ≤ 0.03) for RES and RES-ARG compared with CON. Results indicate that distal tissue blood perfusion decreased due to maternal RES, and RES-ARG was able to improve perfusion but not to the level of CON ewes. Further, maternal RP-Arg altered offspring Arg and related amino acid concentrations during the postnatal period.
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http://dx.doi.org/10.1093/jas/skab201DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8559166PMC
November 2021

Diurnal Ruminal pH and Temperature Patterns of Steers Fed Corn or Barley-Based Finishing Diets.

Animals (Basel) 2021 Sep 27;11(10). Epub 2021 Sep 27.

Department of Animal and Range Sciences, Montana State University, Bozeman, MT 59717, USA.

This study evaluated the effects of corn or barley finishing diets on ruminal pH and temperature and their relationship to feed intake events using continuous reticulorumen monitoring of feedlot steers. Average daily ruminal pH and temperature were not impacted ( ≥ 0.17) by diet. However, diet did affect daily variation of ruminal pH and temperature ( < 0.01). Average hourly ruminal pH displayed a diet by hour post-feeding interaction ( < 0.01), where barley-fed steers had greater ( < 0.01) ruminal pH than corn-fed steers at 0, 1, 18, 19, 20, 21, 22 and 23 h post feeding, but had lower ( ≤ 0.05) ruminal pH than corn-fed steers at 6, 7, and 8 h post-feeding. Variation in ruminal pH hour post-feeding also displayed a diet by hour post-feeding interaction ( < 0.01), where barley-fed steers had greater ( ≤ 0.03) variation in ruminal pH at hours 1-17 post-feeding but did not differ ( ≥ 0.16) at 0, 18, 19, 20, 21, 22 and 23 h post-feeding. Additionally, average hourly ruminal temperature exhibited a diet by hour post-feeding interaction ( < 0.01). In summary, basal grain interacted with time post-feeding influencing ruminal pH and temperature in feedlot steers.
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http://dx.doi.org/10.3390/ani11102809DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8532594PMC
September 2021

The Influence of Environmental Conditions on Intake Behavior and Activity by Feedlot Steers Fed Corn or Barley-Based Diets.

Animals (Basel) 2021 Apr 27;11(5). Epub 2021 Apr 27.

Department of Animal and Range Sciences, Montana State University, Bozeman, MT 59717, USA.

This study evaluated the influence of diet and environmental conditions on intake behavior and activity of feedlot steers. Feedlot rations used were comprised of a main concentrate: (1) corn or (2) barley. A GrowSafe system measured individual animal intake and behavior and HOBO accelerometers measured steer standing time. An Onset weather station collected on site weather data. Steer daily intake displayed a diet by temperature class interaction ( ≤ 0.05). Relative temperature change had no effect on variation in intake ( = 0.60); however, diet influenced variation of intake ( < 0.01), where corn-fed steers had a greater coefficient of variation (CV) than barley-fed steers (21.89 ± 1.46 vs. 18.72 ± 1.46%). Time spent eating (min d) and eating rate (g min) both displayed a diet by temperature class interaction ( ≤ 0.05). Diet did not affect steer lying activity ( ≥ 0.12), however, time spent lying (min d) and frequency of lying bouts (bouts d) increased on relatively cold days while the duration of lying bouts (min bout; < 0.01) decreased. Short-term environmental temperature changes interacted with diet influencing feedlot beef cattle intake behavior; however, they did not interact with basal diet in respect to steer activity.
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http://dx.doi.org/10.3390/ani11051261DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8145294PMC
April 2021

Influence of amount and frequency of protein supplementation to ruminants consuming low-quality cool-season forages: efficiency of nitrogen utilization in lambs and performance of gestating beef cows.

J Anim Sci 2021 Jun;99(6)

Department of Animal Science, Texas A&M University, College Station, TX 77845, USA.

We evaluated the influence of amount and crude protein (CP) supplementation frequency (SF) on nitrogen (N) use by wethers and the performance of late-gestation beef cows. In exp. 1, seven Western whiteface wethers (31.8 ± 1.4 kg) were used in an incomplete 7 × 4 Latin square to evaluate intake and N use. Wethers received one of the seven treatments in a 2 × 3 factorial design containing two levels of supplemental soybean meal offered at a rate of 100% (F) or 50% (H; 50% of F) of the estimated CP requirement daily, once every 5, or once every 10 d, plus a non-supplemented control (CON). Low-quality cool-season forage (4.9 % CP; dry matter [DM] basis) was provided daily for ad libitum intake. Experimental periods lasted 30 d. In exp. 2, 84 Angus × Hereford cows (560 ± 35 kg) were stratified by age, body condition score (BCS), and expected calving date and allocated to 1 of the 21 feedlot pens (three pens per treatment). Pens were randomly assigned to receive the same treatments as in exp. 1 and cows had free access to low-quality cool-season forage (2.9% CP; DM basis). Cow body weight (BW) and BCS were measured every 14 d until calving and within 24 h after calving. In exp. 1, supplementation did not alter total DM and organic matter (OM) intake (P ≥ 0.26), but both parameters linearly decreased as SF decreased (P = 0.02). Supplementation increased DM, OM, and neutral detergent fiber (NDF) digestibility (P ≤ 0.02). Additionally, F feeding linearly increased DM, OM, and NDF digestibility as SF decreased (P ≤ 0.04). Digestibility of N, N balance, and digested N retained were greater with supplementation (P < 0.01), and N digestibility linearly increased as SF decreased (P = 0.01). Mean plasma urea-N concentration was not only greater (P < 0.01) for supplemented vs. CON wethers but also greater (P = 0.03) for F vs. H. In exp. 2, pre-calving BCS change was greater (P = 0.03) for supplemented cows. A linear effect of SF × supplementation rate for pre-calving BCS change was noted (P = 0.05), as F-supplemented cows lost more BCS compared with H as SF decreased. When considering supplementation intervals greater than 5 d, reducing the quantity of supplement provided, compared with daily supplementation, may be a feasible management strategy to maintain acceptable nutrient use and animal performance while reducing supplement and labor costs.
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http://dx.doi.org/10.1093/jas/skab122DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8221049PMC
June 2021

Corn versus Barley in Finishing Diets: Effect on Steer Performance and Feeding Behavior.

Animals (Basel) 2021 Mar 25;11(4). Epub 2021 Mar 25.

Department of Animal and Range Sciences, Montana State University, Bozeman, MT 59717, USA.

This study evaluated the effects of barley and corn finishing rations on feedlot performance and behavior of steers. Feedlot rations in this study were comprised of a main concentrate of either corn or barley. Steers were fed in a GrowSafe system to measure individual animal intake and behavior. Weight gain, average daily gain (ADG), and gain:feed were measured for each steer. Feeding behavior including time spent eating (min/day), visits per day, time per visit (min), eating rate (g/min), intake (kg/day), and intake per visit (g) were measured for each individual. Corn-fed steers had greater ADG ( < 0.01) and heavier hot carcass weights (HCW; < 0.01). In addition, corn fed steers had a higher yield grade than barley fed steers ( < 0.01). No treatment effects ( ≥ 0.11) were observed for time spent eating, visits per day, time per visit, eating rate, intake g/kg body weight, or intake per visit. Although corn-fed steers had a greater ADG and HCW than barley-fed steers, they tended to consume more feed ( = 0.06). Depending on the difference of costs associated with feeding corn or barley, barley could be a potential high-quality feed source in beef cattle finishing rations.
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http://dx.doi.org/10.3390/ani11040935DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8064474PMC
March 2021

Relationships among intramammary health, udder and teat characteristics, and productivity of extensively managed ewes.

J Anim Sci 2021 Apr;99(4)

USDA, ARS, Livestock Bio-systems Research Unit, Roman. L. Hruska U.S. Meat Animal Research Center, Clay Center, NE 68933, USA.

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.
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http://dx.doi.org/10.1093/jas/skab059DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8051848PMC
April 2021

Impacts of increasing levels of salt on intake, digestion, and rumen fermentation with beef cattle consuming low-quality forages.

Transl Anim Sci 2019 Dec 16;3(Suppl 1):1818-1821. Epub 2019 Dec 16.

Department of Animal and Range Sciences, Montana State University, Bozeman, MT.

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http://dx.doi.org/10.1093/tas/txz111DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6999140PMC
December 2019

Zinc AA supplementation alters yearling ram rumen bacterial communities but zinc sulfate supplementation does not.

J Anim Sci 2019 Feb;97(2):687-697

Montana State University, Department of Animal and Range Sciences, Bozeman.

 Despite the body of research into Zn for human and animal health and productivity, very little work has been done to discern whether this benefit is exerted solely on the host organism, or whether there is some effect of dietary Zn upon the gastrointestinal microbiota, particularly in ruminants. We hypothesized that (i) supplementation with Zn would alter the rumen bacterial community in yearling rams, but that (ii) supplementation with either inorganically sourced ZnSO4, or a chelated Zn AA complex, which was more bioavailable, would affect the rumen bacterial community differently. Sixteen purebred Targhee yearling rams were utilized in an 84-d completely randomized design, and allocated to one of three pelleted dietary treatments: control diet without fortified Zn (~1 × NRC), a diet fortified with a Zn AA complex (~2 × NRC), and a diet fortified with ZnSO4 (~2 × NRC). Rumen bacterial community was assessed using Illumina MiSeq of the V4 to V6 region of the 16S rRNA gene. One hundred and eleven OTUs were found with > 1% abundance across all samples. The genera Prevotella, Solobacterium, Ruminococcus, Butyrivibrio, Olsenella, Atopobium, and the candidate genus Saccharimonas were abundant in all samples. Total rumen bacterial evenness and diversity in rams were reduced by supplementation with a Zn AA complex, but not in rams supplemented with an equal concentration of ZnSO4, likely due to differences in bioavailability between organic and inorganically sourced supplement formulations. A number of bacterial genera were altered by Zn supplementation, but only the phylum Tenericutes was significantly reduced by ZnSO4 supplementation, suggesting that either Zn supplementation formulation could be utilized without causing a high-level shift in the rumen bacterial community which could have negative consequences for digestion and animal health.
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http://dx.doi.org/10.1093/jas/sky456DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6358250PMC
February 2019

Effects of maternal nutrition and rumen-protected arginine supplementation on ewe performance and postnatal lamb growth and internal organ mass.

J Anim Sci 2018 Jul;96(8):3471-3481

Departments of Animal Sciences, North Dakota State University, Fargo, ND.

The hypothesis of this study was that arginine supplementation would overcome negative effects of restricted maternal feed intake during the last two-thirds of gestation on ewe performance and positively affect postnatal lamb growth and development. Multiparous, Rambouillet ewes (n = 32) were allocated to 3 treatments in a completely random design at 54 ± 3.9 d of gestation. Dietary treatments were 100% of nutrient requirements (control, CON), 60% of control (restricted, RES), or RES plus a rumen-protected arginine supplement dosed at 180 mg/kg BW once daily (RES-ARG). Ewes were penned individually in a temperature-controlled facility. At parturition, lambs were immediately removed from dams and reared independently. At day 54 ± 3 of age, lambs were stunned using captive bolt, exsanguinated, and organs were collected and weighed. Ewe BW from day 68 of gestation through parturition was greater (P ≤ 0.03) in CON compared with RES or RES-ARG. Similarly, ewe BCS from day 68 of gestation through parturition was greater (P ≤ 0.03) in CON than either RES or RES-ARG. Total ewe colostrum mass (g) at 3 h after parturition was greater (P ≤ 0.001) in CON than RES or RES-ARG. Lamb birth weight was greater (P = 0.04) in CON than RES ewes and tended (P = 0.10) to be greater in CON vs. RES-ARG. Lambs born to CON ewes had greater (P ≤ 0.03) BW than lambs from RES ewes at 7, 14, and 33 d postpartum. On day 19, lambs from CON and RES-ARG ewes both had greater (P ≤ 0.04) BW than lambs from RES ewes (12.0 and 11.5 vs. 10.3 ± 0.41 kg, respectively). Lambs born to CON and RES-ARG ewes had greater (P ≤ 0.04) ADG than lambs from RES ewes on day 19 (355.0 and 354.0 vs. 306.4 ± 15.77 g, respectively). Lambs from CON and RES-ARG ewes also had greater (P ≤ 0.02) girth circumference than lambs from RES ewes on day 19 (55.4 and 54.6 vs. 51.3 ± 0.97 cm, respectively). On day 54, lambs from RES-ARG ewes had greater (P = 0.003) curved crown rump length than lambs from RES ewes (99.8 vs. 93.9 ± 1.28 cm, respectively). Adrenal glands in lambs from CON dams had greater (P = 0.01) mass than adrenal glands in lambs from RES dams. Livers from lambs born to RES-ARG ewes weighed more (P = 0.05) than livers from lambs born to RES ewes. These results confirm our hypothesis that arginine supplementation during the last two-thirds of gestation can mitigate offspring, but not maternal negative consequences associated with restricted maternal nutrition.
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http://dx.doi.org/10.1093/jas/sky221DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6095351PMC
July 2018
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