Animal Sciences Masters Theses

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Effect of Linseed Meal on the Reproductive and Digestive Tracts in Sheep
(North Dakota State University, 2007) O'Neil, Mathew Reid
To evaluate the estrogenic potential of secoisolariciresinol diglycoside (SDG) found in linseed meal (LSM) on visceral organ mass, uterine mass, jejunal cellularity, jejunal vascularity, and angiogenic factor expression in the jejunum, 48 multiparous, ovariectomized ewes were used in a 3 x 4 factorial. Ewes were fed a diet containing 12.5% LSM for 0, 1, 7, or 14 d and implanted with estradiol 17-ß (E2) for 0, 6, or 24 h before tissue collection. This study confirmed that LSM interacts with E2 to alter uterine and duodenal mass; that E2 is capable of altering liver, duodenal, and uterine mass; and that LSM is capable of altering liver and duodenal mass. In addition to altering organ mass, LSM interacted with E2, causing E2 to have no effect on cellular proliferation rate of the jejunum when LSM was fed for 1, 7, or 14 d, whereas cellular proliferation was increased in the duodenum in response to E2 when LSM was fed for 0 d. However, neither LSM nor E2 altered any measurement of vascularity. Expression of angiogenic factor mRNA was also examined. Implanting ewes with E2 for 6 h increased eNOS mRNA expression; whereas, LSM and E2 interacted to alter mRNA expression of its receptor, sGC, as well as VEGF's 2 receptors, FLT and KDR. Although this study confirmed LSM's ability to interact with E2, further research is needed to investigate its effects on intact cyclic animals as well as in pregnant animals and their offspring.
The Role of Distillers Dried Grains with Solubles in Sulfur Toxicity in Ruminants
(North Dakota State University, 2010) Neville, Bryan Wayne
One of the challenges with using ethanol co-products is the potential for increased dietary S concentration. Dietary S concentration has been implicated as a cause of polioencephalomalacia (PEM) in ruminants. The focus of this research was to evaluate PEM in ruminants fed distillers dried grains plus solubles (DOGS) based finishing rations. Two separate hypotheses were formed: 1) Providing increased dietary thiamin will decrease the incidence of PEM in lambs fed increased S diets without affecting animal performance; and 2) Feeding DDGS would increase concentrations of H2S gas and incidence of PEM compared to diets based on dry-rolled com. Two studies were conducted utilizing lambs to evaluate either 1) the influence of increasing supply of dietary thiamin (0, 50, 100, or 150 mg/d) on performance and incidence of PEM when fed diets containing 60% DDGS or 2) the influence of DDGS inclustion (0, 20, 40, or 60% DM basis) on sulfur balance. A third study was conducted using beef steers to examine the influence method of com processing (high-moisture vs. dry-rolled com) and concentration DDGS (20, 40, or 60% DM basis) on animal performance, H2S concentrations and incidence of PEM. Hydrogen sulfide gas concentrations were measured via rumenocentesis as lambs and steers were adapted from a receiving diet to a finishing diet. No differences in lamb performance were noted (P 2: 0.17) when diets containing increasing concentrations of thiamin were fed. Sulfur excretion increased (P :'S 0.01) with increasing dietary DDGS. Lambs fed elevated concentrations ofDDGS had a 3 fold increase in water intake and a 4.8 fold increase S excretion via urine compared to lambs fed no DDGS. Steer performance decreased (P :S 0.02) with increasing concentration of DDGS. Hydrogen sulfide gas concentrations did not differ (P 2: 0.06) until d 14 when lambs fed 60% DDGS had greater H2S concentrations (0.23 ± 0.039 g/m3; P :S 0.006) than all other treatments. Lambs fed 60% DDGS continued to have greater (P :S 0.001) H2S gas concentrations throughout the adaptation phase compared to the other treatments. Lambs fed 150 mg ofthiamin per day and steers fed 60% DDGS had the greatest concentrations of H2S (1.07 g H2S/m3; P :S 0.009; 1.38 g H2S/m3, P :S 0.01), respectively). Ruminal H2S concentrations in steers were affected by increasing DDGS concentration in the diet (P < 0.001), but not by com processing method (P = 0.94). Ruminal pH was not affected by a day x treatment interaction (P = 0.65) or by treatment (P = 0.32), but decreased (P < 0.001) across the adaptation phase from 5.82 (d-7) to 5.33 (d 35) in lambs fed increasing concentrations of DDGS. The use ofthiamin as a dietary additive to aid in the prevention of PEM in finishing lambs does not appear to be necessary under the conditions of this study. Com processing did not influence animal performance or H2S concentrations in our study. Steer performance decreased when DDGS level was> 40% (DM basis); however lambs fed 60% DDGS had similar performance compared to lambs fed lesser amounts ofDDGS. The role dietary S from DDGS plays in incidence of PEM is questionable as no cases of PEM were observed with dietary S concentrations exceeding 2-3 times the maximum tolerable level. Additional research may be needed to clarify species specific observations and responses to dietary S levels.
Evaluation of Feedlot Cattle Health Relative to Carcass Quality
(North Dakota State University, 2010) Jeske, Theresa Mae
The objective of this study was to investigate the effects of Bovine Respiratory Disease (BRD) and liver condemnation on beef carcass traits. Health treatment records for 2534 animals from a North Dakota feedlot were obtained and evaluated as evidence of BRD. Lung Lesions (n = 291) and lung condemnations (n = 1710) at slaughter where also evaluated as an indicator ofBRD. Liver condemnation (n = 2298) at slaughter was also considered in the analysis. Traits measured were hot carcass weight, USDA Quality Grade, USDA Yield Grade, ribeye area, marbling and lih rib fat thickness. All cattle were evaluated by experienced feedlot personnel and treated according to a health protocol utilized by the feedlot. The incidence rate of BRD was observed as affecting 3 .40% of the feedlot population. USDA Quality Grade (P = 0.001) and hot carcass weight (P = 0.07) were decreased for cattle treated for BRD. Cattle with lung condemnation at slaughter had a tendency for lower hot carcass weights. Conversely, marbling (P = 0.04) and lih rib fat thickness (P = 0.04) was increased for cattle with lung condemnations at slaughter. Ribeye area was decreased (P = 0.004) for cattle with liver condemnations at slaughter and cattle with liver condemnations had increased USDA Quality Grades (P = 0.03). The presence of any one particular measurement did not significantly affect all carcass traits measured; however, the relationships between health parameters and carcass traits may be considered in future research in specific carcass traits.
The Effects of Arginine on Reproductive Performance in Ewes
(North Dakota State University, 2010) Saevre, Chelsey Brie
Reproductive performance is the largest determinant of income in the livestock industry. In the U.S. sheep industry, embryonic and fetal deaths during pregnancy account for almost half of the total number of fertilized ova and a majority of these losses have been reported to occur before d 18. In study 1, the objective was to determine if arginine supplementation enhances ovarian function and prevents early reproductive losses in sheep. Ewes received L-arginine HCI (equivalent to 27 mg of L-arginine/ kg of BW, ARG, n = 20) or saline (CON, n 20) i.v. from d O (estrus) to d 15. On d 12, serum concentrations of arginine (nmol/ml) were elevated in ARG vs. CON ewes at O (P < 0.001 ), 0.5 (P < 0.001 ), 1 (P < 0.001 ), 2 (P < 0.005 ), and 4 h (P < 0.05), but were similar (P > 0.05) at -0.5, 8 and 24 h. Pulsatility index in the ovarian artery on d 12 was reduced in ARG vs. CON ewes (P < 0.05). Despite similarities in the number of corpora lutea (CL) per ewe (P > 0.05), ARG ewes had greater P4 concentrations throughout treatment compared to CON ewes. Although pregnancy rate was not influenced (ARG, 55% and CON, 60%; P > 0.05), ARG ewes had more embryos per ewe (P:::; 0.04) and less CL not represented by embryos (P '5 0.03) compared to CON ewes at d 25 of pregnancy. Ewes treated with ARG gave birth to more lambs when compared to control ewes (ARG, 1.6 ± 0.16 vs. CON, l. 1 ± 0.16 lambs born per ewe). In summary, early reproductive losses can be prevented by treatment with arginine. The objective of Study 2 was to determine if arginine supplementation surrounding the time of maternal recognition of pregnancy enhances ovarian function and minimizes reproductive losses. Ewes received L-arginine HCl ( equivalent to 27 mg of L- arginine/kg of BW, ARG, n= 47) or saline (CON, n = 47) i.v. from d 9 to d 14 following estrus ( d 0). On d 10, serum concentrations of arginine (nmol/mL) were elevated in ARG versus CON ewes at O (P < 0.001), 0.5 (P < 0.001), 1 (P < 0.001), 2 (P < 0.001) and 4 h (P < 0.001 ). Despite similarities in the number of CL per ewe (P > 0.05), serum progesterone concentration (ng/mL) was greater in CON compared with ARG on d 9 (P < 0.02) and I 0 (P < 0.005). Treatment with arginine influenced pregnancy rate (ARG, 55% and CON, 30%) throughout the treatment period. Ewes treated with ARG gave birth to similar (P > 0.05) number of lambs when compared to CON ewes (ARG, 1. 78 ± 0.17 vs. CON, 1.6 ± 0.27 lambs born per ewe). In summary, arginine supplementation surrounding the time of maternal recognition of pregnancy may prevent early reproductive loss or influence vascular resistance and circulating serum progesterone concentration in ewes. In study 3, the objectives were to determine if rumen-protected arginine supplemented to ewes on d 8 to 13 of the estrous cycle affected serum amino acid concentration, ovarian blood flow, and circulating progesterone. Ewes fed 360 mg/kg BW arginine (360 ARG) had greater serum arginine concentration than control (CON), 90 mg/kg BW arginine (90 ARG), and 180 mg/kg BW arginine (I 80 ARG) on d 11 (P < 0.07) and d 12 (P:::: 0.03 ). Arginine supplementation increased peak systolic velocity in the CL for 360 ARG and 90 ARG compared to CON (P < 0.04). Supplemental rumen-protected arginine had no effect on serum concentration of progesterone (P > 0.50). Results indicate that rumen-protected arginine supplemented to ewes at the rate of 360 mg/kg B W may increase circulating serum arginine concentration, in addition to increasing ovarian blood flow.
Characterization of Salmonella spp. Isolated From Beef Cattle Post-Weaning To Slaughter
(North Dakota State University, 2010) Nesemeier, Brenton Fred
The occurrence of Salmonella in cattle has been well documented, but little is known of tracking its prevalence and antimicrobial resistance (AMR) from postweaning to slaughter. This study follows a longitudinal approach, allowing for the best analysis of Salmonella prevalence and AMR in cattle. It was carried out to monitor variation in Salmonella prevalence and AMR patterns in beef cattle from range (calves post weaning in North Dakota (ND)) and feedlot cattle up to slaughter (Nebraska). Two separate groups were analyzed, cattle which remained at the Dickinson Research Extension Center (DREC) throughout the course of the study and calves which initially were housed at the DREC, then transferred to a University of Nebraska Feedlot, where they remained until slaughter. Fecal samples were taken four times over a sampling period of eleven months, September 2008-July 2009; a mid-line sponge sample was taken of the steers before slaughter. Laboratory culture of fecal and sponge samples for Salmonella followed a standard published procedure. National Antimicrobial Resistance Monitoring System (NARMS) panels were used for AMR testing of Salmonella isolates. Additionally, PCR was performed to determine the prevalence of the lntegrase 1 gene in the Salmonella isolates and presumptive integrase positive isolates were further analyzed for the presence of a conserved sequence. Overall, the prevalence of Salmonella ranged from 7.9% to 92.1% in adult cattle throughout the study. The prevalence of Salmonella in calves at post weaning ranged from 27.7% to 54.4%, with one month, December 2008, displaying 100% prevalence. At the final sampling of calves, which included a midline sponge sample along with a fecal grab, the prevalence of Salmonella was 45.8% and 46.8%, respectively. Salmonella isolates displayed the highest rate of resistance towards chloramphenicol {57.3%), streptomycin (54.7%) and tetracycline {54.7%) in both groups. Overall, the integrase 1 gene was isolated from 100 (50.0%) isolates, with 88 (44.0%) isolates harboring a conserved sequence. In conclusion, this study provided data on AMR patterns of Salmonella shed by beef cattle at the different stages of production. Also, an association between AMR towards the various antimicrobials tested and presence of integrase 1 on the Salmonella isolates recovered was investigated providing some information on the mechanisms of resistance to these antimicrobials. However, further research is necessary to quantify other resistance mechanisms that weren't explained by this study. Most importantly, this research contributes information to the scientific literature on Salmonella prevalence and AMR risk assessment in the beef cattle food chain that can allow for development of appropriate control measures.
Effects of Linseed Meal on Growth and Reproductive Performance in Ruminants
(North Dakota State University, 2011) Ilse, Breanne Rose
Linseed meal (LSM) was fed to ovariectomized ewes exposed to estradiol 17-ß (E2) implants over time, and LSM was supplemented to beef cows during late gestation and early lactation to evaluate the estrogenic potential of the phytoestrogen secoisolariciresinol diglycoside (SDG) found in LSM. Forty-eight ovariectomized ewes were fed a diet containing 12.5% LSM for 0, 1, 7, or 14 d and implanted with estradiol-17ß (E2) for 0, 6, or 24 h before tissue collection. Uterine cellular proliferation, vascularity, and the expression of the angiogenic factors and their receptors were recorded. There was an interaction of LSM and E2 on uterine mass (P = 0.05). At 24 h of E2 exposure, proliferation was reduced (P < 0.001) when ewes were fed for 14 d compared to being fed 0 or 1 days. There was a LSM x E2 interaction (P ≤ 0.03) on VEGF receptor-2 (KDR) and hasicfihrohlast growth factor receptor (FGFR2) decreasing by 24 h E2 exposure. Exposure of LSM and E2 may impact the estrogenic response of sensitive tissue. Two studies were conducted to examine the effects of supplementing beef cows with LSM during late gestation or early lactation on calf growth and development. In Experiment 1, multiparous cows received either LSM or a control (CON) supplement (approximately 10% diet dry matter) for the last 60 d of gestation. Offspring weights, ADG, heifer age at puberty, conception percentage and steer carcass characteristics were recorded. In Experiment 2, multiparous cows received LSM or CON supplements (approximately 10% diet dry matter) during the first 60 d of lactation, and only heifer calf development performance was observed and recorded. Heifer calf weight, average daily gain, and attainment of puberty were assessed. For both experiments, birth weight, weaning weight and ADG were not affected (P > 0.31) by LSM supplementation. While final body weights were heavier (P = 0.04) for steer calves in Experiment 1, there was no effect (P = 0.09) of supplementation on carcass characteristics. In Experiment 1 and 2, attainment of puberty in heifer calves was not influenced (P > 0.58) by supplement type. Linseed meal supplementation during late gestation or early lactation does not appear to have a negative impact on calf growth, onset of puberty in heifer calves, or steer carcass quality, implicating that it may make a good supplement choice in cattle.
Effect of Maternal Metabolizable Protein Supplementation During Late Gestation on Fetal Visceralorgan Weight with Application of Proteomics to Investigate Skeletal Muscle Development in Sheep
(North Dakota State University, 2012) Schwartz, Christina Anne
The experiment investigated supplementation of maternal metabolizable protein in an isocaloric diet during late gestation on fetal organ growth and skeletal muscle development in sheep. Although fetal body weight was unaffected by treatment, visceral organ weights were sensitive to MP treatment as alterations in small intestinal mass and perirenal adipose tissue content suggest impacts on postnatal growth. Two-dimensional gel electrophoresis and mass spectrometry compared the sarcoplasmic and myofibrillar protein fractions of fetal skeletal longissimus muscle, identifying spots from the sarcoplasmic and myofibrillar protein fractions (30 and 12, respectively). Increased expression of fructose-bisphosphate aldolase in fetal muscle from protein-supplemented and protein-restricted ewes when compared to those from control ewes suggests a positive influence on rate of glycolysis and muscle turnover in these offspring. Further research on maternal supplementation with metabolizable protein in isocaloric diets is needed to improve fetal growth efficiency, thereby optimizing offspring performance.
Effects of Alternate Day Feeding of Dried Distiller’s Grains Plus Solubles and Grass Hay on Metabolism and Performance in Cattle
(North Dakota State University, 2012) Klein, Sharnae Ivon
Two studies were conducted to determine the effects of supplementing dried distiller's grains plus solubles (DDGS) on alternate days to forage-fed cattle. We hypothesized that feeding either DDGS at a low percent of body weight or a moderate to low quality hay on alternate days would decrease forage intake without negatively impacting rumen kinetics and digestibility in steers as well as body weight and body composition in gestating cows. Therefore the objective of these research trials was to examine the effects of alternate day feeding of DDGS and grass hay on ruminal and digestion kinetics in Holstein steers (EXP. 1) and performance in gestating beef cows (EXP. 2). In both research experiments a decrease of total forage DMI was observed (EXP. 1; P = 0.0004 and EXP. 2; P < 0.0001) for cattle allotted to the alternate day feeding of DDGS and grass hay.
Efficacy of Various Five-Day Estrous Synchronization Protocols in Sheep
(North Dakota State University, 2012) Jackson, Christen Georgia
The objective of this study was to determine the effects of various estrous synchronization protocols utilizing the five-day controlled internal drug releasing (CIDR) inserts that are infused with progesterone (P4) alone and when coupled with gonadotropin-releasing hormone (GnRH) and prostaglandin (PG) during different breeding seasons. Ewes received either 1 of 4 treatments: 1) Untreated (U); 2) 5 d CIDR (0.3 g P4) insert (C); 3) 5 d CIDR and PG at CIDR removal (d 0, P); or 4) GnRH at 5 d CIDR insertion and PG at CIDR removal (G). In Experiment 1, overall days to estrus were greater (P ≤ 0.01) in U and P compared with C. In Experiment 2, overall days to estrus were greater (P ≤ 0.02) in U and P compared with G. In summary, the 5 d CIDR reduces the number of days required to bring ewes into estrus when compared to untreated ewes.
Evaluation of a Novel Means to Euthanize Piglets
(North Dakota State University, 2012) Miller, Richelle Lorraine
Research was conducted to evaluate a novel means to euthanize piglets utilizing electromagnetic energy. Experiment 1 assessed if electromagnetic energy could result in a euthanized piglet and Experiment 2 evaluated states of consciousness of piglets. During Experiment 1, six piglets were exposed to 40 seconds of electromagnetic energy (EME). Respiration rate was reduced to zero in each piglet immediately following EME and unassisted death occurred after heart rate ceased within 4.8 minutes after EME in five of the six piglets. Treatments during Experiment 2 included EME for 3, 6, or 9 seconds. State of consciousness and treatment interaction affected (P < 0.01) electroencephalogram amplitude and power. State of consciousness affected (P < 0.01) electroencephalogram frequency and heart rate. Treatment and EME interaction also affected internal body and head surface temperatures (P < 0.01). Piglets exposed to 9 seconds EME had higher (P < 0.01) body temperature compared with other treatments.
Effects of Maternal Nutrition, Intrauterine Growth Restriction (IUGR), and Estrogen (E2) Supplementation on Placental and Fetal Intestinal Growth and Development in Sheep
(North Dakota State University, 2012) Yunusova, Roza
The placenta and fetal intestines are two key nutrient transport organs that sustain and nurture growing fetus. Insufficient placental development and consequently inadequate fetal nutrient supply can lead to IUGR resulting in low birth weight offspring. Our experimental objectives were to investigate the effects of elevated maternal nutrition, IUGR, and E2 supplementation during mid-gestation (in an attempt to rescue IUGR offspring) on placental and fetal intestinal cell proliferation, angiogenic gene expression, and vascularity. Limited responsiveness in placental development and vascularization to E2 supplementation was observed, likely due to inappropriate timing or dose of E2. However, maternal E2 supplementation increased fetal small intestinal length and GUCY1b3 mRNA expression, suggesting that E2 supplementation has positive effects on IUGR fetal intestinal growth. In conclusion, understanding molecular mechanisms associated with IUGR and possible effects of E2 supplementation in rescuing IUGR may lead to enhanced human health and livestock production efficiency.
The Relationship between Pre-Harvest Stress and Carcass Characteristics and the Ability to Qualify for Kosher on Beef Steers and Heifers
(North Dakota State University, 2013) Hayes, Nathan Scott
The objective of this study was to determine if there is a difference in pre-harvest stress and carcass characteristics between kosher and not-qualified-as kosher cattle. Cattle that had a shorter time from gate to exsanguination and a lower vocalization score were more likely to qualify for kosher. Kosher carcasses had a larger REA, a higher WBSF value, tended to have a heavier HCW. At each individual day, kosher steaks had lower L*, a*, and b* values. These data suggest that body composition and stress level may play a factor in the likelihood of a beef animal to qualify for kosher, and there is a defined quality difference between kosher and nonkosher steaks.
The Effect of Artificial Insemination or Natural Service Breeding Systems on Reproductive Performance, Calving Characteristics, Weaning Characteristics, and Steer Backgrounding Performance in a Commercial Beef Herd
(North Dakota State University, 2013) Steichen, Philip Lee
Two experiments were conducted to evaluate the effects of beef cattle breeding systems that incorporate artificial insemination (AI) or breeding systems that use natural service mating on resultant reproductive performance, calving characteristics, weaning characteristics, and steer backgrounding performance. In Exp. 1, cows and heifers were assigned to 1 of 2 breeding season systems: 1) exposed only to natural service bulls (NS, n = 541) or 2) bred via AI on the first day of the breeding season, followed by exposure to natural service bulls (TAI, n = 535). Final pregnancy rates were similar among treatments. However, more calves were born within the first 21 d of the calving season resulting in heavier weaning weights of calves born in the first 21 d of the calving season for TAI compared with NS. In Exp. 2, steer progeny from females in Exp. 1 were evaluated in a 69 d backgrounding study. Though distinct performance advantages of TAI steers were not observed, calves born early in the calving season had greater feed intake and gain compared with calves born later in the calving season regardless of treatment.
Effects of Distillers Dried Grains with Solubles Supplementation to Yearling Heifers Grazing Northern Great Plains Rangeland: Impacts on Subsequent Feedlot Performance and Meat Quality
(North Dakota State University, 2013) Larson, Quynn
Eighty two yearling heifers (319.5 ± 1.03 kg) were utilized in a completely randomized design to evaluate the effects of distillers dried grains with solubles (DDGS) supplementation on animal performance while grazing on rangeland of the Northern Great Plains; and subsequent feedlot performance, carcass characteristics, and meat quality traits. Treatments were 1) 0% DDGS supplementation (CONT) or 2) 0.6% of BW DDGS supplementation (SUP). Heifers received treatments for 70 d while grazing then acclimated to and fed a common corn based finishing diet for 109 d. Carcass characteristics were assessed by trained personnel, and strip loins were transported back to North Dakota State University for retail display life, tenderness determination, and trained sensory panel. Supplementation of DDGS during grazing improved ADG of yearling heifers with no effect on feedlot performance or carcass characteristics, but did improve tenderness and steak sensory attributes.
National Retail Pork Benchmarking Study: Characterizing Pork Quality Attributes of Multiple Cuts in the Self-serve Meat Case
(North Dakota State University, 2013) Klinkner, Benjamin Thomas
The objective of this study was to benchmark fresh pork quality in the retail meat case in the United States. Nationally, 117 retail supermarkets in 67 cities were selected for sampling. Center-cut loin chops were observed in-store to obtain subjective color and marbling scores. Ten loin chop, sirloin chop, and blade steak packages representing each brand and enhancement type were purchased for objective analysis of pH, Minolta color (L*, a*, and b*), and tenderness (WBSF). For L*, enhanced loins were darker (P < 0.05) than non-enhanced. Enhanced loins and sirloins had greater (P < 0.05) pH values than non-enhanced chops. Enhanced loins, sirloins, and blades had lower (P < 0.05) WBSF scores than non-enhanced chops and steaks. This research provides retailers, processors, and other pork industry stakeholders with benchmark values of pork quality, and provides the pork industry with information to help reduce variation and improve pork quality at the retail level.
Impact of Environmental Factors on Ovarian Function and Endocrine Activity in Livestock
(North Dakota State University, 2013) Kaminski, Samantha
Ovarian function is important in reproductive efficiency since the ovary is the site of oocyte development, as well as production and secretion of hormones necessary for proper follicle development, ovulation, and maintenance of pregnancy. However, many environmental factors can affect female reproductive function. For example, physical exercise during gestation has previously demonstrated to increase availability of nutrients and oxygen to the developing offspring, decrease mortality rates, and increase birth weights. Unfortunately there is limited information regarding ovarian development and fertility of offspring born to exercised mothers. Nutrition has also been demonstrated to affect reproductive function by altering steroid and metabolic hormone concentrations which can overall affect ovulation rates, oocyte quality, pregnancy rates, and fetal development and survival. Therefore, the objective was to investigate how manipulation of certain environmental factors, such as exercise, diet, or arginine supplementation, can influence ovarian function and endocrine activity of female livestock species.
The Impact of Management Decisions and their Effect on Reproductive Performance of Beef Cattle
(North Dakota State University, 2014) Schook, Mellissa Renee
Two experiments were conducted to evaluate two management decisions made by beef cattle producers and their impacts on reproduction. In experiment 1, growth, attainment of puberty, and pregnancy rates were evaluated in crossbred heifers originating from two different breeding systems: 1) cows only exposed to natural service herd bulls (NS), or 2) cows exposed to ovulation synchronization and fixed-time AI followed by natural-service bulls (TAI, fixed-time artificial insemination). Artificial insemination did not influence growth rate during the development phase, attainment of puberty, or pregnancy rates in heifer progeny. In experiment 2, pregnancy attainment and calving distribution of beef females administered a control saline dose, killed virus, or modified-live pre-breeding vaccine per label recommendations were compared. No differences in pregnancy attainment were observed among the 3 time points measured, d 28, 56, and 90 as well as no differences seen among the calving distribution.
Body Weight and Adiposity Changes of Obese Gilts Provided Ad Libitum Ground Beef Versus High Carbohydrate Diets
(North Dakota State University, 2014) Wellnitz, Krista R.
This study investigated the impact of providing a red meat (GB; cooked ground beef; 63% lean) or high-carbohydrate diet (CON) on growth performance and body composition of obese gilts as a biomedical model for humans. Treatment differences were observed for total intake (kg consumed/d; P = 0.05), average caloric intake (calculated kcals/d; P = 0.003), BW change (P = 0.012), and a treatment by harvest day interaction (P = 0.001) for pancreas weight. Subcutaneous backfat measured adjacent the 10th thoracic vertebra expressed as a percentage change from d0 tended (P = 0.09) to be less in GB gilts. There was no evidence of cardiac ventricular inflammation across treatments (P > 0.21). Despite consuming more total feed and more calories, the GB gilts gained less BW and deposited less subcutaneous fat over 84 days. More research is needed to further understand the physiological effect of food on human nutrition and health.
Effects of Dietary Supplementation of Flaxseed and Metabolizable Protein on Reproduction in Mares and Ewes
(North Dakota State University, 2014) Swanson, Tara
Two experiments evaluated the effects of dietary supplementation on maternal reproductive parameters. In Experiment 1, 16 mares were assigned to dietary treatments: control, flaxseed, or linseed meal for 16 wk. Blood samples were analyzed for progesterone (P4), serum chemistry panel values, and fatty acids. Flaxseed supplementation increased (P < 0.01) alphalinolenic acid concentration, but treatment had no other effects. In Experiment 2, 45 multiparous ewes were allotted to dietary levels of metabolizable protein (MP): 60% (MP60), 80% (MP80), or 100% (MP100) from d 100 to d 130 of gestation. At d 130 ewes were slaughtered and tissues harvested. There was a day x fetal number interaction for P4, estradiol 17β, and thyroxine (T4) along with a treatment x fetal number interaction for T4. There was a day effect for cortisol and triiodothryonine. Results indicate dietary supplementation alters maternal parameters including hormones and fatty acids.
Influence of Maternal Nutrient Intake on Placental Vascular Function in Pregnant Beef Cows
(North Dakota State University, 2014) Reyaz, Arshi
We hypothesized that global maternal nutrient restriction during early and mid-gestation followed by realimentation in pregnant beef cows would alter placental arterial vascular function. We tested changes in placental caruncular (CAR) and cotyledonary (COT) arterial sensitivity to bradykinin (BK), a potent vasodilator. Cows were randomly assigned to be nutrient restricted for 55 or 110 during early to mid pregnancy. On d 85, 140, and 254 cows were euthanized and CAR and COT arteries were isolated. Maternal nutrient restriction during early and mid-gestation allowed for placental compensation to overcome the loss of nutrients while realimentation returned placental arterial vosoactivity similar to control cows in response to BK. Further, CAR and COT placental arteries may respond to BK induced vasodilation through different pathways which is important when considering possible therapeutics for compromised pregnancies.

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