Animal Sciences Masters Theses

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Dietary Impacts on Mitochondrial Respiration of Gestating Heifers and Fetal Offspring
(North Dakota State University, 2024) Slavick, Kathryn
Two projects were conducted to evaluate dietary impacts on mitochondrial respiration of gestating heifers and fetal offspring. Our first hypothesis was that maternal vitamin and mineral supplementation during gestation improves the liver, muscle, and jejunum mitochondrial function of F1 and F2 offspring. In project 1, vitamin and mineral supplementation was provided to the F0 generation of dams from breeding to calving to isolate the effects of nutrition during pregnancy on future generations. Our second hypothesis was that altering limit-fed diets' forage: concentrate ratio would influence mitochondrial respiration in maternal and fetal jejunum and liver. In project 2, replacement heifers were fed high-concentrate and high-forage diets to evaluate the dietary impacts on fetal cellular metabolism of key metabolic organs. In both project 1 and 2, modulations of metabolism occurred in key metabolic organs of gestating heifers.
Heat-treated Soybean Meal in Beef Cattle Diets
(North Dakota State University, 2024) Gullickson, Grady
Two experiments were conducted to evaluate replacing dried distillers grains with solubles (DDGS) with heat-treated soybean (TSBM) at increasing rates in forage-based diets on steer growth performance, nutrient flow, and digestibility. Experiment 1: 70 angus-based steers were utilized in a generalized randomized block design for an 85-d growing study at the NDSU Beef Cattle Research Complex. Experiment 2: five fistulated Jersey steers fitted with ruminal, duodenal, and ileal cannulas were utilized in a 4 × 5 row column design for 56 d to measure nutrient flow and digestibility. Diets were formulated to replace DDGS, included in the diet at 16% dry matter, with TSBM at 0 (TSBM0), 4 (TSBM4), 8 (TSBM8), and 12% (TSBM12) increments. Treatments had no effect on steer growth performance and residual carcass characteristics from the growing phase. Nitrogen, lysine, and available lysine total tract digestibility increased with increased TSBM inclusion however, post ruminal digestion decreased.
The Impact of Media on Price Paid for Thoroughbred Horses at Auction
(North Dakota State University, 2024) Anderson, Steven
It has been said a picture is worth a thousand words, but the economic value of that picture for livestock sales transactions has not been quantified. The objective of this study aimed to evaluate the effect of the presence of media (photos and/or video) on sale prices of Thoroughbreds. Online auction sale data from two U.S. Thoroughbred auction sites were used to compare 18,221 horses that sold and 4,215 horses that failed to meet the minimum desired bid. Sellers that provided media of their horses at auction received approximately $25,000 more for weanlings, $74,000 more for yearlings, and $89,500 more for older horses versus horses without media representation. Additionally, sellers increased their ability to receive a desired sale price for their horse when media was available for prospective buyers. In conclusion, availability of media prior to sale at auction will result in a greater sale price at every life stage.
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.
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.
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.
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.
Are Infrared Thermography, Automated Feeding Systems, And Heart Rate Variability Measures Capable of Characterizing Group-Housed Sow Social Hierarchies?
(North Dakota State University, 2022) Sommer, Dominique
Group gestation housing is becoming standard practice in commercial swine production. Although group housing promotes behavioral variability within the breeding herd, it can cause several management challenges for producers due to the establishment of the social hierarchy. Poor performance and welfare in group housed breeding stock can be attributed to the repercussions of aggression performed between dyads. The ability to quickly identify sows in the social hierarchy could be beneficial to producers for enforcing preventative actions. Precision livestock farming tools have proven to aid animal caretakers in monitoring animal health and welfare in livestock industries.The objective of this thesis was to investigate the use of infrared thermography, feeding activity obtained from an automated radiofrequency identification feeding system, and heat rate variability indices for detecting the social hierarchy within groups of gestating sows. Additionally, the relationship between observed social hierarchy, body condition scores, backfat, and reproductive performance was also explored.
Influence of Plasma Nuclear Magnetic Resonance Profile, Urea-Nitrogen, Glucose and Non-Esterified Fatty Acids on Dry Matter Intake in Developing Heifers and Mature Cows
(North Dakota State University, 2022) Olorunkoya, Samuel
The objective of this experiment was to determine if nuclear magnetic resonance (NMR) profiles or blood metabolites could explain dry matter intake (DMI) in developing heifers and/or mature cows in the weeks leading to breeding. A total of 335 heifers and 60 cows were fed a forage-based diet. A general linear model (GLM) was fit for DMI using fixed effects; breed, frame size, birth year. Non-esterified fatty acids (NEFA) had the greatest association with DMI (R2 ranged from 54.4% to 58.1% and 64.4% to 70.6%) in heifers and cows, respectively. The NMR profiles accounted for the smallest amount of variation (51.9% and 55.6%) for rumen metabolism and (52.0% and 55.8%) for cellular metabolism in heifers and cows, respectively. Additional exploration of how to profile NMR data is needed. The models containing NEFA accounted for high levels of variation, where fit plots indicated these predictions could be used to manage animals in distinct groups for DMI.
Evaluation of Beef Cattle Temperament Using Infrared Thermography and Computer Vison Imaging Technologies
(North Dakota State University, 2022) Ogdahl, William
The aim of these studies are two-fold. The first, was to evaluate the use of infrared thermography (IRT) maximum, average, and minimum eye temperature (IRTMIN, IRTAVG, and IRTMAX, respectively) and percentage of eye white area (EW) to predict beef cattle temperament by assessing the relationship between IRT and EW traits with 4 established subjective and objective temperament scoring methods (n = 16 traits total). The second was to verify the feasibility of Video Technology (VT) as a measure of beef cattle temperament with minimal equipment and personnel and assess the accuracy and reliability of the VT measurements by comparing those with Temperament Score (TS) and Docility Score (DS). These studies showed potential in using eye white and video technology to objectively predict beef cattle temperament.
Evaluation of the Relationship Between Size, Feeding Behavior, and Feed Efficency in Beef Cattle
(North Dakota State University, 2022) Mosher, Macie
Feed efficiency in cow-calf operations can be influenced by multiple environmental and physiological factors. The current study examined the association between body size (weight, frame score, and volume), linear body measurements, and feeding behavior with different measures of feed efficiency in multiparous lactating beef cows. Prediction models for dry matter intake in cows using linear body measurements were also developed. Our findings indicate that body size measurements and feeding behavior may influence measures of efficiency. The inclusion of body measurements in prediction models of intake may serve as accurate and feasible methods for estimating intake of cows on farm. The associations between the traits measured may provide insight for further producing models to measure and predict efficiency traits that are easily accessible on farm. Body measurements and feeding behavior are two traits that should be accounted for when considering efficiency and selection criteria for cow-calf operations.
The Effect of Hemp Byproduct Supplementation on Beef Quality
(North Dakota State University, 2022) Gundersen, Kiersten
The supplementation of hempseed cake (hemp byproduct) could be considered an alternative protein and fiber source for ruminants such as cattle. Hempseed cake might be a successful alternative feed source due to cattle’s digestive abilities. Yet, the physiological effects caused by cannabinoids in hemp (cannabidiol [CBD] and (-)-Δ9-tetrahydrocannabinaol [THC]) are of concern. However, hemp with much less than 0.3% THC on a dry matter basis can remain a potential alternative feed ingredient. The objective of this study was to evaluate the significance of hempseed cake inclusion in a late finishing ration on carcass characteristics, meat quality characteristics, retail shelf-life, proximate analysis, and fatty acid profile of muscle food obtained from commercial beef heifers.
The Influence of Beef Carcass Weight on Troponin-T Degradation and Heat Shock Protein 70 in Two Different Muscles
(North Dakota State University, 2021) Nath, Supriya Deb
This study was aimed to assess how carcass size affects protein degradation in postmortem muscle and subsequent impacts on meat quality. Beef carcasses were randomly selected at slaughter and classified as heavy (> 430.9 kg; n = 22), average (351.5 to 385.6 kg; n = 23), or light (< 317.5 kg; n = 20). Troponin-T (TnT) and heat shock protein 70 (HSP70) were analyzed for protein abundance on 3-day aged longissimus (LD) and semimembranosus (SM) muscles and 14-day aged LD muscle. TnT degradation in heavy carcasses was greater in the d-3 SM muscle and less in the d-14 LD muscle. Carcass size was positively correlated with the 30 kDa TnT band in d-3 SM. Therefore, carcass size influenced the TnT degradation but had no influence on HSP70 protein activity in either LD or SM.
Use of Soybean Hulls in Drylot Cow-Calf Diets
(North Dakota State University, 2021) Moore, Rebecca Lynn
One hundred and twenty-one Red Angus beef cows were used to evaluate the effects ofsoybean hull inclusion in drylot beef cow diets. Cows were stratified by age, body weight (BW),and body condition score (BCS), and randomly assigned to treatment (n = 4 pens per treatment).Treatments included a control diet (CON) and soybean hull diet (SBH). Beef cow BW, BCS,ultrasound backfat (BF) measurements, colostrum quality, and milk production were evaluated.Beef calf performance was evaluated based on birth weight, weaning weight, ADG, andultrasound measurements of BF, rump fat, and ribeye area at weaning. Dam BW, BCS, and BFmeasurements were not affected (P ≥ 0.12) by treatment. Additionally, calf birth and weaningweights were unaffected (P = 0.30). The present study demonstrated that soybean hulls can beincluded in beef cow diets at 26% of dietary DM without altering cow and calf outcomes.
Estimating the Impacts of Litter Size and Non-Additive Genetic Effects on Ewe Longevity and Stayability in a U.S. Western Extensive Range Production System
(North Dakota State University, 2021) Oribamise, Babatunde Victor
Non-additive genetic effects are usually ignored in animal breeding programs due to data structure, computational limitations, and over-parameterization of the models. Non-additive genetic effects play an important role in the expression of complex traits in livestock species, such as longevity and stayability. Components of genetic variance for additive and non-additive genetic effects were estimated for longevity and stayability in U.S. Western ewes using pedigree relationship matrices. Litter size were also investigated for direct and maternal effects. For longevity, a larger proportion of phenotypic variance was explained by non-additive genetic effects than by additive effects for model A+D, indicating that including dominance genetic effects are important. Results suggest that inclusion of non-additive genetic effects in animal models is possible in estimating longevity and stayability and will improve selection accuracy and reduce overestimation of additive genetic effects.
The Effects of Late Gestational Exercise on Colostrum Quality and Neonatal Immunoglobulin Absorption
(North Dakota State University, 2021) Gavette, Juan Simon
To investigate the effects that late gestational exercise has on ewe performance and colostrum IgG levels, and to evaluate how it impacts neonatal serum IgG absorption and future performance, thirty-two multiparous Dorset ewes were divided into two treatment groups and were housed in individual pens. The treatment group was walked for thirty minutes per day, every other day from the start of the third trimester to lambing. The results indicate that colostrum IgG levels were significantly greater in exercised ewes compared to ewes held in confinement. Increased locomotion impacted pregnant ewe feed intake, body weight, and average daily gain. Gestational exercise did not impact lamb birth weight or weaning weight. There were no significant differences in serum IgG levels amongst lambs after colostrum consumption but there were in serum protein. Further research is needed to better understand how and why gestational exercise increased colostrum IgG levels.
Impacts of Added Roughage on Feedlot Performance, Digestibility, Ruminal Fermentation, and Ruminal pH of Steers Fed Wheat-Based Feedlot Diets
(North Dakota State University, 2021) Pickinpaugh, Wayde Janelle
Two studies were conducted to evaluate the inclusion of additional roughage in wheat-based diets containing modified distillers’ grains with solubles on feedlot performance (Study 1) and digestibility, ruminal pH, and ruminal fermentation characteristics (Study 2). Study 1 used 72 steers (391.6 ± 46.3 kg) and study 2 used 4 ruminally and duodenally cannulated steers (393.4 ± 33.0 kg). Feedlot performance and carcass characteristics, excluding marbling, were not affected by increasing roughage (P ≥ 0.20). Ruminal pH increased linearly (P < 0.01) as rate of roughage inclusion increased. Concentrations of acetate and butyrate increased, and propionate decreased in a linear fashion (P < 0.01), increasing acetate and butyrate to propionate ratio (P < 0.01) with increasing dietary roughage. Our data indicate that increasing roughage inclusion in wheat-based diets including modified distillers’ grains with solubles increased ruminal pH and shifted ruminal fermentation patterns without affecting feedlot performance.
The Milk Withholding Time of Salicylic Acid for Treatment of Digital Dermatitis in Dairy Cattle
(North Dakota State University, 2020) Wirt, Kelsey Marie
Digital dermatitis is a top cause of lameness in dairy cattle that results in ulcerative lesions on the feet. Topical salicylic acid has been shown to provide similar efficacy to the antibiotic drugs used previously, but there is no milk withholding time established in the United States. The objective of this study was to provide data in order to establish this withholding period. A secondary objective was to evaluate outcomes among treatments. Treatment groups were topical applications of the following drugs: salicylic acid paste, salicylic acid powder, and tetracycline. The lesions were scored at day 0, day 7, and day 28 post-treatment. Milk samples were collected the day before treatment, 4 hours, 8 hours, 24 hours, 36 hours, and 48 hours post-treatment. Results indicated that most cows did not show detectable levels of salicylic acid after 24 hours.
Impacts of Banamine Injection on Pain Responses of Either Rubber Ring Castrated and Tail Docked or Surgically Castrated and Docked Lambs
(North Dakota State University, 2020) Anderson, Paige Porter
Our hypothesis was that administering Flunixin Meglumine (FM) to lambs that were both rubber ring castrated and docked or surgically castrated and emasculator docked would decrease behavioral stress, serum cortisol, haptoglobin concentration, and wound and swelling score, but increase average daily gain. Rambouillet ram lambs (n = 181) were allocated with a completely randomized design in a 2 x 2 factorial arrangement of treatments. Treatment combinations included rubber ring castration and docking (on ram lambs with administration of saline or FM) or surgical castration and emasculator docking (on ram lambs with administration of saline or FM). Ram lambs were castrated at 12.5 ± 5.5 days of age. Overall, results indicate that the method of castration and docking in lambs affected short lived behavioral and physiological stress. The administration of FM surgical castration following castration decreased cortisol levels after 140 minutes. Economic analysis showed that rubber-ring castration was the cheaper method.
The Effects of Estrus on Dry Matter Intake and Feeding Behavior in Beef Heifers of Divergent Sizes
(North Dakota State University, 2020) Underdahl, Sarah Rose
The biological process of estrus in cattle is known to initiate behavioral responses as a result of fluctuations in hormones, which may alter time budgeted for feeding. The current study aimed to quantify these variations that may exist in feed intake and behaviors in the days pre and post estrus. For this study, 517 estrous cycles in crossbred beef heifers of divergent sizes were used to analyze the impact of estrus behavior on feeding behavior with or without the presence of a bull. There were few differences in estrus behavior among heifers of divergent sizes, however the presence of a bull influenced all estrus activity parameters. Our findings indicate that feed intake and behaviors were sharply decreased on the day of estrus, but returned to baseline levels the following day. Thus, decreases in feed intake and behavior may serve as an additional tool indicating the onset of estrus.

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