PS4-13. Evaluation of Intake Consistency and Relationships with Feedlot Cattle Growth Performance and Carcass Characteristics

Journal of Animal Science · 2026-04-01

Abstract Feed intake consistency is a key indicator of efficiency in beef cattle. Understanding how intake variation relates to growth and carcass traits can help identify animals with more resilient production performance. The objective of this study was to evaluate the impact of dry matter intake consistency on beef cattle growth performance and carcass characteristics. Over 55 days, crossbred Angus steers (n = 157) were fed a feedlot diet consisting of corn silage, distillers grains, high moisture corn, and ground corn. Individual dry matter intake (DMI) was recorded using the Vytelle feed intake system. The expected DMI was calculated based on the average over the experiment. Dry matter intake consistency was estimated using six metrics, including variance of residuals (VR), maximum drop (MD), cumulative deficit (CD), days below baseline (DBB), longest deficit streak (LDS), coefficient of variation (CV), and minimum DMI residual Z-score (MZS). The VR was defined by the difference between the actual DMI and the predicted DMI. The MD was defined by the highest amount below the predicted baseline on a particular day. CD was defined as the sum of all negative fluctuations around the baseline of predicted feed intake. The DBB was defined as the percentage of days steers spent below the predicted feed baseline. The LDS was defined by the sum of the longest number of consecutive days spent below the predicted intake baseline. The Z-score is calculated by taking the difference between the minimum and the mean DMI residuals over the standard deviation and is used to explain the variation in data relative to the minimum residual DMI. The feeding consistency traits were correlated with backfat (BF), yield grade (YG), hot carcass weight (HCW), marbling, rib eye area (REA), and kidney, pelvic, and heart fat (KPH). The correlation was performed using Pearson's correlation method, and a significant correlation was achieved with P-values ≤ 0.05. Results show that VR has a positive correlation with BF, YG, and HCW. VR has a negative correlation with KPH and REA. CD has a positive correlation with KPH and REA. CD has a negative correlation between BF, YG, and HCW. LDS has a negative correlation with marbling and REA (r = -0.19). CV has a negative correlation with REA (r = -0.26). In conclusion, DMI consistency may moderately affect growth performance and carcass characteristics in beef cattle.

PS4-11. Effects of Ad Libitum Creep Feed Access on Calf Behavior Following Feeding of Cow Total Mixed Ration in a Confinement Cow-calf System

Journal of Animal Science · 2026-04-01

Abstract The objective was to evaluate the effects of providing ad libitum creep feed in a confinement system on calf behavior following feeding of cow total mixed ration. Spring-calving, Simmental × Angus cows (4.7 ± 1.7 yr; n = 36) were allotted to six partially covered, drylot pens with six cow-calf pairs per pen. Cows were limit fed a total mixed ration (TMR) at maintenance. Cow-calf pairs were stratified by cow sire and initial cow body weight (BW; 647 ± 94 kg) and calf BW (176 ± 18 kg; 119 ± 11 days of age). Three pens were randomly assigned to each treatment: ad libitum creep feed access for 21 days (CF), or no creep feed access (NCF). During a 3-week creep feeding period, a single observer recorded behavior observations from the alleyway in front of the pens three times per week. Data were averaged across all nine observation days for analysis. Each observation day began at time of feeding, and calf behavior was evaluated every 10 min for 70 min. Calf behaviors recorded included lying or standing and their location: cow TMR bunk, cow TMR feeding area, bedded area, or open lot area. Data were analyzed using the GLIMMIX procedure with a beta distribution in SAS 9.4. There was no treatment × time interaction (P = 0.98) for percentage of calves lying or standing. However, there was a greater (P = 0.01) percentage of CF calves that were lying compared with NCF calves. There was a treatment × time interaction (P = 0.01) for calves at the cow TMR bunk. Less CF calves were located at the cow TMR bunk than NCF calves at 0, 20, 30, 40, 50, 60, and 70 minutes after feeding. There was a treatment × time interaction (P = 0.01) for calves in the cow TMR feeding area. From 10 to 70 minutes after feeding, there were fewer CF calves in the cow TMR feeding area than NCF calves. There was no treatment × time interaction (P = 0.67) for percentage of calves in the bedded area. However, there was a greater (P = 0.01) percentage of CF calves that were in the bedded area compared with NCF. There was a treatment × time interaction (P = 0.01) for calves in the open lot area. At 0 and 70 minutes after feeding, there was a greater percentage of CF calves in the open lot area, and at 10 minutes after feeding there tended to be more CF calves in the open lot area. Offering ad libitum creep feed reduced calf proximity to the cow TMR bunk after feeding, suggesting creep-fed calves were less interested in competing for additional feed resources.

Performance, thermoregulation, and liver function in beef heifers exposed to endophyte-infected or endophyte-free tall fescue under a common environment

Translational Animal Science · 2026-01-01

Abstract Fescue toxicosis, induced by ingestion of ergot alkaloids from endophyte-infected tall fescue, remains a significant challenge to beef cattle production. This study evaluated the effects of fescue toxicosis on performance, thermoregulation, and liver metabolism in beef heifers maintained under the same experimental conditions as non-exposed controls. Twenty-four commercial Angus heifers were randomly assigned to a diet containing either an endophyte-infected (E+) or endophyte-free (E−) seeds for 49 days. Heifers were allocated to balance genetic representation across the two dietary groups to minimize genetic confounding. Environmental data, including temperature and relative humidity, were continuously recorded, and minimum, mean, and maximum temperature-humidity index (THI) were calculated each day. Two heatwave events occurred during the trial. E + heifers exhibited reductions in dry matter intake (DMI), feeding rate, meal size, average daily gain (ADG), and body weight, and elevated respiration rate and rectal temperature compared to E− heifers (P <0.05). Physiological impairments emerged within the first two weeks of exposure, with a subsequent heatwave exacerbating stress in the E + group. Among the three THI metrics evaluated, minimum THI showed the strongest negative correlation with DMI (r = −0.20). The two heatwave events coincided with notable reductions in DMI across both dietary groups. However, DMI was more severely suppressed in E + heifers compared to the E− group. Serum analysis revealed elevated aspartate aminotransferase (AST) and reduced alkaline phosphatase (ALP) and cholesterol levels in E + heifers, indicating liver stress and metabolic dysfunction (P <0.05). No significant differences were observed in serum albumin, bilirubin, gamma-glutamyltransferase (GGT), or triglyceride levels between groups. Collectively, these findings underscore the complex metabolic and physiological disturbances triggered by ergot alkaloid exposure, which compromise heifer health, thermoregulation, and productivity, particularly under heat stress conditions.

PS4-3. Effects of Heat Stress on Respiration Rate and Behaviors During Different Times of Day

Journal of Animal Science · 2026-04-01

Abstract The objective was to evaluate the effects of time of day during a heat stress event on cattle respiration rates and behaviors. Angus and Angus × Simmental beef heifers (n = 140; BW = 249 ± 24 kg; BCS = 5.1 ± 0.33) and cows (n = 49; BW = 450 ± 29 kg; BCS = 5.8 ± 0.43) were observed for nine days and three different time periods during two heat stress events. Four pens of heifers (32, 34, 36, and 38 heifers/pen) and two pens of cows (24 and 25 cows/pen) were observed in the same sequence three times within a day (0900, 1200, and 1500). Pastures averaged approximately 2 – 2.25 hectares and were composed of predominately endophyte-infected tall fescue. Respiration rate and behavior observations (grazing, ruminating, standing, lying, and under shade) were utilized to determine potential changes in cattle activity. Behaviors are shown as percentages and are not mutually exclusive. Active rumination was determined by cattle standing or laying and actively ruminating. A third of the animals within a pen were selected to provide a representative sample for a pen respiration rate. Breaths were counted by two observers utilizing binoculars for 15 seconds. The respiration rate from each observer was multiplied by four to calculate breaths/minute and averaged. Data were analyzed using the MIXED procedure of SAS 9.4. There was a time-of-day effect on respiration rate (P = 0.01). Respiration rates increased from 91 breaths/min at 0900 to 109 breaths/min at both 1200 and 1500, indicating a physiological response to rising ambient temperature and humidity throughout the day. There was no time-of-day effect (P ≥ 0.14) on grazing, ruminating, lying or standing behaviors. There was a difference (P = 0.01) in time of day on the percentage of cattle under shade. The percentage of cattle seeking shade was greater at 1200 and 1500 compared to 0900. As the day progressed and environmental conditions worsened, respiration rates and the percentage of cattle seeking shade increased which identified the physiological and behavioral adaptations utilized to potentially minimize the effects from the heat stress event.

Predicting body weight and efficiency traits in beef cattle based on depth image data

Frontiers in Animal Science · 2026-03-20

Advancements in sensor technologies have enabled the development of automated, non-invasive, and cost-effective phenotyping tools capable of capturing novel traits relevant to livestock management and genetic selection. The objective of this study was to compare the performance of different analytical approaches for predicting body weight, dry matter intake, and feed efficiency-related traits in beef cattle using image-derived biometric traits, assess the relative contribution of individual biometric traits to the predictive performance, and evaluate how the number of images per animal and image selection strategy affect model performance. A total of 196 commercial Angus steers were video recorded using a RealSense™ D455 depth camera, from which the biometric body traits projected volume, surface area, length, width, and height were extracted. These traits were used as predictors in several analytical approaches, including linear regression, partial least squares, elastic net, random forest, support vector machine, gradient boosting machine, and neural networks. Model performance was evaluated using leave-one-out cross-validation. Across all traits, linear regression achieved performance comparable to or exceeding more complex models (e.g., random forest, gradient boosting machine) while offering greater interpretability and computational efficiency. Body weight was predicted with high predictive performance (R 2 = 0.96; MAE = 10.12 kg) using projected volume, flat surface area, and body length, whereas dry matter intake was moderately predicted (R 2 = 0.59, MAE = 0.602 kg) using projected volume and flat surface area. In contrast, image-derived biometric traits showed limited ability to predict residual feed intake, residual average daily gain, or residual intake and body weight gain (R 2 < 0.01). Prediction accuracy was highest when biometric traits were summarized across all available images per animal, although comparable performance was achieved using one or more randomly or centrally selected images. Overall, these results demonstrate that image-derived biometric traits can accurately predict body weight and provide informative predictors of dry matter intake, with limited predictive value for the feed efficiency traits investigated in this study. These findings demonstrate that image-derived biometric traits provide a scalable, non-invasive phenotyping approach that supports both management and breeding selection decisions in beef cattle.

PSIV-A-4 Evaluation of the correlation between anogenital distance and other body size phenotypes in beef heifers

Journal of Animal Science · 2025-05-01

Abstract The objective was to determine how anogenital distance (AGD) correlates to other body size phenotypic traits in beef heifers and if the relationships change from nine to twelve months of age. Reproductive success is one of the most important components in beef cattle production. The AGD is measured from the center of the rectum to the base of the clitoris. Shorter AGD has been associated with improved fertility in various species. Understanding the relationship between AGD and body size phenotypic traits is important for future breeding programs. Angus and Simmental ´ Angus heifers were weaned at 83±7 days of age (n = 121) or at 226±3 days of age (n = 9) and used in the analysis. After weaning, heifers rotationally grazed predominantly tall fescue pastures starting in April. Heifers were supplemented 1.36 kilograms of DDGS per heifer per day during the grazing season. Four monthly data collections took place from June to September, with heifers being 262±9 days of age at the time of the first collection. Phenotypes collected included heifer AGD, shoulder height, hip height, body length, and body weight. As the heifers were restrained in a squeeze chute with their tail held in an upright position, the AGD was measured using a digital caliper. Shoulder height was determined with a measuring stick from the withers to the base of the hoof, and hip height was determined from the hip bone to the base of the hoof. The body length was determined with a tape measure spanning from the point of the shoulder to the tail head. The association of AGD measurements and body size phenotypes were evaluated using the CORR procedure of SAS 9.4. Shoulder height was correlated to AGD (r ≥ 0.23; P ≤ 0.01) in 10-month-old and 11-month-old heifers but was not in 9-month-old and 12-month-old heifers (r ≤ 0.11; P ≥ 0.22). Hip height was correlated to AGD (r ≥ 0.17; P ≤ 0.05) in 10-month-old and 12-month-old heifers, but not in 9-month-old and 11-month-old heifers (r ≤ 0.11; P ≥ 0.21). Body length was correlated to AGD (r ≥ 0.19; P ≤ 0.03) in 11-month-old and 12-month-old heifers, but not in 9-month-old and 10-month-old heifers (r ≤ 0.10; P ≥ 0.24). Body weight tended to be correlated to AGD (r = 0.17; P = 0.06) in 9-month-old heifers, and was correlated to AGD in 10-month-old, 11-month-old, and 12-month-old heifers (r ≥ 0.21; P ≤ 0.01). In conclusion, anogenital distance is weakly correlated to body size phenotypic traits in beef heifers from nine to twelve months of age, with the most consistent relationships observed for body weight.

PSV-5 Impact of days on slats and locomotion score on growth performance of feedlot cattle

Journal of Animal Science · 2025-05-01

Abstract The objective was to assess the impact of days on slats and locomotion score in a slatted, indoor feeding facility on steer growth performance. Fall-born, SimAngus steers (n = 138) were stratified and randomly assigned to treatments: long days on slats (LDOS) or average days on slats (ADOS). The LDOS steers were weaned at 80 days of age, and spent 262 days on slats. The ADOS steers were weaned at 206 days of age, and spent 192 days on slats. All steers received a Revalor-XS implant and were managed as a group thereafter. Concrete slats were covered with rubber matting, and pens had a minimum stocking density of 3.1 m2 per steer. Steers were fed a common diet and individual daily feed intake was monitored using a Vytelle feed intake system. Dietary components consisted of corn silage, modified wet distillers grain, dry rolled corn, high moisture corn, and a ground corn-based supplement. Steers were fed lubabegron (36 mg/steer/day, Experior, Elanco, Greenfield, IN) for the final 50 days on feed. Prior to slaughter, steers were scored using the Step-Up Locomotion Scoring System (Zinpro). Steers with locomotion score 1 (LS1; n = 52) and locomotion score 2 (LS2; n = 55) were used in a post-hoc analysis in SAS 9.4 considering the effect of days on slats, locomotion score, and their interaction. There was an interaction observed (P = 0.02) for overall average daily gain; for LDOS steers, LS1 steers had a greater average daily gain than LS2 steers, while no effect was observed for ADOS steers. There was an interaction observed (P = 0.02) for overall dry matter intake (DMI); for LDOS steers, LS1 steers had a greater DMI than LS2 steers, but no effect was observed for ADOS steers. While no interaction was observed (P = 0.80) for DMI slope, LS1 steers had a greater (P = 0.03) slope than LS2 steers indicative of greater DMI over time. No interaction was observed (P = 0.99) for overall gain:feed; however, LS1 steers had a greater (P = 0.01) overall gain:feed. In conclusion, results indicated that LS1 steers had a greater DMI slope and overall gain:feed. However, an improved locomotion score only resulted in increased average daily gain and DMI when steers were fed for a longer period of time in a slatted-floor facility.

Effects of rye or triticale with or without crimson clover on forage biomass and quality, gestating beef female performance, and in situ degradation kinetics

Applied Animal Science · 2025-11-22

77 Effect of roughage inclusion in limit-fed cow rations on drylot-housed cow and calf performance

Journal of Animal Science · 2025-05-01

Abstract The objective was to determine the effects of roughage inclusion in isocaloric total mixed rations (TMR) fed to cows in a drylot system on cow performance, calf performance, manure score, and hygiene score. Spring-born Simmental × Angus cows (5±2 yr; n = 72 in yr 1, and n = 72 in yr 2) and their calves were stratified by cow age, calf sex, and body weight (BW) and assigned to 24 pens over two years (yr 1; n = 12, and yr 2; n = 12) with 6 cow-calf pairs per pen. Pens were randomly allotted to one of two treatments: moderate roughage inclusion (40%) TMR targeting dry matter intake (DMI) of 1.7% of BW (LimitTMR) or high roughage inclusion (60%) TMR targeting DMI of 2.1% of BW (BulkyTMR). The experimental unit was pen. Cow-calf pairs were housed in concrete drylots with open-front buildings with 4.7 m concrete bunks (0.8 m/cow). Cow BW and body condition score (BCS) were collected at d-1, d0, d76, and d77. Pre-wean calf BW were collected on d-1, d0, d76, and d77. Artificial insemination (AI) conception and milk production were also measured. Hygiene and manure scoring were conducted on d40 and 76 by 2 trained evaluators. Hygiene was scored on a 1-4 scale; 1 – no manure, 4 confluent plaque of manure. Cow hygiene was evaluated on the lower leg, udder, and upper leg and flank. Manure from each pen was scored on a 1-5 scale; 1 – very liquid consistency, 5 – firm fecal balls. Calves were weaned on d77 and transported to the University of Illinois Beef and Sheep Field Laboratory (Urbana, IL). A receiving diet was then fed for 42 d post-wean. During receiving phase, calf BW (d77 & d119), post-wean ADG, DMI, and G:F were measured. Data were analyzed using the MIXED procedure of SAS 9.4. There were no treatment differences in final cow BW (P = 0.27), pre-weaning calf BW (P = 0.89), and final BCS (P = 0.72). There were also no treatment differences in AI conception (P = 0.67) and milk production (P = 0.84). Treatment did not affect hygiene of the lower leg (P = 0.78), upper leg (P = 0.56), and flank (P = 0.93). Manure score was also not different (P = 0.63) between treatments. No treatment effects were observed in calf receiving ADG (P = 0.83), calf G:F (P = 0.16), and final receiving calf BW (P = 0.93). BulkyTMR calves consumed more (P = 0.05) feed than the LimitTMR calves in the receiving phase. There were no differences in cow or calf performance prior to weaning, but calves from cows fed a bulkier, higher-roughage inclusion TMR had greater intake during the receiving phase.

226 Anogenital distance in beef heifers: repeatability and measurement methods

Journal of Animal Science · 2025-05-01

Abstract The objectives were to determine the repeatability of collecting anogenital distance (AGD) and to compare measurement methods in beef heifers. The AGD is defined as the center of the anus to the base of the clitoris. Shorter AGD has been associated with improved fertility in various species. Conventionally, AGD has been determined using caliper measurements; however, additional methods of measurement may be available that provide increased practicality for producers. The AGD measurements were collected over four different time points from Angus and Angus×Simmental heifers. Heifers were weaned at 83±7 days of age (n=121) or 226±3 days of age (n=9). Heifers rotationally grazed predominantly tall fescue pastures starting in April and were supplemented with 1.36 kilograms of DDGS/ heifer per day. At the time of the first collection, the heifers were 262±9 days of age and measurements were evaluated monthly, June through September. During the measurement collections, heifers were restrained in a squeeze chute with the tail held upright and relaxed. Using the conventional method, measurements were collected with digital calipers and recorded manually. The photogrammetric method consisted of 2-dimensional photographs taken by an iPhone 12. A whiteboard with a photomacrographic scale and heifer identification number was included in the photos, held adjacent to the vulva. The images were set to scale and AGD was measured using the Digimizer software program. The stereo camera (Intel RealSense D455e) method utilized 3-dimensional images in only the August and September evaluations. Images were collected at a rate of 30 frames per second. An annotation software, CVAT, was used to locate the center point of the anus and the base of the clitoris. The YOLOv8 keypoint detection model was then trained using the annotated dataset to detect the points and measure the AGD automatically, correlating the points’ location and the camera’s distance to the vaginal region to transform the px dimension into cm. The associations of AGD caliper, photogrammetric, and stereo measurements were evaluated using the CORR procedure of SAS 9.4. Each pairwise comparison (n = 6) of monthly caliper AGD data was correlated (r ≥ 0.29; P ≤ 0.01), indicating repeatability throughout the evaluation period. Similarly, all pairwise comparisons of photogrammetric AGD measurements were correlated (r ≥ 0.23; P ≤ 0.01) and repeatable throughout the evaluation period. Within each month, photogrammetric 2-dimmensional AGD measurements had a moderate correlation (r ≥ 0.47; P ≤ 0.01) with the caliper AGD measurements. In August and September, stereo AGD measurements were strongly correlated (r ≥ 0.98; P ≤ 0.01) with caliper AGD measurements. In conclusion, AGD measurements were repeatable in beef heifers regardless of the measurement method. Photogrammetry, using 2-dimensional and 3-dimensional images, is a viable alternate method of collecting AGD, with 3-dimensional images being superior.