About

Dr. Gordon Carstens is a professor of animal nutrition in the Department of Animal Science at Texas A&M University. He earned his bachelor’s degree in animal science from Iowa State University, followed by a master’s and a Ph.D. from Colorado State University. Prior to his academic career, he worked for a major pharmaceutical company. His research focuses on energy metabolism and growth and development in ruminants, with specific interest in the regulation of growth and carcass and mammary tissue composition through nutritional control, as well as the use of externally administered growth regulators. Recent research efforts have been directed toward methods to enhance the ability of newborn calves to produce heat and withstand cold stress, along with investigating the influence of genetic and nutritional factors on this trait. Dr. Carstens is actively involved in teaching animal nutrition courses and conducts research aimed at improving livestock productivity and health.

Research topics

• Animal science
• Biology
• Computer Science
• Endocrinology
• Biochemistry
• Food science
• Psychology
• Social psychology

Selected publications

• Smart technologies for sustainable pasture-based ruminant systems: A review

  Smart Agricultural Technology · 2025-01-18 · 8 citations

  reviewOpen access

  Ruminant livestock farming is essential for providing high-value protein foods for humanity. Nevertheless, the environmental impact and sustainability of ruminant farming systems are under increasing scrutiny due to factors such as climate change and land degradation. Extensive pasture-based farming systems can mitigate these challenges, as they are associated with range of ecosystem services, although they are characterized by low efficiency and are labor-intensive and time-consuming. This review investigates the potential of Precision Livestock Farming technologies (PLF) to enhance the health, welfare, and productivity of grazing ruminants while minimizing environmental impacts. Precision Livestock Farming tools, such as GPS tracking, accelerometers, and virtual fencing, enable real-time monitoring of animal behavior, health, and pasture management, offering smart solutions to challenges such as overgrazing and greenhouse gas emissions. These technologies also enhance the integration of sustainable agronomic practices, like rotational grazing and nitrogen-fixing crops, which can improve soil health and reduce emissions. Despite these benefits, the adoption of PLF technologies in extensive pasture-based systems remains limited due to economic, technical, and infrastructural barriers. Further research is required to optimize PLF applications for various ruminant species, improve data accuracy, and scale these technologies for broader implementation in sustainable livestock farming. Additionally, future efforts should prioritize the integration of animal and pasture management practices to fully harness the potential of PLF in mitigating climate impacts and improving the efficiency of livestock systems.

  PublisherDOI

• 341 Determining the optimum duration of performance testing for daily feed intake, growth rate, and residual feed intake in growing goats using Grow Safe Feeding System.

  Journal of Animal Science · 2025-10-01

  articleOpen accessSenior author

  Abstract The study aimed to determine the optimum duration of performance testing length for daily feed intake, growth rate, and residual feed intake in two breeds of growing goats. Nineteen female goats, 10 Alpine and 9 Spanish, with average initial ages of 360-d and 352-d and IBW of 38.8 ± 2.8 kg and 35.5 ± 3.1 kg, respectively, were randomly assigned within the breed to one of two non-adjacent pens (5 goats/pen), each equipped with GrowSafe feed bunks. Goats received a pelletized total mixed ration twice a day and had an ad libitum access to feed, water, and mineral block throughout the 84-d trial period. In determining the length of days on trial for different phenotypic traits for goats, changes and relative changes of phenotypic residual variances, Pearson and Spearman correlations for ADG, DMI, and RFI of shortened tests 28-, 42-, 56-, 70, and the full-test 84-d were determined. The relative residual variance for DMI was 0.0399 at 28-d; it increased, over the increasing test length, to 0.0463, 0.0613, and 0.0634 at 42, 56, and 70 d tests, respectively. At the full test (84-d), the relative residual variance dropped to 0.0574. For DMI, the lowest relative residual variance was observed at the 28-d test period, and the Pearson Correlation coefficient for the DMI reached 0.946 (p < 0.0001) at 28-d. Relative residual variance (RRV) for ADG at 28 d test was 0.00437; it decreased over increasing test period to 0.00406 at 42-d, attained a peak value of 0.0050 at 56-d, and dropped to 0.00268 and 0.000237 at 70-d and 84-d, respectively. The lowest variation for ADG was observed at the full-test period of 84-d. In addition, the Pearson correlation coefficient reached its highest (>0.95) (p <.0001) at 84-d and relatively low 0.946 (p < 0.0001) at 56-d. According to the RRV and Pearson r2 results, the 84-d test length was sufficient to measure ADG in Alpine and Spanish goats. For RFI, the relative residual variance at 28 d and 42 d tests was comparable (0.018); slightly decreased over the increasing test period to 0.017 at 56 and increased to 0.031 and 0.030 at 70 and 84 d, respectively. The lowest variation for RFI was at 56 d test length. However, Pearson correlations between shortened tests (28-, 42-, 56-, and 70-day) and the full-length 84-day test for RFI was 0.83 (p< 0.0001) at 56-d, which is lower than the other shortened tests 28-d, 42-d, and 70-d with R of 0.93, 0.90, and 0.96, respectively. Based on both RRV and r2 results, the 56-d test length should be sufficient to measure the RFI in goats accurately. The current results are inconsistent with previous results and their application warrants further research.

  PublisherOA PDFDOI

• 271 Effects of vaccination on enteric methane emissions, growth performance, and feeding behavior of beef cattle.

  Journal of Animal Science · 2025-10-01 · 1 citations

  articleOpen access

  Abstract Rising global temperatures have intensified the urgency to reduce greenhouse gas (GHG) emissions from anthropogenic sources, including agricultural methane (CH4). CH4 is a potent GHG produced as a byproduct of ruminal fermentation in cattle. CH4 warms the atmosphere 28 times more than carbon dioxide (CO₂) over a 100-year period, making it a critical GHG mitigation target. Multiple approaches are being developed, but the beef cattle industry lacks solutions that effectively reach ~80% of bovine CH4 emissions produced in extensive, pasture-based systems, e.g., the cow-calf and stocker segments. One promising approach is a methane-reducing vaccine. Methane-reducing vaccines stimulate the production of anti-methanogen antibodies. These antibodies potentially enter the rumen, bind to their methanogen targets, and inhibit ruminal methanogenesis, thereby reducing enteric CH4 emissions. The objective of this trial was to assess the effect of a proto-type vaccine on growth performances, gas flux, and feeding behavior in beef cattle. Thirty Angus crossbred steers (n = 30; 451 ± 11 kg) were blocked by body weight (BW) and stratified by breed before being randomly assigned to one of two treatments: control (n = 20) or vaccine-treated (n = 10). Animals received a prime-boost vaccine regimen (2 mL, each) administered subcutaneously on days 0 and 21. Animals were housed in three pens, each equipped with three electronic feed bunks (Vytelle, Lenexa, KS) for recording individual feed intake and feeding behavior, as well as one GreenFeed emission monitoring system (C-lock Inc., Rapid City, SD) for measuring CH4 emissions. Weekly BW, daily feed intake, and gas emissions were measured over an 84-day period. Statistical analyses were conducted in JMP Pro v.16 (SAS Institute Inc., Cary, NC), with individual animals as the experimental unit, and treatment as a fixed effect. There were no significant differences in average daily gain (ADG), initial BW, mid-test metabolic BW (BW⁰·⁷⁵), DMI, alfalfa pellet intake or gain: feed (P > 0.05). The vaccine-treated group had 15% lower (P = 0.0050) CH4 production (g/d), 18% lower (P = 0.0038), CH4 intensity (g/kg BW 0.75) and 13% lower (P = 0.0149) CH4 yield emissions (g/kg DMI) compared to the control. However, CO2 production (g/d), CO2 yield (g/kg DMI) and H2 production (g/d) did not differ (P > 0.05). Bunk visit (BV) duration was also similar between groups (P > 0.05). However, the vaccine-treated group had fewer BV per day (P = 0.0292) and a longer BV head-down duration per day (P = 0.0105), with a tendency for a slower eating rate (P = 0.0697) compared to control. These results highlight the potential of vaccination as a strategy to mitigate enteric CH4 production in beef cattle without negatively impacting growth performance.

  PublisherOA PDFDOI

• 156 Residual methane production is not significantly related to growth performance, feed efficiency, and carcass traits in finishing beef steers

  Journal of Animal Science · 2025-06-01

  articleOpen access

  Abstract Enteric methane (CH4) represents the largest contributor to the beef industry’s carbon footprint. A residual CH4 production (RMP) trait has been suggested as a selection index to identify cattle with lower emissions. However, the relationship between RMP and animal performance, feed efficiency and carcass traits are largely unknown, specifically within the context of the typical feeding practices of the U.S feedlot industry. Accordingly, the objective of this study was to determine the relationship between RMP and CH4 emission traits, dry matter intake (DMI), growth performance, measures of feed efficiency, and carcass traits. Data from two previously published experiments were compiled. The compiled dataset was composed of beef steers [n = 92; initial body weight (BW) = 520.1 to 525.3 kg and final BW = 660.6 to 680.4 kg] fed finishing diets (net energy for maintenance = 2.18 to 2.23 Mcal per kg DM). Enteric CH4 emissions were estimated using automated head chamber systems (AHCS; GreenFeed, C-Lock Inc., Rapid City, SD) and cattle were fed using Calan head gates (American Calan, Northwood, NH) to determine individual DMI in both experiments. The RMP index was determined by regressing CH4 emissions against DMI and metabolic BW. The RMP of each animal was then determined as that animal’s difference between observed and predicted values. The relationship between RMP and traits of interest were assessed using the Pearson’s correlation coefficients between study-adjusted values. Residual CH4 production was not related (P ≥ 0.72) to DMI, average daily gain (ADG), gain-to-feed ratio (G:F), residual average daily gain (RADG), or residual feed intake (RFI). However, RMP was positively (P < 0.01) correlated with CH4 emissions (g/d; r = 0.94), CH4 yield (MY; g CH4/kg DMI; r = 0.79), and emission intensity (EI; g CH4/kg ADG; r = 0.70). Finally, RMP was not (P ≥ 0.28) associated with hot carcass weight, dressing percentage, rib eye area, back fat thickness, yield grade, marbling score, or calculated empty body fat. The results of this investigation suggest that low RMP cattle have lower daily CH4 emissions, MY, and EI, without sacrificing growth performance, feed efficiency, or carcass traits. Future research should establish the heritability for this trait to determine if RMP can be selected through breeding.

  PublisherOA PDFDOI

• Smart Technologies for Sustainable Pasture-Based Ruminant Systems: A Review

  SSRN Electronic Journal · 2024-01-01

  reviewOpen access
  PublisherDOI

• PSV-10 Vaccination of beef cattle to reduce enteric methane emissions

  Journal of Animal Science · 2024-09-01

  articleOpen access

  Abstract Livestock methane (CH4) emissions total over 3 billion tonnes per year of carbon dioxide equivalents (CO2e) and are responsible for approximately 6% of total annual greenhouse gas emissions. The contribution of livestock CH4 emissions are only to be exacerbated as the global demand for meat and dairy products increases. Greater than 75% of livestock CH4 emissions are generated in dispersed production environments (e.g., cow-calf and stocker segments), which are not addressable by methane mitigation strategies requiring constant inputs. Thus, strategies that fit into standard agronomic practices, in particular dispersed production environments, are urgently needed to address the increasing carbon footprint associated with livestock production. Methane-reducing vaccines are a promising solution for addressing this need, due to their longevity of action, low cost, and ease of integration into standard agronomic practices, which could lower the barrier for adoption. Thus, this study aimed to assess the effects of a prototype vaccine on total and antigen-specific immune response, CH4 yield, and average daily gain (ADG) in cattle. Angus crossbred steers [n = 20; initial body weight (BW) = 537 ± 15 kg) fed on a high-forage diet were randomly assigned to either placebo- or vaccine-treated groups blocked by BW, breed, and feed intake. Steers were subcutaneously inoculated (2 mL dose) in the anterior region of the neck. Blood and saliva samples were collected, and total sera and salivary immunoglobulin (Ig) G and IgA were quantified using ELISA (Bethyl laboratories, Montgomery, TX). Antigen-specific sera IgG was measured using ELISA. Daily CH4 emissions and dry matter intake (DMI) were measured using GreenFeed systems (C-Lock Inc. Rapid City, SD) and GrowSafe feed bunks (Vytelle, Lenexa, KS), respectively. Body weights were recorded bi-weekly. Total sera IgA and IgG did not differ between the placebo-treated and vaccinated steers (P = 0.584 and P = 0.425, respectively), nor did total salivary IgA and IgG (P = 0.577 and P = 0.548, respectively). However, antigen-specific sera IgG did significantly increase following booster vaccination in the vaccinated steers, as compared with placebo-treated steers (d 0 vs. d 28; P < 0.001). CH4 yield was significantly reduced in vaccinated steers following booster vaccination despite significantly increasing in placebo-treated steers over the same period (P = 0.002). This reduction in CH4 yield was not associated with a reduction in DMI nor ADG (P = 0.181 and P = 0.314, respectively), suggesting that vaccination did not negatively affect treated animals. These findings underscore the potential of vaccine-based solutions to mitigate the environmental impact of livestock CH4 emissions, especially from dispersed production environments where current options for mitigation strategies are limited.

  PublisherOA PDFDOI

• Association of genomically enhanced residual feed intake with performance, feed efficiency, feeding behavior, gas flux, and nutrient digestibility in growing Holstein heifers

  Journal of Animal Science · 2024-01-01 · 1 citations

  articleOpen access

  Residual feed intake (RFI), a metric of feed efficiency, is moderately heritable and independent of body size and productivity, making it an ideal trait for investigation as a selection criterion to improve the feed efficiency of growing cattle. The objective of this study was to examine the differences in performance, feed efficiency, feeding behavior, gas flux, and nutrient digestibility in Holstein heifers with divergent genomically enhanced breeding values for RFI (RFIg). Holstein heifers (n = 55; BW = 352 ± 64 kg) with low (n = 29) or high (n = 26) RFIg were selected from a contemporary group of 453 commercial Holstein heifers. Heifers were rotated between 1 of 2 pens, each equipped with 4 electronic feed bunks and 1 pen with a GreenFeed emissions monitoring (GEM) system. Individual dry matter intake (DMI) and feeding behavior data were collected for 84-d. Body weight (BW) was measured weekly and spot fecal samples were collected at weighing. Phenotypic RFI (RFIp) was calculated as the residual from the regression of DMI on average daily gain (ADG) and mid-test metabolic BW (BW0.75). A mixed model including the fixed effect of RFIg classification and the random effect of group was used to evaluate the effect of RFIg classification on response variables. There were no differences (P > 0.05) in BW and ADG for heifers with divergent RFIg; however, low RFIg heifers consumed 7.5% less (P < 0.05) feed per day. Consequently, low RFIg heifers exhibited a more favorable (P < 0.05) RFIp compared to high RFIg heifers (-0.196 vs 0.222 kg/d, respectively). Low RFIg heifers had 8.7% fewer (P < 0.05) bunk visit events per day and tended to have an 11.2% slower (P < 0.10) eating rate. Low RFIg heifers had 7.7% lower (P < 0.05) methane (CH4) emissions (g/d), 6.1% lower (P ≤ 0.05) carbon dioxide (CO2) production (g/d), and 5.6% lower (P ≤ 0.05) heat production (Mcal/d) than high RFIg heifers. However, CH4 yield and CO2 yield (g/kg DMI), and heat production per unit DMI (Mcal/kg DMI) did not differ (P > 0.05) between heifers with divergent RFIg. Dry matter (DM) and nutrient digestibility did not differ (P > 0.05) between heifers with divergent RFIg. Results suggest that selection based on RFIg provides opportunities to select cattle with favorable feed efficiency phenotypes to increase the economic and environmental sustainability of the cattle industry.

  PublisherOA PDFDOI

• PSV-30 Effects of divergent residual feed intake on performance, feed efficiency, feeding behavior and gaseous exchange in replacement beef heifers

  Journal of Animal Science · 2024-09-01

  articleOpen access

  Abstract The objective of this study was to examine the differences in performance, feed efficiency, feeding behavior and gaseous exchange (methane, carbon dioxide and oxygen) in replacement beef heifers with divergent phenotypes for residual feed intake (RFI). Crossbred beef replacement heifers [n = 63; initial body weight (BW) = 277 ± 21 kg] were blocked by BW and assigned to 1 of 2 pens each equipped with electronic feed bunks (GrowSafe Systems) and GreenFeed gaseous-exchange measurement systems (GEM; C-Lock). Heifers were fed a corn-silage based ration twice daily. Individual dry matter intake (DMI), feeding behavior, and gas flux data were collected for 70 d and BW measured weekly. Carcass ultrasound data were collected at the beginning and end of the study. Residual feed intake was calculated as the residual from the regression of DMI on ADG and mid-test BW0.75 and heifers assigned to low-, medium-, and high-RFI classes (± 0.5 SD from the mean RFI). A mixed model with RFI class as fixed effect and pen as a random effect was used for data analysis. There were no differences due to RFI class in BW and ADG. However, low-RFI heifers consumed 16% less (P &amp;lt; 0.001) DMI and had more favorable gain to feed (G:F) then high-RFI heifers. High-RFI heifers had a greater (P &amp;lt; 0.05) backfat gain during the 70-d study, with backfat gain accounting for an additional 4.2% of the variation in DMI. Low-RFI heifers exhibited more favorable feeding behavior, with 10.4% fewer (P = 0.057) bunk visit events and spent numerically less time at the feed bunk (103 vs 122 min/d) compared with high-RFI heifers. Methane emissions (g/d) did not differ between heifers with divergent RFI (P = 0.138; 129 vs 140 g/d in low- and high RFI heifers respectively), however, methane yield (g/kg DMI) was 9% greater (P &amp;lt; 0.05) in low- compared with high-RFI heifers. Additionally, low-RFI heifers produced 7.9% less (P &amp;lt; 0.05) carbon dioxide (g/d) and consumed 6.9% less (P &amp;lt; 0.05) oxygen than high RFI heifers. Further research is warranted to investigate the biological mechanisms influencing RFI and the effects of selection for RFI as a strategy to mitigate reduce greenhouse gas emissions from cattle production systems.

  PublisherOA PDFDOI

• 191 Awardee Talk: Characterizing biological processes influencing the efficiency of nutrient utilization in growing cattle

  Journal of Animal Science · 2024-09-01

  articleOpen accessSenior author

  Abstract 2Abstract: Residual feed intake (RFI), a metric of feed efficiency, is moderately heritable and minimally associated with body size and productivity, making it an ideal trait for investigation as a selection criterion to improve feed efficiency of growing cattle. The objective of this research was to characterize the inter-animal variation in biological processes of growing cattle selected to be divergent in RFI. Holstein heifers [n = 55; body weight (BW) = 351 ± 64 kg) with low- (n = 29) or high- (n = 26) genomically enhanced RFI (RFIg) were selected from a contemporary group of 453 heifers. Heifers were assigned to 1 of 2 pens, equipped with electronic feed bunks and a GreenFeed gaseous-exchange measurement system. Individual dry matter intake (DMI) and feeding behavior data were collected for 84-d. Body weight was measured weekly, and spot fecal samples collected at weighing. Phenotypic RFI (RFIp) was calculated as the residual from regression of DMI on ADG and mid-test BW0.75. On d 70 of the study a rumen fluid sample was collected via esophageal tubing. Blood samples were collected and analyzed for complete blood count (CBC). A mixed model including the fixed effect of RFIg classification and random effect of pen was used to evaluate the effect of RFIg classification on response variables. There were no differences (P &amp;gt; 0.05) in BW and ADG for heifers with divergent RFIg; however, low RFIg heifers consumed 7.5% less (P &amp;lt; 0.05) feed per day. Consequently, low RFIg heifers exhibited a more favorable (P &amp;lt; 0.05) RFIp (-0.188 vs 0.211 kg/d, respectively). Low RFIg heifers exhibited more favorable feeding behavior, with 8.7% fewer (P &amp;lt; 0.05) bunk visit events per day and an 11.2% slower (P ≤ 0.05) eating rate. Low RFIg heifers had 12.5% greater (P &amp;lt; 0.05) total rumen volatile fatty acid concentrations than high RFIg heifers, indicating potentially enhanced microbial fermentation and improved efficiency of feed utilization. Low RFIg heifers had 8.2% less (P &amp;lt; 0.05) methane emissions (g/d), 6.3% less (P &amp;lt; 0.05) carbon dioxide production (g/d), and 6.1% less (P &amp;lt; 0.05) heat production (Mcal/d) calculated according to Brouwer (1965) than high RFIg heifers. Dry matter digestibility did not differ (P &amp;gt; 0.05) between heifers with divergent RFIg. Overall, heifers selected to be more feed efficient exhibited more favorable energy efficiencies and feed efficiency phenotypes. To quantify the variation in RFIg explained by feeding behavior, gas flux, digestibility and rumen fermentation, and CBC partial least squares regression models were developed. Feeding behavior accounted for the largest proportion of variation in RFIg (28.8%). Upon sequential addition of gas flux, digestibility and rumen fermentation, and CBC to feeding behavior, 56.3% of the variation in RFIg was accounted for. Identifying the magnitude at which metabolic processes influence inter-animal variation in efficiency of nutrient utilization provides opportunities to discover valuable candidate biomarkers for selection of more feed efficient cattle.

  PublisherOA PDFDOI

• Development of an algorithm to detect feed bunk replacement events in growing cattle from feeding event data acquired by an electronic feed intake measurement system

  Applied Animal Behaviour Science · 2024-07-08 · 3 citations

  articleOpen accessSenior authorCorresponding

  Visual observations of competitive feeding behavior in cattle have been associated with animal productivity, health, and social hierarchy. However, human visual observations are time consuming, limiting the number of animals that can be evaluated. The objective of this study was to develop and assess an algorithm to detect disruptive feed bunk replacement events using feeding event data acquired from the Vytelle SENSE feed intake measurement system. Crossbred beef steers (N = 20) fed a grower diet were housed in one of two pens each equipped with three electronic feed bunks and a video recorder. A trained video observer recorded all feed bunk replacement events (when an actor animal displaced a reactor animal from the feed bunk and occupied the same feed bunk within a specified time interval, termed as the replacement criterion) and other agonistic activities at the feed bunk during a 4-d period. The Vytelle SENSE feed intake measurement system recorded the start and end timestamps of individual bunk visit (BV) events of animals. An algorithm was developed to determine replacement events based on the start and end times of consecutive BV events. Using video observation as the gold standard, the recall, precision, and F-score of the algorithm was calculated corresponding to time intervals from 1 to 60 s. The optimum replacement criterion was determined to be ≤ 18 s and ≤ 22 s for pens 1 and 2 respectively. The recall, precision, and F-score of the algorithm using these replacement criterions were high (> 0.75). A competition index was computed for each steer, calculated as the number of actor-initiated events divided by the number of actor and reactor events at the feed bunk. Spearman’s rank correlations (rs) between total visually observed agonistic interactions at the feed bunk and the replacement events detected from the electronic feeding event data using the algorithm and replacement criterion of the respective pen was determined. There were strong correlations (rs ≥ 0.71; P < 0.05) between the observed and electronic values for the number of actor and reactor events, and the competition index. These results demonstrate the potential to quantify disruptive feed bunk replacement events in confined beef cattle using electronically collected feeding event data from the Vytelle SENSE feed intake measurement system.

  PublisherDOI

Frequent coauthors

• Keara O’Reilly

  Texas A&M University

  54 shared

• L. O. Tedeschi

  Texas A&M University

  50 shared

• William E. Pinchak

  Texas A&M University

  32 shared

• Robin C. Anderson

  Agricultural Research Service

  32 shared

• Lauren Wottlin

  Agricultural Research Service

  30 shared

• Jocelyn R Johnson

  STgenetics (United States)

  27 shared

• Todd R. Callaway

  University of Georgia

  27 shared

• William C Kayser

  Elanco (United States)

  26 shared

Education

• B.S.

  Iowa State University

• M.S.

  Colorado State University

• Ph.D.

  Colorado State University