Impacts of stocking density on development and puberty attainment of replacement beef heifers

Inhibitory Effect of Puerarin on Lipopolysaccharide-triggered Inflammatory Responses of Bovine Kidney Cells

Puerarin (Pue), a flavonoid compound, possesses cytoprotective effects and LPS has been reported to induce renal inflammatory injury in bovine. However, whether Pue inhibits lipopolysaccharide (LPS)-induced inflammatory damage of bovine kidney cells remains unknown. Based on an in vitro model with Madin-Darby bovine kidney (MDBK) cell line, it has found that Pue attenuated LPS-induced damage of MDBK cells, as evidenced by cell viability and lactic dehydrogenase (LDH) release rescued by Pue (P < 0.05). Additionally, the real-time quantitative PCR (qPCR) and enzyme linked immunosorbent assay (ELISA) showed that LPS elevated the levels of pro-inflammatory factors interleukin (IL)-1β, IL-8 and tumor necrosis factor (TNF)-α, which was reversed by pretreatment of Pue (P < 0.05). Besides, Pue reduced the expression of Toll like receptor 4 (TLR4) and phosphorylated nuclear factor kappa B (p-NF-κB) of LPS-exposed MDBK cells (P < 0.05). Collectively, these results showed that Pue suppresses LPS-evoked inflammatory damage of bovine kidney cells, suggesting Pue a potential compound for intervention of bovine inflammation.

Behavioral activity patterns but not hair cortisol concentrations explain steers' transition-related stress in the first 6 wk in the feedlot

Stress during the transition of beef steers from ranch to feedlot may depend on steer source and preconditioning. The interplay between physiological and behavioral patterns of preconditioned (PC) and auction-derived (AD) steers, particularly after commingling, is poorly understood. Our objective was to evaluate whether hair cortisol (HC) concentrations were related to the health and performance of PC and AD steers and study behavioral activities after commingling over 6 wk in a feedlot. Steers, sourced either from ranch (PC, n = 250) or local auction (AD, n = 250), were assigned into 1 of 5 pens, 100% PC (100PC); 75% PC 25% AD (75PC); 50% PC 50% AD (50PC); 25% PC 75% AD (25PC), and 100% AD (0PC), each pen containing 100 steers. Pen was the experimental unit and individual steers were the observational unit where physiological and behavioral changes were measured. The study subsampled 225 steers (PC = 113 and AD = 112) which were equipped with CowManager ear tags to record behaviors. On day 40, hair samples from each steer were collected by clipping hair close to the skin. Data were analyzed using multiple linear, logistic regression, or multilevel negative binomial regression models depending on the outcomes. There was no difference in HC concentrations (day 40) between PC and AD steers (P = 0.66), and no association with Bovine Respiratory Disease (BRD)-related morbidity (P = 0.08) or average daily gain (ADG) (P = 0.44). After adjusting for source and commingling effects, HC concentrations did not affect time spent eating (P = 0.83), ruminating (P = 0.20), active (P = 0.89), or non-active (P = 0.32). PC steers spent more time eating and ruminating over weeks 1 to 4 (P < 0.01) and weeks 1 to 3, respectively (P < 0.05), and more time being active over weeks 1 and 2 compared to AD steers (P < 0.001), but less time being non-active than AD steers on weeks 1 to 3 (P < 0.001). Steers in 100PC and 50PC pens spent more time eating than steers in 0PC (P < 0.001), whereas steers in 25PC spent less time eating than steers in 0PC (P < 0.001). Steers in 0PC spent the most time being not active (P < 0.01). In conclusion, preconditioned steers spent more time eating, ruminating, and being active and less time being not active over the first 3 wk in the feedlot, regardless of commingling. The HC concentrations did not identify potentially lower stress related to ranch transfer and were neither associated with BRD-related morbidity nor ADG.

Effects of a moderate exercise regimen on development and puberty attainment of beef heifers reared in drylots at a high stocking density

This experiment evaluated growth, physiological responses, and puberty attainment in beef heifers reared in drylots with a high stocking density, and provided or not with a moderate exercise regimen. A total of 180 heifers (75% Angus × 25% Brahman) were used in this experiment replicated over 2 yr. Each year, 90 heifers were ranked by age (264 ± 1 d) and body weight (BW on day -3; 200 ± 2 kg) on day 0, and assigned to a) one of six drylot pens (10 × 14 m pens; 10 heifers per pen) with a stocking density of 14 m2/heifer (DENS), or b) one of three pastures (2-ha pastures; 10 heifers per pasture) with a stocking density of 2,000 m2/heifer (CON). Beginning on day 15, three DENS pens were given access to an exercise area (DENS-EX) 3 times/wk (1 h). Negligible forage was available for CON, whereas heifers from all treatments received the same limit-fed diet (~13 kg/heifer daily). Shrunk BW was recorded after 16 h of feed and water withdrawal on days -3 and 225 to calculate BW gain. Temperament was evaluated on days 0, 128, and 224. Heifers were fitted with a pedometer behind their shoulder on day 0 to record physical activity. Pedometer results and blood samples were collected weekly for progesterone analysis. Hair samples from the tail switch were collected every 28 d. Data were analyzed with pen or pasture as an experimental unit, via ANOVA using the MIXED or GLIMMIX procedures of SAS (SAS Inst. Inc., Cary, NC). Heifers from CON had more (P < 0.01) steps per week compared with DENS and DENS-EX (23,973, 6,706, and 12,354 steps/wk, respectively; SEM = 1,247), and DENS-EX heifers had more (P < 0.01) steps per week compared with DENS. No treatment effects (P ≥ 0.91) were detected for heifer BW gain (~0.820 kg/d). Hair cortisol concentrations were greater (P ≤ 0.05) in DENS and DENS-EX compared with CON beginning on day 56. Exit velocity and temperament score were greater (P ≤ 0.05) in DENS compared with DENS-EX and CON on day 224. Puberty attainment was delayed (treatment × day; P < 0.01) in DENS compared with DENS-EX and CON. A greater (P ≤ 0.05) proportion of CON were pubertal by day 105 compared with DENS and DENS-EX (30.0%, 11.6%, and 15.0%, respectively; SEM = 6.5), while a greater (P < 0.05) proportion of CON and DENS-EX were pubertal by day 154 compared to DENS (61.7%, 66.7%, and 43.3%, respectively; SEM = 6.5). Rearing replacement heifers in drylots with high stocking density has detrimental effects on their puberty attainment, and the moderate exercise regimen partially alleviated this negative outcome.

Hair Cortisol and DHEA-S in Foals and Mares as a Retrospective Picture of Feto-Maternal Relationship under Physiological and Pathological Conditions

Equine fetal hair starts to grow at around 270 days of pregnancy, and hair collected at birth reflects hormones of the last third of pregnancy. The study aimed to evaluate cortisol (CORT) and dehydroepiandrosterone-sulfate (DHEA-S) concentrations and their ratio in the trichological matrix of foals and mares in relation to their clinical parameters; the clinical condition of the neonate (study 1); the housing place at parturition (study 2). In study 1, 107 mare-foal pairs were divided into healthy (group H; n = 56) and sick (group S; n = 51) foals, whereas in study 2, group H was divided into hospital (n = 30) and breeding farm (n = 26) parturition. Steroids from hair were measured using a solid-phase microtiter radioimmunoassay. In study 1, hair CORT concentrations measured in foals did not differ between groups and did not appear to be influenced by clinical parameters. A correlation between foal and mare hair CORT concentrations (p = 0.019; r = 0.312, group H; p = 0.006; r = 0.349, group S) and between CORT and DHEA-S concentrations in foals (p = 0.018; r = 0.282, group H; p < 0.001; r = 0.44, group S) and mares (p = 0.006; r = 0.361, group H; p = 0.027; r = 0.271, group S) exists in both groups. Increased hair DHEA-S concentrations (p = 0.033) and decreased CORT/DHEA-S ratio (p < 0.001) appear to be potential biomarkers of chronic stress in the final third of pregnancy, as well as a potential sign of resilience and allostatic load in sick foals, and deserve further attention in the evaluation of prenatal hypothalamus-pituitary-adrenal (HPA) axis activity in the equine species. In study 2, hormone concentrations in the hair of mares hospitalized for attended parturition did not differ from those that were foaled at the breeding farm. This result could be related to a too brief period of hospitalization to cause significant changes in steroid deposition in the mare’s hair.

Identification of chronic stress biomarkers in dairy cows

Stress in dairy herds can occur from multiple sources. When stress becomes chronic because of a long duration and inability of animals to adapt, it is likely to deeply affect the emotional state, health, immunity, fertility and milk production of cows. While assessing chronic stress in herds would be beneficial, no real consensus has emerged from the literature regarding the indicators of interest. The goal of this study was to compare and evaluate potential biomarkers for chronic stress after inducing stress over a 4-week period through severe overstocking, restricted access to feed and isolated unusual events. A total of 30 cows were involved in the experiment and two similar groups were constituted. Over a 4-week period, the 15 cows of the stress group were housed in overstocked conditions, with 4.6 m² per cow, including resting and feeding areas. In this area, only seven individual places at the feeding area were available for the 15 cows to generate competition for feed access. Twice during the trial and over a period of 2 h, an additional stress was induced by moving cows to an unfamiliar barn and diffusion of stressing noises (dog barking). Meanwhile, the 15 cows of the control group stayed in the original barn, with more than 10 m² per cow and more individual places at the feeding area than cow number. On a weekly basis, several variables considered as potential biomarkers for chronic stress were recorded. Collected data were analysed using single trait linear repeated mixed models. No differences were observed regarding milk yield, BW of cows or body condition score but the milk loss was more pronounced in the stress group. The activity was more heterogeneous and the rumination of cows was lower in the stress group. The heart rate was lower in the stress group and showed more heterogeneity at the end of the stress period. No differences were observed regarding salivary cortisol, blood glucose, β-endorphin, thyroxine and leucocyte profile. A higher level of hair cortisol and blood fructosamine were observed in the stress group at the end of the stress period. Regarding the practical use of the highlighted biomarkers, milk loss may be an effective and easy way to detect general problems, including stress. The blood fructosamine and the hair cortisol concentrations are promising indicators to assess chronic stress in commercial farms.

Risk Factors for Chronic Stress in Sows Housed in Groups, and Associated Risks of Prenatal Stress in Their Offspring

Chronic stress has a detrimental effect on sow welfare and productivity, as well as on the welfare and resilience of their piglets, mediated prenatally. Despite this, the specific risk factors for chronic stress in pregnant sows are understudied. Group-housed pregnant sows continuously face numerous challenges associated with aspects of the physical (group type and size, flooring, feeding system) and social (stocking density, mixing strategy) environment. There are many well-known potent stressors for pigs that likely contribute to chronic, physiological stress, including overcrowding, hot temperatures, feed restriction, inability to forage, uncomfortable floors, and poor handling. Some of these stressors also contribute to the development of production diseases such as lameness, which in turn are also likely causes of chronic stress because of the associated pain and difficulty accessing resources. The aim of this review is to discuss potential risk factors for chronic stress in pregnant sows such as space allowance, group size and type (stable/dynamic), feeding level, lameness, pen design, feed system, enrichment and rooting material, floor type, the quality of stockmanship, environmental conditions, and individual sow factors. The mechanisms of action of both chronic and prenatal stress, as well as the effects of the latter on offspring are also discussed. Gaps in existing research and recommendations for future work are outlined.

Supplementing a blend of magnesium oxide to feedlot cattle: effects on ruminal, physiological, and productive responses

This experiment evaluated ruminal, physiological, and productive responses of feedlot cattle consuming a corn-based finishing diet that included different levels of a magnesium oxide (MG) blend. Yearling cattle (58 heifers and 62 steers) were ranked by sex and initial body weight (BW; 407 ± 3.1 kg), and allocated to 4 groups of 30 animals each. Groups were housed in one of four drylot pens (30 × 12 m) equipped with GrowSafe automated feeding systems (Model 6000E, 4 bunks/pen) during the experiment (days -14 to 117). On day 0, groups were randomly assigned to receive a total-mixed ration without (CON; n = 30) or with the inclusion (as-fed basis) of MG at 0.25% (MG25; n = 30), 0.50% (MG50; n = 30), or 0.75% (MG75; n = 30) until slaughter on day 118. Individual feed intake was recorded daily, and BW was recorded every 14 d and prior to slaughter (day 117). Blood samples were collected on days 0, 28, 56, 84, and 112, and hair samples were collected on days 0, 56, and 112 from the tail-switch. On day 42, eight rumen-cannulated steers (BW = 492 ± 8.0 kg) were housed with yearling cattle (1 pair/pen). Pairs rotated among groups every 14 d, resulting in a replicated 4 × 4 Latin square design (n = 8/treatment; days 42 to 98). Rumen pH was measured on days 7 and 14 of each period (0800, 1200, 1600, and 2000 h). Orthogonal contrasts were used to determine if inclusion of MG (0%, 0.25%, 0.50%, or 0.75% of the diet) yielded linear or quadratic effects, and to explore overall effect of MG supplementation (CON vs. MG25 + MG50 + MG75). No treatment differences were noted (P ≥ 0.31) for BW gain, feed intake, or feed efficiency. Cattle supplemented with MG tended to have less carcass marbling (P = 0.07) compared with CON. Inclusion of MG linearly increased (P < 0.01) mean plasma concentrations of magnesium and tended to linearly decrease (P = 0.09) mean plasma concentrations of haptoglobin. Cattle supplemented with MG had greater (P < 0.01) mean plasma concentrations of cortisol compared with CON. Hair cortisol concentration did not differ between treatments on day 56 (P ≥ 0.25) and linearly decreased (P < 0.01) with MG inclusion on day 112 (treatment × day; P = 0.02). Inclusion of MG linearly increased (P = 0.03) mean rumen pH, but these outcomes were mostly noted during the last two sampling of the day (treatment × hour; P = 0.02). Collectively, supplemental MG was effective in controlling rumen pH in cattle receiving a corn-based finishing diet, but without improvements in feedlot performance and carcass merit.

Effects of Temperament on the Reproduction of Beef Cattle

Simple Summary

In beef cattle and other livestock species, temperament can be considered as their behavioral responses to human interaction. Temperament evaluation allows classifying cattle according to the level of responsiveness, from calm to excitable. Consistently across studies, beef females classified as more excitable have signs of increased stress response and are less fertile compared to cohorts with calmer temperament. Cattle temperament can be improved via genetic selection and acclimating young animals to human interaction and handling procedures.

Abstract

Temperament is often defined as the behavioral expression of animals in response to human interaction. Cattle temperament can be evaluated using an association of chute score and exit velocity, with cattle then classified as adequate or excitable temperament. To assess the impacts of temperament on various beef systems, these evaluation criteria were associated with productive and reproductive parameters of Bos taurus and B. indicus-influenced cattle. Consistently across studies, excitable cattle had greater plasma cortisol compared to animals with adequate temperament. Studies also reported that excitable beef females have poorer reproductive performance compared to calmer cohorts, including reduced annual pregnancy rates, decreased calving rate, weaning rate, and kg of calf weaned/cow exposed to breeding. Acclimating B. indicus × B. taurus or B. taurus heifers to human handling improved behavioral expression of temperament and hastened puberty attainment. However, similar benefits were not observed when mature cows were acclimated to human handling. Collectively, temperament of beef females measured via behavioral responses upon human handling impacts their reproductive and productive responses independent of breed type, and should be considered for optimal beef cattle production.

Welfare assessment in dairy cows using hair cortisol as a part of monitoring protocols

Welfare of dairy cows can be assessed using welfare assessment protocols consisting of resource, management and animal-based measures. Welfare Quality® Assessment Protocol is one of the best-known protocols, which depends almost entirely on animal-based measures. To gain more objective and rapid welfare assessment, new techniques have been developed to measure welfare of animals, such as hair cortisol concentration. As cortisol is released in response to stress, it has long been used as a biomarker of stress in animals. While the precise mechanism of cortisol incorporation into hair is unknown, hair cortisol concentration seems to be a marker of long-term systemic cortisol concentration. Hair cortisol is, therefore, a potential marker of chronic stress and is not likely to be affected by acute stress. Studies on cattle show connections between hair cortisol concentration and factors such as pregnancy, parity, diseases, ectoparasites, body condition score, environmental changes, stocking density and milk yield. Hair cortisol concentration appears to be affected by time of sampling, cow age and breed, UV radiation, season, body region of sampled hair and hair colour. Its concentration also depends on sampling and analytical methods. Hair cortisol is a promising non-invasive tool to evaluate welfare of dairy cows, however, more research is needed to determine the extent of effects on its concentration and the appropriate method of sampling and analysis. Correlations between Welfare Quality® Assessment Protocol scores and pooled hair cortisol concentrations have not yet been found, and more research is needed with larger sample size, a standardized protocol of hair sampling, processing and analysis. With proper attention to detail, hair cortisol levels in pooled hair samples might come to be used as a reliable indicator of dairy animal welfare.

Supplementing organic-complexed or inorganic Co, Cu, Mn, and Zn to beef cows during gestation: postweaning responses of offspring reared as replacement heifers or feeder cattle

One hundred and ninety nonlactating, pregnant beef cows (¾ Bos taurus and ¼ Bos indicus; 138 multiparous and 52 primiparous) were assigned to this experiment at 117 ± 2.2 d of gestation (day 0). Cows were ranked by parity, pregnancy type (artificial insemination = 102, natural service = 88), body weight (BW) and body condition score, and assigned to receive a supplement containing: (1) sulfate sources of Cu, Co, Mn, and Zn (INR; n = 95) or (2) an organic complexed source of Cu, Mn, Co, and Zn (AAC; Availa4; Zinpro Corporation, Eden Prairie, MN; n = 95). The INR and AAC provided the same daily amount of Cu, Co, Mn, and Zn, based on 7 g of the AAC source. From day 0 to calving, cows were maintained in a single pasture and segregated 3 times weekly into 1 of 24 individual feeding pens to receive treatments. Calves were weaned on day 367 (200 ± 2 d of age), managed as a single group for a 45-d preconditioning period (days 367 to 412), and transferred to a single oat (Avena sativa L.) pasture on day 412. Heifer calves were moved to an adjacent oat pasture on day 437, where they remained until day 620. Heifer puberty status was verified weekly (days 437 to 619) based on plasma progesterone concentrations. Steer calves were shipped to a commercial feedlot on day 493, where they were managed as a single group until slaughter (day 724). Plasma cortisol concentration was greater (P = 0.05) in AAC calves at weaning but tended to be less (P = 0.10) on day 370 compared with INR calves. Mean plasma haptoglobin concentration was greater (P = 0.03) in INR vs. AAC calves during preconditioning, and no treatment effects were noted (P = 0.76) for preconditioning average daily gain (ADG). Puberty attainment was hastened in AAC heifers during the experiment (treatment × day; P < 0.01), despite similar (P = 0.39) ADG between treatments from days 412 to 620. Expression of myogenin mRNA in the longissimus muscle was greater (P = 0.05) in INR vs. AAC heifers on day 584. No treatment effects were detected (P ≥ 0.24) for steer ADG from day 412 until slaughter, nor for carcass quality traits. Hepatic mRNA expression of metallothionein 1A was greater (P = 0.02) in INR vs. AAC steers on day 586. In summary, supplementing Co, Cu, Zn, and Mn as organic complexed instead of sulfate sources to beef cows during the last 5 mo of gestation did not improve performance and physiological responses of the steer progeny until slaughter, but hastened puberty attainment in the female progeny reared as replacement heifers.

Performance, health, and physiological responses of newly received feedlot cattle supplemented with pre- and probiotic ingredients

Nutritional strategies that optimize immunity of feedlot cattle are warranted due to increasing regulations with the use of feed-grade antimicrobials. This study evaluated physiological, health, and performance responses of cattle receiving a synbiotic supplement (yeast-derived prebiotic + Bacillus subtilis probiotic), which replaced feed-grade antimicrobials or were fed in conjunction with monensin during the initial 45 days in the feedlot. Angus-influenced steers (n = 256) were acquired from an auction facility on day -2, and transported (800 km) to the feedlot. Shrunk BW was recorded upon arrival (day -1). Steers were allocated to 1 of 18 pens (day 0), and pens were assigned to receive (n = 6/treatment) a free-choice diet containing: (1) monensin and tylosin (RT; 360 mg/steer daily from Rumensin and 90 mg/steer daily from Tylan; Elanco Animal Health, Greenfield, IN, USA), (2) yeast-derived ingredient and B. subtilis probiotic (CC; 18 g/steer daily of Celmanax and 28 g/steer daily of Certillus; Church and Dwight Co., Inc., Princeton, NJ, USA), or (3) monensin in addition to yeast-derived and B. subtilis ingredients (RCC) as in RT and CC. Steers were assessed for bovine respiratory disease (BRD) and DMI daily. Steer BW was recorded on days 45 and 46, and averaged for final BW. Blood samples were collected on days 0, 7, 17, 31, and 45. Feed intake was greater (P ≤ 0.05) in CC vs. RCC and RT during the initial 3 weeks upon feedlot arrival. No treatment differences were noted (P ≥ 0.41) for average daily gain, BW, and feed efficiency. Incidence of BRD did not differ (P = 0.77) between treatments (average 80.1%). A greater proportion (P ≤ 0.03) of RT steers diagnosed with BRD required a second antimicrobial treatment compared with CC and RCC (57.3, 37.3, and 38.6%, respectively). Removal of steers from the trial due to severe morbidity + mortality was greater (P = 0.02) in RT vs. CC (22.4 and 7.0%), and did not differ (P ≥ 0.16) among RCC (12.9%) vs. RT and CC. Plasma glucose concentrations were greater (P ≤ 0.02) in CC vs. RCC and RT on day 7. Plasma concentrations of nonesterified fatty acids were greater (P ≤ 0.02) in RT and RCC vs. CC on day 7, and in RT vs. CC on day 17. Steers receiving the synbiotic supplement had improved response to BRD treatment, suggesting heightened immunocompetence from partially enhanced metabolism and the nutraceutical effects of B. subtilis and yeast compounds.

Supplementing Yucca schidigera extract to mitigate frothy bloat in beef cattle receiving a high-concentrate diet

This experiment compared incidence of frothy bloat, as well as ruminal, physiological, and performance responses of beef heifers receiving a bloat-provoking diet and supplemented with Yucca schidigera extract. Sixteen ruminally cannulated Angus-influenced heifers were ranked by body weight (BW) and assigned to 4 groups of 4 heifers each. Groups were enrolled in a replicated 4 × 4 Latin square design containing 4 periods of 28 d, and a 21-d washout interval between periods. Groups were assigned to receive no Y. schidigera extract (CON), or Y. schidigera extract at (as-fed basis) 1 g/heifer daily (YS1), 2 g/heifer daily (YS2), or 4 g/heifer daily (YS4). During each period, heifers (n = 16/treatment) were housed in individual pens, and fed a sorghum (Sorghum bicolor L.)-based bloat-provocative diet at 2% of their BW. Diet and treatments were individually fed to heifers, twice daily in equal proportions (0700 and 1600 hours). Heifers were assessed for bloat score (0 to 5 scale, increasing according to bloat severity) 3 hr after the morning feeding. Blood samples were collected on days 0, 7, 14, 21, and 28 prior to (0 hr) and at 3, 6, and 9 hr relative to the morning feeding. Rumen fluid samples were collected at the same time points on days 0 and 28. Orthogonal contrasts were tested to determine whether inclusion of Y. schidigera extract (0, 1, 2, or 4 g/heifer daily) yielded linear or quadratic effects, and explore an overall effect of Y. schidigera extract supplementation (CON vs. YS1 + YS2 + YS4). Rumen fluid viscosity was impacted quadratically by Y. schidigera extract inclusion (P = 0.02), being greatest in YS1, followed by YS2, and equivalent between CON and YS4 heifers. Heifers receiving Y. schidigera extract had greater (P ≤ 0.05) rumen propionate, iso-valerate, and valerate concentrations, as well as less (P < 0.01) acetate : propionate ratio compared with CON heifers. Inclusion of Y. schidigera extract linearly increased (P ≤ 0.04) average daily gain and feed efficiency. No other treatment effects were noted (P ≥ 0.19) including bloat score (1.07 ± 0.03 across treatments), ruminal protozoa count, plasma concentrations of cortisol, haptoglobin, urea N, total protein, and rumen concentration of total volatile fatty acids. Supplementing Y. schidigera extract up to 4 g/d favored rumen propionate concentrations and linearly increased growth and feed efficiency but failed to mitigate incidence of frothy bloat in beef heifers consuming a grain-based bloat-provocative diet.

Administering an appeasing substance to optimize performance and health responses in feedlot receiving cattle

This experiment evaluated the impacts of administering a bovine appeasing substance (BAS) at feedlot entry to receiving cattle. Angus-influenced steers (n = 342) from 16 sources were purchased from an auction yard on day -1, and transported (12 hr; 4 trucks) to the feedlot. Upon arrival on day 0, shrunk body weight (BW; 240 ± 1 kg) was recorded and steers were ranked by load, shrunk BW, and source and assigned to receive BAS (IRSEA Group, Quartier Salignan, France; n = 171) or placebo (diethylene glycol monoethyl ether; CON; n = 171). The BAS is a mixture of fatty acids that replicate the composition of the bovine appeasing pheromone. Treatments (5 mL) were topically applied to each individual steer on their nuchal skin area. Steers were allocated to 1 of 24 drylot pens (12 pens/treatment) and received a free-choice diet until day 46. Steers were assessed daily for bovine respiratory disease (BRD) signs, and feed intake was recorded from each pen daily. Steer unshrunk BW was recorded on days 7, 17, 31, 45, and 46. Shrunk BW on day 0 was added an 8% shrink to represent initial BW, and final BW was calculated by averaging BW from days 45 and 46. Blood samples were collected from 5 steers/pen on days 0, 7, 11, 31, and 45. Pen was considered the experimental unit. Steer BW gain was greater (P = 0.04) in BAS vs. CON (1.01 vs. 0.86 kg/d, SEM = 0.05). Feed intake did not differ (P = 0.95) between treatments, resulting in greater (P = 0.05) feed efficiency in BAS vs. CON (171 vs. 142 g/kg, SEM = 10). Plasma cortisol concentration was greater (P = 0.05) and plasma glucose concentration was less in CON vs. BAS on day 7 (treatment × day; P = 0.07 and <0.01, respectively). Mean plasma β-hydroxybutyrate concentration was greater (P < 0.01) in BAS vs. CON (3.23 and 2.75 mg/mL; SEM = 0.12). Incidence of BRD was greater (P ≤ 0.05) in BAS vs. CON from days 6 to 10 and days 19 to 23 (treatment × day; P < 0.01), although overall BRD incidence did not differ (P = 0.20) between treatments (82.4% vs. 76.6%, respectively; SEM = 3.2). A greater proportion (P = 0.04) of BAS steers diagnosed with BRD required one antimicrobial treatment to regain health compared with CON (59.3% vs. 47.6%, SEM = 4.2). Hence, BAS administration to steers upon feedlot arrival improved BW gain during a 45-d receiving period by enhancing feed efficiency. Moreover, results suggest that BAS improved steer performance by facilitating early detection of BRD signs, lessening the disease recurrence upon first antimicrobial treatment.

Impacts of commingling cattle from different sources on their physiological, health, and performance responses during feedlot receiving

This experiment compared physiological, health, and performance responses of beef heifers assigned to different commingling schemes (one, two, or four sources per pen) during a 56-d feedlot receiving period. Ninety-six recently weaned Angus-influenced heifers were obtained from an auction facility. Heifers originated from four cow-calf ranches, and were reared in the same herd within each ranch since birth. Heifers were loaded into two livestock trailers at the auction yard (two sources per trailer; d -2), arranged in two sections of each trailer according to source, and transported for 10 h to stimulate the stress of a long-haul. Heifers were not mixed with cohorts from other sources prior to and at the auction yard. Upon arrival (d -2), shrunk body weight (BW) was recorded and heifers were maintained in four paddocks by source with ad libitum access to a complete starter feed and water for 36 h. On d 0, heifers were ranked by source and shrunk BW and allocated to 1 of 24 drylot pens (four heifers per pen) containing: 1) heifers from a single source (1SRC, n = 8), 2) heifers from two sources (2SRC, n = 8), or 3) heifers from four sources (4SRC, n = 8). From d 0 to d 55, heifers had free-choice access to the complete starter feed and water. Heifers were assessed daily for symptoms of bovine respiratory disease (BRD), and feed intake was recorded from each pen daily. Blood samples were collected on d 0, d 6, d 13, d 27, d 41, and d 55, and shrunk BW (after 16 h of water and feed withdrawal) was recorded on d 56 for average daily gain (ADG). No treatment differences were noted (P ≥ 0.56) for heifer ADG (mean ± SE = 0.853 ± 0.043 kg/d), final shrunk BW, feed intake, and feed efficiency. No treatment differences were noted (P ≥ 0.27) for plasma concentrations of cortisol and haptoglobin, and serum concentrations of antibodies against BRD viruses and Mannheimia haemolytica. No treatment differences were noted (P ≥ 0.17) for incidence of BRD (mean ± SE = 59.3 ± 5.0%) or mortality. The proportion of heifers diagnosed with BRD that required three antimicrobial treatments to regain health increased linearly (P = 0.03) according to the number of sources (0.0, 12.3, and 20.8% of 1SRC, 2SRC, and 4SRC heifers, respectively; SEM = 7.0). Hence, commingling heifers from different sources did not impact performance, physiological responses, and BRD incidence during a 56-d receiving period, although recurrence of BRD after the second antimicrobial treatment increased according to commingling level.

Administering an appeasing substance to beef calves at weaning to optimize productive and health responses during a 42-d preconditioning program

This experiment evaluated the impacts of administering a bovine appeasing substance (BAS) to beef calves at weaning on their performance, physiological responses, and behavior during a 42-d preconditioning program. Eighty calves (40 heifers and 40 steers; 90% British × 10% Nellore) were weaned at 233 ± 2 d of age (day 0); ranked by sex, weaning age, and body weight (BW); and assigned to receive BAS (IRSEA Group, Quartier Salignan, France; n = 40) or placebo (diethylene glycol monoethyl ether; CON; n = 40). Treatments (5 mL) were topically applied to the nuchal skin area of each animal following dam separation. Within treatment, calves were allocated to one of eight drylot pens (four pens per treatment; pen being the experimental unit) and received a free-choice total mixed ration (TMR) from day 0 to 42, intake of which was assessed daily. Live behavior observations were conducted on days 1, 2, 4, 8, 16, and 32. Temperament was assessed and blood samples were collected via jugular venipuncture on days -21, 0, 3, 7, 14, 28, and 42. Hair samples were collected from the tail switch on days 0, 14, 28, and 42. Calves were vaccinated against bovine respiratory disease viruses on days -21 and 0. Average daily gain from day 0 to 42 did not differ between treatments (P = 0.57) but was greater (P = 0.05) in BAS vs. CON calves from day 0 to 28. Intake of TMR was greater (P = 0.05) during the first week for BAS vs. CON calves (treatment × week; P = 0.08). The mean proportion of calves feeding simultaneously and performance of social and play behaviors were greater (P ≤ 0.05) for BAS vs. CON calves. Escape attempts were greater (P < 0.01) for BAS vs. CON calves on day 1 (treatment × day; P = 0.03). Exit velocity was greater (P = 0.04) for CON vs. BAS calves on day 14 and tended (P = 0.10) to be greater for CON vs. BAS calves on day 7 (treatment × day; P = 0.03). Mean plasma concentrations of haptoglobin were greater (P = 0.02) in CON vs. BAS calves. Hair cortisol concentrations were greater (P = 0.05) in CON vs. BAS calves on day 14 (treatment × day; P = 0.03). Mean serum concentrations of antibodies against bovine viral diarrhea virus were greater (P = 0.02) in BAS vs. CON calves. Collectively, BAS administration to beef calves at weaning alleviated stress-induced physiological reactions, improved temperament evaluated via chute exit velocity, enhanced humoral immunity acquired from vaccination, and appeared to have accelerated adaptation to novel management scheme and environment.

Is it getting in the hair? - Cortisol concentrations in native, regrown and segmented hairs of cattle and pigs after repeated ACTH administrations

Adrenocorticotropic hormone (ACTH) is part of the hypothalamic-pituitary-adrenal axis response to stress and induces the release of cortisol, which is commonly used as an indicator in stress and animal welfare research. In recent years, hair cortisol concentration (HCC) gained increasing importance as a promising retrospective indicator for stress in animals. Thus, the aim of our study was to validate HCC as a potential indicator of increased endogenous cortisol release in cattle and pigs by repeated ACTH administrations followed by cortisol analysis in different hair types. For this purpose, 34 cattle and 38 gilts were treated either with repeated i.m. injections of ACTH or saline every second day over a period of 4 weeks. Saliva samples were taken before and after injections once a week from selected animals to verify the endogenous cortisol response. At the end of the treatment (week 4) and after 8 and 12 weeks, samples of natural and regrown hair were taken from the caudo-dorsal region of the back and analyzed for cortisol concentrations. In addition, natural hair was sampled after 12 weeks and cut into segments prior to analysis. Treatment with ACTH revealed a significant increase in salivary cortisol after application in both species, although this increase was attenuated in pigs compared to cattle. In week 4, HCCs were significantly elevated in natural and regrown hair of ACTH-treated animals. In cattle, HCCs significantly increased after ACTH treatment in natural, regrown and segmental hair compared with control animals, indicating that HCC may be a promising indicator of stress, as cortisol levels in all hair types reflected the preceding period with increased cortisol release. In pigs, there were no differences in HCCs between treatments. This may be caused by the lower systemic cortisol response in pigs, but seasonally reduced hair growth and external cross-contamination of hair by saliva and urine under commercial husbandry conditions may also interfere with the validity of HCC in this species.

Effects of estrous expression and intensity of behavioral estrous symptoms on variables associated with fertility in beef cows treated for fixed-time artificial insemination

This experiment was conducted to evaluate effects of estrous expression and intensity of behavioral estrous expression, assessed by evaluating physical activity, on variables associated with fertility in beef cows. The following treatment regimen was imposed on lactating, multiparous cows (n = 273): 100-μg injection of GnRH and an intravaginal progesterone (P4) releasing device (CIDR) administered on d -10, 25-mg injection of prostaglandin F_2α at CIDR removal on d -3, and another GnRH injection + fixed-time artificial insemination (TAI) 60-66 h following CIDR removal (d 0). Cows were fitted with a pedometer on d -10, and an estrous detection patch on the tail-head on d -3. Cows were classified as not expressing estrus (NOESTR) or expressing estrus with net physical activity greater (HIESTR) or less than the median (LWESTR). Only data from cows responsive to the estrous synchronization treatment regimen were utilized (NOESTR, n = 119; LWESTR, n = 50; HIESTR, n = 50). Diameter of dominant follicles on d 0 and corpus luteum volume on d 7 were greater in HIESTR compared with LWESTR and NOESTR groups (P < 0.01). Plasma P4 concentrations on d 7 and pregnancy rates to TAI were greater in HIESTR and LWESTR than the NOESTR group (P < 0.01). Hence, if there was estrous expression during the period of the GnRH-based TAI treatment regimen, there were greater pregnancy rates to TAI, whereas when there was greater intensity of behavioral estrous symptoms, there were larger dominant follicles and corpora lutea dimensions but not greater pregnancy rates.

Short communication: administering an appeasing substance to Bos indicus-influenced beef cattle at weaning and feedlot entry

The bovine appeasing substance (BAS) is expected to have calming effects in cattle experiencing stressful situations. Therefore, this study investigated the impacts of BAS administration during two of the most stressful events within beef production systems: weaning and feedlot entry. In experiment 1, 186 Bos indicus-influenced calves (73 heifers, 113 bulls) were weaned at 211 ± 1 days of age (day 0). At weaning, calves were ranked by sex and BW, and assigned to receive BAS (Nutricorp, Araras, SP, Brazil; n = 94) or water (CON; n = 92). Treatments (5 ml) were topically applied to the nuchal skin area of each animal. Calf BW was recorded and samples of blood and tail-switch hair were collected on days 0, 15 and 45. Calves that received BAS had greater (P < 0.01) BW gain from day 0 to 15 compared with CON. Overall BW gain (days 0 to 45) and BW on days 15 and 45 were also greater (P ≤ 0.03) in BAS v. CON. Plasma haptoglobin concentration was less (P < 0.01) in BAS v. CON on day 15, whereas cortisol concentrations in plasma and tail-switch hair did not differ between treatments (P ≥ 0.13). In experiment 2, 140 B. indicus-influenced bulls (∼27 months of age) from 2 different pasture-based systems (70 bulls/origin) were transported to a commercial feedlot (≤ 200-km transport; day -1). On day 0, bulls were ranked by source and BW, and assigned to receive BAS (n = 70) or CON (n = 70) and the same sampling procedures as in experiment 1. Bulls receiving BAS had greater (P = 0.04) BW gain from day 0 to 15, but less (P < 0.01) BW gain from day 15 to 45 compared to CON. No other treatment effects were detected (P > 0.14). Therefore, BAS administration to beef calves alleviated the haptoglobin response associated with weaning, and improved calf growth during the subsequent 45 days. Administration of BAS to beef bulls at feedlot entry improved BW gain during the initial 15 days, but these benefits were not sustained throughout the 45-day experiment.

Impacts of postweaning growth rate of replacement beef heifers on their reproductive development and productivity as primiparous cows1

This experiment evaluated the effects of postweaning body weight (BW) gain of replacement beef heifers on their reproductive development and productivity as primiparous cows. Seventy-two Angus × Hereford heifers were ranked on day -6 of experiment (17 d after weaning) by age and BW (218 ± 1.6 d of age and 234 ± 3 kg of BW), and assigned to receive 1 of 3 supplementation programs from days 0 to 182: 1) no supplementation to maintain limited BW gain (LGAIN), 2) supplementation to promote moderate BW gain (MGAIN), or 3) supplementation to promote elevated BW gain (HGAIN). Heifers were maintained in 2 pastures (36 heifers/pasture, 12 heifers/treatment in each pasture) with free-choice alfalfa-grass hay, and supplements were offered individually 6 d per week. Heifer shrunk BW was recorded on days -6 and 183 for average daily gain (ADG) calculation. Blood samples were collected for puberty evaluation via plasma progesterone weekly from days 0 to 182. On day 183, heifers were combined into a single group and received the same nutritional management until the end of the experimental period (day 718). From days 183 to 253, heifers were assigned to a fixed-time artificial insemination program combined with natural service. Average daily gain from days 0 to 182 was greater (P < 0.01) in HGAIN vs. MGAIN and LGAIN (0.78, 0.60, and 0.37 kg/d, respectively; SEM = 0.02), and greater (P < 0.01) in MGAIN vs. LGAIN heifers. Puberty attainment by the beginning of the breeding season was also greater in HGAIN vs. MGAIN and LGAIN (87.5%, 62.5%, and 56.5%, respectively; SEM = 7.1) but similar (P = 0.68) between MGAIN vs. LGAIN heifers. A treatment × day interaction was detected (P < 0.01) for calving rate, as HGAIN heifers calved earlier compared with MGAIN and LGAIN heifers. Ten heifers per treatment were assessed for milk production via weigh-suckle-weigh at 56.8 ± 1.5 d postpartum, followed by milk sample collection 24 h later. No treatment differences were detected (P ≥ 0.16) for milk yield and composition. However, mRNA expression of GLUT1 in milk fat globules was less (P ≤ 0.02) in LGAIN vs. MGAIN and HGAIN heifers, and expression of GLUT8 mRNA was also less (P = 0.04) in LGAIN vs. HGAIN heifers. No treatment differences were detected (P ≥ 0.44) for offspring weaning BW. Collectively, results from this experiment indicate that HGAIN hastened the reproductive development of replacement heifers, without negatively affecting their milk productivity and offspring weaning weight as primiparous cows.

Supplementing an immunomodulatory feed ingredient to improve thermoregulation and performance of finishing beef cattle under heat stress conditions

This experiment compared physiological and productive responses in finishing beef cattle managed under heat stress conditions, and supplemented (SUPP) or not (CON) with an immunomodulatory feed ingredient (Omnigen-AF; Phibro Animal Health, Teaneck, NJ). Crossbred yearling cattle (¾ Bos taurus × ¼ Bos indicus; 64 heifers and 64 steers) were ranked by initial body weight (BW) (440 ± 3 kg) and sex, and allocated to 1 of 16 unshaded drylot pens (8 heifers or steers/pen). Pens within sex were randomly assigned to receive SUPP or CON (n = 8/treatment). Cattle received a total-mixed ration (91% concentrate inclusion and 1.21 Mcal/kg of net energy for gain; dry matter [DM basis]) during the experiment (day 0 to 106). The immunomodulatory feed was offered as a top-dress to SUPP pens (56 g/d per animal; as-fed basis) beginning on day 7. Cattle BW were recorded on day 0, 14, 28, 42, 56, 70, 84, 98, and 106. Feed intake was evaluated from each pen by recording feed offer daily and refusals biweekly. Intravaginal temperature of heifers was recorded hourly from day 1 to 6, 29 to 41, and 85 to 97. Environmental temperature humidity index (THI) was also recorded hourly throughout the experiment, and averaged 79.8 ± 0.6. Concurrently with BW assessment, hair samples from the tail-switch were collected (3 animals/pen) for analysis of hair cortisol concentrations. Blood samples were collected on day 0, 28, 56, 84, and 106 from all animals for plasma extraction. Whole blood was collected on day 0, 56, and 106 (3 animals/pen) for analysis of heat shock protein (HSP) 70 and HSP72 mRNA expression. Cattle were slaughtered on day 107 at a commercial packing facility. Results obtained prior to day 7 served as independent covariate for each respective analysis. Heifers receiving SUPP had less (P ≤ 0.05) vaginal temperature from 1500 to 1900 h across sampling days (treatment × hour, P < 0.01; 39.05 vs. 39.19 °C, respectively; SEM = 0.04), when THI ranged from 85.3 to 90.1. Expression of HSP70 and HSP72 was less (P ≥ 0.03) for SUPP cattle on day 106 (22.6- vs. 51.5-fold effect for HSP70, SEM = 9.7, and 11.0- vs. 32.8-fold effect for HSP72; treatment × day, P ≤ 0.04). No treatment effects were detected (P ≥ 0.22) for performance, carcass traits, plasma concentrations of cortisol and haptoglobin, or hair cortisol concentrations. Results from this study suggest that SUPP ameliorated hyperthermia in finishing cattle exposed to heat stress conditions, but such benefit was not sufficient to improve productive responses.

An Appraisal of Methods for Measuring Welfare of Grazing Ruminants

Although disturbances in body function of animals can be measured to determine whether a state of stress may exist, there is growing interest in finding ways to assess their emotional status as an indicator of good or bad welfare status. Generally it is easier to determine poor states of well-being than positive ones. For grazing ruminants some indicators of well-being include absence of illness, good growth and productivity, and longevity. Motion detectors can provide automated remote monitoring of behavior and it is likely that there will be advances in the interpretation software to increase the utility of this technology for assessing well-being. Cortisol levels in body fluids, feces and pelage are prominent as a marker of poor animal welfare, but like many of the other objective measures that are used, are not wholly reliable at the individual animal level. These other measures include: plasma serotonin, heart rate variation, infra-red thermography, cytokines, salivary alpha amylase, and acute phase proteins. Use of automated facial expression recognition may supplement electrophysiological recording as means to quantify the pain experience of animals. Although the measures described in the literature do not necessarily provide the final answer for determination of welfare in grazing ruminants, they all have some merit and deserve further investigation.

Revisiting Oxidative Stress and the Use of Organic Selenium in Dairy Cow Nutrition

In commercial animals production, productive stress can negatively impact health status and subsequent productive and reproductive performance. A great body of evidence has demonstrated that as a consequence of productive stress, an overproduction of free radicals, disturbance of redox balance/signaling, and oxidative stress were observed. There is a range of antioxidants that can be supplied with animal feed to help build and maintain the antioxidant defense system of the body responsible for prevention of the damaging effects of free radicals and the toxic products of their metabolism. Among feed-derived antioxidants, selenium (Se) was shown to have a special place as an essential part of 25 selenoproteins identified in animals. There is a comprehensive body of research in monogastric species that clearly shows that Se bioavailability within the diet is very much dependent on the form of the element used. Organic Se, in the form of selenomethionine (SeMet), has been reported to be a much more effective Se source when compared with mineral forms such as sodium selenite or selenate. It has been proposed that one of the main advantages of organic Se in pig and poultry nutrition is the non-specific incorporation of SeMet into general body proteins, thus forming an endogenous Se reserve that can be utilized during periods of stress for additional synthesis of selenoproteins. Responses in ruminant species to supplementary Se tend to be much more variable than those reported in monogastric species, and much of this variability may be a consequence of the different fates of Se forms in the rumen following ingestion. It is likely that the reducing conditions found in the rumen are responsible for the markedly lower assimilation of inorganic forms of Se, thus predisposing selenite-fed animals to potential Se inadequacy that may in turn compromise animal health and production. A growing body of evidence demonstrates that organic Se has a number of benefits, particularly in dairy and beef animals; these include improved Se and antioxidant status and better Se transfer via the placenta, colostrum, and milk to the newborn. However, there is a paucity in the data concerning molecular mechanisms of SeMet assimilation, metabolism and selenoprotein synthesis regulation in ruminant animals, and as such, further investigation is required.

Hair Cortisol in Sheltered Cows and Its Association with Other Welfare Indicators

India, the country with the largest population of dairy cows in the world, has a policy of retiring abandoned and non-lactating cows in shelters, but the level of provision for their welfare in these shelters is unclear. Cows in 54 shelters across India were assessed for historic evidence of physiological stress, through determination of hair cortisol in 540 samples from 10 cows in each shelter by enzyme immunoassay. Animal-based and shelter resource-based welfare measures were recorded and correlations with the hair cortisol investigated by multivariable analysis. High hair cortisol concentrations were associated with dung in the lying area of the cowshed, a low dry bulb temperature there and little cow access to yards, as shelter-based variables. At a cow level, high hair cortisol concentrations were associated with dirty flanks, hock joint ulceration, carpal joint injuries, body lesions, dehydration, an empty rumen, old age, and low levels of body hair loss. Hair cortisol level promises to be an effective biomarker of stress in cows when conducting studies under field conditions.

The use of hair cortisol for the assessment of stress in animals

The hair cortisol concentration (HCC) is assumed to be a retrospective marker of integrated cortisol secretion and stress over longer periods of time. Its quantification is increasingly used in psychoneuroendocrinological studies in humans, but also in animal stress and welfare research. The measurement of HCCs for the assessment of stress offers many considerable benefits for use in domesticated and wild animals, especially due to the easy and minimally invasive sampling procedure and the representation of longer time periods in one sample. This review aims to outline the different fields of application and to assess the applicability and validity of HCC as an indicator for chronic stress or long-term activity of the hypothalamic-pituitary-adrenal axis in wild and domesticated animals. Specific hair characteristics are presented and the advantages and limitations of using HCC are discussed. An overview of findings on the impact of stress- and health-related factors on HCCs and of diverse influencing factors causing variation in hair cortisol levels in different species is given. Recommendations for the use of hair cortisol analysis are proposed and potential fields of future research are pointed out. The studies indicate an effect of age and pregnancy on HCCs, and cortisol incorporation into hair was also found to depend on hair colour, body region, sex and season of year, but these results are less consistent. Furthermore, the results in animals show that a wide array of stressors and pathological conditions alters the cortisol concentrations in hair and that HCC thereby provides a reliable and valid reflection of long-term cortisol secretion in many species. However, more research is necessary to investigate the underlying mechanisms of cortisol incorporation into the hair and to explore the hair growth characteristics in the species of interest. To overcome confounding influences, the use of standardized sampling protocols is strongly advised.

Impacts of estrus expression and intensity during a timed-AI protocol on variables associated with fertility and pregnancy success in Bos indicus-influenced beef cows

This experiment evaluated the impacts of estrus expression and intensity, estimated by physical activity during a timed-AI protocol, on reproductive performance of Bos indicus-influenced beef cows. A total of 290 lactating, primiparous, and multiparous nonpregnant Nelore × Angus cows received a 2 mg injection of estradiol benzoate and an intravaginal progesterone (P4) releasing device (CIDR) on d -11, a 12.5 mg injection of PGF2α on d -4, CIDR removal in addition to 0.6 mg injection of estradiol cypionate and 300 IU injection of eCG on d -2, and timed-AI on d 0. Cows were fitted with a pedometer behind their left shoulder on d -4. An estrus detection patch was attached to the tail-head of each cow on d -2. Pedometer results were recorded on d -2 and 0. Estrus expression was defined as removal of >50% of the rub-off coating from the patch on d 0. Net physical activity during estrus was calculated by subtracting total steps from d -4 to -2 (nonestrus basal activity) from total steps from d -2 to 0 (proestrus + estrus period) of each cow. Cows that did not express estrus were classified as NOESTR. Cows that expressed estrus were ranked by net physical activity; those above the median were classified as HIESTR and the remaining cows as LWESTR. Ovarian ultrasonography was performed on d 0 and 7. Blood was collected on d 0, 7, 20, and 30. Pregnancy status was verified by ultrasonography on d 30. Only data from cows responsive to the estrus synchronization protocol were utilized (NOESTR, n = 59; LWESTR, n = 100; HIESTR, n = 98). Diameter of dominant follicle on d 0, corpus luteum volume on d 7, and plasma P4 concentrations on d 7 were greater (P ≤ 0.05) in HIESTR vs. LWESTR and NOESTR and also greater (P ≤ 0.05) for LWESTR vs. NOESTR. Plasma P4 concentrations on d 0 were greater (P < 0.01) in NOESTR vs. HIESTR and LWESTR and similar (P = 0.93) between HIESTR and LWESTR. Whole blood mRNA expression of myxovirus resistance 2 on d 20 was greater (P ≤ 0.05) in HIESTR vs. LWESTR and NOESTR, and similar (P = 0.72) between LWESTR and NOESTR. Pregnancy rates were less (P ≤ 0.04) in NOESTR vs. HIESTR and LWESTR (52.4%, 68.9%, and 73.5%, SEM = 7.2), and similar (P = 0.57) between HIESTR and LWESTR. Hence, expression of estrus during a timed-AI protocol improved ovarian dynamics and pregnancy success, whereas estrus intensity modulated key biological markers associated with fertility but not pregnancy rates in B. indicus-influenced cows beef cows.