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Summer heat stress in northwest Mexico compromises the physiological thermoregulation capacity and productive performance of lactating Holstein cows, and supplementation of minerals appears to reduce the adverse impact of heat stress in cattle. The objective herein was to evaluate the effects of an injectable mineral supplement containing phosphorus, selenium, potassium, magnesium, and copper on physiological responses, milk production, and milk composition of Holstein cows exposed to heat stress. Sixteen cows were blocked by parity and assigned to one of two treatments (n= 8) using a randomized complete block design: 1) control cows and 2) mineral-treated cows. All cows were exposed to environmental heat stress conditions (i.e., temperature-humidity index = 79.4 ± 4.3 units). No study variable was affected (P ≥ 0.20) by the treatment x sampling day interaction. While the mineral supplement did not affect any physiological variable in the afternoon, this treatment decreased breaths per min (P = 0.01) and most body surface temperatures (P ≤ 0.06; head, shoulder, leg, right-flank, and udder) in the morning. There was no effect (P = 0.37) of the mineral supplementation on milk yield but increased (P ≤ 0.03) the percentages of solids non-fat, protein, lactose, and density in the milk. In conclusion, Holstein cows' physiological thermoregulation and milk composition experiencing summer heat stress were improved by applying an injectable mineral supplement.

The objective of this study was to determine genetic parameter estimates for age at first calving (AFC) in Red Angus and Simmental heifers. The ability for a heifer to calve earlier has implications on calf performance and the heifer's successive re-breeding. Heifer pregnancy data were obtained from International Genetic Solutions, where females with exposure records were included in the population. Females with a subsequent record of calving between 630 and 810 days of age were included in the analysis. Females with embryo transfer or multiple birth progeny were excluded. Records from single-animal and contemporary groups with no variation were eliminated and after data filtering, there were 149,379 Simmental with a mean Simmental breed proportion of 0.58 ± 0.25, and 83,191 Red Angus records with a mean Red Angus breed proportion of 0.80 ± 0.13. A 3-generation pedigree file containing 291,530 Simmental animals with 25,585 unique sires and 161,921 unique dams, and a 3-generation pedigree file containing 174,914 Red Angus animals with 19,733 unique sires and 99,464 unique dams were used for the separate analysis. The mean AFC in Simmental and Red Angus was 724.8 ± 28.64 d, and 724.2 ± 29.93 d, respectively. Data for each breed were modeled separately using a single trait animal model with random additive genetic and residual effects, and the fixed effect of contemporary group using ASReml 3.0. Contemporary group was defined as breeder, herd, year born, birth group and yearling group. The additive, residual, and phenotypic variances for Simmental were 120.08, 520.37, and 640.45 d2, respectively. For Red Angus, 85.67, 543.56, and 629.24 d2 were the additive, residual, and phenotypic variances, respectively. The heritability estimates of AFC for Simmental and Red Angus were 0.19 ± 0.0059 and 0.14 ± 0.0076, respectively. These results demonstrate AFC in days is lowly to moderately heritable. Lower residual and higher additive variance in Simmental compared to Red Angus may suggest the Simmental population has larger variation for underlying fertility influences such as age at puberty. The mean breeding values for AFC in Simmental was 6.1 ± 8.0, with a minimum of -24.4 and maximum of 54.7. Whereas Red Angus breeding values for AFC resulted in a mean of 4.0 ± 5.6 and a minimum and maximum of -16.1, and 37.3, respectively. The comparable heritability estimates, low standard error, and range in breeding values suggest selection for improved AFC can be attained. It is worth further exploring the impact of breed effects and heterosis influences on age at first calving. While this study does not account for heifers that did not calve in their first year, tandem selection for heifer fertility and age at calving should be heavily emphasized due to the economic importance of both traits.

The porcine reproductive and respiratory syndrome (PRRS) is a viral disease that decreases the reproductive performance in breeding sows and leads to economic losses to the swine industry. The objective of the present study was to identify single nucleotide polymorphisms (SNP) associated to the number of live-born piglets in the first (LBP1) and second birth (LBP2) in breeding sows exposed to PRRS virus. The study included 100 pregnant females of the Landrace(¾)/ Yorkshire(¼) line, 75 of which were infected with the PRRS virus and 25 were free of PRRS. Individual blood samples (6-8 drops) were obtained and spotted onto FTA cards and subsequently processed for DNA extraction, which was genotyped using a 10,000 SNP chip for genomic profile. Resulting genotypes were analyzed using a multi-locus mixed model that detected three SNP associated to LBP1 and five SNP associated to LBP2 (P

Pulmonary hypertension is a noninfectious disease of cattle at altitudes1524 m (5,000 ft). Mean pulmonary arterial pressures (PAP) are used as an indicator for pulmonary hypertension in cattle. High PAP cattle (≥50 mmHg) entering the feedlot at moderate elevations have lower feed efficiency as compared to low PAP cattle (50 mmHg). The impact of pulmonary arterial pressure on mitochondrial function, oxidative phosphorylation (OXPHOS) protein abundance, and meat color was examined using longissimus lumborum (LL) from high (98 ± 13 mmHg; n = 5) and low (41 ± 3 mmHg; n = 6) PAP fattened Angus steers (live weight of 588 ± 38 kg) during early postmortem period (2 and 48 h) and retail display (days 1 to 9), respectively. High PAP muscle had greater (P = 0.013) OXPHOS-linked respiration and proton leak-associated respiration than low PAP muscles at 2 h postmortem but rapidly declined to be similar (P = 0.145) to low PAP muscle by 48 h postmortem. OXPHOS protein expression was higher (P = 0.045) in low PAP than high PAP muscle. During retail display, redness, chroma, hue, ratio of reflectance at 630 and 580 nm, and metmyoglobin reducing activity decreased faster (P0.05) in high PAP steaks than low PAP. Lipid oxidation significantly increased (P0.05) in high PAP steaks but not (P0.05) in low PAP. The results indicated that high PAP caused a lower OXPHOS efficiency and greater fuel oxidation rates under conditions of low ATP demand in premortem beef LL muscle; this could explain the lower feed efficiency in high PAP feedlot cattle compared to low PAP counterparts. Mitochondrial integral function (membrane integrity or/and protein function) declined faster in high PAP than low PAP muscle at early postmortem. LL steaks from high PAP animals had lower color stability than those from the low PAP animals during simulated retail display, which could be partially attributed to the loss of muscle mitochondrial function at early postmortem by ROS damage in high PAP muscle.The impact of pulmonary arterial pressure (PAP) on mitochondrial function, oxidative phosphorylation protein abundance, and meat color was examined using longissimus lumborum (LL) from high (98 ± 13 mmHg) and low (41 ± 3 mmHg) PAP fattened Angus steers (live weight of 588 ± 38 kg) during early postmortem period (2 and 48 h) and retail display (days 1 to 9), respectively. The results indicated that high PAP caused a lower oxidative phosphorylation efficiency and greater fuel oxidation rates under conditions of positive energy balance in beef LL muscle. This could explain the lower feed efficiency in high PAP feedlot cattle compared to low PAP counterparts. Mitochondrial integral function declined faster in high PAP than low PAP muscle at early postmortem. LL steaks from high PAP animals had lower color stability than those from the low PAP animals during simulated retail display, which could be partially attributed to the loss of muscle mitochondrial function at early postmortem in high PAP muscle.

Feedlot heart disease (FHD), also known as bovine congestive heart failure, affects feedlot cattle at low to moderate elevations. This disease can cause feedlot death and preliminary research suggests unfavorable influences on performance and carcass quality in those individuals reaching their harvest endpoint. The severity of FHD for an individual animal at harvest can be determined by a heart scoring system that ranges from 1 to 5 corresponding to the increasing degree of heart failure with a score of 1 a normal heart and larger scores indicative of increased malformations. Heart scores (HS) are collected on individual animals at harvest. Previous research indicated that differences exist between sires as to their progeny’s propensity for developing FHD as indicated by HS of 3, 4 and 5. As a result of these sire differences, the objective of this study was to estimate heritability of HS obtained from a group of fattened feedlot cattle. Heart scores, numbers of cattle (Grade 1: 290 ; Grade 2: 728; Grade 3: 340; Grade 4: 64; Grade 5: 0) pedigree, and feedlot pen information were collected from 1,422 individual animals. The pedigree used in the evaluation consisted of the 1,422 individuals and 89 unique sires. No dam information was available on the scored animals. Heritability was estimated using a mixed effect animal model and the statistical software package ASReml 3.0. Fixed effects included scorer, sex, and kill age. Sex was not found to be significant in the model. Individual animal was included as the sole random effect. Scorer (P < 0.05) and kill age (P < 0.1) were found to influence variability in heart score, although kill age was detected as a tendency (P = 0.07). The heritability of HS was estimated to be 0.27 ± 0.10. The genetic variation was 0.15 and the phenotypic variation in the model was 0.40. These results suggest, HS is moderately heritable and has the potential to respond to genetic selection.

Variable precipitation in the western United States impacts forage availability, potentially influencing fertility. Furthermore, producers located above 1,500 meters contend with high altitude disease (HAD) due to reduced atmospheric oxygen, potentially resulting in right sided heart failure. Pulmonary arterial pressure (PAP) score is an indicator trait of HAD. The physiological stress of elevated PAP score could compound environmental stress, such as variable precipitation. Thus, the objective of this study was to investigate the interaction of precipitation and PAP score on beef heifer fertility. Data for this study were sourced from the Colorado State University Beef Improvement Center (CSU-BIC; 1993-2019; n = 3,834; 2,150 to 2,411 m elevation) near Saratoga, Wyoming. Records included identification, birth year, yearling year, yearling weight (YW), PAP, first service conception (FSC), overall heifer pregnancy (HPG) and sire. Precipitation data were sourced from the National Oceanic and Atmospheric Administration. Three classifications were created: cumulative precipitation from birth to breeding, precipitation from heifer birth to weaning, and precipitation from heifer weaning to breeding. Initial models contained sources of variation of precipitation classification, PAP, YW and a PAP by precipitation classification interaction for the response of HPG and FSC. Logistical regression was executed followed by analysis of variance. Yearling weight was a predictor of FSC (P < 0.01) while weaning to breeding precipitation was a predictor for HPG (P < 0.05). In general, the PAP by precipitation interaction was not detected; however, PAP by weaning to breeding precipitation tended to predict HPG (P < 0.10). A favorable, positive relationship was detected between YW and FSC (bi=0.00120 to 00120 to 0.00124; P < 0.01). A favorable, positive relationship also existed between weaning to breeding precipitation and HPG (bi=0.2528, P < 0.05). Those results suggested that increased precipitation during the development period from weaning to breeding was advantageous to HPG. The results also provided evidence to suggest that precipitation and PAP may interact to influence breeding success. Thus, we conclude that increased precipitation during the weaning to breeding period appears advantageous to overall breeding success of Angus heifers in a high-altitude production system.

The objective of this study was to determine heritability and genetic correlation estimates between dry matter intake (DMI) and Stayability in Angus cattle originating from the John E. Rouse Beef Improvement Center. From the years 2015–2021, 640 steers were fed in confinement using a GrowSafe System® to measure individual DMI. The duration of feeding varied each year; however, mean test length was 49 ± 0.31 days with a 21-day warm-up period to allow for acclimation to the environment and ration. A bivariate animal model was used. Stayability was evaluated using a binary, probit threshold model while DMI was evaluated as a continuous trait. In addition to the 640 steers with intake, a total of 1,673 pedigree-related cows possessed a Stayability observation. Cows were awarded a ‘1’ if they maintained functionality within the herd for six years. Those not achieving the six-year threshold were given a ‘0’. Mean DMI calculated for the steers was 10.11 ± 0.12 kg/day while the mean for stayability was 0.59 ± .15 (59% of females in this study remained in the herd for at least six years). Fixed effects in the model included contemporary group and age. Contemporary groups were defined as year, pen and test duration for DMI. Contemporary groups for Stayability were solely the year of birth for a given cohort. Individual animal was included as a random effect for both Stayability and DMI to account for the direct genetic effects for both traits. A 3-generation pedigree file containing 3,421 angus influenced animals with 785 unique sires and 2,425 unique dams was used to link the steers to the cows in this study. Residual covariance between DMI and Stayability in this study was fixed at 0. The heritability estimate for DMI was 0.26 ± 0.12 making it moderately heritable with a phenotypic variance of 9.29 kg2 ± 0.55. The heritability estimate for Stayability was quite low 0.02 ± 0.39. The genetic correlation between DMI and Stayability determined by this model was 0.8211 ± 1.2. Though the heritability is low for Stayability, these results suggested that Angus cows that exhibit higher feed intake tend to have more longevity within the herd.

The aim of this study was to estimate the influence of heterosis and breed percentage on birth weight (BW) and weaning weight (WW) in beef cows in a tropical environment. Data from 900 calves and 2,843 individuals in the pedigree, from the multibreed herd of the Panama Agricultural Innovation Institute (IDIAP) in Gualaca, Panama were used. The herd was comprised of the following genetic groups and according to their breed percentage: tropical adapted Brahman (BR), Nellore (Ne), Un define Bos indicus (BI), Guaymi Creole (CR), Senepol (SP) Romosinuano (RS); Bos taurus (BT), Simmental (SM), Angus (A), Red Angus (AR), Limousin (LM), Charolais (CH), Wagyu (Wa), and Others (Oth); crossbreeds (cx), Beefmaster (BF), Three cx(F1 x different BT), R1(Backcross BR), R2 (Backcross BT), Composite (combination of at least 4 different breeds with less than 25% of Zebu), Upgrade (87.5% BR 12.5% BT), B1 (62.5% Zebu + 37.5% BT), B2 (62.5% BT + 37.5% Zebu). A bivariate animal model for BW and WW, was utilized to estimate variance components. Contemporary group was defined as year of birth. The effects of sex, birth season, weaning season, and age of dam were included as categorical fixed effects. Weaning age, degree of outcross and breed percentage were included as linear covariates. The estimated regression coefficient for BW on heterosis was not significant (P > 0.05), and for WW was 0.072 ± 0.027 kg (P < 0.05). Lower BW and WW were observed for the Japanese, and B1, while R2 and Upgrade had the highest average (P < 0.05). Heritability for BW was found to be low (0.14 ± 0.06) and moderate for WW (0.26 ± 0.09). The proportion of variation of WW accounted by maternal permanent environment for WW was (0.2 ± 0.09). The estimated genetic correlation between additive genetic BW and WW was 0.63 ± 0.30, while a negative, additive genetic correlation was observed for WW and WW maternal (-0.43 ± 0.37). These results suggested that heterosis had a beneficial influence on WW but limited effect on BW. Additionally, increasing the percentage of Wa, and BR negatively influenced WW measurements in a multibreed beef cattle herd in Panama.

Monitoring livestock and forage conditions on extensive rangelands is labor intensive and expensive, and often observations occur infrequently. Technological advancements have made real-time remote monitoring more feasible and less costly. Global positioning system (GPS) tracking data can be transferred from livestock to the internet using cellular phone technologies, low range wide area networks (LoRaWan) and satellite transmissions. With good coverage, cellular-based real time tracking systems work well. Rugged terrain and extensive pastures increase the cost of LoRaWan. Additional LoRaWan gateway towers are needed for data transmission, because these systems rely upon line-of-sight signals. Satellite systems are expensive but hold great potential for rugged terrain. Accelerometers can be used to monitor animal activity, and after on-device summarization the data summary can be transmitted to the internet. Changes in behavior from normal patterns are useful for detecting illness and wellbeing. Bovine ephemeral fever in heifers and perennial ryegrass staggers in sheep were identified by a decrease in activity during the morning and evening grazing bouts using accelerometers. In pen settings, accelerometers were able to detect the timing of lambing and illness associated with unexpected feeding of moldy silage. Continued congregation of livestock at water tanks may indicate water system failures. Normally, animals move away from water to rest after drinking. Tracking is a valuable tool to identify locations where new water developments can improve distribution. Tracking also has potential to notify managers where livestock are congregating and potentially overgrazing, but prediction of forage utilization at light levels is not exact. Tracking systems would also facilitate genetic selection for grazing distribution by providing terrain use phenotypes. Improvements in technology and associated cost reductions of sensors as well as development of algorithms and software potentially gives ranchers mechanisms to remotely monitor livestock wellbeing and rangeland conditions and allow them to respond promptly.

The lactation curve in dairy cows is influenced by the calving season, which is highly dependent on the warm climate in semi-arid regions. Objective herein was to evaluate effects of calving season on the parameters and components of the lactation curve in Holstein cows. The study included 278,317 milk records collected from 1086 cows from the 1st to 5th calving and good body condition score. The cows were grouped according to the season in which they calved: winter-calved (CS1), summer-calved (CS2), and autumn-calved cows (CS3). Ambient temperature and humidity data were used to calculate the temperature-humidity index (THI). The NLIN procedure was used to estimate the parameters of the lactation curve that served to calculate the components. The mixed procedure was executed to analyze the fixed effect of calving season. Associations between lactation curve traits were tested using correlation and regression analyses. A univariate model was utilized to calculate heritability. Average THI values during the lactation period were 73.5, 68.5, and 69.5 units for CS1, CS2, and CS3 groups, respectively. Initial milk production and increasing rate to the maximum milk yield in CS1 and CS3 groups were higher (P 0.05) than CS2 cows. However, persistency and total milk yield during the entire lactation period were superior (P 0.05) for CS2 and CS3 cows compared to CS1 cows, probably due to the moderate heat stress during the lactation period in the CS1 group. In cows from CS2 and CS3 groups, total milk production at 305 days was moderately correlated with initial milk production (r = 0.47; P 0.05), and highly correlated with milk yield at peak day (r = 0.91; P 0.05) which resulted as reliable predictor for total milk yield during the entire lactation (R

Components of the GH/IGF1 endocrine axis regulate growth and reproductive traits in cattle. The pro-melanin-concentrating hormone (PMCH) gene located within chromosome 5 belongs to this axis. Objective herein was to evaluate PMCH single-nucleotide polymorphisms (SNPs) as molecular markers associated with age at first calving, calving interval, and age at second calving in Angus and Brangus beef heifers raised in desert conditions. Five SNPs within the PMCH gene were included in the study. Three of these SNPs had minor allele frequency > 10% and only one SNP did not deviate from Hardy–Weinberg equilibrium. A genotype to phenotype association analyses was performed using a mixed-effects model which included phenotype as the response variable, SNP genotype, breed, year of birth and age of dam as fixed terms, and sire as a random effect. Genotypes from the SNP rs135033882 were found to be associated (P

Climate variability can influence cattle performance. Therefore, the objective of this research was to determine fine-scale genetic diversity in Red Angus cattle in relation to climate zones. One hundred and seventy-five prominent Red Angus artificial insemination (AI) sires were sampled from five conterminous U.S. climate regions (Cool Arid, Cool Humid, Transition Zone, Warm Arid, and Warm Humid). Quantitative and molecular genetic approaches were used to evaluate genetic diversity for the cattle. The first method utilized neutral SNP to determine the genetic structure of the population. The second method used 66 SNP associated with traits potentially influenced by climate (body weight, heat stress, milk yield, heifer conception rate, and early embryonic survival) to detect loci under selection in each zone. Using 13,961 SNP, the genetic structure analysis revealed that there were eight sub-populations present within Red Angus. Furthermore, 23 of the 66 SNP were not in Hardy-Weinberg Equilibrium and loci under selection tests (P

Data for growth and carcass traits were obtained from 738 Brangus heifers (3/8 Brahman-Bos indicus × 5/8 Angus-Bos taurus) registered with International Brangus Breeders Association. Phenotypes included body weights (BW, WW, and YW) collected at birth, ~205 and 365 d of age for growth traits and yearling ultrasound assessment of longissimus muscle area (LMA), percent intramuscular fat (IMF), and depth of rib fat (FAT) for carcass traits and were used to compare univariate and multivariate artificial neural networks (ANN) models with the learning algorithms (Levenberg–Marquardt (LM), Bayesian Regularization (BR) and Scaled Conjugate Gradient (SCG)) and transfer functions (tangent sigmoid and linear) using 1 to 20 neurons models based on the input from G genomic relationship matrix. Pearson correlation coefficients for evaluating model performances in testing datasets indicated that univariate ANN models resulted in better genomic prediction than the multivariate ANN models regardless of the learning algorithms and transfer functions for carcass traits. However, there was no clear difference between univariate and multivariate ANN models about genomic prediction for growth traits. In multivariate ANN models, the prediction performance of the combination of learning algorithms and transfer functions changed for growth and carcass traits and there were no superior multivariate ANN models with BR, LM and SCG learning algorithms and transfer functions. However, the correlation coefficients from univariate ANN-BR model indicated better genomic prediction than univariate ANN-LM and ANN-SCG models. The application of different transfer functions did not make any significant difference on the genomic prediction performance of ANN models with different learning algorithms. Results of this study suggest the use of univariate ANN models with BR learning algorithm for genomic prediction of growth and carcass traits.

Components of the GH/IGF1 endocrine axis regulate growth and reproductive traits in cattle. The pro-melanin-concentrating hormone (PMCH) gene located within chromosome 5 belongs to this axis. Objective herein was to evaluate PMCH single-nucleotide polymorphisms (SNPs) as molecular markers associated with age at first calving, calving interval, and age at second calving in Angus and Brangus beef heifers raised in desert conditions. Five SNPs within the PMCH gene were included in the study. Three of these SNPs had minor allele frequency 10% and only one SNP did not deviate from Hardy-Weinberg equilibrium. A genotype to phenotype association analyses was performed using a mixed-effects model which included phenotype as the response variable, SNP genotype, breed, year of birth and age of dam as fixed terms, and sire as a random effect. Genotypes from the SNP rs135033882 were found to be associated (P 0.05) with all evaluated fertility traits, and the term breed resulted as a significant source of variation only for age at second calving. The allele A was the favorable allele because it decreased the age at first calving 98.6 days, the calving interval 85.3 days, and the age at second calving 183.1 days, in Angus and Brangus heifers. In conclusion, we proposed a SNP within the PMCH gene as a potential candidate marker associated with reproductive performance in Angus and Brangus beef heifers raised in a desert climate.

Grazing distribution is an important aspect of pasture management, yet measuring traits for sustainable forage consumption is challenging. Uplands are often un-grazed by beef cattle due to rugged terrain while riparian zones are often heavily grazed; thus, sustainable consumption may be achieved if improved landscape utilization by cattle is encouraged. Modifying grazing behaviour with fencing and (or) water-source and feeding location(s) is effective in improving grazing patterns; however, these infrastructure improvements are typically expensive, supporting the concept of genetic selection for improved grazing distribution. Efforts funded by the Western Sustainable Research and Education Program (WSARE; SW15-015) using global positioning systems (GPS) indicated a genetic influence on quantitative traits describing grazing distribution of 330 Angus-influenced cows (i.e. distance from water, slope, elevation, vertical climb, etc.). Collars fitted with GPS devices for data collection accrued measures at intervals of 5 to 15 min and 10 m resolution for 3-19 weeks in 16 pastures on 14 ranches and experiment stations. Genome-wide association studies involving trait-measures and high-density genotypes (n = 777,962 single nucleotide polymorphisms; SNP) indicated these traits were polygenic. Combining SNP genotypes with trait measures and pedigree has become the norm in genetic evaluation and improvement processes (i.e. genome-enhanced expected progeny difference (GE-EPD). These processes require data from large numbers of animals (n > 10,000). Collecting grazing distribution phenotypes with GPS collars is accurate, but time-consuming; therefore, collaborative research is being conducted in the 2019-2020 academic year exploring the use of unmanned aerial vehicles (UAV) and cameras to ascertain spatial measures of beef cow grazing distribution. This collaboration involves scientists in the Colorado State University Drone Center, Department of Mechanical Engineering, and Department of Animal Sciences. The project objective is to determine if UAV can expedite data collection to support development of genetic evaluation and improvement programs for grazing distribution.

Data on calving ease (CE) and birth, weaning weight (WW), and yearling weight (YW) were obtained from the American Simmental Association (ASA) and included pedigree and performance information on 11,640,735 animals. Our objective was to quantify differential response from selection for high CE vs. low birth weight (LBW) in first-calf Simmental heifers. We hypothesized that direct selection for CE should be used as the primary approach to reduce dystocia and mitigate losses in growth-related traits. WW and YW were adjusted to 205 and 365 d of age, respectively. Sire and maternal grandsire (co)variance components for CE, birth weight (BW), and 205-d weaning weight (205-d WW), and sire covariance components for 160-d postweaning gain (160-d gain) were estimated using a sire-maternal grandsire model. Direct and maternal expected progeny differences (EPD) for CE, BW, and 205-d WW and direct EPD for 160-d gain and 365-d yearling weight (365-d YW) for first-calf Simmental heifers population (465,710 animals) were estimated using a threshold-linear multivariate maternal animal model. This population was used to estimate genetic trends and as a selection pool (control) for various selection scenarios. Selection scenarios were high CE (HCE), LBW, the all-purpose selection index (API = −1.8 BW + 1.3 CE + 0.10 WW + 0.20 YW) of the ASA and its two derived subindices: (API1 = 1.3 CE + 0.20 YW) and (API2 = −1.8 BW + 0.20 YW), and lastly Dickerson’s selection index (DSI = −3.2 BW + YW). Data for each selection scenario were created by selecting sires with EPD greater than or equal to the average along with the top 75% of dams. Comparison between selection scenarios involved evaluating the direct and maternal genetic trends from these scenarios. Direct heritabilities for CE, BW, 205-d WW, 160-d gain, and 365-d YW of Simmental cattle were 0.23, 0.52, 0.28, 0.21, and 0.33, respectively. The single trait, HCE, selection scenario, as opposed to LBW, increased the intercept for CE by 57.7% and the slopes (P < 0.001) for BW, 205-d WW, 160-d gain, and 365-d YW by 27.9%, 37.5%, 16%, and 28%, respectively. Comparisons of various selection scenarios revealed that the CE-based selection scenarios (HCE, API, and API1) had a greater response for CE and growth traits.

Pulmonary arterial pressure (PAP) is a diagnostic measure used to determine an individual’s susceptibility to developing high-altitude disease. The importance of PAP measures collected at elevations lower than the intended breeding elevation of the bulls (i.e., ≥1,520 m) is unknown. Therefore, the objective of this study was to determine the genetic relationship between PAP measures collected in a range of elevations using reaction norm models. A total of 9,177 PAP and elevation observations on purebred Angus cattle, which averaged 43.49 ± 11.32 mmHg and 1,878.6 ± 296.8 m, respectively, were used in the evaluation. The average age of the individuals in the evaluation was 434.04 ± 115.9 d. A random regression model containing the effects of sex, a linear covariate of age, a quadratic fixed covariate of elevation, and random effects consisting of a contemporary group and a linear regression of PAP on elevation was used for the evaluation of PAP. Two forms of PAP were evaluated with this model. First, to address the non-normality of the data, PAP was raised to the power of −2.6 (ptPAP) based on the results of a Box–Cox analysis. Second, raw PAP (rPAP) phenotypes were evaluated to compare the results to those obtained from the transformed data. For ptPAP, heritability ranged from 0.25 to 0.37 corresponding to elevations of 1,900 and 1,215 m, respectively. For rPAP, heritability ranged from 0.22 to 0.41 corresponding to elevations of 1,700 and 2,495 m, respectively. Generally, lower elevations corresponded to decreased heritabilities while higher elevations corresponded to increased heritability estimates. For ptPAP, genetic correlations ranged from 0.18 (elevation: 1,215 and 2,495 m) to 1.00. For rPAP, genetic correlations ranged from 0.08 (elevation: 1,215 and 2,495 m) to 1.00. In general, the closer the elevations in which PAP was measured, the greater the genetic relationship. The greater the difference in elevation between PAP measures resulted in lower genetic correlations. The rank correlation between expected progeny differences (EPD) for 1,215 and 2,495 m was 0.65 and 0.49 for the ptPAP and rPAP, respectively. These results suggested that PAP measures collected in lower elevations may be used as an indicator of high-altitude adaptability. In the estimation of EPD to rank sires for their suitability for use in high-elevation production systems, it is important to account for the relationships among varied altitudes.