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High Mountain Disease (HMD) in cattle is a consequence of altitude-induced (> 1500 m) pulmonary hypertension (PH). Pulmonary arterial pressure (PAP; mmHg) is an indicator of PH-HMD and moderately heritable. This study analyzed repeated measures of PAP in growing bulls and estimated correlations across elevations and ages. Data included breed, PAP, elevation, weights and ages in spring-born bulls from the Agriculture Research, Development, and Education Center (ARDEC) in Colorado. Five PAP measurements were collected from each bull: 1) Weaning PAP at ARDEC (1,525 m); 2) Yearling PAP at ARDEC (i.e., gain-test); 3) PAP after acclimating for 28 days at Fort Lewis College (FLC; 2,470 m); 4) before returning to ARDEC from FLC after 110 days of grazing; and 5) after re-acclimating for 57 days to the moderate elevation and feeding systems at ARDEC when bulls were 18 months of age. Across these 5 times in Angus (n = 18) and Hereford (n = 12) bulls, PAP measures were: 1) 37.97 ± 0.37; 2) 40.93 ± 0.77; 3) 46.10 ± 1.48; 4) 45.00 ± 1.11; and 5) 42.23 ± 0.67, respectively. Breed and elevation-age were important (P < 0.05) sources of variation. Also, PAP changed (P < 0.05) across the 5 time periods (i.e., increased with altitude and then declined as bulls returned to moderate altitude). Yearling PAP measurements collected at 1,525 m were highly correlated with PAP measures at 2,470 m, as well as a PAP collected at 18.3 ± 0.1 mo of age at 1,525 m (r = 0.93 to 0.99); therefore, suggesting that the yearling PAP measurement collected at 1,525 m in gain-tested bulls was an adequate predictor of PAP at elevations of 1,525 and 2,470 m as bulls aged to 18 months; however, additional study of bovine PAP across elevations, ages, and rates of gain is warranted.

Pulmonary hypertension is a noninfectious disease of cattle at altitudes > 1524 m (5,000 ft). Mean pulmonary arterial pressures (mPAP) ≥ 50 mmHg is used as an indicator for pulmonary hypertension in cattle. Meat quality attribute, such as color, critically influencing consumer purchase decision, is economically significant. However, the effect of pulmonary arterial pressures (PAP) on postmortem beef color has not been investigated. To examine this, instrumental color, metmyoglobin reducing activity (MRA), and lipid oxidation of aged strip loins (longissimus lumborum; LL) steaks from high PAP (98±13; n = 5) and low PAP score (41±3; n = 6) fattened Angus steers (i.e., live weight of ~600 kg) were evaluated during simulated retail display (day 1, 3, 5, 7, 9). A split-plot design was used to analyze the effects of PAP score and display day on instrumental color, MRA, and lipid oxidation. Data analysis was performed using R with the lme4 package as a mixed model, where PAP score (high or low), display day, and their interactions were the fixed effects, and random effect was individual steer. Differences between least square means (P < 0.05) were determined by Tukey’s multiple comparisons. An interaction (P < 0.05) between PAP score and display day for redness (a* value), chroma, hue, and MRA was observed. The LL steaks from high PAP score animal had lower (P < 0.05) redness, chroma, and hue, than from low PAP score steer on day 9. A main effect (P < 0.05) of display day on lipid oxidation of was observed, with lipid oxidation increasing as display days increased. The results of current study indicated that the LL steaks from steers with high PAP score have lower color stability than those from steers with low PAP score during simulated retail display. Research partially supported by USDA-NIFA grant: 2018-67015-28241.

The objective of the study was to evaluate if a genetic relationship exists between pulmonary arterial pressure (PAP) measured at high elevation with traits associated with moderate elevation feedlot and carcass traits. For this analysis, PAP, feed intake, and carcass data were taken from 6,898, 558, and 1,627 animals, respectively. At an elevation of 2,115 m, PAP measurements were collected, then a selective group of steers was relocated to a moderate elevation feedlot (1,500 m) where feed intake data were collected. Genetic relationships were evaluated with 5-trait animal models using REML statistical analysis. For all traits in the analysis, fixed effects and contemporary groups were assigned as well as a direct genetic random effect. For weaning weight, a maternal permanent environmental effect was applied in the analysis. For PAP, the heritability estimate was 0.29 ± 0.03. Genetic correlations between PAP with feedlot traits was positive, with estimates of 0.34 ± 0.20 (average dry matter intake) and 0.05 ± 17 (average daily gain). The strongest genetic correlation between PAP and carcass performance traits were those of rib eye area (-0.30 ± 0.12) and calculated yield grade (0.29 ± 0.13). Genetic correlations between PAP and marbling score, back fat, or hot carcass weight were 0.00 ± 0.13, -0.07 ± 0.13, and 0.14 ± 0.10, respectively. These results suggest a favorable genetic relationship exists between PAP with feedlot and carcass traits.

High altitude disease (HAD) is a hypoxia-influenced pathologic condition experienced by cattle raised at high elevations (> 1,524 m). Pulmonary arterial pressure (PAP) is a common diagnostic tool used as an indicator of susceptibility to develop HAD. Given PAP is moderately heritable, possibilities to genetically reduce the incidence of HAD are feasible. However, an alternative strategy could be given by heterosis, since non-additive genetic effects have been related to survivability and environmental fitness. Therefore, objectives of this study were to determine heterosis and breed percentage effects on PAP measurements. A total of 1,083 cattle with varying percentages of Simmental, Angus, Hereford and Red Angus breeds were used for the study. Such animals’ available information included PAP records, PAP test date, PAP technician, sex, herd of origin and breed percentages of parents. A general linear model was utilized to estimate the effect of heterosis on PAP. Contemporary group (defined as a combination between herd, PAP date, PAP technician and sex) was included as a categorical fixed effect; whereas the age at PAP measurement and the degree of outcross were included as linear covariates. Similarly, breed effects were estimated by including breed percentages of Simmental, Angus, Hereford, Red Angus and “Other” breeds as linear covariates in the model. The general average for PAP measurements in the entire dataset was 41.29 ± 0.22, with range of 26 and 108 mmHg. The estimated regression coefficient for PAP on heterosis was -1.834 ± 1.676 mmHg/percent of outcross (P = 0.276), whereas, the range of breed effects on PAP was 15.08 mmHg. These results suggested that heterosis had no significant effects on PAP measurements. However, further research including other multibreed populations is required in order to better understand if increased levels of heterozygosity could potentially be related to lower PAP scores.

Pulmonary hypertension (PH) and subsequent right heart failure is an economic burden for high altitude beef production systems. An indicator of PH is pulmonary arterial pressure (PAP), which has been used to improve tolerance of cattle to high altitude due to its moderate heritability (0.20 to 0.40). A key mediator of myocardial contraction and relaxation is intracellular signaling of calcium. We hypothesized that genes involved in calcium signaling pathways have a role in susceptibility of cattle to PH at high altitude. Right ventricle tissues were collected from Angus steers (age 12 to 14 months; live weight 387 ± 2.5 kg) fed and harvested at high altitude (2,170 m). Experimental groups consisted of low PAP, healthy (average 39 ± 0.2 mm Hg; n = 7) and high PAP, sick/symptomatic of potential heart failure (average 82 ± 2.9 mm Hg; n = 3) steers. Gene expression counts were estimated from RNA-sequence data and then analyzed with DESeq, resulting in 622 differentially expressed genes between experimental groups (Fold change > 2.0; P < 0.05), after a multiple testing correction with the Benjamini-Hochberg procedure. Ingenuity Pathway Analysis revealed the top disease and biological function as cardiovascular malformation represented by 134 of the differentially expressed genes (P < 0.01). The principal intra-pathway genes identified were TGFβ1, an upstream regulator of ventricular chamber hypertrophy and systolic dysfunction leading to heart failure, and EDN1, a vasoconstrictor with downstream regulatory effects on intracellular calcium availability. Two additional genes, FBLN7, a calcium-binding glycoprotein; and ANKRD2, which interacts with calcium-dependent genes, represented the highest expression fold changes. These results support our hypothesis that calcium-dependent gene regulation appears to be influenced by PH (right ventricle malformation) in Angus steers fed at high altitude.

New breeds can be developed by combining two or more breeds into a composite population, thereby capitalizing on complementarity and retained heterosis. Evaluation of breed formation across generations has not been performed at the molecular level; therefore, we used Brangus cattle (3/8 Brahman x 5/8 Angus) as a model to identify the dynamics of new breed formation across 10 generations. Genotypic data (777,962 SNP) from 68 Brahman, 95 Angus and 59 Brangus prominent AI sires born from 1970 to 2010 were evaluated. Their pedigrees were used to calculate the number of complete Brangus generations using the OptiSel package in R 3.4.2. After standard SNP data filters and linkage disequilibrium pruning, 158,264 SNP genotypes from 220 bulls were chosen. ADMIXTURE analyses were executed using autosomal markers by chromosome, setting K equal to two and three. Brangus animals had 70.4% of Angus composition in all autosomes versus the expected 62.5% (t-test, P < 0.001). When K = 3, the establishment of the Brangus cluster was observed across the genome with a proportional assignment > 0.5. The sex chromosomes deviated from the autosomal pattern. Chromosome X had a high Angus proportion (83%) conserved across generations and Brahman contributed only to 9% of the Y chromosome. Regression analyses of cluster formation among autosomes and across generations showed (P < 0.001) that Angus (β = -0.07) and Brahman (β = -0.03) clusters decreased while Brangus cluster increased (β = 0.10, R(2) = 0.43). Regressions by each autosome followed a similar pattern. Formation of the Brangus cluster became stable after the 5(th) generation. These results provide a view into the evolution of a new breed. [Image: see text]

High altitude disease (HAD) is an environmentally induced pathologic condition experienced by cattle raised at high elevations (>1,524 m). Physiologically, the disease is a consequence of hypoxia-induced pulmonary hypertension, therefore, susceptibility to HAD can be assessed in cattle by measuring the mean pulmonary arterial pressure (mPAP). The evaluation of a bull’s adaptability to higher altitudes is economically relevant and mPAP has a moderate heritability. Reaction norm models have been successfully applied to measure the change in genetic predictions of individuals in response to changes in environment; therefore, the objective of this study was to evaluate the environmental sensitivity of Angus sires to high altitude disease through the use of reaction norm models. Records of mPAP collected by the same veterinarian between 2009 and 2012 from a total of 382 sixteen-month-old Angus bulls (progeny of 132 sires and unknown dams) were used for the analysis. Each bull was tested twice, first at moderate elevation (~1246 m, Hobson, MT) and approximately two months later at a high elevation (~2173 m, Laramie, WY). Expected progeny difference (EPD) for mPAP were estimated using a reaction norm sire model with Legendre polynomials as the base function. Effects in the model included contemporary group (mPAP date of measurement) and elevation as fixed effects and sire as a random regression term (sire random intercept and slope) on environmental descriptor (elevation). A rank correlation of 0.91 between EPD for mPAP estimated at the two elevation points (moderate and high), revealed a small degree of re-ranking of sires mainly due to the existence of heterogeneous genetic (co)variance components for mPAP studied at the two elevations. The previous implies that sires with advantageous EPD for mPAP at low elevations will not necessarily have advantageous EPD for mPAP at high elevations.

Data were analyzed to compare accuracies from PBLUP and GBLUP in 719 heifers (3/8 Brahman, Bos indicus x 5/8 Angus, Bos taurus). Genotypes were from BovineSNP50 Infinium-beadchips. Phenotypes included growth traits (birth weight, 205-day weight, 365-day weight), pre- and post-weaning average daily gains and yearling carcass measures (longissimus dorsi muscle area, percent fat within longissimus dorsi muscle, fat thickness over the 12(th) rib) collected with real-time ultrasound. For cross-validation strategy, genotyped heifers were first divided into ten mutually exclusive groups using K-means clustering on pedigree estimates of additive genetic relationships between animals. All ten combinations of nine groups were used for model training, with cross-validation performed in the group not used in training. Also, two replicated training-testing sets including ten groups were randomly sampled. Accuracies for all traits based on K-means clustering ranged from 0.06 to 0.179 for PBLUP and from 0.047 to 0.268 for GBLUP. However, accuracies for all traits based on random sampling groups were higher than those from K-means clustering and ranged from 0.148 to 0.331 for PBLUP and from 0.143 to 0.283 for GBLUP. Among the growth traits, the accuracy from PBLUP for 205-day weight (0.084) was higher than birth weight (0.065) and 365-day weight (0.060). However, the accuracy from GBLUP for 205-day weight (0.047) was lower than birth weight (0.110) and 365-day weight (0.121). Accuracies from PBLUP (0.084, 0.179, 0.105) and GBLUP (0.225, 0.268, 0.211) for carcass traits (longissimus dorsi muscle area, percent fat within longissimus dorsi muscle, fat thickness over the 12(th) rib) were higher than growth traits. longissimus dorsi muscle area, percent fat within longissimus dorsi muscle, fat thickness over the 12(th) rib had the highest accuracies among all the studied traits. The accuracies of random sampling groups were considerably higher for all traits than the corresponding accuracies obtained by K-means clustering.

Heat stress greatly influences lactating Holstein cattle in southern Sonora Mexico, where the temperature-humidity index (THI) easily exceeds the cow thermal comfort threshold (>72 THI units) from May through October. Despite such warm conditions, some dairy cows are able to maintain their milk production. Using a regression model, daily milk production as a function of daily THI was used to estimate a heat tolerance indicator (HTI) value. The objective of this study was to identify molecular markers associated with HTI in Holstein cows milked during summer. The study included 676 cows from three dairies located in the Yaqui Valley of Sonora Mexico. An individual blood sample was collected and spotted onto FTA cards, from which DNA was extracted and used to genotype 179 tag SNP within 43 genes of the Prolactin and GH-IGF1 pathways. The association analyses among SNP genotypes and HTI values were performed using a mixed effects model for continuous traits. The model included HTI as the response variable, genotype and herd as fixed effects, sire as a random effect, and days in milk as a covariate. Two SNP, one within the Prolactin Receptor gene (rs135164815) and one within the Signal Transducer and Activator of Transcription-4 gene (rs110344022) were associated with HTI (P < 0.01). Least square means for the rs135164815 genotypes AA, AG and GG were 0.365 ± 0.06, 0.217 ± 0.04 and 0.201 ± 0.03 liters/day, respectively; while least square means for the rs110344022 genotypes CC, CT and TT were 0.296 ± 0.05, 0.235 ± 0.04 and 0.183 ± 0.04 liters/day, respectively. In conclusion, two SNP within the Prolactin and GH-IGF1 pathways were predictors of HTI in lactating Holstein cows during the months of summer heat stress. Such results provide evidence of a genetic basis associated with favorable lactation performance under increasing THI during summer.

Reproductive performance in Holstein dairy cattle managed during summer in southern Sonora is a challenge because of high ambient temperature and relative humidity. Both of these factors contribute to heat stress, which influences cow behavior. The physiological response of cows to heat stress is one component of a system-wide gene network. Within this environment, a superior cow's ability to get pregnant early during postpartum is favorable as to reduce the trait days open and to increase productive life. Recently, many reproductive specialists have recommended using pregnancy rate as a measure of reproductive success, after converting this trait into a quantitative value using a linear formula. In comparison to the traditional measure of days open, pregnancy rate calculation includes more easily cows that do not become pregnant; furthermore, the output variable indicates that larger values are more desirable, and therefore, more understandable by dairy producers. The objective herein was to predict pregnancy rate in lactating Holstein cows using molecular markers associated with fertility in Holstein cows under a heat-stressed environment. This study included 500 cows from three dairy herds located in the Yaqui Valley of Sonora. A blood sample was collected from every cow and spotted onto FTA cards. The DNA was extracted from each card and used to genotype 179 tag SNP within 43 genes in the prolactin and GH-IGF1 pathways. Five SNP within the genes IGFBP7, IGFBP2, PAPPA1, SSTR2, and STAT6 were associated with pregnancy rate using a mixed effects model. The genotype term was later included in this model to calculate allele substitution effects. Molecular breeding values of the individual cows were calculated by summing the additive genotype effect for each SNP that showed a significant independent association with pregnancy rate, and the average MBV was 0.46 ± 0.01%. Two statistical regression models were used to predict the variable pregnancy rate: a full model that included effects of days and number of lactations, contemporary group (e.g., farm management group), health status, and MBV and a reduced model that only included MBV. Coefficients of determination were 37.61% and 3.07% for full and reduced models, respectively (P < 0.01). These results indicate that five SNP explained only a small proportion of the additive genetic variance for pregnancy rate. Additional research is needed to understand if these results are due to low heritability/repeatability of a fertility and (or) if these results are also influenced by heat stress.