Single nucleotide polymorphisms of growth hormone gene in cattle and their association with growth traits: a systematic review.

Growth traits in livestock animals are quantitative parameters, which are often controlled by many genes including growth hormone (GH) gene. However, the evidence of effect of GH gene on growth traits of cattle is poorly understood. Hence, the objective of the study was to systematically investigate the literature on single nucleotide polymorphisms (SNPs) of GH gene and their association with growth traits in cattle from four databases Google Scholar, PubMed, ScienceDirect, and Web of Science. The results indicated that fifteen (n = 15) articles with 27% of them from Indonesia qualified to be used in this study after screening. The results revealed five SNPs (1047T > C, 1180 C > T, 86,273,136 A/G, 3338 A > G and 4251 C > T) occurred across multiple investigated breeds with no common identified SNPs. Six articles observed a significant difference (p < 0.05) between growth traits and genotypes of identified SNPs. The findings showed that 7 articles (47%) investigated body weight (BW) with 6 (40%) of them found non-significant and 1 (7%) found a significant association with genotypes of the identified SNPs (3338 A > G). While 7 articles (47%) investigated weaning weight (WW) with 5 (33%) of them revealed a non-significant and 2 (13%) found a significant association with genotypes of identified SNPs (3338 A > G and 4251 C > T). This study shows that there is a lack of evidence on effect of growth hormone gene on growth traits in cattle. However, more studies are recommended for further validation of the identified SNPs and effect of growth hormone gene on growth traits in cattle.

Role of Melatonin in Bovine Reproductive Biotechnology.

Melatonin has profound antioxidant activity and numerous functions in humans as well as in livestock and poultry. Additionally, melatonin plays an important role in regulating the biological rhythms of animals. Combining melatonin with scientific breeding management has considerable potential for optimizing animal physiological functions, but this idea still faces significant challenges. In this review, we summarized the beneficial effects of melatonin supplementation on physiology and reproductive processes in cattle, including granulosa cells, oocytes, circadian rhythm, stress, inflammation, testicular function, spermatogenesis, and semen cryopreservation. There is much emerging evidence that melatonin can profoundly affect cattle. In the future, we hope that melatonin can not only be applied to cattle, but can also be used to safely and effectively improve the efficiency of animal husbandry.

Effect of substitution of distillers grains and glycerin for steam-flaked corn in finishing cattle diets on growth performance and carcass characteristics.

An experiment was conducted to determine the effect of substituting modified corn distillers grains with solubles (DGS) or crude soy glycerin (CG) for steam-flaked corn (SFC) in finishing diets on growth performance and carcass characteristics. Treatments were arranged as a 2 × 2 factorial with DGS (0% or 40%) and CG (0% or 10%) replacing dietary SFC in a basal diet. Growth performance and carcass traits were measured on 48 individually fed crossbred yearling cattle (21 steers and 27 heifers; 380 ± 37 kg). Cattle were randomly allotted to 48 Calan gate bunks. After the first 28 days, nine animals were removed from the study for health reasons or observed confirmation of consumption of feed from unassigned Calan gate bunk (n = 39). After the feeding period, cattle were harvested in two groups on day-124 and day-173. No DGS × CG interactions were observed (P > 0.10) for any dependent growth performance or carcass characteristic variable tested. Cattle-fed DGS as 40% of diet dry matter (DM) had greater (P< 0.01) dry matter intake (DMI), while CG inclusion at 10% of diet DM did not affect DMI (P = 0.16). Carcass-adjusted average daily gain (ADG) was not affected by DGS (P = 0.73) or CG (P = 0.28). Decreased (P = 0.03) carcass-adjusted gain-to-feed (G:F) was observed as the main effect of DGS. Greater DMI resulting from feeding DGS as 40% of diet DM appears to have driven the tendency for reduced G:F. Hot carcass weight, longissimus muscle area, 12th rib fat depth, yield grade, and marbling score were not (P> 0.10) influenced by DGS or CG. However, kidney, pelvic, fat (KPH) was increased (P = 0.01) when cattle were fed DGS as 40% of diet DM. Based on the findings presented, it is concluded that CG can substitute up to 10% of SFC in the diet without negatively affecting cattle growth performance or carcass characteristics, regardless of DGS inclusion as 40% of the diet DM.

Livestock producers have an opportunity to improve sustainably through the utilization of co-products of the bio-fuel industry through cattle feeding. Crude glycerin, although less commonly fed compared to distillers grains, provides an opportunity for cattle feeders to increase the versatility of feed ingredient sources without compromising performance. The present study examined the effect of substituting modified corn distillers grains and crude soy glycerin for steam­flaked corn in beef cattle finishing diets on cattle growth performance and carcass characteristics. Growth performance was not influenced by treatment suggesting that crude glycerin and modified corn distillers grains in finishing diets were effective substitutions for steam­flaked corn when market price permits.

Veterinarian perceptions on the care of surplus dairy calves.

Both male and female calves that are not required in the dairy herd sometimes receive inadequate care on dairy farms. Veterinarians work with farmers to improve animal care, and farmers often view veterinarians as trusted advisors; however, little is known about the attitudes of veterinarians on surplus calves. This study investigated the perspectives of Canadian cattle veterinarians on the care and management of surplus calves, as well as how they view their role in improving care. We conducted 10 focus groups with a total of 45 veterinarians from 8 provinces across Canada. Recorded audio files were transcribed, anonymized, and coded using thematic analysis. We found that veterinarians approached surplus calf management issues from a wide lens, with 2 major themes emerging: (1) problematic aspects of surplus calf management, including colostrum management, transportation, and euthanasia, and suggested management and structural solutions, including ways to improve the economic value of these calves, and (2) the veterinarian's role in advising dairy farmers on the care of surplus calves, including on technical issues, and more broadly working with farmers to better address public concerns. We conclude that veterinarians are concerned about the care of surplus calves on dairy farms and believe that they have an important role in developing solutions together with their farmer clientele.

Development of a multivariable prediction model to identify dairy calves too young to be transported to auction markets in Canada using simple physical examination and body weight.

Calves born on Eastern Canadian dairy farms that are not kept in the herds are traditionally sold through auction markets and are raised for meat purposes such as veal calves. Since February 2020, a new Canadian federal regulation has forbidden calves <9 d old to be sold through auction markets. However, in the absence of a real-time birth registry consultation system, it would be of interest to look for predictors that could be associated with age to allow identification of calves too young to be transported. In the current retrospective cross-sectional study, 1,178 calves with a declared birth date (411 calves aged <9 d old; 34.9%) were assessed in 2 large Québec auction sites. Easy-to-record covariates [body weight (BW), breed phenotype, and presence of an umbilical cord remnant] as well as other clinical signs (umbilical swelling, enlargement, umbilical pain, wet umbilicus, skin tent, sunken eyes, ocular and nasal secretion, and hide cleanliness) were assessed. Two logistic regression models using age as a dichotomous dependent variable (<9 d old vs ≥9 d old) were built. The first model (model 1) considered all covariates, which were selected after univariable analyses and a backward stepwise selection process, whereas a more pragmatic model (model 2) only included the 3 easy-to-record variables (i.e., BW, breed, umbilical cord). Both models had similar accuracy to detect calves <9 d old (sensitivity of 38.4 and 37.5%, and specificity of 85.7 and 84.6% for model 1 and 2, respectively). Model 2 was subsequently more specifically studied as it employs a faster and easier assessment. Decision thresholds were tested for their robustness based on misclassification cost term (MCT) analysis with various prevalence of calves <9 d old and various costs of false-negative:false-positive ratio. Despite statistical significance, model accuracy, even if refined with MCT analysis, was limited at the individual level, showing the limits of using physical signs and BW or their combination as a reliable proxy of age. The sensitivity of these models to find calves <9 d old was not to be used for monitoring compliance with the Canadian federal regulation. The relatively high model specificity may help to use this model as a rule-in test (i.e., targeting positive calves for further investigation) rather than a rule-out test (due to its low sensitivity).

Weaning age influences indicators of rumen function and development in female Holstein calves.

BACKGROUND: Prenatal and postnatal conditions are crucial for the development of calves. Primiparous cows are still maturing during pregnancy, thus competing with the nutritional needs of their offspring. Therefore, mature cows might provide a superior intrauterine condition. Furthermore, weaning calves at an older age might affect them positively as well by reducing stress and offering time for various organs and their functions to develop. We aimed to evaluate effects of mothers' parity and calves' weaning age on gastrointestinal development and corresponding acid-base balance. Fifty-nine female German Holstein calves (about 8 days old) were investigated in a 2 × 2 factorial experiment with factors weaning age (7 vs. 17 weeks) and parity of mother (primiparous vs. multiparous). Calves were randomly assigned to one of these four groups. Animal behavior that was observed included resting, chewing and active behavior. RESULTS: Behavioral patterns were interactively affected by time and weaning age. Rumen sounds per 2 min increased in early-weaned calves during their weaning period. In late-weaned calves a consistently increase in rumen sounds was already recorded before their weaning period. Urinary N-containing compounds (creatinine, hippuric acid, uric acid, urea, allantoin) were interactively affected by time and weaning age. Concentrations of all measured compounds except urea increased during early weaning. All except hippuric acid concentration decreased in early-weaned calves after weaning. In late-weaned calves allantoin and uric acid increased before weaning and did not change during weaning. CONCLUSION: These results suggest that late-weaned calves developed adequate rumen functions and acid-base balance, whereas early-weaned calves might have suffered from ruminal acidosis and catabolism. Weaning calves at 7 weeks of age might be too early for an adequate rumen development.

The metabolomics profile of growth rate in grazing beef cattle.

This study aimed to determine the relationship between the metabolome and changes in growth rate (i.e., liveweight change, LWC) and molasses-lick block supplement intake (MLB) of grazing cattle. Weaner beef cattle were fed for 220 days with a sequence of feed types and blood samples, growth rate, and supplement intake were taken on five points in time. The relative abundance (RA) of plasma metabolites were determined using proton nuclear magnetic resonance (NMR). Sixty-four per cent of the metabolites identified were associated with LWC but only 26% with MLB intake (P < 0.05). Periods with faster growth rate showed high availability of amino acids (i.e., valine, leucine, isoleucine, phenylalanine and tyrosine), acetate, and 3-hydroxybutyrate. Periods with lower growth rate were associated with high RA of lipids, choline and acetate. The metabolic profile of individual animals during a period of compensatory growth (after periods of poor performance) showed that high-performing animals were characterised by lower RA of amino acids (i.e., valine, leucine, isoleucine, methylhistidine), creatinine, creatine, pyruvate, 3-hydroxybutyrate, and acetyl groups. It is speculated that high-performing animals have faster uptake of these metabolites from the bloodstream. Cattle growth rate over time was associated with their metabolome which could be used to ensure that the availability of certain metabolites promoting growth is tailored in feed supplements to improve production.

Effects of group housing and incremental hay supplementation in calf starters at different ages on growth performance, behavior, and health.

The present study examined the effects of age at group housing and age at incremental hay supplementation in calf starters from 7.5 to 15% (dry matter, DM) and their interaction on growth performance, behavior, health of dairy calves, and development of heifers through first breeding. A total of 64 calves (n = 16 calves/treatment, 8 male and 8 female) were randomly assigned to 4 treatments in a 2 × 2 factorial arrangement, with age at group housing (early = d 28 ± 2, EG vs. late = d 70 ± 2, LG; 4 calves per group) and age at incremental hay supplementation of calf starters from 7.5 to 15% of DM (early = d 42 ± 2 d, EH vs. late = d 77 ± 2, LH) as the main factors. All calves (female and male) were weaned at 63 days of age and observed until 90 days of age. Heifer calves were managed uniformly from 90 days of age until first calving to evaluate the long-term effects of treatment. No interactions were observed between age at group housing and age at incremental hay to calves on starter feed intake, performance, calf health and behavior, and heifer development through first breeding, which was contrary to our hypothesis. The age at which incremental hay supplementation was administered had no effect on starter feed intake, growth performance, or heifer development until first calving. When EG calves were compared with LG calves, nutrient intake (starter, total dry matter, metabolizable energy, neutral detergent fiber, starch, and crude protein), average daily gain, and final body weight increased. In addition, frequency of standing decreased and time and frequency of eating increased in EG calves compared to LG calves. Overall, early group housing leads to improved growth performance in dairy calves with no negative effects on calf health compared to late group housing.

Non-invasive metabolomics biomarkers of production efficiency and beef carcass quality traits.

The inter-cattle growth variations stem from the interaction of many metabolic processes making animal selection difficult. We hypothesized that growth could be predicted using metabolomics. Urinary biomarkers of cattle feed efficiency were explored using mass spectrometry-based untargeted and targeted metabolomics. Feed intake and weight-gain was measured in steers (n = 75) on forage-based growing rations (stage-1, 84 days) followed by high-concentrate finishing rations (stage-2, 84 days). Urine from days 0, 21, 42, 63, and 83 in each stage were analyzed from steers with the greater (n = 14) and least (n = 14) average-daily-gain (ADG) and comparable dry-matter-intake (DMI; within 0.32 SD of the mean). Steers were slaughtered after stage-2. Adjusted fat-thickness and carcass-yield-grade increased in greater-ADG-cattle selected in stage-1, but carcass traits did not differ between ADG-selected in stage-2. Overall 85 untargeted metabolites segregated greater- and least-ADG animals, with overlap across diets (both stages) and breed type, despite sampling time effects. Total 18-bile acids (BAs) and 5-steroids were quantified and associated with performance and carcass quality across ADG-classification depending on the stage. Stepwise logistic regression of urinary BA and steroids had > 90% accuracy identifying efficient-ADG-steers. Urine metabolomics provides new insight into the physiological mechanisms and potential biomarkers for feed efficiency.

Copy number variation of bovine DYNC1I2 gene is associated with body conformation traits in chinese beef cattle.

Previous, studies have shown that the dynein transporter compound has a role in diseases such as intellectual disability and cerebral malformations. However, the study of CNV in DYNC1I2 gene has not been reported. Q-PCR and data association analysis were used for DYNC1I2 gene copy in this study. In this study, blood samples were collected from five breeds of Chinese cattle (Qingchuan cattle, Xianan cattle, Yunling cattle, Pinan cattle and Guyuan cattle) for DYNC1I2 gene CNV type detection. SPSS 20.0 software and method of ANOVA were used to analyzed the association between types of CNV and growth traits. Results reveal that the distribution of different copy number types in different cattle breeds is different. Association analysis indicate that CNV of DYNC1I2 gene showed a positive effect in cattle growth: in XN cattle, individuals with deletion types showed better performance on height at hip cross (P < 0.05); individuals with duplication types have better performance on body length (P < 0.05) in PN cattle; individuals with deletion types was significantly correlated with chest width and Hucklebone width (P < 0.05) in QC cattle; individuals with duplication types in Yunling cattle were better than the normal types, and there was a significant correlation between copy number variant and chest depth (P < 0.05). The results showed that CNV markers closely related to cattle production traits were detected at DNA level, which could be used as an important candidate molecular marker for marker-assisted selection of growth traits in Chinese cattle, and provided a new research basis for genetics and breeding of Chinese beef cattle.

The relationship between MFN1 copy number variation and growth traits of beef cattle.

Copy number variation, as a kind of genetic submicroscopic structural variation, refers to the deletion or repetition of a large segment of genomic DNA, involving a segment size ranging from 50 bp to several MB. Mitochondrial fusion protein (MFN1) gene regulates the fusion of mitochondrial outer membrane in cells and maintains the dynamic needs of reticular mitochondria in cells. In this study, we conducted to tested the dstribution characteristics of MFN1-CNV in 522 cattles across Xianan cattle (XN), Pinan cattle (PN), Qinchuan cattle (QC), Jiaxian cattle (JX), Yunling cattle (YL), and correlated it with phenotypic traits. Then we observed the expression of MFN1 in various tissues of QC cattle (n = 3), and the expression levels were higher in lung and muscle. The results showed that there was significant correlation between MFN1 gene CNV and hucklebone width of QC cattle, hip width and height at sacrum of JX red cattle, chest width and rump length of YL cattle (P < 0.05). Individuals with duplication type were better than the type of normal or deletion in phenotypic traits. In conclusion, our data showed the correlation between MFN1 gene and growth traits of Chinese cattle. MFN1 gene can be used as a molecular marker for cattle selection and breeding, and accelerate the improvement of Chinese cattle.

Growth performances, nutrient digestibility, ruminal fermentation and energy partition of Thai native steers fed exclusive rice straw and fermented sugarcane bagasse with Lactobacillus, cellulase and molasses.

The study aimed to evaluate the effect of sugarcane bagasse feeding treated with Lactobacillus casei TH14 (L. casei TH14), cellulase and molasses (BG) on nutrient digestibility, ruminal fermentation, energy partition and growth performances of Thai native steers compared to conventional feeding of rice straw (RS). Eight Thai native steers (144 ± 19.5 kg of initial body weight) were randomly allocated to two roughage sources in a completed randomized design: RS (n = 4) and BG (n = 4). The feeding trial lasted for 90 days plus 21 days for treatment adaptation. The results showed that the BG group showed (p < 0.05) greater intake (2.34 vs 2.02 kg/day), total intake (3.90 vs 3.55 kg/day) and average daily gain (0.27 vs 0.23 kg/day) while feed conversion ratio was lower compared to RS group. The BG group had a greater (p < 0.05) organic matter and acid detergent fibre intake than the RS group as well as dry matter and neutral detergent fibre digestibility. The steers fed RS and BG were significantly (p < 0.05) different for total volatile fatty acids and propionic acid at 4 h after offering the diet. The intake of nitrogen (g/day) and apparent nitrogen absorption was significantly (p < 0.05) higher for BG than the RS group while nitrogen excretion in faeces was significantly lower in RS than the BG group. BG group showed significantly (p < 0.05) greater gross energy intake and digestible energy partition when compared to the RS group. In conclusion, feeding BG enhanced feed utilization, growth performance, ruminal fermentation, nitrogen utilization and energy utilization.

Carcass characteristics and meat evaluation of cattle finished in temperate pasture and supplemented with natural additive containing clove, cashew oil, castor oils, and a microencapsulated blend of eugenol, thymol, and vanillin.

BACKGROUND: Forty crossbred steers were supplemented with different doses (from 0 control to 6000 mg/animal/day) of natural additive blend containing clove essential oil, cashew oil, castor oil, and a microencapsulated blend of eugenol, thymol, and vanillin for 80 days. Carcass characteristics, drip loss, and antioxidant activity were evaluated 24 h post mortem on longissimus thoracis, and the effects of aging (until 14 days) were evaluated for water losses (thawing/aging and cooking), texture, color, and lipid oxidation. RESULTS: The use of the natural additive blend did not modify (P > 0.05) carcass characteristics but did, however, modify body composition (P < 0.05). Drip losses were unaffected by the treatments tested (P > 0.05). There was an observed quadratic effect (P < 0.05) on losses from thawing/aging on the first day of storage. Regarding the effects of natural additives on cooking losses, there was a quadratic effect (P < 0.05) among the treatments on day 7 of aging. Differences between days of aging were only observed with control treatment. Shear force was similar among treatments on days 1 and 7 of aging. On day 14 a linear effect (P < 0.05) was observed. Also, a linear effect (P < 0.05) appeared on meat lightness, meat from the control group being clearer on day 1. No changes were observed in redness among treatments or days of storage (P > 0.05). Yellowness was not modified by the treatments (P > 0.05)but only by the days of storage in control and the lowest dosage used. CONCLUSION: The blend of natural additives has potential use in pasture feeding and could improve meat quality. However, doses should be adjusted. © 2021 Society of Chemical Industry.

Feeding strategies impact animal growth and beef color and tenderness.

The impact of growth rate (GR) and finishing regime (FR) on growth and meat quality traits of Angus x Nellore crossbred steers, harvested at a constant body weight (530 ± 20 kg) or time on feed (140 days), was evaluated. Treatments were: 1) feedlot, high GR; 2) feedlot, low GR; 3) pasture, high GR and 4) pasture, low GR. Live body composition, carcass and meat quality traits were evaluated. High GR had greater impact on muscle and fat deposition in feedlot-finished, but not in pasture-finished animals. Feedlot animals had higher Longissimus muscle area, backfat thickness, meat luminosity and tenderness when compared to pasture groups. Moreover, pasture- and feedlot-finished animals with similar GR did not differ in the chromatic attributes of non-aged meat, regardless of endpoint. Thus, GR appeared to be the main factor driving beef chromatic parameters, while FR had a major impact on achromatic attributes and tenderness of meat.

Effect of copy number variation of PLA2G2A gene to growth traits in Chinese cattle.

SIMPLE SUMMARY: As a member of genetic polymorphism, copy number variation has been a commonly used method in the world for investigating effect of genetic polymorphism on gene expression. Effect of genetic polymorphism made on livestock development has been more and more important in beef cattle molecular breeding. The characteristics of Chinese cattle are excellent meat quality, tolerant to rough feeding, good environmental adaptability and so on. But there are some obvious weaknesses still exist in the process of cattle growth and development, such as weak hindquarters and growth slowly. To improve the growth performance and market competitiveness of Chinese cattle, a lot of studies have been made about finding and investigating effective molecular marker. In this study, Q-PCR and data association analysis were used for PLA2G2A gene copy number variation detection and related effect analysis in Chinese cattle. Results showed that PLA2G2A gene has a significant effect on two breeds of Chinese cattle on growth traits, which could be a basic materials and effective information of cattle molecular markers breeding. PLA2G2A, member of secreted phospholipases A2 (sPLA2) in superfamily of phospholipase A2, could catalyze the process of glycerophospholipids hydrolysis from position of sn-2 acyl with the release of free fatty acids and lysophospholipids. Researches about PLA2G2A gene are mostly focus on disease, including tumors and diabetes, the number of study occurred on animal breeding is weak. In this study, blood samples were collected from five breeds of Chinese cattle (Qingchuan cattle, Xianan cattle, Yunling cattle, Pinan cattle and Guyuan cattle) for PLA2G2A gene CNV type detection. SPSS 20.0 software and method of ANOVA were used to analyzed the association between types of CNV and growth traits. Results reveal that the distribution of different copy number types in different cattle breeds is different. In QC, XN and GY cattle, the frequencies of Deletion and Duplication are about 40%; in YL cattle, the frequency of Deletion type exceeds 60%; in PN cattle, the frequency of Duplication is closed to 80%. Association analysis indicate that CNV of PLA2G2A gene showed a positive effect in cattle growth: in QC cattle, Chest depth with Normal type copy number possess a increased trend (P < 0.05); individuals with Deletion type copy number have better performance on Height at sacrum, Heart girth and Body height in GY cattle (P < 0.05). The functional role and molecular mechanism of PLA2G2A gene in animal growth and development are still unclear, and it is necessary for processing a further research. This research aims to provide basic materials for molecular breeding of Chinese cattle.

Effect of vitamin A injection at birth on intramuscular fat development and meat quality in beef cattle.

This study aimed to evaluate intramuscular fat and expression of genes in the muscle of Montana × Nellore treated with vitamin A at birth. We hypothesized that an injection of vitamin A after birth would increase marbling by increasing the expression of angiogenic, adipogenic, and lipogenic genes. Animals treated with vitamin A had greater marbling in the longissimus muscle (P = 0.05). The vitamin A treatment increased the expression of VEGFA gene at 40 days of age and at weaning and increased the expression of ZNF423 at weaning and at harvesting (P ≤ 0.03). The expression of WNT was higher (P = 0.01) at 40 days of age and at weaning in the animals treated with vitamin A. Vitamin A also increased the expression of SREBF1 at 40 days of age and at weaning (P ≤ 0.05). Therefore, the administration of vitamin A to cattle at birth could be a way to increase carcass marbling without affecting the performance of the animals.

Body composition and composition of gain of growing beef bulls fed rations with varying energy concentrations.

Data on chemical body composition of cattle serve as a basis for recommendations on energy and nutrient requirements. Relevant data of growing dual-purpose Fleckvieh (German Simmental) bulls are scarce and originate from old trials, covering low rates of gain and live weights. Hence, the aim of the study was to analyze the body tissue distribution, chemical composition, and composition of body weight gain of growing Fleckvieh bulls within a 120-780 kg live weight range. Results showed that body composition changed during growth but was not affected by dietary energy concentration. Changes in body composition were characterized by increasing shares of fat tissue and ether extract. Body tissues as blood, organs, gastrointestinal tract, and bone proportionately decreased during growth, while muscle and tendon proportions remained constant. The bulls featured enhanced growth potential and high muscle and protein gain throughout the described weight range. The requirements for metabolizable protein in relation to energy decrease with increasing live weight of the animals.

Discovering of Genomic Variations Associated to Growth Traits by GWAS in Braunvieh Cattle.

A genome-wide association study (GWAS) was performed to elucidate genetic architecture of growth traits in Braunvieh cattle. Methods: The study included 300 genotyped animals by the GeneSeek® Genomic Profiler Bovine LDv.4 panel; after quality control, 22,734 SNP and 276 animals were maintained in the analysis. The examined phenotypic data considered birth (BW), weaning (WW), and yearling weights. The association analysis was performed using the principal components method via the egscore function of the GenABEL version 1.8-0 package in the R environment. The marker rs133262280 located in BTA 22 was associated with BW, and two SNPs were associated with WW, rs43668789 (BTA 11) and rs136155567 (BTA 27). New QTL associated with these liveweight traits and four positional and functional candidate genes potentially involved in variations of the analyzed traits were identified. The most important genes in these genomic regions were MCM2 (minichromosome maintenance complex component 2), TPRA1 (transmembrane protein adipocyte associated 1), GALM (galactose mutarotase), and NRG1 (neuregulin 1), related to embryonic cleavage, bone and tissue growth, cell adhesion, and organic development. This study is the first to present a GWAS conducted in Braunvieh cattle in Mexico providing evidence for genetic architecture of assessed growth traits. Further specific analysis of found associated genes and regions will clarify its contribution to the genetic basis of growth-related traits.

Responses of beef calves to long-term heat stress exposure by evaluating growth performance, physiological, blood and behavioral parameters.

The objective of this study was to explore the responses of beef calves to long-term heat stress (HS) exposure at various levels in comparison with the animals under thermoneutral conditions by evaluating growth performance, physiological, blood, and behavioural parameters. Data were collected from sixteen beef calves (BW: 136.9 ± 6.23 kg; age: 169.6 ± 4.60 d) kept at four stress levels of designated temperature humidity index (THI): threshold (22-24 °C, 60%; THI = 70 to 73), mild (26-28 °C, 60%; THI = 74 to 76), moderate (29-31 °C, 80%; THI = 81 to 83), and severe (32-34 °C, 80%; THI = 89 to 91) stress levels in climatic controlled chambers. Feed and water intake were recorded daily, and body weight was measured once a week. Blood was sampled every three days to analyse metabolite parameters. Dry matter intake (DMI) (p = 0.069, tendency) and blood glucose levels (p = 0.028) were decreased after sudden exposure to HS conditions (severe THI levels). Also, blood cortisol (p = 0.002), glutamic-oxaloacetic transaminase (GOT) (p = 0.009), blood urea nitrogen (BUN) (p = 0.004) and standing time (p = 0.009) were increased in moderate and severe THI levels compared with threshold after exposure to HS conditions. However, in the severe THI group, blood cortisol (p < 0.05), glucose (p < 0.05), GOT (p < 0.05) and BUN (p < 0.05) levels were returned to normal range after 6-13 days of continuous HS exposure. In conclusion, DMI, blood cortisol, GOT, glucose, BUN, and standing time were closely associated with long-term HS condition in beef calves. In addition, calves exposed to HS modulated their physiological responses that resulted in the regulation of the pertinent blood metabolites in the blood to maintain homeostasis during the long-term HS.

Screening microchip sites to predict body temperature in young calves.

Thermal microchip sensors can automate body temperature measurements. The best site of implantation is still unknown, and the accuracy and precision of body temperature predictions based on microchip data need to be investigated. The aim of this study was to investigate the best site for microchip implant for monitoring body temperature in dairy calves. Seventeen calves were used (32.2 ± 5.2 kg of body weight) and the microchips were implanted four days after birth. The microchips were implanted at navel, ear and tail base (subcutaneous), neck (cleidocephalicus) and internal face of leg (gracilis) (intramuscular). Rectal temperature (RT, °C), obtained with a clinical thermometer, was considered as core temperature. Air temperature (AT), relative humidity (RH) and the temperature and humidity index (THI) were evaluated at the same time of rectal and microchip temperature measurements over 56 days. The range of AT, RH and THI was 7.6-34.4 °C, 17.5-99.0% and 50.6 to 91.5. The average for rectum, ear, neck, tail, leg, and navel were 38.7; 36.9; 38.0; 37.0, 37.8 and 37.0 °C. The intramuscular implantations had closest values to RT. The correlations between RT and ear, neck, tail, leg, and navel temperatures were 0.56, 0.60, 0.60, 0.53 e 0.48. The RT prediction based on microchip data had precision (rc) ranged between 0.49 and 0.60 and accuracy (Cb) between 0.79 and 0.88. The inclusion of AT, RH and THI as predictive variables in models decrease the mean absolute error (23%) and increase the precision (21.3%) and accuracy (10.2%). The Concordance Correlation Coefficient and root-mean-square error for equations using tail or neck microchips were 0.68 and 0.67, and 0.29 and 0.28 °C, respectively. The tail base is a promising site for microchip implantation to predict rectal temperature. The inclusion of air temperature as a predictive variable in the models is recommended.