Managing the reproductive performance of beef cows

Weighted single step GWAS reveals genomic regions associated with economic traits in Murrah buffaloes

The objective of the present study was to identify genomic regions influencing economic traits in Murrah buffaloes using weighted single step Genome Wide Association Analysis (WssGWAS). Data on 2000 animals, out of which 120 were genotyped using a double digest Restriction site Associated DNA (ddRAD) sequencing approach. The phenotypic data were collected from NDRI, India, on growth traits, viz., body weight at 6M (month), 12M, 18M and 24M, production traits like 305D (day) milk yield, lactation length (LL) and dry period (DP) and reproduction traits like age at first calving (AFC), calving interval (CI) and first service period (FSP). The biallelic genotypic data consisted of 49353 markers post-quality check. The heritability estimates were moderate to high, low to moderate, low for growth, production, reproduction traits, respectively. Important genomic regions explaining more than 0.5% of the total additive genetic variance explained by 30 adjacent SNPs were selected for further analysis of candidate genes. In this study, 105 genomic regions were associated with growth, 35 genomic regions with production and 42 window regions with reproduction traits. Different candidate genes were identified in these genomic regions, of which important are OSBPL8, NAP1L1 for growth, CNTNAP2 for production and ILDR2, TADA1 and POGK for reproduction traits.

The effect of live body condition score of beef cows on carcass characteristics, carcass-cutting yields, processor profitability, and tenderness in the longissimus lumborum and psoas major muscles

The objective of this study was to investigate the effects of body condition score (BCS) of cull cows on carcass characteristics, carcass-cutting yields, profitability, and tenderness development for the longissimus lumborum and psoas major muscles. During a 5-wk period (May-June 2023), 10 boner cull cows (BCS 4 to 6) and 10 leaner cull cows (BCS 1 to 3) were purchased at a commercial auction market. Live conformation, carcass characteristics, weights of fabricated cuts, tenderness, pH decline, and temperature decline were recorded following slaughter. Carcasses were fabricated into the following cuts: knuckle, inside round, outside round, eye of round, strip loin, top sirloin, bottom sirloin flap, tenderloin, flank, ribeye roll, chuck tender, and brisket, whereas lean was separated into lean and fat components. Beef processor returns for boner cows were calculated as the sum of USDA Carlot Report values for the subprimal cuts, trim, bone, and drop value subtracted by actual live costs at the auction market whereas beef processor returns for leaner cows were calculated as the sum of USDA Carlot Report values for the trim, bone, and drop value subtracted by actual live costs at the auction market. Carcass and merchandizing value parameters were analyzed using a completely randomized design with a fixed effect of classification (leaner or boner) and a random effect of slaughter day. Live weight was used as a covariant for all carcass and merchandizing value parameters due to the pronounced effect of live weight for most parameters. Temperature decline, pH decline, shear force, and cooking loss parameters were analyzed using a completely randomized design with a fixed effect of classification (leaner or boner) and a random effect of slaughter day. Boner cows were found to be heavier for both live and carcass weights when compared with leaner cows. In addition, backfat thickness was 0.39 cm greater (P = 0.03), and ribeye area was 9.17 cm2 (P = 0.05) greater for boner cows compared with leaner cows. This resulted in boner cows yielding larger subprimal cuts and a greater amount of lean trim, which in turn generated more beef processor revenue. However, specific consideration should be provided for profitability as the ability to market subprimal cuts is highly dependent on muscle size, fat deposition, meat quality, and market prices for both boner and leaner cows.

Performance and Metabolic Responses of Nellore Cows Subjected to Different Supplementation Plans during Prepartum

This study assessed the effects of different prepartum supplementation plans on Nellore cows' performance, metabolic responses, and early offspring development. Thirty-nine pregnant Nellore cows (224 ± 2.67 days of pregnancy, 5.3 ± 0.29 years of age, body weight 520 ± 15.2 kg, initial body condition score 6.0 ± 0.07) were assigned to one of four treatments: a control group receiving only mineral mixture ad libitum, and three groups receiving daily protein-energy supplements of 2, 4, or 6 g/kg BW for 60 days prepartum. Weights and body condition scores were evaluated at the start of the experiment, 7 days before calving, and at 45 and 90 days postpartum. Cows supplemented with 4 and 6 g/kg BW showed improved body weight and body condition scores prepartum and postpartum and had a shorter service period (p < 0.05). The highest blood urea nitrogen concentrations were observed in cows receiving 6 g/kg BW (p = 0.0124). There was a reduction in blood urea nitrogen at calving for the 6 g/kg BW group, while the control group showed an increase (p < 0.001). Non-esterified fatty acids concentrations were lower 21 days before calving for the 4 and 6 g/kg BW groups compared to the control (p < 0.05) and decreased postpartum for all treatments (p < 0.001). No significant differences were observed in calf birth weight or performance. Supplementing with 4 g/kg BW of protein-energy is recommended to enhance metabolic health and overall performance.

Performance and metabolic evaluation in primiparous beef cows under grazing at different breeding ages

We aimed to evaluate the metabolic and performance differences in primiparous Nellore cows, which became pregnant at 14 or 24-mo old. Thirty-eight cows with 202 ± 5 days of gestation were divided into two treatments according to breeding age: 14 or 24-mo. Cows were evaluated for body weight (BW), body condition score (BCS), carcass characteristics, milk yield, calves's performance, and blood characteristics. The animals were managed in eight paddocks under continuous grazing and evaluated from 90 d before parturition until 240 d after calving. We observed an interaction between breeding age and time (P < 0.01) for cow BW. Both breeding age categories experienced BW loss during parturition, with a concurrent decrease in BCS. However, following their first calving, the BW of 24-mo cows remained stable (P > 0.05), whereas 14-mo cows exhibited a gradual recovery in BW after parturition (P < 0.05). Milk yield was greater in 24-mo animals (P < 0.01), but decreased with increasing milking days (p < 0.05) for both groups. The weight gain calves from the heifers bred at 24-mo was greater (P < 0.01), which reflected in greater BW at weaning. The beta-hydroxybutyrate (β-OHB) concentration was greater before calving and a marked decrease after parturition (P < 0.05). The 24-mo cows had greater blood β-OHB (P < 0.01) at prepartum and 30 days after calving. Blood progesterone was greater in 24-mo cows (P > 0.05). Primiparous beef cows that conceive at either 14 or 24-months of age exhibit distinct nutritional requirements and metabolic profiles. Notably, cows that conceive at 24-months of age have the advantage of weaning heavier calves and displaying a more consistent reproductive cycle following their first calving than cows that conceive at 14-months.

Comparative Analysis of mRNA and lncRNA Expression Profiles in Testicular Tissue of Sexually Immature and Sexually Mature Mongolian Horses

Testicular development and spermatogenesis are tightly regulated by both coding and non-coding genes, with mRNA and lncRNA playing crucial roles in post-transcriptional gene expression regulation. However, there are significant differences in regulatory mechanisms before and after sexual maturity. Nevertheless, the mRNAs and lncRNAs in the testes of Mongolian horses have not been systematically identified. In this study, we first identified the testicular tissues of sexually immature and sexually mature Mongolian horses at the tissue and protein levels, and comprehensively analyzed the expression profiles of mRNA and lncRNA in the testes of 1-year-old (12 months, n = 3) and 10-year-old (n = 3) Mongolian horses using RNA sequencing technology. Through gene expression analysis, we identified 16,582 mRNAs and 2128 unknown lncRNAs that are commonly expressed in both sexually immature and sexually mature Mongolian horses. Meanwhile, 9217 mRNAs (p < 0.05) and 2191 unknown lncRNAs (p < 0.05) were identified as differentially expressed between the two stages, which were further validated by real-time fluorescent quantitative PCR and analyzed using Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG). The analysis results showed that genes in the sexually immature stage were mainly enriched in terms related to cellular infrastructure, while genes in the sexually mature stage were enriched in terms associated with hormones, metabolism, and spermatogenesis. In summary, the findings of this study provide valuable resources for a deeper understanding of the molecular mechanisms underlying testicular development and spermatogenesis in Mongolian horses and offer new perspectives for future related research.

Influence of differing levels of concentrate on circulating cytokine concentrations in beef heifers

Components of the immune system (e.g., cytokines and chemokines) can influence reproductive efficiency. Characterizing the influence nutrition has on shifts in circulating cytokine concentrations will allow for a better understanding of reproductive efficiency in beef cattle. This study aimed to determine the effect of diet composition on circulating cytokine concentrations of beef heifers. Using a 3 × 3 Latin square design, pubertal Bos taurus-influenced rumen-cannulated heifers (n = 15) were fed a diet based on different concentrate percentages. The treatment period consisted of 28-d feeding periods with a washout interval of 21 d. Treatment groups were fed 100% grass hay (high forage; HF), 60% grass hay with 40% corn-based concentrate (intermediate; INT), and 25% grass hay with 75% corn-based concentrate (high grain; HG). Heifers were offered 2% of their body weight in feed daily. Blood was collected on days 0 and 28 of the treatment period for cytokine analysis. Plasma cytokine concentrations were quantified using RayBiotech Quantibody Bovine Cytokine Array Q1 kit according to manufacturer instructions. Concentrations of interferon gamma-induced protein 10 (IP10) linearly decreased with an increased concentrate diet (P = 0.037). Concentrations of IP10 differed for heifers consuming HF diet vs. HG diet (3,069.52 vs. 1,001.84 ± 669.01 pg/mL, respectively) and heifers consuming INT diet vs. HG diet (2,886.77 vs. 1,001.84 ± 669.01 pg/mL, respectively); however, there were no significant differences in IP10 concentrations between HF and INT heifers. There was a tendency for interleukin-1 family member 5 (IL1F5) concentrations to be lower for heifers consuming the HG diet compared to INT diet (P = 0.08). Results suggest that heifers consuming a high-concentrate diet have lower concentrations of IP10 and IL1F5. Additional research is necessary to better understand the dietary influence on the immune system in developing heifers.

Factors influencing pregnancy per artificial insemination (AI) and embryonic mortality in Nelore females subjected to timed-AI in Brazil

A greater understanding of factors influencing fertility is essential to improve pregnancy rates and reduce the occurrence of embryonic mortality in beef herds. The objective of the current study was to evaluate retrospective data of pregnancy per artificial insemination (P/AI) and pregnancy loss in Nelore females subjected to timed-AI (TAI) in Brazil. Data from 40,104 TAI collected from six breeding seasons (2016-2022) were analyzed, and the effects of animal category (e.g., classification based on age and parity), farm, month of parturition, sire, sire breed (Nelore vs Angus), estrus expression at TAI, animal temperament, and body condition scores (BCS) were evaluated. P/AI and pregnancy loss were affected (P < 0.001) by animal category. There was also an effect of farm (P = 0.0013) on P/AI and pregnancy loss (P = 0.001), as P/AI ranged from 49.28% and 55.58% and pregnancy loss from 3.37% to 6.89% across the herds evaluated. Month of parturition also affected (P < 0.001) P/AI and was higher for cows that became pregnant at the beginning of the previous breeding season. Calmer animals, presenting lower velocity scores while exiting the chute following TAI, achieved higher P/AI (P < 0.001). Lower BCS at TAI was associated (P < 0.001) with increased pregnancy loss, and BCS gain following AI was associated (P < 0.001) with reduced rates of embryonic mortality. There was a major effect (P < 0.001) of sire on P/AI and pregnancy loss, as P/AI ranged from 11% to 79%, and embryonic mortality from 0% to 40% for the bulls used in the study, highlighting the importance of the sire fertility on overall pregnancy success. Results from the current study reinforce the idea that animal age and parity at the beginning of the breeding season, BCS at the onset of estrous synchronization, BCS gain following AI, estrus expression at TAI, sire, and month of parturition are important factors influencing P/AI and rates of embryonic mortality in beef herds.

Genomic Predictions in Korean Hanwoo Cows: A Comparative Analysis of Genomic BLUP and Bayesian Methods for Reproductive Traits

This study aimed to predict the accuracy of genomic estimated breeding values (GEBVs) for reproductive traits in Hanwoo cows using the GBLUP, BayesB, BayesLASSO, and BayesR methods. Accuracy estimates of GEBVs for reproductive traits were derived through fivefold cross-validation, analyzing a dataset comprising 11,348 animals and employing an Illumina Bovine 50K SNP chip. GBLUP showed an accuracy of 0.26 for AFC, while BayesB, BayesLASSO, and BayesR demonstrated values of 0.28, 0.29, and 0.29, respectively. For CI, GBLUP attained an accuracy of 0.19, whereas BayesB, BayesLASSO, and BayesR scored 0.21, 0.24, and 0.25, respectively. The accuracy for GL was uniform across GBLUP, BayesB, and BayesR at 0.31, whereas BayesLASSO showed a slightly higher accuracy of 0.33. For NAIPC, GBLUP showed an accuracy of 0.24, while BayesB, BayesLASSO, and BayesR recorded 0.22, 0.27, and 0.30, respectively. The variation in genomic prediction accuracy among methods indicated Bayesian approaches slightly outperformed GBLUP. The findings suggest that Bayesian methods, notably BayesLASSO and BayesR, offer improved predictive capabilities for reproductive traits. Future research may explore more advanced genomic approaches to enhance predictive accuracy and genetic gains in Hanwoo cattle breeding programs.

Calving date as a potential predictor for the probability of approval in the first breeding soundness evaluation of Nellore bulls

Beef production systems primarily use natural service (NS) for breeding. However, a significant number of bulls used for NS are subfertile, limiting the profitability of the cow-calf operations. Therefore, producers should select bulls based on breeding soundness evolutions (BSE) to ensure higher pregnancy rates. Several factors can affect the bull ability to pass a BSE. We hypothesize that calving date would be a factor that affects the bull probability of approval at the first BSE. For this purpose, a multivariate logistic regression in a dataset of 14,737 BSEs from young Nellore bulls was used. Correlations between calving date, biometrics, and semen traits were evaluated using Pearson's correlation coefficient. Our results demonstrated that the calving date affected the probability of approval at the first BSE (p < .05). Indeed, the variable that added more information to our model was the calving date, far more than the age group of the bulls according to Akaike's information criterion. Hence, bulls born on day 0 of the calving season have 1.26 more chances to be approved at the first BSE than bulls born 21 days later. This result highlights the importance of getting the dams of future bulls pregnant as soon as possible in the breeding season. In addition, the calving season should be no longer than 47 days to achieve 80% BSE approval in 20-22 months old Nellore bulls. The strongest correlation was with SC, which decreased as the calving date increased. Therefore, the calving date may be used as a predictor of the outcome of the first BSE in young bulls. In that way, the calving date can help seedstock producers to maximize efficiency in making crucial management decisions during the breeding and calving season including nutrition, reproductive, and culling.

A multi-omics analysis identifies molecular features associated with fertility in heifers (Bos taurus)

Infertility or subfertility is a critical barrier to sustainable cattle production, including in heifers. The development of heifers that do not produce a calf within an optimum window of time is a critical factor for the profitability and sustainability of the cattle industry. In parallel, heifers are an excellent biomedical model for understanding the underlying etiology of infertility because well-nourished heifers can still be infertile, mostly because of inherent physiological and genetic causes. Using a high-density single nucleotide polymorphism (SNP) chip, we collected genotypic data, which were analyzed using an association analysis in PLINK with Fisher's exact test. We also produced quantitative transcriptome data and proteome data. Transcriptome data were analyzed using the quasi-likelihood test followed by the Wald's test, and the likelihood test and proteome data were analyzed using a generalized mixed model and Student's t-test. We identified two SNPs significantly associated with heifer fertility (rs110918927, chr12: 85648422, P = 6.7 × 10-7; and rs109366560, chr11:37666527, P = 2.6 × 10-5). We identified two genes with differential transcript abundance (eFDR ≤ 0.002) between the two groups (Fertile and Sub-Fertile): Adipocyte Plasma Membrane Associated Protein (APMAP, 1.16 greater abundance in the Fertile group) and Dynein Axonemal Intermediate Chain 7 (DNAI7, 1.23 greater abundance in the Sub-Fertile group). Our analysis revealed that the protein Alpha-ketoglutarate-dependent dioxygenase FTO was more abundant in the plasma collected from Fertile heifers relative to their Sub-Fertile counterparts (FDR < 0.05). Lastly, an integrative analysis of the three datasets identified a series of molecular features (SNPs, gene transcripts, and proteins) that discriminated 21 out of 22 heifers correctly based on their fertility category. Our multi-omics analyses confirm the complex nature of female fertility. Very importantly, our results also highlight differences in the molecular profile of heifers associated with fertility that transcend the constraints of breed-specific genetic background.

Effects of two protocols of ovulation synchronization on corpus luteum size and blood flow, progesterone concentration, and pregnancy rate in beef heifers

The objective of this study was to evaluate the effect of 7-day estradiol-progesterone-based [Treat_(C)] and 5-day Co-Synch plus progesterone [Treat_(Co-Sy)] protocols on ovulation time, pre-ovulatory follicle diameter, corpus luteum (CL) size and blood flow, progesterone (P4) concentration and pregnancy rate (PR) in beef heifers. In Experiment 1, a crossover design was applied (n = 9). For Treat_(C), a progesterone intravaginal (PI) device was inserted, plus 2 mg of estradiol benzoate (day 0). On day 7, 500 µg of cloprostenol plus 0.5 mg of estradiol cypionate were administered, and PI was removed. For Treat_(Co-Sy), on day 0, a PI was inserted plus 100 µg gonadotropin-releasing hormone (GnRH). On day 5, PI was removed, plus 500 µg of cloprostenol and 100 µg of GnRH were administered at 69-70 h later. From day one to ovulation day, dominant follicle was evaluated by ultrasonography. On days 4 and 8 post-ovulation, CL was evaluated by color Doppler, and P4 concentration was determined by chemiluminescence. In Experiment 2, a split-plot experimental design was used. Protocols followed were the same as in Experiment 1 [Treat_(C); n = 310 and Treat_(Co-Sy); n = 314]. Heifers were fixed-time artificially inseminated. Pregnancy was determined on day 41. In Experiment 1, the interval between PI removal and ovulation time was different between protocols (P < 0.01). In addition, P4 concentration was related to the CL size (P < 0.001), CL blood flow (P < 0.01) and protocols (P < 0.03). In Experiment 2, PR did not differ between protocols.

Importance of the female reproductive tract microbiome and its relationship with the uterine environment for health and productivity in cattle: A review

Once thought to be sterile, the reproductive tract microbiome has been characterized due to the transition from culture-dependent identification of bacteria to culture-independent sequencing methods. The urogenital microbiome was first identified in women through the Human Microbiome Project, which led to research in other species such as the bovine. Previous research focused on uterine bacteria associated with postpartum disease, but next generation sequencing methods identified a normal, healthy bacterial community of the reproductive tract of cows and heifers. Bacterial communities are now understood to differ between the uterus and vagina, and throughout the estrous cycle with changes in hormone dominance. In a healthy state, the bacterial communities largely interact with the uterine environment by assisting in maintaining the proper pH, providing and utilizing nutrients and metabolites, and influencing the immunological responses of the reproductive tract. If the bacterial communities become unbalanced due to an increase in potentially pathogenic bacteria, the health and fertility of the host may be affected. Although the presence of a reproductive tract microbiome has become widely accepted, the existence of a placental microbiome and in utero colonization of the fetus is still a popular debate due to conflicting study results. Currently, researchers are evaluating methods to manipulate the reproductive bacterial communities, such as diet changes and utilizing probiotics, to improve reproductive outcomes. The following review discusses the current understanding of the reproductive tract microbiome, how it differs between humans and cattle, and its relationship with the uterine environment.

What are the factors associated with pregnancy loss after timed-artificial insemination in Bos indicus cattle?

Pregnancy loss (PL) has important impacts on the profitability of livestock production systems, although it is not widely reported, particularly in Bos indicus cattle. The present study retrospectively evaluated PL after timed-artificial insemination (TAI) in Bos indicus (Nelore) beef cows corresponding to several factors, such as parity, body condition score (BCS), presence of corpus luteum (CL) at the beginning of TAI protocols, expression of estrus, and hormonal manipulations during the TAI protocol. Data from two experiments performed during three breeding seasons (BS) were reanalyzed. Both experiments evaluated adding GnRH treatment at TAI in a 7-d estradiol (E2) plus progesterone (P4)-based protocol, with intravaginal P4 implant removal on Day 7 combined with treatment with 0.5 or 1.0 mg E2 cypionate and 300 IU eCG, and TAI on Day 9. In addition, during BS 2 and 3 (Exp 2), cows were randomized to receive or not a PGF treatment on Day 0 (beginning of the TAI protocol). In all BS, presence of CL and BCS were evaluated at the beginning of TAI protocols, follicle size and expression of estrus were evaluated at TAI. The PL was assessed between the first pregnancy diagnosis (∼35d) and parturition. There were no effects of hormonal manipulations within TAI protocols of different BS on PL. There was no interaction between GnRH treatment at TAI and the other variables within BS, and there was no main effect of GnRH treatment on PL (without = 10.1% [102/1007] vs. with = 10.4% [114/1100]). The addition of PGF on Day 0 had no effect on PL (11.5% [102/886] vs. 10.5% [89/850]), as well as EC dose to induce final ovulation (10.8% [89/827] vs. 11.2% [102/909] for 0.5 and 1.0 mg, respectively). Primiparous had greater PL than multiparous cows (14.0% [77/550] vs. 8.9% [139/1557]), and cows not expressing estrus near TAI had greater PL than those expressing estrus (13.5% [57/422] vs. 9.7% [156/1617]). There was no interaction between follicle size at TAI and GnRH treatment on PL. However, probability of PL decreased linearly as follicle size at TAI increased. There were no effects of service number (first TAI or resynchronization), BCS, or presence of CL on D0 on PL. In addition, PL was not affected by sire within any of the BS. In conclusion, some factors that are known to impact pregnancy per AI also influenced PL, such as parity and expression of estrus, although, other aspects such as BCS, number of services, and presence of CL on D0 did not affect PL. Moreover, commonly implemented treatments to increase fertility (e.g., PGF on Day 0 and increasing EC dose to 1.0 mg) did not affect PL. Finally, the GnRH treatment at TAI had no effect on PL and did not interact with any of the variables, an important result, since GnRH at TAI also increases fertility in Bos indicus beef cows.

Direct and indirect nutritional factors that determine reproductive performance of heifer and primiparous cows

Pregnancy rate is a major determinant of population dynamics of wild ungulates and of productivity of livestock systems. Allocation of feeding resources, including stocking rates, prior to and during the breeding season is a crucial determinant of this vital rate. Thus, quantification of effects and interaction among multiple factors that affect pregnancy rate is essential for management and conservation of pasture-based systems. Pregnancy rate of 2982 heifers and primiparous cows was studied as a function of animal category, average daily gain during the breeding season, stocking rate, pasture type and body weight at the beginning of the breeding season. Data were obtained from 43 experiments conducted in commercial ranches and research stations in the Pampas region between 1976 and 2015. Stocking rate ranged from 200 to 464 kg live weight ha-1, which brackets values for most of the grazinglands in similar regions. Age at breeding was 14-36 months (24.6±7.5 months); initial breeding weights were 129-506 kg and 194-570 kg for heifers and primiparous cows. Pregnancy rate was modeled with an apriori set of explanatory variables where proximate variables (breed, body weight at start of breeding, weight gain during breeding and category) were included first and subsequently modeled as functions of other variables (pasture type, supplementation and stocking rate). This modeling approach allowed detection of direct and indirect effects (through nutrition and body weight) of factors that affect pregnancy rate. Bos taurus breeds (N = 1058) had higher pregnancy rate than B. Taurus x B. indicus crossbreed (N = 1924) females. Pregnancy rate of heifers and primiparous cows grazing in natural grasslands decreased with increasing stocking rate, but no effect of stocking rate was detected in cultivated and improved pastures. Pregnancy rate increased with increasing average daily gain during the breeding season. Use of cultivated or improved natural pastures promotes higher pregnancy rate, as well as allows an increase in stocking rate at the regional level. Body weight at the start of the breeding season is the primary determinant of pregnancy rates in heifer and primiparous cows.

Integration of transcriptomic and metabolomic analysis of the mechanism of dietary N-carbamoylglutamate in promoting follicle development in yaks

Yak is the main livestock in the highlands of China. The low reproductive rate of yaks is a serious constraint on their production and utility. N-carbamylglutamate (NCG) can increase arginine synthesis in mammals and has been shown to improve reproductive performance. Twelve multiparous and simutaneous anoestrous female yaks were randomly divided into two groups, one of which was fed the basal diet (Control, n = 6), and the other was fed the basal diet supplemented with NCG at 6 g/day/yak (NCG, n = 6). All yaks were slaughtered on the 32nd day (the time predicted for the selection of the last wave of dominant follicles), and their ovarian tissues were collected and follicles were classified. NCG supplementation increased the number of large ovarian follicles (diameter > 10 mm), as well as caused significant changes in the transcriptional and metabolic levels in yak ovaries which due to the differential expression of 889 genes and 94 metabolites. Integrated analysis of the transcriptomics and metabolomics data revealed that the differentially expressed genes and differential metabolites were primarily involved in the process of energy metabolism, amino acid metabolic pathways, carbohydrate metabolic pathways, and lipid metabolic pathways. The highlighted changes were associated with amino acid synthesis and metabolism, ovarian steroid hormone synthesis, the pentose phosphate pathway, and the tricarboxylic acid cycle, suggesting that NCG supplementation may promote estrogen synthesis and help regulate follicular development by altering the pathways associated with glucose catabolism. The results present important clues for understanding the mechanisms by which NCG supplementation promotes follicular development in yaks. The findings of this study provide a basis for the development and application of NCG in optimizing animal reproduction, including yak reproductive performance, which may help optimize livestock management and uplift the pastoral economy.

Backfat Thickness Does Affect the Restoration of Ovarian Activity Postpartum in Different Breeding Programs in Zebu Cattle

The backfat thickness (BFT) was used to forecast the onset of ovarian activity and predict the calf growth. Eighty Brahman cows with their calves were allocated in two groups of 40 distributed in 4 months according to the month of calving, starting in March and finishing in June. One was synchronized and inseminated at fixed time following by natural mating (TAI+NM); whilst the other only by natural mating (NM). The programs started at 60 ± 5 days postpartum and ended 60 days later. From day 30 postpartum, serial ultrasound examinations and progesterone samples were used to monitor the onset of ovarian activity. The BFT in the rump area was measured by ultrasound from 30 days postpartum and every 15 days thereafter. The weight of the calves was recorded at birth and at weaning on 160 days. The adjusted effect of BFT on ovarian activity and the calves' development was assessed by binomial logistic regression at 30, 60, 75, and 120 days postpartum. The cycling cows averaged higher BFT irrespective of breeding program (P < 0.001). Also, slower changes in BFT were recorded during the follow-up at each time for all cows. However, the former had the higher BFT values from calving to the end of the study (P < 0.001). At 60, 75, and 120 days, the BFT measured, at the preceding time, was the only factor predicting the commencement of cyclicity (P < 0.001). The accumulative pregnancy through time was higher in TAI+NM (P = 0.003). Daily weight gain and weaning weight of the calves born in March was significantly heavier (P < 0.001) than peers born in April, May, or June. The most critical element to forecast the onset of ovarian activity is the monitoring of BFT around calving regardless of the breeding program. BFT to estimate the development of the calves until weaning was unpredictable.

Animal board invited review - Beef for future: technologies for a sustainable and profitable beef industry

The global consumption, notably in developing countries, and production of beef are increasing continuously, and this requires the industry to improve performance and to reduce the environmental impact of the production chain. Since the improvement in efficiency and the highest impacts occur at farm level, it is appropriate to focus on the profitability and environmental sustainability of these enterprises. In many areas of the world, beef production is economically and socially relevant because it accounts for a significant portion of the agricultural production and represents a vital economic activity in mountain and hill districts of many regions, where few alternatives for other agricultural production exist. Due to the important role in the agricultural and food economy worldwide, the future of the beef industry is linked to the reduction of ecological impacts, mainly adopting the agroecological mitigation practices, and the simultaneous improvement of production performances and of product quality. This review analyses the technical and managerial solutions currently available to increase the efficiency of the beef industry and, at the same time, to reduce its environmental impacts in response to the growing concerns and awareness of citizens and consumers.

Meloxicam administration in the management of postoperative pain and inflammation associated with caesarean section in beef heifers: Evaluation of reproductive parameters

Post-operative pain and inflammation are normal physiological reactions to caesarean section. Their management in cattle have rarely been investigated. This surgical procedure negatively affects reproductive function with, for example, a reduction in fertility resulting in an increase in calving interval. In this multicenter clinical trial, the objective was to evaluate the impact on reproductive performance of meloxicam injected before caesarean section to manage post-operative pain and inflammation. Meloxicam is a non-steroidal anti-inflammatory drug. One hundred and twenty-seven Charolais heifers (n = 127) were recruited from 47 farms in six French veterinary practices in the Burgundy region. The heifers underwent a non-elective standardized caesarean section operation. Heifers were randomly assigned to one of two groups: meloxicam (n = 66), intravenous meloxicam injection before surgery, or control (n = 61). Reproductive performance and health information were recorded from the time of the caesarean section to the next calving or to culling. In our study, meloxicam administration before caesarean section had no effect on the incidence of retained placenta (18.2% of treated vs 25.0% of control cows, p = 0.35). The pregnancy rate was higher in treated than in control cows (83.1% vs 67.8%, p = 0.04 after multivariate analysis) and a survival analysis showed that the median calving interval was 35 days shorter in the meloxicam (t_50% = 417 days) compared to the control group (t_50% = 452 days, p = 0.05). A trend was also observed for culling rate to be lower in treated (4.7%) compared to control cows (13.3%, p = 0.09). In conclusion, this study suggests that there is a beneficial effect of meloxicam administration before caesarean section on reproductive performance in Charolais heifers.

Effect of ovulation synchronization program and season on pregnancy to timed artificial insemination in suckled beef cows

This study was conducted to (i) evaluate the requirement for the administration of GnRH coincident with insertion of a progesterone-releasing intravaginal device (PRID) and (ii) the effect of supplementing with 400 IU eCG at PRID removal on pregnancy per AI (P/AI) in spring and autumn calving suckled beef cows, subjected to a 7-d CO-Synch + PRID timed artificial insemination (TAI) program. Suckled beef cows (n = 1408) on 62 commercial farms were enrolled and randomly assigned to either of three treatments: 1) cows received a PRID and 100 μg GnRH on Day -10, followed by 25 mg PGF_2α at PRID removal (Day -3) and 100 μg GnRH 72 h later (Day 0) at TAI (Treatment 1; n: spring = 236, autumn = 248); 2) as Treatment 1, but without GnRH at PRID insertion on Day -10 (Treatment 2; n: spring = 232, autumn = 227); 3) as Treatment 1, but cows also received 400 IU eCG at PRID removal on Day -3 (Treatment 3; n: spring = 233, autumn = 232). At Day -10, ovaries were examined by ultrasonography to evaluate the presence or absence of a corpus luteum (CL) and follicle(s) ≥ 10 mm in diameter. Body condition score (BCS) was assessed on a scale of 1-5. Pregnancy diagnosis was carried out 30-35 d after TAI by transrectal ultrasonography. Data were analyzed using the GENMOD and LOGISTIC procedures of SAS. There was a treatment by season interaction for P/AI (P < 0.001). In spring, overall P/AI was 59.1% (414/701) and was affected by treatment (59.3 v 49.6 v 68.2%, for Treatments 1, 2 and 3, respectively P < 0.05). In contrast, in autumn, overall P/AI (51.5%, 364/707) was unaffected (P > 0.05) by treatment (50.1 v 53.7 v 48.7% for Treatments 1, 2 and 3, respectively). Overall, eCG had a positive effect on P/AI for cows lacking a CL at treatment initiation (P < 0.05). In addition, in cows with low BCS (≤2.25), eCG supplementation tended (P = 0.09) to improve P/AI. Seasonal differences in response to synchronization treatment may be reflective of different management regimens (grazing v confinement) and breed type and remain to be elucidated.

Using unmanned aerial vehicles to record behavioral and physiological indicators of heat stress in cattle on feedlot and pasture

Physiological and behavioral indicators of heat stress in cattle are time- and labor-intensive to measure, and difficult to observe in extensive feedlot and pasture settings. We proposed to record respiration rate and standing behavior using unmanned aerial vehicles. Videos were recorded above steers on feedlot in the morning (0830–1130) and afternoon (1400–1700) over 10 d between 25 July and 10 August and cows on pasture over 9 d between 19 and 29 August In the feedlot, video recordings on 925 individuals (264 black coated, 413 red, and 248 white) were obtained, varying in breed which included Black Angus, Hereford, Charolais, Canadian Speckle Park, and Simmental. On pasture, video recordings on 267 individuals (116 Black Angus and 151 Hereford) were obtained. Observer software was used to analyze videos. Respiration rate in feedlot cattle was the highest in black cattle, followed by red cattle, then white cattle. Coat color did not affect respiration rate in cows on pasture; temperatures on pasture were lower than in feedlots and the effect of coat color may not manifest until a certain heat load threshold. The probability that cattle would be standing increased with heat load index in feedlot and pasture settings.

Effects of feeding graded levels of black spruce needles and branches on beef cow performance and health during mid to late gestation

Pregnant beef cows (56; 727 ± 102 kg body weight) in their second trimester were used to examine black spruce (BSP) needles and branches for replacing alfalfa silage in wintering cow diets. Five dietary treatments assessed BSP inclusion rates (0%, 15%, 22.5%, 30%, and 37.5% in the diet) for 92 d up until 2 wk before start of calving using a randomized complete block design (10–12 cows per treatment). There were linear decreases (P < 0.001) in total weight gain, average daily gain, and dry matter intakes (DMI) as amounts of dietary BSP increased. Low DMI feeding BSP may be attributed to palatability issues and lower rates of digestion. Changes in body condition score increased (P < 0.003) as dietary BSP increased. These effects are supported by corresponding linear decreases (P < 0.001) for changes in rump fat cover and increases (P < 0.001) in serum non-esterified fatty acids as dietary BSP increased. After feeding the test diets, there were no dietary treatment differences (P > 0.42) for calf birth and weaning weights as well as cow pregnancy and culling rates. Based on this study, incorporation of BSP into gestating cow diets cannot be recommended.

Effects of Premating Calcium and Phosphorus Supplementation on Reproduction Efficiency of Grazing Yak Heifers

Simple Summary

This study was realized to explore the effects of calcium chloride (CaCl) and monocalcium phosphate (MCP) supplementation on the reproductive efficiency of grazing yak heifers. The body weight, serum markers of bone metabolism, and conception and calving rate of grazing yaks in control group and supplementary feeding groups were compared. The results revealed that supplementation with MCP but not CaCl could significantly improve the reproductive performance, possibly due to the improvement in body weight and bone phosphorus storage providing better estrous physiological conditions for grazing yak heifers. The findings of this study may be helpful and instructional to improve the reproductive efficiency of yaks on the Qinghai Tibet Plateau.

Abstract

Reproductive efficiency is the main factor limiting yak production on the Tibet Plateau. The purpose of this study was to investigate the effect of supplementation with calcium chloride (CaCl) and monocalcium phosphate (MCP) for 30 days before breeding on body weight (BW) change, serum bone metabolism biomarkers, conception rate, and calving rate of grazing yaks. Ninety 3 year old yak heifers (153.05 ± 6.56 kg BW) were assigned to three treatments (n = 30 per treatment): grazing without supplementation (CONT), grazing plus calcium chloride supplementation (CaCl), and grazing plus monocalcium phosphate supplementation (MCP). Compared with the CONT group, supplementation with CaCl increased the serum concentrations of osteocalcin and decreased the alkaline phosphatase (ALP) levels (p < 0.05); supplementation with MCP increased the average daily gain (ADG), serum concentrations of phosphorus (P) and osteocalcin, conception rate, and calving rate (p < 0.05), whereas it decreased the serum concentrations of hydroxyproline, ALP, and calcitonin (p < 0.05). Both CaCl and MCP supplementation had no effect on serum calcium (Ca) concentration. The ADG, conception rate, and calving rate were higher in the MCP group than in the CaCl group (p < 0.05), while the serum concentrations of hydroxyproline and calcitonin were lower (p < 0.05). It could be concluded that premating supplementation with MCP increased the body weight gain and subsequent conception and calving rate of grazing yaks. Supplementation with MCP had a positive effect on body condition and bone metabolism, thus providing a better estrous condition for grazing yak heifers, which could contribute to enhancing reproduction efficiency.

Short- and long-term effects of temporary early cow-calf separation or restricted suckling on well-being and performance in zebu cattle

Information on weaning techniques in the tropics is scarce, particularly regarding the long-term effect of temporary early cow-calf separation or restricted suckling. Therefore, we studied the effects of these two handling practices on well-being and performance at 150 days postpartum in fifteen zebu cow-calf pairs randomly assigned to three treatments. Continuous suckling (CS) where calves remained with their dams from birth to weaning; restricted suckling (RS) calves were allowed to suckle 30 min/day from Day 34 until weaning at Day 150 and kept separated the rest of the time; temporary separation (TS) calves were separated for 72 h from their dams from Day 33 to 36 but remained with their dams the rest of the time. Blood samples and behavioral data were collected on Days 32-36 (1st period) and 149-153 (2nd period). In the 1st period, a greater percentage of RS and TS calves were observed close to the fence line (<10 m) that separated them from their dams (P < 0.0001) and vocalized more than CS calves (P < 0.0001), while in the 2nd period, RS calves had the highest cortisol concentration and vocalization rate (P < 0.05). Similarly, during the 1st period, a greater percentage of RS and TS cows were observed close to the fence line than CS cows (P < 0.0001), with TS cows vocalizing the most (P = 0.001). In the 2nd period, RS cows had greater cortisol concentration than TS (P = 0.037) and CS cows (P = 0.003). More TS and CS cows than RS were observed close to the fence line (P = 0.03 and P = 0.05). On Day 150, TS calves and cows vocalized more than RS and CS animals (P < 0.0001). Before calf-cow separation, 27 out of 45 cows were cycling (CS = 10; RS = 6; TS = 11). After separation, 12 of the remaining 18 cows resumed ovarian activity (CS = 3; RS = 5; TS = 4), and all cows were cycling after estrous synchronization treatment. The pregnancy rate was similar between CS, RS, and TS (60, 53, and 60% respectively). In conclusion, temporary separation increased calf distress response to definitive weaning even four months later, while restricted suckling seemed to reduce it.

Genome-wide association study of economically important traits in Charolais and Limousin beef cows

Genomic selection has proven effective for advancing genetic gain for key profit traits in dairy cattle production systems. However, its impact to-date on genetic improvement programs for beef cattle has been less effective. Despite this, the technology is thought to be particularly useful for low heritability traits such as those associated with reproductive efficiency. The objective of this study was to identify genetic variants associated with key determinants of reproductive and overall productive efficiency in beef cows. The analysis employed a large dataset derived from the national genetic evaluation program in Ireland for two of the most predominant beef breeds, viz. Charolais (n = 5 244 cows) and Limousin (n = 7 304 cows). Single nucleotide polymorphisms (SNPs) were identified as being statistically significantly associated (adj. P < 0.05) with both reproductive and productive traits for both breed types. However, there was little across breed commonality, with only two SNPs (rs110240246 and rs110344317; adj. P < 0.05) located within the genomic regions of the LCORL and MSTN genes respectively, identified in both Charolais and Limousin populations, associated with traits including carcass weight, cull-cow weight and live-weight. Significant SNPs within the MSTN gene were also associated with both reproduction and production related traits within each breed. Finally, traits including calving difficulty, calf mortality and calving interval were associated with SNPs within genomic regions comprising genes involved in cellular growth and lipid metabolism. Genetic variants identified as associated with both important reproductive efficiency and production related traits from this study warrant further analyses for their potential incorporation into breeding programmes to support the sustainability of beef cattle production.

Effects of dietary n-3-PUFA supplementation, post-insemination plane of nutrition and pregnancy status on the endometrial transcriptome of beef heifers

Supplementation of cattle diets with n-3-polyunsaturated fatty acids (PUFA) can improve reproductive efficiency. Conversely, short-term fluctuations in feed supply can impact pregnancy establishment. The objectives of this study were to examine the effects of (1) dietary supplementation with n-3-PUFA and (2) post-insemination plane of nutrition on the endometrial transcriptome. Beef crossbred heifers were offered concentrate based diets fortified with n-3-PUFA (PUFA; n = 32) or not (CONT; n = 28) for 30 days prior to breeding at a synchronised oestrous. Following artificial insemination, heifers were allocated within treatment to either a high or low plane of nutrition. Heifers were maintained on these diets for 16 days following which endometrial tissue was harvested at slaughter for subsequent RNAseq analysis. The influence of pregnancy status on the endomentrial transcriptome, within each dietary treatment group, was also examined. Post-insemination diet affected (P < 0.05) the endometrial transcriptome. Specifically, within n-3-PUFA-supplemented heifers, genes involved in embryonic development and mTOR signalling pathways, important in pregnancy establishment, were identified as differentially expressed. Results indicate that dietary supplementation of cattle diets with n-3-PUFA may have a positive effect on the expression of key fertility-related genes and pathways, during the critical window of maternal recognition of pregnancy, particularly where animals are underfed.

The effect of clitoral stimulation post artificial insemination on pregnancy rates of multiparous Bos indicus beef cows submitted to estradiol/progesterone-based estrus synchronization protocol

Clitoral stimulation after artificial insemination (AI) in beef cattle is a common practice utilized by AI technicians; however, the effect of clitoral stimulation during fixed-time AI (TAI) is still unknown. The objective of the present experiment was to evaluate the effect of clitoral stimulation on temperament responses and pregnancy rates to TAI in Bos indicus beef cows. A total of 1,186 multiparous Nellore cows across three different locations were assigned to an estradiol/progesterone-based estrus synchronization + TAI protocol (day -11 to 0). Cows were randomly assigned to receive either 3 s of clitoral stimulation (n = 602) or no clitoral stimulation (n = 584) immediately after TAI (day 0). Cow body condition score (BCS) was recorded on day -11. Estrus expression was evaluated based on estrus detection visual aid patch activation on day 0 (estrus, ≥50% activated; no estrus, <50% activated). Temperament was assessed by individual chute score based on a 5-point scale before TAI, and individual exit velocity was measured after clitoral stimulation. Pregnancy diagnosis was performed 30 d after TAI via transrectal ultrasonography. Pregnancy rate to TAI was positively affected by BCS (P < 0.01) and estrus expression (P = 0.03). Pregnancy rates of cows receiving clitoral stimulation did not differ (P = 0.39) from cows non-stimulated (47.5 ± 4.6% vs. 44.3 ± 4.6%, respectively). No interaction of clitoral stimulation and estrus expression was observed (P = 0.26). Chute score was positively correlated to exit velocity (P < 0.01; r = 0.29); however, clitoral stimulation did not affect exit velocity (P = 0.86). In summary, pregnancy rates to TAI are influenced by various factors and multiple strategies have the potential to increase the fertility of beef cows submitted to TAI; however, clitoral stimulation of Bos indicus beef cows did not improve TAI pregnancy rate.

A negative energy balance during the peri-implantational period reduces dam IGF-1 but does not alter progesterone or pregnancy-specific protein B (PSPB) or fertility in suckled cows

The aim of this study was to evaluate the effect of a negative energy balance during the first third of gestation on metabolic, endocrine, and pregnancy recognition parameters in 2 beef cattle breeds adapted to semiextensive conditions. Seventy-five lactating Parda de Montaña and 40 Pirenaica multiparous cows rearing calves were synchronized and timed artificial inseminated (TAI) on day 76 postpartum. Cows were assigned to one of 2 diets (CONTROL or SUBNUT; 100% or 65% of their requirements supplied) until day 82 of gestation. Pregnancy was diagnosed 37 d post-TAI using ultrasound. Blood samples were obtained to determine metabolic (glucose, NEFA, β-hydroxybutyrate, cholesterol, and urea) and endocrine (IGF-1) status throughout the first third of gestation and to determine the concentrations of progesterone and pregnancy-specific protein B (PSPB) in the peri-implantational period. Undernutrition affected both cow and calf performance. The CONTROL cows maintained BCS and BW, whereas SUBNUT cows had negative daily gains. The CONTROL lactating calves had higher BW gains than SUBNUT. These negative effects were more evident in the Pirenaica breed, which was more sensitive to undernutrition. The negative energy balance was reflected in the cows' metabolic profiles, with higher NEFA values and lower IGF-1 concentrations in SUBNUT cows. However, undernutrition did not affect dam pregnancy/TAI or pregnancy recognition and maintenance, confirming that during periods of undernourishment pregnant dams prioritize the allocation of dietary energy toward reproductive functions. Progesterone concentration on day 21 post-TAI (with a 4.8 ng/mL cut-off value) and PSPB on day 26 post-TAI (with a 0.57 ng/mL cut-off value) were determined as the earliest indicators to accurately establish dam pregnancy status, regardless of breed or nutrition treatment. In summary, early undernutrition affected cow performance and metabolic profiles and impaired lactating calf growth, but did not affect progesterone or PSPB concentrations or the pregnancy/TAI rate in suckled cows.

Performance, metabolic and hormonal responses of grazing Nellore cows to an energy-protein supplementation during the pre-partum phase

BACKGROUND

Supplementation programs for prepartum beef cows are usually adopted because the nutritional status of the cows upon calving is a main factor impacting reproductive performance of the next production cycle. This study evaluated the effects of 60-d pre-partum energy-protein supplementation on performance, metabolic and hormonal responses during the peripartum phase of grazing beef cows. Thirty-eight pregnant multiparous Nellore cows were assigned to a completely randomized design with two treatments: control (no supplement) and supplementation (1.5 kg of energy-protein per d with 30% crude protein, dry matter basis).

RESULTS

The supplemented cows had higher ADG pre-partum (P < 0.10), but postpartum ADG did not differ between treatments. Supplementation did not affect BCS and calf BW upon calving, on days 45 and 90, milk yield and composition (P > 0.10). No differences were found for forage intake and neutral detergent fiber digestibility (P > 0.10). The intake and digestibility of CP and OM increased in response to supplementation (P < 0.10). An interaction occurred between supplementation and peripartum days for BUN, βHB, T3 and T4, which had higher concentrations for supplemented cows at pre-partum period (P < 0.10). Concentration of others blood parameters significantly changed along peripartum days (P < 0.10). There was no difference in pregnancy rates and days from calving to conception between treatments (P > 0.10).

CONCLUSIONS

Providing an energy and protein supplement to grazing Nellore cows over the last 60 d of gestation improved their pre-partum energy balance. However, no post-partum carryover effects were detected.

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.

Genomic Regions Associated With Gestation Length Detected Using Whole-Genome Sequence Data Differ Between Dairy and Beef Cattle

While many association studies exist that have attempted to relate genomic markers to phenotypic performance in cattle, very few have considered gestation length as a phenotype, and of those that did, none used whole genome sequence data from multiple breeds. The objective of the present study was therefore to relate imputed whole genome sequence data to estimated breeding values for gestation length using 22,566 sires (representing 2,262,706 progeny) of multiple breeds [Angus (AA), Charolais (CH), Holstein-Friesian (HF), and Limousin (LM)]. The associations were undertaken within breed using linear mixed models that accounted for genomic relatedness among sires; a separate association analysis was undertaken with all breeds analysed together but with breed included as a fixed effect in the model. Furthermore, the genome was divided into 500 kb segments and whether or not segments harboured a single nucleotide polymorphism (SNP) with a P ≤ 1 × 10^-4 common to different combinations of breeds was determined. Putative quantitative trait loci (QTL) regions associated with gestation length were detected in all breeds; significant associations with gestation length were only detected in the HF population and in the across-breed analysis of all 22,566 sires. Twenty-five SNPs were significantly associated (P ≤ 5 × 10^-8) with gestation length in the HF population. Of the 25 significant SNPs, 18 were located within three QTLs on Bos taurus autosome number (BTA) 18, six were in two QTL on BTA19, and one was located within a QTL on BTA7. The strongest association was rs381577268, a downstream variant of ZNF613 located within a QTL spanning from 58.06 to 58.19 Mb on BTA18; it accounted for 1.37% of the genetic variance in gestation length. Overall there were 11 HF animals within the edited dataset that were homozygous for the T allele at rs381577268 and these had a 3.3 day longer (P < 0.0001) estimated breeding value (EBV) for gestation length than the heterozygous animals and a 4.7 day longer (P < 0.0001) EBV for gestation length than the homozygous CC animals. The majority of the 500 kb windows harboring a SNP with a P ≤ 1 × 10^-4 were unique to a single breed and no window was shared among all four breeds for gestation length, suggesting any QTLs identified are breed-specific associations.

Evaluation of age, weaning weight, body condition score, and reproductive tract score in pre-selected beef heifers relative to reproductive potential

Background

Artificial insemination is a preferred breeding method for beef heifers as it advances the genetic background, produces a predictive and profitable calving season, and extends the heifer's reproductive life span. As reproductive efficiency in heifers is key for the success of beef cattle production systems, following artificial insemination, heifers are exposed to a bull for the remainder of the breeding season. Altogether, up to 95% of heifers might become pregnant in their first breeding season. Heifers that do not become pregnant at the end of the breeding season represent an irreparable economical loss. Additionally, heifers conceiving late in the breeding season to natural service, although acceptable, poses serious losses to producers. To minimize losses due to reproductive failure, different phenotypic parameters can be assessed and utilized as selection tools. Here, we tested the hypothesis that in a group of pre-selected heifers, records of weaning weight, age at weaning, age at artificial insemination, and age of dam differ among heifers of varied reproductive outcomes during the first breeding season.

Results

None of the parameters tested presented predictive ability to discriminate the heifers based on the response variable ('pregnant to artificial insemination', 'pregnant to natural service', 'not pregnant'). Heifers categorized with body condition score = 6 and reproductive tract score ≥ 4 had the greatest proportion of pregnancy to artificial insemination (49% and 44%, respectively). Furthermore, it was notable that heifers presenting body condition score = 6 and reproductive tract score = 5 presented the greatest pregnancy rate at end of the breeding season (89%). Heifers younger than 368 d at the start of the breeding season did not become pregnant to artificial insemination. Those young heifers had 12.5% chance to become pregnant in their first breeding season, compared to 87.5% if the heifers were older than 368 days.

Conclusion

Our results suggest that beef heifers with body condition score = 6 and reproductive tract score ≥ 4 are more likely to become pregnant to artificial insemination. Careful assessment should be undertaken when developing replacement heifers that will not reach 12 months of age by the beginning of the breeding season.

Hormones and monensin use to improve pregnancy rates in grazing lactating beef cows in the semiarid region of Argentina

The objectives of this study were 1) to determine the effect of monensin treatment, alone or combined with a hormonal estrus synchronization treatment, on the pregnancy rate of lactating beef cows, and 2) to evaluate the effect of monensin capsule administration on ruminal metabolism in steers. In experiment 1, ninety-four cows were selected from a 300 cow herd. The experimental design used was a 2 x 2 factorial with the administration of monensin capsule as first factor (M1 = with monensin vs. M0 = without monensin) and hormonal treatment as second factor (H1 = with hormonal treatment vs. H0 = no hormonal treatment). Thirty-eight days before the beginning of the breeding season, cows were randomly assigned to the first factor, and thirty days later to the second factor, resulting in four treatments: M1H0, M1H1, M0H0 and M0H1. Cow were exposed to bull (bull/cow ratio 1:20) from day 0 (day 0 = start of the breeding season and 38 days after monensin capsule administration) to day 50. Pregnancy diagnosis was performed at 30, 60 and 80 days after start breeding season by ultrasonography. In experiment 2, eight ruminally cannulated crossbred beef steers were randomly assigned to two treatments (M1 and M0). To determine proportion of volatile fatty acids (VFA), ruminal fluid samples were taken on days 0, 40 and 77 of the experimental period, at 0, 4 and 12 h after grazing. In experiment 1, treatments whit monensin did not improve pregnancy rate (P = 0.95), however, hormonal treatment resulted in grater pregnancy rates (P = 0.03). In experiment 2, the proportion of VFA in ruminal fluid of steers was significantly different between treatments. The highest proportion of propionate was found in ruminal fluid from M1 treatment at 12 h after grazing (P = 0.04). In conclusion, the treatment with monensin increased the proportion of propionate. The result might suggest that energy balance was improved in steers, without improvement in cow´s pregnancy rates. Treatment with monensin alone did not improve pregnancy rate, nor did treatment with monensin enhance the pregnancy rate when a hormonal synchronisation treatment was given. Nevertheless, the use of a hormonal treatment increased pregnancy rate, suggesting that it could be used as a suitable tool to enhance the productivity in cows with marginal body condition score.

Diet Impacts Pre-implantation Histotroph Proteomes in Beef Cattle

In ruminants, the period from fertilization to implantation is relatively prolonged, and the survival of embryos depends on uterine secretions known as histotroph. Our objective was to determine if the pre-breeding diet affected histotroph proteomes in beef cattle. Cows were assigned to one of four diets: a control diet (CON), a high-protein diet (PROT), a high-fat diet (OIL), or a high-protein and high-fat diet (PROT + OIL). After 185 days on these diets, an intravaginal progesterone implant (CIDR) was inserted for 7 days. At 9 days after CIDR removal, animals with a corpus luteum were selected ( n = 16; 4 per treatment). Proteins were isolated from the histotroph collected by uterine lavage and analyzed with liquid chromatography-tandem mass spectrometry. Over 2000 proteins were expressed ( n ≥ 3 cows per treatment), with 1239 proteins being common among all of the groups. There were 20, 37, 85, and 123 proteins unique to CON, PROT + OIL, PROT, and OIL, respectively. Relative to CON, 23, 14, and 51 proteins were differentially expressed in PROT + OIL, PROT, and OIL, respectively. Functional analysis found that 53% of histotroph proteins were categorized as extracellular exosome, 3.28% as cell-cell adhesion, and 17.4% in KEGG metabolic pathways. Differences in proteomes among treatments support the idea that pre-breeding diet affects histotroph. Understanding the impact of diet on histotroph proteins may help improve conception rates.

Resumption of ovarian function, the metabolic profile and body condition in Brahman cows (Bos indicus) is not affected by the combination of calf separation and progestogen treatment

To evaluate the effect of different calf separation procedures after a progestogen treatment on the resumption of ovarian function, body condition and metabolic profile, 59 multiparous Brahman cows grazing on a mixed grass pasture were studied. No supplementation was given at any time. Body condition score (BCS), fat thickness (FAT) and blood metabolites were measured fortnightly from the beginning of the last trimester of gestation until 96days postpartum. At 30days postpartum all animals received a progesterone (P4)-releasing device (CIDR) which was withdrawn 9days later when prostaglandin F2α was applied. At this time, treatments TW (n=28), where calves were separated from their dams for 48h; RS (n=21), calves were allowed to suckle once a day for 1h; and continuous suckling (CS; n=10). Ovarian function was assessed by blood concentrations of progesterone on days -14, -9, 10, 13, 30 and 33 after CIDR removal. At the end of the experimental period, an average of 20% of the cows had not initiated estrous cycles. There were no changes of FAT or BCS during the last trimester of pregnancy in all cows (P>0.05). During the postpartum period cows of all groups lost (P<0.05) BCS and FAT with a nadir at 60-80days postpartum, regardless of treatment. At 10days after CIDR withdrawal the percentage of cows having ovulations was 75, 61 and 80 (P>0.05) for TW, RS and CS groups. Blood metabolites follow a similar pattern in the three groups. With the conditions of the present study, the method of calf separation after a progestogen treatment, does not affect the resumption of ovarian function or metabolic profile.