- Background: The effect of heat stress on livestock production is a worldwide issue. - 1 Key Laboratory of Animal Genetics, Breeding and Reproduction, MARA, National Engineering Laboratory of Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing 100193, China Full list of author information is available at the end of the article. - Lastly, the candidate genes identified to be linked with response to heat stress provide a better understanding of the underlying biological mechanisms of heat tolerance in dairy cattle.. - Stud- ies of the North American Holstein population have shown that heat conditions can lead to 165 kg loss of milk yield annually and 0.4% reduction in milk fat per- centage kg decrease in feed intake with one unit increase in air temperature [13], and about 15% de- crease in conception rate when THI surpasses 72 [14].. - The average daily THI in many regions of the world exceed 72 throughout most summer period days, indi- cating that dairy cattle located in these regions may suf- fer from mild to severe heat stress [15]. - In this case, simply using the daily average of THI may lead to the underestimation of the impact of heat stress. - In addition to the timing of the day, for dairy cows, the time of its reproductive period may also influence the response to heat stress. - Several studies have demon- strated that the conception rate of dairy cows decreased when they experienced heat stress before and after in- semination [16–18], which highlights the role of the crit- ical period of exposure to heat conditions. - The relationship matrix of the RNM can be structured either by pedigree and using the pedigree-based Best Linear Unbiased Pre- diction (BLUP), or by combining both pedigree and gen- omic information and using the single-step genomic BLUP (ssGBLUP) method [19, 20]. - Markers related to the intercept and slope of the reaction norms can be mapped by applying ssGWAS procedures.. - 2) the minimum THI for each day of the candidate period (mTHI-EG).. - To avoid the underestimation of the heat stress effect, the days in which the hourly THI was higher than 72 for six continuous hours were considered as heat-stress days for prop-EG. - The detailed results of the AIC values for the 19 tested combinations are presented in Supp. - When using the H matrix (hybrid pedigree-genomic relationship matrix), approximately 75% of the heifers were the same in both scenarios for AFC and IFL, but relatively low (29.63. - The pattern of the heritability curves were similar when using different relationship matrices but differed across EGs. - 20) or heat-stress environments (mTHI-EG >. - However, the patterns were flatter when prop-EG was used, and the highest heritabilities only appeared in heat stress conditions. - As shown in Table 4, the variance of the slope for all traits was significantly different from zero based on a one-tailed test (P <. - Among the top sires with more than 20 daughters with phenotypes, the number of sires overlapping across the two EGs, reflecting the magnitude of the re-ranking of sires, are listed in Table 5. - In this case, sires that are sensitive to the environ- ments (blue lines), would perform worse than those with flat slopes (red lines) under heat stress conditions. - Meanwhile, the gEBVs of the red lines were stable along the whole prop-EG (Fig. - Similarly, the same region (from to bp), which is one of the four shared genomic win- dows, explained 1.12 and 0.91% genetic variance for the intercept and slope of IFL, respectively. - How- ever, the genomic region from to bp that explained the highest proportion of the total additive genetic variance (2.38 and 2.29% for the inter- cept and slope, respectively) for CR, was still located in BTA14. - Prop-EG AFC S1 60. - a prop-EG The number of days that exceeded the threshold temperature humidity index in the period, mTHI-EG Minimum temperature-humidity index for each day of the period. - More shared genomic regions were detected when the same variables (the intercept or slope) of the two scenar- ios were tested. - For AFC and IFL, more than 10 genomic areas were connected, although they did not explain the largest amount of the total additive genetic variance.. - Candidate genomic re- gions of the intercept term were previously linked to several types of quantitative trait loci (QTL) such as milk kappa-casein percentage, metabolic body weight, average daily gain, length of productive life, dry-matter intake, conception rate, and pregnancy rate (Supp. - Most of the mapped QTLs are associated with pro- duction traits, and the rest are associated with reproduction, health, and meat/carcass traits. - b prop-EG using the number of days that exceeding the threshold temperature humidity index in the period as EG, mTHI-EG using the minimum temperature humidity index of a day of the critical period as EG. - Table 4 Variances of the intercept ( σ 2 a 0 ) and slope ( σ 2 a 1. - Prop-EG AFC S . - a prop-EG the number of days that exceeding the threshold temperature humidity index in the period, mTHI-EG Minimum temperature humidity index for each day of the period. - The color indicates the magnitude of the genetic correlation. - a prop-EG the number of days that exceeding the threshold temperature humidity index in the period, mTHI-EG minimum temperature humidity index for each day of the period. - Candidate genomic regions of the slope term have been previously linked to a variety of trait groups, in- cluding luteal activity, body weight, stillbirth, and many milk-related QTLs. - Similarly, most of the QTLs identified were associated with milk production traits as most of the QTLs overlapped between the two genetic terms. - 5 Percentage of the intercept and slope genetic variances explained by a sliding window of 20 SNPs for three fertility traits, which were estimated under scenario one of prop-EG. - 6 Percentages of the intercept and slope genetic variances explained by a sliding window of 20 SNPs for three traits, which were estimated under scenario two of prop-EG. - and in the same Chinese Holstein populations [4]. - Sakatani et al. - Khan et al. - A study evaluating the whole cycle of estrus showed that heat stress inhibits the develop- ment of the dominant follicle during preovulatory period in heifers [27]. - boundary of the critical periods for AFC and IFL was found to be 90 days (3 months) before the first insemin- ation. - Amundson et al. - negatively affected by heat stress in both before and after the day of insemination. - Li et al. - The results of the current research indicated that the critical period of heat stress is trait-related, and the periods we identified for CR are within the range reported in previous studies, which pro- vides substantial support for the results of AFC and IFL.. - The overlapping test of the two EGs under two scenar- ios (Table 3) indicated that prop-EG and mTHI-EG cap- ture different mechanisms. - it repre- sents the average heat load of heifers, i.e., the proportion. - Zhang et al. - C2 = SNP effects changes in the opposite ways (increase for AFC and IFL. - Based on the t-test for the variance of the slope, a sta- tistically significant G × E was observed for all traits in this study [5]. - As mentioned in the previous sec- tion, heat stress has adverse effects on follicular develop- ment, which is directly associated with conception.. - 1%) proportion of the total additive genetic variance, in- dicating that fertility and heat tolerance are largely poly- genic traits. - However, the functional analysis confirmed that the fertility traits are influenced by heat stress. - For example, some of the genomic regions were previously reported to be associated with pathways such as re- sponse to abiotic stimulus, detection of stimulus in- volved in sensory perception, response to temperature stimulus, response to radiation, negative regulation of saliva secretion, and aerobic respiration and energy.. - Ilha et al. - White et al. - Most of the QTLs over- lapped when using different EGs, and many were located in BTA14. - Costa et al. - Mota et al. - Most of the QTLs were shared by the intercept and slope, which is consistent. - As for CR, half of the periods overlapped in S1. - SNP effects of the slope ranged from 9.48e-9 to 1.47E-11 for all traits. - Thus, candidate genes that play an important role in SNP effect changes (C1 and C2) are the priority of the current research.. - Sakurai et al.. - NR5A2 was mapped in C1, and it has been reported to affected ste- roidogenic pathways of progesterone production during the luteal phase of the estrous cycle in cattle [65].. - The results indicated that EGFR could be involved in the regulation of the bovine oviductal microenvironment, but these regulatory mech- anisms may be compromised in the presence of heat stress. - This indicates that the interaction between GUCY1B and HSP90 in cattle may be related to the heat stress response.. - We analyzed the impact of heat stress on dairy cattle based on three fertility traits. - Thus, linear models were used for all fertility traits in the current study. - The matrix A was constructed using pedigree data only for conventional BLUP, whereas for the ssGBLUP models, the inverse of the H matrix (H − 1. - G was built using (1 − ω)G 0 + ωA 22 , where ω is the as- sumed weight of the genetic variance not captured by markers and was set to 0.05 according in previous stud- ies [7, 78]. - For each trait, two critical periods (S1 and S2) were chosen under each EG (prop-EG and mTHI-EG) to estimate the (co) variance components of the RNMs.. - The relationships of the two EG schemes were also evaluated by calculating the equivalent values: the proportion of days exceeding threshold THI when the average minimum THI of this period at a certain level. - G × E exists if the variance of the slope was significantly different from zero by using a one-tailed t-test with the significance level of . - Single-step genome-wide association study (ssGWAS) The marker effects of the intercept and the slope for all traits were estimated using the ssGWAS method pro- posed by Wang et al. - mTHI: Minimum THI for each day of the candidate period;. - Percentages of the intercept and slope genetic variances explained by a sliding window of 20 SNPs for three traits, which were estimated under scenario one of mTHI-EG.. - Percentages of the intercept and slope genetic variances explained by a sliding window of 20 SNPs for three traits, which were estimated under scenario two of mTHI-EG.. - breeding research team members who participated in the sample collection and provided helpful suggestions during discussion of the results.. - The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.. - Temperature-humidity indices as indicators of Milk production losses due to heat stress. - Heat stress interaction with shade and cooling. - Genetic component of heat stress in dairy cattle, development of heat index function. - Dairy cow reproduction under the influence of heat stress. - Effect of heat stress on pregnancy rates of crossbred dairy cattle in Terai region of Uttarakhand, India. - Impact of heat stress on conception rate of dairy cows in the moderate climate considering different temperature – humidity index thresholds, periods relative to breeding, and heat load indices. - Effects of heat stress on body. - temperature, milk production, and reproduction in dairy cows: a novel idea for monitoring and evaluation of heat stress — a review. - Effects of Controlled Heat Stress on Ovarian Function of Dairy Cattle. - Bayesian analysis of the linear reaction norm model with unknown covariates1. - Investigation of the association of two candidate genes (H-FABP and PSMC1) with growth and carcass traits in Qinchuan beef cattle from China. - Functional characterization of genetic polymorphisms identified in the promoter region of the bovine PEPS gene. - Involvement of the Orexin system in adrenal sympathetic regulation.. - Genetic association of the ACACB gene with milk yield and composition traits in dairy cattle. - The expression of the nuclear receptors NR5A1 and NR5A2 and transcription factor GATA6 correlates with steroidogenic gene expression in the bovine corpus luteum. - Expression of the erbB/HER receptor family in the bovine uterus during the sexual cycle and the relation of this family to serum sex steroids. - Effect of epidermal growth factor (EGF) on the phosphorylation of mitogen-activated protein kinase (MAPK) in the bovine oviduct in vitro: alteration by heat stress. - Evaluation of heat stress effects on cellular and transcriptional adaptation of bovine granulosa cells
Xem thử không khả dụng, vui lòng xem tại trang nguồn hoặc xem
Tóm tắt