Genetic correlated responses to selection for resilience in key inflammatory and stress biomarkers under heat stress of rabbits

-Geographic variation in litter size of the raccoon (Procyon lotor) is positively correlated with latitude, longitude and female body size. The positive correlation between litter size and body size for raccoons is inconsistent with interspecific patterns of litter sizebody size variation of carnivores in which litter size decreases with increasing body size. Multiple regression analysis revealed that only body size explains a significant amount of the variation in raccoon litter size. Geographic variation in litter size of raccoons occurs because there is geographic variation in female body size whereas climatic factors associated with latitude and longitude appear to influence litter size only indirectly via their effects on

ویژگی‌های محیطی یکی از عوامل مؤثر بر عملکرد گاوهای شیری می‏باشد. برای برآورد میزان تأثیر این عوامل از شاخص دما-رطوبت (THI) استفاده می‏شود. در این حوزه اطلاعات نسبتا کمی در دسترس می‌باشد. به همین منظور تأثیر تنش دما-رطوبت بر تولید شیر یک گاوداری صنعتی شهر مشهد طی هفت سال با استفاده از معادلات مربوطه مورد مطالعه قرار گرفت. همبستگی معنی‌داری بین داده‌های روزانه تولید شیر و معادلات مختلف برآورد THI در سری زمانی سالانه و فصلی (بهار، پاییز و زمستان) وجود نداشت و فقط در فصل تابستان همبستگی معنی‌دار و منفی بین تولید روزانه شیر و شاخص دما-رطوبت وجود داشت، همچنین از بین هشت معادله موجود، معادله THI4 که از روی دمای خشک و دمای نقطه شبنم به دست می‌آید، همبستگی بیشتری با داده‌های تولید شیر نشان داد. بررسی نوسانات تولید شیر و شاخص منتخب THI نشان داد حد شروع تأثیر گذاری تنش دما-رطوبت بر گاوهای این گاوداری 75 بود که به اندازه 5 واحد بیشتر از عدد ارائه شده بر اساس معیارهای جهانی است. در طی 7 سال دوره آماری مورد بررسی در مجموع نسبت به حالت بدون تنش حدودا 401 تن کاهش تولید شیر برای این گاوداری برآورد گردید که بیشترین مقدار مربوط به سال 1392 و کمترین مقدار مربوط به سال 1387 بود. افزایش درجه حرارت و رطوبت در فصل تابستان از علل اصلی ایجاد این تنش است و خروج از شرایط بهینه محیطی تنها در این فصل در حیوان تنش ایجاد کرده و باعث کاهش تولید شیر شده است.

We examined the effects of maternal age and parity on litter size in 2 populations of white-footed mice (Peromyscus leucopus) in southwestern Ontario, Canada, to determine whether these factors cause seasonal variation in litter size. Litter size increased from 1st to subsequent litters among females that bred for the 1st time in their natal year, but not among females that 1st bred as overwintered adults. Thus, prior reproductive experience was not an important determinant of litter size. Maternal age accounted for approximately 70% of the variance in litter size; mean litter size was greatest among females between 150 and 250 days of age at parturition. Date of birth explained 79% of the variation in mean litter size, with litters born in summer significantly smaller than those born in spring or autumn. This effect was attributed to the fact that most summer litters were produced by primiparous young-of-the-year females. Although litter size declined among old, multiparous females, few individuals survived to the age at which reproductive senescence was apparent. Thus, reproductive senescence plays a minor role in population-wide variation in litter size.

BackgroundEnvironmental variance (VE) is partly under genetic control and has recently been proposed as a measure of resilience. Unravelling the genetic background of the VE of complex traits could help to improve resilience of livestock and stabilize their production across farming systems. The objective of this study was to identify genes and functional mutations associated with variation in VE of litter size (LS) in rabbits. To achieve this, we combined the results of a genome-wide association study (GWAS) and a whole-genome sequencing (WGS) analysis using data from two divergently selected rabbit lines for high and low VE of LS. These lines differ in terms of biomarkers of immune response and mortality. Moreover, rabbits with a lower VE of LS were found to be more resilient to infections than animals with a higher VE of LS.ResultsBy using two GWAS approaches (single-marker regression and Bayesian multiple-marker regression), we identified four genomic regions associated with VE of LS, on chromosomes 3, 7, 10, and 14. We detected 38 genes in the associated genomic regions and, using WGS, we identified 129 variants in the splicing, UTR, and coding (missense and frameshift effects) regions of 16 of these 38 genes. These genes were related to the immune system, the development of sensory structures, and stress responses. All of these variants (except one) segregated in one of the rabbit lines and were absent (n = 91) or fixed in the other one (n = 37). The fixed variants were in the HDAC9, ITGB8, MIS18A, ENSOCUG00000021276 and URB1 genes. We also identified a 1-bp deletion in the 3′UTR region of the HUNK gene that was fixed in the low VE line and absent in the high VE line.ConclusionsThis is the first study that combines GWAS and WGS analyses to study the genetic basis of VE. The new candidate genes and functional mutations identified in this study suggest that the VE of LS is under the control of functions related to the immune system, stress response, and the nervous system. These findings could also explain differences in resilience between rabbits with homogeneous and heterogeneous VE of litter size.

It has been known that, weather condition has a great effect on living being. Now a days the study of the effect of weather conditions on plant, animals and all living being is considered as an interdisciplinary science, which has a great effect on the quality and quantity of living being productions. In order to survive and maintain their physiological activities, warm-blooded animals’ body temperature should be in a specific rang. Therefor in warm days, in order to restrain their body temperature in an optimized rage, their transpiration, breathing and heart beat will raise, while the feeding rate decrease. In these situation if the relative humidity was high too, these cooling reaction cannot response well and therefore animals’ body temperature will raise, and it has been said that animals are under the heat stress. As a consequence of that feeding rate and animal production reduce, reproductive problems accrues, and the rate of getting sick raise. In this regard, researches show that air temperature and environmental humidity are two parameters which has a great effect on cows’ heat stress. In order to evaluate and assess the heat stress, most of the researchers use Temperature Humidity Index (THI). There are numbers of equation to obtain THI, and also their coefficient must be calibrated for every different regions, therefore using them, are sometimes, confusing. Therefore the aim of this study is determining the best THI equation for dairy industry in Mashhad, and also finding the reduction in milk production during the heat stress period. The meteorological data (daily wet and dry bulb and relative humidity records) were obtained from Iran meteorological organization. Then by using 8 common equations, temperature humidity index (THI) were calculated for 7 year period (2007-2013). The daily milk production data was also obtained from improvement center of milk production in Karaj. Then the relationship between daily milk production and 8 obtained THI were calculated for annual and seasonal time scale. At that point by using the correlation coefficients and P-value the best equation to determine THI was chosen. Finding the best THI equation for the study area, led to find a warning heat stress point. As a final point, daily milk production during the heat stress calculated and reduced milk production was estimated during the heat stress time. The results show that there are no significant correlation between annually milk production and obtained THI. Also the relationship between THI and milk production in seasonal scale (spring, fall and winter) were not significant to. Nevertheless, only daily milk production in summer has a significant relationship with temperature-humidity index, which was negative. Which means that daily milk production decreases with increasing THI. Among from 8 investigative equation, the forth equation (which calculate THI by using dry bulb and dew point temperature) has the best correlation coefficient and P-value with daily milk production. By definition the break point in summer daily THI and milk production, the heat stress warning point for Mashhad dairy industry was found. The results show that when temperature-humidity index raise above 75, the milk production significantly decrease. In order to calculate the amount of milk reduction as a result of THI increasing, the relationship between milk production and THIs’ more than 75 was estimated. Then by subtracting the calculated THI from average milk production in a non-stress day, the loss of milk production were calculated for each cow. Then by multiplying one cow milk lost, by the number of cows, the final milk production loss were calculated for each year. The results show in 2013, the temperature humidity stress had a greatest effect on milk production, so that during a summer time, each cow averagely produce 138.8 lit milk less than usual. This amount is also equal to 1.5 lit milk per a day. During 7 years period investigation, the total milk loss was calculated 401 ton. In conclusion, raising air temperature can cause a heat stress and a reduced milk reduction. When the heat comes with high relative humidity, these effects highlighted and cows were under enormous stress therefore their body temperature transpiration, breathing and heart beat raise, while the feeding rate decrease, and as a result of that milk production reduced which can cause a great damage in diary industry

This study evaluated genetic parameters for test-day egg production in four Thai native synthetic chicken lines-Soi Nin, Soi Pet, Kaen Thong, and Kaimook e-san-under heat stress in Thailand. A total of 11,887 monthly test-day egg records from 1134 hens, collected between January 2023 and July 2025, were analyzed using a repeatability test-day model with the temperature-humidity index (THI) as an environmental covariate. THI thresholds from 70 to 80 were evaluated, and the THI1 equation provided the best model fit with the highest coefficient of determination (R2) and the lowest mean squared error (MSE). With increasing THI, heritability estimates declined from 0.255-0.323 at THI 70 to 0.173-0.236 at THI 80, a 26.9-32.2% decrease reflecting reduced additive genetic variance and consequent lower genetic expression under heat stress. Genetic correlations between egg production and heat stress were positive at low THI (0.250-0.600) but became negative at THI ≥ 73, suggesting antagonism between productivity and thermotolerance under severe stress. The rate of decline in egg production increased with increasing THI, from -0.35 to -0.45 eggs/bird/THI at THI 73, -0.80 to -1.22 at THI 76, and -1.76 to -2.35 at THI 80. The ranges of heritability and decline rates reflect the variation observed among the four Thai native synthetic chicken lines examined in this study. Kaimook e-san consistently showed the steepest decline in egg production, whereas Soi Nin exhibited the smallest, indicating greater resilience. These findings reveal significant genetic variation in heat tolerance among Thai native synthetic lines and underscore the need to consider both productivity and environmental sensitivity in breeding programs to sustain egg production under future climate change.

This study characterized the environmental–climatic trends occurring in the largest dairy cattle intensive production cluster under arid land conditions in northern Mexico. The study was based on the Temperature Humidity Index (THI); it aimed to identify the number of days with THI values ≥68 as a bio-marker of heat stress (HS) and evaluate the possible HS effect upon the milk production of dairy cows. Climate data were obtained every 10 min in five farms across years (i.e., 2015–2020). THI was divided into four HS subclasses, 68–71, 72–76, 77–79, and ≥80, according to the circadian HS occurrence (i.e., 1, 4, 8, 12, 16, 20, 24 h), and analyzed across seasons–years. Thus, a total of 1,475,319 THI across different time-scale subclasses was analyzed. The observed results supported our working hypothesis in that yearling-average periods with more than 300 d, HS was confirmed. A yearly average of 31.2 d with THI ≥ 80 with similar (p > 0.05) trends across dairy farms and a slight annual variation (p < 0.05) were also witnessed. Moreover, the highest days with THI levels ≥68 occurred in summer and autumn (p < 0.05), while the in the subclasses 68–71, 72–76, and 77–79, THI occurred in any hour-scale subclass (i.e., 1, 4, 8, and 12 h). Furthermore, a trend to observe THI-HS increases either among years or within an hour-scale basis were also observed. On average, HS engendered a reduction of up to 11.8% in milk production. These research outcomes highlight the need to identify and quantify the negative impacts that HS may generate at a productive and reproductive level in order to delineate mitigation strategies that may lessen the environmental impact upon the dairy cattle industry.

Temperature increases due to climate change induce heat stress in livestock, resulting in economic losses for farmers. This study investigated the physiological responses of Hanwoo cattle to heat stress, and the effects of heat stress on the vaginal microbiome. Four cows (mean weight: 380.3 ± 37.5 kg, parity: 2.5 ± 1.0) were allocated to two groups: heat stress (temperature-humidity index (THI) 86: 33 °C, 70% humidity) and no heat stress (THI 67: 20 °C, 60% humidity). The cows were exposed to these conditions for 15 days, and the study was repeated twice with the same cohort of animals, ensuring that each cow was exposed to both thermal conditions in a crossover manner. The study revealed that feed intake was lower, while water intake, rumen temperature, rectal temperature, and respiration rate were higher in THI 86 than in THI 67 cows. The blood cortisol, glucose, and cholesterol concentrations, and the inverse Simpson index of the vaginal microbiome, were lower in THI 86 cows, while certain microorganisms (for example, Tenericutes) were more abundant in THI 86 than in THI 67 cows. The increase in blood oestradiol concentration during oestrus was 2.8× lower, and the duration of oestrus was shorter by 41 hours in the THI 86 than in the THI 67 cows. Blood progesterone concentrations increased after ovulation in THI 67 cows and during oestrus in THI 86 cows. In THI 86 cows, the increase in blood luteinising hormone secretion and ovulation were delayed by 10 hours and 11 hours, respectively. We concluded that heat stress raises the body temperature of Hanwoo cows, causes changes in endocrine hormones and metabolic physiology, reduces the microbial diversity in the vagina, and negatively affects the oestrus cycle.

Summary The influence of age at conception, number of matings per conception, season of conception, and breed of female on parity-1 litter size was investigated in 4,944 females from 5 commercial swine herds located in North America. The influence of age at conception on reproductive performance of females in subsequent parities also was investigated. As the age at conception increased from 180 to 245 days, litter size increased 0.017 and 0.012 pig per day, respectively, (P<0.05) in 2 of the 3 herds that recorded such data. Age at conception did not influence litter size when conception occurred after 245 days of age. Longevity (parity achieved before death or culling) of females was not influenced by age at first conception. Gilts that conceived before 220 days of age had significantly shorter weaning-to-conception intervals in one herd and shorter farrowing-to-conception intervals in another herd throughout subsequent parities. In 1 of 3 herds that recorded such data, live and total litter size increased from 9.46 to 10.46 and 10.16 to 11.50, respectively (P<0.05), as number of matings increased from 1 to 3 per conception. No significant influence of number of matings per conception was observed in the other 2 herds. The effect of season of conception was variable among herds. In 2 herds, there was no significant effect of season of conception on subsequent litter size. In 2 herds, conception during December, January, February, and March was associated with a 0.5-pig reduction (P<0.05) in subsequent live litter size, whereas, in one herd, conception during June, July, August, and September was associated with a 0.5-pig reduction (P<0.05) in litter size. The 2 herds with Landrace × Large White F1 females were found to produce the largest mean live and total litter sizes (P<0.01) at first parity. Age at conception, number of matings per conception, season of conception, and breed were associated with variation in parity-1 litter size, but the associations varied among herds. No evidence of interaction of the variables that influenced parity-1 litter size was found. The amount of variation in litter size, explained by a model using main effects of all these variables, was small (the maximum R2 in any herd was <0.025) but significant (P<0.05) in each herd.

Climate sensitivity of milk production traits and milk fatty acids in genotyped Holstein dairy cows

Callitrichids are unusual among anthropoid primates in that they can deliver one to four offspring per litter in captivity. Factors underlying intraspecific variation in litter size are unclear. Data from the Oak Ridge Associated Universities (ORAU) Marmoset Research Center provided an opportunity to investigate determinants of variation in (1) average litter size at birth and (2) average litter size surviving to 2 weeks of age in Saguinus fuscicollis, S. oedipus, and Callithrix jacchus. The objectives were to (1) investigate the impact of parity, husbandry, origin (wild or captive), and subspecific hybridization on phenotypic variance in litter size and (2) to estimate the heritability of litter size at birth and at 14 days. Husbandry changes were the only significant covariate and increased litter size at birth in C. jacchus only. Heritability estimates for average litter size at birth were significant only in S. fuscicollis (h2 = 0.306). Heritability of average litter size at 2 weeks of age was not significantly greater than zero. Estimates of genetic variability were relatively high, however both traits had very high levels of residual variance. The results suggest that litter size is a malleable trait that may respond to environmental factors.

A previous systematic review has shown associations between exposure to high temperatures and negative birth outcomes. To date, a scoping review for heat indices and their use to measure effects...

Because many species of diprotodont marsupials (including all large ones) have litters of a single young, it seems to be assumed tacitly that there is little variation in litter size within and between species in this group. In contrast, polyprotodont marsupials have litters that are typically larger; variation in litter size between species is related to body size, diet, and ecology; and intraspecific variation in litter size also occurs. The largest litters in diprotodont marsupials are found in the small possums (eight species from the families Burramyidae, Acrobatidae, and Tarsipedidae), but there also is variation in litter size beyond that which can be explained by body size, reflecting a fast-slow continuum among small possums. There also are geographical differences in litter size within some species. Number of teats varies among species and also varies within three of the species. Production of supernumerary young occurs in some species such that number of teats effectively limits litter size. In other species, number of young at birth is smaller than number of teats, so litter size is limited by number of eggs shed at ovulation and embryos carried in utero. The largest mean litter sizes are found in species that produce supernumerary young, and these are the fast species among small possums.

Summer heat stress (HS) is associated with a reduction in conception rate, increase in services per conception, and early embryonic death. However, the impact of summer HS on the thermal environment of different regions of the bovine female genital tract remains unknown. This study aimed to elucidate the effect of summer HS on the thermal environment of different regions of the genital tract in the cow. Three non-pregnant Japanese Black cows were investigated using a specially designed digital thermometer to record the temperatures of the rectum (RT), vagina (VT), cervix (CT), uterine body (UBT), and uterine horns (UHT) on days 0, 1, 2, 3, and 8 of the estrous cycle (day 0 = heat) in February (winter), May (spring), and August (summer). During the experiment, the temperature humidity index (THI) was recorded. THI during summer was higher (P˂0.001) than in winter and spring (78.45 ± 0.32 vs. 60.26 ± 1.20 and 68.51 ± 0.80, respectively) and was higher than the alert THI indicating HS (i.e., THI > 73). Consequently, the VT, CT, UBT, and UHT were elevated during summer HS (P < 0.05) in comparison to winter and spring. THI was positively correlated (P < 0.01) with RT, VT, CT, UBT, and UHT. Linear regression revealed that VT, CT, UBT, and UHT increased by 0.05°C per unit of THI. VT was more highly correlated than RT with THI and with the temperature of other regions of genital tract. HS induced increases in the temperatures of different regions of the female genital tract. The relationship between THI and VT could be incorporated into a mathematical model to predict the thermal load of HS on different regions of the female genital tract.

The present study aimed to identify the novel mechanisms regulating rabbit fecundity. For this purpose, the association between litter size variability, fecundity, ovarian morphology, and markers of proliferation, apoptosis, steroidogenesis, and the presence of regulatory proteins were examined in ovarian cells from two rabbit lines divergently selected for low (LL) and high (HL) variability in litter size throughout sixteen generations. Ovaries and uteri were isolated from multiparous non-lactating female rabbits from each line at sixteen generations of selection. One part of the ovary was subjected to histomorphometric analysis of folliculogenesis. From the rest of ovary, ovarian granulosa cells (OGCs) were isolated, cultured, and cell viability, proliferation (accumulation of PCNA and of cyclin B1, and BrdU-positive cells), and apoptosis (accumulation of caspase 3, bax and DNA fragmentation) were evaluated by the Trypan blue exclusion test and BrdU, quantitative immunocytochemistry, and cell death detection assays. Furthermore, OGCs were subjected to proteomic analysis by using the nano HPLC-Chip-MS/MS method. The release of progesterone and oestradiol was measured by ELISA. The LL had more than one kit per litter than the HL (7.6 kits vs. 6.5 kits, p ≤ 0.05). No differences were found in the diameter of primordial and primary ovarian follicles, theca, and granulosa thickness, but the diameter of oocytes in the primary and secondary follicles was higher in the LL than in the HL (88.49 µm in the LL vs. 77.86 µm in the HL for oocytes of primary follicles, p ≤ 0.05; 122.10 µm in the LL vs. 109.87 µm in the HL for oocytes of secondary follicles, p ≤ 0.05). Preovulatory follicles were presented only in the ovaries of the LL. The LL had higher incorporation of BrdU and reduced accumulation of bax within OGCs (0.92% in the LL vs. 0.44% in the HL for incorporation of BrdU, p ≤ 0.05; 41% in the LL vs. 48% in the HL for accumulation of bax, p ≤ 0.05). Ovarian fragments from the LL produced less progesterone and oestradiol than those of the HL (12 ng/mg tissue/day in the LL vs, 45 ng/mg tissue/day in the HL for progesterone, p ≤ 0.05; 11 ng/mg tissue/day in the LL vs. 30 ng/mg tissue/day in the HL for oestradiol, p ≤ 0.05). Besides, the OGCs from the LL produced a higher number of specific regulatory proteins involved in cell differentiation, proliferation, and adhesion than the HL (50 vs 38, p ≤ 0.05). In conclusion, higher prolificacy in the LL line would be caused by: (1) the selection of growing primordial ovarian follicles; (2) better transformation to preovulatory follicles; (3) increased cytoplasmic maturation of oocytes; (4) increased DNA synthesis and decreased cytoplasmic apoptosis in OGCs; (5) changes in ovarian steroidogenesis; and (6) changes in the number of peptides involved in cell differentiation, proliferation, and adhesion. HIGHLIGHTS Assessing fecundity in two divergently rabbit lines for variability in litter size. Fecundity and its variability are related to the diameter and quality of oocytes. Selection and better growth of preovulatory follicles have been related to fecundity.