Temporal effect of maternal heat stress during gestation on the fertility and anti-Müllerian hormone concentration of offspring in bovine

Developmental programming of production and reproduction in dairy cows: V. Association of the main and interactive effects of maternal level of milk production and milk fat to protein ratio with offspring's birth weight, survival, and productive and reproductive performance from birth to the first lactation period

Level of dam milk production (DMP) and dam milk fat to protein ratio (DFPR), as an indicator of metabolic status in dairy cows, have been identified to be associated with productive and reproductive performance of the offspring. Yet whether the interaction of DMP by DFPR can be associated with performance of the offspring have not been studied to our knowledge. Therefore, the present study was conducted to investigate the association of the main and interactive effects of DMP and DFPR with offspring's birth weight, survival, milk yield and fertility. To this end, data of birth weight, culling rate, milk yield and reproductive variables of offspring born to lactating dams (n = 14,582) and data associated with DMP and DFPR during 305-day lactation were retrieved. Afterwards, offspring were classified in three categories of DMP, including DMP1 (dams with <10.00 × 103 kg of 305-day milk production), DMP2 (dams with ≥10.00 × 103 kg and <14.00 × 103 kg of 305-day milk production), DMP3 (dams with ≥14.00 × 103 kg of 305-day milk production), and three categories of DFPR, including DFPR1 (offspring born to dams with <1.00 FPR), DFPR2 (offspring born to dams with ≥1.00 and < 1.40 FPR) and DFPR3 (offspring born to dams with ≥1.40 FPR). Statistical analysis revealed no association of the interaction effect of DMP by DFPR with investigated variables in the offspring (P > 0.05). However, the main effect of DMP was positively associated with milk yield, but negatively associated with survival, age at first insemination and conception during nulliparity, and transgenerational improvement in milk yield in the offspring (P < 0.05). Moreover, the main effect of DFPR was positively associated with birth weight, survival and first service conception rate during nulliparity, but negatively associated with metabolic status and reproductive performance during primiparity in the offspring (P < 0.05). In conclusion, the present study did not find any interaction effect of DMP by DFPR on productive and reproductive variables in the offspring. This finding implicates the association of DMP with milk production in the offspring was regardless of DFPR. Moreover, this finding implies the association of DFPR with postpartum metabolic status and reproductive performance in the offspring was regardless of DMP.

Functional transcriptome analysis revealed upregulation of MAPK-SMAD signalling pathways in chronic heat stress in crossbred cattle

Animal geneticists and breeders have the impending challenge of enhancing the resilience of Indian livestock to heat stress through better selection strategies. Climate change's impact on livestock is more intense in tropical countries like India where dairy cattle crossbreeds are more sensitive to heat stress. The main reason for this study was to find the missing relative changes in transcript levels in thermo-neutral and heat stress conditions in crossbred cattle through whole-transcriptome analysis of RNA-Seq data. Differentially expressed genes (DEGs) identified based on the minimum log twofold change value and false discovery rate 0.05 revealed 468 up-regulated genes and 2273 down-regulated significant genes. Functional annotation and pathway analysis of these significant DEGs were compared based on Gene Ontology (Biological process), Kyoto Encyclopedia of Genes and Genome (KEGG), and Reactome pathways using g: Profiler, ShinyGO v0.76, and iDEP.951 web tools. On finding network visualization, the most over-represented and correlated pathways were neuronal and sensory organ development, calcium signalling pathway, Mitogen-activated protein kinase (MAPK) and Smad signalling pathway, Ras-proximate-1, or Ras-related protein 1 (Rap 1) signalling pathway, apoptosis, and oxidative stress. Similarly, down-regulated genes were most expressed in mRNA processing, immune system, B-cell receptor signalling pathway, Nucleotide oligomerization domain (NOD)-like receptors (NLRs) signalling pathway and nonsense-mediated decay (NMD) pathway. The heat stress-responsive genes identified in this study will facilitate our understanding of the molecular basis for climate resilience and heat tolerance in Indian dairy crossbreeds.

Maternal nutrition and fetal imprinting of the male progeny

The global population as well as the demand for human food is rapidly growing worldwide, which necessitates improvement of efficiency in livestock operations. In this context, environmental factors during fetal and/or neonatal life have been observed to influence normal physical and physiological function of an individual during adulthood, and this phenomenon is called fetal or developmental programming. While numerous studies have reported the impact of maternal factors on development of the female progeny, limited information is available on the potential effects of fetal programming on reproductive function of the male offspring. Therefore, the objective for this review article was to focus on available literature regarding the impact of maternal factors, particularly maternal nutrition, on reproductive system of the male offspring. To this end, we highlighted developmental programming of the male offspring in domestic species (i.e., pig, cow and sheep) as well as laboratory species (i.e., mice and rat) during pregnancy and lactation. In this sense, we pointed out the effects of maternal nutrition on various functions of the male offspring including hypothalamic-pituitary axis, hormonal levels, testicular tissue and semen parameters.

Developmental programming of the ovarian reserve in livestock

Mammalian females are born with a finite number of follicles in their ovaries that is referred to as the ovarian reserve. There is a large amount of variation between females in the number of antral follicles that they are born with, but this number is positively correlated to size of the ovarian reserve, has a strong repeatability within a female, and a moderate heritability. Although the heritability is moderate, numerous external factors including health, nutrition, ambient temperature, and litter size influence the size and function of the ovarian reserve throughout life. Depletion of the ovarian reserve contributes to reproductive senescence, and genetic and epigenetic factors can lead to a more rapid decline in follicle numbers in some females than others. The relationship of the size of the ovarian reserve to development of the reproductive tract and fertility is generally positive, although some studies report antagonistic associations of these traits. It seems likely that management decisions and environmental factors that result in epigenetic modifications to the genome throughout life may cause variability in the function of ovarian genes that influence fecundity and fertility, leading to differences in reproductive longevity among females born with ovarian reserves of similar size. This review summarizes our current understanding of factors influencing size of the ovarian reserve in cattle, sheep, and pigs and the relationship of the ovarian reserve to reproductive tract development and fertility. It provides strategies to apply this knowledge to improve diagnostics for better assessment of fertility and reproductive longevity in female livestock.

Developmental programming of production and reproduction in dairy cows: IV. Association of maternal milk fat and protein percentage and milk fat to protein ratio with offspring's birth weight, survival, productive and reproductive performance and AMH concentration from birth to the first lactation period

Although the association of maternal milk production with developmental programming of offspring has been investigated, there is limited information available on the relationship of maternal milk components with productive and reproductive performance of the offspring. Therefore, the present study was conducted to analyze the association of maternal milk fat and protein percentage and milk fat to protein ratio with birth weight, survival, productive and reproductive performance and AMH concentration in the offspring. In study I, data of birth weight, milk yield and reproductive variables of offspring born to lactating dams (n = 14,582) and data associated with average maternal milk fat percentage (MFP), protein percentage (MPP) and fat to protein ratio (MFPR) during 305-day lactation were retrieved. Afterwards, offspring were classified in various categories of MFP, MPP and MFPR. In study II, blood samples (n = 339) were collected from offspring in various categories of MFP, MPP and MFPR for measurement of serum AMH. Maternal milk fat percentage was positively associated with birth weight and average percentage of milk fat (APMF) and protein (APMP) and milk fat to protein ratio (FPR) during the first lactation, but negatively associated with culling rate during nulliparity in the offspring (P < 0.05). Maternal milk protein percentage was positively associated with birth weight, APMF, APMP, FPR and culling rate, but negatively associated with milk yield and fertility in the offspring (P < 0.05). Maternal FPR was positively associated with APMF and FPR, but negatively associated with culling rate, APMP and fertility in the offspring (P < 0.05). However, concentration of AMH in the offspring was not associated with MFP, MPP and MFPR (P > 0.05). In conclusion, the present study revealed that maternal milk fat and protein percentage and their ratio were associated with birth weight, survival, production and reproduction of the offspring. Yet it was a preliminary research and further studies are required to elucidate the mechanisms underlying these associations.

Effect of Milk-Feeding Frequency and Calcium Gluconate Supplementation on Growth, Health, and Reproductive and Metabolic Features of Holstein Heifers at a Rearing Farm

We compared the effects of milk-feeding in 288 Holstein calves (72 per group) which were fed twice (2F) or thrice (3F) daily, with or without the addition of hydrogenated fat-embedded calcium gluconate (G) supplemented in the starter food and in the daily diet up to the age of 9 months, on the calves' metabolism, growth, health, and reproductive efficiency up to first pregnancy. The calves received 6 L of milk replacer (130 g/L) and had ad libitum access to water and textured calf starter with or without gluconate. Gluconate supplementation promoted a "catch-up" in growth in supplemented calves compared to their counterparts that did not receive gluconate. Gluconate appeared to reduce animal metabolic stress during key events, such as weaning and transfer into open-door pens, reducing fructosamine (352.61 vs. 303.06 in 3FG and 3F, respectively; p = 0.028) and urea (3F revealed the highest values compared with the other three groups: 19.06 for 3F vs. 13.9 (2F), 13.7 (2FG), and 14.3 (3FG), respectively, p = 0.002) from weaning onwards. The feeding of dairy calves with milk replacer three rather than two times per day tended to be associated with better health from weaning to 4 months old; parameters such as ultrasound lung score and calf health score improved over time (p < 0.001). Thrice-daily feeding with milk replacer tended to reduce the number of artificial inseminations per pregnancy in heifers by 0.2 points (p = 0.092). We confirmed significant correlations between early health and growth parameters and reproductive efficiency and a positive correlation between body weight and average daily weight gain and the thickness of the back fat layer in young heifers (r = 0.245; p < 0.0001; r = 0.214; p < 0.0001 respectively). Our study was conducted on a commercial farm with reasonably effective animal management, so baseline welfare was likely satisfactory.

Developmental programming of reproduction in the female animal

Successful reproduction is a cornerstone in food animal industry in order to sustain food production for human. Therefore, various methods focusing on genetics and postnatal environment have been identified and applied to improve fertility in livestock. Yet there is evidence indicating that environmental factors during prenatal and/or neonatal life can also impact the function of reproductive system and fertility in the animals during adulthood, which is called the developmental programming of reproduction. The current review summarizes data associated with the developmental origins of reproduction in the female animals. In this regard, this review focuses on the effect of plane of nutrition, maternal body condition, hypoxia, litter size, maternal age, parity, level of milk production and milk components, lactocrine signaling, stress, thermal stress, exposure to androgens, endocrine disrupting chemicals, mycotoxins and pollutants, affliction with infection and inflammation, and maternal gut microbiota during prenatal and neonatal periods on the neuroendocrine system, puberty, health of reproductive organs and fertility in the female offspring. It is noteworthy that these prenatal and neonatal factors do not always exert their effects on the reproductive performance of the female by compromising the development of organs directly related to reproductive function such as hypothalamus, pituitary, ovary, oviduct and uterus. Since they can impair the development of non-reproductive organs and systems modulating reproductive function as well (e.g., metabolic system and level of milk yield in dairy animals). Furthermore, when these factors affect the epigenetics of the offspring, their adverse effects will not be limited to one generation and can transfer transgenerationally. Hence, pinpointing the factors influencing developmental programming of reproduction and considering them in management of livestock operations could be a potential strategy to help improve fertility in food animals.

The importance of developmental programming in the dairy industry

The concept of developmental programming suggests that environmental influences during pre- and early postnatal life that can have long-term effects on future health and performance. In dairy cattle, maternal body growth, age, parity and milk yield, as well as environmental factors during gestation, have the potential to create a suboptimal environment for the developing fetus. As a result, the calf's phenotype may undergo adaptations. Moreover, developmental programming can have long-term effects on subsequent birth weight, immunity and metabolism, as well as on postnatal growth, body composition, fertility, milk yield and even longevity of dairy cows. This review provides an overview of the impact of developmental programming on later health and performance in dairy cows.

Developmental programming of production and reproduction in dairy cows: III. Association of level of maternal milk production with offspring's birth weight, survival, productive and reproductive performance and AMH concentration from birth to the first lactation period

Although some studies investigated the relationship of dam milk production (DMP) with offspring birth weight and productive performance, limited information is available on the association of level of DMP with reproductive performance in dairy cows. Therefore, the present study was conducted to understand whether dams with various levels of milk production produce offspring with different fertility. In study I, offspring were classified based on the level of DMP into five categories, including DMP1 (dams with <10.00 × 103 kg of 305-day milk production), DMP2 (dams with ≥10.00 × 103 kg and <12.00 × 103 kg of 305-day milk production), DMP3 (dams with ≥12.00 × 103 kg and <14.00 × 103 kg of 305-day milk production), DMP4 (dams with ≥14.00 × 103 kg and <16.00 × 103 kg of 305-day milk production) and DMP5 (dams with ≥16.00 × 103 kg of 305-day milk production). In study I, data of birth weight, milk yield and reproductive variables of 14,536 offspring born to lactating dams and corresponding data of DMP were retrieved. In study II, blood samples (n = 339) were collected from offspring in various categories of DMP for measurement of serum AMH. Offspring were heavier at birth in DMP4 and DMP5 categories than DMP1 and DMP2 categories (P < 0.05). Milk yield of offspring increased as DMP elevated (P < 0.05); however, offspring in DMP1 and DMP2 categories produced higher milk as compared with their dams during primiparity (P < 0.05) whereas offspring in DMP3, DMP4 and DMP5 categories produced less milk as compared with their dams during primiparity (P < 0.05). Milk fat to protein ratio during the first month of lactation was greater in DMP4 and DMP5 categories than DMP1 category (P < 0.05). Offspring of DMP4 and DMP5 categories were inseminated and conceived at younger ages than offspring of DMP1 category during nulliparity (P < 0.05). Calving to conception interval was longer in DMP5 than DMP1 category in primiparous offspring (P < 0.05), but concentration of AMH did not differ among various categories of DMP (P > 0.05). In conclusion, dams with greater level of milk production produced heavier offspring with higher milk yield but worse transgenerational improvement in milk production and diminished reproductive performance, which were seemingly under higher pressure of negative energy balance during the first month of lactation.

The effects of heat stress on intrauterine development, reproductive function, and ovarian gene expression of F1 female mice as well as gene expression of F2 embryos†

Exposure to heat stress (HS) in utero was postulated to trigger an adaptive molecular response that can be transmitted to the next generation. Hence, this study assessed the impact of HS exposure at different stages of the gestational period of mice on the female F1 population and their offspring. Heat stress exposure (41°C and 65% relative humidity-RH) occurred during the first half (FP), the second half (SP), or the entire pregnancy (TP). A control group (C) was maintained in normothermic conditions (25°C, 45% RH) throughout the experiment. Heat stress had a significant negative effect on intrauterine development, mainly when HS exposure occurred in the first half of pregnancy (FP and TP groups). Postnatal growth of FP and TP mice was hindered until 4 weeks of age. The total number of follicles per ovary did not vary (P > 0.05) between the control and HS-exposed groups. Mean numbers of primordial follicles were lower (P < 0.05) in the sexually mature FP than those in SP and TP F1 females. However, the mean number of viable embryos after superovulation was lower (P < 0.05) in TP compared with C group. The expression of genes associated with physiological and cellular response to HS, autophagy, and apoptosis was significantly affected in the ovarian tissue of F1 females and F2 in vivo-derived blastocysts in all HS-exposed groups. In conclusion, exposure to HS during pregnancy compromised somatic development and reproductive parameters as well as altered gene expression profile that was then transmitted to the next generation of mice.

Association between maternal growth in the pre-conception and early gestational period of nulliparous dairy heifers with anti-Müllerian hormone in their female offspring

Anti-Müllerian hormone (AMH) is secreted by granulosa cells of healthy, growing follicles and is positively correlated with the ovarian reserve. Maternal and environmental factors, such as nutrition, disease, parity and endocrine disruptors, are thought to have a profound impact on ovarian reserve development during early foetal life. For genetic progress, it can be advantageous to breed dairy replacements from heifers to expedite the generation interval; however, there is some evidence that nulliparous animals produce female offspring with smaller ovarian reserves compared with multiparous animals. The objective of this prospective, observational study was to determine whether maternal growth in the pre-conception and early gestational period of nulliparous dairy heifers is associated with pre-weaning AMH concentrations in their female offspring. Our hypothesis was that excessive growth in this period would negatively impact AMH concentrations. Seasonal, pasture-based dairy heifer calves (n = 156) born from nulliparous dams, from six Irish farms, were blood sampled at an average of 60 days of age in spring 2022 and tested for AMH. Mixed-effects linear regression models were constructed with Box-Cox transformed AMH concentration as the dependent variable. The independent variables tested included maternal average daily gain (ADG) from pre-breeding examination (PBE) to pregnancy diagnosis (PD) between 30 and 60 days in calf (DIC), ADG from PBE to PD over 60 DIC and ADG between the two PDs. Calf breed and age at sampling were forced into the models, and the farm was treated as a random effect in all models. We found that as ADG increased from the pre-breeding period to their first PD visit, the AMH concentration in their offspring reduced. However, ADG explained only a small amount of the variation in AMH concentrations (marginal R2  = 0.041). In conclusion, the results of our study suggest that excessive growth prior to conception and in early gestation of nulliparous heifers could impact the ovarian reserve of their female offspring, and may imply that farmers should avoid excessive growth in the immediate pre-breeding and early gestational periods.

Ameliorating Effect of Sodium Selenite on Developmental and Molecular Response of Bovine Cumulus-Oocyte Complexes Matured in Vitro Under Heat Stress Condition

Selenium (Se), an essential trace element, plays an important role in the antioxidative defense mechanism, and it has been proven to improve fertility and reproductive efficiency in dairy cattle. The present study evaluated the potential protective action of Se supplement of in vitro maturation (IVM) media on the maturation and subsequent development of bovine cumulus-oocyte complexes (COCs) exposed to heat stress (HS). The treatment with Se improved the viability of cumulus cells (CCs) and oocytes (P < 0.05). The proportion of oocytes reached metaphase II (MII) and those arrested at metaphase I (MI) was greater and lower in treatment than control respectively (P < 0.05). Supplementation with Se increased the percentage of cleaved embryos, total blastocysts, and blastocyst/cleavage ratio (P < 0.05). Moreover, the upregulation of CCND1, SEPP1, GPX-4, SOD, CAT, and downregulation of GRP78, CHOP, and BAX in both Se-treated CCs and oocytes were recorded. The upregulation of NRF2 was detected in Se-treated CCs other than in oocytes, which showed upregulation of IGF2R and SOX-2 as the markers of quality as well. Se supplement in IVM media improved the viability, maturation, and the level of transcripts related to antioxidant defense and quality of heat-treated oocytes, which coincided with greater subsequent development outcomes. Se ameliorated the viability of CCs along with upregulation of antioxidative candidate gene expression and downregulation of apoptosis-related ones to support their protective role on restoring the quality of oocytes against compromising effects of HS.

Developmental programming of production and reproduction in dairy cows: II. Association of gestational stage of maternal exposure to heat stress with offspring's birth weight, milk yield, reproductive performance and AMH concentration during the first lactation period

Although the negative effect of maternal exposure to heat stress on production and reproduction of offspring has been reported, there are some discrepancies among various studies about which gestational stage is more critical in this regard. Therefore, the present research was conducted to identify during which stage(s) of pregnancy maternal exposure to heat stress would lead to more dramatic decrease in productive and reproductive performance of offspring. To this end, offspring were classified based on the gestational stage they were in utero exposed to heat stress into four categories, including heat stress exposure (HSE) during only the first trimester of gestation (HSE1), HSE during the first and second trimester of gestation (HSE2), HSE during the second and third trimester of gestation (HSE3) and HSE during only the third trimester of gestation (HSE4). In study I, data of birth weight, milk yield and reproductive variables of 11,788 offspring and data of the month they were conceived were retrieved. In study II, blood samples (n = 521) were collected from offspring in various categories of HSE for measurement of serum AMH. Offspring in HSE1 and HSE2 categories were heavier than offspring in HSE3 and HSE4 categories (P < 0.0001). Offspring in HSE1 and HSE3 categories had the lowest and highest milk production, respectively (P < 0.05). First service conception rate was the greatest and worst in HSE1 and HSE4 categories, respectively (P < 0.05). Service per conception and calving to conception interval were greater in HSE2 than HSE4 category (P < 0.05). Concentration of AMH was lower in HSE1 than HSE4 category (P < 0.05). In conclusion, the present study indicated that the early stage of gestation could be a more critical period for the negative impact of in utero heat stress on developmental programming of milk production and ovarian reserves. Yet an evident temporal pattern for the adverse effect of maternal heat stress on developmental programming of reproductive performance in offspring was not found.

Developmental programming of production and reproduction in dairy cows: I. Association of maternal parity with offspring's birth weight, milk yield, reproductive performance and AMH concentration during the first lactation period

Multiparous dams have been reported to produce offspring with greater fertility and higher AMH concentration, as a marker of ovarian reserves, as compared with nulliparous and primiparous dams. Yet it has remained to be addressed whether this phenomenon can still be true for old multiparous cows which might experience some geriatric changes in their reproductive system. Therefore, the present study was conducted to evaluate the productive and reproductive performance of offspring with different maternal parity. To this end, offspring were classified based on their maternal parities into four categories, including offspring of nulliparous (no previous parity), primiparous (one previous parity), young multiparous (two to six previous parities) and old multiparous (seven or more previous parities) dams. In study I, data of birth weight, milk yield and reproductive variables of 11,788 offspring and data of their maternal parity were retrieved. In study II, blood samples (n = 521) were collected from offspring with various maternal parity for measurement of serum AMH. Birth weight was the lowest in the offspring of nulliparous dams (P < 0.0001) and it was lower in offspring of primiparous and old multiparous dams than offspring of young multiparous dams (P < 0.05). Milk production was the lowest in offspring of old multiparous dams (P < 0.01), and it was lower in offspring of young multiparous dams than offspring of nulliparous and primiparous dams (P < 0.0001). Offspring of old multiparous dams had greater first service conception rate, less services per conception and shorter calving to conception interval than offspring of nulliparous, primiparous and young multiparous dams (P < 0.05). Furthermore, AMH concentration was higher in offspring of old multiparous dams than offspring of nulliparous and primiparous dams (P < 0.05). In conclusion, the present study revealed greater milk production in offspring resulting from dams with lower parity, probably due to the genetic selection for improvement of milk production in dairy cows which imparts the younger generations greater genetic merits for milk production. Reproductive performance, however, was greater in offspring born to dams with higher parity, particularly those born to old multiparous dams, and this phenomenon might be related to their lower milk production and higher AMH concentration.

Identification of temporal patterns of environmental heat stress of Holstein dairy heifers raised in Mediterranean climate during their in-utero and post-natal life periods and modelling their effects on age at first calving

A retrospective study was conducted to evaluate temporal patterns of environmental heat stress during the in-uterus period of development (IUP) and the 3-month post-natal (PN) period of dairy heifers, and to estimate their association with the age at first calving (AFC). Data from 30 dairy herds in Northern Greece including 9098 heifers were extracted from National Cattle Database. Data (2005-2019) regarding 230,100 farm-specific ambient daily temperature and relative humidity records, were obtained from ERA5-Land. Average monthly Temperature-Humidity-Index values (THI; low≤68, and high>68) were calculated and matched for each heifer to their IUP and PN. Subsequently, Cluster Analysis was used with monthly THIs as predictors to allocate heifers to THI clusters. The association of clusters with AFC was assessed with Generalized Linear Mixed Model analysis, an extended form of multiple linear regression. Finally, 8 Heat Stress Clusters (HSC; namely HSC-1 to HSC-8) were identified. Compared to HSC-8 (8th-9th IUP months and 1st PN month) heifers of HSC-5 (4th-7th IUP months) and HSC-6 (6th-8th IUP months) calved 13.8 and 17.8 days later, respectively (P < 0.01-0.001). Moreover, when AFC was treated as a binary variable, heifers of HSC-5 and HSC-6 had 1.15 and 1.34 (P < 0.01-0.001) higher risk of calving for the first time later than 787 days compared to HSC-8, respectively.

Review: The ovarian follicular reserve - implications for fertility in ruminants

Ruminants are born with a finite number of healthy ovarian follicles and oocytes (ovarian reserve) and germ cell proliferation in the developing foetal gonad predominantly occurs during early gestation. Two markers have been established to reliably estimate the size of the ovarian reserve in cattle: the number of antral follicles ≤3 mm in diameter recruited per follicular wave (Antral Follicle Count, AFC) and peripheral concentrations of the Anti-Müllerian hormone (AMH). Studies that used one or both indicators show that the size of ovarian reserve varies greatly among age-matched individuals, but is highly repeatable in the same animal. Conditions during prenatal life are likely among the causes of such variation in the ovarian reserve. In addition, the size of the ovarian reserve is a moderately heritable trait in cattle. The association between ovarian reserve and fertility is controversial. Several studies indicate that cattle with a low ovarian reserve have phenotypic characteristics that are associated with suboptimal fertility. On the contrary, the presence and absence of a positive association between AFC and/or AMH and fertility measures (i.e. no. on services/conception, pregnancy rates, pregnancy loss) have been equally reported in cattle. In conclusion, the size of the ovarian reserve in the progeny can be enhanced by improving management of the dam from preconception to early gestation and also through genetic selection. However, although the ovarian reserve may be among the determinants of reproductive success in ruminants, the use of AFC/AMH as reliable predictors of fertility is yet to be established. Furthermore, the possibility that there is a complex interaction of AFC, AMH and reproduction has yet to be fully characterised and exploited to improve fertility in cattle.

Replacement of the first GnRH by estradiol in the breeding Ovsynch of Double Ovsynch protocol could improve fertility in Holstein dairy cows

Unlike GnRH, estradiol could induce emergence of a new follicular wave regardless of the size of follicle. Therefore, the present study was conducted to understand whether replacement of the first GnRH by estradiol in the breeding protocol of Double Ovsynch program could enhance fertility. Cows were randomly assigned to two groups, including Double Ovsynch protocol (Control; n = 120) and Ovsynch-estradiol-PGF2α-GnRH (EPG) protocol (Treatment; n = 120). Cows in both groups were subjected to presynchronization Ovsynch. Seven days later, cows in the control group received GnRH, which was followed by PGF2α and GnRH 7 days and 9 days plus 8 h later, respectively. Cows in treatment group received estradiol 7 days after the second GnRH of presynchronization Ovsynch, which was followed by PGF2α and GnRH 7 days and 10 days plus 8 h later, respectively. Cows were subjected to timed AI (TAI) 16 h after final GnRH in both groups. Pregnancy per AI (P/AI) was greater in cows in treatment than control group (64.17 % vs. 44.17 %, respectively; P = 0.02). Cows with a follicle with diameter ≥ 10 mm (F10) at the beginning of EPG in treatment group had greater P/AI than cows without a F10 at the beginning of breeding Ovsynch in control group (P ≤ 0.05). Pregnancy per AI was greater in cows with a CL at the beginning of EPG in treatment group than cows without a CL at the same timepoint in treatment group, and cows with or without a CL at the beginning of breeding Ovsynch in control group (P ≤ 0.05). In conclusion, inclusion of estradiol in Double Ovsynch protocol as a replacement for the first GnRH of breeding Ovsynch could improve fertility, particularly in cows with a CL at the initiation of EPG.

Evidence that elevation of maternal somatic cell count could lead to production of offspring with inferior reproductive and productive performance in dairy cows during the first lactation period

Although the effect of mastitis on reproduction and production of lactating dairy cows has been vastly studied, little information is available about the association of maternal udder health status with offspring reproduction and production. Therefore, the present research was conducted to study the association between maternal average monthly somatic cell count (SCC) with reproduction, anti-Müllerian hormone (AMH) concentration, udder health status and milk production in the offspring. Based on maternal average monthly SCC (MSCC), offspring were classified into five categories including MSCC1 (SCC <200,000; n = 3005), MSCC2 (200,000 ≤ SCC <400,000; n = 252), MSCC3 (400,000 ≤ SCC <600,000; n = 103), MSCC4 (600,000 ≤ SCC <800,000; n = 40) and MSCC5 (SCC ≥800,000; n = 61). Data associated with reproduction, production and udder health status of offspring were retrieved from the herd database. In addition, blood samples were collected from a subset of offspring (n = 136) for measurement of serum AMH, as a reliable marker of ovarian reserves. Offspring in MSCC5 category had more services per conception and longer calving to conception interval than offspring in MSCC1 and MSCC2 categories (P < 0.05). The average number of SCC and risk of clinical mastitis in the offspring were not associated with MSCC (P > 0.05). But offspring in MSCC5 category produced less milk, fat and protein than offspring in MSCC1 category (P < 0.05). In addition, AMH concentration was lower in MSCC5 than MSCC1 category (P < 0.05). In conclusion, the present study showed that elevated maternal average monthly SCC could culminate in birth of offspring with inferior reproductive performance, smaller size of ovarian reserves and lower level of milk production during the first lactation period.

Thermoprotective molecules: Effect of insulin-like growth factor type I (IGF-1) in cattle oocytes exposed to high temperatures

The adverse effects of heat stress (HS) on the welfare and productivity of cattle are the result of the associated hyperthermia and the physiological and behavioral mechanisms performed by the animal to regulate body temperature. The negative effects of HS on in vitro oocyte maturation and in vitro bovine embryo production have been reported; being one of the major concerns due to economic and productive losses, and several mechanisms have been implemented to reduce its impact. These mechanisms include supplementation of the medium with hormones, adjuvants, identification of protective genes, among others. This review aims to explore the cellular and molecular mechanisms of insulin-like growth factor-1 (IGF-1) during in vitro and in vivo maturation of bovine oocytes and its thermoprotective effect under HS. Although the supplementation of the culture medium during oocyte maturation with IGF-1 has been implemented during the last years, there are still controversial results, however, supplementation with low concentration showed a positive effect on maturation and thermoprotection of oocytes exposed to higher temperatures. Additionally, IGF-1 is involved in multiple cellular pathways, and it may regulate cell apoptosis in cases of HS and protect oocyte competence under in vitro conditions.

Programming effects of late gestation heat stress in dairy cattle

The final weeks of gestation represent a critical period for dairy cows that can determine the success of the subsequent lactation. Many physiological changes take place and additional exogenous stressors can alter the success of the transition into lactation. Moreover, this phase is pivotal for the final stage of intrauterine development of the fetus, which can have negative long-lasting postnatal effects. Heat stress is widely recognised as a threat to dairy cattle welfare, health, and productivity. Specifically, late gestation heat stress impairs the dam's productivity by undermining mammary gland remodelling during the dry period and altering metabolic and immune responses in early lactation. Heat stress also affects placental development and function, with relevant consequences on fetal development and programming. In utero heat stressed newborns have reduced birth weight, growth, and compromised passive immune transfer. Moreover, the liver and mammary DNA of in utero heat stressed calves show a clear divergence in the pattern of methylation relative to that of in utero cooled calves. These alterations in gene regulation might result in depressed immune function, as well as altered thermoregulation, hepatic metabolism, and mammary development jeopardising their survival in the herd and productivity. Furthermore, late gestation heat stress appears to exert multigenerational effects, influencing milk yield and survival up to the third generation.

Prenatal transportation stress did not impact ovarian follicle count for three generations of female Brahman offspring

As prenatal transportation stress altered behavior and adrenal glucocorticoid secretion of calves, we hypothesized that prenatal transportation stress would decrease ovarian reserve size and negatively impact female offspring fertility. The impact of prenatal transportation stress on ovarian follicle numbers in female offspring for three generations was studied. Brahman cows were transported for 2 h on day 60 ± 5, 80 ± 5, 100 ± 5, 120 ± 5, and 140 ± 5 of gestation. Ovaries were collected from offspring of transported or non-transported dams at multiple ages. Primordial, primary, secondary, and antral follicles were histologically analyzed. Antral follicle numbers were determined by ultrasound in a subset of offspring. Numbers of primordial, primary, secondary, and antral follicles were analyzed using the MIXED procedure, while the CORR procedure of SAS was used to determine the correlation between follicles observed by ultrasonography and histology. There were no differences (P > 0.05) in the number of primordial, primary, secondary, antral, or total follicles observed histologically due to treatment. Younger females had significantly greater numbers of follicles than older females (P < 0.0001). Antral follicles tended to be correlated with total histological ovarian follicles (P = 0.10). There was no difference in the number of antral follicles observed at ultrasound due to treatment (P = 0.3147), or generation (P = 0.6005) when controlling for age at observation. These results show that short-term transportation stress during early- to mid-gestation did not impact fertility as measured by ovarian follicle numbers in female Brahman offspring for three generations.

Long-Term Consequences of Adaptive Fetal Programming in Ruminant Livestock

Environmental perturbations during gestation can alter fetal development and postnatal animal performance. In humans, intrauterine growth restriction (IUGR) resulting from adaptive fetal programming is known as a leading cause of perinatal morbidity and mortality and predisposes offspring to metabolic disease, however, the prevalence and impact in livestock is not characterized as well. Multiple animal models have been developed as a proxy to determine mechanistic changes that underlie the postnatal phenotype resulting from these programming events in humans but have not been utilized as robustly in livestock. While the overall consequences are similar between models, the severity of the conditions appear to be dependent on type, timing, and duration of insult, indicating that some environmental insults are of more relevance to livestock production than others. Thus far, maternofetal stress during gestation has been shown to cause increased death loss, low birth weight, inefficient growth, and aberrant metabolism. A breadth of this data comes from the fetal ruminant collected near term or shortly thereafter, with fewer studies following these animals past weaning. Consequently, even less is known about how adaptive fetal programming impacts subsequent progeny. In this review, we summarize the current knowledge of the postnatal phenotype of livestock resulting from different models of fetal programming, with a focus on growth, metabolism, and reproductive efficiency. We further describe what is currently known about generational impacts of fetal programming in production systems, along with gaps and future directions to consider.

Effects of Selenium as a Dietary Source on Performance, Inflammation, Cell Damage, and Reproduction of Livestock Induced by Heat Stress: A Review

Heat stress as a result of global warming has harmful consequences for livestock and is thus becoming an urgent issue for animal husbandry worldwide. Ruminants, growing pigs, and poultry are very susceptible to heat stress because of their fast growth, rapid metabolism, high production levels, and sensitivity to temperature. Heat stress compromises the efficiency of animal husbandry by affecting performance, gastrointestinal health, reproductive physiology, and causing cell damage. Selenium (Se) is an essential nutritional trace element for livestock production, which acts as a structural component in at least 25 selenoproteins (SELs); it is involved in thyroid hormone synthesis, and plays a key role in the antioxidant defense system. Dietary Se supplementation has been confirmed to support gastrointestinal health, production performance, and reproductive physiology under conditions of heat stress. The underlying mechanisms include the regulation of nutrient digestibility influenced by gastrointestinal microorganisms, antioxidant status, and immunocompetence. Moreover, heat stress damage to the gastrointestinal and mammary barrier is closely related to cell physiological functions, such as the fluidity and stability of cellular membranes, and the inhibition of receptors as well as transmembrane transport protein function. Se also plays an important role in inhibiting cell apoptosis and reducing cell inflammatory response induced by heat stress. This review highlights the progress of research regarding the dietary supplementation of Se in the mitigation of heat stress, addressing its mechanism and explaining the effect of Se on cell damage caused by heat stress, in order to provide a theoretical reference for the use of Se to mitigate heat stress in livestock.

Across-generation effects of maternal heat stress during late gestation on production, female fertility and longevity traits in dairy cows

This research paper focuses on time-lagged heat stress (HS) effects from an across-generation perspective. Temperature × humidity indexes (THI) from the last 8 weeks of pregnancy were associated with subsequent female offspring performances. The offspring dataset considered 172 905 Holstein dairy cows from calving years 2002-2013 from 1,968 herds, located in the German federal state of Hesse. Production traits included milk yield (MKG), protein percentage (PRO%), fat percentage (FAT%), somatic cell score (SCS) and milk urea nitrogen (MUN) from the first official test-day in first lactation. Female fertility traits were the non-return-rate after 56 d (NRR56) in heifers and the interval from calving to first insemination (ICFI) in first parity cows. Longevity traits were the length of productive life (LPL), lifetime productivity in milk yield (LTP-MKG) and milk yield per day of life (MKG-DL). The association analyzes for 10 traits combined with meteorological data from 8 single weeks before calving implied in total 80 different runs. THI ≥50 from all single 8 weeks before calving had unfavorably significant effects on FAT%, ICFI and LPL. Heat stress in terms of THI ≥60 from the last 3 weeks before calving impaired MKG. NRR56 decreased with increasing THI, as observed for all 6 weeks before calving. LTP-MKG and MKG-DL decreased due to high THI in the last 4 weeks before calving. Heat stress (THI ≥60) during late pregnancy had no significantly unfavorable impact on PRO% and MUN. Interestingly, SCS in offspring declined with increasing THI during late pregnancy. In conclusion, for most of the primary and functional traits, unfavorable impact of HS from the dry period on time-lagged performances in offspring was identified, even on longevity. From a practical perspective, our data suggest to provide HS abatement to late gestation dams to avoid long-term adverse effects on the offspring.

Impacts of Epigenetic Processes on the Health and Productivity of Livestock

The dynamic changes in the epigenome resulting from the intricate interactions of genetic and environmental factors play crucial roles in individual growth and development. Numerous studies in plants, rodents, and humans have provided evidence of the regulatory roles of epigenetic processes in health and disease. There is increasing pressure to increase livestock production in light of increasing food needs of an expanding human population and environment challenges, but there is limited related epigenetic data on livestock to complement genomic information and support advances in improvement breeding and health management. This review examines the recent discoveries on epigenetic processes due to DNA methylation, histone modification, and chromatin remodeling and their impacts on health and production traits in farm animals, including bovine, swine, sheep, goat, and poultry species. Most of the reports focused on epigenome profiling at the genome-wide or specific genic regions in response to developmental processes, environmental stressors, nutrition, and disease pathogens. The bulk of available data mainly characterized the epigenetic markers in tissues/organs or in relation to traits and detection of epigenetic regulatory mechanisms underlying livestock phenotype diversity. However, available data is inadequate to support gainful exploitation of epigenetic processes for improved animal health and productivity management. Increased research effort, which is vital to elucidate how epigenetic mechanisms affect the health and productivity of livestock, is currently limited due to several factors including lack of adequate analytical tools. In this review, we (1) summarize available evidence of the impacts of epigenetic processes on livestock production and health traits, (2) discuss the application of epigenetics data in livestock production, and (3) present gaps in livestock epigenetics research. Knowledge of the epigenetic factors influencing livestock health and productivity is vital for the management and improvement of livestock productivity.

Association between heat stress during intrauterine development and the calving-to-conception and calving-to-first-service intervals in Holstein cows

Heat stress has been widely studied in relation to its effects on the production and reproduction of dairy cattle. However, the long-term effects of heat stress during intrauterine development on adult cows have been scarcely considered. Thus, the aim of this study was to evaluate possible changes in the reproductive performance of Holstein cows gestated under different values of the Temperature-Humidity Index (THI) during their intrauterine development. Data collected from a database of reproductive and productive records of 10,790 Holstein cows from the central region of Argentina and the THI data from the agrometeorological station of the Instituto Nacional de Tecnología Agropecuaria (INTA) EEA Rafaela, Santa Fe, Argentina, were used. The gestation of the cows evaluated was divided into trimesters, in which the highest THI cycles (sum of three or more consecutive days of exposure to a THI ≥72 during each trimester) and number of days with a THI ≥ 72 were calculated. The calving-to-conception and calving-to-first-service intervals of the cows evaluated were considered as reproductive variables associated with their first lactation. Generalized Linear Mixed Models were used, considering the cow's dairy farm as a random factor within the model. The exposure of the animals to environments with a THI ≥72 during the first trimester of gestation had a negative impact on the reproductive efficiency parameters analyzed. The results obtained indicate that the exposure of pregnant females to high THI values has a long-term impact on their daughters, which may contribute to a decrease in their reproductive performance, possibly through inherited epigenetic characteristics that remain in later generations through fetal programming.

Exposure of dairy cows to high environmental temperatures and their lactation status impairs establishment of the ovarian reserve in their offspring

The objectives of this study were to establish if exposure of pregnant dairy cows to high environmental temperatures and humidity during the first trimester of pregnancy impairs the establishment of the ovarian reserve (total number of healthy follicles and oocytes in ovaries) and fertility in their offspring. Serum anti-Müllerian hormone (AMH) concentrations and number of follicles ≥3 mm (antral follicle count; AFC) were assessed on a random day of the estrous cycle in 310 sixteen-month-old dairy heifers. Based on season of their conception and early fetal life, heifers were separated into 2 groups: summer (mean monthly temperature-humidity index = 69.33 ± 2.6) and winter (temperature-humidity index = 54.91 ± 1.08). The AMH and AFC were lower in summer (419.27 ± 22.81 pg/mL and 9.32 ± 0.42 follicles, respectively) compared with winter heifers (634.91 ± 47.60 pg/mL and 11.84 ± 0.46 follicles, respectively) and were not influenced by farm and age at sampling. Heifers born to dams that were not being milked during gestation had lower AMH and AFC compared with offspring of cows on their first lactation, whereas no difference was detected between offspring of cows on their first and subsequent lactations. Summer and winter heifers had similar age at first service and at first calving, and similar number of services per conception. Regardless of season in early fetal life, heifers were classified into 3 groups based on AMH and AFC (low = 20%, intermediate = 60%, high = 20%). Heifers with the lowest AMH were older at first service compared with herd mates with intermediate AMH, but age at first calving and number of services per conception were similar among AMH categories. No difference was detected in any of the fertility measures among AFC categories. Heifers born to mothers exposed to high environmental temperatures in early gestation had smaller ovarian reserves compared with herd mates conceived in winter, but no association between season of early fetal life and fertility at first conception was established. Season of conception and maternal lactation status affect the size of the ovarian reserve, but not fertility, at first conception in the progeny.

Evidence for quadratic association between serum anti-Müllerian hormone (AMH) concentration and fertility in dairy cows

In cattle, results of some but not other studies indicated there has been an association of circulating anti-Müllerian hormone (AMH) concentration with reproductive variables. Considering the inconsistency in results among previous studies, there was evaluation of associations between circulating AMH and reproductive performance in dairy cows, and to this end, the prevailing data of serum AMH concentration and reproductive variables were used (n = 172). Preliminarily, association of AMH concentration with reproductive indices were analyzed using linear and quadratic models. Subsequently, cows were categorized based on AMH concentrations in four equal quartiles, including cows with the least (Q₁; n = 43), moderately lesser (Q₂; n = 43), moderately greater (Q₃; n = 43) and greatest (Q₄; n = 43) AMH concentrations, and reproductive variables were compared among the respective AMH quartiles. Initially, assessments indicated reproductive variables were not linearly associated with serum AMH (P > 0.05); however, for all reproductive variables except days to first breeding service (DFS) there was a quadratic association with serum AMH (P < 0.05). Results from analysis of reproductive performance in various AMH quartiles indicated there was a longer period of DFS for cows in Q₃ than Q₁ (P < 0.05). First postpartum insemination to conception and calving to conception intervals were shorter for cows in Q₃ than Q₁ and Q₄ (P < 0.05) and for cows in Q₂ than Q₁ (P < 0.05). In conclusion, results from the present study indicate cows with intermediate AMH concentrations had greater reproductive performance.

Association of exposure to air pollution and green space with ovarian reserve hormones levels

Exposure to air pollution has been associated with adverse health effects while exposure to greenspace has been associated with public health benefits. However, the available evidence on the association of exposure to air pollution with ovarian reserve markers is still scarce, with no study on such an association with greenspace exposure. Therefore, this study aimed to investigate the association of exposure to particulate matter with diameter of less than 1, 2.5 and 10 μm (PM₁, PM_2.5, PM₁₀), traffic indicators (distance from women's residence to major roads and total street length in different buffers around women's residential address) and greenspace indicators (residential surrounding greenspace and distance to green spaces) with serum levels of anti-müllerian hormone (AMH) and follicle stimulating hormone (FSH) as markers of ovarian reserve. This cross-sectional study was based on 67 women residing in Sabzevar, Iran (2018). Basal serum levels of FSH and AMH were measured by the enzyme-linked immunosorbent assays (ELISA). Land use regression models were used to estimate PMs concentrations at residential addresses and the average of normalized difference vegetation index (NDVI) in different buffers was used to characterize residential surrounding greenspace. Multiple linear regression models were developed to estimate the association of AMH and FSH with exposure to air pollution, traffic, and greenspace (one at a time) controlled for relevant covariates. In fully adjusted models, there was an inverse association between exposure to PM₁, PM_2.5 as well as total street length in 100 m buffer around women's residence and AMH level (β = -0.89, 95% confidence interval (CI): -1.43, -0.35, P-value ≤ 0.01, β = -1.11, 95% CI: -1.67, -0.55, P-value ≤ 0.01 and β = -0.76, 95% CI: -1.48, -0.50, P-value = 0.03, respectively). Moreover, increase in distance from home to nearest major road as well as residential surrounding greenspace (100 m buffer) and decrease in residential distance to a green space larger than 5000 m² were associated with increase in serum level of AMH. However, we did not observe any significant association between exposure to air pollution, traffic, and greenspace with FSH level. Overall, our findings supported a beneficial association of exposure to greenspace and detrimental association of exposure to air pollution with ovarian reserve.

Effects of periconceptional heat stress on primiparous and multiparous daughters of Holstein dairy cows

To meet growing worldwide demands for animal products, animal production will need to increase in capacity and efficiency. Every opportunity to improve animal protein yield should be considered and explored. Developmental programming is one such opportunity that has not yet been thoroughly investigated in farm animal production. While developmental programming can be advantageous for the survival of the offspring, it is often described in conjunction with negative consequences. The known and potential causes and mechanisms are numerous, often stemming from some sort of stress experienced during the prenatal or early postnatal period. One stressor that is particularly concerning for farm animal production is heat stress. Heat stress is known to elicit adaptations associated with developmental programming in several species, but has not been investigated in dairy cattle until recently. Multiple studies have shown that heat stress experienced during the periconceptional period is generally associated with reduced milk production of resulting offspring. This could be the result of adaptations within the pre-ovulatory oocyte or early developing embryo. Interestingly, in a few select comparisons, periconceptional heat stress was associated with greater milk production. This was only observed when dairy cattle calved in the spring, and would therefore be reaching peak milk production in late spring or early summer (in heat stress). This is consistent with the match/mismatch theory associated with developmental programming, where matched prenatal/postnatal environments confer advantageous adaptations and mismatched prenatal/postnatal environments are generally detrimental to the offspring. While these studies are important additions to our growing knowledge of heat stress impacts on dairy cow production, the broader implication of developmental programming requires further investigation.

Prenatal heat stress effects on gestation and postnatal behavior in kid goats

Consequences of heat stress during pregnancy can affect the normal development of the offspring. In the present experiment, 30 Murciano-Granadina dairy goats (41.8 ± 5.7 kg) were exposed to 2 thermal environments varying in temperature-humidity index (THI) from 12 days before mating to 45 days of gestation. The environmental conditions were: gestation under thermal-neutral (TN; THI = 71 ± 3); and gestation under heat stress (HS; THI = 85 ± 3) conditions. At 27 ± 4 days old, female kids exposed to in utero TN (IUTN; n = 16) or in utero HS (IUHS; n = 10) were subjected to 2 tests: arena test (AT) and novel object test (NOT), the latter was repeated at 3 months of age. Additionally, 8 months after birth, a subset of IUTH and IUHS growing goats (n = 8 each; 16.8 ± 3.4 kg BW) were exposed to 2 environmental conditions in 2 consecutive periods: a basal thermal-neutral period (THI = 72 ± 3) for 7 days, and a heat-stress period (THI = 87 ± 2) for 21 days. In both periods, feeding, resting, posture, and thermally-associated behaviors were recorded. The gestation length was shortened by 3 days in GHS goats. In the AT, IUHS kids showed a lower number of sniffs (P < 0.01) compared to IUTN. In the NOT, IUHS kids also tended to show a lower number of sniffs (P = 0.09). During heat exposure, IUTN and IUHS growing goats spent more time resting and exhibited more heat-stress related behaviors such as panting and drinking (P < 0.001); however, no differences were observed between both groups. In conclusion, heat stress during the first third of pregnancy shortened gestation length and influenced the exploratory behavior of the kids in the early life. However, behavior responses to heat stress during the adulthood were not affected by the in utero thermal treatment.

Selenium Attenuates Chronic Heat Stress-Induced Apoptosis via the Inhibition of Endoplasmic Reticulum Stress in Mouse Granulosa Cells

Heat stress induces apoptosis in various cells. Selenium, an essential micronutrient, has beneficial effects in maintaining the cellular physiological functions. However, its potential protective action against chronic heat stress (CHS)-induced apoptosis in granulosa cells and the related molecular mechanisms are not fully elucidated. In this study, we investigated the roles of selenium in CHS-induced apoptosis in mouse granulosa cells and explored its underlying mechanism. The heat treatment for 6–48 h induced apoptosis, potentiated caspase 3 activity, increased the expression levels of apoptosis-related gene BAX and ER stress markers, glucose-regulated protein 78 (GRP78), and CCAAT/enhancer binding protein homologous protein (CHOP) in mouse granulosa cells. The treatment with ER stress inhibitor 4-PBA significantly attenuated the adverse effects caused by CHS. Selenium treatment significantly attenuated the CHS- or thapsigargin (Tg, an ER stress activator)-induced apoptosis, potentiation of caspase 3 activity, and the increased protein expression levels of BAX, GRP78, and CHOP. Additionally, treatment of the cells with 5 ng/mL selenium significantly ameliorated the levels of estradiol, which were decreased in response to heat exposure. Consistently, administering selenium supplement alleviated the hyperthermia-caused reduction in the serum estradiol levels in vivo. Together, our findings indicate that selenium has protective effects on CHS-induced apoptosis via inhibition of the ER stress pathway. The current study provides new insights in understanding the role of selenium during the process of heat-induced cell apoptosis.

Heat stress impairs in vitro development of preantral follicles of cattle

Although detrimental effects of heat stress on antral follicle development have been well studied, long-term effects - affecting the preantral follicle pool - are still largely unknown. The goal of this study was to evaluate effects of heat stress on growth, viability, gene expression and ATP production of preantral follicles of cattle. Follicles at the primary, early secondary and secondary stages were isolated from cattle ovaries and individually cultured while imposing physiological (CON; 38.5 °C) or intermittent heat stress (HS; 38.5 °C for 16 h and 41 °C for 8 h daily) conditions for 7 days. Individual follicles were subjected to real-time qPCR for determination of relative abundance of BAX, HSPA1A and SOD1 mRNA transcripts and evaluated for ATP production. Treatment for 7 days with intermittent HS decreased viability (P =  0.01) and diameter (P =  0.03) of preantral follicles. Relative abundances of BAX and HSPA1A mRNA transcripts were greater in follicles of the CON and HS groups that became non-viable during culture (P <  0.05); relative abundance of SOD1 mRNA transcript, however, was only greater in non-viable follicles of the HS group (P <  0.05), but not non-viable follicles of the CON group (P =  0.3). The ATP production was not different between viable follicles of the CON and HS group (P = 0.86). In conclusion, all stages of growing preantral follicles of cattle were susceptible to negative effects of heat stress. Follicles at the secondary stage of development were most sensitive, followed by early secondary and primary follicles.

Evaluation of anti-Mullerian hormone, antral follicle count and progesterone concentration during estrous cycle in Murrah buffaloes

An experiment was conducted to study the anti-Mullerian hormone (AMH) concentration, antral follicle count (AFC) and progesterone (P4) concentration during estrous cycle in Murrah buffaloes. Seven animals of 5–10 years were selected for the study. All the animals were synchronized as per the ovsync protocol and the pair of ovary of each animal was scanned by ultrasonography on 0, 3rd, 7th, 11th, 14th, 17th and 21st day of estrous cycle. Blood was collected on the same day to evaluate serum AMH and P4 concentration. The nonsignificant difference was observed in antral follicle count of 3–5 mm, 5–8 mm and total follicles count (> 3 mm), whereas, significantly lower mean values of >8 mm of antral follicles were recorded on the day of estrus (0.14 ±0.14) as compared to 3rd, 7th, 11th, 14th, 17th and 21st day of estrous cycle. The significant individual variation was recorded in average mean of 3 - 5 mm and total antral follicle count (>3 mm). However, the difference for 5 - 8 mm and >8 mm was nonsignificant. The positive correlation of low and high antral follicle count was observed in the present study. Two animals of low antral follicle count remained non pregnant and two animals showed 3 follicular waves during estrous cycle. The nonsignificant difference was recorded in AMH concentration during estrous cycle, whereas, individual variation in AMH concentration differ significantly. The progesterone concentration showed significant increase and decrease in values according to the stages of estrous cycle.

Influence of temperature-humidity index on conception rate of Nelore embryos produced in vitro in northern Brazil

Considering the high temperatures that the tropical climate provides to most of Brazil and the effects of thermal stress on reproductive processes, the objective of the present study was to analyze, in the warmer months of 2016, conception rates of Nelore bovine embryos in Acre state. For this purpose, oocytes were aspirated (ultrasound-guided follicular aspiration), matured, fertilized with Nelore bull semen, cultured for 6 days, and then the embryos were transferred to crossbred recipients. Pregnancy diagnosis was performed 30 and 60 days after embryo transfer. Meteorological data were obtained at www.inmet.gov.br to generate temperature-humidity index (THI). The data from the conception rates and periods of the year were submitted to the chi-square test at 5% probability to verify independence. Regression analysis was used to verify the relationship between THI and gestation rate. There was a strong relationship between conception rates and THI values, verified by an increase in conception rates as THI values were reduced and a decrease when THI reached the highest value. Our findings demonstrated a negative effect of heat stress in conception rates of crossbred cows in northern Brazil.

Evaluation of anti-mullerian hormone in heifers and anestrus Murrah buffaloes

An experiment was conducted to quantify the anti-mullerian hormone (AMH) concentration in heifers and anestrus Murrah buffaloes during fortnight blood collections for 3 months. Two groups of heifer and anestrus Murrah buffaloes were formed on the basis of record and actual per rectal examination. Serum AMH concentration was determined by ELISA method, using bovine AMH ELISA kit. Nonsignificant difference was recorded in AMH concentration (pg/ml) in heifer and anestrus buffaloes during fortnight collection (0, 15, 30, 45, 60 and 75). Highly significant individual variation was observed in heifer and anestrus buffaloes in this study. Heifers (6) with AMH concentration above 200 pg/ml were pregnant and 4 heifers with AMH concentration below 200 pg/ml were non pregnant. AMH concentration is a reliable phenotypic marker to predict the number of healthy follicles and oocytes, in ovaries and predict the future potential of heifers and young adult buffaloes. The cut-off value of AMH concentration in Murrah heifers buffaloes as a marker of fertility may be 200 pg/ml. However, study with more number of buffaloes is required to determine the accurate cut-off value of AMH concentration.

Inferior fertility and higher concentrations of anti-Müllerian hormone in dairy cows with longer anogenital distance

Anogenital distance (AGD), which is an indicator of prenatal androgen exposure, has been reported to have high variability and negative association with fertility in dairy cows. Prenatal exposure to androgens could influence the development of primordial follicles and size of ovarian reserve, which is related to reproduction. However, the relationship between AGD and size of ovarian reserve has not been studied. Therefore, the present study was conducted to determine the association between AGD and circulating anti-Müllerian hormone (AMH), as an indirect marker of ovarian reserve, and to evaluate serum AMH concentration and reproductive performance in dairy cows with short and long AGD. Anogenital distance was measured 28 to 32 d postpartum, and based on the median of AGD, cows were divided into 2 subsets including short (n = 43) and long (n = 43) AGD groups. Afterward, serum AMH was evaluated on the day of estrus in cows that were estrus-synchronized. Furthermore, reproductive data of dairy cows during the previous lactation period were collected from the herd database. Concentrations of serum AMH tended to be positively associated with length of AGD, and there was a tendency for higher serum AMH concentrations in the long (634.89 ± 74.52 pg/mL) than short (451.39 ± 45.92 pg/mL) AGD group (0.05 <P ≤ 0.10). There was a tendency for more days to first service, lower first service conception rate, and higher proportion of repeat breeders in long (99.95 ± 5.34 d, 30.23% and 32.56%, respectively) than short (89.07 ± 4.97 d, 48.84% and 16.28%, respectively) AGD cows (0.05 <P ≤ 0.10). Services per conception did not differ between short (2.30 ± 0.27) and long (2.93 ± 0.29) AGD cows (P > 0.05). Calving to conception interval was prolonged in long (194.30 ± 17.12 d) than short (147.14 ± 13.11 d) AGD cows (P ≤ 0.05). In conclusion, the present study revealed elevated serum AMH concentrations and poor reproductive performance in cows with longer AGD compared with cows with shorter AGD.

Maternal age influences the number of primordial follicles in the ovaries of yearling Angus heifers

The number of antral follicles detectable by ultrasonography in heifers is influenced by age of the dam, because daughters of primiparous cows have fewer antral follicles than daughters of mature cows. We, therefore, hypothesized that heifers with primiparous dams would have fewer primordial follicles in their ovaries than heifers born to mature (4+ y) cows. Angus heifers (n = 464) were submitted for ultrasonographic evaluation of antral follicle number at 325, 355, and 385 d of age. Ovaries were collected from a random subset of heifers (n = 79) and processed for histological evaluation to determine number of primordial follicles. A greater percentage of heifers with primiparous dams had a corpus luteum at first ultrasonographic examination; however, a greater percentage of heifers with multiparous dams had ovulated by the start of breeding (P <  0.01). Heifers with primiparous dams had fewer antral follicles detectable by ultrasonography (P <  0.01). Heifers with primparous dams had fewer surface antral follicles on their ovaries (P <  0.01), and the number of primordial follicles per histological section was less for heifers with primiparous dams (P =  0.02). These data indicate that the lesser number of antral follicles detectable by ultrasonography in heifers with primparous dams is due to less ovarian follicle reserves. Selecting replacement heifers from mature dams may result in daughters with greater fertility and reproductive longevity; however, further research is necessary to determine if interactions between size of the ovarian follicle reserve and age at puberty influence fertility and reproductive longevity in replacement heifers.

Nulliparous and primiparous cows produce less fertile female offspring with lesser concentration of anti-Müllerian hormone (AMH) as compared with multiparous cows

Nutritional partitioning to fetal development differ among nulliparous, primiparous and multiparous cows, leading to birth of smaller calves to nulliparous and primiparous than multiparous dams. The prenatal nutritional state could influence ovarian reserve and fertility in the adult offspring. The effect of maternal parity on ovarian reserve and reproduction of female offspring, however, has not been investigated in cattle. Accordingly, a retrospective research was conducted to study reproductive variables in nulliparous- (n = 310), primiparous- (n = 236) and multiparous-born (n = 323) female offspring during the first four lactation periods in dairy cows. Additionally, anti-Müllerian hormone (AMH), as a reliable marker of ovarian reserve, was measured in a subset of nulliparous- (n = 51), primiparous- (n = 51) and multiparous-born (n = 49) female offspring. Birth weight in multiparous-born calves was greater than that in nulliparous- and primiparous-born calves (P <  0.01). Days to first service was shorter in multiparous-born female offspring as compared with nulliparous- and primiparous-born female offspring (P <  0.05). First service conception rate, proportion of repeated breeders, service per conception and calving to conception interval were greater in multiparous-born than nulliparous-born cows (P <  0.05). Cumulative culling rate was greater in primiparous-born cows than nulliparous- and multiparous-born cows (P <  0.05). The AMH concentration was greater in multiparous-born than nulliparous- and primiparous-born cows (P <  0.05). In conclusion, the present study revealed that in comparison with multiparous cows, nulliparous and primiparous cows, particularly nulliparous cows, produce female offspring with lesser reproductive performance and smaller size of ovarian reserves.