Energy level in winter diets of Fallow deer: effect on plasma levels of insulin-like growth factor-I and sex ratio of their offspring

Effects of body condition score at initiation of the breeding season on reproductive performance and overall productivity of Bos taurus and B. indicus beef cows

This experiment was conducted to evaluate reproductive and productive responses of Bos indicus and B. taurus beef cows according to body condition score (BCS) at initiation of the annual breeding season. Non-pregnant, suckling multiparous cows were assigned to a fixed-time artificial insemination treatment regimen followed by natural service. Cows were classified as having a BCS < 5.0 (B. taurus, n = 158; B. indicus, n = 248) or BCS ≥ 5.0 (B. taurus, n = 173; B. indicus, n = 122). Calving rate was greater (P < 0.03) in cows with a BCS ≥ 5.0 (93.7 % and 85.1 % in B. taurus, 83.6 % and 73.3 % in B. indicus), which also calved earlier (P < 0.01) compared with cows with a BCS < 5.0. Cows with a BCS ≥ 5.0 weaned more (P ≤ 0.05) calves compared with those with a BCS < 5.0, which were older (P ≤ 0.04) and weighed more (P ≤ 0.09) at weaning (258 and 252 kg in B. taurus, 213 and 203 kg in B. indicus). Kilograms of calf weaned/cow in the breeding herd were greater (P ≤ 0.03) in cows with a BCS ≥ 5.0 compared with those with a BCS < 5.0 (221 and 200 kg in B. taurus, 159 and 129 d in B. indicus). Collectively, cows with a BCS ≥ 5.0 at initiation of the breeding season had greater reproductive and overall productivity during a cow-calf cycle, and these outcomes were observed in B. taurus and B. indicus cowherds.

Gonadotropin Inhibitory Hormone and Its Receptor: Potential Key to the Integration and Coordination of Metabolic Status and Reproduction

Since its discovery as a novel gonadotropin inhibitory peptide in 2000, the central and peripheral roles played by gonadotropin-inhibiting hormone (GnIH) have been significantly expanded. This is highlighted by the wide distribution of its receptor (GnIH-R) within the brain and throughout multiple peripheral organs and tissues. Furthermore, as GnIH is part of the wider RF-amide peptides family, many orthologues have been characterized across vertebrate species, and due to the promiscuity between ligands and receptors within this family, confusion over the nomenclature and function has arisen. In this review, we intend to first clarify the nomenclature, prevalence, and distribution of the GnIH-Rs, and by reviewing specific localization and ligand availability, we propose an integrative role for GnIH in the coordination of reproductive and metabolic processes. Specifically, we propose that GnIH participates in the central regulation of feed intake while modulating the impact of thyroid hormones and the stress axis to allow active reproduction to proceed depending on the availability of resources. Furthermore, beyond the central nervous system, we also propose a peripheral role for GnIH in the control of glucose and lipid metabolism at the level of the liver, pancreas, and adipose tissue. Taken together, evidence from the literature strongly suggests that, in fact, the inhibitory effect of GnIH on the reproductive axis is based on the integration of environmental cues and internal metabolic status.

Post-mortem recovery, in vitro maturation and fertilization of fallow deer (Dama dama, Linnaeus 1758) oocytes collected during reproductive and no reproductive season

Habitat degradation leads to small and fragmented populations, lower genetic variability and fertility overtime. Assisted reproductive techniques represent important tools to cope with the dramatic loss of biodiversity. Fallow deer (Dama dama), beyond its high commercial value and wide distribution, may represent the most suitable model to study endangered cervids. In this study, oocytes were recovered post-mortem from fallow deer during the breeding and no breeding seasons and were in vitro matured (IVM). The ability of cryopreserved thawed sperm samples recovered by electroejaculation from four adult males was tested by in vitro fertilization of IVM oocytes. The number of oocytes collected per ovary did significantly vary across seasons from 6.2 ± 0.92 during breeding season to 10.4 ± 1.26 during no breeding season (p = .006). Oocytes collected during the breeding season showed higher in vitro fertilization rate compared to the no breeding season (p = .045). However, no embryos reached the blastocyst stage. Semen samples obtained by electroejaculation were successfully cryopreserved, although the cryopreservation process negatively affected most kinetic parameters, mainly at 2 hr post-thawing. Moreover, the percentage of rapid spermatozoa significantly decreased between fresh samples and at 2 hr post-thawing, whereas the percentage of slow spermatozoa increased across the same period (p < .05). Our study provides the logistic steps for the application of assisted reproductive techniques in fallow deer and might be of great interest for genetic resource bank planning.

High-energy diet enhances spermatogenic function and increases sperm midpiece length in fallow deer (Dama dama) yearlings

Nutrition is a major factor involved in the sexual development of livestock ruminants. In the male, a high-energy diet enhances the reproductive function, but its effects on the underlying processes such as spermatogenic efficiency are not yet defined. Moreover, the possible changes in sperm size due to a supplemented diet remain poorly investigated. The main goal of this study was to evaluate whether a high-energy diet affects the spermatogenic activity, epididymal sperm parameters (concentration, morphology, morphometry and acrosome integrity) and blood testosterone levels in fallow deer yearlings. For this purpose, 32 fallow deer were allocated into two groups according to their diet: control (pasture) and experimental (pasture and barley grain) groups. Fallow deer from the experimental group showed a significant increase in the Sertoli cell function and sperm midpiece length, together with a higher testicular mass, sperm concentration and percentage of normal spermatozoa than the control group (p < 0.05). We also found a tendency for higher blood testosterone levels in the animals fed with barley grain (p = 0.116). The better sperm quality found in the experimental group may be related to their higher efficiency of Sertoli cells and to an earlier onset of puberty. The results of the present work elucidate the mechanisms by which dietary supplementation enhances the male sexual development and might be useful for better practices of livestock management in seasonal breeders.

Sex-dependent insulin like growth factor-1 expression in preattachment equine embryos

An adjustment of sex ratio of offspring to the conditions present at conception is seen in many mammals including horses. This depends on preferential survival of male embryos under conditions of high energy intake. In several species, growth factors including insulin like growth factor (IGF)-1 have been shown to promote embryonic development by decreasing apoptosis and increasing cell proliferation. We hypothesized that sex-related differences in IGF-1 expression in equine embryos during the phase of maternal recognition of pregnancy might exist and thus contribute to preferential survival of embryos from either of both sexes under specific environmental conditions. Insulin like growth factor-1 mRNA expression of in vivo-produced equine embryos on different days of pregnancy (Day 8, N = 6; Day 10, N = 8; Day 12, N = 14) was analyzed. Insulin like growth factor-1 mRNA expression was evaluated by reverse transcription quantitative polymerase chain reaction. The sex of the embryo was determined by detection of X-inactivation specific transcript (Xist) RNA and equine sex determining region of the Y chromosome DNA. Embryos positive for Xist expression were classified as female, and Xist negative and equine sex determining region of the Y chromosome positive embryos were classified as male. From 28 embryos tested, 15 (54%) showed positive Xist expression and were thus classified as female. Insulin like growth factor-1 mRNA expression was influenced by sex (P = 0.01) but not by day of pregnancy (relative expression of IGF-1 in relation to β-actin, Day 8: male 5.1 ± 2.1, female 11.4; Day 10: male 5.2 ± 1.6, female 17.4 ± 6.7; Day 12: male 2.6 ± 0.3, female 11.6 ± 2.4). Results demonstrate an increased expression of IGF-1 in female equine embryos. Sex-related influences on expression of the IGF system are probably related to a gradual X chromosome inactivation.

Nutritional skewing of conceptus sex in sheep: effects of a maternal diet enriched in rumen-protected polyunsaturated fatty acids (PUFA)

BACKGROUND

Evolutionary theory suggests that in polygynous mammalian species females in better body condition should produce more sons than daughters. Few controlled studies have however tested this hypothesis and controversy exists as to whether body condition score or maternal diet is in fact the determining factor of offspring sex. Here, we examined whether maternal diet, specifically increased n-6 polyunsaturated fatty acid (PUFA) intake, of ewes with a constant body condition score around the time of conception influenced sex ratio.

METHODS

Ewes (n = 44) maintained in similar body condition throughout the study were assigned either a control (C) diet or one (F) enriched in rumen-protected PUFA, but otherwise essentially equivalent, from four weeks prior to breeding until d13 post-estrus. On d13, conceptuses were recovered, measured, cultured to assess their capacity for interferon-tau (IFNT) production and their sex determined. The experiment was repeated with all ewes being fed the F diet to remove any effects of parity order on sex ratio. Maternal body condition score (BCS), plasma hormone and metabolite concentrations were also assessed throughout the study and related to diet.

RESULTS

In total 129 conceptuses were recovered. Ewes on the F diet produced significantly more male than female conceptuses (proportion male = 0.69; deviation from expected ratio of 0.5, P < 0.001). Conceptus IFNT production was unaffected by diet (P > 0.1), but positively correlated with maternal body condition score (P < 0.05), and was higher (P < 0.05) in female than male conceptuses after 4 h culture. Maternal plasma hormone and metabolite concentrations, especially progesterone and fatty acid, were also modulated by diet.

CONCLUSION

These results provide evidence that maternal diet, in the form of increased amounts of rumen-protected PUFA fed around conception, rather than maternal body condition, can skew the sex ratio towards males. These observations may have implications to the livestock industry and animal management policies when offspring of one sex may be preferred over the other.

Sexual dimorphism in interferon-tau production by in vivo-derived bovine embryos

Interferon-tau (IFN-tau) is an anti-luteolytic factor responsible for preventing regression of the maternal corpus luteum (CL) during early pregnancy of cattle. In vitro-produced (IVP) bovine embryos first produce IFN-tau as blastocysts. In the present study, we have examined whether sexually dimorphic production of IFN-tau, which is observed among IVP blastocysts, also occurs among in vivo-produced blastocysts, and whether this difference between the sexes persists to day 14 when silencing of one of the X-chromosomes in the trophectoderm is complete. Embryos were flushed from cattle that had been superovulated and bred by AI. Blastocysts (63 male, 62 female) recovered between days 8.5 and 9.5 of pregnancy, were cultured individually. No differences were observed between males and females in either their developmental stage or quality at the beginning, during, and at the end of culture. Female embryos produced more IFN-tau than males by 24 hr (mean values, males: 16.6 +/- 3.7, females: 49.4 +/- 9.0 pg per embryo; P < 0.05) and 48 hr (male: 189.8 +/- 37.1, female: 410.9 +/- 66.6 pg per embryo; P < 0.05). However, the variability in IFN-tau production between individual blastocysts was so great that IFN-tau secretion is unlikely to be of value as a non-invasive means to predict embryo sex. When conceptuses were recovered at day 14, elongating males (n = 25) and females (n = 24) were similar in dimension and did not differ in their IFN-tau production after 4.5 hr (male: 2,550 +/- 607, female: 2,376 +/- 772 ng per conceptus) and 24 hr (male: 12,056 +/- 2,438, female: 8,447 +/- 1,630 ng per conceptus) of culture. Thus, sexual dimorphism in IFN-tau production is observed in both IVP and in vivo-produced expanded blastocysts, but is lost by day 14 of in vivo development.

Facultative adjustment of mammalian sex ratios in support of the Trivers-Willard hypothesis: evidence for a mechanism

Evolutionary theory predicts that mothers of different condition should adjust the birth sex ratio of their offspring in relation to future reproductive benefits. Published studies addressing variation in mammalian sex ratios have produced surprisingly contradictory results. Explaining the source of such variation has been a challenge for sex-ratio theory, not least because no mechanism for sex-ratio adjustment is known. I conducted a meta-analysis of previous mammalian sex-ratio studies to determine if there are any overall patterns in sex-ratio variation. The contradictory nature of previous results was confirmed. However, studies that investigated indices of condition around conception show almost unanimous support for the prediction that mothers in good condition bias their litters towards sons. Recent research on the role of glucose in reproductive functioning have shown that excess glucose favours the development of male blastocysts, providing a potential mechanism for sex-ratio variation in relation to maternal condition around conception. Furthermore, many of the conflicting results from studies on sex-ratio adjustment would be explained if glucose levels in utero during early cell division contributed to the determination of offspring sex ratios.

Striking variation in the sex ratio of pups born to mice according to whether maternal diet is high in fat or carbohydrate

In female mammals, it remains controversial whether maternal diet and particularly the source and availability of energy can influence sex of offspring born. Outbred female mice were fed ad libitum from 30 days to approximately 45 wk of age on defined, complete diets that differed only in their relative content of fat and carbohydrate to determine whether calorie source influenced litter size and sex ratio of pups. Diet 1 (very high in saturated fat, VHF) provided 60% of calories as fat, mainly lard. Diet 2 (low in saturated fat, LF) was low in fat (10% of calories) but high in carbohydrate. Mice delivered four litters of pups, resulting in a total of 1,048 young born over 108 pregnancies. Gestation length and litter size did not differ between VHF and LF groups and did not change as mice aged. Sex ratio of pups (fraction male) born to mothers on VHF diet was unusually high (0.67) and to mothers on LF diet very low (0.39) over litters 2, 3, and 4. This skewing of sex ratio was related to diets fed and not to body mass of mothers. Age of mothers was an important variable, however. Mice that were first bred at 10 wk of age delivered similar numbers of sons and daughters, whereas virgin mice bred later than 20 wk of age produced litters that were skewed toward males or females according to diet. The data show that the source of calories provided in a nutritionally complete diet to mature female mice can influence sex of offspring born.

Interferon-tau in bovine blastocysts following parthenogenetic activation of oocytes: pattern of secretion and polymorphism in expressed mRNA sequences

A series of experiments were conducted to examine the pattern of production and secretion of interferon-tau (IFN-tau) by blastocysts following parthenogenetic activation of bovine oocytes. In the first experiment, 36.8, 24.1, and 33.2% of IVF-derived and parthenogenetically activated oocytes cultured in the presence or absence of a monolayer of buffalo rat liver cells, respectively, reached the blastocyst stage. Following individual culture of blastocysts, IFN-tau concentration in medium droplets was similar among the three groups, although IVF-derived blastocysts contained significantly more cells. In the second experiment, 156 IVF-derived blastocysts were sexed by PCR with 75 and 81, respectively, being male and female. IFN-tau secretion of these was compared to that of 70 parthenogenetic blastocysts. Female and parthenogenetic blastocysts produced significantly more IFN-tau than their male counterparts. In the third experiment, the ability of hatched blastocysts to form outgrowths and the pattern of their IFN-tau secretion were examined. Of the 48 IVF-derived blastocysts, 44 formed outgrowths compared to 41 of the 42 hatched parthenotes. Parthenogenetic outgrowths were significantly larger after 7 days, but this difference had disappeared after 14 days. IFN-tau secretion did not differ between the two groups. Lastly, sequence analyses of expressed mRNA from individual parthenogenetic blastocyst outgrowths showed four different transcript types which, based on their predicted amino acid sequence, belong to two subgroups, IFN-tau1 and IFN-tau3. In addition, one new transcript sequence was identified, encoding a new protein isoform.

The mammary gland in mammalian evolution: a brief commentary on some of the concepts

Current thinking is highlighting the mammary glands and the process of lactation in the evolutionary success of mammals over and above the selective advantages provided by the nutritional and antimicrobial properties of milk. The extended period of contact between mothers and their young, necessitated by the regular and frequent transfer of milk, particularly characteristic of the primate strategy of reproduction and the primate mode of life, has been suggested to afford the offspring the opportunity for more learning and the eventual development of the levels of intelligence present in "higher" primates. Lactation offers the opportunity for maternal effects on development and the eventual phenotype of the offspring in addition to those that occur during pregnancy or from behavioral interactions. Lactation comes with high metabolic costs, which are manifested in parent-offspring conflict, and special physiological adaptations have evolved which match milk supply to demand by the young.

Sexual dimorphism among bovine embryos in their ability to make the transition to expanded blastocyst and in the expression of the signaling molecule IFN-tau

IFN-tau is a secretory product of trophectoderm of cattle, sheep, and their relatives and is expressed for a few days in early pregnancy after the blastocyst first forms. It serves to alert the mother that she is pregnant. A delayed or less than robust IFN-tau signal is a likely cause of embryonic loss. Here we have determined whether blastocyst production of IFN-tau, which is encoded by a cluster of genes on chromosome 9, differs between the sexes in cattle, as assessed by culture of in vitro-derived embryos on two different media, one complex (tissue culture medium 199 supplemented with serum) with coculture support, the other relatively simple (synthetic oviductal fluid plus albumin). With both media, female blastocysts produced approximately double the amount of IFN-tau as males, regardless of such variables as oocyte batch, blastocyst quality, hatching, and length of time in culture. However, in either tissue culture medium 199, which contains 5.5 mM d-glucose, or in synthetic oviductal fluid, in the presence but not in the absence of added glucose, significantly fewer female than male embryos were able to progress from the morula/early blastocyst stage to more advanced stages of development. It is possible that the differences between male and female embryos both in their production of IFN-tau and in their ability to progress in development in glucose-rich media are manifestations of phenomena that occur in vivo and provide plasticity in embryo selection during early pregnancy.