Dietary excesses of urea influence the viability and metabolism of preimplantation sheep embryos and may affect fetal growth among survivors

Fitness of calves born from in vitro-produced fresh and cryopreserved embryos

In cattle, vitrified/warmed (V/W) and frozen/thawed (F/T), in vitro-produced (IVP) embryos, differ in their physiology and survival from fresh embryos. In this study, we analyzed the effects of embryo cryopreservation techniques on the offspring. IVP embryos cultured with albumin and with or without 0.1% serum until Day 6, and thereafter in single culture without protein, were transferred to recipients on Day 7 as F/T, V/W, or fresh, resulting in N = 24, 14, and 13 calves, respectively. Calves were clinically examined at birth, and blood was analyzed before and after colostrum intake (Day 0), and subsequently on Day 15 and Day 30. On Day 0, calves from V/W and F/T embryos showed increased creatinine and capillary refill time (CRT) and reduced heartbeats. Calves from F/T embryos showed lower PCO₂, hemoglobin, and packed cell volume than calves from V/W embryos while V/W embryos led to calves with increased Na⁺ levels. Colostrum effects did not differ between calves from fresh and cryopreserved embryos, indicating similar adaptive ability among calves. However, PCO₂ did not decrease in calves from V/W embryos after colostrum intake. Serum in culture led to calves with affected (P < 0.05) temperature, CRT, HCO 3 - , base excess (BE), TCO₂, creatinine, urea, and anion gap. On Day 15, the effects of embryo cryopreservation disappeared among calves. In contrast, Day 30 values were influenced by diarrhea appearance, mainly in calves from V/W embryos (i.e., lower values of TCO₂, HCO 3 - , and BE; and increased glucose, anion gap, and lactate), although with no more clinical compromise than calves from fresh and F/T embryos. Diarrhea affected PCO₂ and Na⁺ in all groups. Embryo cryopreservation, and/or culture, yield metabolically different calves, including effects on protein and acid-base metabolism.

Elevated blood urea nitrogen alters the transcriptome of equine embryos

High blood urea nitrogen (BUN) in cows and ewes has a negative effect on embryo development; however, no comparable studies have been published in mares. The aims of the present study were to evaluate the effects of high BUN on blastocoele fluid, systemic progesterone and Day 14 equine embryos. When a follicle with a mean (±s.e.m.) diameter of 25±3mm was detected, mares were administered urea (0.4g kg-1) with sweet feed and molasses (n=9) or sweet feed and molasses alone (control; n=10). Blood samples were collected every other day. Mares were subjected to AI and the day ovulation was detected was designated as Day 0. Embryos were collected on Day 14 (urea-treated, n=5 embryos; control, n=7 embryos). There was an increase in systemic BUN in the urea-treated group compared with control (P<0.05), with no difference in progesterone concentrations. There were no differences between the two groups in embryo recovery or embryo size. Urea concentrations in the blastocoele fluid tended to be higher in the urea-treated mares, with a strong correlation with plasma BUN. However, there was no difference in the osmolality or pH of the blastocoele fluid between the two groups. Differentially expressed genes in Day 14 embryos from urea-treated mares analysed by RNA sequencing were involved in neurological development, urea transport, vascular remodelling and adhesion. In conclusion, oral urea treatment in mares increased BUN and induced transcriptome changes in Day 14 equine embryos of genes important in normal embryo development.

Carvalho PC. Low-Intensity, High-Frequency Grazing Positively Affects Defoliating Behavior, Nutrient Intake and Blood Indicators of Nutrition and Stress in Sheep

The intensity and frequency of grazing affect the defoliating strategy of ruminants, their daily nutrient intake, thus nutrition and physiological status. Italian ryegrass (Lolium multiflorum Lam.) pastures were grazed by sheep either under a low-intensity/high-frequency grazing strategy (Rotatinuous stocking; RN) with nominal pre- and post-grazing sward heights of 18 and 11 cm, respectively, or under a high-intensity/low-frequency strategy (traditional rotational stocking; RT) with nominal pre- and post-grazing sward heights of 25 and 5 cm, respectively. Treatments were arranged under a complete randomized design and evaluated over two periods, in different years. In 2017, the aim was to depict the type of bites that sheep perform during the grazing-down and associate them to the grazing management strategy according to their relative contribution to the diet ingested. In 2018 we estimated the total nutrient intake and evaluated blood indicators of the nutritional status and immune response to stress of sheep. The bite types accounting the most for the diet ingested by RN sheep were those performed on the "top stratum" of plants with around 20, 15, and 25 cm, whereas the type of bites accounting the most for the diet of RT sheep were those performed on "grazed plants" with around 10, 5, and ≤ 3 cm. In 2018, the RN sheep increased by 18% the total organic matter (OM) intake and by 20-25% the intake of soluble nutrients (i.e., crude protein, total soluble sugars, crude fat), digestible OM and of metabolizable energy, and had 17.5, 18, and 6.1% greater blood concentration of glucose, urea nitrogen (BUN) and albumin, respectively, but 17% lower blood neutrophil-to-lymphocyte (N:L) ratio. Sheep grazing vegetative Italian ryegrass pastures under the low-intensity/high-frequency grazing strategy (RN) ingested a diet of better quality from bites allocated on the top stratum of plants, had greater intake of soluble nutrients and blood parameters positively associated with nutritional status and immune response to stress.

Towards a Sustainable Reproduction Management of Dairy Sheep: Glycerol-Based Formulations as Alternative to eCG in Milked Ewes Mated at the End of Anoestrus Period

Simple Summary

Reproductive management of sheep for autumnal lambing often require induction and synchronization of oestrus and ovulation, either for natural mating or artificial insemination, by the use of pharmacological treatments. Such treatments are mostly based on the administration of progesterone followed by a single intramuscular dose of equine chorionic gonadotrophin (eCG) at progesterone withdrawal. However, repeated eCG treatments in consecutive mating seasons can result in the outbreak of resistance with a rise of anti-eCG antibodies. Furthermore, the future use and availability of eCG appears to be strongly challenged by the highly active animal-rights movement because the hormone is obtained from pregnant mares. The present study demonstrated that the administration of glycerol-based formulations to milked ewes is a valid alternative to eCG treatment in reproductive management protocols based on the induction of ovulation with progesterone-releasing devices at the end of anoestrus period. The glucogenic treatment administration to late lactation dairy ewes at the end of the anoestrus period improved their metabolism without harming animal production or animal welfare, thus promoting a sustainable reproductive management of dairy sheep.

Abstract

This study investigated whether the administration of equine chorionic gonadotrophin (eCG) in a protocol to induce and synchronize ovulations before mating could be replaced by the administration of glycerol-based formulations in milked ewes at the end of their seasonal anoestrus. Forty-eight late-lactation dairy ewes of the Sarda breed were synchronized using sponges impregnated with progestogen and then joined with fertile rams (day (D) 0, ram introduction). From D−4 to D−1, the ewes received by gavage either 100 mL of a glucogenic mixture (70% glycerol, 20% propylene glycol and 10% water; GLU group; n = 24) or 100 mL of water (GON group; n = 24) twice daily. Moreover, on the day of sponge withdrawal (D−1), GON ewes received 200 IU of eCG. There were no differences in reproductive performances between groups. GLU ewes showed higher glycemia (p < 0.001), insulinemia (p < 0.05), plasma glycerol (p < 0.001), triglycerides (p < 0.001) and lower cholesterol (p < 0.001), non-esterified fatty acids (NEFA; p < 0.05) and urea (p < 0.001). Plasma osmolality was higher in GLU but only 4 h after dosing (p < 0.001). Milk yield and milk composition were not affected by the treatments with exception of milk glycerol (p < 0.001) and milk urea (p < 0.001), which were higher and lower in GLU than GON ewes, respectively. In conclusion, the administration of the glucogenic mixture to late lactation dairy ewes at the end of anoestrus period resulted in reproductive responses as good as the ones obtained by the eCG treatment, suggesting that the objective of a sustainable reproductive management of dairy sheep can be successfully pursued.

Relationships between blood and follicular fluid urea nitrogen concentrations and between blood urea nitrogen and embryo survival in mares

High blood urea nitrogen (BUN) concentration is linked to low fertility in cows and ewes; however, this relationship has not been reported in mares. The study characterized the relationship between BUN and follicular fluid urea nitrogen (FUN) during follicle growth (Experiment 1) and the impact of BUN from embryo donors on the pregnancy outcome of recipient mares (Experiment 2). In experiment one, follicular fluid and blood samples were collected from mares during diestrus with growing follicles and during estrus with pre-ovulatory follicles (n = 16 and 10 mares, respectively). In experiment two, BUN concentrations of embryo donors were related to pregnancy outcome after embryo transfer. In experiment one, there was a strong positive correlation between BUN and FUN (R = 0.83; P < 0.0001), with higher BUN in mares with growing follicles than with preovulatory follicles (P = 0.004) and higher FUN in growing follicles than in preovulatory follicles (P = 0.031). In experiment two, BUN was higher in donor mares that produced unsuccessful embryos compared to donor mares that produced embryos resulting in successful pregnancies at D14 (P < 0.03). Additionally, there was an effect of age (P = 0.01) and interaction between age and lactation (P = 0.009) in donor mares for embryo survival after embryo transfer. Donor mares with unsuccessful embryos were older than donor mares with successful embryos. Therefore, these experiments showed that BUN was related to follicular fluid environment as well as to the survival of Day 7-8 embryos after transfer to recipient mares.

Administration of glycerol-based formulations in sheep results in similar ovulation rate to eCG but red blood cell indices may be affected

BACKGROUND

The objective of this study was to investigate the metabolic and osmotic effects of different doses of glycerol or a glycerol - propylene glycol mixture in Sarda sheep with the aim to identify those able to beneficially modify ewe's metabolic status without harmful changes in red blood cell (RBC) indices. Thereafter, the selected doses were tested for their effects on ewe's ovarian activity during an induced follicular phase and compared to the effects of a hormonal treatment with equine chorionic gonadotrophin (eCG).

RESULTS

Glycerol was administered alone (G groups: 90% glycerol and 10% water; % v/v) or in combination with propylene glycol (M groups: 70% glycerol, 20% propylene glycol, 10% water; % v/v). Treatments were formulated to provide 100, 75, 50 and 25% of the amount of energy supplied in previous experiments. Obtained results showed that the formulations G75 and M75 (22.5 and 18.2% on DM basis, respectively) induce metabolic changes comparable to those induced by M100. The latter dose has been already evaluated for its effects on sheep metabolism and reproductive performance. However, with these high doses, plasma osmolality increased significantly, and RBC indices showed significant alterations. The low dose groups (G25 and M25, 8.6 and 6.9% on DM basis, respectively) did not show any alterations in plasma osmolality and RBC indices, but the metabolic milieu differed markedly from that of M100. Between the medium dose groups, M50 (12.9% on DM basis) showed a more comparable milieu to M100 than G50 (15.9% on DM basis) and no RBC alterations. Therefore, M75, G75 and M50 doses were tested for their effect on ovarian functions and proved to be equally effective as eCG.

CONCLUSION

The results of the present study evidenced an alteration of RBC indices, and possibly of their functions, as a side effect of glycerol administration at high doses in the diet of ewes. Therefore, protocols foreseeing the administration of glycerol should be tested for their effects on RBC indices and functions. In general terms, the medium dose of the glucogenic mixture (12.9% of dietary DM on offer) should be preferred.

Effect of oral urea supplementation on the endometrial transcriptome of mares

An intravenous large dose of protein led to an increased blood urea nitrogen (BUN), resulting in a lesser uterine pH and altered uterine gene expression in mares. The objective of the present study was to evaluate effects of a more physiological methodology to increase BUN on the endometrium of mares. Mares were fed hay and a treatment or control diet (n = 11 mares/treatment) in a crossover design starting at time of ovulation detection (D0) and continuing until D7. Mares of the treated group were fed urea (0.4 g/kg BW) with sweet feed and molasses, and those of the control group were fed sweet feed and molasses. Blood samples were collected daily, 1 hour after feeding, for BUN determination. Uterine and vaginal pH were determined after the last feeding on D7, and endometrial biopsies were performed. The RNA sequencing of the endometrium of a subset of mares (n = 6/treatment) was conducted. Differentially expressed genes (DEGs) between treatments were calculated (FDR-adjusted P-value<0.1). Urea-treated mares had greater BUN (P < 0.05), with no differences in uterine and vaginal pH compared to control mares. A total of 60 DEGs were characterized, those with largest fold change were SIK1, ATF3, SPINK7, NR4A1 and EGR3. Processes related to necrosis and cellular movement were predicted with the DEGs. Dietary administration of urea resulted in transcriptomic changes in the endometrium of mares related to necrosis, tissue remodeling and concentration of lipids. The observed changes in gene expression after an increased BUN might result in a disruption to the endometrium.

An alternative model for fetal loss disorders associated with mare reproductive loss syndrome

Fertile chicken eggs were used as an alternative model for large animals to evaluate suspect toxic dietary ingredients for fetal loss disorders associated with mare reproductive loss syndrome (MRLS) and fetal losses in other livestock. Nitrate, ammonia, and sulfate may react with proteinaceous compounds to enable the formation of abiotic pathogenic nanoparticles which were constant findings in pathognomonic placental lesions associated with non-infectious fetal losses of previously unknown etiology in mares, chickens and other livestock. The pathogenic nanoparticles may be produced naturally by toxic elements associated with air pollution that affect pasture forages or crops, unintentionally by reactions of these elements in protein-mineral mixes in dietary rations, or endogenously within tissues of fetuses and adult animals. The nanoparticles may form niduses in small vessels and predispose animals to a host of secondary opportunistic diseases affecting the reproductive, respiratory and gastrointestinal tracts of animals. The newly recognized abiotic pathogenic micro and nanoparticles are associated with MRLS. The discovery of the pathogenic nanoparticles led to the identification of nitrate, ammonium, and sulfur, in the form of sulfate, that seemingly enable the formation of the pathogenic nanoparticles in embryonic and fetal tissues.

Metabolic biomarkers, body condition, uterine inflammation and response to superovulation in lactating Holstein cows

The objective was to determine associations between response to superovulation and body condition, subclinical endometritis and circulating metabolic biomarkers [adiponectin, leptin, insulin, IGF1, tumor necrosis factor (TNF) α, interleukin (IL) 1β, IL6, and urea] in lactating dairy cows. Ten multiparous lactating Holstein cows in each body condition score (1-5; 1 emaciated; 5 obese) category (BCSC) 2.00 to < 2.50 (BCSC1), 2.50 to < 3.00 (BCSC2), 3.00 to <3.50 (BCSC3), 3.50 to <4.00 (BCSC4) and 4.00 to 5.00 (BCSC5) groups (total n = 50) were randomly selected and superovulated, timed artificially inseminated with frozen-thawed semen from three sires and embryos collected (n = 50 collections). At embryo collection, blood samples and embryo recovery fluid were collected for determination of metabolic markers and presence of subclinical endometritis (lavage technique; > 6% PMN). In total, 379 embryos were collected (average of 7.6 embryos per superovulation). Mean numbers of total ova and embryos was greater for cows in BCSC2, BCSC3 and BCSC4 groups compared with cows in BCSC1 and BCSC5 groups (P < 0.01). Total number of transferrable embryos were greater for cows in BCSC 2 and BCSC3 groups compared with cows in BCSC1, BCSC4 and BCSC5 groups (P < 0.01). Mean number of total ova and embryos and of transferrable embryos was higher for cows with 0 or 1-6% PMN compared to cows with >6% PMN (P < 0.01). In addition, there was a quadratic association between blood urea nitrogen concentrations and % transferrable embryos (r² = 0.85; P < 0.05) and between BCS and % transferrable embryos (r² = 0.73; P < 0.05). Circulating adiponectin, leptin, insulin, IGF1 and TNFα were greater in cows with moderate to good body condition compared to thin or obese cows (P < 0.05). Circulating adiponectin, leptin, IGF1 and insulin were greater in normal cows (≤6% PMNs), whereas, TNFα and IL1β and IL6 were greater in cows with subclinical endometritis (P < 0.05). In conclusion, BCS and subclinical endometrial inflammation were associated with superovulatory response and embryo quality. Further, circulating metabolic biomarkers were associated with superovulatory response and embryo quality, likely due to donor's metabolic status and uterine environment. Optimizing superovulatory responses and embryo quality in lactating dairy cows requires management of nutrition and uterine health.

A High Protein Model Alters the Endometrial Transcriptome of Mares

High blood urea nitrogen (BUN) decreases fertility of several mammals; however, the mechanisms have not been investigated in mares. We developed an experimental model to elevate BUN, with urea and control treatments (7 mares/treatment), in a crossover design. Urea-treatment consisted of a loading dose of urea (0.03 g/kg of body weight (BW)) and urea injections over 6 hours (0.03 g/kg of BW/h). Control mares received the same volume of saline solution. Blood samples were collected to measure BUN. Uterine and vaginal pH were evaluated after the last intravenous infusion, then endometrial biopsies were collected for RNA-sequencing with a HiSeq 4000. Cuffdiff (2.2.1) was used to identify the differentially expressed genes (DEG) between urea and control groups (false discovery rate-adjusted p-value < 0.1). There was a significant increase in BUN and a decrease of uterine pH in the urea group compared to the control group. A total of 193 genes were DEG between the urea and control groups, with five genes identified as upstream regulators (ETV4, EGF, EHF, IRS2, and SGK1). The DEG were predicted to be related to cell pH, ion homeostasis, changes in epithelial tissue, and solute carriers. Changes in gene expression reveal alterations in endometrial function that could be associated with adverse effects on fertility of mares.

Involvement of Quebracho tannins in diet alters productive and reproductive efficiency of postpartum buffalo cows

This study was conducted to investigate the effects of 10 weeks supplementation of Quebracho tannins (QT; 0 [control], 100 [QT100] or 200 g/[cow·d] [QT200]) to 30 multiparous postpartum buffalo cows (10 cows per group) on milk yield and composition, blood metabolites and reproductive performance. Supplementation of QT100 had no significant effect on milk yield, whereas QT200 decreased (P < 0.05) this trait. Compared with the control group, both QT levels decreased (P < 0.05) fat-corrected milk (FCM) yield, but no significant effects were found on percentages of milk fat and protein. Contrariwise, yields of milk fat, lactose and milk protein were decreased (P < 0.05) when QT200 was supplemented. The solids nonfat (SNF) percentage and yield were decreased (P < 0.05) with QT100 supplementation. Moreover, QT tended to numerically reduce total number of ovarian follicles, number of small follicles, peripheral progesterone concentration and conception rate. Supplementation of QT200 numerically increased number of large follicles, mean diameter of large follicle, number and diameters of corpora lutea. The inclusion of QT200 shortened days open (DO) and decreased number of services per conception. Contrariwise, QT did not show significant effects on serum total protein, albumin, globulin, glucose, cholesterol and triglycerides concentrations. Supplementation of QT100 caused an increase (P < 0.05) of serum urea compared with that in control and QT200 groups. Generally, QT decreased (P < 0.05) serum creatinine concentration. Therefore, the supplementation of a commercial QT to early lactating Egyptian buffalo cows displayed negative consequences on their productive and reproductive performances.

Nutritional effects on resumption of ovarian cyclicity and conception rate in postpartum dairy cows

Increased genetic potential for milk production has been associated with a decline in fertility of lactating cows. Following parturition the nutritional requirements increase rapidly with milk production and result in negative energy balance (NEBAL). NEBAL delays the time of first ovulation thereby affecting ovarian cycles before and during the subsequent breeding period The effects of NEBAL on reinitiation of ovulation are manifested through inhibition of LH pulse frequency and low levels of glucose, insulin and IGF-I in blood that collectively restrain oestrogen production by dominant follicles. Upregulation of LH pulses and peripheral IGF-I in association with the NEBAL nadir increases the likelihood that emerging dominant follicles will ovulate. The legacy of NEBAL is reduced fertility after insemination in conjunction with reduced serum progesterone concentrations. Diets high in crude protein support high milk yield, but may be detrimental to reproductive performance. Depending upon protein quantity and composition, serum concentrations of progesterone may be lower and the uterine luminal environment is altered. High protein intake is correlated with plasma urea concentrations that are inversely related to uterine pH and fertility. The direct effects of high dietary protein and plasma urea on embryo quality and development in cattle are inconsistent. In conclusion, the poor fertility of high producing dairy cows reflects the combined effects of a uterine environment that is dependent on progesterone, but has been rendered suboptimal for embryo development by antecedent effects of negative energy balance and may be further compromised by the effects of urea resultingfrom intake of high dietary protein.

Embryo survival rate in cattle: a major limitation to the achievement of high fertility

Over the past 30-40 years genetic improvement and better nutrition of dairy cows have led to a significant increase in milk production per cow but this is associated with an increase in cow reproductive wastage. Reproductive wastage in the dairy herd particularly in a seasonal calving system, results in a serious financial loss. Early embryo death accounts for a significant portion of cow reproductive wastage and information is becoming available on the extent and timing of early embryo loss and on aspects of embryo growth, development, metabolism and viability. Such information is necessary to facilitate objective investigation of factors that contribute to early embryo death. For heifers and moderate yielding dairy cows published estimates of fertilisation rate of about 90%, and of average calving rates of about 55% indicate an embryonic and foetal mortality rate of about 40%. Of this total loss, 70 to 80% is sustained between days 8 and 16 after insemination, a further 10% between days 16 and 42 and a further 5-8% between day 42 and term. In high yielding cows there is some evidence of a higher increment of late embryo loss. During the period of greatest embryo loss, between days 8 and 16 after fertilisation, there is a dramatic increase in the growth rate and protein content of embryos, particularly from day 13 to day 16 when the increase is exponential. There is evidence that from day 13 to 15 cattle embryos undergo time and developmental stage-dependent changes in the rate of de-novo protein synthesis and protein phosphorylation. It seems that by the time cattle embryos have elongated they have passed their maximal synthetic activity in terms of protein synthesis and phosphorylation, which seems to occur at day 13 or earlier. While there is little published information on the causes of embryo loss it is clear that even a short-term reduction in energy intake near the time of insemination can significantly reduce embryo survival rate. Abo and low post-ovulatory systemic progesterone has been associated with increased embryo loss. Recent evidence shows that elevated systemic concentrations of ammonia and urea per se do not reduce embryo survival rate but there may be other modifying factors, such as negative energy balance, operating in the high yielding dairy cow that lead to reduced fertility when the systemic concentrations of urea and or, ammonia are high.

Consequences for reproductive function of metabolic adaption to load

An effective method for enhancing milk production efficiency in dairy cows is to increase milk yield and significant progress has been achieved through intense selection, assisted by the application of new reproductive techniques. However this increased milk yield has been accompanied by a slow but steady decline in dairy cow fertility. The two main reasons for this reducing level of fertility appear to be selection for increased milk yield and large herd sizes, although the affect of the introduction of Holstein genes needs to be investigated. In addition, other negative consequences such as an increase in the incidence of metabolic diseases and lameness have been observed. This has given rise to public concern that the high-yielding dairy cow may be under a state of metabolic stress during peak lactation and therefore the welfare and performance of other body functions are compromised.

The reason for this decline in fertility is not well understood, although a nutritional influence on the initiation of oestrous cycles, follicular growth, oocyte quality and early embryonic development has been implicated. In early lactation dietary intake is unable to meet the demands of milk production and most cows enter a period of negative energy balance. Negative energy balance has a broadly similar effect to undernutrition leading to a mobilization of body reserves. Furthermore diets high in rumen degradable protein lead to an excess of rumen ammonia, which before it is converted to urea by the liver and excreted in the urine, may cause an alteration in the reproductive tract environment reducing embryo survival. Such major changes in the metabolic and endocrine systems can therefore influence fertility at a number of key points.

Possible reproductive sites where inadequate nutrition may have detrimental effects include: (i) the hypothalamic/pituitary gland where gonadotropin release may be impaired; (ii) a direct effect on the ovaries, where both follicular growth patterns and corpus luteum function may be directly influenced; (iii) the quality of the oocyte prior to ovulation may be reduced and coupled with an inadequate uterine environment will result in reduced embryo survival and (iv) there may be effects on subsequent embryo development. The initiation of normal oestrous cycles post partum is usually delayed in dairy cows with a higher genetic merit for milk production, confirming that intense selection towards high milk yield can compromise reproductive function. In addition, the effects of increased milk yield may include changes in circulating GH and insulin concentrations, which in turn alter both insulin-like growth factor (IGF) and IGF binding protein production. Nutrition has recently been shown to have a direct effect at the level of both the ovaries and the uterus to alter the expression of these growth factors.

In conclusion, further knowledge is required to determine how the metabolic changes associated with high milk output reduce fertility. Identification and understanding of the mechanisms involved and the key sites of action responsible for compromised reproductive function, will enable the identification of possible indices for future multiple-trait selection programmes.

Relationships between nutrition and fertility in dairy cattle

The reduced fertility that is becoming more evident in high yielding dairy cows may be related to many factors including changes in milk production, food intake and fluctuations in body condition. Metabolic and production markers have been studied as a way of predicting success to a particular artificial insemination. Successful conception to a particular service was not associated with milk production, body condition or plasma concentrations of several indicators of metabolic state around the time if insemination. This highlights the importance of time of information collection in fertility management programmes. Increased food intake may reduce systemic progesterone concentrations. This is more evident in sheep than cattle, but a positive relationship between systemic progesterone early post mating and establishment of pregnancy in cattle has been reported. However, progesterone concentrations in the ovarian vein and endometrium are not strongly correlated with systemic progesterone. Thus, the significance of modest changes in systemic progesterone in affecting oocyte and embryo development must be questioned. Blood urea concentrations can be altered by diet, and reduced pregnancy rates have been reported in cows with high urea concentrations. However, in other recent studies, no difference was reported in serum urea in cows that conceived and those that failed to conceive. Pregnancy rate was equally high in heifers when in-vitro produced embryos were transferred to heifers on high and low urea diets. When embryos were produced in sheep on high and low dietary urea, the effects on embryo development appear to occur early in the developmental process, suggesting a substantial effect on the development of the oocyte. The developmental capacity of oocytes and quality of embryos is reduced in cattle maintained on extremely high dietary intakes. Oocyte developmental capacity is reduced in cows of higher genetic merit and embryo quality can be substantially reduced in the early postpartum period. Collectively, these results suggest that high dietary intake or high metabolic load is deleterious to normal oocyte development and establishment of pregnancy. This highlights the importance of further studies on the effect of dietary intake on metabolic state and follicle, oocyte and embryo development. In a practical context, these results highlight the importance of nutritional management and avoiding changes in the amount or type of diet around the time of mating in high-production dairy cows.

Effects of dietary urea on embryo development in superovulated donor ewes and on embryo survival following transfer in recipient ewes

Urea can be fed as a source of nitrogen for rumen micro-organisms to synthesize microbial protein. It is also applied to pasture as a source of nitrogen for grass growth. Reduced fertility and embryonic loss can occur when dietary urea is in excess (McEvoy et al., 1997). Elevated plasma urea resulting from excess rumen degradable protein or dietary urea can decrease uterine pH (Elrod et al., 1993) and pregnancy rate in cows (Butler et al., 1996). The aim of this experiment was to determine the effect of dietary urea on yield and quality of embryos in superovulated donor ewes and on embryo survival (to day 34-36) in recipient ewes following embryo transfer.

Functional amino acids in the development of the pig placenta

The mammalian placenta is essential for supplying nutrients (e.g., amino acids and water) and oxygen from the mother to fetus and for removing fetal metabolites (e.g., ammonia and CO₂ ) from fetus to mother. Thus, placental growth and development are determinants of fetal survival, growth, and development. Indeed, low birth weight is closely associated with reduced placental growth. Providing gestating gilts or sows with dietary supplementation of arginine and glutamine, increases placental growth (including vascular growth), improves embryonic/fetal growth and survival, and reduces the large variation in birth weight among litters. These two amino acids serve as building blocks for tissue protein as well as substrates for the production of polyamines and nitric oxide, which stimulate DNA and protein synthesis and angiogenesis and vascular growth in the placenta. These recent findings not only greatly advance the field of mammalian amino acid metabolism and nutrition, but also provide practical, mechanism-based methods to enhance reproductive efficiency in swine. These results may also help improve embryonic/fetal survival and growth in other livestock species (e.g., sheep and cattle) and in humans.

Protein based flushing related blood urea nitrogen effects on ovarian response, embryo recovery and embryo quality in superovulated ewes

The present study is the first report that evaluates effects of nutritional effects of flushing with differing diet crude protein ratios on blood urea nitrogen (BUN) levels, related some reproductive parameters and embryo quality in ewe. During mating season, before synchronization protocol ewes were fed on alfalfa hay and additive concentrate feeding as flushing. Intra vaginal FGA containing sponges applied for 12 days for the purpose of synchronization and pFSH was administered by 8 declining doses for the purpose of superovulation. Uterus was flushed in the morning of the seventh day of mating and embryos were collected surgically. Collected embryos were qualified according to IETS criterion. There is no dependency found between BUN values measured at different days and at different diet crude protein concentrations. An increase in uterine pH levels due to increasing protein amounts was observed but this increase was not significant among groups. Ovarian function was evaluated by ovarian responses (CL + large follicle) showed difference between groups (p < 0.05) and the lowest protein intake group gave highest ovarian response. In addition, embryo recovery rates revealed difference between groups (p < 0.05) and it was observed that the lowest ovarian response group showed the highest rates of embryo recovery. It is concluded that, in some Anatolian native sheep breeds, the application of diet flushing with different crude protein concentrates influence ovarian responses and embryo recovery rates but has no effect on BUN levels; uterus physiology or embryonic quality.

Glucogenic treatment creates an optimal metabolic milieu for the conception period in ewes

This study determined the influence of a short-term glucogenic nutritional treatment on circulating concentrations of glucose, insulin, insulin-like growth factor 1 (IGF-1), nonesterified fatty acids (NEFA), and urea, and on their correspondent levels in follicular fluid (FF) collected 12 h after the end of the treatment. After estrous synchronization with intravaginal progestagen-impregnated sponges, 20 Sarda ewes were randomly allocated into two experimental groups (GLU and WAT) and, from day 7 to day 10 (day 0 = day of sponge removal), the GLU group was gavaged with a glycogenic mixture, whereas the WAT group was gavaged with water (control group). Follicular development was stimulated by FSH administration from day 8 to 10. At day 11, ovaries were collected and follicular fluid processed. Plasma changes were assessed from day 6 to 11. In GLU group, circulating concentration of glucose (P < 0.0001), insulin (P < 0.0001), and IGF-1 (P < 0.01) rose significantly, whereas NEFA and urea concentrations decreased (P < 0.0001), as compared with controls. In particular, in FF the higher glucose concentrations found in GLU ewes compared with controls (P < 0.0001) were not accompanied by any increase in insulin and IGF-1 concentrations. NEFA (P < 0.0001) and urea (P < 0.0001) were lower in FF of GLU than WAT group, although NEFA clearance in the ovary proved to be less efficient than at the systemic level. No significant difference between groups was found in FF concentrations of pregnancy-associated plasma protein A (a protease regulating the levels of free IGF-1 in follicles), glutathione, and in its total antioxidant capacity. These results suggest that glycogenic mixture administration creates a suitable follicular microenvironment for the conception period in dairy ewes.

Nutritional effects on foetal growth

The emphasis in nutritional studies on foetal growth has now moved from the last trimester of pregnancy, when most of the increase in foetal size takes place, to earlier stages of pregnancy that coincide with foetal organogenesis and tissue hyperplasia. At these stages absolute nutrient requirements for foetal growth are small but foetal metabolic activity and specific growth rate are high. It is thus a time when nutrient supply interacts with maternal factors such as size, body condition and degree of maturity to influence placental growth and set the subsequent pattern of nutrient partitioning between the gravid uterus and maternal body.

Throughout pregnancy the maternal diet controls foetal growth both directly, by supplying essential nutrients and indirectly, by altering the expression of the maternal and foetal endocrine mechanisms that regulate the uptake and utilization of these nutrients by the conceptus. Nutritional effects on the endocrine environment of the embryo during the early stages of cell division can alter the subsequent foetal growth trajectory and size at birth; so too can current in vitro systems for oocyte maturation and embryo culture up to the blastocyst stage. There is increasing evidence that subtle alterations in nutrient supply during critical periods of embryonic and foetal life can impart a legacy of growth and developmental changes that affect neonatal survival and adult performance. Identifying the specific nutrients that programme these effects and understanding their mode of action should provide new management strategies for ensuring that nutritional regimens from oocyte to newborn are such that they maximize neonatal viability and enable animals to express their true genetic potential for production.

Effect of rumen degradable protein with or without fermentable carbohydrate supplementation on blood metabolites and embryo survival in cattle

High intakes of dietary protein, particularly rumen degradable protein (RDP), lead to elevations in systemic concentrations of ammonia and (or) urea and these may be increased further if associated with inadequate fermentable energy intake. High systemic concentrations of ammonia and urea have been associated with reduced reproductive performance in cattle. The objective of this study was to examine the effect of RDP and fermentable energy intake on a range of blood metabolites and on embryo survival in heifers. Oestrous synchronized, nulliparous beef heifers (no. = 162) were randomly assigned in a 2 ✕ 2 factorial designed experiment to two levels of RDP and two levels of fermentable energy. Grass silage-based diets were supplemented with either 0 (0U) or 240 (240U) g dietary urea (460 g/kg N) and these in turn with either 0 (0P) or 3 (3P) kg dry matter of molassed sugar-beet pulp pellets (MSBP) per day. The four treatments were, therefore, (1) 0U + 0P (no. = 43), (2) 0U + 3P (no. = 44), (3) 240U + 0P (no. = 40) (4) 240U + 3P (no. = 35), respectively. Systemic concentrations of ammonia, urea, insulin, glucose and progesterone were measured. Heifers were given artificial insemination (AI) and embryo survival measured by ultrasonography at 30 and again at 40 days after AI. Systemic ammonia and urea were elevated (P < 0·001) in the animals given the high RDP diets. Supplementation with MSBP reduced systemic urea in the heifers on both high and low RDP diets. Plasma ammonia concentrations were not affected by MSBP supplementation (P > 0·05). Plasma glucose was not affected by urea or MSBP treatment (P > 0·05) but was affected by day and time of sampling (P > 0·05). Plasma concentration of insulin was not affected by urea or MSBP supplementation or by day or time of sampling (P > 0·05). Plasma concentration of progesterone was not affected by diet or time of sampling (P > 0·05). The overall embryo survival rate was 62% and was not affected by dietary urea or fermentable carbohydrate or by systemic concentrations of ammonia, urea, glucose, insulin or progesterone (P > 0·05).

The effects of dietary urea on embryo development in superovulated donor ewes and on early embryo survival and development in recipient ewes

The aim was to examine the effect of dietary urea on yield and quality of embryos in superovulated donor ewes, and on embryo survival in recipient ewes. Ewes (25 donors and 34 recipients) were offered 1·25 kg of grass meal containing 50 g urea per ewe per day on a group basis; the remaining ewes (30 donors and 32 recipients) received 1·25 kg untreated grass meal per day. After 5 days, ewes were synchronized using a progestagen pessary for 14 days and stimulated with pregnant mare serum gonadotropin. Donors were naturally mated; recipients were detected in oestrus using vasectomized rams. On day 4 following the onset of oestrus, embryos were recovered from donors, graded morphologically and cell number counted. Two embryos of acceptable morphological grade (≥ eight cells on day 4) were then surgically transferred to recipient ewes. Recipients were slaughtered between days 34 and 36 post oestrus. The mean number of embryos recovered per ewe [3·68 (s.e. 0·41) v. 3·83 (s.e. 0·45)] was not different between untreated and urea-treated ewes, respectively. However, urea treatment of donor ewes reduced the mean cell number per embryo (10·27 (s.e. 0·27) v. 8·17 (s.e. 0·29) for untreated and urea-treated donor ewes, respectively, P < 0·001). Similarly, the percentage of embryos recovered that had ≥ 10 cells and their mean cell number was reduced following urea treatment of donor ewes (82/113 (73%) v. 39/93 (42%), P < 0·01 and 11·61 (s.e. 0·20) v. 10·41 (s.e. 0·29), P < 0·001) for untreated and urea-treated ewes, respectively. The diet offered to recipient ewes had no effect on the number of ewes confirmed pregnant (24/32 (75%) v. 28/34 (82%)) or on embryo survival following transfer (45/64 (70%) v. 51/68 (75%) for untreated and urea-treated ewes, respectively, P > 0·05). Excess nonprotein nitrogen in the form of dietary urea reduced embryo quality. However, embryo survival in recipient ewes was not affected when good quality embryos were transferred. This suggests that the deleterious effects of excess dietary urea are due to alterations to the oocyte and (or) the oviductal environment rather than changes in the uterine environment.

Nutritional effects on ovulation, embryo development and the establishment of pregnancy in ruminants

The effects of high and low dietary dietary intake on reproduction in female cattle and sheep will be considered at the level of the pituitary gland, ovary and uterus. In sheep, increased dietary intake for a relatively short time will increase ovulation rate, by increasing gonadotropin secretion. Dietary intake can affect steroids such as progesterone and also intra-follicular concentrations of some growth factors such as IGF-1 and IGF-2. The effects of altered energy intake on gonadotropins and steroids in cattle are not as repeatable as those in sheep but follicular growth rates can be altered. High nutrition has a negative effect on oocyte quality, with animals onad-libitumhigh energy diets particularly at risk. Overfeeding can decrease embryo quality in both sheep and cattle and it appears that this results from changes primarily at the level of the follicle or oocyte. Restricted nutrition for a short time will enhance pregnancy rates in cattle; most of this benefit appears to occur if food is restricted before insemination. Thus feeding levels before mating are particularly important to subsequent reproductive success. High dietary crude protein may decrease pregnancy rate in lactating cows. In ewes and heifers supplementation with urea failed to have any effect on pregnancy rates when good quality embryos were transferred to recipient animals exposed to high dietary crude protein. In donor ewes there were adverse effects on early embryo development following urea treatment, suggesting that the mechanism affecting the reproductive process was primarily operating at the level of the oocyte. Collectively, these data identify the overall deleterious effects of high dietary intake and excess crude protein on fertility and highlight the importance of dietary intake before ovulation on the likelihood of establishing a viable pregnancy.

Effect of pasture crude protein and fermentable energy supplementation on blood metabolite and progesterone concentrations and on embryo survival in heifers

Seasonal milk production systems rely on heavy inputs of nitrogenous fertilizer, which typically generate pastures with a high crude protein (CP) and low fermentable energy concentration. High intake of CP, particularly in association with low rumen fermentable energy, increases systemic ammonia and urea and has been associated with reduced fertility in cattle. The objective of this study was to examine the relationship between pasture protein intake and fermentable energy supplementation on a range of blood metabolites and on embryo survival and development in cattle.

Oestrous synchronized, nulliparous beef heifers (no. = 175) were randomly assigned to one of four pasture-based dietary treatments in a 2✕2 factorial study carried out over 2 years. Animals were randomly allocated to either high (85 kg nitrogen (N) per ha; HN) or low (0·0 kg N per ha; LN) N fertilized pastures and within pasture treatment were randomly allocated to receive either zero or three (+3P) kg dry matter (DM) of molassed sugar-beet pulp (MSBP) per head per day as follows: (1) HN (no. = 44), (2) HN + 3P, (no. = 43), (3) LN (no. = 44), (4) LN + 3P (no. = 44). Blood samples were collected to measure systemic concentrations of ammonia, urea, insulin, glucose and progesterone. Heifers were artificially inseminated (AI) and pregnancy diagnosis was carried out by ultrasonography 30 days after AI. Subgroups of pregnant animals across treatments were slaughtered 40 days after AI to estimate conceptus development.

The HN pasture had a higher CP (P< 0·001) and lower water-soluble carbohydrate (P< 0·01) concentration. Plasma concentrations of ammonia (P< 0·05) and urea (P< 0·001) were higher in the animals on the HN pastures and were reduced (P< 0·05) by MSBP supplementation, but only in animals on the HN pastures. Embryo survival rate across treatments was high overall (71%) and not related to pasture CP concentration, fermentable energy supplementation or systemic concentrations of ammonia, urea, glucose or insulin. There was no relationship between dietary treatment or systemic metabolites and any of the estimates of conceptus development. Systemic insulin was not affected by pasture N treatment or MSBP supplementation (P> 0·05). Systemic concentrations of glucose were not affected by pasture N treatment (P> 0·05) but were increased by MSBP supplementation (P< 0·05). Systemic progesterone was not affected by pasture CP or MSBP supplementation (P> 0·05) but at day 7 after AI was positively related (P< 0·05) to embryo survival. Intake of high CP herbage elevated systemic ammonia and urea but there was no association with embryo survival rate or embryo development in heifers.

Relationships between Circulating Urea Concentrations and Endometrial Function in Postpartum Dairy Cows

Simple Summary

Dairy cows fed high levels of protein to increase milk yield tend to have reduced fertility but the reasons behind this are unclear. Differing dietary protein levels are reflected in altered urea concentrations in both blood and other tissues including the uterus. We showed that the circulating urea concentration was highly correlated to changed expression levels of many genes in the endometrium shortly after calving. These were predominantly associated with tissue repair, innate immunity and lipid metabolism. A subsequent study found no effect of altered urea concentration on endometrial gene expression in vitro implying that the dietary influence is indirect.

Abstract

Both high and low circulating urea concentrations, a product of protein metabolism, are associated with decreased fertility in dairy cows through poorly defined mechanisms. The rate of involution and the endometrial ability to mount an adequate innate immune response after calving are both critical for subsequent fertility. Study 1 used microarray analysis to identify genes whose endometrial expression 2 weeks postpartum correlated significantly with the mean plasma urea per cow, ranging from 3.2 to 6.6 mmol/L. The biological functions of 781 mapped genes were analysed using Ingenuity Pathway Analysis. These were predominantly associated with tissue turnover (e.g., BRINP1, FOXG1), immune function (e.g., IL17RB, CRISPLD2), inflammation (e.g., C3, SERPINF1, SERPINF2) and lipid metabolism (e.g., SCAP, ACBD5, SLC10A). Study 2 investigated the relationship between urea concentration and expression of 6 candidate genes (S100A8, HSP5A, IGF1R, IL17RB, BRINP1, CRISPLD2) in bovine endometrial cell culture. These were treated with 0, 2.5, 5.0 or 7.5 mmol/L urea, equivalent to low, medium and high circulating values with or without challenge by bacterial lipopolysaccharide (LPS). LPS increased S100A8 expression as expected but urea treatment had no effect on expression of any tested gene. Examination of the genes/pathways involved suggests that plasma urea levels may reflect variations in lipid metabolism. Our results suggest that it is the effects of lipid metabolism rather than the urea concentration which probably alter the rate of involution and innate immune response, in turn influencing subsequent fertility.

The effects of chemical and physical factors on mammalian embryo culture and their importance for the practice of assisted human reproduction

BACKGROUND

Although laboratory procedures, along with culture media formulations, have improved over the past two decades, the issue remains that human IVF is performed in vitro (literally 'in glass').

METHODS

Using PubMed, electronic searches were performed using keywords from a list of chemical and physical factors with no limits placed on time. Examples of keywords include oxygen, ammonium, volatile organics, temperature, pH, oil overlays and incubation volume/embryo density. Available clinical and scientific evidence surrounding physical and chemical factors have been assessed and presented here.

RESULTS AND CONCLUSIONS

Development of the embryo outside the body means that it is constantly exposed to stresses that it would not experience in vivo. Sources of stress on the human embryo include identified factors such as pH and temperature shifts, exposure to atmospheric (20%) oxygen and the build-up of toxins in the media due to the static nature of culture. However, there are other sources of stress not typically considered, such as the act of pipetting itself, or the release of organic compounds from the very tissue culture ware upon which the embryo develops. Further, when more than one stress is present in the laboratory, there is evidence that negative synergies can result, culminating in significant trauma to the developing embryo. It is evident that embryos are sensitive to both chemical and physical signals within their microenvironment, and that these factors play a significant role in influencing development and events post transfer. From the viewpoint of assisted human reproduction, a major concern with chemical and physical factors lies in their adverse effects on the viability of embryos, and their long-term effects on the fetus, even as a result of a relatively brief exposure. This review presents data on the adverse effects of chemical and physical factors on mammalian embryos and the importance of identifying, and thereby minimizing, them in the practice of human IVF. Hence, optimizing the in vitro environment involves far more than improving culture media formulations.

Reproductive performance in ewes fed varying levels of cut lucerne pasture around conception

Elevated intakes of protein and energy may increase embryo mortality, but it is not clear whether fresh lucerne (Medicago sativa) pasture poses a risk. A two-year pen study using oestrous synchronised and artificially inseminated Merino ewes (n=175 in 2013 and 215 in 2014) evaluated whether feeding freshly cut lucerne pasture (mean crude protein 19.7%, metabolisable energy 9.4MJ/kg DM) at maintenance or ad libitum during different periods around insemination altered reproductive performance in comparison with ewes fed a Control diet (mean crude protein 7.8%, metabolisable energy 9.0MJ/kg DM) of pelleted faba bean hulls and oat grain hulls at maintenance. The proportion of pregnant ewes carrying multiple fetuses was reduced (P=0.026) when ewes were fed lucerne ad libitum between days 0 and 17 after insemination compared with the Control diet (0.18 and 0.34, respectively), but not when ewes were fed lucerne ad libitum between days 0 and 7 after insemination (0.22). Reproductive performance, including the proportion of ewes pregnant and the proportion with multiple fetuses, was not different (P>0.05) when ewes were fed lucerne at maintenance between days 0 and 7 compared with the Control diet. While reproductive performance was similar when ewes were fed lucerne at maintenance between 0 and 17 days after artificial insemination compared with pellets at maintenance, fetal numbers per pregnant ewe were reduced by feeding lucerne ad libitum after insemination.

Impact of maternal malnutrition during the periconceptional period on mammalian preimplantation embryo development

During episodes of undernutrition and overnutrition the mammalian preimplantation embryo undergoes molecular and metabolic adaptations to cope with nutrient deficits or excesses. Maternal adaptations also take place to keep a nutritional microenvironment favorable for oocyte development and embryo formation. This maternal-embryo communication takes place via several nutritional mediators. Although adaptive responses to malnutrition by both the mother and the embryo may ensure blastocyst formation, the resultant quality of the embryo can be compromised, leading to early pregnancy failure. Still, studies have shown that, although early embryonic mortality can be induced during malnutrition, the preimplantation embryo possesses an enormous plasticity that allows it to implant and achieve a full-term pregnancy under nutritional stress, even in extreme cases of malnutrition. This developmental strategy, however, may come with a price, as shown by the adverse developmental programming induced by even subtle nutritional challenges exerted exclusively during folliculogenesis and the preimplantation period, resulting in offspring with a higher risk of developing deleterious phenotypes in adulthood. Overall, current evidence indicates that malnutrition during the periconceptional period can induce cellular and molecular alterations in preimplantation embryos with repercussions for fertility and postnatal health.

The effect of hyperammonemia on myostatin and myogenic regulatory factor gene expression in broiler embryos

Myogenesis is facilitated by four myogenic regulatory factors and is significantly inhibited by myostatin. The objective of the current study was to examine embryonic gene regulation of myostatin/myogenic regulatory factors, and subsequent manipulations of protein synthesis, in broiler embryos under induced hyperammonemia. Broiler eggs were injected with ammonium acetate solution four times over 48 h beginning on either embryonic day (ED) 15 or 17. Serum ammonia concentration was significantly higher (P<0.05) in ammonium acetate injected embryos for both ED17 and ED19 collected samples when compared with sham-injected controls. Expression of mRNA, extracted from pectoralis major of experimental and control embryos, was measured using real-time quantitative PCR for myostatin, myogenic regulatory factors myogenic factor 5, myogenic determination factor 1, myogenin, myogenic regulatory factor 4 and paired box 7. A significantly lower (P<0.01) myostatin expression was accompanied by a higher serum ammonia concentration in both ED17 and ED19 collected samples. Myogenic factor 5 expression was higher (P<0.05) in ED17 collected samples administered ammonium acetate. In both ED17 and ED19 collected samples, myogenic regulatory factor 4 was lower (P⩽0.05) in ammonium acetate injected embryos. No significant difference was seen in myogenic determination factor 1, myogenin or paired box 7 expression between treatment groups for either age of sample collection. In addition, there was no significant difference in BrdU staining of histological samples taken from treated and control embryos. Myostatin protein levels were evaluated by Western blot analysis, and also showed lower myostatin expression (P<0.05). Overall, it appears possible to inhibit myostatin expression through hyperammonemia, which is expected to have a positive effect on embryonic myogenesis and postnatal muscle growth.

The effect of periconceptional undernutrition of sheep on the cognitive/emotional response and oocyte quality of offspring at 30 days of age

Maternal periconceptional undernutrition is associated with altered development and increased risks of adverse outcomes in the offspring. This circumstance is normal in flocks under extensive farming systems, which depend on natural forage resources. The aim of this study was to determine the effect of periconceptional undernutrition in sheep on behavioral and reproductive aspects of the offspring. Eighty ewes were synchronized in estrus and allocated to two groups (n=40) to be fed diets that provided 1.5 (C) or 0.5 (L) times the requirements for maintenance. Ewes were mated and 7 days later fed the control diet until lambing. One month after lambing, 32 lambs were exposed to tests to determine their cognitive and emotional responses. Six ewe lambs were euthanized and in vitro maturation and fertilization procedures were performed. L ewes presented a significant reduction in prolificacy and fecundity (P<0.05) in comparison with C ewes. Mean LW at lambing of L lambs was significantly higher than C lambs (C: 3.80 ± 0.11; L: 4.24 ± 0.15 kg, P<0.05). Lambs born from C ewes spent more time walking than L lambs (P<0.05) in the isolation test, revealing a decrease in the locomotor activity of lambs born from undernourished ewes around conception. Ewe lambs from the undernourished ewes presented a total population of oocytes 2.3 times higher than ovaries from control ewe lambs (60.0 ± 7.8 v. 140.0 ± 18.5 oocytes; P<0.05). In conclusion, periconceptional undernutrition is able to produce an increment in the body weight and the oocyte population, and an alteration of the locomotor activity of the offspring.

Effect of body condition and season on yield and quality ofin vitroproduced bovine embryos

The aim of our study was to examine the effects of cow's body condition score (BCS; scale 1–5) and season on the quality of bovinein vitroproduced embryos. The proportion of good quality oocytes (Q1 and Q2) was higher (P< 0.05) in the BCS 2 (57.60%) and BCS 3 (60.90%) groups compared with the BCS 1 (43.60%) group. There were no statistical differences in embryo cleavage and blastocyst rate among the BCS groups. The highest total cell number (TCN, DAPI stain) of blastocysts (P< 0.05), recorded in BCS 1 (122.27 ± 6.90) in comparison with BCS 2 (101.8 ± 3.60) or BCS 3 (105.44 ± 3.70) groups, was related to higher dead cell (DCI, TUNEL) index in this group (7.07%) when compared with BCS 2 (6.54%) or BCS 3 (6.06%), respectively. The yield of good quality oocytes during spring was lower (P< 0.05) compared with the summer season. There were significant differences (P< 0.05) in maturation and cleavage rates between autumn and summer (73.42%, 76.2% vs. 85.0%, 41.8%, respectively). The highest (P< 0.01) blastocyst rate was noted during spring and summer months. Significant difference (P< 0.05) in the TCN among spring (99.38 ± 3.90), autumn (110.1 ± 4.58) or summer (108.96 ± 3.52) was observed. The highest proportion of embryos with the best (grade I) actin cytoskeleton (phalloidin–TRITC) quality was noted during the summer months. Our results indicate that body condition affects the initial quality of oocytes, but does not affect embryo cleavage, blastocyst rate and actin quality. This finding may suggest that developmentin vitrocan mask the influence of BCS. The season affects yield and quality of blastocysts in the way that the autumn period is more favorable for embryo development.

Impact of the periconceptional environment on the programming of adult disease

The periconceptional period of mammalian development has been identified as an early 'developmental window' during which environmental conditions may influence the pattern of future growth and physiology. Studies in humans and animal models have revealed that factors such as maternal nutritional status or in vitro culture and manipulation of developing gametes and preimplantation embryos can impact upon the long-term health and physiology of the offspring. However, the mechanisms involved in the programming of adult disease in response to altered periconceptional development require increased investigation. The role of epigenetic modifications to DNA and chromatin organisation has been identified as a likely mechanism through which environmental perturbations can affect gene expression patterns resulting in phenotypic change. This study will highlight the sensitivity of two critical stages in early mammalian development, gametogenesis and preimplantation development. We will detail how changes to the immediate environment can not only impact upon developmental processes taking place at that time, but can also affect long-term aspects of offspring health and physiology. We will also discuss the emerging role of epigenetics as a mechanistic link between the environment and the later phenotype of the developing organism.

Parental diet, pregnancy outcomes and offspring health: metabolic determinants in developing oocytes and embryos

The periconceptional period, embracing the terminal stages of oocyte growth and post-fertilisation development up to implantation, is sensitive to parental nutrition. Deficiencies or excesses in a range of macro- and micronutrients during this period can lead to impairments in fertility, fetal development and long-term offspring health. Obesity and genotype-related differences in regional adiposity are associated with impaired liver function and insulin resistance, and contribute to fatty acid-mediated impairments in sperm viability and oocyte and embryo quality, all of which are associated with endoplasmic reticulum stress and compromised fertility. Disturbances to maternal protein metabolism can elevate ammonium concentrations in reproductive tissues and disturb embryo and fetal development. Associated with this are disturbances to one-carbon metabolism, which can lead to epigenetic modifications to DNA and associated proteins in offspring that are both insulin resistant and hypertensive. Many enzymes involved in epigenetic gene regulation use metabolic cosubstrates (e.g. acetyl CoA and S-adenosyl methionine) to modify DNA and associated proteins, and so act as 'metabolic sensors' providing a link between parental nutritional status and gene regulation. Separate to their genomic contribution, spermatozoa can also influence embryo development via direct interactions with the egg and by seminal plasma components that act on oviductal and uterine tissues.

Fertility and growth of nulliparous ewes after feeding red clover silage with high phyto-oestrogen concentrations

The study aimed to determine the effects of red clover (Trifolium pratense) silage with high phyto-oestrogen content on ewe performance during their first breeding season. Red clover silage containing formononetin, biochanin A, genistein, and daidzein was fed to 10 nulliparous ewes of the prolific Finnish Landrace breed before, during and after the breeding season, for a total of 5 months. A control group of 10 ewes was fed with grass silage. The mean numbers of foetuses per pregnancy were 2.1±0.7 and 2.2±0.8 for the red clover and control groups, respectively. The total mass of the uterus with its contents was significantly greater in ewes of the red clover group compared with those of the control group. This difference was mainly explained by the greater volume of foetal fluids. Serum progesterone concentration in the red clover group was significantly lower over the entire period analysed than in the control group. In conclusion, the fecundity of the ewes was not reduced by red clover feed with high phyto-oestrogen concentrations. The volume of foetal fluids increased that could increase the risk for vaginal prolapse before the term.

The effect of peri-conceptual grazing of live pasture on fetal numbers in unsynchronised ewes

Methods of increasing the number of lambs born per ewe that avoid the use of pharmaceutical methods of oestrus synchronisation but which require a short period of increased nutrition are desirable. Four separate experiments evaluated whether peri-conceptual grazing of lucerne, compared with senescent herbage or other live herbage, increased fetal numbers in unsynchronised ewes. Merino ewes that grazed lucerne pasture for 7 days before joining and for the first 7 days of a 5–6-week joining produced up to 21 extra (P < 0.05) fetuses per 100 ewes joined, compared with ewes grazing cereal stubble with minimal live herbage (Experiment 2). In Experiments 1, 3 and 4, Merino or First Cross ewes grazing either cereal stubbles or phalaris pasture with as little as 200 kg DM/ha of live herbage produced a similar (P > 0.05) number of fetuses per ewe joined as those grazing on lucerne, either because this quantity of live feed was sufficient to increase fetal numbers, or because, for Experiment 3, First Cross ewes may not have responded at the commencement of the breeding season. It is concluded that grazing live pasture for 7 days before joining and for the first 7 days of joining during the breeding season can substantially increase fetal numbers in unsynchronised ewes compared with ewes grazing stubbles containing no live herbage. The response appears to occur on a range of plant species, and a small quantity of live herbage can elicit a response. Grazing lucerne in the peri-conceptual period did not increase (P > 0.05) the proportion of non-pregnant ewes. Further studies are required to determine how early in the breeding season ewes with a distinct breeding season will respond to nutritional manipulation.

Incidence of abnormal offspring from cloning and other assisted reproductive technologies

In animals produced by assisted reproductive technologies, two abnormal phenotypes have been characterized. Large offspring syndrome (LOS) occurs in offspring derived from in vitro cultured embryos, and the abnormal clone phenotype includes placental and fetal changes. LOS is readily apparent in ruminants, where a large calf or lamb derived from in vitro embryo production or cloning may weigh up to twice the expected body weight. The incidence of LOS varies widely between species. When similar embryo culture conditions are applied to nonruminant species, LOS either is not as dramatic or may even be unapparent. Coculture with serum and somatic cells was identified in the 1990s as a risk factor for abnormal development of ruminant pregnancies. Animals cloned from somatic cells may display a combination of fetal and placental abnormalities that are manifested at different stages of pregnancy and postnatally. In highly interventional technologies, such as nuclear transfer (cloning), the incidence of abnormal offspring continues to be a limiting factor to broader application of the technique. This review details the breadth of phenotypes found in nonviable pregnancies, together with the phenotypes of animals that survive the transition to extrauterine life. The focus is on animals produced using in vitro embryo culture and nuclear transfer in comparison to naturally occurring phenotypes.

Effect of nutrition on plasma lipid profile and mRNA levels of ovarian genes involved in steroid hormone synthesis in Hu sheep during luteal phase

Ovarian steroid hormones regulate follicular growth and atresia. This study aims to determine whether key ovarian sterol-regulatory genes are differentially expressed in Hu sheep under different short-term nutritional regimens. Estrus was synchronized using intravaginal progestagen sponges. The ewes were assigned randomly to 3 groups. On d 6 to 12 of their estrous cycle, the control (CON) group received a maintenance diet (1.0×M), the supplemented (SUP) group received 1.5×M, and the restricted (R) group received 0.5×M. On d 7 to 12, blood samples were taken. The sheep were slaughtered at the end of the treatment, and their organs and ovaries were collected. The plasma concentrations of urea (P<0.01), total cholesterol (P<0.01), low-density lipoprotein cholesterol (P<0.01), NEFA (P<0.01), FSH (P<0.05), and estradiol (P<0.05) increased with decreasing dietary intake, whereas plasma triglyceride (P<0.01) and triiodothyronine (T3) concentrations decreased (P<0.05). The ewes in the R group had higher spleen weight and percentage of spleen to BW and lower liver and small intestine weights and percentage of liver/stomach to BW than the SUP group ewes (P<0.05). Nutritional restriction decreased the cytochrome p450 (CYP17A1) and estrogen receptor 1 (ESR1) mRNA expression (P<0.05) and increased the cytochrome p450 aromatase (CYP19A1) mRNA expression (P<0.05) in follicles>2.5 mm. Follicle size affected the mRNA expression of very low density lipoprotein receptor (VLDLR), estrogen receptor 2 (ESR2), FSH receptor (FSHR), CYP17A1, and CYP19A1 (P<0.05). In conclusion, we suggest that a potential mechanism by which short-term negative energy balance inhibits follicular growth may involve responses to disrupted reproductive hormone concentrations and influenced the intrafollicular expression of CYP17A1, CYP19A1, and ESR1. This result may be due to increased plasma urea and lipid concentrations.