Characteristics of the oestrous cycle of Iberian red deer (Cervus elaphus hispanicus) assessed by progesterone profiles

Exogenous Melatonin Improves the Reproductive Outcomes of Yearling Iberian Red Deer (Cervus elaphus hispanicus) Hinds

Simple Summary

Increasing the reproductive performance of hinds is considered to be a key factor of overall farm deer productivity. In the case of yearling hinds, this aspect becomes more important, as a delay in the pubertal onset will compromise the reproductive performance of the entire herd (decreased fertility), and these yearling hinds will carry this ‘late’ condition throughout their reproductive life. The aim of this study was to explore the use of melatonin implants on yearling Iberian red deer (Cervus elaphus hispanicus) hinds to improve their fertility outcomes, advance the calving date and the calves’ weight, and to prevent the negative impact of yearling hinds’ low liveweight on their reproductive outcomes. Melatonin implants (18 mg), administered three-fold (two implants each time) every 30 days before the breeding season, rendered significantly higher fertility rates (regardless of the yearling hind’s weight) and heavier calves, and advanced the calving date in the yearling hinds by 15 days compared to non-treated hinds. In addition, halving the number of yearling hinds that received melatonin provided a similar benefit to a large-scale treatment of the whole herd, which indicates female-to-female stimulation of the ovarian activity. Taken together, this protocol for melatonin treatment simplifies its administration, reduces its costs, and assures the enhancement of the reproductive productivity of the entire farm.

Abstract

The aim of this study was to assess the effect of melatonin implants on the reproductive performance of yearling Iberian red deer (Cervus elaphus hispanicus) hinds. It also explored exogenous melatonin administration as a tool to minimize the negative effect of a low yearling hind’s liveweight on their reproductive efficiency. In addition, the effect of melatonin-treated yearling hinds on non-treated hinds was studied in order to provide a practical and economical protocol to improve farms’ productivity. A total of 4520 Iberian red deer hinds belonging to the same farm were included in this study. Melatonin (108 mg/hind) implants were administered three-fold every 30 days before the breeding season. Fertility rates, calves’ weights and calving dates were registered for each hind. The results showed that exogenous melatonin increased significantly (p < 0.05) the calves’ weight (32.39 ± 1.07 kg vs. 27.65 ± 1.11 kg for Weight 1_calf (July) and 46.59 ± 1.50 kg vs. 41.79 ± 1.54 kg for Weight 2_calf (August, at weaning)) and advanced the calving date by 15 days in yearling hinds compared to the non-treated group. In addition, the administration of melatonin implants before the breeding season was able to minimize the negative effect of low yearling hinds’ liveweight (Weight 1_hind) on their future reproductive outcomes, as the fertility rates increased by 46% and the calves’ weight increased by 7 kg after the melatonin treatment, regardless of the yearlings’ weight. Finally, when both experimental groups (melatonin and non-treated) were kept separate, higher fertility rates (76.73 ± 7.18% vs. 66.94 ± 7.41%) were observed for the melatonin-treated hinds compared to the non-treated hinds. However, when both groups of yearling hinds were maintained together, no significant differences were observed in their fertility outcomes (78.13 ± 21.26% vs. 78.12 ± 23.32%). Therefore, melatonin implants may be used in yearling Iberian red deer hinds as a management tool to improve their reproductive productivity.

The Effectiveness of Pharmacological Synchronization of the Estrous Cycle in Hinds (Cervus elaphus L.): A Pilot Field Trial

The aim was to estimate the effective pharmacological method of the estrous cycle synchronization by checking the effects of synchronization by measurement of progesterone (P4) and 17-beta estradiol (E2) concentration by RIA and artificial insemination. The experiment was performed at the red deer farm in Rudzie (North-East Poland; 3 year's old). The herd (N = 14) was kept away from bulls and was divided in two groups of seven animals. In the Group I, CIDR insert (0.3 g of P4) was applicated intravaginally for 12 days; a second insert replaced the first one for the next 12 days, and next 200 IU of equine chorionic gonadotropin (eCG) was injected intramuscularly (Folligon). Estrus was expected 48 h after eCG injection. In the Group II, Chronogest sponge (20 mg of flugestone acetate) was applicated intravaginally and after 7 days replaced with second chronogest sponge for 7 days. After removing the sponge, on the same day eCG was injected and estrus was expected after 48 h. Artificial insemination was provided with frozen-thawed semen twice: 12 and 24 h after expected estrus. The peripheral blood from the jugular vein was collected each time when the inserts or sponge were applicated and 40 days after insemination. The concentration of P4 and E2 in plasma was measured by RIA. The effectiveness of insemination was monitored by pregnancy-associated glycoproteins determination and observed by the number of calves born. Two pregnancies were confirmed in Group I and five in Group II based on PAG concentration. One newborn was observed in Group I and five in Group II. Both methods of synchronization are effective in hinds based on the received profile of steroids. Although the sponge shape in case of chronogest is better comparing with CIDR, which was not completely deposited in the vagina of hind, potentially leads to bacteria inflammation, and it disturbs the rightful endocrine regulation. Moreover, pregnancy rate and hormone responsiveness were better in Group II.

Antioxidative Potential of Red Deer Embryos Depends on Reproductive Stage of Hind as A Oocyte Donor

Simple Summary

Deer breeding tends to select animals for obtain the high meat quality and in case of males preferred shape and weight of antlers. Fertilization in vitro (IVF) using high-indexing parents results favorable features. Moreover, evaluation of effective method of IVF on Cervus elaphus as a model, will be useful for application on Cervids in danger of extinction. The effectivity of IVF depends on quality of gametes and proper development of embryo. The aim was to compare the blastocyst stages of red deer embryos in respect of IVF efficiency, morphology, apoptotic and proliferative abilities, and antioxidative potential according to the reproductive status of hinds. We used three experimental groups, including the ovaries collected post mortem on the 4th and 13th days of the estrous cycle (farmed animals) and during pregnancy (wild animals). Frozen-thawed epididymal semen was used for IVF. Blastocyst quality, apoptotic, and antioxidative potential of blastocysts were evaluated. Results indicate that red deer embryos on blastocyst stage received in vitro collected from hinds on 4th day of the estrous cycle as an oocyte donor are characterized by better antioxidative potential and qualities to those developed from oocytes collected from hinds on 13th day of the estrous cycle and pregnancy.

Abstract

The aim was to compare the blastocyst stages of red deer embryos in respect of in vitro fertilization (IVF) efficiency, morphology, apoptotic and proliferative abilities, and antioxidative potential according to the reproductive status of hinds. We used three experimental groups, including the ovaries collected post mortem on the 4th and 13th days of the estrous cycle and during pregnancy (n = 18). After oocyte maturation, frozen-thawed epididymal semen was used for IVF. Blastocyst quality, apoptotic potential by determining the mRNA expression of BAX, BCL-2, OCT4, SOX2, and placenta-specific 8 gene (PLAC8), and antioxidative potential of blastocysts were evaluated by determining the mRNA expression of CuSOD, MnSOD, and GPX as well as the enzymatic activity of superoxide dismutase and reduced glutathione. The highest development rate of expanded blastocyst, mRNA expression of BCL-2, OCT4, SOX2, and PLAC8 and mRNA expression and enzymatic activity of the antioxidative factors increased (p < 0.05) in blastocysts developed from the oocytes collected on the 4th day, compared to those developed from the oocytes collected on the 13th day of the cycle and during pregnancy. Our study indicates that the 4th day of the estrous cycle is the most effective period for oocyte collection for IVF and embryo development in hinds, considering quality parameters and antioxidative potential of the blastocysts.

Effects of extender type on the quality of post-thaw giant panda (Ailuropoda melanoleuca) semen

Sperm cryopreservation is an essential approach for assisted reproduction and genetic resources conservation in captive giant pandas. Cryopreservation, however, leads to a significant decrease in sperm quality and, consequently, a low fertilization rate. Therefore, it is mandatory to disclose more suitable and efficient freezing strategies for sperm cryopreservation. In the present study, we compared for the first time the performance of two commercial freeze extender (INRA96 versus TEST) freezing methods on post-thawed semen quality. Semen cryopreserved with the INRA96 showed better total motility (73.00 ± 4.84% vs 57.56 ± 3.60%, P < 0.001), membrane integrity (60.92 ± 2.27% vs 40.53 ± 2.97%, P < 0.001) and acrosome integrity (90.39 ± 2.74% vs 84.26 ± 4.27%, P < 0.05) than stored with TEST. There was no significant difference in DNA integrity after thawing between the two extenders (95.69 ± 3.60% vs 94.26 ± 4.84%). In conclusion, the INRA96 method showed to be better for giant panda sperm cryopreservation and should therefore be recommended for use in order to increase success of artificial insemination.

Plasma progesterone changes and length of oestrous cycle in Rusa Deer (Rusa timorensis)

A study was conducted to profile the plasma progesterone (P4) concentrations and establish the length of oestrous cycle in the Rusa timorensis during the breeding season. Five healthy hinds were selected for peripheral blood sampling twice weekly to gauge the P4 levels by radioimmunoassay, at the start of the breeding season indicated by rutting behaviours of sexually active males. The hinds were polyestrous as proven by the cyclic trend of P4 levels. After the presumptive oestrus indicated by the lowest P4 concentrations (0.20±0.09ng/ml), this ovarian hormone was markedly elevated on day 7 of the cycle (0.78±0.20ng/ml), reached its peak (2.61±0.23ng/ml, P<0.05) on day 14, and then declined to the basal level in the subsequent oestrus. The mean oestrous cycle length in R. timorensis during the breeding season was 19.2 days with a range of 18-21 days, and the pattern of circulating progesterone during the oestrous cycle of the R. timorensis is similar to those of other deer species. It was also observed that the length of oestrous cycle of R. timorensis determined by gauging the progesterone levels and observation of the oestrous behaviours as well as changes in the cellular pattern of vaginal epithelial cells are highly consistent.

The Application of Reproductive Technologies to Natural Populations of Red Deer

Over the past decade, there has been increasing interest in the application of reproductive technology to the conservation and management of natural populations of deer. The application of assisted reproduction technologies within natural population of deer is in its infancy. However, its future potential is enormous, particularly in relation to genetic management or conservation. This paper reviews the present state of such technologies for a wild subspecies of red deer, the Iberian red deer (Cervus elaphus hispanicus), by discussing the major components of oestrous synchronization, semen collection/cryopreservation and insemination techniques. In addition, findings made during the course of studies on natural populations have enormous potential for the understanding of novel reproductive mechanism that may not be uncovered by livestock or human studies. A summary of these results are also reviewed here.

Seasonal Endocrine Changes and Breeding Activity in Mediterranean Wild Ruminants

The methods of assisted reproduction commonly used in domestic animals are currently being applied to non-domestic species. This is because of the limitation of maintaining the genetic variability in the wild, as it occurs in wild ruminants of the Mediterranean Basin. Despite the apparent progress of the technology, success of the offspring to grow and become healthy adult individuals has remained low in wild species. Difficulties usually arise from insufficient information about basic reproductive biology, such as the seasonal changes in ovarian and testicular activity. Directional adaptive evolution involves development of speciespecific physiological reproductive patterns to cope with various environmental factors. Thus, species originating and living at the same latitude display different reproductive strategies to entrain the breeding activity at an optimal time of the year. The aim of this paper was to present current knowledge on reproductive physiology of Mediterranean wild ruminants as a basic prerequisite for the successful use of assisted reproduction methods. Special emphasis is given to seasonal endocrine changes, ovarian cycles and testicular activity of Iberian wild ruminants, together with the role of social interactions on the regulation of these events.

Compensatory extension of gestation length with advance of conception in red deer (Cervus elaphus)

Calving date in many mammals is matched to the time of greatest food availability. Out of season calving results in heavy penalties in terms of own and offspring survival or body condition. This study examined whether gestation length is affected by advancing fertilisation. Thirty-six red deer hinds (of the Iberian and Scottish subspecies) were subjected to a synchronisation treatment of oestrus, ovulation, and artificial insemination on three dates, with remaining non-pregnant females mated with an intact male in a last group. Gestation was longer the more the fertilisation was advanced; gestation lasted 241.5+/-1.3 days (d) in the first group, 237.4+/-1.2 d in the second, 235.1+/-1.3 d in the third, and 231.2+/-1.6 d in the last. Mean gestation lasted 234.2+/-0.7 d. Hinds gained less weight during gestation the more the fertilisation was advanced. The difference was due at least in part to net body weight of the hind after calving compared to that at mating, and calves did not differ in birth weight. As early born calves suffer greater mortality in the field, this enlargening of gestation might be a compensatory response of the hinds to match calving with food availability. Under natural conditions, similar small modifications of gestation length may help hinds to overcome short-term adverse conditions for calving. Because calf mortality is correlated with birth weight, hinds may have kept calf birth weight constant at the expense of greater body weight loss.