Effects of Heat-Stress on Oocyte Number and Quality and In Vitro Embryo Production in Holstein Heifers

Background: This study aimed to determine the effects of environmental temperature on the number and quality of oocytes and embryo production rates obtained by performing ovum pick up (OPU). Heat stress leads to long-term, short-term, visible, and invisible effects in dairy cows. Its effects on reproduction are evident in all stages, from oocyte development to birth. Disturbance in ovarian follicle development, follicular dominance deficiency, anoestrus, polyspermia, embryoniclosses, decreased fetal growth, and abortion are some examples of responses to these effects. The aim of the present study was aimed to determine the effects of ambient temperature on oocyte quality and number and embryo production rates.Materials, Methods & Results: The animal material used in this study comprised 10 Holstein heifers. At the beginning of the study, the heifers were 13-15 months old. OPU was performed at different times of the year, and weather conditions were recorded. Grouping according to ambient temperature was done as < 10°C (group 1), 10-25°C (group 2), and > 25°C (group 3). The veterinary ultrasonography device and a set of compatible intravaginal OPU probe, catheter, and aspiration device were used for OPU application. All antral follicles with diameters of 2-8 mm in the ovaries were aspirated. The aspirated follicle fluids were examined under a stereo microscope, and the cumulus-oocyte complexes (COC) were collected and classified according to their structure. A, B, and C-quality oocytes were included in the in vitro embryo production process. After performing 69 OPUs on random days of the cycle, the number of oocytes per OPU was found to be 8.72, 6.32, and 6.85 in groups 1, 2, and 3, respectively (P < 0.05). The number of viable oocytes per OPU was 6.83, 4.64, and 4.65 in groups 1, 2, and 3, respectively (P < 0.05). The statistical difference between the first group and the other groups was significant for cleavage and blastocyst counts (P < 0.05).Discussion: All the negative effects of heat stress on animals resulted from the increased body temperature. Reproductive performance is adversely affected by high temperatures and humidity during periods of high ambient temperatures. Metabolic heat is released, and the heat load increases due to the metabolism of nutrients in cattle. Internal body temperature is regulated via the dissipation of metabolic heat to the environment. The amount of heat dissipated via conduction andconvection depends on the unit body weight, surface area, skin and coat color, difference in temperature gradient of the animal and ambient temperature, and humidity. In the present study, it was determined that the blastocyst development rates of the oocytes obtained in the warm season (>25°C [group 3]) were lower than those of the other groups. It was concluded that this may be because the oocytes developed under chronic heat stress in the animals, and several cycles were required to enhance oocyte quality and developmental potential. Additional studies are needed to investigate the response of oocytes obtained with OPU to heat stress during embryonic developmental stages and to determine the sensitivity and effects of embryonic tissue damage according to developmental stages. Based on the results of the present study, it was concludedthat performing OPU and in vitro embryo production (IVEP) when the ambient temperature is close to the thermoneutral limits may increase the blastocyst development rates. Keywords: blastocyst, heat stress, heifer, in vitro embryo production, oocyte quality, ovum pick-up

Determination of the Effect of Different Doses of ECG Applications on Reproductive Parameters in Primiparous Akkaraman Kangal Sheep

To increase meat production at a level parallel to meet the demand of the increasing world population in recent years, reproductive management in farm animals must be successful. In order to reach the desired level of fertility in sheep, particularly starting with the non-prolific breeds, anoestrus period applications should be carried out effectively. In this study, different doses of equine chorionic gonadotropin were applied to determine the effective eCG dose for underwent estrus synchronization with progesterone in anoestrus Kangal ewes whose milk and wool yield has been completely abandoned by the breeder for various reasons and whose only economic benefit is lamb production. A total of 225 Kangal Akkaraman Sheep breeds, 2 years old, with a body condition score of 2.5-3.5 and an average weight of 40-50 kg, were included in the study. In line with this purpose, ewes were divided into 3 groups, containing 75 primiparous sheep. A vaginal sponge containing progesterone was inserted into the animals in all groups on day 0. Seven days after this application (on the 7th day), vaginal sponges were removed and Prostaglandin F2α (PGF2α) was applied. When the vaginal sponge was removed and the PGF2α was administered, 400 IU of eCG was given to animals in Group 1 (n:75), 500 IU of eCG was administrated to animals in Group 2 (n:75), and 600 IU of eCG was injected to the ewes in Group 3. The effectiveness of different doses of eCG application on reproductive parameters such as estrous rate, pregnancy rate, multiple pregnancy rate, and the number of offspring was evaluated. While no statistical difference could be determined between the groups in terms of the stated reproductive parameters, numerically more offspring were obtained in the group in which eCG was applied at a low rate (Group 1). In the light of this information, it is concluded that 400 IU eCG can be as effective as 600 IU eCG in sexual stimulation of Kangal ewes in anestrus

Effects of Heat-Stress on Oocyte Number and Quality and In Vitro Embryo Production in Holstein Heifers

Background: This study aimed to determine the effects of environmental temperature on the number and quality of oocytes and embryo production rates obtained by performing ovum pick up (OPU). Heat stress leads to long-term, short-term, visible, and invisible effects in dairy cows. Its effects on reproduction are evident in all stages, from oocyte development to birth. Disturbance in ovarian follicle development, follicular dominance deficiency, anoestrus, polyspermia, embryoniclosses, decreased fetal growth, and abortion are some examples of responses to these effects. The aim of the present study was aimed to determine the effects of ambient temperature on oocyte quality and number and embryo production rates.Materials, Methods & Results: The animal material used in this study comprised 10 Holstein heifers. At the beginning of the study, the heifers were 13-15 months old. OPU was performed at different times of the year, and weather conditions were recorded. Grouping according to ambient temperature was done as < 10°C (group 1), 10-25°C (group 2), and > 25°C (group 3). The veterinary ultrasonography device and a set of compatible intravaginal OPU probe, catheter, and aspiration device were used for OPU application. All antral follicles with diameters of 2-8 mm in the ovaries were aspirated. The aspirated follicle fluids were examined under a stereo microscope, and the cumulus-oocyte complexes (COC) were collected and classified according to their structure. A, B, and C-quality oocytes were included in the in vitro embryo production process. After performing 69 OPUs on random days of the cycle, the number of oocytes per OPU was found to be 8.72, 6.32, and 6.85 in groups 1, 2, and 3, respectively (P < 0.05). The number of viable oocytes per OPU was 6.83, 4.64, and 4.65 in groups 1, 2, and 3, respectively (P < 0.05). The statistical difference between the first group and the other groups was significant for cleavage and blastocyst counts (P < 0.05).Discussion: All the negative effects of heat stress on animals resulted from the increased body temperature. Reproductive performance is adversely affected by high temperatures and humidity during periods of high ambient temperatures. Metabolic heat is released, and the heat load increases due to the metabolism of nutrients in cattle. Internal body temperature is regulated via the dissipation of metabolic heat to the environment. The amount of heat dissipated via conduction andconvection depends on the unit body weight, surface area, skin and coat color, difference in temperature gradient of the animal and ambient temperature, and humidity. In the present study, it was determined that the blastocyst development rates of the oocytes obtained in the warm season (>25°C [group 3]) were lower than those of the other groups. It was concluded that this may be because the oocytes developed under chronic heat stress in the animals, and several cycles were required to enhance oocyte quality and developmental potential. Additional studies are needed to investigate the response of oocytes obtained with OPU to heat stress during embryonic developmental stages and to determine the sensitivity and effects of embryonic tissue damage according to developmental stages. Based on the results of the present study, it was concludedthat performing OPU and in vitro embryo production (IVEP) when the ambient temperature is close to the thermoneutral limits may increase the blastocyst development rates. Keywords: blastocyst, heat stress, heifer, in vitro embryo production, oocyte quality, ovum pick-up