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De Rensis F, Dall’Olio E, Gnemmi GM, Tummaruk P, Andrani M, Saleri R. Interval from Oestrus to Ovulation in Dairy Cows-A Key Factor for Insemination Time: A Review. Vet Sci 2024; 11:152. [PMID: 38668419 PMCID: PMC11054615 DOI: 10.3390/vetsci11040152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Revised: 03/25/2024] [Accepted: 03/27/2024] [Indexed: 04/29/2024] Open
Abstract
This review describes the oestrus-to-ovulation interval, the possibility of predicting the time of ovulation, and the optimum time for insemination relative to oestrus in dairy cows. The duration of oestrus in dairy cows is approximately 8-20 h, with differences possibly related to the methods of oestrus detection and the frequency of observations. Most cows ovulate approximately 24-33 h after the onset of oestrus and 15-22 h after the end of oestrus. The interval from the preovulatory luteinising hormone (LH) surge to ovulation is approximately 4-30 h. Ovulation occurs when follicle diameter averages 18-20 mm. When it is possible to correctly determine the beginning of oestrus, artificial insemination can be performed utilizing the "a.m.-p.m. rule", and only one insemination may be applied. In cows with too long or too short oestrus-to-ovulation intervals, fertility can be compromised. One important factor that can alter the oestrus-to-ovulation interval is acute or chronic heat stress during the warm season. When there is a risk that insemination may occur too early or too late with respect to the time of ovulation, GnRH administration can be considered.
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Affiliation(s)
- Fabio De Rensis
- Department of Veterinary—Medical Science, University of Parma, Via del Taglio 10, 43126 Parma, Italy; (F.D.R.); (R.S.)
| | - Eleonora Dall’Olio
- Department of Veterinary—Medical Science, University of Parma, Via del Taglio 10, 43126 Parma, Italy; (F.D.R.); (R.S.)
| | - Giovanni Maria Gnemmi
- Bovinevet Internacional SL. Bovine Reproduction Ultrasonography & Herd Management Huesca (ES), 22006 Huesca, Spain;
| | - Padet Tummaruk
- Department of Obstetrics, Gynecology and Reproduction, Faculty of Veterinary Science, Centre of Excellence in Swine Reproduction, Chulalongkorn University, Bangkok 10310, Thailand;
| | - Melania Andrani
- Department of Veterinary—Medical Science, University of Parma, Via del Taglio 10, 43126 Parma, Italy; (F.D.R.); (R.S.)
| | - Roberta Saleri
- Department of Veterinary—Medical Science, University of Parma, Via del Taglio 10, 43126 Parma, Italy; (F.D.R.); (R.S.)
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Ozaki R, Inoue S, Yorozui Y, Ichikawa R, Yamada N, Higashi S, Matsuyama S, Tsukamura H, Ohkura S, Uenoyama Y, Morita Y. Capturing temperature changes on the ocular surface along with estrus and ovulation using infrared thermography in Japanese Black cows. J Reprod Dev 2024; 70:49-54. [PMID: 38008463 PMCID: PMC10902635 DOI: 10.1262/jrd.2022-116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Accepted: 10/23/2023] [Indexed: 11/28/2023] Open
Abstract
Pre-ovulatory follicles are cooler than the neighboring reproductive organs in cows. Thus, measuring the temperature of reproductive organs could be a useful method for predicting estrus and ovulation in cows, and the establishment of a non-invasive technique is required. In this study, we used infrared thermography (IRT) to measure ocular surface temperature as a potential surrogate for reproductive organ temperature. Five Japanese Black cows with synchronized estrus were subjected to temperature measurements in five regions of the ocular surface, including the nasal conjunctiva, nasal limbus, center cornea, temporal limbus, and temporal conjunctiva, twice a day (0800 h and 1600 h) during the experimental period. The temperatures in the five regions significantly declined in cows from estrus to ovulation. To the best of our knowledge, this study is the first to use IRT to show a temperature decrease in the ocular surface along with estrus to ovulation in Japanese Black cows.
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Affiliation(s)
- Riho Ozaki
- Department of Animal Sciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan
| | - Seiji Inoue
- Department of Animal Sciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan
| | - Yuki Yorozui
- Department of Animal Sciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan
| | - Rei Ichikawa
- Department of Animal Sciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan
| | - Naoki Yamada
- Department of Animal Sciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan
| | - Seiya Higashi
- Department of Animal Sciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan
| | - Shuichi Matsuyama
- Department of Animal Sciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan
| | - Hiroko Tsukamura
- Department of Animal Sciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan
| | - Satoshi Ohkura
- Department of Animal Sciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan
| | - Yoshihisa Uenoyama
- Department of Animal Sciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan
| | - Yasuhiro Morita
- Department of Clinical Veterinary Science, Obihiro University of Agriculture and Veterinary Medicine, Hokkaido 080-8555, Japan
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De Rensis F, Saleri R, Garcia-Ispierto I, Scaramuzzi R, López-Gatius F. Effects of Heat Stress on Follicular Physiology in Dairy Cows. Animals (Basel) 2021; 11:ani11123406. [PMID: 34944184 PMCID: PMC8697862 DOI: 10.3390/ani11123406] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Revised: 11/22/2021] [Accepted: 11/26/2021] [Indexed: 12/30/2022] Open
Abstract
Simple Summary Environmentally induced hyperthermia, also called heat stress (HS), compromises reproductive physiology in mammals. The number of oocytes is fixed after birth and they are stored in the ovary in a quiescent state (at the stage of the first meiotic prophase) in primordial follicles. There is evidence that HS alters the oocyte quality, the dynamics of follicular growth and ovulation. The dairy cow, submitted to the metabolic stress of high milk production, is a good model for studying the effects of HS on ovarian function. The aim of this review is to describe the influence of HS during the stages of follicular development in dairy cattle, from the activation of primordial follicles to ovulation. Some clinical aspects are also considered. Abstract Follicular organization starts during mid-to-late fetal life with the formation of primordial follicles. The bilateral interplay between the oocyte and adjoining somatic cells during follicular growth and ovulation may be sensitive to heat stress (HS). Mechanisms giving rise to pre-ovulatory temperature gradients across reproductive tissues are mostly regulated by the pre-ovulatory follicle, and because the cooling of the gonads and genital tract depends on a counter-current transfer system of heat, HS may be considered a major factor impairing ovulation, fertilization and early embryo development. There is evidence of a long-lasting influence of HS on oogenesis and final follicular maturation. Follicular stages that are susceptible to HS have not been precisely determined. Therefore, the aim of this review was to describe the influence of HS during the staged follicular development in dairy cattle, from the activation of primordial follicles to ovulation. Some clinical prospects are also considered.
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Affiliation(s)
- Fabio De Rensis
- Department of Veterinary Sciences, University of Parma, Strada del Taglio 10, 12, 43121 Parma, Italy;
| | - Roberta Saleri
- Department of Veterinary Sciences, University of Parma, Strada del Taglio 10, 12, 43121 Parma, Italy;
- Correspondence:
| | - Irina Garcia-Ispierto
- Department of Animal Science, University of Lleida, 25198 Lleida, Spain;
- Agrotecnio Centre, 25198 Lleida, Spain;
| | - Rex Scaramuzzi
- Royal Veterinary College, London NW1 0TU, UK;
- Institute of Agriculture, University of Western Australia, Perth 6009, Australia
| | - Fernando López-Gatius
- Agrotecnio Centre, 25198 Lleida, Spain;
- Transfer in Bovine Reproduction SLu, 22300 Barbastro, Spain
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López-Gatius F, Garcia-Ispierto I, Hunter RHF. Cervix-rectum temperature differential at the time of insemination is correlated with the potential for pregnancy in dairy cows. J Reprod Dev 2021; 67:251-255. [PMID: 34053994 PMCID: PMC8423606 DOI: 10.1262/jrd.2021-022] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
This study sought to establish whether temperature gradients between the cervix, vagina, and rectum at and 7 days post-artificial insemination (AI) were associated with the incidence of
pregnancy in lactating dairy cows (Experiment I; n = 90 ovulating cows) and to evaluate temperature gradient dynamics from the time of insemination to 7 days post-AI under heat stress
conditions (Experiment II; n = 16 ovulating and 4 non-ovulating cows). In Experiment I, 39 cows (43.3%) became pregnant. The odds ratio for pregnancy was 2.5 for each one-tenth of a degree
drop in cervical temperature with reference to the control rectal temperature at the time of AI (P = 0.01), whereas the same decrease in the cervix–rectum temperature differential 7 days
post-AI resulted in an odds ratio of 0.44 (P = 0.02). In Experiment II, 5 of the ovulating cows (31.3%) became pregnant. The mean values of the vagina–rectum, vagina–cervix, and
cervix–rectum temperature differentials at AI (day 0), 8 h, 24 h, and 7 days post-AI changed significantly from day 0 to day 7 (within-subject effect; P < 0.02) in ovulating cows but not
in non-ovulating cows. Temperature differentials on days 0 and 7 were similar between ovulating cows and cows of Experiment I. Overall, our findings support the notion that a temperature
differential between the caudal cervical canal and rectum at AI may be an indicator of the likelihood of pregnancy. Possible prospects of confirming estrus at the herd-level are also
suggested.
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Affiliation(s)
- Fernando López-Gatius
- Agrotecnio Centre; University of Lleida, 25198 Lleida, Spain.,Transfer in Bovine Reproduction SLu, 22300 Barbastro, Spain
| | - Irina Garcia-Ispierto
- Agrotecnio Centre; University of Lleida, 25198 Lleida, Spain.,Department of Animal Science, University of Lleida, 25198 Lleida, Spain
| | - Ronald H F Hunter
- Sidney Sussex College, University of Cambridge, England.,3 Pleasants Steading, Oxnam, Jedburgh TD8 6QZ, Scotland
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Thermal Mechanisms Preventing or Favoring Multiple Ovulations in Dairy Cattle. Animals (Basel) 2021; 11:ani11020435. [PMID: 33567503 PMCID: PMC7915362 DOI: 10.3390/ani11020435] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 02/04/2021] [Accepted: 02/06/2021] [Indexed: 12/16/2022] Open
Abstract
Simple Summary While cows are usually monovular, the incidence of dizygous twin births has recently increased considerably alongside increasing milk production. Genetic progress and improvements in nutrition and management practices have led to a continuous increase in milk yield and thus also to multiple ovulations and twin pregnancies. Twin pregnancies are undesirable as they seriously compromise the welfare of the cow and herd economy. A better understanding of the processes associated with multiple ovulations should help to reduce rates of twinning. During the stages of the sexual cycle, temperature gradients are established within the ovary and throughout the genital tract. Pre-ovulatory local cooling of the reproductive system favors male and female gamete maturation and subsequent fertilization. In fact, thermal mechanisms may prevent or favor multiple ovulations and thus twinning. The purpose of this review was to update this topic. Abstract While cows are predominantly monovular, over the past 30 years the incidence of multiple ovulations and thus twinning has increased considerably alongside milk production. Multiple pregnancies are not desirable as they negatively affect the health of cows and the herd economy. Although causal mechanisms associated with multiple ovulations have been extensively revised, the process of multiple ovulations is not well understood. Recent studies on the thermal biology of the reproductive system have shown how thermal mechanisms may prevent or favor multiple ovulations. This review focuses on this relationship between thermal dynamics and multiple pregnancies. Cooling of the pre-ovulatory follicle is able to regulate ovulation. In effect, pre-ovulatory local cooling of the female reproductive system favors male and female gamete maturation and promotes fertilization. Thermal stress is proposed here as a model of stress. Periods of high ambient temperature affect the processes of pre-ovulatory follicular cooling and multiple ovulations. While the ratio between unilateral and bilateral multiple pregnancies is normally close to one, under heat stress conditions, this ratio may be 1.4 favoring unilateral multiple pregnancies. A ratio approaching unity is here proposed as an indicator of cow wellbeing.
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Tatebayashi R, Nakamura S, Minabe S, Furusawa T, Abe R, Kajisa M, Morita Y, Ohkura S, Kimura K, Matsuyama S. Gene-expression profile and postpartum transition of bovine endometrial side population cells†. Biol Reprod 2021; 104:850-860. [PMID: 33438005 DOI: 10.1093/biolre/ioab004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 12/11/2020] [Accepted: 01/07/2021] [Indexed: 11/12/2022] Open
Abstract
The mechanism of bovine endometrial regeneration after parturition remains unclear. Here, we hypothesized that bovine endometrial stem/progenitor cells participate in the postpartum regeneration of the endometrium. Flow cytometry analysis identified the presence of side population (SP) cells among endometrial stromal cells. Endometrial SP cells were shown to differentiate into osteoblasts and adipocytes. RNA-seq data showed that the gene expression pattern was different between bovine endometrial SP cells and main population cells. Gene Set Enrichment Analysis identified the enrichment of stemness genes in SP cells. Significantly (false discovery rate < 0.01) upregulated genes in SP cells contained several stem cell marker genes. Gene ontology (GO) analysis of the upregulated genes in SP cells showed enrichment of terms related to RNA metabolic process and transcription. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis of upregulated genes in SP cells revealed enrichment of signaling pathways associated with maintenance and differentiation of stem/progenitor cells. The terms involved in TCA cycles were enriched in GO and KEGG pathway analysis of downregulated genes in SP cells. These results support the assumption that bovine endometrial SP cells exhibit characteristics of somatic stem/progenitor cells. The ratio of SP cells to endometrial cells was lowest on days 9-11 after parturition, which gradually increased thereafter. SP cells were shown to differentiate into epithelial cells. Collectively, these results suggest that bovine endometrial SP cells were temporarily reduced immediately after calving possibly due to their differentiation to provide new endometrial cells.
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Affiliation(s)
- Ryoki Tatebayashi
- Laboratory of Animal Production Science, Graduate School of Bioagricultural Sciences, Nagoya University, Aichi, Japan
| | - Sho Nakamura
- Faculty of Veterinary Medicine, Okayama University of Science, Ehime, Japan
| | - Shiori Minabe
- Department of Anatomy and Neurobiology, Graduate School of Medicine, Nippon Medical School, Tokyo, Japan
| | - Tadashi Furusawa
- Division of Animal Sciences, Institute of Agrobiological Sciences, National Agriculture and Food Research Organization (NARO), Ibaraki, Japan
| | - Ryoya Abe
- Laboratory of Animal Production Science, Graduate School of Bioagricultural Sciences, Nagoya University, Aichi, Japan
| | - Miki Kajisa
- Laboratory of Animal Production Science, Graduate School of Bioagricultural Sciences, Nagoya University, Aichi, Japan
| | - Yasuhiro Morita
- Laboratory of Animal Production Science, Graduate School of Bioagricultural Sciences, Nagoya University, Aichi, Japan.,Asian Satellite Campuses Institute, Nagoya University, Nagoya, Japan
| | - Satoshi Ohkura
- Laboratory of Animal Production Science, Graduate School of Bioagricultural Sciences, Nagoya University, Aichi, Japan
| | - Koji Kimura
- Laboratory of Reproductive Physiology, Graduate School of Environmental and Life Science, Okayama University, Okayama, Japan
| | - Shuichi Matsuyama
- Laboratory of Animal Production Science, Graduate School of Bioagricultural Sciences, Nagoya University, Aichi, Japan
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Nakamura S, Miwa M, Morita Y, Ohkura S, Yamamura T, Wakabayashi Y, Matsuyama S. Neurokinin 3 receptor-selective agonist, senktide, decreases core temperature in Japanese Black cattle. Domest Anim Endocrinol 2021; 74:106522. [PMID: 32841888 DOI: 10.1016/j.domaniend.2020.106522] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 06/25/2020] [Accepted: 07/08/2020] [Indexed: 11/27/2022]
Abstract
Heat stress disrupts reproductive function in cattle. In summer, high ambient temperature and humidity elevate core body temperature, which is considered to be detrimental to reproductive abilities in cattle. Neurokinin B (NKB) is a factor that generates pulsatile GnRH and subsequent LH secretion in mammals. Recent studies have reported that NKB-neurokinin 3 receptor (NK3R) signaling is associated with heat-defense responses in rodents. The present study aimed to clarify the role of NKB-NK3R signaling in thermoregulation in cattle. We examined the effects of an NK3R-selective agonist, senktide, on vaginal temperature as an indicator of core body temperature in winter and summer. In both seasons, continuous infusion of senktide for 4 h immediately decreased vaginal temperature, and the mean temperature change in the senktide-treated group was significantly lower than that of both vehicle- and GnRH-treated groups. Administration of GnRH induced LH elevation, but there was no significant difference in vaginal temperature change between GnRH- and vehicle-treated groups. Moreover, we investigated the effects of senktide on ovarian temperature. Senktide treatment seemed to suppress the increase in ovarian temperature from 2 h after the beginning of administration, although the difference between groups was not statistically significant. Taken together, these results suggest that senktide infusion caused a decline in the vaginal temperature of cattle, in both winter and summer seasons, and this effect was not due to the gonadotropin-releasing action of senktide. These findings provide new therapeutic options for senktide to support both heat-defense responses and GnRH/LH pulse generation.
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Affiliation(s)
- S Nakamura
- Division of Animal Feeding and Management Research, Institute of Livestock and Grassland Science, NARO, Nasushiobara, Japan; Faculty of Veterinary Medicine, Okayama University of Science, Imabari, Japan
| | - M Miwa
- Division of Animal Feeding and Management Research, Institute of Livestock and Grassland Science, NARO, Nasushiobara, Japan; Division of Grassland Farming, Institute of Livestock and Grassland Science, NARO, Nasushiobara, Japan; Agricultural AI Research Office, Research Center for Agricultural Information Technology, NARO, Tsukuba, Japan
| | - Y Morita
- Laboratory of Animal Production Science, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - S Ohkura
- Laboratory of Animal Production Science, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - T Yamamura
- Agricultural AI Research Office, Research Center for Agricultural Information Technology, NARO, Tsukuba, Japan; Division of Animal Breeding and Reproduction Research, Institute of Livestock and Grassland Science, NARO, Tsukuba, Japan
| | - Y Wakabayashi
- Division of Animal Breeding and Reproduction Research, Institute of Livestock and Grassland Science, NARO, Tsukuba, Japan
| | - S Matsuyama
- Division of Animal Feeding and Management Research, Institute of Livestock and Grassland Science, NARO, Nasushiobara, Japan; Laboratory of Animal Production Science, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan.
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Twin Pregnancies in Dairy Cattle: Observations in a Large Herd of Holstein-Friesian Dairy Cows. Animals (Basel) 2020; 10:ani10112165. [PMID: 33233629 PMCID: PMC7699672 DOI: 10.3390/ani10112165] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Revised: 11/01/2020] [Accepted: 11/18/2020] [Indexed: 12/18/2022] Open
Abstract
Simple Summary Cows have two ovaries, two uterine horns, two oviducts, and a uterine body. Although they are commonly monovular, they can sustain twin or other multiple pregnancies to term. In cows with a single pregnancy, the embryo implants in the uterine horn that is on the side of ovulation where a corpus luteum develops. Multiple pregnancies are classified into bilateral (one or more embryos in each uterine horn) and unilateral (all embryos in the same uterine horn, right or left) and, in both cases, embryos occur on the side of their corresponding corpus luteum or corpora lutea. Multiple pregnancies are undesirable in dairy herds as they compromise the reproductive performance and productive lifespan of cows. The present study sought to: (a) gain information on the incidence of twin pregnancies, (b) assess and expand information on the relative incidence of bilateral twins compared to unilateral twins, (c) confirm corresponding laterality between embryos and corpora lutea, (d) tabulate the frequency of triplets or quadruplets, and (e) evaluate possible effects of environmental heat stress conditions on the incidence of multiple pregnancies. The data for this study were derived from the ultrasonographic examination of 1130 cows carrying twins, triplets, or quadruplets, and 3160 cows carrying singletons. Abstract Multiple pregnancies have devastating consequences on the herd economy of dairy cattle. This observational study examines incidence patterns based on data from the ultrasonographic examination of 1130 multiple pregnancies in cows in their third lactation or more carrying twins (98.8%), triplets (1.1%), or quadruplets (0.08%), and 3160 of their peers carrying singletons. Cows became pregnant following a spontaneous estrus with no previous hormone treatments. Irrespective of a significant decrease (p < 0.0001) in the conception rate (28–34 days post-insemination) during the warm period of the year, the multiple pregnancy rate was similar for both warm (26.5%) and cool (26.3%) periods. The incidence of unilateral multiple pregnancies (all embryos in the same uterine horn) was higher than that of bilateral pregnancies (at least one embryo in each uterine horn): 54.4% versus 45.6% (p < 0.0001). This difference rose to 17% during the warm season (p = 0.03). Pregnancy was monitored in unilateral multiple pregnancies until abortion or parturition (n = 615). In the warm period, the parturition rate was 43% compared to 61% recorded in the cool period (p < 0.0001). Thus, a warm climate is the main factor compromising the fate of multiple pregnancies. Some clinical suggestions are provided.
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Hunter RHF, López-Gatius F. Temperature gradients in the mammalian ovary and genital tract: A clinical perspective. Eur J Obstet Gynecol Reprod Biol 2020; 252:382-386. [PMID: 32682213 DOI: 10.1016/j.ejogrb.2020.07.022] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 06/30/2020] [Accepted: 07/10/2020] [Indexed: 12/11/2022]
Abstract
Temperature within mammalian reproductive tissues is noted to be a key component of fertility, and significant gradients in temperature can be demonstrated deep within the abdomen shortly before ovulation. Indeed, in the absence of such gradients in the ovary and genital tract, the processes of ovulation and fertilisation are severely compromised. This review aims to assess literature produced during the last five decades regarding temperature gradients in the mammalian ovary and genital tract. A large body of observations derived from rabbits, women, pigs and cattle is summarised in tabular form, ovarian follicular values being as much as 2.5 °C or more cooler than neighbouring ovarian tissues or deep rectal temperature. We highlight recent works demonstrating a positive correlation between pre-ovulatory follicular cooling and pregnancy. Understanding the significance of follicular cooling should help us (a) explain why so many potential pregnancies fail in vivo as in vitro and (b) inspire ways for improving the processes of fertilisation and establishment of a full-term pregnancy. Based on our findings in domestic animals, and most recently in cows whose Graafian follicles are comparable in size and timing of response to the LH peak with human follicles, we wish to encourage IVF and fertility preservation clinics to take advantage of this work. By so doing, the incidence of full-term pregnancies in women should be improved.
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Affiliation(s)
- Ronald H F Hunter
- Sidney Sussex College, University of Cambridge, UK; Ladfield, Oxnam, Jedburgh, UK
| | - Fernando López-Gatius
- Agrotecnio Center Lleida, Spain; Transfer in Bovine Reproduction SLu, Barbastro, Spain.
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