Reproductive physiology of the heat-stressed dairy cow: implications for fertility and assisted reproduction

Hansen, P. J.

doi:10.21451/1984-3143-ar2019-0053

Cited by 71 publications

(68 citation statements)

References 88 publications

(39 reference statements)

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“…The first is during periods of heat stress. The benefits of ET for improving fertility in heat-stress cows have been reviewed extensively ( Hansen, 2019 ; Baruselli et al, 2020 ). Most of the infertility caused by heat stress is because of damage to the oocyte and early embryo.…”

Section: Comparisons Of Pregnancy Success Following Ai and Etmentioning

confidence: 99%

“…By the time an embryo is transferred, at the blastocyst stage, the embryo has acquired resistance to maternal thermal stress. As a result, there can be a large improvement in pregnancy rate using ET in summer (see Figure 3 for an example), and there is little or no seasonal variation in P/ET even in hot climates ( Hansen, 2019 ; Baruselli et al, 2020 ).…”

Section: Comparisons Of Pregnancy Success Following Ai and Etmentioning

confidence: 99%

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The incompletely fulfilled promise of embryo transfer in cattle—why aren’t pregnancy rates greater and what can we do about it?

Hansen

2020

Journal of Animal Science

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Typically, bovine embryos are transferred into recipient females about day 7 after estrus or anticipated ovulation, when the embryo has reached the blastocyst stage of development. All the biological and technical causes for failure of a female to produce a blastocyst 7 d after natural or artificial insemination (AI) are avoided when a blastocyst-stage embryo is transferred into the female. It is reasonable to expect, therefore, that pregnancy success would be higher for embryo transfer (ET) recipients than for inseminated females. This expectation is not usually met unless the recipient is exposed to heat stress or is classified as a repeat-breeder female. Rather, pregnancy success is generally similar for ET and AI. The implication is that either one or more of the technical aspects of ET have not yet been optimized or that underlying female fertility that causes an embryo to die before day 7 also causes it to die later in pregnancy. Improvements in pregnancy success after ET will depend upon making a better embryo, improving uterine receptivity, and forging new tools for production and transfer of embryos. Key to accelerating progress in improving pregnancy rates will be the identification of phenotypes or phenomes that allow the prediction of embryo competence for survival and maternal capacity to support embryonic development.

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Section: Comparisons Of Pregnancy Success Following Ai and Etmentioning

confidence: 99%

Section: Comparisons Of Pregnancy Success Following Ai and Etmentioning

confidence: 99%

The incompletely fulfilled promise of embryo transfer in cattle—why aren’t pregnancy rates greater and what can we do about it?

Hansen

2020

Journal of Animal Science

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“…-Introducing ET into the breeding program should improve the fertility of older cows under heat stress conditions [12].…”

Section: Resultsmentioning

confidence: 99%

Transfer of a single embryo versus drainage of subordinate follicles to prevent twin pregnancies in dairy cows. Why not both?

López‐Gatius

García-Ispierto

2020

Journal of Reproduction and Development

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In this study, we present two proposed approaches to prevent twin pregnancies in dairy cattle: 1) single, in vitro-produced embryonic transfer into a recipient cow or 2) subordinate follicle drainage at the time of insemination. Both procedures lead to improved embryonic survival. As the use of sexed semen generates herd replacements and additional heifers, we propose the transfer of a single female cattle embryo into cows that are not suitable for producing replacements, and follicular drainage in lactating cows with genetic merit. This should eliminate economic losses associated with twin pregnancies and increase cattle output of the herd.

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“…Surprisingly, however, we did not find downregulation of progesterone levels caused by the dysfunction of the corpus luteum during long-term HS. Suggesting the HS cows maintained pregnancy and mild to moderate HS did not impact corpus luteum function and placental development [8, 11]. Physiological indicators proved that pregnant cows were more susceptible to thermal stress, compared to non-pregnant cows.…”

Section: Discussionmentioning

confidence: 99%

“…In Florida, pregnancy rates of lactating cows in the summer is low (13.5%) [10]. Furthermore, the number of mounts per estrus also decreased by nearly half in summer, compared to winter [11]. For lactating cows, HS conditions have been reported to reduce milk yield by about 30-40 % [12–14].…”

Section: Introductionmentioning

confidence: 99%

Analysis of circulating-microRNA expression in lactating Holstein cows under summer heat stress

Lee¹,

Lee

Son³

et al. 2020

Preprint

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Korean peninsular weather is rapidly becoming subtropical due to global warming. In summer 2018, South Korea experienced the highest temperatures since the meteorological observations recorded in 1907. Heat stress has a negative effect on Holstein cows, the most popular breed of dairy cattle in South Korea, which is susceptible to heat. To examine physiological changes in dairy cows under heat stress conditions, we analyzed the profiles circulating microRNAs isolated from whole blood samples collected under heat stress and non-heat stress conditions using small RNA sequencing. We compared the expression profiles in lactating cows under heat stress and non-heat stress conditions to understand the regulation of biological processes in heat-stressed cows. Moreover, we measured several heat stress indicators, such as rectal temperature, milk yield, average daily gain, and progesterone concentration. All these assessments showed that pregnant cows were more susceptible to heat stress than non-pregnant cows. Particularly, progesterone concentrations known to have maternal warming effects were at similar levels in non-pregnant cows but significantly increased in pregnant cows under heat stress conditions. The differentially expressed miRNAs and their putative target genes were analyzed in pregnant cows. Interestingly, we found that differentially expressed miRNAs (bta-miR-146b, bta-miR-20b, bta-miR-29d-3p, bta-miR-1246) specifically targeted progesterone biosynthesis (StAR) and the function of corpus luteum-related genes (CCL11, XCL), suggesting that pregnant cows with elevated progesterone concentrations are more susceptible to heat stress. In addition, we found the differential expression of 11 miRNAs (bta-miR-19a, bta-miR-19b, bta-miR-30a-5p, and several from the bta-miR-2284 family) in both pregnant and non-pregnant cows under heat stress conditions. In target gene prediction and gene set enrichment analysis, these miRNAs were found to be associated with the cytoskeleton, cell junction, vasculogenesis, cell proliferation, ATP synthesis, oxidative stress, and immune responses involved in heat response. These miRNAs can be used as potential biomarkers for heat stress.

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Reproductive physiology of the heat-stressed dairy cow: implications for fertility and assisted reproduction

Abstract: Heat stress causes a large decline in pregnancy success per insemination during warm times of the year.

Cited by 71 publications

References 88 publications

The incompletely fulfilled promise of embryo transfer in cattle—why aren’t pregnancy rates greater and what can we do about it?

The incompletely fulfilled promise of embryo transfer in cattle—why aren’t pregnancy rates greater and what can we do about it?

Transfer of a single embryo versus drainage of subordinate follicles to prevent twin pregnancies in dairy cows. Why not both?

Analysis of circulating-microRNA expression in lactating Holstein cows under summer heat stress

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