Comparing early embryo mortality in dairy cows during hot and cool seasons of the year

Ryan, David P.; Prichard, J.F.; Kopel, E.; Godke, R.A.

doi:10.1016/0093-691x(93)90257-6

Cited by 78 publications

(17 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…For example, heat stress compromised embryonic development when applied from d 8 to 16 of pregnancy (Biggers et al, 1987). In addition, Ryan et al (1993) observed differences in embryonic loss of superovulated cows between cool and hot periods of year at d 13 or 14 of pregnancy but not at d 6 or 7. Furthermore, exposure of bovine embryos flushed from superovulated heifers at d 6 or 7 of pregnancy to heat shock in culture reduced cell number (Sugiyama, 1999).…”

Section: Later Embryonic Developmentmentioning

confidence: 94%

“…The mechanism by which heat stress causes decreased fertility is probably multifactorial and may vary depending on the magnitude of heat stress. When rectal temperatures in the hot season were low (39.0°C ) because of environmental cooling, most early embryonic mortality associated with the hot season occurred between d 6 and 14 of pregnancy (Ryan et al, 1993). In contrast, Putney et al (1988a) observed that experimental application of a heat stress that caused rectal temperatures to rise to 41.1°C caused a large reduction in embryonic development at an earlier time ( d 7 after estrus).…”

Section: Heat Stress-induced Embryonic Mortality: Characteristics Andmentioning

confidence: 99%

“…2/1999 seen in cool weather because of the severe consequences of heat stress for embryogenesis. Depression in pregnancy rate per insemination in warm or hot periods of the year has been well documented in many regions (Stott et al, 1962;Monty and Wolff, 1974;Rosenberg et al, 1977;Badinga et al, 1985;Cavestany et al, 1985;King et al, 1988;Du Preez et al, 1991;Ryan et al, 1993). There are two types of evidence that this depression is caused primarily by heat stress and not other environmental variables.…”

Section: Heat Stress-induced Embryonic Mortality: Characteristics Andmentioning

confidence: 99%

See 2 more Smart Citations

Strategies for managing reproduction in the heat-stressed dairy cow

Hansen

Aréchiga

1997

Journal of Animal Science

168

136

View full text Add to dashboard Cite

Establishment and maintenance of pregnancy is difficult in lactating dairy cows exposed to heat stress because of reductions in estrous detection rate and the proportion of inseminated cows that maintain pregnancy. The most common approach to ameliorate heat stress in developed countries has been to alter the cow's environment through provision of shade, fans, sprinklers, and so on. Nonetheless, seasonal variation in reproductive function persists. Increased understanding of bovine reproductive function and its alteration by heat stress has led to additional strategies for reducing deleterious consequences of heat stress on reproduction. These include hormonally induced timed artificial insemination, which can reduce losses in reproductive efficiency caused by poor detection of estrus, and embryo transfer, which can increase pregnancy rate by allowing embryos to bypass the period when they are most sensitive to elevated temperature (i.e., in the first 1 to 2 d after breeding). Other efforts are directed toward developing methods to protect the embryo from harmful actions of elevated temperature. Approaches being studied include manipulation of embryonic synthesis of heat shock proteins and use of antioxidants to reduce free radical damage associated with heat stress. It may also be possible to reduce the magnitude of hyperthermia caused by heat stress. This might be possible physiologically, for example by feeding of agents that affect thermoregulatory systems, or genetically by selecting for specific traits conferring thermal resistance. Finally, the development of bovine somatotropin as a lactational promotant means that it may be possible to extend lactations beyond 305 d and voluntarily discontinue inseminations during periods of heat stress.

show abstract

Section: Later Embryonic Developmentmentioning

confidence: 94%

Section: Heat Stress-induced Embryonic Mortality: Characteristics Andmentioning

confidence: 99%

Section: Heat Stress-induced Embryonic Mortality: Characteristics Andmentioning

confidence: 99%

See 1 more Smart Citation

Strategies for managing reproduction in the heat-stressed dairy cow

Hansen

Aréchiga

1997

Journal of Animal Science

168

136

View full text Add to dashboard Cite

show abstract

“…Hypersensitivity of the preimplantation embryo to elevated temperatures is a transient phenomenon; effects of heat shock on development of cultured bovine embryos are reduced as embryos advance in development past the two-to four-cell stage [4,7]. The susceptibility of the embryo to elevated temperature is likely one of the major causes for the decrease in fertility and increase in embryonic mortality caused by heat stress in cattle [9][10][11], sheep [12], rabbits [13], and mice [14].…”

Section: Introductionmentioning

confidence: 99%

Alterations in Ultrastructural Morphology of Two-Cell Bovine Embryos Produced In Vitro and In Vivo Following a Physiologically Relevant Heat Shock1

Rivera

Kelley

Erdos

et al. 2003

Biology of Reproduction

View full text Add to dashboard Cite

Exposure of cultured preimplantation embryos to temperatures similar to those experienced by heat-stressed cows inhibits subsequent development. In this study, the effects of heat shock on the ultrastructure of two-cell bovine embryos were examined to determine mechanisms for inhibition of development. Two-cell embryos produced in vitro were harvested at approximately 28 h postinsemination and cultured for 6 h at one of three temperatures: 38.5 degrees C (cow body temperature), 41.0 degrees C (characteristic temperature for heat-stressed cows), or 43.0 degrees C (severe heat shock). Ultrastructural examinations revealed that both heat shocks resulted in the movement of organelles towards the center of the blastomere. In addition, heat shock increased the percentage of mitochondria exhibiting a swollen morphology. Distance between the membranes comprising the nuclear envelope was increased but only when embryos were treated at 43.0 degrees C. To determine whether ultrastructural responses to heat shock in culture were similar for embryos produced in vitro and in vivo, two-cell embryos were collected from superovulated Angus cows 48 h postinsemination and treated ex vivo for 6 h at 38.5 degrees C or 41.0 degrees C. Again, heat shock caused an increase in number of swollen mitochondria and movement of organelles away from the periphery of the blastomere. Exposure of two-cell bovine embryos to physiologically relevant elevated temperatures causes disruption in ultrastructural morphology that is inimical to development. The observation that overall morphology and response to heat was similar for embryos produced in vitro and in vivo implies that the former can be a good model for understanding embryonic responses to heat shock.

show abstract

“…Embryo loss is another important factor that effects fertility and is increased during heat stress. There are several evidences available to show that the bovine embryo is sensitive to maternal heat stress, particularly during the first 2 weeks after breeding (Ryan et al, 1993). A major source for reduction in embryonic survival induced by heat stress may be adverse effects of elevated body temperatures on developing zygotes and embryos.…”

Section: Effect On Embryonic Developmentmentioning

confidence: 99%

Effect of Environmental Heat Stress on Reproduction Performance of Dairy Cows- A Review

Ahmed¹,

Tiwari²,

Mishra³

et al. 2015

Int. J. Livest. Res.

View full text Add to dashboard Cite

Stress is the condition where there is undue demand for physical and mental energy due to excessive and aversive environmental factors (stressors) and cause deformations those are identifiable through physiological disequilibrium. Temperature stress imparts physical and economical losses to livestock production in temperate, subtropical and tropical regions of the world. Each species, breed or animal with its physiological state, has a comfort zone, in which the energy expenditure of the animal is minimal, constant and independent of environmental temperature. When environmental temperatures move out of the thermo-neutral zone (or comfort zone) dairy cattle begin to experience heat stress. Thermo-neutral zone depends on the age, breed, feed intake, diet composition, previous state of temperature acclimatization, production, housing and stall conditions, tissue (fat, skin) insulation and external (coat) insulation, and the behaviour of the animal. The ranges of thermo-neutral zone are from lower critical temperature (LCT) to upper critical temperature (UCT). LCT is the environmental temperature at which an animal needs to increase metabolic heat production to maintain body temperature. UCT is the environmental temperature at which the animal increases heat production as a consequence of a rise in body temperature resulting for inadequate evaporative heat loss. Heat stress negatively impacts a variety of dairy parameters including milk yield and reproduction and therefore is a significant financial burden in many dairy-producing areas of the world. Advances in management (i.e. cooling systems) and nutritional strategies have alleviated some of the negative impact of thermal stress on dairy cattle, but production continues to decrease during the summer. In this review an attempt has been made to bring forth the effect of heat stress and to discuss their impact on dairy cows.

show abstract

Comparing early embryo mortality in dairy cows during hot and cool seasons of the year

Cited by 78 publications

References 33 publications

Strategies for managing reproduction in the heat-stressed dairy cow

Strategies for managing reproduction in the heat-stressed dairy cow

Alterations in Ultrastructural Morphology of Two-Cell Bovine Embryos Produced In Vitro and In Vivo Following a Physiologically Relevant Heat Shock1

Effect of Environmental Heat Stress on Reproduction Performance of Dairy Cows- A Review

Contact Info

Product

Resources

About