Effect of the El Nińo phenomenon on the ovarian responsiveness and embryo production of donor cows

Abstract

The effects of different Temperature Humidity Index (THI) values in cold, hot and El Niño (EN) climates on superovulation and embryo production were analysed on Holstein Friesian donor cows. There were significant differences in the THI among the three climates. The average temperature in the EN period was 6 °C higher than in the summer period of the previous 30 years. The number of corpora lutea (CL) and embryos were log-and back-transformed, KolmogorovSmirnoff test was used for normality and Lilliefors test was applied for significance. In the cold season THI was 70.74 ± 1.35 and the average number of CL was 9.84 ± 4.37. In the hot season the THI was 73.99 ± 0.72 and the average number of CL was 9.70 ± 4.49. When the THI, in the EN period, increased up to 79.74 ± 4.01, the superovulation response was significantly (P < 0.01) reduced (average number of CL = 5.22 ± 2.53). The embryo production result showed a similar tendency. In the hot period the average number of embryos obtained was 5.87 ± 2.98. However, in the EN period it decreased to 4.21 ± 2.05. Higher temperature reduced embryo quality. The proportion of live embryos (%) was 59.2 ± 37.4 in the cold and 38.2 ± 38.5 in the EN periods of the year (P < 0.01). However, ovarian sensitiveness showed adaptation to summer environment while the heat stress, which was more severe in the EN period, negatively affected the superovulation response and embryo production.Key words: Heat stress, El Niño phenomenon, donor cows, superovulation, embryo production Cattle, like other mammalian species, are homoiothermic animals that regulate internal temperature within a narrow range (~38.0 to 39.3 °C). An animal maintains homoiothermy by matching the amount of heat produced through metabolism with the heat flow from the animal to the surrounding environment. Heat flow occurs through a process dependent on the surrounding temperature

Seasonal influences on the litter size at birth of pigs are more pronounced in the gilt than sow litters

“…7¡4 . 0) (Be´nyei et al 2003). It has also been demonstrated that this level of THI significantly reduced the number of ovulation and the oocyte quality in superovulation cows (Be´nyei et al 2003).…”

“…In beef cattle, it has been shown that increasing environmental temperature and relative humidity from 21 xC and 35 % to 33-37 xC and 27 or 38 % during days 8 to 16 of gestation reduced the size and weight of the conceptus (Biggers et al 1987). Be´nyei et al (2003) demonstrated that the average number of corpus luteum of superovulation cows decreased from 9 . 8 to 5 .…”

“…The mean relative humidity during gestation period were classified as <50·0, 50·0–59·9, 60·0–69·9, 70·0–79·9 and ⩾80·0%. The mean THIs during gestation period were classified as 71–72, 73–78, 79–80 and ⩾81, based on information from earlier studies (Bényei et al 2003) and the frequency of the THI data. The least-squares means were obtained from each class of the factors and were compared using a least-significant-difference test with the Tukey–Kramer adjustment.…”

Influence of maternal nutrition and heat stress on bovine oocyte and embryo development

“…One of these reasons is the direct effect of elevated temperature on follicular development and oocyte competence [26]. In addition, HS negatively affects the superovulation response of cows and subsequently recovered embryos number, and quality [27]. A recent study on pigs reported that gilts exposed to HS during the follicular phase showed a clear induction of ovarian autophagy, and that HS increases anti-apoptotic signaling in oocytes and early follicles [28].…”

“…However, several studies elucidated this effect from different prospective. Based on the gene expression patterns, it has been reported that HS stimulates the apoptosis signaling pathway in oocyte by upregulation of BAX and ITM2B (apoptotic genes) [27] and in early stage embryo by down-regulate genes associated with embryonic survival, such as CDX2, a transcription factor involved in the regulation of embryo implantation and placental development [41]. In another studies, expression of growth/differentiation factor-9 (GDF9) associated with oocyte maturation was downregulated when oocyte was exposed to HS both in vivo [42] and in vitro [43].…”