Induction of successive follicular waves by gonadotropin-releasing hormone and prostaglandin F2α to improve fertility of high-producing cows during the summer and autumn

Abstract

Reduced conception rate during the hot summer and subsequent autumn is a well-documented phenomenon. Evaporative cooling systems greatly increase milk production but only slightly improve reproductive performance; hence, additional approaches to improving fertility during the hot season are required. The purpose of the present study was to examine whether the combination of an efficient cooling system and hormonal manipulation (GnRH+PGF(2α)) might improve fertility during the summer and autumn. The experiment was conducted from July to December in 2 commercial herds in Israel and included 382 healthy Holstein cows. Cows (50 to 60 d in milk) were hormonally treated to induce 3 consecutive 9-d follicular waves, with GnRH administration followed by PGF(2α) injection 7 d later. Both control (n=187) and treated (n=195) cows were inseminated following estrus, and pregnancy was determined by palpation 45 d post-insemination. Data revealed an interaction between treatment and primiparous cows, reflected by a 16% increase in conception rate [odds ratio (OR) 2.32, 95% confidence interval (CI): 0.96-5.61] and 14% increase in pregnancy rate at 120 d in milk (OR 3.16, 95% CI: 0.93-10.47). Interaction between treatment and high body condition score was reflected by a 14% increase in pregnancy rate at 90 d in milk (OR 3.02, 95% CI: 1.14-7.96). About 60% of the treated cows expressed estrus at the expected time (normal response within 5 d following the third PGF(2α) injection); the remaining 40% that manifested estrus later (late response) had higher milk yield and lower body condition score. Additional analyses indicated that treatment interacted with normal response to raise conception rates and pregnancy rates of primiparous cows and cows with high body condition score. On the other hand, treatment by late-response interaction lowered conception rate during the summer. Implementation of such hormonal treatment in combination with an efficient cooling system may improve reproductive performance of dairy cows during the summer and subsequent autumn.

Treatment of lactating dairy cows with gonadotropin-releasing hormone before first insemination during summer heat stress

“…Among cows with BCS >2 at 50 to 60 DIM, treatments with GnRH and PGF 2α increased P/AI compared with no treatment. Furthermore, the treatments benefited primiparous, but not multiparous cows (Friedman et al, 2011). The previous authors speculated that the lesser milk production of primiparous cows may have resulted in lower body temperature compared with multiparous cows, leading to a better response to the hormonal treatments.…”

“…Factors not assessed in this study (e.g., BCS and body core temperature) were likely associated with the observed treatment differences across herds. Friedman et al (2011) had previously reported that the benefit of treating heat-stressed cows with GnRH and PGF 2α was limited to subpopulations of cows. Among cows with BCS >2 at 50 to 60 DIM, treatments with GnRH and PGF 2α increased P/AI compared with no treatment.…”

Effects of heat stress on ovarian functions and embryonic development: mechanism and potential strategies to alleviate these effects in dairy cows

“…This transient effect is highly important because induction of frequent follicular waves during the autumn can enhance this spontaneous improvement (Roth et al 2004). Similarly, the idea that hormonal manipulation of follicle turnover will improve fertility was recently tested by Friedman et al (2011;Fig. 1): induction of three consecutive 9-day follicular waves during the summer and fall improved CR (37 vs. 53% for control and treated cows, respectively) in primiparous but not multiparous cows.…”

Overview on Adaptation, Mitigation and Amelioration Strategies to Improve Livestock Production Under the Changing Climatic Scenario

“…Administrations of hormonal preparations have found to be more benefi cial for improving reproductive effi ciency in livestock. Pregnancy rate can also be improved in the summer and autumn in primiparous cows by the use of gonadotropin-releasing hormone and prostaglandin F2α to generate three consecutive 9-day follicular waves beginning at 50-60 days in milk (Friedman et al 2011 ). The gonadotropinreleasing hormone (GnRH) administered at estrus onset is found more effective in primiparous cows and during the summer in increasing conception rate in cows with low body condition scores at AI (Kaim et al 2003 ).…”