Ovarian evaluation of Girolando (Holstein × Gir) heifers submitted to a GnRH–PGF2α–GnRH protocol in the dry or rainy seasons in the tropical savannah

Abstract

The Girolando breed is used in pasture-based dairy production systems in Brazil to associate the high production of Bos taurus to the rusticity and thermal adaptation of Bos indicus. This study was designed to evaluate the physiological response to a gonadotropin-releasing hormone (GnRH)-prostaglandin F2α (PGF2α)-GnRH protocol to synchronize the ovulation in 40 Girolando heifers of a pasture-based dairy production system and its relationships with the temperature and humidity index (THI) during the dry (DS) and rainy season (RS) in the tropical savannah-Brazil's cerrado biome. Responses were characterized by follicular and corpus luteum number and diameter, ovulation (D9), and pregnancy rates after first AI. Total follicle number (8.1 ± 0.3 × 8.8 ± 0.3), D9 ovulatory follicle diameter (11.9 ± 0.4 × 10.1 ± 0.4 mm), corpus luteum diameter (8.6 ± 1.3 × 3.9 ± 1.5 mm), corpus luteum score (3.7 ± 0.8 × 1.8 ± 1.0), corpus luteum diameter after AI (9.6 ± 1.6 × 3.9 ± 1.5 mm), and corpus luteum score after AI (3.2 ± 0.4 × 0.9 ± 0.6) in DS and RS differed (P < 0.01). D9 ovulation rate was 40 % (DS) and 20 % (RS), without differences (P > 0.05). Pregnancy rate was 45 % (DS) and 11 % (RS), with differences (P < 0.01). THI differed between DS and RS (P < 0.01). THI may interfere in the follicular and luteal dynamics and in the response of Girolando heifers to the GnRH-PGF2α protocol in the tropical savannah, thus reducing the chances of pregnancy at the first artificial insemination.

Study on reproductive performance of Holstein x Lai Sind crossbred dairy heifers and cows at smallholdings in Ho Chi Minh City, Vietnam

“…The increase in WP of cows that give birth during the RS could result from the indirect effect of a significant increase in THI (81.5 vs. 79.9, P < 0.001). A similar effect has been observed in Brazil (Bilego et al 2013). Several studies have shown the negative effects of heat stress on BCS through a reduction in intake capacity, follicular growth (Kornmatitsuk et al 2008), the resumption of PP ovarian cyclicity (Kornmatitsuk et al 2008;Rensis and Scaramuzzi 2003), and on the quality of heat detection (Fekadu et al 2011;Kornmatitsuk et al 2008).…”

“…The CRFS (58%) is lower than that of Holstein crossbred heifers in Thailand (68%) (Buaban et al 2015). These differences can be explained by the effect of nutritional (Le Cozler et al 2009) or environmental factors (heat stress) (Bilego et al 2013). Our study observed a significant decrease in AFS and AC according to year of birth.…”

“…It also leads to a decrease in oocyte quality (Ferreira et al 2011;Payton et al 2011) and in early embryo development (Gendelman et al 2010;Sakatani et al 2012). In Holstein x Gir crossbred heifers, a negative seasonal effect on the number of follicles, their diameter and the corpus luteum diameter, as well as on serum progesterone concentration was reported (Bilego et al 2013). At the same time, the favorable impact of an increase in BCSI was also demonstrated (Carvalho et al 2014).…”

“…Better fertility was observed in cows inseminated in DS than in RS (P < 0.001). Many studies reported that the season had a significant effect in some cases (Avendano-Reyes et al 2010;Bilego et al 2013;Fekadu et al 2011) and less significant in others (Ansari-Lari et al 2010;Tadesse et al 2010). This effect is more probably due to a reduction in THI than to a lack of feed in DS.…”

Effects of FSH and the weather during induced ovulation and timed artificial insemination to increase jenny conception rates

“…For example, Bilego et al . 21 found that THI interfered with follicular and luteal dynamics and the response of heifers to the GnRH-PGF 2α treatment, leading to reduced pregnancy after insemination. Ghuman et al .…”