The use of insulin to improve fertility of timed-inseminated postpartum suckled beef cows

Abstract

-The objective of this work was to evaluate the effect of insulin alone or in association with equine chorionic gonadotropin (eCG) on the fertility of postpartum beef cows subjected to synchronization. A total of 340 cows was subjected to fixed time artificial insemination. In the trial 1, the cows were subjected to temporary weaning (TW), while in the trial 2 the same protocol was tested without TW. The addition of an insulin injection to a progesterone/eCG-based protocol without TW increased the pregnancy rate of beef cows with body condition score (BCS) equal to or lower than 2.5. Insulin had no effect on cows submitted to TW or with BCS equal to or higher than 3.0.Index terms: Bos taurus, eCG, insulin, FTAI, weaning. Uso de insulina para aumento da fertilidade de vacas de corte pós-parto lactantes inseminadasResumo -O objetivo deste trabalho foi avaliar apenas o efeito da insulina ou dela em associação com gonadotrofina coriônica equina (eCG) na fertilidade de vacas em pós-parto submetidas à sincronização. Um total de 340 vacas foi submetido à inseminação artificial em tempo fixo. No experimento 1, as vacas foram submetidas ao desmame temporário (DT), enquanto no experimento 2, o mesmo protocolo foi testado sem DT. A adição de uma injeção de insulina a um protocolo baseado em progesterona/eCG sem DT aumentou a taxa de prenhez de vacas de corte com escore de condição corporal (ECC) igual ou menor que 2,5. A insulina não teve efeito em vacas submetidas a DT ou com ECC igual ou maior que 3,0.

Insulin effect during a Heatsynch protocol in dairy cows

“…From the results of our study and other related research, the beneficial effects of using insulin exogenously can be summarized by two main points, the first relating to the increased performance of insulin when the animals are in metabolically challenging conditions. A study previously carried out by our group on beef cows (SCHNEIDER et al, 2010) supports this, as exogenous insulin administered during the TAI protocol increased conception rate only in animals with a body condition below 2.5 and without temporary weaning. Therefore, it can be postulated that insulin may be more effective in higher produce cows or in early DIM cows, once those animals face a challenge metabolic situation.…”

“…The second point is that insulin, when associated with reproductive hormones, seems to promote increased follicular growth in cattle (BHATIA & PRICE, 2001;GUPTA et al, 2010;SCHNEIDER et al, 2010;CHAVES et al, 2012). In vitro study showed that the addition of high doses of insulin (100 ng / ml) to culture media of granulosa cells is able to stimulate aromatase activity, even in the absence of FSH (BHATIA & PRICE, 2001).…”

“…Moreover, studies in vivo using insulin alongside FSH, showed that this combination promoted the growth of larger follicles and the estradiol production (SIMPSON et al, 1994). Additionally, in cows with BCS≤2.5, administering insulin together with eCG lead to an improvement in pregnancy rate when compared to animals that received only eCG (SCHNEIDER et al, 2010). In anestrus buffaloes, the use of GnRH-associated insulin had positive effects on ovarian activity, estrus presentation and ovulation rate (GUPTA et al, 2010).…”

“…SIMPSON et al (1994) observed a larger diameter of follicles in Bos indicus cattle treated with insulin during superovulation protocol. In a study conducted in Angus cattle, administering both insulin and eCG during the TAI protocol lead to an increase in pregnancy rate in cows with a body condition score (BCS) of less than 2.5 (on a scale of 1 to 5) in comparison to animals receiving only eCG (SCHNEIDER et al, 2010). In dairy cows, insulin administered alongside glucose promotes increased levels of estradiol and IGF-I (BUTLER et al 2004).…”

Evaluation of follicular growth and progesterone production in Bos taurus cows strategically treated with insulin

“…As a strategy to increase the efficiency of TAI results, in these cases of low nutritional status in cows with calves, the application of equine chorionic gonadotrophin (eCG) showed positive results according to previous studies (BARUSELLI et al, 2004;ROSTAMI et al, 2011;PESSOA et al, 2016). In addition, a study conducted by our group showed that the association of insulin with eCG during the TAI protocol in beef cattle resulted in an improvement in the pregnancy rate in animals with a body corporal score (BCS) less than 2.5 (on a scale of 1 to 5), as compared with animals that received only eCG (SCHNEIDER et al, 2010). However, there are still few studies on the isolated action of metabolic hormones, such as insulin, which is an important marker of follicular dynamics in cattle (WEBB et al, 2004;HESS et al, 2005), and has the capacity to stimulate cell proliferation and follicular steroidogenesis (WETTEMANN;BOSSIS, 2000).…”