Supplementation of Slow‐Release Melatonin Improves Recovery of Ovarian Cyclicity and Conception in Summer Anoestrous Buffaloes (Bubalus bubalis)

Abstract

The role of melatonin as a protective neurohormone against restoring cyclicity in summer anoestrous animals in photoperiod species has gained wider acceptance. This study was designed to uncover the evidence the slow-release melatonin (MLT) has on initiation of ovarian cyclicity and conception rate (CR) in summer anoestrous buffaloes. Thus, buffaloes diagnosed as summer anoestrous (absence of overt signs of oestrus, concurrent rectal examination and radioimmunoassay for serum progesterone at 10 days interval) were grouped as untreated (Group I, sterilized corn oil, n = 8) and treated (Group II, single subcutaneous injection of MLT @18 mg/50 kg bwt in sterilized corn oil, n = 20). Animals treated and detected in oestrus were artificially inseminated (AI) followed by division into Group III (second dose of MLT on 5th day post-AI, n = 8) and Group IV (no melatonin administration, n = 10). Blood samples were collected at 4 days interval for estimation of serum MLT, progesterone and oestrogen using radioimmunoassay kit. Mean oestrous induction rate (OIR), oestrous induction interval (OII), interoestrous interval (IOI) and CR were estimated. Compared to control, concentration of melatonin was significantly (p < 0.05) higher in treated group ranging from 14.34 ± 1.72 to 412.31 ± 14.47 pg/ml whereas other two hormones did not show any concentration difference. Melatonin-administered buffaloes showed significantly (p < 0.05) higher (90%) OIR with OII of 18.06 ± 1.57 days. Results showed improvement in conception rate in buffaloes administered with post-insemination melatonin. It can be concluded from the study that slow-release melatonin supplementation restored cyclicity in summer anoestrous animals resulting in improvement in conception rate in buffaloes.

Role of Melatonin in Reproductive Seasonality in Buffaloes

“…It has been reported that melatonin implants in buffaloes can improve conception rate [12,15]. Melatonin treatment in buffalo is necessary to induce cyclicity during anestrus in out-of-breeding season in which evidenced an improvement in conception rate [42,43]. Ramadan et al [12,15] found that melatonin implantation alone did not affect the post-treatment reproductive performance in either anestrus buffalo or lactating buffaloes during out-of-breeding season.…”

“…In anestrus lactating buffaloes injected with melatonin, the serum P4 concentrations increased (0.71 ng/ml) after melatonin injection compared with control group (0.28 ng/ml) at days 12 and 16 post-treatment (post-AI), during the summer season, suggesting a luteotrophic effect of melatonin [42]. Also, exogenous melatonin might improve uterine expression of P4 receptors or their binding capacity, which would result in higher reproductive efficiency [42].…”

“…Lactating buffaloes treated with melatonin alone present higher E 2 concentrations recorded (16 pg/ml) after melatonin treatment in comparison to the control group (9.02 pg/ml) [42]. The pattern of serum E 2 profile in the induced estrous cycle was highest on the day of estrus and decreased in the second week of the cycle [46].…”

“…The administration of slow-release melatonin (implants) was responsible for an increase in serum melatonin concentration, ranging from 14.34 to 412.31 pg/ml in treated lactating buffaloes [42]. Administration of exogenous slow-release melatonin induced the restoration of the ovarian activity in summer anestrus buffaloes, which can be explained by a 'cascading effect' of at least a 10-fold increase on the plasma concentrations of GnRH and gonadotrophins, which provides the necessary boost for follicular growth and ovulation [50].…”

>b<Melatonina para o tratamento da degeneração testicular em touros e seus efeitos sobre a bioquímica sérica e do plasma seminal, termodinâmica e hemodinâmica testicular e características espermáticas>/b<

“…Esses genes participam ativamente na formação da barreira hemato-testicular, regulação das células de Leydig, na espermatogênese e no mecanismo de apoptose(YANG et al, 2014). A administração exógena de melatonina diluída em veículo oleoso por via intramuscular é eficiente em aumentar a concentração sérica de melatonina por tempo prolongado em touros bovinos da raça Nelore.Para a escolha da concentração de melatonina a ser testada foi tomado por base a concentração descrita porKumar et al (2016) para bubalinos, os quais utilizaram a concentração de 18 mg/50 kg de peso vivo com resultados satisfatórios, conseguindo manter a concentração de melatonina elevada durante aproximadamente 20 dias, conforme ilustrado na figura 1. Porém, também foi testada uma concentração 50% maior, a fim de verificar se uma concentração maior seria mais efetiva.Figura 1: Concentração de melatonina sérica obtida por Kumar et al (2016) em animais tratados com 18 mg de melatonina para cada 50 kg de peso vivo em comparação com animais controle por 36 dias.…”