Effect of Melatonin Implants during the Non-Breeding Season on the Onset of Ovarian Activity and the Plasma Prolactin in Dromedary Camel

Administration of melatonin prior to modified synchronization protocol improves the productive and reproductive efficiency of Chinese crossbred buffaloes in low breeding season

Introduction

Melatonin is a neurohormone involving various biological processes, including restoration of cyclicity in animals with seasonal breeding patterns. The use of melatonin in different forms has gained broader acceptance in different species, particularly in summer anestrous buffaloes.

Objectives

The objective of the current study was to evaluate the melatonin effect on the reproductive and productive performance of crossbred buffaloes during the low breeding season.

Methods

Sixty-five cyclic and reproductively sound crossbred buffaloes were randomly allocated to three groups: the G1 (n = 20) served as the control group and received no single melatonin, G2 received melatonin (n = 22; 18 mg/50 kg, body weight) once prior to synchronization and G3 group was administered multiple melatonin injections (n = 23; 6 mg/50 kg body weight) for three consecutive days before the start of the synchronization protocol. The reproductive performance, milk yield traits, and serum immunoglobulin M (IgM) and melatonin levels were evaluated in treated and untreated crossbred buffaloes.

Results

The results revealed that a single dose of melatonin administration has (p < 0.05) improved estrus response, ovulation occurrence and follicular growth in crossbred buffaloes compared to control groups. Higher pregnancy rates were observed in both melatonin-treated buffalo groups compared to the control. Following the administration of melatonin, serum IgM level increased in G2 and G3; however, an increment in melatonin level (p < 0.05) was detected in the G2 group only as compared to the control group subsequent day of melatonin administration. The milk compositions were not affected by melatonin administration except for milk urea nitrogen and somatic cell count (SCC). The melatonin administration (p < 0.05) decreased the somatic cell count in buffalo milk compared to untreated.

Conclusion

In conclusion, single or multiple doses of melatonin before initiating the synchronization protocol improved the ovulation, ovulatory follicle diameter and pregnancy rates in crossbred buffaloes during the low breeding season. Moreover, the administration of melatonin enhanced the IgM values along milk traits in terms of milk protein, MUN and somatic cell count in treated buffaloes.

Seasonal variations in locomotor activity rhythm and diurnal activity in the dromedary camel (Camelus dromedarius) under mesic semi-natural conditions

The dromedary camel (Camelus dromedarius) is a large ungulate that copes well with the xeric environment of the desert. Its peculiar adaptation to heat and dehydration is well-known. However, its behavior and general activity is far from being completely understood. The present study was carried out to investigate the ecological effect of the various seasons on the locomotor activity (LA) rhythm and diurnal activity of this species. Six adult female camels were maintained under mesic semi-natural conditions of the environment during four periods of 10 days in each season: autumn, winter, spring and summer. In addition, three female camels were used to test the effect of rain on the LA rhythm during a period of 18 days during the winter. The animal's LA was recorded using the locomotion scoring method. Camels displayed a clear 24.0h LA rhythm throughout the four seasons. Activity was intense during Day-time (6-22 fold higher in comparison to night) and dropped or completely disappeared during nighttime. Mean daytime total activity was significantly higher in the summer as compared to winter. Regardless of the season, the active phase in camels coincided with the time of the photophase and thermophase. Furthermore, the daily duration of the time spent active was directly correlated to the seasonal changes of photoperiod. The diurnal activity remained unchanged over the four seasons. For each season, the start and the end of the active phase were synchronized with the onset of sunrise and sunset. At these time periods, temperature remained incredibly stable with a change ranging from 0.002 to 0.210°C; whereas, changes of light intensity were greater and faster with a change from 0.1 to 600 lux representing a variation of 3215-7192 fold in just 25-29 min. Rainfall affected the pattern of the LA rhythm with occurrence of abnormal nocturnal activity during nighttime disturbing nocturnal rest and sleep. Here we show that the dromedary camel exhibits significant seasonal changes of its activity within daylight hours. However, the diurnal pattern remains unchanged regardless of the season; whereas, abnormal nocturnal activity is observed during periods of rain. The activity onset and offset in this species seems to be primarily driven by the changes in light intensity at dusk and dawn.

Effect of advancing the breeding season on reproductive performance of dromedary camels

This study examines the effect of advancing the breeding season on the reproductive performance of dromedary camels under an intensive management system. Using a synchronization protocol, timed natural mating in female camels was carried out either in September (2 months ahead of the natural breeding season, n = 182) or December (peak breeding season, n = 115). The ovarian responses (size of the dominant follicle at the time of mating and ovulation), pregnancy rate, and pregnancy losses were evaluated using ultrasonography. Blood samples were collected after mating to assess progesterone concentrations by RIA. The libido of male camels (n = 13) was evaluated objectively. Results showed that the percentage of female camels with an optimal sized follicle (11-17 mm) for breeding at the time of mating was lower in September compared to December (81.9 vs 91.3%, P = 0.03). The libido of male camels was lower in September than in December (P <0.001). The ovulation rate (86.3 vs 93.9%, P = 0.04), size of the ovulated follicle (12.7 ± 0.1 vs 13.7 ± 0.2 mm, P <0.001), pregnancy rates on Day 14 (47.8 vs 72.2%, P <0.001) and Day 90 (38.5 vs 60.9%, P <0.001) after mating was lower in September compared to December. However, pregnancy loss was not affected between months (15.7 vs 19.5%, P = 0.3). Among pregnant camels, the progesterone concentrations on Days 6, 8, 10, 12 and 14 after mating were lower in September as compared to December (P <0.001). In non-pregnant camels, the progesterone concentrations on Days 6, 8 and 10 after mating were also lower in September as compared to December (P <0.001). In conclusion, advancing the breeding season by two months, significantly affects the reproductive performance of dromedary camels, yet, acceptable pregnancy rates can be achieved.

The in vitro effects of melatonin and Cry gene on the secretion of estradiol from camel ovarian granulosa cells

Bactrian camel as endemic economic species to the Northwest of China, its seasonal reproduction severely limits litter rates. In addition to melatonin, seasonal reproduction of animals is also regulated by the biological clock, but the specific molecular mechanism is not clear. To investigate the effects of melatonin and Cryptochrome (Cry) genes on seasonal reproduction, they were placed in ovarian granulosa cells, and their effects on reproduction were determined by measuring the concentrations of estradiol. Immunohistochemistry revealed that melatonin receptor protein (MT) was expressed in the cytosol and membrane of the ovarian granulosa cells, and the highest levels of CRY were expressed in the nuclei. The concentrations of estradiol in the cell culture supernatant were increased after the addition of exogenous melatonin or overexpression of MT, but these were decreased after MT was over expressed, and exogenous melatonin was added to the cells. In addition, there was a significant increase in the concentrations of estradiol after the Cry genes were overexpressed; however, the estradiol concentrations were decreased after the Cry genes were silenced. Our findings demonstrate that the MT and Cry genes play important roles in ovarian granulosa cell production of estradiol in a seasonally breeding species.

The effect of photoperiod and melatonin on plasma prolactin concentrations in female guanaco (Lama guanicoe) in captivity

The present study examined the effects of different photoperiods and melatonin treatment on plasma prolactin concentrations in guanacos, a South American camelid, in captivity. Fourteen adult female guanacos, not gestating or lactating and isolated from males, were studied. The control group was exposed to natural daylight, during short days (N = 7, 10L:14D) and long days (N = 7, 16L:8D). The treatment group (N = 7, 10L:14D) received melatonin implants every 23 days for 6 weeks during long days. Blood samples were taken at intervals of 1 week for 3 weeks, starting the third week of treatment. Prolactin concentrations were measured using competitive ELISA. Plasma concentrations of prolactin in non-lactating female guanacos have seasonal changes, with a higher concentration (p < .001) in short days (3.50 ± 2.24 ng/ml) than long days (1.10 ± 0.91 ng/ml). Melatonin treatment significantly decreases (p < .05) plasma concentrations of prolactin on the 21st day after the treatment. These findings are the first report of an endogenous circannual rhythm of plasma prolactin concentration and the action of melatonin treatment on prolactin secretion in this wild camelid.

Dromedary camel: A model of heat resistant livestock animal

Camels are highly adapted to harsh environments. The dromedary camel is adapted to a wide range of arid and semi-arid conditions. The aim of the present paper is to review some of the key adaptation characteristics of the dromedary and how they affect reproductive patterns. Special attention is given to the reproductive seasonality and interaction between lactation and reproduction. Adaptive mechanisms are described including some of the recent molecular aspects with respect to heat shock protein expression in camels.

Higher doses of Melatonin affect ovarian and middle uterine arteries vascular blood flow and induce oestrus earlier in acyclic ewes

The present study aimed to evaluate the effect of a single intramuscular injection of melatonin on response of oestrus, rate of conception, ovarian and uterine blood supply during the non-breeding season. Melatonin powder was dissolved in dimethyl sulfoxide (DMSO) and olive oil and injected in two dose of 25 mg (MEL-1; n = 10) and 50 mg (MEL-2; n = 10) in May. Ten ewes were served as the control (CON). Results showed that oestrous response was higher in the MEL-2 group than in other groups (p < .01). The time to onset of oestrus in both the MEL-1 and MEL-2 groups was significantly shorter, compared with the CON group (p < .01). Pregnancy rates reached 80% and 90% at 45 days of gestation. Doppler indices of the right and left ovarian artery were lower in the melatonin groups than in normal groups (p < .01). Both Doppler indices in uterine arteries were not different among two treatment groups (p > .05), but there was a significant difference when compared with the CON group (p < .01), no difference found between two treatment group in the Doppler velocities of middle uterine arteries (p > .05). In conclusion, the definite changes in the studied parameters showed two novel findings; (a) the increase in melatonin dose results in increasing the blood flow expressed by increased Doppler velocities in fatty tailed ewes, (b) as well as, melatonin can initiate the breeding season regardless of the season earlier by 1-2 months in ewes.

Pregnancy and parturition in dromedary camels I. Factors affecting gestation length, calf birth weight and timing of delivery

In the present study, we evaluated the role of genetic, physiologic and environmental factors in affecting gestation length, calf birth weight and time of parturition in dromedary camels. Reproductive data were collected over a 10-year period at the world's first intensively managed, large-scale camel dairy farm. We hypothesized that environmental conditions (i.e. photoperiod) have a decisive effect on these reproductive parameters. The effect of various factors was tested with linear mixed models and variance component analysis. A total of 557 (13.1%) primiparous and 3691 (86.9%) multiparous parturitions were observed in 2,123 dromedaries. Parturitions had a pronounced seasonal distribution. The mean (±SE) length of gestation and mean (±SE) birth weight were 384.5 ± 0.17 days (n = 4,093, CV = 2.88%) and 34.5 ± 0.09 kg (n = 3,909, CV = 16.8%), respectively. All but one fixed factors (type of breeding) affected length of gestation and calf birth weight. Month of conception (27.1%), female camel (11.2%) and live-dead status of the calf (10.6%) were responsible for close to 50% of the variation in gestation length. At the same time, female camel (30.3%), parity (11.3%), year (6.9%) and month of parturition (6.2%) had the strongest relative influence on the variation in calf birth weight. Both reproductive traits showed a pronounced circannual variation. Mean length of gestation was longer by app. 18 days in dromedaries conceiving in November compared to those becoming pregnant in May. Average new-born weight was 4.4-4.9 kg higher in December compared to that in September and April. Dromedaries gave birth throughout the 24 h period, but most of the deliveries (n = 3,117, 74.1%) occurred from sunrise to sunset. The peak of deliveries was between 2 and 3 pm. Month of the year has a strong effect on the timing of deliveries. In contrast, the time from sunrise to parturition did not differ among the months. Peak of deliveries occurred 7-9 h after sunrise and the median of time from sunrise to parturition was 8 h and 24 min. These results give strong support to the original hypothesis. Seasonal changes were independent of nutritional factors, were associated with climatic conditions (i.e. photoperiod) and may reflect an endogenous circannual rhythm in foetal development. The dromedary camel could be a useful in vivo model to study the effect of the environment on feto-maternal communication, fetal development and timing of parturition.

Effect of short artificial lighting and low temperature in housing rooms during non-rutting season on reproductive parameters of male dromedary camels

Ten dromedary mature males were used to study the effects of short artificial lighting and low temperature on the reproductive behavior, testicular size, semen quality and hormone during the non-rutting season and subsequent rutting season. Bulls were allocated into two groups: the first group were subjected to natural daylight and temperature and used as a control. The second group was housed individually in light and temperature controlled rooms in which artificial light (300 lux) was used for 10 h/d, and the temperature was 25.28 ± 0.21 °C. The trial was initiated in mid-June and continued for 10 weeks in the non-rutting season. The reproductive parameters of all animals in the control and room groups were evaluated once every two weeks. The reproductive parameters of all animals in the control and room groups were re-evaluated during the rutting season of the same year. A significant (P < 0.05) increase in the morphometry of the testes, scrotum, libido, and reaction time score, as well as serum melatonin and testosterone levels, was observed in the treatment non-rutting season (TNRS) group compared to in the control non-rutting season (CNRS) group. The testicular volume, reaction time score, serum melatonin, and testosterone were significantly (P < 0.05) higher in the treatment rutting season (TRS) group than in the control non-rutting season (CRS) group. Improvement in the semen parameters were observed in the TNRS and TRS groups compared to in the CRS group. In conclusion, these results demonstrate that short artificial lighting and low temperature can induce rutting out of season and improve the reproductive parameters of dromedary males during the subsequent rutting season.