Blood melatonin levels relating to the reproductive activity of Sarda does

Assessing the Diversity and Population Substructure of Sarda Breed Bucks by Using Mtdna and Y-Chromosome Markers

A sample of 146 Sarda bucks from eight subregions of Sardinia, Italy (Nuorese, Barbagia, Baronia, Ogliastra, Sarrabus, Guspinese, Iglesiente, Sulcis) were characterized for Y-chromosome and mtDNA markers to assess the levels of population substructure. Five polymorphic loci (SRY, AMELY, ZFY, and DDX3Y) on the Y-chromosome were genotyped. The control region of mtDNA was sequenced as a source of complementary information. Analysis of Y-chromosome data revealed the segregation of 5 haplotypes: Y1A (66.43%), Y2 (28.57%), Y1C (3.57%), Y1B1 (0.71%), and Y1B2 (0.71%). High levels of Y-chromosome diversity were observed in populations from Southwest Sardinia. The FST values based on Y-chromosome and mtDNA data were low, although a paternal genetic differentiation was observed when comparing the Nuorese and Barbagia populations (Central Sardinia) with the Sulcis, Iglesiente, and Sarrabus populations (Southern Sardinia). AMOVA analysis supported the lack of population substructure. These results suggest the occurrence of a historical and extensive gene flow between Sarda goat populations from different locations of Sardinia, despite the fact that this island is covered by several large mountain ranges. Introgression with foreign caprine breeds in order to improve milk production might have also contributed to avoiding the genetic differentiation amongst Sarda populations.

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.

Melatonin treatment and male replacement every week on the reproductive performance in Sarda sheep breed

The aim of this study was to highlight whether the combination of melatonin treatment and weekly male replacement could influence reproductive performances in Sarda sheep breed. In a preselected farm, on 5th March 2016, 400 lactating ewes were identified, aged 3-5 years, with body condition score (BCS) 2.5-4.0, who lambed between 20th October and 1st December 2015. The 400 chosen animals were subsequently divided into 4 groups with 100 animals in each group (M, MR, C and CR). On 20th March 2016 the animals of Group M and MR (consisting of 100 ewes each) were treated with melatonin implants and on 24th April 2016 five entire rams were introduced into each group. In groups MR and CR, males were replaced each week with other males whereas in groups M and C the introduced males were not replaced. The MR group showed the highest fertility (number of lambed ewes) compared to the other three groups (P < 0.01). Both the melatonin treated groups (M and MR) exhibited an increase in fertility greater than the controls groups C and CR (P < 0.01). However, when the two groups treated with melatonin were compared, the MR group showed a higher fertility than the M group (P < 0.01). The same can be said for the two control groups, of which the CR group showed a greater increase in fertility than the C group (P < 0.01). The mean interval of days from male introduction to lambing was lower in the treated than in the control groups (P < 0.05). The MR group presented the lowest mean interval of days from male introduction to lambing amongst all of the groups (P < 0.05). A similar trend was recorded for group CR when compared to group C (P < 0.05). In the MR and M groups the lambing peak was recorded close to 170 days after the males introduction, whereas the CR group and the C group were reported to be around 180 days and 190 days, respectively. At the 170th day from the male introduction the number of ewes lambed in the MR group was greater than that of the M group (P < 0.05) (60 vs. 42), and more than double of that of the C and CR groups (P < 0.01). In conclusion, weekly male replacement improved the reproductive activity and strengthened the effect of the pineal hormone on reproductive efficiency. Therefore male replacement either in untreated animals or in association with the melatonin implants, can be straightforwardly applied to guarantee a more efficient reproduction in sheep breeding.

Melatonin treatment in spring and reproductive recovery in sheep with different body condition score and age

With the aim to evaluate the effect of melatonin treatment on the advanced reproductive recovery in sheep with different body condition score (BCS) and age, 800 ewes were selected from two farms. These ewes (3-6 years old, multiparous and with BCS 2.5-4.0) were subdivided into two Groups (200 M and 200 C), balanced on their BCS and age. On 20 March, Group M was treated with one melatonin implant (18 mg). Group C was untreated. Males were introduced to the groups 35 days after treatment. Gestation was diagnosed between day 45 and 90 after mating by transabdominal ultrasonography. From day 150 to 190 after rams introduction, lambing date and newborns' number were recorded. The average time in days between male introduction and lambing resulted shorter in treated than in control ewes (166.4 ± 0.48 vs. 172.5 ± 0.50) (P < 0.05). At day 160 and 170 from ram introduction the fertility rate was higher in Group M than in C (P < 0.05). The overall fertility at day 190 from rams introduction showed no differences between Group M and C (337 and 339, respectively). At day 170 from male introduction the number of the 5-6 years-old lambed ewes were 2-fold higher than the youngers (P < 0.05). The animals with a BCS 3.5-4.0 had a faster response to male effect, and a shorter mean distance in days from rams introduction to lambing, compared to those scored 2.5-3.0 (166.1 ± 0.48 vs. 174.8 ± 0.51) (P < 0.05). We concluded that the ewes with BCS 3.5-4.0 and aged 5-6 years showed a better response to melatonin treatment in spring.

Plasma melatonin in domestic female Mediterranean sheep (Comisana breed) and goats (Maltese and Red Syrian)

The plasma melatonin nychtemeral profiles in Mediterranean ewes and goats were evaluated six times throughout the year. Melatonin levels were high throughout the night and generally below the assay detection limit during daytime. However, during long days, 30% of the last daytime samples had high melatonin concentrations. Plasma melatonin levels were higher in Comisana sheep than in goats, and higher in Maltese than in Red Syrian goats, with highly significant effect of the individual animal and high repeatability. Plasma melatonin was higher in April than in August. When there was a large difference between the duration of day and night, the plasma melatonin pattern and the light/dark cycle did not always match exactly, suggesting some form of superimposition and/or the prevalence of an endogenous rhythm. The difference found at similar scotoperiods with increasing or decreasing day length may be involved in the perception of the photoperiodic changes.

Melatonin concentrations in the two jugular veins, and relationship with the seasonal reproductive activity in goats

The authors investigated whether melatonin concentrations vary between the two jugular veins and whether absolute (nocturnal) or relative (nocturnal/diurnal ratio) plasma melatonin concentrations are associated with seasonal reproductive activity measured by oestrus or ovulatory activity in Payoya goats. Thirty-two adult Payoya goats were penned under natural photoperiod. Oestrus activity was tested daily using aproned males-twice a week plasma was sampled for progesterone. Melatonin plasma concentrations were studied at each equinox and solstice of the year in jugular samples taken simultaneously by venipuncture. Nocturnal and diurnal plasma melatonin concentrations from each jugular vein were assessed in 3 and 2 plasma samples per goat, respectively, taken at hourly intervals in each period. No differences in melatonin concentrations between the two veins were observed, but there was a significant interaction (P < 0.001) between jugular vein and animal in nocturnal melatonin concentrations. There was no effect of sampling period on melatonin concentrations and the coefficient of correlation between sampling periods was very high. The analyses performed indicated that neither absolute nor relative melatonin concentrations were related with the dates of onset or end of ovulatory/oestrus activity. Therefore, we concluded that in goats (1) melatonin concentrations are highly variable between jugular veins in the same individual but not in the general population, (2) melatonin concentrations are highly repeatable for each individual, and (3) absolute and relative amplitudes of melatonin concentrations are not linked to the seasonal breeding activity in Mediterranean goats.

Relationship between MTNR1A melatonin receptor gene polymorphism and seasonal reproduction in different goat breeds

The reproductive activity of goats bred in temperate latitude follows a seasonal pattern, influenced by annual variation in day length. Daily variation in pineal melatonin secretion is the neuroendocrine signal recognized by animals through the link between this hormone and melatonin receptor 1a (MTNR1A). A total of 345 goats of different breeds (225 Sarda, 30 Saanen, 30 Chamois Coloured, 30 Maltese and 30 Nubian) with a kidding period in October-December or January-March were analysed to verify if a link exists between the structure of the receptor gene and reproductive activity. The main part of exon II of MTNR1A gene was amplified by PCR and then digested with MnlI and RsaI to prove the presence of restriction sites. Sequencing of 20 cloned samples and 20 purified samples permitted comparison with previously published sequences. No polymorphism was found using MnlI enzyme, as all 345 samples showed the cleavage site in position 605 and all the goats were MM genotype. However, using RsaI enzyme, some Sarda goats, showed a polymorphic site in position 53. Nine Sarda goats were R/r genotype, lacking this cleavage site only in one allele, while the other animals, both Sarda and the other breeds, presented the cleavage site in both the alleles and were thus R/R genotype. No r/r genotype was found in any of the breeds. In Sarda goats the allelic frequency was 0.98 for R allele and 0.02 for r allele; genotypic frequency was 96.00% for R/R genotype and 4.00% for R/r genotype. A strong link emerged from statistical analysis (P<0.001) between R/r genotype and reproductive activity, which was strongly influenced by photoperiod. Sequencing indicated six nucleotide changes that did not induce any amino acid change. Data showed that polymorphism was present and that it influences reproductive activity only in the Sarda breed.