ABSTRACT
This research has two aims: (i) to characterize the coding sequence of the SREBP-1 gene in dairy sheep in order to investigate possible relationships between single nucleotide polymorphisms (SNPs) and milk traits; and (ii) to investigate possible relationship between SREBP-1 gene expression and nucleotide variation. Four hundred adult and multiparous lactating Sarda breed ewes were selected from two farms. Milk samples were collected from Day 30 to Day 150 of lactation to determine the mean yield, somatic cell count, lactose, fat, and protein content of the milk. RNA was extracted from the milk samples, after which the SREBP-1 gene coding regions were amplified and sequenced to scan mutations. Whilst eight SNPs were identified, none had statistically significant association with the analysed milk traits. Moreover, the identified expression patterns were not affected by the SNP or combined genotypes. High SREBP-1 gene expression levels were found to be correlated with high milk fat content (P < 0.01), indicating the crucial role of this gene in the milk fat synthesis. In conclusion, the polymorphisms found within SREBP-1 gene exhibited no significant associations with milk traits or with individual SREBP-1 mRNA expression patterns. The findings thus suggest that this small genetic variability may derive from the selection carried out in Sarda breed to improve milk yield.
ABSTRACT
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.
