Alleviation of reproductive seasonality in Barki ewes using CIDR-eCG with or without melatonin

Evaluation of the effect of melatonin implantation in rams and eCG dose in ewes synchronized by a CIDR-eCG protocol on reproductive performance of Lacaune sheep breed during non-breeding season

Sustainable production of milk is favorable in dairy sheep industry, which necessitates year-round reproduction of rams and ewes even during non-breeding season. Hence, protocols facilitating reproduction of rams and ewes during non-breeding season are of importance for this purpose. Therefore, the present study was conducted to investigate the effect of melatonin implantation in rams and administration of 400 IU eCG (E400) versus 300 IU eCG (E300) in ewes on reproductive performance of Lacaune sheep breed during non-breeding season. Rams were allocated to two groups including untreated (control, CON; n = 36) and melatonin-treated (MEL; n = 37). A subset of rams from CON (n = 7) and MEL (n = 7) groups were used for assessment of scrotal circumference, kinematic and functional characteristics of sperm, total antioxidant capacity (TAC) of semen and circulating testosterone on Days 0 (the beginning of study) and 60 (60 days after melatonin implantation). Further, the study had a 2 × 2 factorial design with four experimental groups including 1) ewes treated with E300 and introduced to CON rams (E300CON; n = 17 rams and 172 ewes), 2) ewes treated with E300 and introduced to MEL rams (E300MEL; n = 18 rams and 177 ewes), 3) ewes treated with E400 and introduced to CON rams (E400CON; n = 19 rams and 192 ewes), and ewes treated with E400 and introduced to MEL rams (E400MEL; n = 19 rams and 190 ewes). Melatonin implantation improved scrotal circumference, concentration, progressive motility, velocity, mitochondrial membrane potential and viability of sperm, TAC of semen, concentration of testosterone and fertility of rams (P < 0.05). Besides, E400 compared with E300 enhanced synchronization of estrus and fertility in ewes (P < 0.05). In conclusion, melatonin implantation promoted reproductive performance in Lacaune rams, and increase in dose of eCG improved reproductive performance in Lacaune ewes.

The role of melatonin implantation and the associated effect of insulin-like growth factor-1 on milk composition of Barki ewes

ContextManipulation of milk composition in lactating ewes represents an important mechanism by which sheep breeders can improve profits through increased milk prices for cheese making and higher lamb growth rates. To this end, melatonin implantation may affect milk composition by alleviating reproductive seasonality and augmenting insulin like growth factor-1 (IGF-1).AimsThis research aimed to evaluate the effects of melatonin administration on hormone levels and milk composition, and to determine its potential to manipulate milk composition of lactating Barki ewes.MethodsFifty lactating Barki ewes were divided into two groups of 25. One group received 18mg melatonin in a single implant at 40 days after delivery, and the other group served as an untreated control. Over the following 8 weeks, milk components (fat, protein, lactose and total solids percentages), milk energy value, and blood serum hormones including IGF-1 were measured.Key resultsMelatonin implantation increased (P&lt;0.05) IGF-1 concentration, which showed continued elevation (P&lt;0.05) throughout the treatment period (from Day14 to Day56) relative to the control. Analysis of milk composition of implanted ewes revealed higher (P&lt;0.05) milk fat, protein, lactose and total solids percentages as well as milk energy value than in milk of control ewes.ConclusionAn integrated effect of melatonin and IGF-1 successfully improved milk composition of lactating Barki ewes.ImplicationsMelatonin implantation can be used to improve milk composition of lactating Barki ewes, potentially increasing profits from cheese making and lamb production.

Greater concentrations of IGF-1 are associated with increasing pregnancy rate in melatonin implanted anestrous Barki ewes

The present study was conducted to determine if increases in IGF-1 concentration, associated with treatment of ewes with melatonin, has beneficial effects on pregnancy rates when there is induction of estrus in anestrous ewes. A total of 120 multiparous lactating ewes were assigned to three groups (n = 10/group). Ewes of Group 1 were treated with a melatonin implant for 42 days followed by insertion of a controlled internal drug release (CIDR) device for 14 days with administration of equine chorionic gonadotropin (eCG) at day of CIDR removal. The ewes of Group 2 were treated with a CIDR and eCG at the same times as ewes of Group 1 and ewes of Group 3 were assigned to an be untreated control group. Melatonin implantation resulted in an increase in IGF-1 concentrations and lesser estradiol (E₂) and triiodothyronine (T₃) concentrations. Ewes of Groups 1 and 2 had the greatest progesterone (P₄) concentration compared ewes of Group 3. The E₂:P₄ ratio was less in ewes of Group 1 compared Group 3. Melatonin implantation of ewes resulted in a greater pregnancy rate compared to treatment with the CIDR and eCG which, in turn, had a greater rate than ewes of the control group. In conclusion, melatonin implantation modulates the hormonal milieu including P₄, E₂, T₃ and IGF-1 in seasonally anestrous ewes. Increased IGF-1concentrations, as a result of melatonin treatment, are associated with a greater percentage pregnancy rate when there is treatment of anestrous ewes to induce onset of estrus.