twinning rate

Effect of short-term feeding high energy diet along with eCG and hCG injection on follicular dynamics, blood metabolites, double ovulation and twinning rates in Naeini ewes was evaluated. For this purpose, 45 Naeini ewes (3-4 years old) were randomly assigned to 3 experimental groups: 1- Maintenance diet + eCG (Me), 2- Short-term high energy diet + eCG (HEe) and 3- Short-term high-energy diet + eCG and hCG (HEeh). All ewes were synchronized by inserting intravaginal progesterone sponges for a period of 12 days during the breeding season. The short-term feeding was started 4 d before until 1 d after sponge removal (for a 6 d period). The eCG injection was done 1 d before sponge removal and hCG injection was done on the day of sponge removal and 1 d later. Results showed that regardless of the kind of hormone injection, feeding high energy diet increased (P<0.05) the medium and large follicles population. The HEe and HEeh groups had higher (P<0.05) serum glucose, cholesterol and insulin, but lower (P<0.05) serum urea nitrogen compared with Me group. In HEe and HEeh groups, (P<0.05) serum oestradiol decreased before sponge removal and increased (P<0.05) after that. The HEeh ewes had highest (P<0.05) twinning rate (42.9%). In general, short-term feeding (6-day) high energy diet along with chorionic gonadotropins injection improved the follicular development, blood parameters and reproductive performance in Naeini ewes.

The litter size is a threshold trait that is controlled by many genes. Due to the low heritability (0.10), of litter size, classical breeding methods lead to slow genetic progress. Hence it is essential to use new technology to improve this trait. Length of chromosome 1 in goat is approximately 186 cM. Based on previously published data in addition to a high genetic homology between goat and cattle choromosome 1, a region between 16 to 169 cM of chromosome 1 was selected for QTL detection of litter size in the Markhoz goat breed. Sample population included 8 paternal half-sib families. The numbers of half-sib offspring per buck ranged from 30 to 40. All individuals were genotyped by six microsatellites specific to chromosome 1. QTL analyses were performedusing multiple regression method under a half-sib model. Our study indicated that a QTL in position 165 cM on chromosome 1 affect litter size rate in Markhoz goats. Its location was near to CSSM19 marker and was able to explaining 2.20 percent of the genetic variance of litter size. The QTL detected in this research could be related with POU1F1 gene. Hence this gene could be a candidate for the associated QTL on goat chromosomes 1.