Genetic variation of CAST gene in Local Karnobat and Karnobat merino sheep breeds

Karnobat sheep plays an important role in the development of sheep breeding in Southeastern region of Bulgaria. They are valuable source of genetic material. The aim of present experiment was to determine the allele variation of CAST gene in Local Karnobat and Karnobat Merino sheep breeds. A total of 60 blood samples were collected – 30 per breed. DNA was extracted and genotypes of all animals were identified by means of PCR-RFLP technique. The restriction reactions were accomplished by specific enzyme MspI. As expected both breeds were characterized with low level of genetic diversity due to the fact that mostly maintaining selection has been implemented. In Local Karnobat sheep breed was identified only one heterozygous individual from all 30. In Karnobat merino were identified allele M with frequency 0,97 and allele N with frequency 0,03. Genotypes MM and MN were revealed with frequencies 0,93 and 0,07, respectively. According to the statistical analysis both breeds were in HWE equilibrium.

Variations in HIF-1α Contributed to High Altitude Hypoxia Adaptation via Affected Oxygen Metabolism in Tibetan Sheep

The Tibetan sheep is an indigenous species of the Tibetan plateau and has been well adapted to high-altitude hypoxia. In comparison to lowland sheep breeds, the blood gas indicators have changed and the HIFs signaling pathway is activated in Tibetan sheep. These phenotypic and genetic alterations in Tibetan sheep are thought to be an important basis for adaptation to high-altitude hypoxia and variation in genes encoding the subunits that make up HIFs, such as HIF-1α can affect blood gas indicators. In this study, exons 9, 10, 12 of the HIF-1α gene were sequenced to find variations and 3 SNPs were detected, and these 3 SNPs were genotyped by KASP in 341 Hu sheep and 391 Tibetan sheep. In addition, 197 Hu sheep, 160 Tibetan sheep and 12 Gansu alpine merino sheep were used for blood gas indicators analysis. The results showed significant differences between the blood gas indicators of high-altitude breeds (Tibetan sheep and Gansu alpine merino sheep) and low-altitude breeds (Hu sheep), implying that the differences in blood gas indicators are mainly caused by differences in altitude. The haplotype combinations H2H3 and H1H3 were more frequent in the Tibetan sheep population, H2H3 increases O2 carrying capacity by increasing hematocrit and hemoglobin concentrations; H1H3 makes O2 dissociate more readily from oxyhemoglobin by decreasing partial pressure of oxygen and oxygen saturation. These results suggest that variants at the HIF-1α promote the ability of oxygen utilization in Tibetan sheep, which may underpin the survival and reproduction of Tibetan sheep on the Tibetan plateau.

Effects of FecB Mutation on Estrus, Ovulation, and Endocrine Characteristics in Small Tail Han Sheep

The Booroola fecundity gene (FecB) has a mutation that was found to increase the ovulation rate and litter size in Booroola Merino sheep. This mutation is also associated with the fecundity of small-tail han (STH) sheep, an important maternal breed used to produce hybrid offspring for mutton production in China. Previous research showed that the FecB gene affects reproduction in STH sheep, based on litter size records. However, the effects of this gene on estrus, ovulation, and endocrine characteristics in these sheep remain unclear. Here, we analyzed the traits mentioned earlier and compared them among the three FecB genotypes of STH ewes using estrus synchronization. Overall, 53 pluriparous ewes were selected from among 890 STH ewes and subjected to FecB genotyping for experiments to characterize estrous and ovulation rates. FecB heterozygous (+B) ewes presented an earlier onset of estrus (42.9 ± 2.2 h) and a shorter estrous cycle (17.2 ± 0.2 days) (P ≤ 0.05). The ovulation rates increased with the increasing copy number of the B allele (P ≤ 0.01). Ovulation time showed no significant differences among the three FecB genotypes. The serum concentrations of follicle-stimulating hormone (FSH), luteinizing hormone, estrogen (E2), and progesterone (P4) were measured in 19 of the ewes. Serum concentrations of E2 and FSH dramatically varied around the time of behavioral estrus. In FecB mutant homozygous (BB) ewes, E2 concentration had two peaks, which were higher (P ≤ 0.05) than those of ++ genotypes. FSH concentration of BB ewes was higher (P ≤ 0.05) than that of the ++ ewes just after estrus. The expression of the estrogen receptor 1 (ESR1) gene in the +B genotype was higher than in the other genotypes. Based on the data for the reproductive performance of STH ewes with the three FecB genotypes, our study suggests that the development of follicles in ewes with the B allele is dependent on the response to FSH regulated by E2 in the early stage. +B ewes, exhibiting moderate ovulation and litter size and a shorter estrous cycle, can be highly recommended in sheep crossbreeding systems for commercial mutton production. Moreover, this study provides useful information to conserve better and use the genetic resources of STH sheep in China.

Genetic Analysis of Fitness Traits of Kashmir Merino Sheep at Organized Farms of Kashmir

Background: Fitness traits include measures of reproductive efficiency of sheep. The improvement in reproductive efficiency has significant impact on overall economy of sheep. Methods: Data spanning over 21 years (1997-2017) were collected from two sheep breeding farm and analyzed with mixed model least-squares maximum likelihood (LSMLMW) computer (PC-2) programme designed by Harvey (1990) to estimate number of lambs born per ewe (NLBE), number of lambs weaned per ewe (NLWE), litter size (LS) and sex ratio (SR) of Kashmir Merino sheep. Result: Overall estimates of 3.56±0.11, 3.20±0.10, 48.32±0.04 and 1.06±0.01 for number of lambs born per ewe (NLBE), number of lambs weaned per ewe (NLWE), litter size (LS) and sex ratio (SR), respectively were observed in the present study. The period of birth had significant (p less than 0.05) effect on NLBE and NLEE. The effect of sire was highly significant on all the traits under study whereas effect of all the non-genetic factors considered had non-significant effect on LS and SR.