Mehraban Ewes Research Articles

The Effect of Injection of GnRH Dissolved in Aluminum Hydroxide Gel Nanoparticles or Propyleneglycol on Estrus Synchronization, Ovulation Induction and Fertility Outcome after Artificial Insemination in Mehraban Ewes

The Effect of Injection of GnRH Dissolved in Aluminum Hydroxide Gel Nanoparticles or Propyleneglycol on Estrus Synchronization, Ovulation Induction and Fertility Outcome after Artificial Insemination in Mehraban Ewes

Screening for causative mutations in ovine BMPR1B and BMP15 genes and their homologous fragments in human.

The BMPR1B and BMP15 genes are well known for their considerable associations with prolificacy in sheep. These genes may also affect fertility or prolificacy in other species, including human. This study was conducted to investigate possible causative mutations in BMPR1B and BMP15 genes in human and an indigenous breed of sheep. Blood samples were collected from 83 singleton- and prolific Mehraban ewes and 81 infertile, singleton- and twin-bearing women. A 190-bp fragment, containing the FecB mutation in ovine BMPR1B, a 380-bp fragment in ovine BMP15 gene and their homologous fragments in human were amplified and then investigated by single-stranded conformation polymorphism and DNA sequencing methods. The FecB mutation of BMPR1B (g.159A>G) was detected in the sheep population, but no polymorphic loci were found in the homologous fragment in studied human samples. The studied fragments of BMP15 were monomorphic in both sheep and human samples. A total of nine and 69 point-differences in the studied fragments of BMPR1B and BMP15 genes were detected between the species, respectively. In sheep, the G allele of BMPR1B had a positive effect on litter size (p<0.05), whereby all AG or GG ewes were prolific. The FecB mutation for the first time was detected in Mehraban sheep and therefore could be considered for marker-assisted selection in this breed. The studied fragments of BMPR1B and BMP15 genes are not responsible for reproduction variation in human. More studies on other genes, associated with fertility in human, are necessary in the future.

The effect of pre-breeding vitamin E and selenium injection on reproductive performance, antioxidant status, and progesterone concentration in estrus-synchronized Mehraban ewes.

The present study was conducted to assess the effects of pre-breeding vitamin E and selenium (ESe) injections on the reproductive performance, antioxidant status, and serum progesterone (P4) concentration in estrus-synchronized Mehraban ewes. During the breeding season, 38 ewes (3-4years) were divided into two groups (n = 18), and the synchronization of estrus was achieved by intravaginal insertion of 0.3g progesterone CIDR device for 13days followed by 350IU eCG at CIDR withdrawal. Ewes were kept under pasture conditions and exposed to Mehraban rams 48h following CIDR withdrawal. The experimental treatments were control and ESe injection. The ESe group was received three intramuscular (5mL) injections of Ese (0.5mg/mL of selenium as sodium selenite and 50IU vitamin E as DL-α- tocopheryl) once every 2weeks. Specifically, Ese was administered at 2weeks before CIDR insertion, at the times of CIDR insertion and CIDR withdrawal. Fertility, prolificacy, lambing rate, and birth weight were recorded after parturition. Blood samples were collected at CIDR insertion, CIDR withdrawal, 5, 10, and 15days after ram exposure. Fertility, prolificacy, lambing rate, and birth weight did not improve by Ese treatment, but viabilityof lambs was higher in ESe than control (P < 0.05). Serum total antioxidant capacity at day 5 and P4 at day 10 after ram exposure was higher in ESe than control (P < 0.05). In conclusion, sheep breeders can use ESe at CIDR insertion and withdrawal times to potentiate antioxidant status and progesterone profile of estrus-synchronized Mehraban ewes.

Detection of single nucleotide polymorphisms at major prolificacy genes in the Mehraban sheep and association with litter size

Abstract The present study aimed to investigate the presence of polymorphisms at four known genes controlling ovine prolificacy i.e. BMP15, GDF9, BMPR1B and B4GALNT2 in a sample of 115 Iranian Mehraban ewes and their association with litter size (LS) and lambs’ birth weight (BW) traits. Using Sanger sequencing of exons and polymorphism specific genotyping, ten SNPs (Single Nucleotide Polymorphisms) were observed in only two genes, GDF9 and BMPR1B. Seven SNPs were found in the GDF9 gene on the chromosome 5. Among them, six were already described in the coding sequence, and a new one (g.41840985C&gt;T) was found in the 3’UTR. In the BMPR1B gene on the chromosome 6, three novel SNPs were detected in the exon 7 (g.29382184G&gt;A; g.29382337G&gt;A and g.29382340G&gt;A). Allelic frequencies were established for six SNPs among the ten identified and they were in Hardy-Weinberg equilibrium. A significant association was found between the novel SNPs found in the exon 7 of BMPR1B and LS. Present results indicate the potential role of the BMPR1B locus in controlling prolificacy of Mehraban sheep and provide genetic markers for further exploitation in selection to improve reproductive efficiency.

The Effect of Maternal Supplementation of Zinc, Selenium, and Cobalt as Slow-Release Ruminal Bolus in Late Pregnancy on Some Blood Metabolites and Performance of Ewes and Their Lambs.

The aim of this study was to determine the effect of the supplementation of a slow-release bolus of zinc (Zn), selenium (Se), and cobalt (Co) at late gestation (6week prepartum) on performance and some blood metabolites of Mehraban ewes and their lambs until weaning. Seventy pregnant ewes, 6weeks prior to expected lambing, were randomly divided into two groups (35 heads each) including (1) control group and (2) slow-release bolus group. Blood samples of ewes were obtained on day 10 prepartum and 45 and 90days postpartum, and milk samples were collected on day 45. Blood samples of lambs were collected on days 10, 45, and 90. Body weight at birth and weaning and average daily gain were higher and percentage of mortality and white muscle disease rate were lower in lambs whose mothers were given a bolus (P < 0.05). Slow-release bolus administration increased serum alkaline phosphatase and whole blood glutathione peroxidase activity, plasma concentrations of Zn, Se, and vitamin B12 in ewes and their lambs (P < 0.05). In addition, serum creatine phosphokinase activity of lambs whose mothers were given bolus was lower (P < 0.05). Serum concentration of T3 in bolus given ewes and their lambs was higher (P < 0.05) and serum T4 concentration was lower (P < 0.05). Zinc, Se, and vitamin B12 concentrations in milk were significantly higher in treated ewes (P < 0.05). Obtained results showed that maternal supplementation of zinc, selenium, and cobalt as slow-release ruminal bolus in late pregnancy improved some mineral status of ewes and their lambs until weaning and led to higher body weights of lambs at weaning.

Extensive analysis of milk fatty acids in two fat-tailed sheep breeds during lactation.

The profile of fatty acids (FA) in the milk fat of two Iranian fat-tailed sheep breeds, Sanjabi and Mehraban, was compared during lactation. Eight ewes of each breed, balanced in parity and carrying one foetus, were selected before parturition. Ewes were kept separated in individual pens during the experimental period, under the same management practices and fed the same diet, in order to eliminate any confounding effects on milk FA profile. Milk was sampled at biweekly intervals up to 10weeks of lactation, starting 2weeks after parturition. More than 100 FA were determined in milk fat by means of gas chromatography. The milk fat of Sanjabi ewes contained more cis-9 18:1, that of Mehraban ewes was richer in 10:0, 12:0 and 14:0, and no differences were found for 16:0 and 18:0. No breed differences were found for most branched-chain FA. Mehraban ewes showed a higher presence of vaccenic and rumenic acids in their milk fat. The milk fat of Sanjabi ewes had a lower atherogenicity index and n-6/n-3 FA ratio. The contents of several FA showed time-dependent changes, so breed differences were more apparent or disappeared as lactation progressed. The milk fat of Sanjabi ewes showed a better FA profile from the human health point of view.

Estimation of genetic parameters for reproductive traits in Mehraban sheep

Genetic parameters for basic and composite reproductive traits in Mehraban sheep were estimated. Data included 10 257 records on reproductive performances of 5813 lambs from 69 sires and 603 dams which were collected from 1994 to 2011 in the Mehraban breeding station in Hamedan province, western Iran. Studied traits were litter size at birth (LSB), litter size at weaning (LSW), litter mean weight per lamb born (LMWLB), litter mean weight per lamb weaned (LMWLW), total litter weight at birth (TLWB), and total litter weight at weaning (TLWW). Test of significance to include fixed effects in the statistical model was performed using the GLM procedure of SAS. Genetic parameters were estimated with univariate and bivariate repeatability animal models using WOMBAT program. Direct heritability estimates were 0.16, 0.14, 0.03, 0.16, 0.06, and 0.18 for LSB, LSW, LMWLB, LMWLW, TLWB, and TLWW, respectively, and corresponding repeatabilities were 0.02, 0.01, 0.73, 0.41, 0.27, and 0.03. The estimate for animal-dependent permanent environmental variance ranged from 0.01 ± 0.04 for LMWLW to 0.23 ± 0.04 for LSB. Genetic correlation estimates between traits ranged from −0.98 for LSB–LMWLW to 0.99 for LSB–TLWB. Phenotypic and environmental correlations were generally lower than genetic correlations. Phenotypic correlations ranged from −0.50 for LSB–LMWLB to 0.85 for LMWLW–TLWW. Environmental correlations ranged from −0.45 for LSB–LMWLB to 0.87 for LMWLW–TLWW. The results suggested that indirect selection based on TLWW could improve the reproductive performance in Mehraban ewes more effectively than if based on the other traits.

Patterns of milk production, blood metabolite profile and enzyme activities of two fat-tailed sheep breeds

This study was conducted to compare milk yield and composition, blood parameters and enzyme activities between two fat-tailed Iranian breeds of sheep (Mehraban and Sanjabi). Two groups of eight ewes per breed were kept indoors and fed a diet based on alfalfa hay (60%) and concentrates (40%). Milk production of the individual ewes was measured and sampled weekly for 11 weeks and blood samples were obtained at 28, 56 and 77 days of lactation. No significant differences between the breeds were evident in average daily milk production and fat and lactose contents, but average milk protein content tended to be higher (P = 0.05) in Mehraban than in Sanjabi ewes. However, milk and protein yields were higher (P &lt; 0.05) in Mehraban ewes in the last two-thirds of lactation. Plasma lipid profile (triglyceride, cholesterol, HDL- and LDL-cholesterol) was not different between the two breeds at any time of study. At the end of lactation, plasma urea contents and alanine amino transferase activities were higher (P &lt; 0.05) either before or after feeding in Mehraban than in Sanjabi ewes, which suggests a more intense metabolic activity in the former probably related to their higher milk and protein production at that stage of lactation.

Association of BMPR-1B and GDF9 genes polymorphisms and secondary protein structure changes with reproduction traits in Mehraban ewes

BMPR-1B and GDF9 genes are well known due to their important effects on litter size and mechanisms controlling ovulation rate in sheep. In the present study, polymorphisms of BMPR-1B gene exon 8 and GDF9 gene exon 1 were detected by single strand conformational polymorphism (SSCP) analysis and DNA sequencing methods in 100 Mehraban ewes. The PCR reaction forced to amplify 140 and 380-bp fragments of BMPR-1B and GDF9 genes, respectively. Two single nucleotide polymorphisms (SNPS) were identified in two different SSCP patterns of BMPR-1B gene (CC and CA genotypes) that deduced one amino acid exchange. Also, two SNPS were identified in three different SSCP patterns of GDF9 gene (AA, AG and GG genotypes) that deduced one amino acid exchanges. Two different secondary structures of protein were predicted for BMPR-1B exon 8, but the secondary protein structures predicted for GDF9 exon 1 were similar together. The evaluation of the associations between the SSCP patterns and the protein structure changes with reproduction traits showed that BMPR-1B exon 8 genotypes have significant effects on some of reproduction traits but the GDF9 genotypes did not have any significant effect. The CA genotype of BMPR-1B exon 8 had a significant positive effect on reproduction performance and could be considered as an important and new mutation, affecting the ewes reproduction performance. Marker assisted selection using BMPR-IB gene could be noticed to improve the reproduction traits in Mehraban sheep.

The modulatory role of cortisol on prolactin secretion in anestrus Iranian fat-tailed ewes

Release of prolactin, a milk-secreting hormone, is normally inhibited by the neurotransmitter dopamine. Numerous attempts have been made to explain the effects of environmental stress on the level of prolactin, proposing a basic role for cortisol in the modulation of the hormone secretion. The pharmacologic properties of antagonists in the release of prolactin, during the anovulatory early postpartum period, were examined in this research. This study included ten 3-year-old Mehraban ewes that gave birth to their third lambs, at least 2 weeks before the experiment. Each animal was randomly assigned to receive either a corresponding dose of either metoclopramide (0.3 mg/kg BW; im; n = 5) or haloperidol (0.1 mg/kg BW; im; n = 5). During the 2 weeks prior to the start of the study, all ewes were allowed to acclimatize to their environment with free access to food and tap water, in order to avoid stress-induced influences on hormone levels resulting from environmental factors. Blood samples were collected from each ewe through the jugular vein via intravenous catheter immediately at the time of study entry, 2 and 4 h before and after every injection, with a time interval of 30 min. The serum recovered was assayed for prolactin, cortisol, and progesterone. Animals were assumed to be anestrous if the mean serum level of progesterone was lower than 0.4 ng/mL and that of prolactin higher than 80 mIU/L. One-way ANOVA revealed that the mean serum concentrations of prolactin measured at 30 and 90 min after metoclopramide administration were statistically different compared with the control but showed no difference at other time points. The secretion of cortisol prior to the treatment and afterward was statistically similar; however, under haloperidol administration, it increased and the difference was statistically significant (p 0.05). In conclusion, the pharmacologic properties of an antagonist to release prolactin, during the anovulatory early postpartum period, may depend on the presence of dopaminergic D2 receptor subtypes. In addition to its specificity for D2 receptors, the bioactivity of that antagonist may also play a role in the control of the secretion.

Effect of a Calcium Soap of Fatty Acids on Reproductive Characteristics and Lactation Performance of Fat-Tailed Sheep

Experiments were carried out to study the effect of feeding Megalac, calcium soaps of fatty acids (protected fat), on reproduction and lactation of sheep. In the first experiment, 20 Ghezel and 20 Mehraban cyclic fertile ewes (4-5 years old) were randomly allotted to 4 groups. The control group was fed with a balanced ration and the other groups received the same diet as well as a daily allowance of 40 g non-protected fat (NP), 40 g protected fat (LP), or 80 g (HP) protected fat. The ewes were fed with their respective rations for one cycle length. Blood samples were collected and analyzed for progesterone (P4), cholesterol (CHOL), High Density Lipoproteins (HDL), Low Density Lipoproteins (LDL) and triacylglycerols (TG). The ewes were slaughtered on their next estrous period and the size and number of follicles in ovaries were recorded. There were no significant effects of feeding fat on ovarian weights, cycle length and follicular numbers in each class, or on the size of the largest follicle. Serum concentrations of P4, CHOL, TG and HDL were greater for HP ewes as compared with the control ewes (p<0.05). In the second experiment, effects on lactation and lamb performance of feeding protected fat during mating, late gestation and early lactation were studied in Mehraban ewes. Milk and fat yields on day 25 of lactation were significantly increased by feeding protected fat. Protected fat resulted in lower weight loss in ewes and a higher lamb birth weight. Average daily weight gain of lambs from birth to day 60 and the weaning weight of lambs were increased by feeding protected fat (p<0.05). In conclusion, calcium soaps of fatty acids increased serum P4 between days 10 to 14 of the cycle which may be beneficial to early pregnancy maintenance. Protected fat seemed to have a beneficial effect on milk yield, fat yield, lamb daily gain, lamb birth weight and ewe weight loss.

Effect of Sulfates in the Diet of Pregnant Ewes on Plasma Concentrations of Copper and Ceruloplasmin in Newborn lambs

The effect of short-term experimentally elevated dietary sulfates on copper status of heavy pregnant ewes and their newborn lambs was studied. Sixteen pregnant Mehraban ewes, 4-4.5 years old, were fed a basal diet containing 0.19% sulfur, 8 PPM copper and 3.9 PPM molybdenum from about the 100th day of pregnancy till 3 days postpartum. During the last 25 days of pregnancy, the animals were fed individually and 10 ewes (the experiment group) received 0.38% extra sulfur as sulfate daily in their diet. Liver copper concentration of ewes was determined at about the 100th day of pregnancy and on the 3rd day postpartum. Plasma concentrations of copper and ceruloplasmin were measured weekly before parturition and also at the 1st hour and on the 3rd day after lambing. Concentrations of copper and ceruloplasmin were also measured in plasma of newborn lambs at the 1st hour (before sucking colostrum) and again on the 3rd day after birth. In ewes of the control group, liver copper concentration increased significantly (p 0.05), which could be due to increased requirements during heavy pregnancy together with the effect of sulfates in reducing the availability of dietary copper. This decline, however, was not sufficient to produce even marginal deficiency. No significant difference was observed in plasma concentrations of copper and ceruloplasmin between the two groups. In newborn lambs, plasma concentrations of both copper and ceruloplasmin were similar at birth. On the 3rd day, however, plasma copper was significantly lower in the lambs of the experiment group (p<0.05). This may be related to the lower concentration of ceruloplasmin in their blood. It is concluded that sulfates, in short terms, may not result in copper deficiency in pregnant ewes, but may affect copper metabolism in newborn lambs. Routine experiments conducted on adults to detect copper deficiency seem not to be proper for predicting these changes in newborn lambs. ORAL GLYCEROL AS A GLUCONEOGENIC PRECURSOR IN THE TREATMENT

Effect of daily oxytocin injection on milk yield and lactation length in sheep

The effects of daily oxytocin (OT) (2 IU) injection (i.m.) on lactation performance of 25 Mehraban ewes were studied. Eight control ewes were injected with 1 ml of saline. Eight ewes were injected with OT after weaning (POT), and nine ewes were injected with OT from day 15 of lactation (WOT). Total milk production for WOT ewes was 55.5 and 24.7% greater ( P<0.05) than for control and POT ewes, respectively. POT group produced 24.7% more milk than control group. Lactation length was 175 days for WOT and POT groups, and 143 days for control ewes. Daily milk yield after weaning was greater for WOT and POT as compared with control ewes. WOT lambs had a greater daily weight gain as compared with POT and control lambs. WOT ewes lost more weight during the suckling period, but the difference in ewe live weight loss after weaning was not significant between the experimental groups. Fat content as a percentage of milk dry matter was greater for WOT than for control and POT ewes. Milk density, pH, freezing point, and protein, lactose and ash contents were not affected by OT treatment. Somatic cell count (SCC) was greater for control than for POT and WOT groups and increased as lactation progressed. The results of this experiment support the hypothesis that OT may be involved in mammary cell maintenance and metabolism, in addition to causing myoepithelial cell contraction and milk letdown.

Breeding season and oestrous activity of Iranian fat-tailed Mehraban ewes and ewe lambs

This study was conducted in four successive breeding seasons (1986–1989) of oestrous activity in Iranian fat-tailed Mehraban ewes and ewe lambs. The ewe lambs normally attained puberty in their first year of life, and their age at first oestrus averaged 212 (s.d. 7.3) days. Ewe lambs had a shorter breeding season (3–4 months) than ewes (8–11 months), with great individual variation. They exhibited shorter oestrous cycles than ewes (15.7 ± 0.7 days vs. 17.2 ± 0.9 days) and had more silent heats, resulting in less regular cyclic activity. A shorter duration of oestrus (heat) in ewe lambs than in ewes was observed (32.8 ± 1.7 h vs. 37.6 ± 1.2 h). Body weight and year did not significantly affect these traits. Repeatability estimates for the onset and cessation of the breeding season and the duration of anoestrus (0.45, 0.53 and 0.48, respectively) showed that these traits are moderately repeatable. In contrast, the repeatability estimate for the length of oestrus was low (0.11). The study concluded that Mehraban sheep could be considered as a breed with a long breeding season with an optimal oestrous activity in summer and autumn. This characteristic might be exploited for out-of-season lambings.

Lamb growth performance of Iranian fat-tailed Karakul, Mehraban and Naeini breeds of sheep and their crosses with Corriedale and Targhee rams

SUMMARYBirth weights, weaning weights (75 days of age) and pre-weaning average daily gains of 291 lambs and post-weaning average daily gains, feed conversions and market weights of 136 ram lambs were studied. The lambs were of three fat-tailed Iranian breeds of sheep, Karakul, Mehraban and Naeini, and their crosses with Corriedale and Targhee rams.The crossbreds were significantly superior to the purebreds in all the traits studied, by approximately 7% in the pre-weaning traits and up to 18·4% in the post-weaning daily gain. Among the purebreds, Mehraban lambs were superior to the other two breeds in the preweaning traits and final weight.The progeny of the Targhee and Corriedale rams were similar in performance except for feed conversion, in which the lambs sired by Targhee rams were more efficient. Breed of dam had a significant effect on the pre-weaning traits and feed conversion. Mehraban ewes produced lambs with the highest pre-weaning average daily gain and weaning weight among the crossbreds, but they were the least efficient lambs after weaning.Age of dam significantly influenced the pre-weaning but not the post-weaning traits. Lambs born to 4-yr-old ewes were the heaviest and those born to 2-yr-old ewes were the lightest at birth. The lambs reared by 2-yr-old ewes had significantly lower rates of growth and were the lightest at weaning. Sex had a highly significant effect on the pre-weaning traits in favour of the male lambs.