Ewe Traits Research Articles

Dietary inorganic chromium improved wool traits of Ossimi ewes

Dietary inorganic chromium improved wool traits of Ossimi ewes

Effect of PITX2 gene polymorphism on growth traits in Awassi ewes

Effect of PITX2 gene polymorphism on growth traits in Awassi ewes

Genome-wide associations with longevity and reproductive traits in U.S. rangeland ewes.

Introduction: Improving ewe longevity is an important breeding and management goal, as death loss and early culling of mature ewes are economic burdens in the sheep industry. Ewe longevity can be improved by selecting for positive reproductive outcomes. However, the breeding approaches for accomplishing this come with the challenge of recording a lifetime trait. Characterizing genetic factors underpinning ewe longevity and related traits could result in the development of genomic selection strategies to improve the stayability of sheep through early, informed selection of replacement ewes. Methods: Towards this aim, a genome-wide association study (GWAS) was performed to identify genetic markers associated with ewe longevity, reproductive, and production traits. Traits evaluated included longevity (i.e., length of time in the flock), parity and the lifetime number of lambs born, lambs born alive, lambs weaned, and weight of lambs weaned. Ewe records from previous studies were used. Specifically, Rambouillet (n = 480), Polypay (n = 404), Suffolk (n = 182), and Columbia (n = 64) breed ewes (N = 1,130) were analyzed against 503,617 SNPs in across-breed and within-breed GWAS conducted with the Bayesian-information and Linkage-disequilibrium Iteratively Nested Keyway (BLINK) model in R. Results: The across-breed GWAS identified 25 significant SNPs and the within-breed GWAS for Rambouillet, Polypay, and Suffolk ewes identified an additional 19 significant SNPs. The most significant markers were rs411309094 (13:22,467,143) associated with longevity in across-breed GWAS (p-value = 8.3E-13) and rs429525276 (2:148,398,336) associated with both longevity (p-value = 6.4E-15) and parity (p-value = 4.8E-15) in Rambouillet GWAS. Significant SNPs were identified within or in proximity (±50kb) of genes with known or proposed roles in reproduction, dentition, and the immune system. These genes include ALPL, ANOS1, ARHGEF26, ASIC2, ASTN2, ATP8A2, CAMK2D, CEP89, DISC1, ITGB6, KCNH8, MBNL3, MINDY4, MTSS1, PLEKHA7, PRIM2, RNF43, ROBO2, SLCO1A2, TMEM266, TNFRSF21, and ZNF804B. Discussion: This study proposes multiple SNPs as candidates for use in selection indices and suggests genes for further research towards improving understanding of the genetic factors contributing to longevity, reproductive, and production traits of ewes.

A comparative Study of the Productive Traits of Drinking Thermally Stressed Awassi Ewes with Tap and Well Water before and after their magnetic treatment

This study was conducted in the sheep field of the Department of Animal Production-Faculty of Agriculture - University of Kirkuk for the period from 15/6/2021 to 15/9/2021. The study targeted the role of different water types in influencing some of the productive traits of ewes exposed to heat stress in the summer. 20 mature ewes were used at the age of 18 months with an average weight of 44.12 kg. The animals were divided into four groups, each group included five ewes of homogeneous weights, and randomly divided then the coefficients into groups. The 1st treatment was orally administrated with tap water, the 2nd treatment was orally administrated with well water, the 3rd treatment was orally administrated with tap water treated magnetically (1500 gauss) and the 4th treatment was orally administrated with well water treated magnetically (1500 gauss). Both magnetically treated tap and well water groups showed a significant increasing (P≤0.05) in the weight of ewes, an average weight gain, a decrease in the amount of feed intake and an improvement in the coefficient of nutritional conversion.

A study on the Determination of Some Reproductive Traits of Ewes and The Growth Performance of Lambs Akkaraman Raised under Farm Conditions in the Province of Niğde

In this study, the reproductive and growth performance of Akkaraman sheep between 2017-2021 were evaluated within the scope of the National Sheep and Goat Breeding Project in the Hand of the Public, which is being carried out in the province of Nigde. In the research, data obtained from 30923 animals in 22 farms in 7 villages in the central district of Nigde province were used. In the study, the effect of year, dam’s age, gender and birth type on birth weight (BW), live weight on day 60 (LW1), live weight on day 120 (LW2), daily live weight gain (DLWG) on day 120 were investigated. The effects of year, dam’s age, gender and birth type on BW, LW1, LW2, DLWG were found to be statistically significant. While the effects of year, dam’s age and gender were found to be statistically effective on SR, the effect of birth type was found to be insignificant. In the study, fertility, fecundity and litter size in Akkaraman lambs were determined as 0.92, 1.03 and 1.13, respectively. As a result, remarkable progress has been achieved in Akkaraman lambs in terms of performance characteristics (LW1, LW2 and DLWG) between 2017 and 2021.

One intron variant in the oocyte expressed protein (OOEP) gene is associated with twinning rate, prolificacy, and several body measurement traits in Awassi ewes

Awassi breed is an important sheep in the Middle East, but its lower twinning potential is a limitation against improvement. Due to the dynamic role of oocyte-expressed protein (OOEP) gene in controlling folliculogenesis, this study was conducted to evaluate the possible association between OOEP and twinning rate, as well as body measurement traits, in Awassi ewes. A total of 232 Awassi ewes (123 ewes-producing singletons and 109 ewes-producing twins) were included in this study. Three PCR fragments (OOEP-1 to OOEP-3) were designed to cover the majority of OOEP sequences and genotyped by single-strand conformation polymorphism (SSCP) method. One nucleic acid variant was identified in the intron-2 of OOEP-3, or rs430263839:A>G. Ewes with rs430263839:AG genotype showed variable significant values of larger head length, chest and abdominal circumferences, and higher prolificacy and twinning rates than ewes with the rs430263839:AA genotype. The conducted computations predicted that the detected SNP had caused altered splicing mechanisms in ewes with rs430263839:AG genotype. The increased abdominal and chest diameters in ewes with the rs430263839:AG genotype were thought to help the uterus accommodate more lambs. The predicted splicing alteration caused by this SNP is the putative mechanism by which these ewes may improve reproductive and productive traits. This is the first study that demonstrated the importance of OOEP as a potential biomarker for the twinning rate, prolificacy, and some body measurement traits in Awassi ewes with an opportunity to be introgressed to other breeds using large-scale association analysis.

Molecular markers for thermo-tolerance are associated with reproductive and physiological traits in Pelibuey ewes raised in a semiarid environment

Pelibuey sheep exhibit reproductive activity through the year, but warm weather lowers their fertility and demonstrates physiological limitations of environmental heat stress. Single nucleotide polymorphisms (SNPs) associated with heat stress tolerance in sheep have been reported previously. The objective was to validate the association of seven thermo-tolerance SNP markers with reproductive and physiological traits in Pelibuey ewes raised in a semiarid region. Pelibuey ewes were assigned to a cool (January 1st.– March 31st.; n = 101) or warm (April 1st.– August 31st.; n = 104) experimental group. All ewes were exposed to fertile rams and assessed for pregnancy diagnosis 90 days later; lambing day was reported at birth. These data served to calculate the reproductive traits of services per conception, prolificacy, days to estrus, days to conception, conception rate and lambing rate. Rectal temperature, rump/leg skin temperature and respiratory rate were measured and reported as physiological traits. Blood samples were collected and processed to extract DNA, which was genotyped using the TaqMan allelic discrimination method and qPCR. A mixed effects statistical model was used to validate associations between SNP genotypes and phenotypic traits. The SNPs rs421873172, rs417581105 and rs407804467 were confirmed as markers associated with reproductive and physiological traits (P < 0.05), and these SNPs were in the genes PAM, STAT1 and FBXO11, respectively. Interestingly, these SNP markers resulted as predictors for the evaluated traits but only in ewes from the warm group, which indicated their association with heat-stress tolerance. An additive SNP effect was confirmed with the highest contribution (P < 0.01) of the SNP rs417581105 for the evaluated traits. Reproductive performance improved (P < 0.05) and physiological parameters decreased in ewes carrying favorable SNP genotypes. In conclusion, three thermo-tolerance SNP markers were associated with improved reproductive and physiological traits in a prospective population of heat-stressed ewes raised in a semiarid environment.

A Novel c.100C > G Mutation in the FST Gene and Its Relation With the Reproductive Traits of Awassi Ewes.

Reproductive traits are affected by many factors, including ovarian function, hormones, and genetics. Genetic polymorphisms of candidate genes are associated with reproductive traits. Several candidate genes are associated with economic traits, including the follistatin (FST) gene. Thus, this study aimed to evaluate whether the genetic variations in the FST gene are associated with the reproductive traits in Awassi ewes. The genomic DNA was extracted from 109 twin ewes and 123 single-progeny ewes. Therefore, 4 sequence fragments from the FST gene were amplified using polymerase chain reaction (PCR) (exon 2/240, exon 3/268, exon 4/254, and exon 5/266 bp, respectively). For a 254 bp amplicon, 3 genotypes were identified: CC, CG, and GG. Sequencing revealed a novel mutation in CG genotypes c.100C > G. The statistical analysis of c.100C > G showed an association with reproductive characteristics. Ewes carrying the c.100C > G had significantly (P ⩽ .01) lower litter sizes, twinning rates, lambing rates, and more days to lambing compared with CG and CC genotypes. Logistic regression analysis confirmed that the c.100C > G single-nucleotide polymorphism (SNP) is responsible for decreasing litter size. According to these results, the variant c.100C > G negatively affects the traits of interest and is associated with lower reproductive traits in Awassi sheep. As a result of this study, ewes carrying the c.100C > G SNP have lower litter size and are less prolific.

Novel variants associated with adiponectin-related traits in Awassi ewes

BackgroundAdipose tissue secretes adiponectin (ADIPOQ), a hormone related to fat oxidation, glucose metabolism, and reproduction. The polymorphism of adiponectin is associated with productive traits in domestic animals. Thus, this study investigated the association of adiponectin gene polymorphism with lipid profile and reproductive hormones in Awassi ewe. In this study, 200 ewes between the ages of 2.5 and 5 years, neither pregnant nor lactating, were included. To determine the lipid profile and reproductive hormones, sera were separated from the blood. DNA extraction, genotyping, and sequencing reactions were used to verify the variants in the amplified fragments (exon 1).ResultsThree genotypes, CC, CA, and AA, were identified from 368 bp amplicons (exon 1). A sequencing reaction revealed a novel mutation, c.198473337C > A, in the CA genotype. The results revealed significant differences (P ≤ 0.05) in cholesterol and HDL levels in the AA genotype than CC and CA genotypes. The AA genotype had higher estradiol and progesterone levels (50.52 ± 0.64) (pg/ml) and (7.10 ± 0.04) (ng/ml), respectively, than those with the CC and CA genotypes.ConclusionsThese results conclude that the ADIPOQ gene affects lipid profiles and sex hormone levels in Awassi sheep. Choosing sheep that are polymorphic for the ADIPOQ gene should be a future study, as this gene could be linked to high prolificacy.

Polymorphism of the ADIPOQ gene and its association with productive traits in Awassi Ewes.

Adiponectin (ADIPOQ) plays a critical role in energy and lipid metabolism, indicating that adiponectin could affect livestock productivity. There is an association between polymorphisms in the ADIPOQ gene and variations in livestock productive traits. Therefore, this study investigated the relationship between ADIPOQ polymorphism and productive traits in Awassi ewes. This study included 200 sexually mature ewes, aged 2.5 to 5 years, non-pregnant and not lactating. A phenotypic measurement consisting of live weight and body dimensions, was taken. Samples of blood were taken for extraction of genomic DNA and PCR-SSCP based genotyping, followed by sequencing to confirm variants in amplified fragments. A novel c.198,473,337C > A SNP was found in exon 1 of the ADIPOQ gene confirming heterogeneity with genotypes AA, CC, and CA. The AA genotype differed significantly (P < 0.05) by comparison with the CA and CC genotypes concerning live body weight and body measurements. An association between productive traits and the c.198,473,337C > A SNP revealed a significant association of the A allele (odds ratio: 2.22 (95% CI: 0.94-5.30) in the additive genetic model. Sheep with the AA genotype were heavier and had larger body dimensions, implying superior production and reproduction. Further studies are required in other breeds to prove the results.

Impact of breeding for reduced methane emissions in New Zealand sheep on maternal and health traits.

Enteric methane emissions from ruminants account for ∼35% of New Zealand’s greenhouse gas emissions. This poses a significant threat to the pastoral sector. Breeding has been shown to successfully lower methane emissions, and genomic prediction for lowered methane emissions has been introduced at the national level. The long-term genetic impacts of including low methane in ruminant breeding programs, however, are unknown. The success of the New Zealand sheep industry is currently heavily reliant on the prolificacy, fecundity and survival of adult ewes. The objective of this study was to determine genetic and phenotypic correlations between adult maternal ewe traits (live weight, body condition score, number of lambs born, litter survival to weaning, pregnancy scanning and fleece weight), faecal and Nematodirus egg counts and measures of methane in respiration chambers. More than 9,000 records for methane from over 2,200 sheep measured in respiration chambers were collected over 10 years. Sheep were fed on a restricted diet calculated as approximately twice the maintenance. Methane measures were converted to absolute daily emissions of methane measured in g per day (CH4/day). Two measures of methane yield were recorded: the ratio of CH4 to dry matter intake (g CH4/kg DMI; CH4/DMI) and the ratio of CH4 to total gas emissions (CH4/(CH4 + CO2)). Ewes were maintained in the flocks for at least two parities. Non-methane trait data from over 8,000 female relatives were collated to estimate genetic correlations. Results suggest that breeding for low CH4/DMI is unlikely to negatively affect faecal egg counts, adult ewe fertility and litter survival traits, with no evidence for significant genetic correlations. Fleece weight was unfavourably (favourably) correlated with CH4/DMI (rg = −0.21 ± 0.09). Live weight (rg = 0.3 ± 0.1) and body condition score (rg = 0.2 ± 0.1) were positively correlated with methane yield. Comparing the two estimates of methane yield, CH4/DMI had lower heritability and repeatability. However, correlations of both measures with adult ewe traits were similar. This suggests that breeding is a suitable mitigation strategy for lowering methane yield, but wool, live weight and fat deposition traits may be affected over time and should be monitored.

Evaluation of the BMPR-1B gene functional polymorphisms and their association with litter size in Qinghai Tibetan sheep

The Bone morphogenetic protein receptor-1B (BMPR-1B) was one of the most major candidate gene for sheep follicular development and litter size trait. The BMPR-1B gene encoded a structural and functional highly conserved transmembrane protein related to sheep reproductive performance. To further validate its genetic effect, genotype-phenotype associations were performed in Tibetan sheep. Through DNA sequencing of the entire coding region of the BMPR-1B gene using DNA of 30 unrelated Tibetan ewes (10 Singletons Tibetan ewes, and 20 Twins Tibetan ewes). And genotyping the target SNPs loci using PCR-RFLP (or PCR-SSCP) combined with DNA sequencing and analyzing their association with lambing traits in 510 Tibetan ewes. One mutation in 3′UTR (A1354G) and three mutations in exons (G192A, A746G, T864C) were found to be strongly associated with lambing traits in Tibetan ewes in this study. χ2 suitability test showed that all of SNPs were Hardy-Weinberg equilibrium. After independence test, A746G, T864C and A1354G of BMPR-1B gene polymorphisms were significantly correlated with litter size in all-types of Tibetan sheep. These results indicate that the variations in the BMPR-1B genes and their corresponding genotypes may be considered as marker-assisted selection (MAS) for litter traits in Tibetan sheep breeding.

Association of OLR1 gene polymorphism with live body weight and body morphometric traits in Awassi ewes: short communication.

Oxidized low-density lipoprotein receptor 1 (OLR1) is an endothelial receptor that binds and degrades oxidized low-density lipoproteins (Ox-LDL), thus having a physiological role in metabolism. Polymorphisms in the OLR1 gene are associated with animals with different production traits. Due to this, the study aimed to determine if OLR1 polymorphisms in Awassi ewes associate with live body weight and body measurement. In this study, 200 ewes between the ages of 2.5 and 5years, not pregnant or lactating, were selected. Phenotypic measurements including live body weight and body measurements were collected. A sheep's blood was collected to extract genomic DNA, genotyped, and sequenced to confirm the presence of the variants that arose from the amplified fragments. One novel C246A single nucleotide polymorphism (SNP) was identified in the OLR1 gene (exon 3) that assigned two genotypes CC and CA. The study indicated significant differences (P ≤ 0.05) in live body weight and body measurements of the genotype CC compared with the genotype CA. The genotype CC correlated positively with live body weight, height at shoulder, height at hip, chest girth, and chest width (r = 0.67, P = 0.02), (r = 0.54, P = 0.03), (r = 0.61, P = 0.02), (r = 0.53, P = 0.01) and (r = 0.66, P = 0.04) respectively. Sheep with the CC genotype had a higher live body weight and larger body measurement, making them better for productivity. These genotypic data and associations can be used to better select sheep for future marker-assisted selection programs.

A novel p.K116Q SNP in the OLR1 gene and its relation to fecundity in Awassi ewes

Sheep's fecundity is determined by both twinning rate and litter size, both influenced by several genes, one of which is the OLR1 (oxidized low-density lipoprotein receptor) gene. This study aimed to determine the genetic variation of the OLR1 gene affecting the fecundity traits of Awassi ewes. The genomic DNA from 114 ewes with a single progeny and 86 ewes with twins was extracted. Polymerase chain reaction (PCR) was used to amplify three fragments (334 bp, 291 bp, and 274 bp) (exon 3, exon 4, and exon 6) of the OLR1 gene. Two genotypes of 334-bp amplicons – CC and CA – were detected. In a sequence reaction, the novel mutation p.K116Q was discovered in CA genotypes. There was a highly significant (P ≤ 0.01) association between the single nucleotide polymorphism (SNP) and reproductive traits, in that ewes with the p.K116Q SNP had lower litter size, twinning rate, fecundity, and lambing percentages than ewes with the CC genotype. These observations imply that the missense p.K116Q variant has an adverse effect on the traits under study and show that p.K116Q SNP has a negative influence on fecundity traits in Awassi sheep. Based on the findings of this study, it is clear that ewes with the p.K116Q SNP are associated with reduced litter size and reduced fecundity traits for this population.

Identifikasi Sifat-Sifat Kualitatif Warna Bulu, Bentuk Tanduk, dan Bentuk Ekor pada Domba Priangan Betina di SP3TDK Tambak Mekar Kabupaten Subang

Qualitative trait is one of indicators of selection that can be used as a phenotypic character of a breed. There are many traits that are usually observed to include hair color, horn shape, and tail shape. The research about “Identification of Qualitative Traits of Hair Color, Horn Shape, and Tail Shape of Priangan Ewes in SP3TDK Tambak Mekar Subang Regency” was conducted to determine the qualitive traits of Priangan Ewes in SP3TDK Tambak Mekar Subang Regency. The research conducted for ten days from January 6 st 2020 to January 17 st 2020. The method used in this research was survey and data collections were conducted by census method to look at the parameters of hair color, horn shape, and tail shape of Priangan Ewe in SP3TDK Tambak Mekar Subang Regency. The results showed that Priangan Ewes in SP3TDK Tambak Mekar Subang Regency were dominated by white hair color (81,82%), combination hair color (13,64%), black hair color (4,54%), and brown Priangan Ewe was not found (0%). The horn shapes of Priangan Ewe in SP3TDK Tambak Mekar Subang Regency were dominated by unhorn (68,18%), muser (27,27%), and small horn (4,54%). The tail shapes of Priangan Ewe in SP3TDK Tambak Mekar Subang Regency were dominated by tail shape ngabuntut beurit (86,36%) and ngabuntut bagong (13,64%). In conclusion, SP3TDK Tambak Mekar Subang Regency has Priangan Ewes with the majority qualitative traits of white hair color, unhorn, and ngabuntut beurit .

A novel association between hemoglobin subunit beta gene and reproductive performance in Awassi ewes

Abstract This study was performed to assess the polymorphism in the HBB gene and its association with reproductive traits in Awassi ewes. Genomic DNA extracted from 124 and 100 Awassi ewes, respectively, produced single and twins. We amplified three exons in the HBB gene (exon 1, exon 2, and exon 3) to obtain the band (204 bp, 251 bp, and 222 bp) by PCR. Two genotypes were determined in 251 bp amplicon, AA and AG genotypes. Sequencing reactions detected a novel mutation in AG genotype, c.51983514 A > G, with a missense effect of p.K65R. A highly significant (P ≤ 0.01) association of p.K65R SNP with reproductive traits (especially composite reproductive traits, twinning rate, prolificacy and litter size) was reported, in which sheep having p.K65R SNP had a lower composite reproductive traits, twining rate, prolificacy and litter size than those without this SNP. This negative influence of p.K65R SNP was also confirmed by cumulative predictions performed by several in silico tools, which indicated a strongly deleterious impact of p.K65R SNP on hemoglobin. In conclusion, the interesting negative effect of p.K65R SNP has a considerable effect on reproductive performance (especially composite reproductive traits, twinning rate and prolificacy as well as litter size) in Awassi sheep. This manuscript strongly suggests the need to exclude ewes having p.K65R SNP when high values from higher reproductive performance are required.

Amasya İlinde Yetiştirilen Karayaka Koyunlarının Bazı Döl Verim Özellikleri ve Kuzuların Büyüme Performanslarının Belirlenmesi

This study was carried out to determine the growth and reproductive performance of Karayaka sheep in Amasya province within the scope of National Animal Breeding Project. Data were collected from 17529 Karayaka lambs of 20120 Karayaka sheep which were born during 2012 to 2015 birth season. In this study, the live weights, survival rates of the lambs in various periods and reproductive traits of Karayaka ewes were investigated. In this study, the live weights, daily live weight gain, survival rates (90th day) and reproductive traits of Karayaka ewes were investigated. The averages of reproductive traits of Karayaka sheep such as infertility, fertility, twins, fecundity, litter size and survival rate were 13.8%, 86.2%, 7.20%, 0.867, 1.01 and 89.0% respectively. The effects of year, sex and type of birth on the birth weights and the live weights of 90 days (weaning) of Karayaka lambs were found to be significant. Daily live weight gain was affected only by year and sex.

The Effects of Different Levels of Sunflower Hulls on Reproductive Performance of Yearly Ewes Fed with Pelleted Complete Diets

In this study, 84 pregnant ewes were used and randomly distributed to one of four treatments, as follows: C (control), total mixed ration (TMR) +12% SFH (S12), TMR +20% SFH (S20), and TMR +28% SFH (S28). Treatments had a significant (p &lt; 0.05) effect on the daily feed intake (DFI) of the ewes during the late gestation (30 d prepartum) and post-partum period, with the S12 and S20 groups having lower feed intake (35; 60%) than the C and S28 group. The DFI was significantly (p &lt; 0.05) low during late gestation in comparable with other periods. The results revealed that body weight (BW) at late gestation was significantly (p &lt; 0.05) higher than the BW at 60-days postpartum and during the mating period. Body condition score (BCS) was significantly (p &lt; 0.05) higher during late gestation in comparison with other periods. There was no significant effect of different levels of SFH on reproductive parameters except S/C, which was significantly higher in the S20 than other groups. Serum glucose level was significantly (p &lt; 0.05) higher in the S20 group than the C, S12, and S28 groups during 30 days postpartum. S20 and S28 groups showed a significant (p &lt; 0.05) increase in glucose levels at parturition in comparison with other reproductive periods. At late gestation, a significantly (p &lt; 0.01) higher concentration of blood NEFA was reported for ewes from the C group compared with other groups. Furthermore, significantly lower (p &lt; 0.05) NEFA levels at parturition were found for ewes from the S20 group compared with the S12 group. In conclusion, TMR is not preferable to be used alone in the late gestation period. Sunflower hull can be used as a cheap source of fiber in TMR without adverse effects on health or the reproductive traits of ewes. The increasing level of sunflower hull up to 28% can affect fertility and increase the number of services per conception, probably due to its high content of lignin (phytoestrogen).

Is selection for resistance and resilience to Haemonchus contortus possible in Morada Nova sheep?

Gastrointestinal nematodes (GIN) are a major constraint for sheep production. Selection of animals resistant to GIN infection is an effective and sustainable control strategy. In this study, the possibility of selection for resistance and resilience, as well as potential correlated responses, were evaluated. A total of 256 lambs and 123 ewes were submitted to two consecutive independent artificial infections with 4,000 infective larvae (L3) of Haemonchus contortus. Records of faecal egg count (FEC), packed cell volume (PCV), and body weight (BW) were taken serially until day 42 after infection in both challenges. Estimates of genetic parameters were obtained for individual records (in lambs) and for overall traits (in lambs and ewes) using mixed models. Phenotypic and genetic correlations were estimated between traits in lambs, with genetic correlations being based on estimated breeding values (EBVs). In addition, correlations between FEC in lambs and FEC in ewes, as well as PCV in lambs and ewes, were calculated. Heritability estimates for FEC in the first and second parasite challenge were, respectively, 0.25 ± 0.18 and 0.46 ± 0.19 for lambs, and 0.00 ± 0.09 and 0.20 ± 0.16 for ewes. For PCV, heritability estimates were 0.23 ± 0.14 and 0.32 ± 0.16 for lambs and 0.13 ± 0.11 and 0.37 ± 0.18 for ewes. For the overall daily weight gain (DWG), the heritability estimate was 0.70 ± 0.21. No significant genetic correlation was found between DWG and the other traits, while there was a negative genetic correlation between FEC and PCV (-0.70 ± 0.03). Genetic correlations of FEC and PCV between lambs and ewes were 0.36 ± 0.08 and 0.42 ± 0.08, respectively. The results of the present study suggest that selection for low FEC, high PCV and high BW/DWG is possible in Morada Nova lambs. Furthermore, selection for low FEC should have a correlated response on PCV (leading to higher PCV), while no correlated response is expected on DWG. Selection for low FEC in lambs would, in future generations, lead to higher resistance of lambs and also of ewes. Simultaneous selection for all three traits is possible in Morada Nova lambs, which would increase performance, decrease losses due to parasite infection and reduce the need for anthelmintic treatments, with beneficial consequences regarding selection pressure on parasite populations and productivity.

Productivity and Reproductive Performance of Mixed-Age Ewes across 20 Years of Selection for Ultrafine Wool in Uruguay

This study reports the phenotypic trends for wool, growth, and reproductive traits in mixed-age ewes after twenty years of genetic selection. Data were obtained from the Merino nucleus flock in Uruguay between 1999 and 2020. Overall, the aim of this selection flock was to reduce the fiber diameter (FD) and increase both the clean fleece weight (CFW) and live weight (LW). Data on ewe wool traits, LW, body condition score (BCS), the total number of lambs weaned (TLW), and the total LW of lambs weaned (TWW) across all lambing opportunities (1–8 mating seasons) were analyzed. Between 1292 and 2063 ewes were measured, depending on the trait considered. Ewe FD decreased by approximately 3 µm (19–16 µm), whereas greasy fleece weight (GFW) increased by 0.2 kg. This improvement in wool traits was accompanied by increases in LW at mating (3 kg), decreases in BCS at mating (approximately by 1 unit), and a small positive change in TWW across years. This study demonstrated that increasing farmer income by selecting for finer wool, heavier fleeces, and heavier animals can be obtained without compromising ewe lifetime reproduction.