Mutations in bone morphogenetic protein 15 and growth differentiation factor 9 genes are associated with increased litter size in fat-tailed sheep breeds

The objective of this study was to investigate association between GDF9 and BMP15 gene polymorphism and litter size in fat-tailed sheep, a total of 97 mature ewes from four breeds (Afshari=19; Baluchi=18; Makui=30 and Mehraban=30) were genotyped for the BMP15 HinfI and GDF9 HhaI polymorphisms by PCR-RFLP technique. The highest and lowest mutant allele frequencies were found in Makui (0.27) and Afshari (0.10) sheep for the BMP15 gene and in Afshari (0.24) and Mehraban (0.18) sheep for the GDF9 gene, respectively. Litter size was significantly influenced by genotype of the ewe for two genes (P < 0.01). Heterozygous genotypes for both loci showed higher litter size than homozygous genotypes (P < 0.01). None of the individuals carried homozygous genotype for both of the GDF9 and BMP15 variants in these breeds. The individuals carrying the mutant allele for one of the investigated candidate gene still showed fertile phenotype. Thus, existence of homozygosity at one of the BMP15 and GDF9 variant is not probably able to block normal hormonal pathway of reproduction in fat-tailed sheep.     

Genetic parameters for birth weight,growth, and litter size in Nordic sheep breeds

Abstract

In this study, genetic parameters were estimated for the Danish populations of Danish Marsk, Finnish Landrace, Gotland Pelt and Spel for birth weight (BW), average daily gain until two months (DG2) and litter size (LS). A multivariate animal model was used for estimation of genetic parameters, including fixed effects, both direct and maternal additive genetic effects, common litter effects and permanent environmental effects. Mean birth weight and DG2 ranged from, respectively, 3.39 kg and 262 g to 4.61kg and 286 g. Litter size ranged from 1.60 to 2.07. Direct heritability for BW ranged from 0.12 to 0.24, and maternal heritability for BW was about 0.23 for all breeds. Direct heritability of DG2 ranged from 0.19 to 0.33. The heritability for LS was between 0.08 and 0.13. The significant genetic correlations between the direct and maternal effect on both BW and DG2 were negative. The genetic correlations between the growth traits and LS were not uniform.     

Influence of management system on litter size, lamb growth, and carcass characteristics in sheep.

Three management systems (winter, spring, and late summer) distinguished by season of lambing and management practices were compared for litter size born and weaned and growth and carcass characteristics of lambs. Three sire breeds (Cheviot, Rambouillet, and Suffolk) and three dam breeds (Florida Native, Native-X, and Synthetic-X) were used in 698 matings over a 3-yr period. System affected (P < .01) litter size born. Spring lambing yielded more lambs (1.62) than winter (1.49) and late summer (1.12). The winter-born lambs were lighter but fatter (P < .05), and spring-born lambs were leaner with higher leg conformation and carcass quality scores. The late summer-born lambs were not different from spring-born lambs. Wethers had higher (P < .01) weights off test than ewe lambs (43.9 vs 42 kg) but had lower (P < .01) leg conformation scores, percentage kidney and pelvic fat, yield grade, and dressing percentages. Dam breed effects were significant (P < .05) for average preweaning daily gains with 249+/-5, 201+/-9, and 191+/-9 g for progeny of Native-X, Florida Native, and Synthetic-X, respectively. Single-born lambs had higher daily gains (P < .05) than twins in a preweaning period in all management systems and higher postweaning and lifetime daily gains for winter and spring management systems.     

Relationship between litter birth weight and litter size in six breeds of sheep

Metabolizable energy requirements of the ewe increase during pregnancy due to increases in fetal and maternal metabolism. Fetal metabolism is related to total weight of the fetuses. Fetal number is a primary contributor to fetal weight. Litter birth weight represents the culminated fetal growth of the litter and can be used to estimate the effect of fetal metabolism on energy requirements of the ewe. We hypothesized that litter weight in sheep would increase at a decreasing rate with increasing litter size. Birth weights of lambs born to yearling (11 to 15 mo) and mature ewes (> 34 mo) were collected on litters born to Dorset, Rambouillet, Suffolk, Finnsheep, Romanov, and Composite III ewes mated to produce straightbred lambs. Litter birth weight expressed as a function of litter size increased at a decreasing rate and the quadratic term differed from zero for mature Rambouillet, Suffolk, Finnsheep, Romanov, and Composite III litters (P < 0.042). The quadratic coefficient differed among breeds. In yearlings, litter weight increased at a decreasing rate for Suffolk ewes (P = 0.002). The quadratic term for the relationship between litter weight and litter size did not differ from zero for Finnsheep (P = 0.39) or Romanov litters (P = 0.07). The hypothesis that litter weight increases at a decreasing rate with increased litter size is supported by experimental results.     

Genetic parameters for early lamb survival and growth in Scottish Blackface sheep

The objectives of this study were 1) to estimate the heritability of lamb survival and growth in the Scottish Blackface breed; 2) to examine the relationship between lamb survival and live BW; and 3) to investigate the possibility of using lamb survival in a breeding program for this breed. The data used for the analyses contained information about survival and live BW at different ages on 4,459 animals. The records were collected from 1988 to 2003 in a Scottish Blackface flock. Live BW was recorded every 4 wk from birth to 24 wk. Survival was defined either by perinatal or postnatal mortality (up to weaning at 12 wk), or as cumulative survival to 1, 4, 8, and 12 wk. The pedigree file comprised 1,416 dams and 178 sires. A sire model was used to estimate genetic parameters for binary survival traits. Heritabilities of BW traits, and phenotypic and genetic correlations between BW and between survival and BW were estimated by fitting an animal model. Further, correlations of survival with live BW were estimated by using a Markov chain Monte Carlo threshold model, implemented by Gibbs sampling. The heritability estimates for cumulative lamb survival declined from birth onward (from 0.33 to 0.08), and postnatal survival had a heritability of 0.01. The direct and maternal heritabilities for BW traits ranged from 0.08 to 0.26 and from 0.06 to 0.21, respectively, whereas the maternal environmental component was between 0.04 and 0.16. The genetic correlations between BW traits at different ages were high. The genetic and phenotypic correlations between survival and BW were always positive (ranging from 0.04 to 0.54), so there was no antagonism between these traits. Therefore, it is possible to simultaneously improve both survival and live BW in a breeding program for this breed.     

Different models for evaluation of growth traits and Kleiber ratio in an experimental flock of Iranian fat-tailed Afshari sheep

Records for Afshari sheep were retrieved from data collected between 2000 and 2005 at the Zanjan University experimental flock, at Zanjan, Iran. (Co)variance components and corresponding genetic parameters for birth weight (BW), weaning weight (WW), 6-month weight (W6), average daily gain from birth to weaning (ADGa), from birth to 6 months (ADGb), from weaning to 6 months (ADGc), Kleiber ratio at weaning (WWKR) and Kleiber ratio at 6 months of age (W6KR) were estimated using univariate and bivariate analyses by the DFREML procedure. The Kleiber ratio, defined as growth rate/metabolic weight, has been suggested to be a useful indicator of growth efficiency and an indirect selection criterion for feed conversion. Estimates of direct heritability ( h ²) were 0.23, 0.27, 0.11, 0.22, 0.07, 0.01, 0.13 and 0.06 for BW, WW, W6, ADGa, ADGb, ADGc, WWKR and W6KR, respectively. Maternal genetic effects represented a relatively large proportion of the total phenotypic variance for BW ( m ² = 0.22), whereas maternal permanent environmental effects were significant for W6 ( c ² = 0.15), ADGb ( c ² = 0.16), ADGc ( c ² = 0.14) and W6KR ( c ² = 0.16). Results of bivariate analyses indicated the variable genetic correlations between traits. The largest positive genetic relationships were between adjacent measurements. The moderate estimates of h ² for early growth traits indicate that in Afshari sheep faster genetic improvement through selection is possible for these traits. In order to increase the efficiency of feed conversion, use of Kleiber ratio in selection programmes was recommended.     

Inbreeding impact on litter size and survival in selected canine breeds

Data obtained from the French Kennel Club and the Fichier National Canin were used to estimate the effect of inbreeding on average litter size and survival in seven French breeds of dog. Depending on the breed, litter sizes were 3.5–6.3 puppies and longevities were 7.7–12.2 years. Estimated heritabilities were 6.0–10.9% for litter size and 6.1–10.1% for survival at 2 years of age. Regression coefficients indicated a negative effect of inbreeding on both individual survival and litter size. Although the impact of baseline inbreeding within breeds appears to be limited, the improper mating of close relatives will reduce biological fitness through significant reduction of litter size and longevity.     

Fertility, embryo survival and litter size in lines of Targhee sheep selected for weaning weight or litter size

Conception rate, prenatal survival and litter size were recorded for 444 ewes of two age groups from five lines of grade Targhee sheep: two unselected control lines, HC1 and DC(C); two lines selected for 20 yr for increased 120-d weight, HW and DH(W); and a line selected for 18 yr for increased multiple births, T. Line T was equal or superior to the control lines in conception rate, prenatal survival and litter size in both age groups, although most of the differences were not significant. The W selected lines were inferior to the C and T lines in fertility and tended to be lower in prenatal survival, among mature ewes, resulting in a significantly lower number of lambs born per corpus luteum in the W lines than in the other two groups. Among yearlings, C ewes were non-significantly lower in fertility than T and W ewes, while W ewes were significantly lower than C and T ewes in prenatal survival. The T line ewes had higher overall reproductive performance than either of the other two groups. Ewes with two ovulations had a significantly higher conception rate than ewes with single ovulations. Gestation period was exceptionally uniform with a coefficient of variation of 1.3% and little difference due either to line or litter size. It was concluded that selection for multiple births improved overall reproductive performance, whereas selection for increased growth rate had an adverse effect on several components of reproduction, leading to a net decline in fitness.     

Direct and maternal genetic relationships of lamb live weight and carcass traits in Swedish sheep breeds

Possibilities to include carcass traits recorded at commercial slaughterhouses in the genetic evaluation of sheep in Sweden were investigated by estimating direct and maternal genetic parameters for 4‐month weight (4MW), carcass weight (CW), carcass fatness grade (FAT), and carcass fleshiness (FLESH) using multiple‐trait animal models. Data included two sets of breeds, the so‐called white breeds (Swedish landrace breeds, Texel, Dorset, Oxford Down, Suffolk, East Friesian Milk Sheep, and Swedish crossbred) and the Gotland breed. There were 30 625 observations on 4MW and 5062 observations on carcass traits for the white breeds. For the Gotland breed the numbers were 43 642 and 7893, respectively. The results showed that it is feasible to use field‐recorded carcass traits in the genetic evaluation. To consider the effects of selection and to utilize all information in an optimal way multiple trait animal models should be used. Direct and maternal heritabilities for 4MW and CW varied between 0.04 and 0.18 and heritabilities for FAT and FLESH between 0.21 and 0.29. Direct and maternal genetic correlations between 4MW and CW were high (0.61–0.97). Genetic correlations were higher between the weights and FLESH (0.11–0.62) than between the weights and FAT (?0.23 to 0.40). Genetic correlations between FAT and FLESH were moderate (0.38–0.45). Heritabilities for CW were higher if 4MW was included in the analyses and the effect of selection on 4MW was stronger for CW than for FAT or FLESH. The importance of maternal effects on carcass traits was discussed.     

Genotype by environment interaction for lamb weaning weight in two Norwegian sheep breeds

Genotype x environment interaction (G x E) effects on live weaning weights of lambs were studied by using the 2 breeds Norwegian White sheep (NWS; heavy, long-tailed) and Spel sheep (Spel; lighter, short-tailed) as genetic groups (G). A total of 37,338 NWS lambs and 30,075 Spel lambs born from 1989 to 1999 on 40 farms that kept both breeds together were included in the analyses. Environment was characterized by farm x year (E). In a mixed linear model framework, significance of the random G x E effect and breed-specific environmental variances were tested by using a log-likelihood approach. Directions and magnitudes of the effect were described through variance component estimates. An across-genotype environmental correlation was also used. There was a significant G x E effect on lamb BW; significant breed differences were found for variance of flock x year effects, indicating different phenotypic plasticities with changing flock x year environments, with the NWS being more sensitive to environmental change. Further, the breed-specific residual variance was greater for NWS, indicating that the effects of environmental variation were larger for the weaning weights of the NWS breed within flock and year. Further, the correlation between flock x year effects for the 2 breeds was significantly different from unity (0.82 +/- 0.02), indicating that the common environment is "perceived" differently in the 2 breeds. The best environment for one breed is not necessarily best for the other breed, and vice versa. Solutions of flock x year effects may be used to describe how environmental characteristics such as climate and topography affect the production of different genotypes, and for clustering of environments, thus facilitating improvement of breeding programs and management schemes for domestic and wild ungulate populations.     

The Damara in the context of Southern Africa fat-tailed sheep breeds

Sheep production is one of the most important activities in animal production in tropical regions. Southern Africa (SA) fat-tailed sheep such as the Afrikaner, Namaqua Afrikaner, Nguni, Persian Black Head, Tswana, Pedi, Sabi, and particularly the Damara are important animal genetic resources very well adapted to their harsh home environments. In this review, autochthonous sheep genetic resources of SA are reviewed regarding history and productive performance. A special focus is made to the most internationalized of such breeds: the Damara. The following aspects are reviewed: history, standards, productive performance in SA, and importation to Australia. Finally, a reference is made to the influence of fat-tailed sheep formation of composite breeds such as the Dorper or the Meatmaster.     

Relationship between inbreeding and milk production traits in two Italian dairy sheep breeds

The effects of inbreeding in livestock species breeds have been well documented and they have a negative impact on profitability. The objective of this study was to evaluate the levels of inbreeding in Sarda (SAR, n = 785) and Valle del Belice (VdB, n = 473) dairy sheep breeds and their impact on milk production traits. Two inbreeding coefficients (F) were estimated: using pedigree (F_PED), or runs of homozygosity (ROH; F_ROH) at different minimum ROH lengths and different ROH classes. After the quality control, 38,779 single nucleotide polymorphisms remained for further analyses. A mixed-linear model was used to evaluate the impact of inbreeding coefficients on production traits within each breed. VdB showed higher inbreeding coefficients compared to SAR, with both breeds showing lower estimates as the minimum ROH length increased. Significant inbreeding depression was found only for milk yield, with a loss of around 7 g/day (for SAR) and 9 g/day (VdB) for a 1% increase of F_ROH. The present study confirms how the use of genomic information can be used to manage intra-breed diversity and to calculate the effects of inbreeding on phenotypic traits.     

Responses in ovulation rate, embryonal survival, and litter traits in swine to 14 generations of selection to increase litter size

Eleven generations of selection for increased index of ovulation rate and embryonal survival rate, followed by three generations of selection for litter size, were practiced. Laparotomy was used to count corpora lutea and fetuses at 50 d of gestation. High-indexing gilts, approximately 30%, were farrowed. Sons of dams in the upper 10% of the distribution were selected. Selection from Generations 12 to 14 was for increased number of fully formed pigs; replacements were from the largest 25% of the litters. A randomly selected control line was maintained. Responses at Generation 11 were approximately 7.4 ova and 3.8 fetuses at 50 d of gestation (P < .01) and 2.3 fully formed pigs (P < .01) and 1.1 live pigs at birth (P < .05). Responses at Generation 14 were three fully formed pigs (P < .01) and 1.4 live pigs (P < .05) per litter. Number of pigs weaned declined (P < .05) in the index line. Total litter weight weaned did not change significantly. Ovulation rate and number of fetuses had positive genetic correlations with number of stillborn pigs per litter. Significantly greater rate of inbreeding and increased litter size at 50 d of gestation in the select line may have contributed to greater fetal losses in late gestation, greater number of stillborn pigs, and lighter pigs at birth, leading to lower preweaning viability. Heritabilities of traits were between 8 and 25%. Genetic improvement programs should emphasize live-born pigs and perhaps weight of live-born pigs because of undesirable genetic relationships of ovulation rate and number of fetuses with numbers of stillborn and mummified pigs and because birth weight decreased as litter size increased.     

Inheritance of litter size and its components in crosses between the D'man and Sardi breeds of sheep

Data on ovulation rate, litter size and embryo survival of 364 Sardi (S), D'man (D), S x DS, DS x S, S x D, D X S (F1), F2, D x DS and DS x D ewes mated for first and second lambing to F1 rams were analyzed. Breed group, birth group and season had significant effects on ovulation rate and litter size but not on embryo survival. D'man ewes had the highest ovulation rate (2.79) and litter size (2.00), with an essentially linear increase in each of these variables with percentage of D'man inheritance in the ewe (b = .017 +/- .001 CL and .009 +/- .001 lambs born). Embryo survival was influenced only by the number of ova shed. D'man direct genetic effects were higher (P less than .01) than those of Sardi for ovulation rate (+1.78) and litter size (+1.08) but did not differ for embryo survival (-.07). Maternal effects differed little for any of the three traits. Individual heterosis estimates were negative and significant for ovulation rate but not significant for litter size and embryo survival. Maternal heterosis and epistatic recombination effects were small and not significant for any trait.     

Evaluation of sheep breeds for early growth in tropical north-east Brazil

Summary Three breeds of sheep, Brazilian Somali, Morada Nova and Santa Inês which are indigenous to hot tropical semi-arid north-east Brazil were studied for their early growth. There were large breed differences in size at birth, at the 86th day and at 6 months. The Santa Inês was the largest and the Brazilian Somali the smallest. The type of birth (single vs. multiple) had a profound effect on weight at virtually all stages of growth which was similar for male and female lambs. Sex effects tended to become significant at around the 86th day, female lambs slightly outweighing males but marked sex differences appeared around 6 months when males outweighed females. The 7-day variation in age of lambs when the weights were taken around the 15th day had a marked effect on weight and correction for age would be necessary in future studies. However, the 7-day variation in age around the 86th day and thereafter did not affect the weights. The birth weight and weights at the 15th, 86th and 112 days and at 6 months were significantly correlated.

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Evaluacion De Razas Ovinas Durante Su Crecimiento En La Nordeste Tropical De Brasil

Resumen Se realizó una evaluación de crecimiento precoz de tres razas nativas, Somali Brasilera, Morada Nova, y Santa Inés, razas que habitan la parte nordeste tropical semiárida de Brasil. Se encontraron diferencias marcadas en tamaño al nacer, a los 86 días y a los 6 meses. La Santa Inés fué la más grande y la Somali Brasilera la más pequeña. El tipo de parto (simple-multiplo) tuvo un afecto marcado en el peso virtualmente en todos los estados de crecimiento, efecto que fué similar en hembras y machos. Los efectos de sexo comenzaron a ser significativos alrededor del día 86, lashembras pesaron un poco más que los machos, pero los machos pesaron significativamente más que las hembras alrededor de los 6 meses. Los 7 días de diferencia en edad, cuando los borregos se pesaron alreadedor de los 15 días, tuvieron un efecto marcado, teniendo que hacer correcciones en el futuro. Este efecto no se detectó cuando se pesaron a los 86 días y posteriormente. Los pesos al nacer y el peso a los 15, 86 y 112 días y a los 6 meses se correlacionaron significativamente.

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Evaluation Des Facultés De Developpement Chez Diverses Races De Mouton Dans Le Nord Est Du Brésil

Résumé Trois troupeaux de moutons de races indigènes Somali Brésilien, Morada Nova et Santa Inès adaptées au climat tropical chaud semi-aride du Nord Est du Brésil ont été comparativement étudiés au niveau de leur croissance précoce. On a observé de grandes différences raciales de taille à la naissance, au 86e jour et à 6 mois. Les Santa Inès ont été les plus développés et les Somali brésiliens plus petits. Le type de naissance (gestation simple ou gestation multiple) a eu un effet considérable sur le poids à virtuellement tous les stades de développement, qui a été semblable pour les agneaux mâles et femelles. L'effet du sexe tend à devenir significatif aux alentours du 86e jour, les femelles devenant un peu plus légeres que les mâles aux environs du 6e mois, la différence entre les sexes est plus marquée lorsque les mâles deviennent plus lourds que les femelles. Des variations de 7 jours dans l'âge des agneaux lorsque les poids ont été pris vers le 15e jour ont eu une influence marquée sur les poids et des corrections relatives à l'âge seraient nécessaires lors d'études ultérieures. Quoiqu'il en soit cette variation de 7 jours dans l'âge n'affecte pas les poids lors des pesées au 86e jour ni après. Les poids de naissance et ceux relevés les 15e, 86e et 112 jours ainsi qu'à 6 mois ont des corrélations significatives.

     

Estimation of additive and non-additive genetic parameters for reproduction, growth and survival traits in crosses between the Moroccan D'man and Timahdite sheep breeds

Genetic breed differences, heterosis, recombination loss, and heritability for reproduction traits, lamb survival and growth traits to 90 days of age were estimated from crossing D'man and Timahdite Moroccan breeds. The crossbreeding parameters were fitted as covariates in the model of analysis. The REML method was used to estimate (co)variance components using an animal model. The first estimation of crossbreeding effects for Timahdite and D'man breeds shows that breed differences in litter traits are mainly of maternal genetic origin: +1.04 lambs, +1.88 kg, +0.60 lambs, and +2.23 kg in favour of D'man breed for litter size at lambing, litter weight at lambing, litter size at weaning, and litter weight at 90 days, respectively. The breed differences in lamb growth and survival are also of maternal genetic origin for the majority of traits studied, but in favour of the Timahdite breed: +3.48 kg, +45 g day⁻¹ and +0.19 lambs for weight at 90 days, for average daily gain between 30 and 90 days of age, and for lamb survival to 90 days, respectively. The D'man direct genetic effect was low and negative for survival and birth weight of lambs during the first month of life. All traits studied showed positive heterosis effects. Recombination loss effects were not significant. Therefore, crossbreeding of Timahdite with D'man breeds of sheep can result in an improved efficiency of production of saleable lambs. Heritability estimates were medium for litter size but low for the other reproduction traits. Direct heritabilities were low for body weights and lamb survival at 90 days and the corresponding maternal heritabilities showed, however, low to moderate estimates. For litter traits, the estimates of genetic and phenotypic correlations were positive and particularly high for genetic correlations.