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1.
In this study, the potential association of PrP genotypes with ewe reproductive traits and lamb growth traits was investigated. Data were included on ewes and lambs of the INRA 401 breed from the Bourges-La Sapinière INRA experimental farm. This breed was chosen because of good breeding (prolificacy and maternal abilities) and carcass qualities, and the large number of available animals with performance records and PrP genotypes. Ewes were categorized into 3 PrP genotype classes: ARR homozygous, ARR heterozygous, and animals without any ARR haplotype. Two analyses differing in the traits considered were carried out. Firstly, the potential association of the PrP genotype of ewes with their reproduction traits (fertility, litter size, and ovulation rate) was studied. The data included 801, 779, and 587 genotyped ewes for fertility, litter size, and ovulation rate, respectively. Secondly, the association of the PrP genotype of the ewes with growth traits of their lambs (birth weight, ADG between 10 and 30 d of age) was investigated. The data included 3,749 and 3,512 lambs for birth weight and ADG, respectively. The different traits were analyzed using an animal model, where the PrP genotype effect was included as a fixed effect. The reproductive traits were modeled under a probit or a threshold approach. The results of this study indicate no evidence of an association between PrP genotypes and reproductive and growth traits. It is unlikely that selection for scrapie resistance will have an effect on the reproductive or performance traits studied in the INRA 401 breed.  相似文献   

2.
The objective of this study was to analyze the association between the haplotypes of the prion protein (PrP) locus and several reproductive and lamb weight traits in Ripollesa sheep. Prion protein genotypes were available for a total of 310 sheep (7 rams, 114 ewes, and 189 lambs), all of them belonging to the purebred Ripollesa flock of the Universitat Autònoma of Barcelona, for which all sheep had a known pedigree. In addition, the genotype of 24 historical descendants of the previously genotyped adult individuals was reconstructed, provided that both parents were homozygous for PrP haplotypes. Only 3 haplotypes (ARR, ARQ, and ARH) were observed in the PrP locus of the sheep sampled. Reproductive traits included conception rate and litter size, whereas birth BW and 90-d BW were the lamb weight traits studied. The additive effect of PrP haplotypes was analyzed through Bayesian animal threshold and linear models, for reproduction and weight traits, respectively. Ewe reproductive data belonged to 89 ewes that gave 492 conception rate records and 440 litter size records. Analyses of BW at birth and at 90 d of age were made on 323 and 164 lamb records, respectively. No associations between PrP haplotypes and conception rate and BW traits were observed. For litter size, the effect of the ARH haplotype was greater than that of the ARQ haplotype. Differences between ARH and ARR haplotypes also suggested an advantage for the ARH. As a whole, our results indicated that the selection favorable to increase litter size in Ripollesa ewes may also increase the ARH haplotype frequency, which contradicts the recommendations of the current European Union legislation aiming to increase the genetic resistance to scrapie. As a consequence, scrapie genotyping needs to be included as a new selection criterion in the breed.  相似文献   

3.
This study investigated associations of prion protein (PrP) genotype with body composition and weight traits of Scottish Blackface ewes. Body composition was predicted using computer tomography (CT) scans to estimate muscle, carcass fat, internal fat, and bone weights. The traits were measured at 4 key seasonal production points (pre-mating, pregnancy, midlactation, and weaning) over 4 production cycles (2 to 5 yr old). There were 2,413 records for each of the CT traits measured on 335 ewes, and 26,649 records for each of the body condition score and BW traits for 2,356 ewes. From 1999 to 2004, animals were genotyped to determine polymorphisms at codons 136, 154, and 171, which are associated with scrapie susceptibility. Four alleles were found in the population (ARR, AHQ, ARQ, and VRQ). The data were analyzed using a linear mixed random regression model assuming that the direct additive genetic effect was a 2nd order Legendre polynomial function of time. The PrP genotype was included in the model as a fixed effect along with other fixed factors with significant effects (P < 0.05). Five separate analyses were carried out for each trait, depending on the method of classifying the PrP genotype. In the first analysis, animals were categorized according to the genotype. Only the 5 most common genotypes (ARR/ARR, ARR/AHQ, ARR/ARQ, AHQ/ARQ, and ARQ/ARQ) were included. In the last 4 analyses, animals were categorized according to the number of each PrP allele carried. For CT traits and body condition score, results showed that the PrP genotype has no association with the overall mean of the traits (averaged over age). For BW, ewes without the ARQ allele were at least 0.5 kg heavier than ARQ homozygous and heterozygous ewes. On the other hand, there was a significant interaction between PrP genotype and age of the ewe (i.e., the effect of PrP genotype was not the same at different ages for 5 out of the 6 traits studied). In general, ARQ carrying ewes mobilized more fat reserves at times of nutrient deficiency, such as during lactation, and gained it back more quickly by the mating season (when nutrients became abundant) than non-ARQ carriers. Therefore, selecting against this allele would have consequences on BW and seasonal mobilization of body reserves. The number of VRQ alleles (the most scrapie susceptible allele) carried was not significantly associated with any of the traits.  相似文献   

4.
A total of 147 ewes, 4 rams and 188 lambs of their progeny of the Djallonké breed of sheep were used to study the factors affecting reproductive and growth traits and the causes of lamb mortality. Data on ewes were collected during a 12-month period, while those on the lambs born to 123 of the ewes were collected until they were 12 months of age. The average fertility and abortion rates were 0.84 and 0.09. The fertility rate increased and the abortion rate decreased with increasing age of the ewes (p<0.05). The number of lambs born per ewe joined, litter weight at birth per ewe joined and litter weight at weaning per ewe joined were 1.28, 3.5 kg and 17 kg, respectively. The average numbers of lambs born per ewe, lambs born alive per ewe, lambs born dead per ewe and lambs per ewe that died between birth and weaning were 1.53, 1.43, 0.03 and 0.3, respectively. The age of the ewes significantly (p<0.05) affected all these traits except the number of dead lambs and the index of fertility (94%). The age of the ewes significantly (p<0.05) affected the birth weight and the weight at 6 and 12 months of age, whereas the lambing season significantly (p<0.05) affected all the growth traits studied. The type of birth was the most important source of variation in body weights of lambs. Sex had no significant (p>0.05) effect on the growth traits studied. The complex `starvation–bad management–light body weight at birth' caused 48% of the lamb mortality between birth and weaning, while diarrhoea, pneumonia and internal and external parasites caused approximately 52% of the lamb mortality over the same period. The seasonal raw mortality rate of the lambs before weaning was highest in the humid season.  相似文献   

5.
The ARR allele of the prion protein gene is associated with resistance to classical scrapie, while the ARQ allele is associated with susceptibility. The objective of this study was to estimate the effect, on lamb growth and carcass traits, of replacing an ARQ allele with an ARR allele. Pedigree rams (22 Suffolks, 18 Texels and 18 Charollais) were sourced in pairs, from the same flock (by the same sire where possible), with one member being ARR/ARR and the other being ARQ/ARQ and these rams were progeny tested through single-sire mating in six flocks. Effects of ram genotype on reproductive performance of ewes and on growth and carcass traits of progeny were estimated using mixed model procedures with sire as a random effect. Ram genotype had no effect on litter size at birth or on lamb survival as measured by the number of lambs reared. The differences between the performance of progeny by ARR/ARR and ARQ/ARQ sires provided an estimate of the effect of substituting an ARR allele for an ARQ allele. This allele substitution had no effect on birth weight, growth rate, weight at 5 or 14 weeks, weight or ultrasonic fat depth at 120 days of age or on carcass classification traits (conformation, fatness) for the Suffolk, Texel or Charollais breeds. Substituting an ARR allele for an ARQ allele had a negative effect on ultrasonic muscle depth at 120 days for the progeny of Suffolk rams (P = 0.01) but had a positive effect on ultrasonic muscle depth at 120 days for the progeny of Charollais rams (P = 0.02). The ARR substitution effect was negative for slaughter age in the Suffolk (P < 0.05) and positive for carcass weight in Texel progeny (P < 0.05). The magnitude of these effects was quite small, however, and the overall results support the hypothesis that substituting an ARR allele for an ARQ allele has no important negative effect on lamb growth or carcass traits in any of the breeds examined.  相似文献   

6.
Six ewe genotypes, generated by mating Coopworth (C), Polypay (P), and Suffolk (S) rams to Polypay and Coopworth-type (Ct) ewes, were exposed to Hampshire rams for spring lambing from 1986 through 1990. Data from 1,092 exposures and 1,044 resultant lambings were used to analyze reproductive traits and lamb growth rates. Overall conception rate averaged 95% and ranged from 93% for S x Ct ewes to 97% for P x Ct ewes. Mean litter size at birth averaged 1.63 and ranged from 1.45 for C x C ewes to 1.75 for S x P ewes. Ewes from P dams had higher mean litter size (P less than .01) than those from Ct dams (1.73 vs 1.54), but differences between sire breeds were not significant. Incidence of lambing assistance was similar for ewes producing single or multiple lambs. Lamb birth weight influenced the level of assistance rendered to single-bearing but not to multiple-bearing ewes. Lambing assistance was not related to lamb survival, probably because the high surveillance level minimized trauma before assistance was rendered. Incidence of required assistance declined over subsequent parities. Lamb birth weights were affected by ewe genotype and increased with increasing ewe age. Survival of single-born lambs averaged 94% and was not affected by dam genotype. Survival of twins averaged 85%, ranging from 79% for lambs from S x Ct ewes to 89% for lambs from P x P ewes. Suffolk-sired ewes produced the heaviest mean birth and weaning weights for both singles and twins. Coopworth-sired ewes weaned heavier single lambs but lighter twins than P-sired ewes.  相似文献   

7.
The objective of this study was to investigate and estimate the associations of the ovine prion protein (PrP) genotypes with a wide range of performance traits in Scottish Blackface lambs. Performance records of up to 7,138 sheep of known PrP genotypes born from 1999 to 2004 in 2 experimental farms were utilized. Performance traits studied were BW at birth, marking (when the sheep were identified with permanent ear tags at an average age of 52 d), and weaning (average age of 107 d); slaughter traits (BW at slaughter, slaughter age, carcass weight, and carcass conformation); ultrasonic muscle and fat depths; and computerized tomography-predicted carcass composition and carcass yield at weaning. Different linear mixed models, including random, direct animal effect, and up to 3 maternal effects (genetic, permanent, and temporary environmental) were used for the different traits. The PrP genotype was included in the model as a fixed effect, along with other fixed factors with significant effects (P < 0.05). Five separate analyses were carried out for each trait, differing in the method of PrP genotypic classification. The first analysis was based on classifying the sheep into categories according to all 9 available PrP genotypes. In the other 4 analyses, sheep were categorized according to the number of each PrP allele carried. Results showed that there were no significant differences between PrP genotypes for any of the performance traits studied when all 9 genotypes were compared (first analysis). Similarly, performance of the lambs did not significantly differ between genotypes with different numbers of ARR copies. However, there were significant variations in a few traits with respect to the number of ARQ, AHQ, and VRQ alleles carried. Heterozygous lambs for the AHQ or the ARQ allele were significantly heavier at some ages than lambs of the other genotypes. Lambs carrying the VRQ allele required approximately 10 d longer finishing time (P = 0.01) and yielded carcasses approximately 0.5 kg heavier (P = 0.03) compared with noncarriers. The few significant associations found do not have a negative influence on performance when selecting against the most susceptible PrP allele (VRQ) or in favor of the most resistant one (ARR). Overall, there were no major associations of PrP genotypes with most lamb performance traits in Scottish Blackface sheep.  相似文献   

8.
Data from 364 ewes of 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 breed groups mated to F1 rams were analyzed for fertility, number of lambs born alive, litter size at weaning, litter weight at weaning per ewe joined and mean lamb weight at 60 d. Each ewe was exposed in two seasons and had one or two lambings. Effects of breed group were significant for all traits. The highest number of lambs born alive and litter size at weaning were recorded in D'man (1.84 and 1.45, respectively) and D x DS (1.81 and 1.43, respectively). F1 ewes (S x D and D x S) had the highest fertility (.94) and litter weight at weaning per ewe exposed (13.8 kg). Mean lamb weight at 60 d was highest for S x DS and Sardi ewes (13.4 kg and 13.2 kg). D'man additive effects were positive and significant for number of lambs born alive, litter size at weaning and litter weight at weaning per ewe joined; were significant but negative for mean lamb weight at 60 d; and were not significant, although positive, for fertility. Significant individual heterosis was found for fertility, litter weight weaned and mean lamb weight at 60 d. Maternal heterosis and direct epistatic recombination effects were small for all traits.  相似文献   

9.
The National Scrapie Plan (NSP) for Great Britain includes selective breeding programmes. These aim to reduce the frequencies of the ovine prion protein (PrP) genotypes at high risk of developing clinical disease (principally those containing the VRQ allele) within the national flock, and select for the low-risk ARR-containing genotypes. The aim of this work was to use available data from embryo transfer programmes in guaranteed scrapie-free environments to investigate whether there was a difference in lamb birth weight associated with the lamb's PrP genotype, which might affect survival. The first analysis utilised data from 355 Cheviot lambs born between 2001 and 2004. The analysis was then repeated using a larger data set of 737 Cheviot, Dorset and Suffolk lambs born between 1999 and 2003. The most important determinants of mean lamb birth weight were litter size, sex and recipient ewe breed, plus lamb breed in the three breed analysis. In both analyses the effects of all these variables are consistent and of the same order of magnitude. In the first analysis there was evidence for an apparent increase in mean lamb birth weight for the ARR-containing genotypes of 0.3 kg (95% C.I. 0.1–0.5 kg). Whereas, in the second data set there was evidence for a decrease in mean lamb birth weight for the VRQ-containing genotypes of − 0.6 kg (95% C.I. − 0.8 to − 0.4 kg). This had been masked in the first analysis by the categorisation of these genotypes with the ARQ/ARQ genotype. Within these flocks, in a scrapie-free environment, neither finding provides support for concerns that selection for low risk ARR-containing genotypes would be detrimental to lamb birth weight, which is considered to be the most important determinant of lamb survival. Extension of this work into field flocks, where scrapie-status cannot be easily assured, will require the collection of sufficient data to adjust for known direct effects as well as any additional potential confounding effects.  相似文献   

10.
The roles of recipient and embryo genotype in determining the growth performance and survivability of offspring based on specific behavioural differences were investigated using inter‐breed embryo transfer. This study was carried out using three recipient genotypes (Awassi, Redkaraman and Tuj) and two embryo genotypes (Charollais and Romanov) to obtain the six possible combinations of ewe and lamb genotypes. Data were collected from 71 recipient ewes (10 Redkaraman with Charollais and 15 Redkaraman with Romanov embryos; 10 Tuj with Charollais and 12 Tuj with Romanov embryos, and 12 Awassi with Charollais lambs and 12 Awassi with Romanov embryos); all ewes received two frozen‐thawed embryos. Awassi ewes had a significantly longer duration of the licking/grooming event (25.5 min, p < 0.05) than Tuj ewes. Charollais lambs were significantly (p < 0.05) more likely to require birth assistance compared to Romanov lambs. Romanov lambs were significantly more (p < 0.01) active than Charollais lambs in the first 2 h after birth; ewe breed had no effect on lamb behaviour. There was no recipient breed effect on either birth or weaning weights of lambs. Charollais lambs were recorded with higher birth (5.5 ± 0.3 kg vs 3.9 ± 0.2 kg; p < 0.001) and weaning (29.4 ± 1.2 kg vs 22.4 ± 1.9 kg; p < 0.001) weights compared to Romanov lambs. At weaning Romanov lambs had significantly higher (95% vs 75%; p < 0.05) survival rates, however, this was not significantly affected by recipient breed. It was concluded that recipient breed was not an important factor in survival and weaning performance of embryo transferred lambs from a prolific breed (Romanov) while these traits recorded for lambs from meat type (Charollais) embryos were influenced by dam breed.  相似文献   

11.
Six ewe genotypes, generated by mating Coopworth (C), Polypay (P), and Suffolk (S) rams to P and Coopworth-type (Ct) ewes, were exposed to Hampshire rams for spring lambing from 1987 through 1990. Data from 1,013 exposures and 973 resultant lambings were used to analyze reproductive traits and cumulative ewe productivity over 4 yr. Ewe body and fleece weights were also analyzed. Ewes from S sires weaned the heaviest lambs and ewes from P sires weaned the largest number of lambs, resulting in similar total weight of lamb weaned per ewe mated. Coopworth-sired ewes weaned the least total weight of lamb per ewe mated. Ewes weaning twins produced 54% more total litter weight per ewe than those weaning singles. Annual ewe survival averaged 95%, ranging from 93% for S x P and C x P ewes to 97% for P x Ct and C x Ct ewes. When cumulative number and weight of lamb produced was assessed on the basis of all ewes starting the trial, P-sired ewes were highest, followed in order by daughters of S and C sires. Suffolk-sired ewes (67 kg) were 13% heavier than daughters of P rams and 19% heavier than daughters of C rams. Adjustment of lamb production for ewe metabolic body size resulted in C-sired ewes being more efficient than the heavier S-sired ewes. Coopworth-sired ewes produced 32% more wool than ewes sired by the other two breeds. Differences in wool production between ewes weaning one or two lambs were small.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

12.
A performance evaluation, conducted between 2003 and 2005, compared the milk production of three genotypes of Awassi ewes: Turkish (T), Syrian (S) and the F1-cross between the Turkish and Syrian ewes (TS), at the International Center for Agricultural Research in the Dry Areas (ICARDA) experimental farm in Tel Hadya (northern Syria). After weaning, which occurred at 56days, milk yield and milking length were measured weekly during the milking period (n = 381). Milk yield of TS and T ewes were 12% and 30% higher, respectively, than S ewes. Milk yield and milking length of TS ewes reflected additive inheritance and did not differ from the parental genotypes' average (p ≥ 0.199). Culling of low producing ewes in 2003 and 2004 also resulted in increased milk yield. Dams of all genotypes displayed similar weights at birth (p = 0.898) and weaning (p ≥ 0.677). The latter suggests dams of the different genotypes olerated equally the pre-weaning lactation load. Performance tended to improve as ewes aged, with milk yield and milking length peaking at 3years of age (p > 0.05). Ewe lambing weight, birth–weaning ewe weight decline, litter size, and litter weight weaned peaked at 4–5years of age (p ≤ 0.016). With the exception of birth–weaning ewe weight decline, year effects influenced the traits under study (p ≤ 0.035). Excluding litter size, the best performance was in 2005, followed by 2003 and 2004. Milk yield increased with litter size at weaning (b = 18.7; p = 0.024). The lambing–weaning ewe weight decline (3.6kg) and ewe productivity (0.46kg litter weaned weight per kg ewe weight) did not differ between genotypes (p ≥ 0.178). Average litter size was 1.15, with the TS ewes displaying the largest litter size (1.23; p = 0.026). Single lambs were 25% heavier than twins at birth averaging 4.73kg and 3.8kg, respectively. Male lambs were 4% heavier than female lambs at birth (p < 0.0001) and 9.3% heavier at weaning (p < 0.0001). Lamb birth weights, weaning weights and daily weight gains were similar for all genotypes (p ≥ 0.210). The average proportion of fat (5.95%), crude protein (5.19%) and solids non-fat (11.29%) in the milk varied across genotypes where S < TS < T (p ≤ 0.0037). F1 crosses with T increased the productivity of S ewes by 12.2%. It is noteworthy that this occurred under improved feeding and may not be recommended for other conditions. Culling low producing ewes led to a 12.8% increase in milk yield, which could translate into a substantial boost in revenue for farmers rearing traditional sheep flocks in milk producing areas.  相似文献   

13.
Booroola Merino (BM) and Finnsheep (FS) rams were mated to FS and crossbred (CO) ewes to compare their effects on the productivity of their mates and the performance of their progeny. Effects of breed of ram and the interaction of breed of ram X breed of ewe were no significant for fertility, total number born, number born alive, litter birth weight, or number of lambs weaned by the ewe or in the nursery. Birth weights of FS- and BM-sired lambs were equal, but FS-sired lambs were heavier at weaning and 147 d of age. Compared with BM-sired lambs, survival from birth to weaning of dam-reared lambs was greater for FS-sired lambs produced by CO dams than for FS-sired lambs produced by FS dams. At a constant live weight, FS-sired lambs had a heavier carcass with less external fat thickness than BM-sired lambs. Percentage of ewe lambs reaching puberty was lowest and age at puberty was highest for the BM X CO cross; relatively small differences existed between the other three genotypes for these traits. Ewe lambs sired by BM had a greater ovulation rate than FS-sired ewe lambs. Embryo mortality was greater in BM X CO ewe lambs than in ewe lambs of the other three genotypes; the difference was larger for ewes with three ovulations than for ewes with two ovulations. The net result was that BM X CO ewe lambs averaged slightly fewer lambs born than FS X CO ewes. The BM X FS ewe lambs had larger litters than the FS ewes due to a substantially higher ovulation rate and only a slightly lower overall embryo survival rate. With the exception of ovulation rate and litter size, FS rams produced lambs with a more desirable level of performance than did BM rams.  相似文献   

14.
A resource population of ewes derived from Dorset and Romanov grandparents was generated over 5 yr to provide genotypic and phenotypic data to estimate effects of each callipyge genotype on component traits of reproduction. Effects on ovulation rate were estimated from data recorded by examination of ovaries from serially slaughtered ewe lambs (n = 174) born in 1994 and 1995. Productivity and longevity through 5 yr of age were recorded on a total of 265 F2 ewes produced in 1996 through 1998. Number of lambs born, birth weights, and weaning weights of lambs were calculated for each ewe. Weaning weight was recorded for each lamb and adjusted for age to 56 and 32 d for dam- and nursery-reared lambs, respectively. Longevity was determined as a binary trait based on the presence or absence of the ewe in the breeding flock at 5 yr of age. Ewes generated 937 records for breeding weight and 925 records for conception rate, which was determined on ewes exposed and still present at the start of each lambing season. Seven hundred seventeen records were analyzed for traits based on the number of ewes lambing. Genotypes for the causative callipyge mutation were determined using a matrix-assisted laser desorption/ionization time-of-flight mass spectrometry assay. Each ewe was classified into 1 of 4 genotypes; NMatNPat, NMatCPat, CMatNPat, or CMatCPat, where N represents wild type and C represents the mutant allele. The mean ovulation rate of the ewe lambs genotyped NMatNPat was greater (P < 0.02) than that exhibited by NMatCPat; however, the estimated difference of 0.25 ovum in the ewe lambs did not affect the number born. The live weight of NMatCPat ewes at breeding was 2.5 kg less than that of other genotypes (P < 0.01). The callipyge genotype class did not significantly affect conception rates, fecundity, maternal ability, or ewe longevity. Maintaining a ewe flock to produce homozygous mutant rams for use in terminal sire mating systems presents no unusual problems from a reproduction standpoint.  相似文献   

15.
Scrapie is one of several transmissible spongiform encephalopathies of livestock. Disease susceptibility is linked to polymorphisms in the normal prion protein gene that encodes the mammalian prion precursor. Codon 171 of this gene is a major determinant of scrapie susceptibility. Selection for arginine (R) at codon 171 is encouraged by the USDA to decrease the incidence of scrapie. Objectives of this study were to determine the frequency of R allele variants at codon 171 in a sample of sheep from five breeds (Columbia, Hampshire, Rambouillet, Suffolk, and Targhee) and western white-faced commercial ewes and to determine whether the R allele is associated with ewe and lamb production traits. Genotyping was performed on 532 ewes and 901 lambs from the University of Wyoming flock, in addition to 820 rams from 52 sheep producers from Wyoming and surrounding areas, using a DNA mismatch assay that discriminated the R allele from others at codon 171. Genotyping was performed by DNA sequencing on 127 rams representing all breeds, except Hampshire from the USDA Sheep Experiment Station at Dubois, ID. The 171R allele was found in all five breeds and in the commercial western white-faced ewes. Genotype frequencies varied (P < 0.001) by breed in ewe and ram populations. Influence of R-allele frequency on ewe lambing records and individual lamb records was analyzed for Columbia (62, 161, 121), Hampshire (89, 193, 162), Rambouillet (87, 179, 133), Suffolk (67, 178, 161), and commercial sheep (227, 463, 324) for numbers of ewes, total number of ewe production records, and individual lamb records, respectively. Suffolk ewes without the R allele (non-R/non-R) gave birth to more (P or= 0.08) by ewe genotype. Lamb birth and weaning weights were not influenced (P >or= 0.12) by lamb genotype in any of the breeds or in the commercial flock. In this population, ultimate lamb production was only influenced by genotype at codon 171 in the Suffolk flock.  相似文献   

16.
Objectives of this study were to estimate the magnitude of the effects of various factors associated with ewes and their ram lamb mates on fertility, prolificacy, lamb survival, lamb weaning weight and ewe productivity and to estimate the heritability and repeatability of each trait. Records from 731 ewe-years, 75 ram lamb sires and 616 lambs born from the University of Illinois Rambouillet flock were used. Ewes mated to single-born ram lambs had higher fertility rates (P less than .01), gave birth to lambs with higher survival rates (P less than .01), weaned lighter (P less than .05) individual lambs but weaned more weight of lamb per ewe exposed (P less than .01) than ewes mated to multiple-born ram lambs. Ram lamb breeding weight, ram lamb scrotal circumference, ewe breeding weight and ewe age had relatively large and positive effects on the composite trait of weight of lamb weaned per ewe exposed and significant effects on a number of the component traits. Heritability and repeatability estimates were, respectively, as follows: fertility, 3%, 3%; prolificacy, 34%, 19%; lamb survival, 15%, 8%; lamb weaning weight, 7%, 36%; and ewe productivity, 27%, 10%.  相似文献   

17.
A terminal sire Composite population was formed by mating Columbia rams to Hampshire-Suffolk crossbred ewes. Subsequent generations were produced by inter se mating. The objective was to compare Composite sheep to purebred Suffolks for numerous performance traits. Young ewes lambing at 1 yr of age were evaluated separately from mature ewes (2, 3, 4, and 5 yr old) of each population. Composite and Suffolk populations did not differ significantly in components of litter weaning weight per young ewe joined. Mature Composite ewes produced more wool than Suffolk ewes. Fertility of mature ewes did not differ significantly between populations. The greater prolificacy (P less than .01) of mature Suffolk ewes was offset by a lower survival to weaning (P less than .01), particularly for twin-born lambs. Consequently, mature Composite and Suffolk ewes did not differ for number weaned and litter weaning weight per ewe joined. The average birth weight of lambs born to young and mature Composite ewes was greater (P less than .02) than the average birth weight of Suffolk lambs. The average weaning weight of lambs born to young Composite ewes was greater (P less than .05) than that of lambs born to young Suffolk ewes. Breed differences were not detected for preweaning daily gains, weaning weights, and postweaning daily gains of ewe lambs born to mature ewes. Likewise, weights of ewes at 125 d of age and weights of mature ewes at breeding did not differ significantly between breeds.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

18.
The objective of this study was to compare reproductive efficiency and wool production of 1/4 Finn crossbred ewes with straightbred Columbia, Rambouillet and Targhee ewes. In Phase I, white-faces ewes (WF; Columbia, Rambouillet and Targhee) were bred to either rams of their own breed or Finnish Landrace X Rambouillet rams (F X R) to produce 821 lambs from 563 lambings. Ewes bred to F X R had similar average litter size and individual lamb weights at birth, 60 d and weaning as those bred to WF. Lambs sired by F X R had 7% higher (P less than .01) lamb weaned per ewe lambing for ewes bred to F X R rams. For Phase II, approximately equal numbers of F X R-sired (1/4Fx) and WF-sired female lambs produced in Phase I each year were exposed to Suffolk rams at yearly intervals beginning at 7 mo of age. At 1 yr of age, 1/4Fx had higher fertility (P less than .01) than WF (37.7% vs 1.3%), resulting in 14.0 kg more lamb weaned per ewe exposed to breeding. Mature (ages 2 to 6 yr) 1/4Fx ewes had similar fertility to mature WF ewes, but litter size, number of lambs at 60 d and weaning was .36, .24 and .22 lambs higher (P less than .01), respectively, for mature 1/4Fx. Progeny of 1/4Fx were lighter at birth (P less than .01), but not different (P greater than .05) at 60 d and weaning than those of WF. Survival to 60 d unadjusted and adjusted for birth weight was 4.6% (P less than .05) and 7.6% (P less than .01) higher, respectively, for 1/4Fx progeny than for WF progeny.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

19.
产羔期、补饲水平对考力代羊生产和繁殖性能影响的研究   总被引：2，自引：1，他引：1  
为了研究草地一绵羊系统中草畜供求间的动态平衡，寻求在人工草地放牧条件下适宜的产羔时期及在此时期给产羔母羊的合理补饲水平，１９９０～１９９３年，在贵州省威宁县灼甫联户示范牧场进行了两期产羔期及补饲水平对绵羊生产性能影响的试验。产羔期的改变，导致了母羊及羔羊体重的不同变化趋势。结果显示出母羊体重对其生产、繁殖性能的重要性。春羔母羊配种前体重较之冬羔母羊提高９．７５ｋｇ，两者产羔率分别为１３９．２％和１１６．１％。春羔母羊较高的双羔率导致了春羔母羊较之冬羔母羊更低的繁殖成活率（分别为９１．２％和１０４．７％）。断奶时，春羔较之冬羔体重高５．２５ｋｇ，但断奶以后这种优势即消失了。补饲水平的差异对母羊及羔羊体重有一定的影响，但在牧草丰富的条件下表现得并不很强烈。  相似文献   

20.
This study reports on the phenotypic and genetic (co)variance components for reproductive traits in Zandi sheep, using between 1,859 and 2,588 records obtained from 577 ewes. The data were collected from the Khojir Breeding Station of Zandi sheep in Tehran, Iran from 1994 to 2008. The basic traits were litter size at birth (LSB), litter size at weaning (LSW), litter mean weight per lamb born (LMWLB), and litter mean weight per lamb weaned (LMWLW), and the composite traits were total litter weight at birth (TLWB) and total litter weight at weaning (TLWW). Genetic analyses were carried out using the restricted maximum likelihood method that was explored by fitting the additive direct genetic effects and permanent environmental effects of the ewes as random effects and the ewe age at lambing and lambing year as fixed effects for all of the investigated traits. Akaike’s information criterion was used to choose the most appropriate model. LSB, LSW, LMWLB, LMWLW, TLWB, and TLWW direct heritability estimates were 0.07, 0.05, 0.12, 0.10, 0.08, and 0.14, respectively. The estimated fractions of variance due to the permanent environmental effects of the ewe ranged from 0.03 for LMWLB to 0.08 for LMWLW and TLWW. Corresponding repeatability estimates ranged from 0.10 for LSW to 0.22 for TLWW. Direct genetic correlations varied from ?0.61 for LSB–LMWLB to 0.88 for LSB–LSW and LSB–TLWB. Results indicate that genetic change depends not only on the heritability of traits, but also on the observed phenotypic variation; therefore, improvement of non-genetic factors should be included in the breeding programs.  相似文献   

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