Breed and environmental influences on weaner lamb production in Zimbabwe

Performance of the Dorper and Mutton Merino breeds and their crosses was assessed from 1,305 ewe and 1,453 lamb records from six lambing seasons. Dorper and Mutton Merino were mated in all combinations under an accelerated lambing system and crossbred females were mated to Suffolk rams. The Dorper and Mutton Merino breeds were not significantly different for fertility, pre-weaning lamb growth and survival. Suffolk sired lambs from crossbred ewes grew rapidly and were heaviest at birth and at weaning. They also survived better than lambs from the other breeding groups and this contributed to the higher weaning rate (P less than 0.05) in crossbred ewes. Weight of weaned lambs per ewe exposed to the ram per season was 12% higher (P less than 0.05) in the Dorper than the Mutton Merino ewes. However lifetime production was 28% higher (P less than 0.01) in Mutton Merino ewes due to significantly superior longevity. Crossbred ewes were highly productive. Individual heterosis was not significant but estimates were positive for most traits. Growth rate and survival of lambs increased as age of dam increased to 48 and 40 months respectively. Lambs born to previously non-lactating ewes were heavier and survived better than lambs born to ewes lactating in the previous season. Lambs born and reared as singles were 25% heavier at birth (P less than 0.001) and 52% heavier at weaning (P less than 0.001) than those born and reared as twins. Male lambs grew faster and were 7% heavier at weaning than females (P less than 0.001).     

乾华肉用美利奴羊生长规律及生长曲线拟合

乾华肉用美利奴羊是我国新培育的具有肉毛兼用特性的绵羊新品种,为了解舍饲条件下乾华肉用美利奴羊的生长发育规律,分别测定了0～24月龄乾华肉用美利奴公、母羊的体重,运用Logistic和Gompertz两种模型对其体重进行了拟合分析.结果表明:两种模型的拟合度R2均在0.95以上,拟合效果好,其中Gompertz模型对体重的拟合效果优于Logistic模型;乾华肉用美利奴羊公、母羊体重的拐点月龄分别为6.37和2.44个月,拐点体重为49.68和23.02 kg,最大日增重为218.59和249.38 g·d-1;各个月龄的公羊体重显著高于母羊,公、母羊体重绝对生长高峰分别出现在3～6和0～3月龄,与生长模型拟合结果相吻合.本研究结果为指导乾华肉用美利奴羊的早期选育和饲养管理提供了理论参考.     

Mutations in BMPR-IB and BMP-15 genes are associated with litter size in Small Tailed Han sheep (Ovis aries)

The Small Tailed Han is a prolific local sheep breed in China. The bone morphogenetic protein receptor IB (BMPR-IB) gene, which affects the fecundity of Booroola Merino sheep, and the bone morphogenetic protein 15 (BMP-15) gene, which affects the fecundity of Inverdale, Hanna, Belclare, Cambridge, and Lacaune sheep, were studied as candidate genes associated with the prolificacy of Small Tailed Han sheep. Single nucleotide polymorphisms of BMPR-IB and BMP-15 genes were detected in Small Tailed Han ewes (n = 188) by PCR-RFLP. The combined effect of the 2 genes on the prolificacy of Small Tailed Han sheep was studied. The results indicated that the same FecB mutation (Q249R) occurred in the BMPR-IB gene in Small Tailed Han ewes as found in Booroola Merino ewes. The Small Tailed Han ewes with genotypes FecB(B)/FecB(B) and FecB(B)/FecB(+) had 1.40 (P < 0.01) and 1.11 (P < 0.01) more lambs, respectively, than those with genotype FecB(+)/FecB(+). The same FecX(G) mutation (Q239Ter) of the BMP-15 gene was found in Small Tailed Han ewes as in Belclare and Cambridge ewes. The Small Tailed Han ewes with the heterozygous mutant FecX(G)/FecX(+) had 0.55 (P < 0.01) more lambs than those with the wild-type FecX(+)/FecX(+). The Small Tailed Han ewes carrying mutations in both BMPR-IB and BMP-15 genes had greater litter size than those with either mutation alone. In view of our results, marker-assisted selection using both BMPR-IB and BMP-15 genes is warranted to increase litter size in sheep and will be of considerable economic value to sheep producers.     

乾华肉用美利奴羊新品种种质特性的研究

乾华肉用美利奴羊是正在培育的绵羊新品种,对该品种的产区的自然生态条件、品种体型外貌和生产性能指标进行观测和分析,旨在为进一步选育提高提供理论依据和技术参考。结果表明:乾华肉用美利奴羊对东北农牧交错区的自然条件具有良好的适应性;具有优良的生长发育性能、产肉性能、繁殖性能和产毛性能;该品种成年公、母羊的体重可达124.78、103.25 kg,原毛产量和净毛率分别为6.68 kg、49.15%,4.67 kg、48.83%;育成羊和成年羊的羊毛的自然长度均超过9 cm,体侧部的羊毛纤维直径集中在20.32~21.45μm;育成公、母羊的屠宰率和胴体净肉率分别为51.65%和75.45%、51.28%和74.251%;初产和经产母羊的产羔率分别为125.23%和150.21%,羔羊成活率分别为93.12%和95.26%。     

Duration of pregnancy and diurnal distribution of lambing in sheep with different genotypes

Based on 1103 lambings the duration of pregnancy was determined for the breeds German Mutton Merino, German Blackhead Mutton and their Booroola crosses. Furthermore the influence of age and body mass of the ewes as well as number, sex and body mass of the born lambs were considered. German Blackhead Mutton have with 145/146 days on average a 4-5 days shorter duration of pregnancy than German Mutton Merino with 150 days. The examined effects influenced the pregnancy duration only insignificantly or not at all. An influence of the breed, however, was determined. In the pen with limited light during the night all genotypes lambed mostly between 9.00 a.m. and 3.00 p.m. During the day time 12-26% more ewes lambed than during the remaining 12 hours of the day.     

Evaluation of the ovine callipyge locus: IV. Genotypic effects on reproductive traits

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.     

Inhibitory Effect of Selenium Supplementation on the Reproductive Performance in Synchronized Merino Sheep at Range Conditions in a Selenium-deficient Area

The effect of selenium (Se) supplementation on the reproductive performance of Merino ewes mated out of the normal breeding season was studied in a 2 (no Se supplementation vs Se supplementation) × 2 (ewes mated at natural oestrus vs synchronized oestrus) factorial design with 50 ewes per treatment combination. Synchronization of oestrus was achieved by intravaginal insertion of 40 mg cronolone sponges for 14 days and administration of 440 IU PMSG at sponge withdrawal. Se supplementation was by the addition to the concentrate with 0.5 mg/kg of Se in the form of selenomethionin, for the 3 months prior to the mating and during gestation. Ewes were kept under range conditions in south‐west Spain, and exposed to Merino rams at a female: male ratio of 4 : 1 from 2 days following sponge withdrawal, or the equivalent time, for 21 days. Se supplementation alone did not improve significantly ewe fertility or lamb birth weight, but there was a positive effect of synchronizing ewes mated out of the breeding season as more of these ewes lambed and produced more lambs than those not synchronized. However, a strong interaction was found between synchronization and Se supplementation, causing a deleterious effect on the reproductive performance of ewes. This negative effect, presumably related to high embrionary mortality caused by Se toxicity, should be taken into account for oestrus synchronizing in Se‐deficient areas. The supplementation with Se, for the prevention of nutritional myodystrophy degeneration in lambs, should be conducted in a fashion which does not generate high levels of Se in the ewes around the mating period.     

Performance of Djallonké Sheep under an Extensive System of Production in Faranah,Guinea

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.     

The influence of the ovulation rate on ultrasonically determined ovine corpus luteum morphometry and progesterone concentrations in cyclic and early pregnant sheep

The objective of the present study was to describe morphology and function of the Corpora lutea (CL) during the oestrous cycle and early pregnancy in sheep with different ovulation rates. In total 40 Booroola. Mutton Merino crosses [heterozygous carriers (FecBFec+) and non-carriers (Fec+Fec+) of the Booroola-fecundity gene (FecB)] with ovulation rates 1 to 4 were examined. During the oestrous cycle (n = 20) and the first month of pregnancy (n = 20) blood samples were taken daily (radioimmunoassay of progesterone) and an ultrasonic ovary diagnosis was conducted. The ewes were scanned transrectally with a 7.5 MHz linear probe lying in a dorsal position. During every examination the CL could be detected. The number and the diameter of the CL were documented and the total volume of luteal tissue per ewe was calculated. The effect of the ovulation rate on CL-morphology (diameter and total volume of luteal tissue per ewe) and peripheral progesterone concentrations were assessed by one-way ANOVA. On day 6 and 7 post ovulationem in cyclic and early pregnant sheep 42% of the diagnosed CL had a cavity. On day 11 (cyclic sheep) and day 10 post ovulationem (early pregnant sheep) this number decreased to 22% (p < 0.05). Both conditions of the CL (compact or with a central cavity) are similar in function and should be regarded as appearances of the same basic process. From the third day onwards the ovulation rate influenced significantly (p < 0.05) the development of the outside diameters of the CL. However, the ovulation rate had no effect on the total volume of the luteal tissue per sheep and on the progesterone concentrations. Yet, in sheep with the ovulation rate 1 significantly lower progesterone concentrations were determined than in sheep with the ovulation rates 2 to 4. In sheep with the ovulation rates 2 to 4 the peripheral progesterone concentrations did not differ significantly. In cyclic and pregnant sheep there is a positive correlation (r = 0.75, p < 0.05) between the progesterone concentration and the total volume of luteal tissue. Considering the smaller diameters of the preovulatory follicles it seems that the development of the CL continues until a threshold-value of progesterone and/or of the total luteal tissue is exceeded. Ewes with low ovulation rates reach this threshold-value with only a few but large CL. With increasing ovulation rate the CL tend to have smaller diameters.     

The reproductive performance of Finn × German Mutton Merino and purebred German Mutton Merino Ewes

The sexual season, i.e. the sexual cycle activity, of Finn × German Mutton Merino (Finn × GMM) ewes was found to extend from August to March. In a group of purebred German Mutton Merino (GMM) ewes the sexual season extended from June to January.After July–August and October–November lambings, 90–95% of the Finn × GMM crosses renewed postpartum sexual activity within 90 and 75 days, respectively. Only 40% of the November lambing purebred GMM ewes started new cycles within 105 days postpartum.The responsiveness of the Finn × GMM ewes to hormonal treatment was high (90–100%) during different months of the year. The fertility at the synchronized or induced oestrus was 60–75% throughout the year, with a mean litter size of 2.0 lambs per lambing.     

An Ultrasonographic Method to Study Reproductive Seasonality in Ewes Isolated from Rams

In studies concerning the seasonality in sheep, the effect of the teaser-ram, which can by itself induce oestrus as well as the development of ovary function bodies, has not been considered. In this study, a method is developed to determine ovarian activity during the year while excluding a possible influence of the ram. The study was carried out on 10 German Blackhead Mutton ewes (GBM) and 10 German Mutton Merino ewes (GMM) and lasted for 14 months. The ewes were kept without contact with any ram, and once a week a transrectal ultrasonography was conducted to determine ovary function bodies (corpora lutea, follicles) and a blood sample was taken to analyse progesterone (P4) concentration. In both breeds, the number of ovulating ewes, the ovulation rate (OR), the size of the corpora lutea (CL) and P4-concentrations showed significant seasonal fluctuations. During the main breeding period (September-February), the OR was higher (2.0 +/- 0.4) than during the rest of the year (1.6 +/- 0.5). Outside the main breeding season (March-August), approximately 40% GBM ewes and only approximately 15% GMM ewes produced CL. The cycle and the related seasonal changes in the P4-concentration coincide with different ultrasonically diagnosed CL (developing or regressing, insufficient, no CL). Between the volume of fully developed CL and P4-concentration, correlations of 0.57 (GMM) and 0.45 (GBM), respectively, were found. On average, P4-concentration in September to February was by approximately 1.60-1.66 nmol/l in the GMM and by approximately 1.80-1.86 nmol/l in the GBM higher than in spring and summer. Considering the OR, the P4-values corresponded with the CL volumes, i.e. in the months from August to February the CL values were significantly larger than in the months March to August. The ultrasonic ovarian diagnosis is a useful method to determine the ram-uninfluenced seasonality of reproduction in sheep.     

Comparison of Booroola Merino and Finnsheep: effects on productivity of mates and performance of crossbred lambs

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.     

提高低产羊群产肉性能的技术研究

本试验对所有细度在60s以上的基础母羊全部采用"新吉"细毛羊配种改良;细度在60s以下的基础母羊,分别用德国肉用美利奴、白头萨福克、无角道赛特、夏洛莱和特克赛尔五个品种的肉用公羊杂交,试验结果表明,用肉羊品种与本地羊杂交能显著提高子代的产肉性能,其中以德国肉用美利奴的改良效果最好,德肉美公羊的细度达60～64s,对产毛性能较差的母羊有明显的改良作用。     

Evaluation of Dorset, Finnsheep, Romanov, Texel, and Montadale breeds of sheep: II. Reproduction of F1 ewes in fall mating seasons

Objectives were to estimate effects of sire breed (Dorset, Finnsheep, Romanov, Texel, and Montadale), dam breed (Composite III and northwestern whiteface), mating season (August, October, and December), ewe age (1, 2, and 3 yr), and their interactions on reproductive traits of F1 ewes. A total of 1,799 F1 ewes produced 3,849 litters from 4,804 exposures to Suffolk rams during 35-d mating seasons over 3 yr. Ewes were weighed at breeding. Conception rate and ewe longevity (present or absent at 42 mo of age) were determined. Number born and litter birth weight were recorded, and number and weight at weaning and 20 wk of age were analyzed separately for dam- and nursery-reared litter mates. Total productivity through 3 yr of age for each ewe entering the breeding flock was calculated as the sum of 20-wk weights for dam- or nursery-reared lambs. Interactions of sire breed x mating season, sire breed x ewe age, and mating season x ewe age were generally significant, whereas interactions of sire breed, mating season, and ewe age x dam breed were seldom detected. Interactions of sire breed x mating season were often due to changes in rank as well as magnitude, indicating the importance of matching sire breed to a specific mating season. The number born to Dorset-, Texel-, and Montadale-sired ewes was not affected by dam breed; however, Finnsheep-sired ewes out of northwestern whiteface dams were more prolific than Finnsheep-sired ewes out of Composite III dams, and the opposite situation existed for Romanov-sired ewes. Least squares means of sire breeds (P < 0.001) for total productivity of dam-reared lambs were 98.5, 103.5, 106.9, 124.6, and 154.9 kg/ewe entering the breeding flock for Texel, Dorset, Montadale, Finnsheep, and Romanov, respectively. Superior reproduction of Romanov-sired ewes was due to greater conception rate and prolificacy for each mating season and ewe age, as well as greater ewe longevity. Total productivity of F1 ewes by Composite III dams (125.6 kg) was greater (P < 0.001) than for ewes born to northwestern whiteface dams (109.7 kg), and the effect of mating season increased (P < 0.001) from August to October to December. Litter weight at 20 wk of age of 2- and 3-yr-old ewes was similar but greater (P < 0.001) than for 1-yr-old ewes. Experimental results provide comprehensive information about the appropriate use of these breeds in crossbreeding systems to meet specific production-marketing objectives.     

Effects of sarcoptic mange on the reproductive performance of ewes and transmission of Sarcoptes scabiei to newborn lambs

In each of two experiments, the reproductive performance of ewes naturally infested with sarcoptic mange and of uninfested ewes was assessed in in-season natural breeding conditions (experiment I) or in out-of-season controlled breeding conditions (experiment II). A statistically significant difference was observed in the total lambs born per ewe (infested ewes, 1.2; controls, 1.6), in the liveborn lambs per ewe (infested ewes, 1.2; controls, 1.5) and in the lamb body weight per ewe (infested ewes, 3.33kg; controls, 4.53kg) under natural breeding conditions, as well as in the lamb body weight per ewe (infested ewes, 3.37kg; controls, 4.14kg) among ewes under controlled breeding conditions. No adverse effects were observed in the other reproductive indices, cycling rate, mating rate, return-to-oestrus rate, abortion rate, lambing rate and stillbirth rate. Sarcoptic mange was observed in the offspring of infested ewes after 30 days and in the offspring of uninfested controls 60 days after their birth.     

影响南非肉用美利奴羊生长性状的非遗传因素

根据山西省沁水示范牧场2005—2008年度出生的183只羔羊的0-12月龄的生长记录,采用SPSS 17.0软件分析了羔羊出生年份、出生月份、出生类型、母亲年龄、哺育类型和性别等非遗传因素对南非肉用美利奴羊生长性状的影响。结果表明：①出生年份和母亲年龄对初生重的影响极显著（P〈0.01）;②出生年份、出生月份和性别对断奶重的影响极显著（P〈0.01）;③出生年份和性别对周岁重的影响极显著（P〈0.01）;④出生类型和性别对初生重的影响显著（P〈0.05）;⑤其余各因素对体重影响均不显著（P〉0.05）。这些结果可为今后估计南非肉用美利奴羊遗传参数和育种值时固定效应的划分提供科学依据,为该品种早期选种奠定基础。     

Non-genetic factors affecting reproductive traits in Lohi sheep

Abstract

The data on breeding and performance records (3830) of 1134 Lohi ewes kept at an Institutional Livestock Experiment Station, Okara in Punjab province during the period from 1972 through 2001 were used to study the influence of some non-genetic factors such as year and season of birth/lambing, age and weight at first service sex of lamb born, birth type, age of dam on various reproductive traits. The age of ewes at first service averaged 615.6±8.2 days and was not significantly affected by the year and season of birth of the ewes. The ewes born during spring season had comparatively low (613.6±7.9 days) age at first service than autumn born (617.5±9.8 days). The type of birth did not significantly influence age at first service. The least squares mean for the weight at first service was 42.10±0.24 kg and was significantly (P<0.01) influenced by the ewe's year and season of birth. The spring-born ewes were heavier (42.3±0.3 kg) at first service than autumn-born ewes (41.9±0.3 kg). The weight at first service was also significantly affected by the age at first service. The type of birth did not significantly influence weight at first service. The number of services per conception averaged 1.29±0.03 and varied significantly (P<0.01) between seasons. The number of services per conception was higher (1.37±0.02) in ewes bred during autumn than those bred in spring (1.16±0.06). The effects of years and weight at service on the number of services per conception were non-significant. The number of services per conception significantly increased with advancing age. Mean gestation period was 152.31±0.08 days and it was significantly affected by the years and seasons of lambing and the age of the ewe at lambing. However, gestation length was not significantly affected due to birth type and sex of the lamb born.     

不同杂交组合后代羔羊的生长发育和屠宰性能比较

为了研究杜泊羊和德国肉用美利奴羊与乌珠穆沁羊杂交产生的杂交后代的生产性能,在相同饲养环境下,试验分别选择同年龄的杜泊公羊、德国肉用美奴公羊与乌珠穆沁母羊杂交,对杜×乌组合、德×乌组合与乌×乌组合的后代(F1)羔羊的生长发育和屠宰性能进行了比较研究。结果表明,杜×乌组合、德×乌组合F1代羔羊的初生体重、1月龄体重、3月龄体重和6月龄体重均显著高于乌×乌组合的后代(F1)羔羊同月龄体重(P<0.05);杜×乌组合F1代羔羊的初生重、1月龄体重、3月龄体重均显著高于德×乌组合,但6月龄体重两组合差异不显著。屠宰性能结果表明,杜×乌组合、德×乌组合F1代羔羊在宰前活重、胴体重和净肉重均显著高于乌×乌组合(P<0.05);胴体率和净肉率各组间差异不显著。由该试验可以得出,杜泊公羊和德国肉用美利奴公羊与乌珠穆沁母羊杂交产生的杂交后代均表现出良好的杂种优势,二者均可作为优秀的良种公畜杂交改良内蒙古锡林郭勒盟当地羊,以提高杂交羊的产肉量,增加农牧民收入,助力当地畜牧业高质量发展。     

Influence of body weight, age, and weight gain on fertility and prolificacy in four breeds of ewe lambs

Breeding ewes to lamb at 1 yr of age can improve profitability for some production systems. The first objective of this study was to evaluate the effect of age and weight at breeding and total postweaning weight gain on reproductive performance of ewe lambs. The second objective was to compare the effects of weight and age variables in four major sheep breeds (Columbia, Polypay, Rambouillet, and Targhee). Weights, ages, and the binary traits of fertility (pregnant or nonpregnant) and prolificacy (one lamb born vs. two or more) were collected on 2,055 ewe lambs at the U.S. Sheep Experiment Station, Dubois, ID, from 1984 through 1988. The effects of age and weight at breeding and total weight gain from weaning to breeding on fertility and prolificacy were analyzed with a logit model in a maximum likelihood analyses. Differences (P < 0.001) among breeds for fertility were identified, with a 93% fertility rate for Polypay ewe lambs compared with lower fertility rates in Columbia, Targhee, and Rambouillet ewe lambs (50, 60, and 75%, respectively). The percentage of multiple births (prolificacy rate) also was higher (P < 0.001) in the Polypay (47%) than in Columbia, Targhee, and Rambouillet breeds (1, 13, and 14%, respectively). Averaged across breeds, weight at breeding had a positive effect on fertility and prolificacy (P < 0.001), whereas total weight gain from weaning to breeding had a positive effect only on fertility (P < 0.027). In separate analyses for each breed, increasing age (P < 0.001) and weight at breeding (P < 0.001) increased the probability of pregnancy in Rambouillet ewe lambs. The probability of pregnancy for Targhee ewe lambs increased (P < 0.005) with weight at breeding. Increasing weight at breeding increased (P < 0.004) the probability of multiple births in all breeds. Increasing total postweaning weight gain increased (P < 0.007) the probabilities of multiple births in Rambouillet and Targhee ewe lambs. In conclusion, Polypay ewe lambs were superior in fertility and prolificacy to Columbia, Rambouillet, and Targhee under Western range conditions. Improved reproductive performance of Columbia, Rambouillet, and Targhee ewe lambs may be achieved by increasing age and weight at breeding and postweaning gain.     

对妊娠后期甘肃高山细毛羊补饲秸秆全价颗粒饲料效果的研究

试验采用放牧+补饲的方式,分别利用玉米秸秆和小麦秸秆全价颗粒饲料在冷季对妊娠后期甘肃高山细毛羊进行补饲,测定妊娠后期母羊体重、血清生化指标、瘤胃液发酵参数及羔羊初生重。试验选取体况相近且健康的妊娠后期母羊60只,随机分为3组,每组20只。试验组补饲营养量根据中国美利奴羊妊娠后期母羊的饲养标准确定（扣除放牧采食量）,试验组Ⅰ补饲小麦秸秆全价颗粒饲料（1.19 kg/（只·d））,试验组Ⅱ补饲玉米秸秆全价颗粒饲料（1.19 kg/（只·d））,对照组按牧民传统方式（玉米0.05 kg/（只·d）、燕麦草0.2 kg/（只·d））补饲,正试期60 d。结果表明,试验组妊娠母羊的平均日增重、羔羊初生重均显著高于对照组（P<0.05）,而两试验组间无显著差异（P>0.05）;试验组妊娠母羊血液总蛋白、白蛋白、葡萄糖、总胆固醇浓度及谷草转氨酶、谷丙转氨酶和乳酸脱氢酶活性均显著高于对照组（P<0.05）;试验组妊娠母羊瘤胃液中总氮、蛋白氮、挥发性脂肪酸浓度和丙酸摩尔比均显著高于对照组（P<0.05）,而乙酸摩尔比显著低于对照组（P<0.05）。综上所述,补饲小麦秸秆或玉米秸秆全价颗粒饲料均可改善妊娠后期甘肃高山细毛羊营养状况,促进羔羊的生长发育。