不同杂交组合母羊繁殖性能的观察

随机选择波本、萨本、波萨本母羊各300只用波尔山羊公羊配种,观察其受胎率、妊娠期、产羔率等指标,以期了解各杂交组合母羊的繁殖性能,结果表明:这3个杂交系母羊在情期受胎率、妊娠期和产羔率上无显著差异(P<0.05雪,萨本母羊难产率高而波本母羊后代2月龄成活率较低,说明在生产实践中,推行波萨本杂交模式最为理想。     

山羊同期发情人工授精效果观察

利用三合激素(ITC)对山羊进行同期发情处理,0～96h同期发情率为93.9%,选出适宜配种的发情母羊立即肌注促排A3,采用波尔山羊种公羊鲜精(1∶20倍稀释)配种,对发情母羊进行人工输精,间隔8～12h再进行第2次输精,情期受胎率不到40%。     

波尔山羊批量胚胎移植

波尔山羊是一种著名的肉用山羊品种。为了提高波尔山羊繁殖效率,本试验采用激素处理经产母波尔山羊,超数排卵,经与纯种公波尔山羊配种,手术从输卵管中冲出发育至2～8细胞的胚胎,再经手术移回同步发情的受体山东奶山羊输卵管内,妊娠产仔。结果:(1)超排50头次波尔山羊(其中12头重复使用),获1179枚早期胚胎,其中2细胞以上的胚胎占84.8%(1000/1179);(2)移植480头受体;受体羊最终怀孕率56.25%(270/480),共产仔334头,其中产双胎的受体有64只,占妊娠羊数的23.7%(64/270);(3)羔羊出生重平均为(3.8±0.86)kg,最重达7.2kg。以上结果表明,每头次波尔山羊经过超数排卵、胚胎移植,平均可产6.68(344/50)头羔羊,若1年内1头波尔羊重复2次可获得13.4头羊羔,与常规育种相比极大地提高了纯种波尔山羊的繁殖速度。     

波尔山羊精液高倍稀释人工授精的受胎效果

公羊为江苏省丰县（梁寨镇）合作种羊场所饲养的3只种用波尔山羊，年龄2～3岁，体重90～110kg，射精量0.4～1．2mL，精液密度每毫升19．8亿～30．4亿。抗力系数13000～15500。精液活力0．7～0．9级。母羊为当地农民散养的自然发情后前来配种的羊只，品种为徐淮白山羊或波尔山羊杂交羊，年龄5月龄至7岁，胎次0～12胎。     

不同季节隆林山羊繁殖性能的调查情况

通过对广西扶绥肉用山羊种羊场2006—2007年686胎次隆林山羊母羊繁殖性状的按季度统计分析,以揭示母羊繁殖性能随季节的变化规律。结果发现,隆林山羊母羊受胎率随着季节的不同呈现出规律性的变化,以春季(3—5月)最高,平均受胎率为89.2%;最低是夏季(6—8月),为77.2%。断奶成活率以夏季(6—8月)最高,平均断奶成活率为96.9%;最低是冬季(12—次年2月),为80.4%。     

波尔山羊胚胎移植研究进展

自1995年我国开始引进波尔山羊(Boergoat)以来,因其体格大、生长快、屠宰率高,改良本地山羊杂交优势明显而倍受广大养羊户的青睐,价格居高不下,种羊供不应求,从而为波尔山羊的胚胎移植(embryotransfer,ET)提供了广阔的市场和巨大的空间。本文就近年来波尔山羊ET技术的研究进展介绍如下:1供、受体羊选择1.1供体羊选择进行ET的供体母羊应具有优良的遗传特性和较高的育种价值,生产性能、经济价值、育种价值高,健康无病,生殖系统机能正常,无难产和屡配不孕史,膘情适中。符合品种标准,年龄2.5～6岁为宜,青年羊至少1.5岁(18月龄)以上,经产羊应…     

波尔山羊在鄂西山区适应性饲养以及生产性能效果观察

观察结果表明：波尔山羊具有很强的适应性，抗寄生虫侵袭能力强，采食力强；生长发育良好，周岁公母羊口平均增重分别为134.3g和115.7g，羔羊日平均增重165g；受胎率、产仔率、繁殖成活率等生产性能接近或达到原产地水平；波尔山羊与宜昌白山羊杂交一代体重明显提高，改良效果显著。     

波尔山羊的超数排卵研究

在不同季节、应用不同FSH剂量对不同年龄、是否经产、不同体重以及不同利用次数的55头次波尔山羊进行超数排卵处理(其中10头波尔山羊为重复使用)。结果表明:在繁殖季节,应用FSH总剂量为200～300IU,年龄为2～5岁,经产的波尔山羊超排效果好。每头平均获卵20.75枚。重复超数排卵的波尔山羊也具有较好的超排效果:第一次平均获卵21.9枚,第二次平均获卵17.8枚。     

YL母猪繁殖性能的观察和测定

对从乐山种猪场和从仁寿县种猪场引近的300多头YL母猪进行繁殖性能观察，其适配日龄为8～10月龄，体重100kg左右，发情周期为18～23d，平均21d，发情持续期约为5d，妊娠期平均为114d，平均产仔率112％，仔猪平均初生重1．25kg，用杜洛克种公猪精液对YL母猪人工授精，情期受胎率高达92. 86％，用杜洛克种公猪对YL母猪进行自然交配，情期受胎率为83. 3％。     

利用外源性激素对波杂山羊同期发情处理效果的研究

试验以波杂山羊为试验对象,设计了3种不同的短期同期发情处理方法,对同期发情率、发情后卵巢状态观察及情期受胎率进行了统计分析与评价。结果表明:组2(CIDR+PG+PMSG,82%)和组3(PG+三合激素,80%)的同期发情率显著高于组1(PG+PMSG,66%)(p<0.05);组2处理后发情羊的卵巢状态明显优于其他2组;而且组2的情期受胎率也显著高于组1和组3(p<0.05)。综上,CIDR+PG+PMSG是波杂山羊最有效的短期同期发情处理方法。     

农区不同品种肉羊杂交组合模式效益分析

选择波尔山羊、南江黄羊、本地羊进行杂交组合,分析不同组合模式的产羔数、初生重、双月龄断奶重、六月龄出栏重等生产指标,筛选农区适度规模舍饲肉羊的最优杂交组合。结果表明:不同品种肉羊杂交生产性能明显提高;不同杂交组合模式效益依次为本♀×波♂×波♂>本♀×南♂×波♂>本♀×波♂。     

中华绒螯蟹一龄性早熟和二龄成熟家系子一代成蟹阶段生长发育育性能的比较研究

中华绒螯蟹(Eriocheir sinensis)存在一龄性早熟和二龄正常成熟两种现象,为了解其后代养殖性能是否存在差异,本研究利用构建的一龄早熟家系和二龄正常成熟家系,评估了其子一代在成蟹养殖阶段的生长、存活率、产量、生殖蜕壳和性腺发育,结果显示:(1)正常家系的子一代在8月和10月的平均体重(70.45±18.62)g,(95.87±34.44)g高于早熟家系的平均体重(58.93±16.33)g,(95.56±25.26)g,甲壳长和甲壳宽在7、8和10月份,正常家系显著高于早熟家系,4-10月二龄正常成熟家系的特定增重率(SGR,(1.48±0.45)%/d)低于一龄早熟((1.65±0.12))%/d;(2)一龄性早熟家系完成生殖蜕壳的时间早于二龄正常家系,一龄性早熟家系在8月份的生殖蜕壳率为85%,高于正常家系(75%),但两者的性腺指数和肝胰腺指数均无显著差异;(3)就最终养殖效果而言,尽管正常成熟家系子代的存活率和平均产量比早熟家系分别高出14%和17%,但两种家系间无显著差异。结果表明,河蟹二龄成熟家系子代在成蟹阶段的生长性能优于一龄早熟家系子代。     

Crosses between two subspecies of bay scallop Argopecten irradians and heterosis for yield traits at harvest

In order to improve the yield of bay scallop Argopecten irradians by exploiting geographic subspecies heterosis, crosses between and within two subspecies, the northern A. i. irradians (Lamarck) and the southern A. i. concentricus (Say), were created and the offspring were cultured under the same environmental conditions. The two parental populations were collected from Bohai Bay in northern China and Beibu Bay in southern China, which were distinct in particular shell colours. The results indicated that the shell colour of bay scallop was inheritable and could be used as a morphological mark to distinguish hybrid and purebred individuals. At harvest, hybrid offspring always produced a significantly higher yield than purebred offspring. Positive heterosis was achieved for shell length, shell height, shell width, total weight and adductor weight, which was 5.02, 5.22, 3.88, 7.53 and 9.47 respectively. Hybrid gain was 10.86% for shell length, 10.48% for shell height, 9.77% for shell width, 34.90% for total weight and 41.69% for adductor weight, respectively, and all were significantly >5%. The present study reveals that it is effective for improving yield by hybridization between different geographic subspecies in the bay scallop.     

Fertilization, hatching, survival and growth rates in reciprocal crosses of two strains of an African catfish Heterobranchus longifilis Valenciennes 1840 under controlled hatchery conditions

A diallelic cross between two strains [Layo strain (LS) and Noun strain (NS)] of the catfish Heterobranchus longifilis Valenciennes was carried out under controlled hatchery conditions to estimate their reproductive performance and aquaculture potential in terms of fertilizability, hatchability, survival, growth and heterosis. The average fertilization rate of all mating groups was as high as 90.4%, the fertilization rate of the purebred NS (95.2%) being significantly higher than that of the purebred LS or the reciprocal crosses (P < 0.05). The average hatching rate of all genetic groups was as high as 84.7%, the hatching rate of NS (89.4%) being significantly higher than that of the purebred LS or the reciprocal crosses (P < 0.05). The mean survival rate of all crosses from hatching up to the onset of exogenous feeding stood at 94.2%, without showing a significant difference (P > 0.05) between the crosses. During the larval rearing period, which extended from the onset of exogenous feeding up to 15 days of age, NS displayed a significantly lower growth rate (P < 0.001) than that of the purebred LS and their reciprocal hybrids. There was no significant difference (P > 0.05) in survival rate (mean 84.7%) between the four crosses at the end of the larval rearing period. During the juvenile rearing phase, the mean growth performance of all crossbreds was similar to that of the purebred LS and significantly different from that of the purebred NS (P < 0.001). The final individual weights attained by LS, NS, LS × NS and NS × LS were 3.31, 0.71, 3.97 and 3.66 g respectively. The increase in weight attained by the fast‐growing crossbred LS × NS was 562.2%, 20.4% and 8.7% more than that of NS, LS and NS × LS respectively. The survival rate of NS (57.1%) was significantly lower (P < 0.001) than that of all the rest of the crosses. The crossbreds displayed about 15.1% heterosis in mean body weight relative to the fast‐growing purebred LS. It was concluded that cross‐breeding of H. longifilis strains could be advantageous because of the hybrid vigour in the progeny.     

Fishery‐induced demographic changes in the timing of spawning: consequences for reproductive success*

Demography can have a significant effect on reproductive timing and the magnitude of such an effect can be comparable to environmentally induced variability. This effect arises because the individuals of many fish species spawn progressively earlier within a season and may produce more egg batches over a longer period as they get older, thus extending their lifetime spawning duration. Inter‐annual variation in spawning time is a critical factor in reproductive success because it affects the early environmental conditions experienced by progeny and the period they have to complete phases of development. By reducing the average lifetime spawning duration within a fish stock, fishing pressure could be increasing the variability in reproductive success and reducing long‐term stock reproductive potential. Empirical estimates of selection on birth date, from experiments and using otolith microstructure, demonstrate that there is considerable variation in selection on birth date both within a spawning season and between years. The few multi‐year studies that have linked egg production with the survival of progeny to the juvenile stage further highlight the uncertainty that adults face in timing their spawning to optimize offspring survival. The production of many small batches of eggs over a long period of time within a season and over a lifetime is therefore likely to decrease variance and increase mean progeny survival. Quantifying this effect of demography on variability in survival requires a focus on lifetime reproductive success rather than year specific relationships between recruitment and stock reproductive potential. Modelling approaches are suggested that can better quantify the likely impact of changing spawning times on year‐class strength and lifetime reproductive potential. The evidence presented strengthens the need to avoid fishing severely age truncated fish stocks.     

Growth Performance of All-Female and Mixed-Sex Common Carp Cyprinus Carpio L. Populations in the Central Europe Climatic Conditions

The results of a 4-yr study focused on comparing growth performance in all-female and mixed-sex populations of common carp are presented. All-female and mixed-sex populations of purebred Northern mirror carp (M72) and scaly crossbreds of female Ropsha (ROP) and male/neomale M72 carp (ROP × M72) were used for this experiment. Average weight and survival after each growing season and slaughtering value after the third and fourth year of the study were measured. While after 8 wk of rearing no differences between all-female and mixed-sex populations were found, the 1-yr-old all-female mirror carp population (M72) gained 29.7% more weight ( P < 0.0001) than the mixed-sex (68.5:± 15.8 g against 52.8:± 13.9 g; meant S.D.) population. After the second, third and fourth year of rearing, live weight was 9.5% ( P = 0.0062) and 6.8% ( P = 0.0229) and insignificantly 5.1 % higher, respectively, in the all-female population. There was no significant difference, even after the fourth growing season, in live weight between all-females and bisexual scaly crossbreds (2,192 g± 478.3 and 2,206 g± 484.5, respectively). The percentage of the main edible parts (processed body, filleting yield) was significantly higher in both mirror and scaly, all-female populations at 3 yr of age but not significantly different in 4-yr-old fish. No distinct differences in survival and body shape of all-female and bisexual populations were found. The potential of all-female populations for commercial production is discussed.     

Spawning‐related mortality in captive Atlantic cod (Gadus morhua L.)

Two year‐classes of Atlantic cod were reared in indoor tanks from November 2002 to November 2004. The average annual mortality was 21% and 36% for males and females respectively. The highest monthly mortality rates in females were observed around and during the spawning periods from March to July, maximally 7% and 20% for year‐class 2001 and 18% and 34% for year‐class 2000. The mortality in males was less dependent on season, reaching a maximum of 7% and 5% month^?1 for year‐class 2001 and 2000 respectively. The maximum mortality during spawning increased with age from: 7%, 19% and 34% per month for 2‐, 3‐ and 4‐year‐old females respectively. The average gonadosomatic indices in 3‐ and 4‐year‐old mature females that died during the spawning periods were 22% and 26% respectively and most of them were spawning when they died. The results suggest that egg‐retention may have been the main cause of death in females during spawning.     

Offspring Growth in a Diallel Crossbreeding with Three Strains of Nile Tilapia Oreochromis niloticus

Abstract— A complete diallel crossing of three strains, Stirling, Korean and Local, was used to evaluate heterosis of intraspecific crossbreeding on early growth of Nile tilapia Oreochromis niloticus . All possible F-1 hybrid offspring were obtained and their growth rates to 90 d were compared. The specific heterosis for F-1 hybrids in Stirling × Korean, Stirling × Local and Korean × Local crosses were 7.61, 5.63 and 7.70 for weight, and 0.47, 0.26 and 0.55 for length, respectively. The purebred Stirling strain showed better growth than the other two strains (P < 0.05). When growth of F-1 hybrids was compared between sexes, males grew more rapidly than females (P < 0.05). However, no differences were observed in growth of male or female between hybrid groups. Purebred males in the Stirling strain were slightly heavier than those in the Korean and Local strains, and Local × Stirling, Korean × Local and Local × Korean crosses. However, in purebred females Stirling was superior to Korean, but not the Local strain and all F-1 hybrid crosses. Implications to choose the appropriate strains for developing a breeding program of tilapia are also discussed.     

The prevalence of escaped farmed salmon, Salmo salar L., in the River Ewe, western Scotland, with notes on their ages, weights and spawning distribution

Abstract  The prevalence of escaped farmed Atlantic salmon, Salmo salar L., in the River Ewe, western Scotland, was assessed. After the establishment of smolt cages in the catchment and marine cages near the river mouth during 1986–1987, approximately 425 000 parr and smolts, and 122 000 growers have escaped. Between 1987 and 2001, farmed salmon occurred in the rod fishery in 13 of the 15 years, contributing at least 5.8% of the total catch, with a maximum annual frequency of 27.1%. It was estimated that <1% of fish escaping from the marine cages entered the river, but contributed at least 27% of potential anadromous spawners in 1997. Radiotagged, farmed fish in 2001 probably spawned in three subcatchments also used by tagged wild fish. Despite the likelihood of hybridisation there was no change in the median weight or marine age of wild fish, but smolt age decreased significantly ( P  < 0.02). The Ewe has a depleted wild salmon population (≤900 anadromous adults), and further genetic introgression by escapees should be prevented.     

Assessment of the heterosis of F1 hybrids of Misgurnus anguillicaudatus and Paramisgurnus dabryanus using microsatellite-based parentage assignment

Misgurnus anguillicaudatus and Paramisgurnus dabryanus hybrids were generated via full diallel crosses between the Meishan (M_M) and Fuyang (M_F) populations of M. anguillicaudatus and Meishan (P_M) and Ziyang (P_Z) populations of P. dabryanus. The purebred and hybrid offspring were co-cultured in a pool for 4 months, and 96.5% of the offspring could be assigned to a single parental pair based on nine potentially cross-species polymorphic microsatellites. The average body weight (BW) of the P_M × P_Z (female × male, in this order hereafter) hybrids was the highest (4.88 g), followed by that of the P_Z × P_M and P_M × P_M hybrids. The general combining abilities (GCA) of BW from both the sires and dams of P_M and P_Z were high, and that from M_M and M_F were low. The specific combining ability (SCA) of P_M × P_Z was the largest (16.61), followed by that of P_Z × P_M, M_F × M_M, and M_M × M_F (?15.89). The combination of M_F × P_M, M_F × P_Z, and P_M × M_F showed > 10% heterosis. This is the first study to use microsatellite-based parentage assignment in hybrid fish and lays foundation for loach crossbreeding.