Pure Crosses Research Articles

Sex-specific stress tolerance, proteolysis, and lifespan in the invertebrate Tigriopus californicus.

Because stress tolerance and longevity are mechanistically and phenotypically linked, the sex with higher acute stress tolerance might be expected to also live longer. On the other hand, the association between stress tolerance and lifespan may be complicated by tradeoffs between acute tolerance and long-term survival. Here we use the copepod Tigriopus californicus to test for sex differences in stress resistance, proteolytic activity and longevity. Unlike many model organisms, this species does not have sex chromosomes. However, substantial sex differences were still observed. Females were found to have superior tolerance to a range of acute stressors (high temperature, high salinity, low salinity, copper and bisphenol A (BPA)) across a variety of treatments including different populations, pure vs. hybrid crosses, and different shading environments. Upregulation of proteolytic capacity - one molecular mechanism for responding to acute stress - was also found to be sexually dimorphic. In the combined stress treatment of chronic copper exposure followed by acute heat exposure, proteolytic capacity was suppressed for males. Females, however, maintained a robust proteolytic stress response. While females consistently showed greater tolerance to short-term stress, lifespan was largely equivalent between the two sexes under both benign conditions and mild thermal stress. Our findings indicate that short-term stress tolerance does not predict long-term survival under relatively mild conditions.

Evaluation of Clonal Uniformity in Six Superior Cacao Clones Based on SSR Marker

<p><em>Propagation of cacao plants is generally carried out vegetatively. Therefore, plants that are clonally propagated should be genetically uniform. Genetic uniformity in cacao clones is also very important information for germplasm conservation and in obtaining pure parental crosses. Evaluation of genetic uniformity can be seen through analysis using SSR markers. This study aimed to determine the genetic uniformity in six cacao clones using SSR markers. This experiment was conducted at IIBCRI Integrated Laboratory in Sukabumi and Plant Molecular Biology Laboratory, IPB Bogor, from September 2015 to December 2016. Six cacao clones used (TSH 858, TSH 908, ICS 13, PA 300, GC 7 and UIT) are from Kalitelepak experimental station of PTPN XII, Genteng District, Banyuwangi, East Java. Ten samples were taken randomly to represent cacao clones. DNA amplification was carried out using 12 SSR markers. The result showed that 12 SSR markers generated 45 alleles with the number of alleles per locus was 3-4 alleles. The polymorphic information content (PIC) ranges from 0.37</em>–<em>0.67, which are identied as very informative molecular analysis </em><em>in identifying the genetical uniformity of the evaluated cacao population. Six SSR loci generated variant alleles within both the TSH 858 and UIT clones, indicating there are off-type plants in these two samples. Clonal uniformity were detected for samples of the GC 7, ICS 13, PA 300 and TSH 908 clones. On the other hand, 8.33% of evaluated samples within the TSH 858 and UIT clones were off-type plants.</em></p>

Mortality investigation of Mytilus edulis and Mytilus galloprovincialis in France: An experimental survey under laboratory conditions

In the context of mass mortality outbreaks affecting adult and juvenile mussels since 2014 in France, two investigations were conducted to study mussel mortality under laboratory conditions in 2015. The first investigated the horizontal transmission of a putative causal agent of the mortality among two stocks of wild Mytilus edulis and the potential genetic resistance of adults and their progenies. The second evaluated the resistance of pure and hybrid crosses of M. edulis and M. galloprovincialis at the spat stage to a mortality outbreak. For the first time in France, we described several mortality outbreaks affecting spat and adult mussels under laboratory conditions. Mortality was observed for seawater temperatures ranging from 10 to 23 °C, although the significant mortality outbreaks occurred between 12 and 17 °C in adults and at 22 °C in spat. The disease screening revealed that no notifiable pathogen agent, as defined by OIE, was detected in the analyzed moribund mussels. Although bacteria belonging to the Splendidus clade were detected at high prevalence, with the exception of a mortality outbreak occurring in August, their role could not be defined in this study. Survivors of a mortality event occurring in the field in 2014 (Yves stock) still exhibited around 30% of mortality in 2015 under laboratory conditions, which indicated that they were either not fully resistant or that susceptibility varies with mussel age/size. This finding also suggests that a part of the survivors (or all) were carriers of a putative causal agent of the mortality. We demonstrated the horizontal transmission of a putative causal agent from the Yves stock to another stock of wild adult mussels (stock Agnas) which experienced 46% of mortality. In contrast, the Agnas stock had low mortality (5%) in the separate condition. Horizontal transmission of a putative causal agent from the wild adults to their hatchery-produced progenies was also observed. The progenies of the Yves stock, which survived a mortality outbreak in 2014, had lower mortality (27%) than those of the unselected Agnas stock (68%). Similarly, low mortality (<20%) were reported at the spat stage for a second stock of M. edulis produced from survivors of a mortality outbreak as well as for M. galloprovincialis, whereas their interspecific hybrids had mortality around 30%. These results could suggest that selective breeding programs in M. edulis, or the cultivation of M. galloprovincialis rather than M. edulis, could both reduce the impact of mortality outbreaks on mussel aquaculture. Nevertheless, further investigations are required to address the genetic basis of the survival in the two main mussels species cultivated in France.

Estimación de heterosis individual en cuyes (Cavia porcellus) F1 cruces de los genotipos Peru, Inti y Andina

El estudio se realizó en la E.E.A. Canaán del INIA (Ayacucho, Perú) con el objetivo de estimar la heterosis individual en cuyes F1 de cruces entre los genotipos Perú, Andina e Inti para las características de peso al beneficio, velocidad de crecimiento, rendimiento de carcasa, grasa de deposición y conversión alimenticia. Se obtuvo información de 115 descendientes entre puros y cruces de los genotipos Perú x Andina, Andina x Perú y Perú x Inti, siendo criados como grupos contemporáneo durante la fase de recría. La incidencia de los efectos fijos de tamaño de camada, sexo de la cría y número de parto de la madre sobre las variables en estudio fue analizada a través de un modelo de efectos, estimándose factores de corrección por mínimos cuadrados para aquellos efectos fijos que tuvieron incidencia significativa (p&lt;0.05). La heterosis fue estimada como el desvío del promedio del cruzamiento recíproco frente al promedio de los parentales puros. No se encontró heterosis significativa en los cruces y para las variables evaluadas. El cruce Perú x Inti (genotipo Perú como vía paterna) y el cruce recíproco Perú x Andina presentaron valores ínfimos de heterosis de 11.90 g (1.5%) y 10.25 g (1.3%) para el carácter peso al beneficio, respectivamente; en tanto que la velocidad de crecimiento se tuvo una heterosis de 0.39 g/día (3.9%) para Perú x Inti (genotipo Perú como vía paterna). Se concluye que el cruzamiento entre cuyes mejorados no produce niveles significativos de heterosis a nivel de los caracteres relacionados con la producción de carne.

Morphological characterization of the progenies of pure and reciprocal crosses of Pangasianodon hypophthalmus (Sauvage, 1878) and Clarias gariepinus (Burchell, 1822)

Twenty-five traditional and thirty-four geometric morphometric comparisons were carried out on pure and reciprocal crosses of Pangasianodon hypophthalmus (Sauvage, 1878) and Clarias gariepinus (Burchell, 1822). Thirty fish samples each of the C. gariepinus (CH), P. hypophthalmus (PH), Pangapinus (♀PH × ♂CG) and the two distinct morphotypes of the Clariothalmus (♀CG × ♂PH) (Clarias-like and Panga-like) between the ages of four and six months were used for this study. Phenotypically, the Clarias-like Clariothalmus and the Pangapinus progenies were indistinguishable from their maternal parents while the Panga-like Clariothalmus was a phenotypic intermediary of the putative parents but looks more closely to the paternal parent. Hence, both univariate proportion and multivariate analysis of the collected data successfully separated the different fishes into three multivariate spaces. The analysis of the dendrogram with complete linkage and Euclidean distance further showed the close relationship of the isolated Panga-like Clariothalmus progenies to the paternal parent, however, Clarias-like Clariothalmus and the Pangapinus were completely intermingled with their maternal parents. The most important index of discrimination of these fishes into different multivariate spaces was the fin characteristic which showed 100% exclusive ranges for the individual groups in many cases.

Water quality tolerance and gill morphohistology of pure and reciprocal crosses of Pangasianodon hypophthalmus and Clarias gariepinus

Tolerance to degrading water qualities in relation to the gill morphohistology was investigated in pure and reciprocal crosses of two important catfishes. Progenies of Clarias gariepinus (CG), Pangasianodon hypophthalmus (PH), Pangapinus (♀PH×♂CG) and the two observed morphotypes (Clarias-like and Panga-like) of Clariothalmus (♀CG×♂PH) were obtained from the same breeding history. These fishes were cultured in a static system without aeration and at high stocking density for a maximum period of two weeks. Mortality and water quality were monitored daily. Total mortality was observed 24 h post exposure (1DPE) in the Panga-like Clariothalmus, while the Pangapinus and pure P. hypophthalmus did not survive beyond the third day (3DPE). However, total mortality was not recorded in the Pure C. gariepinus and Clarias-like Clariothalmus even after 14DPE. Morphohistology of the gills of the latter fishes showed the presence of an accessory breeding organ in the form of branched bulbous dendritic-like structures and less occurrence/severity of many histopathological conditions observed during the challenge experiment. However, this was not the case with the other fish groups. It was concluded that the architecture and the level of susceptibility of the gill influenced the tolerance ability of the different fishes to poor water quality.

Effects of acidic pH on wild, farmed, and F1 hybrid Atlantic salmon (Salmo salar) parr

Farmed escapees have the potential to introduce novel genes to wild salmon and alter locally adapted populations. We tested whether the acidic conditions found in rivers on Newfoundland’s south coast might differentially impact offspring of farmed Atlantic salmon (Salmo salar) in comparison to wild populations. We performed crosses with wild and farmed parents to obtain wild (W♂ × W♀), farmed (F♂ × F♀), and F1 hybrid (W♂ × F♀, F♂ × W♀) parr and conducted a common garden experiment at neutral or acidic pH. No differences were observed between pure wild crosses and F1 hybrids, suggesting that acidic waters do not differentially affect survival, growth, condition factor, and Na+/K+-ATPase activity of F1 hybrids. Trends in mortality show that pure farmed parr had lower survival than pure wild and F1 hybrids in low pH. Considering that production of F1 hybrids rather than pure farmed offspring is the most likely outcome in the wild, pure farmed parr survival may have little bearing on the prediction of genetic risks of farmed–wild interactions. There is no evidence to indicate that the survival of the F1 generation in acidic waters acts as a potential barrier against introgression.

Hematological parameters of pure and reciprocal crosses of Pangasianodon hypophthalmus (Sauvage, 1878) and Clarias gariepinus (Burchell, 1822)

Comparative study on the hematological parameters of pure and reciprocal crosses of the African and Asian catfish was done to establish a reference range for fingerlings of the novel fish. Blood was collected from Clarias gariepinus (CG), Pangasianodon hypophthalmus (PH), Pangapinus (♀PH × ♂CG), and the two observed morphotypes (Clarias-like and Panga-like) of Clariothalmus (♀CG × ♂PH) obtained from similar breeding history. Result obtained revealed that red blood cell counts and white blood cell counts were significantly lower in Panga-like Clariothalmus (1.08 × 106/mm3 and 6.99 × 103/mm3, respectively) compare to other groups with similar higher counts (between 2.09 × 106/mm3 and 2.65 × 106/mm3; 13.60 × 103/mm3 and 17.27 × 103/mm3, respectively). However, Pangapinus and pure P. hypophthalmus had significantly higher values of packed cell volume (33.10 and 32.50%, respectively) and hemoglobin content (12.63 and 11.72 g/dL, respectively); similar values were recorded in those fish with Clarias maternal origin (between 25.00–27.80% and 6.67–8.03 g/dL, respectively for PCV and Hb). Calculated values for mean corpuscular volume was higher in Panga-like Clariothalmus (198.8 fL and 80.26 pg, respectively) while mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration values were higher in the Pangapinus and pure P. hypophthalmus (between 48.10–56.98 pg and 38.28–35.96 g/dL, respectively). This result obtained is suggestive that the Panga-like Clariothalmus may have reduced fitness as compared to the other progenies. The baseline values established in this study could serve as a standard for physiological, pathological, and toxicological references in future studies.

Erythrocyte characteristics of the progenies of pure and reciprocal crosses of Pangasianodon hypophthalmus (Sauvage, 1878) and Clarias gariepinus (Burchell, 1822)

In this study, erythrocyte characteristic of pure and reciprocal crosses of African catfish Clarias gariepinus (Burchell, 1822) and Asian catfish Pangasianodon hypophthalmus (Sauvage, 1878) were evaluated. Blood smear was made from the progenies of C. gariepinus (CG), P. hypophthalmus (PH), Pangapinus (♀PH × ♂CG) and in two morphotypes (Clarias-like and Panga-like) of Clariothalmus (♀CG × ♂PH) obtained from similar breeding history. Erythrocyte measurement of the cell and nuclear axis was done under the microscope, while many other parameters were calculated. Result obtained suggests a preponderant maternal influence on the erythrocytes shape and size characteristics of the reciprocal crosses. Erythrocytes from progenies with C. gariepinus maternal origin was rounded in shape (not less than 90%) while those with P. hypophthalmus maternal origin had relatively high oval shaped erythrocytes (between 76 and 64%). Also, significant size variations were recorded for the different group. Principal component analysis and biplot of component loading of the trio comparison of hybrid progenies and the pure crosses suggest the possibility of discriminating the direction of hybridization of the reciprocal crosses. However, it was impossible to describe the hybridization status of the progenies assessed in this study. This approach may be a simple and viable alternative to molecular markers which characterizes maternal inheritance in hybrid crosses provided that there is significant shape difference between the fishes. Erythrocyte characterization coupled with morphological and cytogenetic studies is recommended for clearer understanding of the nature of hybrid progenies.

No reduction of hatching rates among F1 hybrids of naturally hybridizing three Far Eastern daces, genus Tribolodon (Cypriniformes, Cyprinidae)

Egg hatching rates of F1 hybrids among three fishes, Japanese dace Tribolodon hakonensis, Pacific redfin T. brandtii, and rosyface dace T. sachalinensis, were compared with pure crosses. They are highly divergent (diverged 10–20 million years ago) but naturally hybridizing. Although crosses involving female rosyface dace were not available, hatching success was high among all combinations of hybrids (76 ± 23%) and comparable to pure crosses (86 ± 8%), implying ecological or genetic isolation mechanisms maintaining each species in later life stages.

Physicochemical changes of semimembranosus muscle during the processing of dry-cured ham from Celta pig. Effect of crossbreeding with Duroc and Landrace genotypes

Physicochemical characteristics of dry-cured hams from three genetic types, Celta breed (C line), Celta × Duroc (C × D) and Celta × Landrace (C × L) were determined on the semimembranosus muscle during 551 days of aging. Hams were obtained from 60 pigs reared in extensive systems and finished with a commercial feeding. Physicochemical parameters (pH and water activity) and chemical composition, (moisture, intramuscular fat, ash, protein and total chlorides content), colour parameters (L*, a* and b*) and lipid oxidation (thiobarbituric acid reactive substances value) were studied during the whole process after salting, post-salting, drying and bodega stages. Hams from crosses were characterised by higher intramuscular fat (12.78% and 10.48% for C × D and C × L lines, respectively) and moisture (46.86% and 46.63% for C × D and C × L genotypes, respectively), contents respect to Celta pure line that showed values of 5.96% and 35.83% for intramuscular fat and water content, respectively. Concerning colour parameters, hams from Celta line had lower values for all colour traits. The influence of crossbreeding on most physicochemical parameters observed was mainly due to the differences in moisture and intramuscular fat between hams obtained from pure breed and crosses. As a general conclusion, the crossbreeding of Celta pig (especially with the Duroc line) allows to improve the quality of dry-cured hams.

Early life traits of farm and wild Atlantic salmon Salmo salar and first generation hybrids in the south coast of Newfoundland.

This study examined fertilization rates, survival and early life-trait differences of pure farm, wild and first generation (F1) hybrid origin embryos after crossing farm and wild Atlantic salmon Salmo salar. Results show that despite a trend towards higher in vitro fertilization success for wild females, differences in fertilization success in river water are not significantly different among crosses. In a hatchery environment, wild females' progeny (pure wild and hybrids with wild maternal parent) hatched 7-11 days earlier than pure farm crosses and hybrids with farm maternal parents. In addition, pure wild progeny had higher total lengths (LT ) at hatch than pure farm crosses and hybrids. Directions in trait differences need to be tested in a river environment, but results clearly show the maternal influence on early stages beyond egg-size differences. Differences in LT were no longer significant at 70 days post hatch (shortly after the onset of exogenous feeding) showing the need to investigate later developmental stages to better assess somatic growth disparities due to genetic differences. Higher mortality rates of the most likely hybrids (farm female × wild male hybrids) at egg and fry stages and their delayed hatch suggest that these F1 hybrids might be less likely to survive the early larval stages than wild stocks.

Induced spawning, survival and growth of an African catfish hybrid (female &lt;i&gt;Clarias gariepinus&lt;i&gt; and male &lt;i&gt;Clarias anguillaris&lt;/i&gt;) fingerlings relative to their parental species in the mount Cameroon region

Clarias is a good candidate for aquaculture in Cameroon because of its high economic value but getting hardy and fast growing Clarias seed have been a major problem to fish farmers, especially in the Mount Cameroon Region. The objectives of this work are: to present the results of the experiments where a new Clarias hybrid fry/fingerlings will be reared simultaneously with the fry/fingerlings produced from pure parental species crosses in order to provide a critical assessment of the growth performance and survival rate of the hybrid fingerlings relative to those of the both parental species. Interspecies hybrids were produced by artificial insemination of the African catfish, pure C. gariepinus females X pure C. anguillaris males. The results revealed that the growth performance of the hybrid fingerlings relative to both parental species was most rapid in the second month and a high survival rate of 85.5 % was recorded. The absolute density estimated (at 95 % confidence limits) showed that the hybrid fingerlings of two mature female pure C. gariepinus (1kg/fish) and one mature male C. anguillaris (1 kg/fish) was 10,471 ± 126 fingerlings. This result is the first recorded success in the survival and growth of African catfish hybrid fingerlings relative to their parental species in the Mount Cameroon Region.Key words: Performance, aquaculture, hardy, interspecies hybrids, environmental

The male handicap: male-biased mortality explains skewed sex ratios in brown trout embryos.

Juvenile sex ratios are often assumed to be equal for many species with genetic sex determination, but this has rarely been tested in fish embryos due to their small size and absence of sex-specific markers. We artificially crossed three populations of brown trout and used a recently developed genetic marker for sexing the offspring of both pure and hybrid crosses. Sex ratios (SR = proportion of males) varied widely one month after hatching ranging from 0.15 to 0.90 (mean = 0.39 ± 0.03). Families with high survival tended to produce balanced or male-biased sex ratios, but SR was significantly female-biased when survival was low, suggesting that males sustain higher mortality during development. No difference in SR was found between pure and hybrid families, but the existence of sire × dam interactions suggests that genetic incompatibility may play a role in determining sex ratios. Our findings have implications for animal breeding and conservation because skewed sex ratios will tend to reduce effective population size and bias selection estimates.

Embryogenesis and Early Growth of Pure Strains and Hybrids of Sharptooth Catfish Clarias gariepinus and Sampa Heterobranchus longifilis

AbstractThe embryonic development, early growth and survival of pure and reciprocal hybrid crosses of Sharptooth Catfish Clarias gariepinus and Sampa Heterobranchus longifilis were studied. The morula and blastula stages occurred 5 and 10 min earlier, respectively, in pure crosses (at 4 h, 10 min and 5 h after fertilization, respectively) than in hybrids. Timing of gastrulation in pure strain H. longifilis and the ♀ H. longifilis × ♂ C. gariepinus cross was earlier (9 h) than in pure strain C. gariepinus and ♀C. gariepinus × ♂ H. longifilis (9 h, 25 min), but similar timings were recorded during the somite stages (18 h). Hatching started at 23 h in H. longifilis, at 23 h, 10 min in C. gariepinus, and at 23 h, 15 min in the hybrids. Yolk absorption was complete in 4 d, but exogenous feeding began on the third day (72 h) when larvae weighed 0.7± 0.01 mg (mean ± SE). After 4 weeks of feeding ad libitum with shell‐free Artemia, pure crosses of both species grew better than the hybrids, and C. gariepinus recorded the highest weight (83.33 mg). The hybrids, however, showed significantly higher survival than did the pure strains.

Survival and growth of reciprocal crosses between two stocks of the Hong Kong oyster C rassostrea hongkongensis ( L am &amp; M orton, 2003) in southern China

The Hong Kong oyster, Crassostrea hongkongensis, is one of the most economically important and well-known oyster species in southern China. To explore the possibility of improving the performance of the Hong Kong oyster, complete diallel crosses between two oyster stocks, the Zhuhai stock (Z: fast growth line F4) and the Maowei Sea stock (M: resistant line F3), were conducted using pooled gametes. Three replicates, each consisting of two pure stocks (ZZ and MM) and two reciprocal crosses (ZM and MZ), were successfully generated. High fertilization rate and hatching level were observed among all the experimental groups, suggesting that there was no sperm–egg recognition barrier between geographic populations. Reciprocal crosses had higher survival rate compared to the pure stock crosses and the rate of survival increased with progeny growth. Growth heterosis became obvious both in larval and adult stages, and was primarily influenced by the egg origin and mating strategy at the larval stage. Also, the phenotypic traits of all progeny differed amongst the culture sites, suggesting a significant environmental effect. The Zhuhai site was more suitable for oyster aquaculture than the Maowei Sea site. Thus, our results demonstrated that crossbreeding between Zhuhai and Maowei Sea stocks of Hong Kong oyster to produce superior heterosis represents a promising means to improve the fishery yield of this species in southern China.

Short communication: Heterosis by environment and genotype by environment interactions for protein yield in Danish Jerseys

Crossing of lines or strains within and between breeds has been demonstrated to be beneficial for dairy cattle performance. However, even within breed, differences between strains may also give rise to heterosis. A key question is whether an interaction exists between heterosis and environment (H × E) that is independent of genotype by environment (G × E) interactions. In this study, H × E and G × E interactions were estimated in a population of approximately 300,000 Danish Jersey cows. The cows were a mixture of pure Danish Jerseys and crosses of US and Danish Jerseys. The phenotype studied was protein yield. A reaction norm model where the unknown environmental covariates are inferred simultaneously with the other parameters in the model was used to analyze the data. When H × E, but not G × E, was included in the model, heterosis was estimated to be 3.8% for the intermediate environmental level. However, when both H × E and G × E were included in the model, heterosis was estimated to be 4.1% for the intermediate environmental level. Furthermore, when only H × E was included in the model, the regression on the unknown environmental covariate was estimated to be 0.15, interpreted as meaning that an increase of average herd-year protein yield by 1kg of protein led to an increase in heterosis of 0.15kg above the average heterosis for a first-cross cow. When both H × E and G × E were included in the model, the regression on the unknown environmental covariate was not significantly different from zero, meaning that heterosis was similar in all environments investigated. The genetic correlation of protein yields for different environmental levels ranged from 0.72 to 0.93, which was significantly different from unity, indicating that G × E exist for protein yield.

Testing for intraspecific postzygotic isolation between cryptic lineages ofPseudacris crucifer

Phenotypically cryptic lineages appear common in nature, yet little is known about the mechanisms that initiate and/or maintain barriers to gene flow, or how secondary contact between them might influence evolutionary trajectories. The consequences of such contact between diverging lineages depend on hybrid fitness, highlighting the potential for postzygotic isolating barriers to play a role in the origins of biological species. Previous research shows that two cryptic, deeply diverged intraspecific mitochondrial lineages of a North American chorus frog, the spring peeper (Pseudacris crucifer), meet in secondary contact in Southwestern Ontario, Canada. Our study quantified hatching success, tadpole survival, size at metamorphosis, and development time for experimentally generated pure lineage and hybrid tadpoles. Results suggest that lineages differ in tadpole survival and that F1 hybrids may have equal fitness and higher than average mass at metamorphosis compared with pure parental crosses. These findings imply hybrid early life viability may not be the pivotal reproductive isolation barrier helping to maintain lineage boundaries. However, we observed instances of tadpole gigantism, failure to metamorphose, and bent tails in some tadpoles from hybrid families. We also speculate and provide some evidence that apparent advantages or similarities of hybrids compared with pure lineage tadpoles may disappear when tadpoles are raised with competitors of different genetic makeup. This pilot study implies that ecological context and consideration of extrinsic factors may be a key to revealing mechanisms causing negative hybrid fitness during early life stages, a provocative avenue for future investigations on barriers to gene flow among these intraspecific lineages.

Growth curve estimation in pure goat breeds and crosses of first and second generation in Tunisian oases

Five non-linear statistical models were tested to fit the growth curve parameters of the kids of indigenous, Alpine and Damascus goats and their crosses. Data from 16 years’ periodical weight study was used to adjust the growth curve of 1,687 suckling kids before they attained the age of five months. Among the tested models, the iterative procedure made it possible for the Gompertz model to be identified as the best for use to adjust kids’ growth evolution. Brody, Richards, Logistic and Polynomial models showed some convergence problems of accuracy. Curve parameters were fitted by Gompertz model after about 16 iterations with a coefficient of determination (CD) value of 71%. Growth parameters were established by genetic groups and the shape of the curve changed with kids’ genotypes. Crossbreeding allowed for a better growth kinetic in indigenous kids. After birth, kids’ weights increased rapidly to an asymptotic weight at an early age. The best growth performances were obtained in the first generation of crossbreeding due to heterosis. The growth curve adjustment helped in better flock management and in the fattening of kids according to the potentialities of each genotype. Key words: Goat, kids’ growth, curve model, Gompertz, crossbreeding, Tunisian oases.

Production of Heterotic Hybrid in Rohu (Labeo rohita) Through Strain Crossing

As a genetic means of aquaculture development, hybridization can increase production quickly in fishes because of heterotic effect. At the backdrop of reports on the decline of growth and reproduction of the hatchery population of Labeo rohita in Bangladesh, a 3 months study was undertaken to see the heterotic effect by intra-specific crossing among the Padma, Jamuna and Hatchery strains of rohu. Six reciprocal crosses and 3 pure crosses were obtained. The fertilization and hatching rates of the developing embryos were found better in the parental crosses than the reciprocal intra-specific hybrids. The growth performance of reciprocal crosses showed significant differences (P&lt; 0.05) over the parental crosses. The best growth performance was observed in Padma ? X Jamuna ? hybrids; providing 72% positive heterosis. Since the growth rate of strain crossed hybrids were reasonably high, this technique can be profitably applied for the production of fast growing seed to ensure higher fish production and more profit.DOI: http://dx.doi.org/10.3126/ijls.v5i1.5035 International Journal of Life Sciences Vol.5(1) 2011 32-38