Vaccination with an Insulin-like Growth Factor Binding Protein-1 (IGFBP-1)-bBased Vaccine Improves Growth in Feed-Restricted Brahman Steers

Dry-season weight loss in grazing cattle in northern Australia has been attenuated using a number of strategies (Hunter and Vercoe, 1987, Sillence et al. 1993, Gazzola and Hunter, 1999). Furthermore, the potential to improve efficiency of feed utilisation (and thus, dry-season performance) in ruminants through conventional modulation of the insulin-like growth factor (IGF) axis (Oddy and Owens, 1997, Hill et al., 1999) and through immunomodulation of the IGF axis (Hill et al., 1998a,b) has been demonstrated. The present study investigated the use of a vaccine directed against IGFBP-1 in Brahman steers which underwent a period of nutritional restriction followed by a return to wet-season grazing.

Limb-loss in pond-reared blue swimmer crabs Portunus pelagicus (L.): Effect on growth in an indoor shedding system

Limb-loss in crustaceans can reduce moult increment and delay or advance the timing of moulting, both aspects that are likely to impact upon soft-shell crab production. Pond-reared blue swimmer crabs Portunus pelagicus were harvested and maintained in a crab shedding system. The wet weight, carapace width (CW) and the occurrence of limb-loss were assessed before stocking in the shedding system and after each of the next three moults. Many of the crabs were initially missing one or two limbs and these did not grow as much as the crabs that were intact at the start of the trial. Despite its strong correlation with wet weight, CW changes proved to be misleading. Limb-loss reduced the %CW increment but not the per cent weight increment (where the later is calculated from the actual pre-moult weight). Pre-moult weight explained much of the variation in post-moult weight, with crabs moulting to approximately double their weight. Limb-loss reduced 'growth' and production from the pond because it reduced pre-moult weight but limb-loss did not alter the weight change on shedding a given weight of crabs, although some of that change now included regeneration of limbs. One can hypothesize that much of the size variation seen in pond-reared crabs may be due to accumulated effects of repeated limb-loss, rather than genetic variation.

Heritability estimates for growth in the tropical abalone Haliotis asinina using microsatellites to assign parentage

The tropical abalone Haliotis asinina is a wild-caught and cultured species throughout the Indo-Pacific as well as being an emerging model species for the study of haliotids. H. asinina has the fastest recorded natural growth rate of any abalone and reaches sexual maturity within one year. As such, it is a suitable abalone species for selective breeding for commercially important traits such as rapid growth. Estimating the amount of variation in size that is attributable to heritable genetic differences can assist the development of such a selective breeding program. Here we estimated heritability for growth-related traits at 12 months of age by creating a single cohort of 84 families in a full-factorial mating design consisting of 14 sires and 6 dams. Of 500 progeny sampled, 465 were successfully assigned to their parents based on shared alleles at 5 polymorphic microsatellite loci. Using an animal model, heritability estimates were 0.48 ± 0.15 for shell length, 0.38 ± 0.13 for shell width and 0.36 ± 0.13 for weight. Genetic correlations were > 0.98 between shell parameters and weight, indicating that breeding for weight gains could be successfully achieved by selecting for shell length.

Heritability of reproductive traits and genetic correlations with growth in the black tiger prawn Penaeus monodon reared in tanks

Captive-reared broodstock of the black tiger prawn (Penaeus monodon) have exhibited poor reproductive performance limiting attempts to domesticate this species. The potential for improved reproductive performance was assessed by determining heritabilities of four measures of reproductive performance, their genetic correlations with each other and with growth rate and weight at age. Heritability estimates (h2 ± S.E.) obtained from √ (days to spawn), √ (egg number), √ (nauplii number) and arcsin √ (proportion hatched) were 0.47 ± 0.15, 0.41 ± 0.18, 0.27 ± 0.16, and 0.18 ± 0.16, respectively. Estimates of genetic correlations between reproductive traits and weight at age, or growth rate were less than 0.5 except for √ (egg number) and weight at 54 weeks (0.93 ± 0.19) and √ (egg number) and 16-54-week growth (0.63 ± 0.29).

Phototropic growth in a reef flat acroporid branching coral species

Many terrestrial plants form complex morphological structures and will alter these growth patterns in response to light direction. Similarly reef building corals have high morphological variation across coral families, with many species also displaying phenotypic plasticity across environmental gradients. In particular, the colony geometry in branching corals is altered by the frequency, location and direction of branch initiation and growth. This study demonstrates that for the branching species Acropora pulchra, light plays a key role in axial polyp differentiation and therefore axial corallite development - the basis for new branch formation. A. pulchra branches exhibited a directional growth response, with axial corallites only developing when light was available, and towards the incident light. Field experimentation revealed that there was a light intensity threshold of 45 mu mol m(-2) s(-1), below which axial corallites would not develop and this response was blue light (408-508 nm) dependent. There was a twofold increase in axial corallite growth above this light intensity threshold and a fourfold increase in axial corallite growth under the blue light treatment. These features of coral branch growth are highly reminiscent of the initiation of phototropic branch growth in terrestrial plants, which is directed by the blue light component of sunlight.

A novel breeding programme for improved growth in barramundi Lates calcarifer (Bloch) using foundation stock from progeny-tested parents

Rapid genetic gains for growth in barramundi ( Lates calcarifer) appear achievable by starting a breeding programme using foundation stock from progeny tested broodstock. The potential gains of this novel breeding design were investigated using biologically feasible scenarios tested with computer simulation models. The design involves the production of a large number of full-sib families using artificial mating which are compared in common growout conditions. The estimated breeding values of their paternal parents are calculated using a binomial probit analysis to assess their suitability as foundation broodstock. The programme can theoretically yield faster rates of genetic gain compared to other breeding programmes for aquaculture species. Assuming a heritability of 0.25 for growth, foundation broodstock evaluated in two years had breeding values for faster growth ranging from 21% to 51% depending on the genetic diversity of stock under evaluation. As a comparison it will take between nine and twenty-two years to identify broodstock with similar breeding values in a contemporary barramundi breeding programme.

Pollination methods, stigma receptivity and pollen tube growth in Eucalyptus argophloia

Eucalyptus argophloia Blakely (Western white gum) has shown potential as a commercial forestry timber species in marginal environments of north-eastern Australia. We measured early pollination success in Eucalyptus argophloia to compare pollination methods, determine the timing of stigma receptivity and compare fresh and stored pollen. Early pollination success was measured by counting pollen tubes in the style of E. argophloia 12 days after pollination. We compared the early pollination success of 1) Artificially Induced Protogyny (AIP), one-stop and three-stop methods of pollination; 2) flowers pollinated at 2 day intervals between 2 days before and 6 days after anthesis and 3) fresh pollen and pollen that had been stored for 9 months. Our results show significantly more pollen tubes from unpollinated AIP and AIP treatments than either the one-stop pollination or three-stop pollination treatments. This indicates that self-pollination occurs in the unpollinated AIP treatment. There was very little pollen tube growth in the one-stop method indicating that the three-stop method is the most suitable for this species. Stigma receptivity in E. argophloia commenced six days after anthesis and no pollen tube growth was observed prior to this. Fresh pollen resulted in pollen tube growth in the style whereas the stored pollen resulted in a total absence of pollen tube growth. We recommend that breeding programs incorporating E. argophloia as a female parent use the three-stop pollination method, and controlled pollination be carried out at least six days after anthesis using fresh pollen.

Analysis of sexually dimorphic growth in captive reared cobia (Rachycentron canadum) and the occurrence of intersex individuals

The growth of three cohorts of captive reared cobia, grown in a combination of flow-though and recirculating aquaculture systems, was progressively measured to determine the existence and extent of sexually dimorphic growth in cobia. Approximately 100 fish from each cohort were individually identified and regularly weighed until the average weight of the fish was approximately 5 kg. The sex of individuals was determined through gonadal observations at the conclusion of each trial and the gender fitted retrospectively to the growth data set. Intersex gonads were observed in the first two cohorts of cobia, with 16.9% incidence in cohort 1 and 6.8% in cohort 2. Cobia is considered a gonochoristic species. This was the first reported observation of intersex gonads in cobia and the first reported occurrence of intersex gonads from a gonochoristic fish species from Australian waters. Only one fish out of the 182 examined in the third cohort was identified as intersex. There was no sexually dimorphic growth in cobia when there was a relatively high incidence of the intersex anomaly, as seen in the first two cohorts of fish. In the relative absence of the intersex condition, female cobia was significantly larger than males from 2 kg onwards. The weight of female cobia was almost 30% more than that of males at 17 months of age when average weight of the cohort was 4.6 kg. It is likely that the first two cobia cohorts were exposed to endocrine disruption in some form, and the possible sources are discussed. Statement of relevance This study demonstrated that female cobia grow significantly faster than male fish and that investigations into monosex culture could lead to significant productivity gains for cobia aquaculture. It also demonstrated that cohorts containing intersex fish did not exhibit sexually dimorphic growth. It is likely that the reproductive anomaly is the result of disruption to the endocrine system.