Resistance to nematode parasites in Merino sheep: Correlation with production traits

Merino sheep representing a range of bloodlines in resource flocks located across Australia were tested for resistance to gastro-intestinal nematodes. These flocks included the JB Pye Flock (Camden, NSW), Katanning Base Flock (Katanning, WA), Turretfield Merino Resource Flock (Rosedale, SA), and the CSIRO Finewool Flock (Armidale, NSW) and included a total of 328 sire groups. Resistance to nematodes was measured by faecal egg count (FEC). Data were also available for greasy and clean fleece weight (GFW and CFW, respectively), fibre diameter (FD), and body weight (BW) at a range of ages from weaning to 21 months. Variance components were estimated by restricted maximum likelihood, fitting an animal model and estimating covariances in a series of bivariate analyses. Phenotypic correlations between FEC0·33 and production traits were all close to zero ( –0·09–0·02). Genetic correlations between FEC0·33 and production traits were –0·20, –0·18, and –0·26 for weaning weight, 10-month BW, and 16-month BW, respectively; 0·21, –0·06, and 0·21 for 10-month GFW, 16-month GFW, and 21-month GFW; 0·21, –0·05, and 0·07 for 10-month CFW, 16-month CFW, and 21-month CFW; and –0·09, –0·12, and 0·04 for 10-month FD, 16-month FD, and 21-month FD. When estimates were pooled for all fleece traits and all BW traits, the genetic correlations between FEC0·33 and GFW, CFW, FD, and BW were 0·15, 0·10, –0·06, and –0·21, respectively. Using pooled estimates for CFW, FD, and BW, selection for a breeding objective based on production traits alone would lead to an unfavourable correlated response in FEC0·33 of approximately 1% per year

The effect of the liver fluke Fasciola gigantica infestation on the leucocyte eosinophil cell profile on sheep

Eosinophil is one of the major leucocyte cell in the blood which specifically reacted on parasite infection, thus it is important to determine its profile against the F. gigantica infection. The aims of this study is to determine the differences of the eosinophil count profiles on the different breed of sheep infected with F. gigantica and its relation with the resistance of sheep bred against parasitic disease. Four groups of sheep consist of Indonesian Thin Tail (ITT) sheep, Merino sheep, backcross sheep (10 families) and F2 sheep were infected with 300 metacercariae of Fasciola gigantica. The total sheep used in this trial is 621. Those sheep were observed for 12 weeks and the blood samples were collected every 2 weeks after infection. The results showed that total eosinophil counts in all infected sheep increased after two weeks post infection and ITT sheep showed the highest counts. On the other hand, the mean fluke counts on ITT sheep is the lowest compared with the other groups of sheep. Merino and F2 sheep had the highest mean fluke counts. Three families of backcross sheep had the mean flukes count similar to ITT sheep and the other 7 families were similar to the Merino sheep. In conclusion, the highest total eosinophil count at the early stage of infection on ITT sheep might be related with the genetic resistance, which was showed by the lowest flukes count, and the resistance was inherited to some of the backcross sheep, which had similar flukes count with ITT sheep.   Key words: Fasciola gigantica, eosinophil, shee

Cylindrical, periodic surface lattice — theory, dispersion analysis, and experiment

A two-dimensional surface lattice of cylindrical topology obtained via perturbing the inner surface of a cylinder is considered. Periodic perturbations of the surface lead to observation of high-impedance, dielectric-like media and resonant coupling of surface and non-propagating volume fields. This allows synthesis of tailored-for-purpose "coating" material with dispersion suitable, for instance, to mediate a Cherenkov type interaction. An analytical model of the lattice is discussed and coupled-wave equations are derived. Variations of the lattice dispersive properties with variation of parameters are shown, illustrating the tailoring of the structure's electromagnetic properties. Experimental results are presented showing agreement with the theoretical model

The responses of eosinophil and packed cell volume (PCV) on sheep infected with Fasciola gigantica

The responses of eosinophil and packed cell volume (PCV) values were verified in infected sheep, in order to identify whether these parameters could be used to predict the flukes burden and their correlation with breed resistance. Fifteen Indonesian thin tail sheep (ET), 9 Merino sheep and 148 backcross sheep generated from mating of Merino sheep and F1 sheep (Merino X ET cross) were infected with 300 metacercariae of Fasciola gigantica. The blood samples were collected every 2 weeks by using EDTA venoject tubes in order to determine the amount of eosinophils and the PCV value. After 14 weeks of infection all of sheep were killed and the liver was collected in order to determine the number of flukes. The results showed that the amount of eosinophils increased 2 weeks after infection and reached the peak at week 4 after infection. The average of eosinophils in ET appeared higher than the other 2 breeds (Merino was the lowest and the backcross was in between). The correlation between the number of flukes recovered from the liver and the eosinophil counts were positive in ET and Merino, but negative in the backcross sheep. The PCV values remained constant along the trial, except at week 14 after infection; the PCV values were slightly decreased in backcross sheep and Merino sheep, but not in ET sheep. The correlation between number of flukes in the liver and the PCV values were negative in all breeds of sheep. These results suggested that the eosinophilic and PCV’s response of ET were higher compared to backcross and Merino sheep, thus that responses were thought to be associated with the resistant phenomenon.   Key words: Fasciolosis, eosinophil, PCV, shee

The next wave in selective breeding: implementing genomic selection in aquaculture

Advanced animal breeding in aquaculture has reached a tipping point where the commercial implementation of genomic selection to improve productivity and disease resistance is becoming reality. However, the success of practical implementation of genomic selection depends on the specific aquaculture species, production system and available phenotyping and genetic resources. Using the experience learned from commercial programs for pearl oysters and marine shrimp, we highlight current benefits and options in cost-effective high-throughput genotyping and phenotyping technologies for genomic selection applications relevant to aquaculture species, followed by discussion of some of the lessons learnt when dealing with its practical implementation, including what is needed to build adequate genotype resources for non-model species; confounded breeding objective verse trait measurements; complex traits and unknown interactions; multi-family breeding schemes; multi-stage selection schemes, and transition to a genomic selection breeding program incorporating minimisation of inbreeding

The effect of the liver fluke Fasciola gigantica infestation on the leucocyte eosinophil cell profile on sheep

Eosinophil is one of the major leucocyte cell in the blood which specifically reacted on parasite infection, thus it is important to determine its profile against the F. gigantica infection. The aims of this study is to determine the differences of the eosinophil count profiles on the different breed of sheep infected with F. gigantica and its relation with the resistance of sheep bred against parasitic disease. Four groups of sheep consist of Indonesian Thin Tail (ITT) sheep, Merino sheep, backcross sheep (10 families) and F2 sheep were infected with 300 metacercariae of Fasciola gigantica. The total sheep used in this trial is 621. Those sheep were observed for 12 weeks and the blood samples were collected every 2 weeks after infection. The results showed that total eosinophil counts in all infected sheep increased after two weeks post infection and ITT sheep showed the highest counts. On the other hand, the mean fluke counts on ITT sheep is the lowest compared with the other groups of sheep. Merino and F2 sheep had the highest mean fluke counts. Three families of backcross sheep had the mean flukes count similar to ITT sheep and the other 7 families were similar to the Merino sheep. In conclusion, the highest total eosinophil count at the early stage of infection on ITT sheep might be related with the genetic resistance, which was showed by the lowest flukes count, and the resistance was inherited to some of the backcross sheep, which had similar flukes count with ITT sheep