No abstract

Interspecies hybridization is of concern for the management of invasive species, as it can allow the exchange of advantageous alleles between introduced species and undermine control efforts. In this study, hybridization between populations of introduced common carp and goldfish in Australia is investigated. Common carp and goldfish were sampled extensively from the Murray-Darling Basin, the largest river basin in Australia. Fish identified in the field as hybrids, on the basis of having truncated or missing pairs of barbels around their mouths, were also sampled. All fish were genotyped for five microsatellite loci that could be amplified through polymerase chain reaction in both species, and the mitochondrial DNA control region was sequenced in the field-identified hybrids and a subset of the goldfish and common carp. Bayesian clustering analyses, factorial correspondence analysis and direct inspection of the microsatellite profiles confirmed that all fish identified as hybrids in the field had ancestry from both species. A number of cryptic hybrids were also identified. While most hybrids were inferred to be F1-generation, some F2-generation and backcrossed individuals were detected, indicating that gene flow is ongoing between carp and goldfish in Australia. Gene flow was biased in favor of male carp mating with female goldfish, as 19 of the 20 F1-generation hybrids had goldfish maternal ancestry. This ongoing gene flow could allow advantageous alleles (e.g. resistance to koi herpes virus) to move between species. This study illustrates that invasive species control programs should not only target the species considered most destructive, but should also consider the risks posed by introgression with related species. Animal Conservation. Print ISSN 1367-9430 Animal Conservation 15 (2012) 83-94

Summary. The association between bovine major histocompatibility system (BoLA) type and persistent lymphocytosis in cattle with antibodies to bovine leukaemia virus was examined by comparing antigen frequencies in cattle with persistent lymphocytosis to controls matched for age, sex, breed and presence of antibodies to BLV. The cattle came from nine dairy herds in south‐east Queensland, Australia; six herds were Australian Illawarra Shorthorn (AIS), two herds were Jersey and one herd was Friesian. Antigen W6 and Eu28R were more common in cattle with persistent lymphocytosis than in controls. Antigen W8 was less common in AIS cattle with persistent lymphocytosis. A study of 24 offspring from one sire, heterozygous for W10 and Eu28R, showed that offspring inheriting Eu28R from the sire were significantly more likely to have antibodies to BLV than offspring inheriting the opposing W10 haplotype.

The occurrence of the Leu127/Val127 variants of the bovine growth hormone (bGH) gene and their effect on milk production traits was investigated in Australian Holstein-Friesian cattle. Animals were genotyped for the Leu127/Val127 variants, with RFLP methodology, using PCR and AluI digestion of PCR products (AluI-RFLP). Alleles Leu127 and Val127 occurred with frequencies of 82% and 18%, respectively. The quantitative effect of this polymorphic site on milk-production traits was estimated from lactation data and test-day data. Results from the 2 data sets consistently showed that the Leu127 allele is associated with higher production of milk, fat, and protein and is dominant to Val127. The average effects of the gene substitution are 95 L for milk yield, 7 kg for fat yield, and 3 kg for protein yield per lactation. This locus may be directly responsible for quantitative variation or it may be a marker for a closely linked quantitative trait locus (QTL) for milk-production traits in Australian dairy cattle. In either case, it will be useful as an aid to selection for improvement of milk production traits. As the Leu127 allele is dominant, selection of AI sires homozygous for the Leu127 allele (Leu127/Leu127) will result in maximum benefit without the need for genotyping cows.

Mastitis is a multifactorial infectious disease, mainly caused by bacteria that infect the mammary gland. It is one of the major diseases in dairy ruminants, with respect to industry and public concern, economic impact, zoonotic potential and animal welfare. Genetic control of mastitis has been widely demonstrated. Accordingly, most countries have developed breeding programmes to improve udder health. Most evidence for host genetic variability, and its application for genetic improvement, is principally based on a few basic phenotypic traits related to healthy versus diseased status such as milk somatic cell counts (SCC) and clinical mastitis (CM) occurrence. Additionally, considerable progress has been made in the last decade to scrutinize immune mechanisms and genes that play key roles in the mammary gland defences. Accumulating QTL detection studies have allowed localization of regions of the genome that explain a large part of genetic variability for either SCS or CM traits on almost all autosomal chromosomes. However, resistance to mastitis is a highly complex trait, the genetically determined biological basis of which is mostly unknown. There is still an open field for development of additional relevant phenotypes that can be routinely collected. Further, additional studies are necessary to better understand the genetic basis of mastitis resistance, to predict long-term responses to selection and to develop new tools and strategies for genetic improvement of udder health.