A note on the use of inbreeding in progeny test schemes

SUMMARY: In this note some theoretical and simulated results are presented comparing the selection response in a progeny test scheme that utilizes inbred offspring for testing, with respect to a standard progeny test. The theory indicates a substantial increase in selection response, although the advantage decreases as the number of dams mated to a sire and the number of offspring per dam increases. The advantage is at a maximum when the variation of the trait is due to segregation of recessive alleles at low frequencies unfavourable to the direction of selection. Computer simulation confirmed the advantage of the method. ZUSAMMENFASSUNG: Verwendung von Inzuchttieren bei der Nachkommenschaftsprüfung Hier wurden theoretische und simulierte Selektionserfolge konventioneller Nachkommenschaftsprüfung mit Prüfung von Inzuchtnachkommen verglichen. Theoretisch zeigt sich ein erheblicher Vorteil der letzteren, wenn dieser auch mit steigende Zahl von Partnern und deren Nachkommen abnimmt und nach null tendiert. Der Vorteil der Nachkommenschaftsprüfung ingezüchteter Nachkommen ist am h?chsten, wenn seltene ungünstige rezessive Gene eine Rolle spielen. Rechner-Simulation best?tigt den Vorteil dieser Vorgangsweise.     

Genetic relationship, inbreeding and generation interval in registered Gir cattle in Brazil

SUMMARY: Two-hundred random pedigrees of cows and fifty of sires born in 1987 from the Gir herdbook of the Brazilian Association of Zebu Breeders were analized. The bull Chave de Ouro DGR no. 2851 was the most influential animal with a 7% direct relationship to the breed. Total average inbreeding was 3.62 and 3.25 for the female and male sample, respectively. The subdivision of total inbreeding into current and non-current components resulted in values of 1.62, 1.25, 2.00 and 2.00 for the female and male sample, respectively. Long-term inbreeding was the principal component of non-current inbreeding, with values of 1.52% and 1.26%, respectively. Inbreeding due to strain formation strain due formation was less important (0.48% and 0.74%, respectively). The average generation interval was 8.02 years. The breed appears not yet to be subdivided into strains but this process may be starting. The average generation interval for the pedigree population was very high. Culling of old bulls could decrease this interval. ZUSAMMENFASSUNG: Verwandtschaft, Inzucht und Generationsintervall bei Gir Herdbuchrindern in Brasilien 200 zuf?llige Stammb?ume von Kühen und 50 von 1987 geborenen Stieren wurden vom Gir Herdbuch des brasilianischen Zebu Zuchtverbandes genommen. Der Stier Chave de Ouro DGR Nr. 2851 war das einflu?reichste Tier mit einer 7%igen direkten Verwandtschaft zur Rasse. Der gesamte Inzuchtkoeffizient war 3.6 und 3.25% für die weibliche und m?nnliche Stichprobe. Die Unterteilung der gesamten Inzucht in laufende und nicht laufende Komponenten resultierte in Werten von 1.62, 1.25, 2.0, 2.0 für die weibliche und die m?nnliche Stichprobe. Langfristige Inzucht war die Hauptursache für Nicht-Rezente Inzucht mit Werten von 1.5 und 1.26. Inzucht aufgrund von Linienbildung war weniger wichtig (0.48% und 0.74%). Das durchschnittliche Generationsintervall war 8.02 Jahre. Die Rasse scheint noch nicht in Linien unterteilt zu sein, aber dieser Proze? k?nnte begonnen haben. Das durchschnittliche Generationsintervall ist mit 8.02 Jahren sehr hoch. Nichtverwendung alter Stiere k?nnte dieses Intervall verkürzen.     

Factors associated with past and potential future use of veterinarians by Ontario trout farmers

This study investigated whether certain variables were associated with Ontario trout farmers' use of the Fish Pathology Laboratory (FPL), Ontario Veterinary College, or their willingness to pay for private veterinary services. Sixty-two farmers, representing 91% of Ontario's 1990 farmed trout production, were personally interviewed. Logistic regression was used to compare the 26 farmers who had submitted fish to the FPL during the previous two years to those who had not. Submitters tended to have been fish farming for fewer years, and to produce more fish, use more workers, treat prophylactically less frequently, keep records of drug treatments, and not disinfect holding units (p<0.05). Most farmers stated they would occasionally hire a private veterinarian. Only 13 farmers anticipated hiring one more than once per year. Polychotomous regression showed that farmers who purchased, instead of hatched, their seed stock, kept records, treated therapeutically often, and used several workers would hire private veterinarians more frequently (p<0.05). Strategies are discussed by which the veterinary profession might better understand and meet the needs of the aquaculture industry.     

Heartworm in dogs in Canada in 1991

In late November 1991, 1883 clinics in Canada were sent a questionnaire to assess the status of Dirofilaria immitis in dogs in 1991 and there was a 60.0% response. There were 344,031 dogs tested for heart-worm (HW), 627 were found infected and the prevalence of HW infection was 0.18%. There were 417 dogs with HW in Ontario, 116 in Manitoba, 38 in Quebec, 53 in British Columbia, three in Alberta, and one in Nova Scotia. In British Columbia, all of the infected dogs but one were from the Okanagan valley which, as from 1991, is a new focus of infection in Canada. Most dogs with HW had not been on preventive medication in 1990, and the prevalence among dogs tested and unprotected was 0.59%. That prevalence was considerably higher in endemic areas. Companion dogs, over three years of age and maintained primarily outdoors in rural areas, were most frequently infected. One cat was diagnosed with D. immitis and 33 dogs had Dipetalonema reconditium.