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Titolo: MOET BREEDING SCHEMES FOR WOOL SHEEP .1. DESIGN ALTERNATIVES
Autore: WRAY NR; GODDARD ME;
 Indirizzi:
 VICTORIAN INST ANIM SCI,LIVESTOCK IMPROVEMENT UNIT,475 MICKLEHAM RD ATTWOOD VIC 3049 AUSTRALIA
 Titolo Testata:
 Animal Production
,
volume: 59,
anno: 1994,
parte:, 1
pagine: 71  86
 SICI:
 00033561(1994)59:<71:MBSFWS>2.0.ZU;2F
 Fonte:
 ISI
 Lingua:
 ENG
 Soggetto:
 EMBRYO TRANSFER; DAIRYCATTLE; MULTIPLE OVULATION; GENETIC CHANGE; SELECTION; RATES;
 Keywords:
 BEST LINEAR UNBIASED PREDICTION; INBREEDING; MOET; SELECTION; SHEEP; WOOL;
 Tipo documento:
 Article
 Natura:
 Periodico
 Settore Disciplinare:
 Science Citation Index Expanded
 Science Citation Index Expanded
 Citazioni:
 29
 Recensione:
 Indirizzi per estratti:



 Citazione:
 N.R. Wray e M.E. Goddard, "MOET BREEDING SCHEMES FOR WOOL SHEEP .1. DESIGN ALTERNATIVES", Animal Production, 59, 1994, pp. 7186
Abstract
Breeding schemes for wool sheep based on natural service (N), MOET (multiple ovulation and embryo transfer) in adults (A) and MOET in juveniles (J) are compared using Monte Carlo simulation allowing overlapping generations and selection across age groups. In all schemes parents can bea maximum of 6 years old when their offspring are born, and can be a minimum of 2 years in N or A schemes or 1 year in J schemes. Embryo transfer success rates follow realistic distributions (only 70% of flushes resulting in live lambs) with a mean of 2.13 or 3.45 6monthold lambs per donor per flush for current or 'future' situations. Undernatural mating an average of 1.09 6monthold lambs per ewe mated is assumed. The trait under selection has a heritability of 0.4 and is measurable on both sexes by 18 months of age, which is before selection in N and A schemes but after the initial opportunity for selection in J schemes where selection is based on a pedigree index. Two culling policies for males are considered in J schemes: all sires culled if not selected (J), or all sires available for selection after their record is collected even if they were not selected on their pedigree index inthe previous year (J(male)). Comparison of schemes is made on the basis of response depressed by the effect of inbreeding and cumulated anddiscounted over a medium time horizon. For a given population size (constant expected number of lambs per year and therefore numbers of dams dependent on fertility rates) different numbers of sires were utilized. The optimum number of sires was determined as the number which maximized the response criterion. N, A, J and J(male) schemes have different optimum numbers of sires (5, 8, 30 and 20 respectively) which occur at different rates of inbreeding and which are approximately independent of population size. Advantages in the response criterion of A, J and J(male) over N schemes are 23%, 33% and 47% respectively for 'future' embryo transfer success rates and mass selection. Increasing the number of lambs born per donor ewe from 2.13 to 13.8 (by increasing embryos per flush and number of flushes) increases the response criterionby up to 25% in A and up to 11% in J schemes (assuming donor ewes aremated to a different sire for each flush) with 345 lambs born per year. Use of best linear unbiased prediction (BLUP) estimated breeding values increases response by 8%, 3% and 3% in N, A and J schemes respectively. The advantages of J over A and N schemes, of increased lambs per donor and of BLUP over mass selection all increase as population size increases. Insemination of the poorer ewes with semen which gave only female offspring gave 5% increase in the N scheme and no benefit in A or J schemes.
ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 23/09/20 alle ore 07:21:07