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F.W.C. Neser Animal breeding may be seen as the optimal exploitation of the species biological VARIATION Ollivier (2000) 10cm vs 2m 159kg vs 1kg Thumbeline (42cm) vs Clydesdale (2m+) You usually get what you select for – but not always Sometimes the unexpected happens The breeding of animals that are more closely related than the average of the population Increase homosigosity Decrease variation Decrease in performance, especially in fertility and survivability Affects polygenic traits because of inbreeding depression Genetic defects least of the problems Linebreeding Genetic diversity can be defined as the variation of genes and genotypes present in a population, and provide a basis of adaptive and evolutionary processes (Frankham et al., 2002) Tankwa goats Climate change Most endangered species went through genetic bottleneck Limited genetic variation within specie. Any inbreeding or wrong mating practices will destroy the variation that is left Create genetic lines within population Lines should be manage as one population Sires should be rotated between lines using as specific order This way inbreeding will be limited and new diversity can be created Recordkeeping Indekse Blup – Teelwaardes Groter akkuraatheid Komplekse Modelle Seleksie vordering Genetic trends for milk production in the SA Holstein and Jersey population 200 0 -200 -400 -600 -800 -1000 1983 1985 1987 1989 1991 1993 Holstein 1995 Jersey 1997 1999 2001 2003 2005 Seleksiedoelwitte Telers geen doelwitte Teveel produksie te min fiksheid Inteling VSA -3.7 milj Holsteins Effektiewe populasie grootte 60 diere • Jersey’s 38 diere Inbreeding USA average; - F = 5.85% (2012) 1910 1930 1950 1970 1990 2010 Fiksheid = NATUURLIKE SELEKSIE: Oorlewing Vrugbaarheid Fiksheid dui op die relatiewe vermoë van draers van ‘n spesifieke genotiepe om hulle gene na die genepoel van die volgende generasie oor te dra. Dit word die aanpassingswaarde of die fiksheid in die Darwin sin, van ‘n genotiepe genoem (Dobzhnsky, 1959) The heritability of fitness traits are usually low and will be severly influence by inbreeding depression and heterosis (Bourdon, 1997) + GENES FOR FITNESS INTENSIVE SYSTEMS NATURAL PASTURES Selection for growth under different conditions Environmental limit No limit on size Environment limit size Natural conditions Artificial conditions This is where an animal excels in one environment but fail to perform in a second environment, while another animal may excels in the second but fail to perform in the first Genotype for: High appetite Large Frame P r o d u c t i v i t y High heat production Genotype for: Optimum Low appetite Small Frame Low heat production Unfavourable No genotype, no matter how versatile, is equally efficient in all environments - Dobzhansky (1951) Alle diere is ewe vrugbaar Vrugbaarheid kan nie geneties verbeter word nie Voer jou diere vrugbaar MINDER VRUGBAAR NIE GEKALF BOGEMIDDELD VRUGBAAR Eers net kwaliteits eienskappe Produksie eienskappe Vleissagtheid Marmering Voeromsetting Vrugbaarheid Groei Melkproduksie Wolproduksie/Veseldikte Skape – 753 QTL’s, 212 eienskappe Beeste – 6 305 QTL’s, 416 eienskappe Nie die “Magic bullet” nie Hoofgeen verklaar tot 30% van σa2 Meeste QTL’s verklaar baie min – minder as 1% van die σa2 Belangrikste eienskappe word deur baie gene beinvloed Omgewing skakel gene aan of af Patentereg – groot maatskappye DNA Fingerprinting: Parentage verification Microsatellites & SNP: Inbreeding Heterozygosity and genetic variation Specie verification Whole genome sequencing Genetic variation Limit inbreeding Maintain genetic diversity Work with the environment Recordkeeping