Adaptation in Beef Cattle

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  • 1. Adaptation in Beef Cattle T. G. JenkinsMeat Animal Research CenterClay Center NE1

2. ADAPTABILITYFrequently a focus of discussionbut are we all discussing the sameconcept? 2 3. Objectives: 1. What is meant by Adaptability2. Evidence of Adaptability in beef cattle 3. Potential for application3 4. TerminologyPhenotype: the appearance of anindividual resulting from theinteraction of genotype andenvironment Genotype: total sum of all genetic factors of an individual Environment: all factors that influence the expression ofgenes4 5. Types of AdaptabilityEvolutionary: Trans-generationalPhenotypic: adjustments made byindividual within a lifetimemay be linked to biologicalprocesses that areevolutionary5 6. ADAPTABILITY- Evolutionary - Provides a species the ability for continued existence (trans-generational) adaptability could be considered an optimization of a phenotype to express fecundity potential What creates a need for the organism to change?6 7. Changes in conditions in which affects the expression of the fecundity potential of species Environment geographic location food resources climatic conditions pathogens etc7 8. What allows the species to change: Genetic variability Individuals exist within a population whose genotype provides a selective advantage in the altered environment allowing these individuals to leave greater number of offspring mutationsexisting alleles8 9. Existing alleles (Mayr, 1970)In manufacturing districts of England mothchange color from white to black because ofpollution. Predators were able to see whitemoths so black had selective advantageMutation (Nature Biotech, Feb, 1999) Specific strains of Salmonella have become resistant to antibiotics (Amoxicillin, Flofenicol, Streptomycin, Tetracycline) 9 10. Phenotypes vary because genetic variation exists in population that enable forces of change (environment) to alter genotypic frequenciesSelection 10 11. Evidence for adaptation in beef cattleGeographic location Ngunni in Africa tsetse fly Bonsmara Animals that suffer from hyperthermiehave an increased respiratory and pulse rate with concomitant metabolic, physiological andendocrinological disturbances. Head shapeBreeds foundation phase frequently associated with geographic location, enhancefrequency of alleles of favored phenotypes11 12. Effecting genetic change may or may not lead to alleviation of environmental constraint.FailureComposite population in Venezuela (all made using 50% Zebu and 50% unadapted Bos taurus breeds) appeared to have failed to produce productive cattle in spite of strong selection.Success Australian milking zebu (AMZ): Pakistani Sahiwal andRed Sindhi dairy cattle were mated initially to high-producing Jersey cattle. Later, some infusion of Illawarra,Guernsey and Holstein-Friesian bloodlines occurred.Adaptation for heat tolerance and tick resistance inbred for milk production.12 13. Texas LonghornWhy did this particular Creole type flourish in hostile nutritionally sparse environment?Resistant to tick fever 13 14. Brisket Disease is caused primarily by an oxygen shortage; oxygen availability is 17% less at 5,000 feet than it is at sea level; 20% less at 6,000 feet, 26% less at 8,000 feet, and 31% less at 10,000 feet. Cause excessive heart activity, eventually, the heart wears out and stops beating. The losses from the disease can vary depending on the origin of the cattle. In cattle born and raised at high elevations, the losses tend to run from .5% to 5%. In imported or lowland cattle the losses can range from 30% to 40%. There is test to identify animals that are resistant, moderately heritable, selection practiced to resolve 14 15. Breeds reproduction at low Levels of Dry Matter50 Red Poll Charolais AngusPinzgauer Pinzgauer40Limousin Efficiency (g/kg DM)SimmentalBraunvieh30Gelbvieh20 Red PollAngusHereford10Red Poll Pinzgauer CharolaisJenkins and FerrellAngusGelbviehLimousin .1994. JAS 72:2787 Hereford Braunvieh Simmental 0 3000 400050006000 7000Dry Matter Intake (kg/yr)15 16. Potential applications of Adaptability in Beef Cattle Production16 17. Forage selectivityParasite resistance Endophyte resistanceHeat resistanceWater needsNutrient use 17 18. What is required to implement Adaptability to improve beef productionRecognition of novel phenotypes associated with economically important traits Determination if phenotype can be measured accurately Assessment of variation associated with phenotype Proportion of variation attributable to genetics Programs to implement change 18