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Selection for economic characters in Merino sheep PDF

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Preview Selection for economic characters in Merino sheep

NOTE TO USERS This reproduction is the best copy available. ® UMI Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. u a m i m *» bcoiomic Q m m m m s m M2KIH0 O P by frederick Barold Willim Jforley A Dissertation Submitted to the §taAmt# Faculty in Partial fulfillment of The Requirements for the Degree of DOCTOR Of PHILOSOPHY Major Subject®: Animal Breeding Senetlcs hffroyed* m i ^ 7 ■ ■ *»«** " - * - ids of Major Departments ean of Graduate College Iona State College 1950 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UMI Number: DP13383 INFORMATION TO USERS The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleed-through, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. ® UMI UMI Microform DP13383 Copyright 2005 by ProQuest Information and Learning Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. ProQuest Information and Learning Company 300 North Zeeb Road P.O. Box 1346 Ann Arbor, Ml 48106-1346 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. S F 373.M 5 M 8 2 . s ii Stti1; Of OOBf SB s ■ Big® I, ' ' i II, mt moBim.............. .............. § in. t m w m « i mnosAM. .................. a A, fhe S n v i r o n m o n t , . 8 3.t9fc» Sheep...... 11 6. She Characters Observed.............. 13 If. »SfI«A*Ii 'or VUtm&lQ RAMWfSBS,... . . . . . * A. Phenotypic Meaae, fariaaees sad @#«rela» tioBs....................................... 26 1. source of lata*..................... 36 2. Besulte............................. 26 B. BepeataMllty. ..... 34 1. definition. ....... 34 2. lata used and Methods of analysis... 3? 3. Results.... 40 4. Comparison with published estimates. 44 0. leiatire Kconoiaic Values.................... 47 v. r a of M in a si A. HerttaMllty....... 51 1. Definition......... 51 2. Methods and results............... 52 B. tenetic Correlations Between Various Characters...... 63 1. Definition............ 63 2. Methods .... 63 3. Results 65 VI. CALOULAf I0M OF A SBLiSC'HOli IMDSX. ....... 68 VII. ®180tfSSl«,...... 83 A. General Restrictions........................ 83 1. fbenetypiG Statisiiee.*..,.................. 84 C. Genetic Statistics....... 88 T 7 3 7 - V Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. in P«Nge VIII, iOT IX* It© x, umio&Msrar** * * . * . , u* xi* m ' Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. i, stisMfoiiGs The Australian Merino sheet 1* probably one of the h»st demonstra­ tions of the power of selection to Improve production in a domestic animal. Becords of average wool production from Balgety1 s Animal leview (ltd®) show an increase la average fleece weight from 4.9 pounds for the five year# eating 1981 to 8.2 pounds for the five year* ending 1948 (fig. 1), tome of this increase has probably resulted from improved husbandry, including nutrition, disease control and control of external ant internal parasites. Some may also he accounted for by dis­ continuation of the practice| common ever §8 years ago, of washing sheep before 'shearing. the following considerations suggest that genetie change has been responsible for some of the improvement, firstly, the majority of sheep la Australia are grated In semi-arid regions in which nutrition is gen­ erally beyond the control of the pastoralist, except Insofar as stocking rats Is controlled. Apart, from brief periods of submaintenance feeding during severe droughts, sheep seldom receive supplementary feed end are wholly dependent on pasture. While pasture improvement has increased production considerably on seas properties (Gluniee loss et al. 1987), its offset on the general average wist be rather unimportant when one considers that only a small proportion of sheep are graced on improved pastures. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. -2' r 3> o f ) s d n u o p IO o> n i. (6 4 9 p1 e e Shto CO n6 o> ia188 l ram to sr uf A of ds o O) hts Peri eigr Wa e Y e- ce ev ei lF F e g a r e v A O) . 1 CO e r u g i F 00 00 O Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ' -3- the rapid improvement fit*® during the early part of the period appears to h^y# become slower during the last three decades. Many of'th® important advances 1m nutrition, disease centre! and parasite control took'.place during the lSi@*s and 1930*s, whereas the greatest increase In fleece weight occurred prior to 1920, a-period when centre!' of internal parasites each as the stomach worm (laeaonehua contortus) 'and intestinal worms (f richestrongylid spp.), as well' as sheep blowfly (hacilia cuprina Sc.), was relatively crude sued Inadequate. these reasons for considering genetic factors as having teas important receive substantial support from' observations on a museum flock at Camden Park, lew tenth Wales, which has hem maintained relative* ly free from selection and without introduction of breeding stock, these sheep as® an altogether different type from the majority of stud Merino sheep seen today, having smaller frame, smoother shine and cutting much lighter fleeces of finer wool. While there is thus considerable cause for breeders* satisfaction 'With the progress achieved, there 'are some indications that selectlea may -have reached a point of diminishing returns, the Increase la fleece weight ever the Inst'19 years has not beta substantial when one considers that some of the greatest improvements la husbandry 'have occurred during this period. Shifting emphasis from wool production to other characters may 'have retarded improvement in fleece weight, Changing economic and ecological circumstances have necessarily directed selection from fleece weight towards other characteristics. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. •>4** for example the blowfly menace tea compelled breeders to practice selec­ tion .against fold®, end a rapidly lavoicping f»t-laifi» industry haa demanded eeloetioa for * ior§#-ft»«e4 sheep suitable for use as a anther of crossbred lambs. Such attention toother ehansciere haa caused the problem of eoleetleit to become .tamMiad? complex, a situation only to bo expected in a ^rural sad industrial economy undergoing rapid expansion sad dtversification. • fh* develop*®!*! of synthetic toxtiloe servos to emphasise the relative lasfo-ytiince of the attributes of wool which compete with or t#»i&««»e»t those of man-made fibers, that, develop­ ment may shift attention rapidly t© ■fharscterlstlce of wool not previous­ ly considered important. With these considerations in mini* the present study was undertaken I® explore- and clarify sows-, of the problems confronting the breeder under existing circumstances, and -if possible, to euggest measures which might improve efficiency of selection. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.

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