Abstract:
WRINKLE SCORE SELECTION AND REPRODUCTIVE PERFORMANCE OF MERINO SHEEP IN NORTH WEST QUEENSLAND Differences in reproductive performance of groups where rams were selected for high wrinkle score (Wrinkly) and low wrinkle score (Plain) were small but the Plain group performed better at all stages of reproduction. Differences in mean wrinkle score of the groups were also small. However there has been a far greater decline in ewe numbers in the Wrinkly group so the use of plain-bodied rams offers some benefit in performance in this harsh environment. I. ItNTRoDucTIoN Raproductiveperformance of&&in0 sheep innorthwest Queenslandis extrerrely lcw (mse 1972) so the definition of selection criteria for breedingsheepbetter abletoprodu~ in this envir ormentwouldbeof considerable benefit to producers. Dm (1964) reported a 1-r net reproductive rate for a Merino flock selected for skin fold than for a flock selected against skin fold. Drinan and Dun (1965) in a study in 14 New South Wales flocks reported an overall17percentadvantage inl&srnarkedforplainewes campared withdevelopedewes. Howeveron'halftheproperties increasingwrinkle scorewasnotassocia~dwitharrrarked~crease in fertility. Dun (1964) suggested that skin foldmuld be a nwlre irrportant fault the store ' difficulttheentironmant. ,Thispaperreportsthe~p~u~~performanceof ewes in groups where rmwere selectedforhighandl~wrinkle score andinarandcm groupatJuliaCreektinorthwestQueensland. II. MATE?lRIcALs AND METHODS The experimental flock was run on Toorak Sheep Field Research Station, Julia Creek. Theenviro~tandflockhistoryhavebeen described previously (Beattie 1961; mse 1972). an 1959 them flock was dividedinto three groups basedonwrinkle score using the photographic standards of Turneretall (1953). Ewes -m were scoredwithina* groups andplacedinorderbasedonthis score. TheRantigroupaamprisedeverythirdewe. Theremainingeweswere divi~dinto~o~~s;~swithl~rscores formingthePlaingroup andtheothers theWrinklygrow. Noeweswere culledduringthe expertit. Ramselectionwas basedprimarilyonwrinkle score. Plain rams were sele~dfrcanthosewiththel~stscores intheplaingroup and Wrinkly rams fromthosewiththehighestsaores intheWrinklygroup. The selectedplain andwrinkly ramswere joinedtoewes in the Ranti group so that equal numbers of Random ewes were joined to Wrinkly and Plainrm. * Departrrrentof Primary Industries,Brisbane,Q. 101 4000. III. RESULTS Figure 1 shows the maan wrinkle score (neck + side score) for the ewes ineachwrinkle group as scoredimuediatelyaftershearinginJune/ July of each year. The differenoe in scores achievedatthe formationof the groups was 1.6 and was little changed by selection. The difference belxm scores for the Plain and Wrinkly groups was only 2.2 at its maximum (1970) and at its minimum 1.3 (1966, 1971, and 1973), the'Randam groupbeingintermzdiate inscore. Reproductive performances for wrinkle groups and season of joining Tablelshows the reproductiveperformanceof thewrinkle grouq?s recorded at stages of the reproductive cycle for autumn and spring joinings. Performances of allgroupswereextremzlylow. However the Plain groupperformedconsis&ntlybetter than thewrinkly group. 102 Theperformnaz of the Randcmgroupwas intenrrediati ti theothergrows. The differences bel~een groupswerenotstatistically significant. Neonatal losses (Table 2) were emly high in all groups being highest in the Wrinkly group andlowestin the Plain group,exoeptfor the period frcgn 7 days to marking (spring joining). Losses in the Random groupwere againintermediati ti theothergroups. Differencesbe-groqs were not statistically significant. TABLE2 Neonatal losses for wrinkle groups and season of joining Age specific death raes in ewes in the two groups showed little difference in adult death ratis for either autumn or spring joinings but more Wrinkly ewes died bel~een birth and first joining at 1.5 years. When the groupswere joinedin aut'uIIII130 percentofWrinklyewes and25 percentofplainewes tiedbeforeentiringthebreedingflockandwith spring joining ewe losses prior to first joining were 52 per cent -in the Wrinklygroupand 32 percentintheplaingrow. IV. DISCUSSION Selection in the wrinkle groups has only maintained the difference inwrinkle score achievedatthe formationof the groups. The expression ofwrinklinesswas greatestinyearswithrtore favourable seasonal conditions. Howeverevenin1962wh~ thewrinkle scoreswerehighest theman side scoreof theWrinklygro~was only 3 on the scale fram0 (absenceofanybodywrinkles) to 5 ( extrer~ly wrinkled). These ewes were only erately wrinkled although the mean neck score of 5 on the scale from0 ti 6 shacJeda~arativelyhighdegreeofwrinklingonthe neck. In most years sheep in all groups were relatively plain-bodied. Themainreason forthevery small differences achievedinwrinkle score for the groups over more than *lve years of selection was probably the la& of any effective selection differential. sarently in sheep bred and selec&d in the area natural selection keeps wrinkle scores atalowlevelso little response canbeexpectedbyselecting for plain-bodied sheep angst those bred in the area. Although the differences inwrinkle score andreproductive performance recordedforthePlain andwrinkly groupswere small they were consistentandsupportedthe relationshipof increasingwrinkle scorewithdecreasingreproducti~performanoe. 103 Attheendoftheexperimnttheplain gmupwasmxe than twice the size of the Wrinkly one. Since thereweremlysmalldifferences in the groups' reproductiveperfomance anddeathrates oflmbs andadultewes, the Wrinkly gmup's more rapid decline can only be explained by the much poorer survival rates of ewe weaners especially with spring joinings. Inthisharshenvir onmnt there is sorre advantage in keeping the ewe flock as plain as possible. This canbe achiewdbythe useofplainbodiedrams. kbre research is required to define the characterswhichenable sheeptosurvive andreproduce in this area. Studies are ccntinuingat Julia Greek into sheep better adapted to the harsh conditions as well as intootheravenues of improvingreproductiveperformnce through the melioration of the effects of heat and poor nutrition. v. AcKNaiLlx- Grateful ackncwledgemnt is made of the assistance of Miss mslyn Grantwhomaintainedthe records andof themany staffmrribers of?roordk Sheep Field Research Station who have collected these records. VI. REZFERENCES BEA!!, A.W. (1961). QuemslandJourmlofagricultural Science, 18: 437. D-7 J.P., and DUN, R.B. (1965). AustralianJoumalofexperimntal Agriculture andAnimalHusbandry, 5: 345. DUN, R.B. (1964). AustralianJoumalo=fe~~~~Agriculture and Animal Husbandxy, 4: 376. ROSE, Mary (1972), P&dings 0ftheAustralian Society of-1 Production, 9: 48. TURNER, Helen New&, HAYMAN, R.H., RICHES, J.H., mBER!IS, N.F., and WILSON, L.T. (1953). CSIRO Division of Animal Health and Production. Divisional Rqqrt No. 4 (Series S.W:2) 104