Slippers, SC

van der Merwe, HJ

van Wyk, JB

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The effect of age, frontal skinfold development andseason on libido and mating dexterity in Merino ramsH.J. van der Merwe, J.B. van Wyk and S.C. SlippersDepartment of Sheep and Goat Husbandry, Faculty of Agriculture, University of the Orange Free StateThe mating ability of 541 Merino rams from 19 different pro-ducers in the area surrounding Bloemfontein was investigated.About 23 % of the rams were not able to mate successfullywith a ewe in oestrus. This figure is a combination of 7,3 %rams showing no heterosexual sex interest and 15,8 % thatwere unable to mate successfully with an oestrous ewe withinten minutes. Age, season and frontal skinfold development didnot significantly effect (P ~ 0,05) the mating ability of therams.S. Afr. J. Anim. Sci., 1984, 14: 26 - 28Die dekvermoe van 541 Merinoramme is by 19 verskillende pro-dusente in die omliggende skaapproduserende gebiede vanBloemfontein getoets. Ongeveer 23 % van die ramme was niein staat om bronstige ooie suksesvol te dek nie. Hierdie syferis saamgestel deur die 7,3 % ramme wat geen heteroseksuelegeslagsbelangstelling getoon het nie en die 15,8 % ramme watnie in staat was om 'n bronstige ooi binne tien minutesuksesvol te dek nie. Ouderdom, seisoen en kraagontwikke-ling, het 'n nie-betekenisvolle (P ~ 0,05) invloed op die dekver-moe van die ramme gehad.S.-Afr. Tydskr. Veek., 1984, 14: 26 - 28H.J. van der Merwe*, J.B. van Wyk and S.C. SlippersDepartment of Sheep and Goat Husbandry, Faculty of Agriculture,University of the Orange Free State, Bloemfontein, 9301,South AfricaIntroductionIn the effort to increase the reproduction rate of South Africansheep flocks, the role of the ewe was emphasized in the past,whilst the role of the ram was largely neglected. It is, however,important that a ram's semen quality be high, and it shouldalso be ascertained whether or not the ram is able to mate.Pretorius (1972) stressed the importance of aberrations in thenormal mating behaviour of rams.In preliminary observations (Van Wyk & Van der Schyff,1981 - unpublished data) made of Merino rams under prac-tical farming conditions, it was established that approximate-ly 21 0,10 of the rams were unable to mate successfully withewes in oestrus. Should this be a general phenomenon amongSouth African Merino flocks, it could contribute significantlyto poor breeding rates among local Merinos. The work ofMarincowitz, Pretorius & Herbst (1966) clearly demonstratedthe practical importance of selecting rams with a good libidoand mating dexterity. According to Mattner, Braden & George(1973), this aspect is particularly important under extensive con-ditions, such as those generally experienced in South Africa.Identification of rams that are able to mate successfully witha large number of ewes within a short period of time, wouldcontribute considerably to the fertility of the flock and the nettefficiency of sheep farming. Mattner, Braden & George (1971)concluded that a simple libido test could largely contribute tothe identification and elimination of aberrant rams under flockconditions. It is consequently important that the extent of theproblem be investigated under practical, extensive farmingconditions.The aim of this study was to determine the nature and ex-tent of the problem regarding the mating behaviour and aber-rations in Merino rams at farm level.ProcedureSurveys were done on rams from 19 different producers in thesheep producing areas surrounding Bloemfontein. The libidoand mating dexterity of 541 Merino rams were determined ac-cording to the method of Marincowitz et al. (1966). Each ramwas introduced to a ewe actively in oestrus in a small pen forat least ten minutes. The time lapse between introduction intothe pen and the first attempt at mating was taken as the reac-tion time. The number of attempts made before ejaculation(mated successfully) served as a parameter of mating dexteri-.ty. The ages of the rams, varying between two-tooth andbroken-mouthed, as well as the frontal skinfold development,were noted.In order to statistically compare the effect of age, frontalskinfold development and season, an analysis of variance wasapplied.Results and DiscussionThe results of the libido and mating dexterity tests performedon the Merino rams, are summarized in Table 1. Accordingto these results 7,3 0,10 of the rams showed no heterosexual sexinterest at all. Pretorius (1967) is of the opinion that the prac-tice of rearing rams in single-sexed isolation, could contributeto the lack of heterosexual sex interest. Banks (1964) likewisepoints out that puberty is of particular importance and isola-tion during this period could most probably be responsible forthe poor development of successive sex manifestations thateventually lead to normal mating behaviour. Important,however, were the large percentage of rams that still showedno interest after repeated introductions to oestrus ewes(Pretorius, 1967).Table 1 The influence of age on the mating abilityof Merino ramsAgeFull- Broken-Parameter 2-t. 4-t. 6-t. mouthed mouthed TotalNumber of rams 222 49 80 138 52 541070 Exibiting nointerest 9,4 12,2 5,0 5,7 1,9 7,30"10 Unsuccessfullymated 18,4 6,1 11,2 13,7 26,9 15,8Average reactiontime(sec) 27,4 26,7 31,3 18,7 23,9 25,6Average matingtime(sec) 89,1 94,2 97,5 79,2 112,6 94,5Number of matingattemptsMated successfully 4,4 3,6 3,9 3,7 5,5 4,2Mated unsuccessfully 17,0 10,7 12,1 15,1 12,8 13,5According to the data summarized in Table 1, it is clear thatapproximately 15,8 % of the rams could not successfully matewith a ewe within a period of ten minutes. The poor matingdexterity of these rams is reflected in the large number ofmating attempts that were made without the ewe being suc-cessfully served.An average of 23 % of the rams were unable to mate suc-cessfully with ewes in oestrus. This corresponds well with theaverage of 20 % established by Walkley & Barber (1976a) forSouth Australian Merino rams, and compares favourably withthe 29,6 % of Hulet, Blackwell & Ercanbrack (1964) and the33,3 % reported by Pretorius (1967). Lightfoot & Smith (1968)allege that an average of 20 to 50 % inactive rams in a flockunder extensive conditions, could lead to a substantial decreasein the reproduction rate owing to the increased workload placedupon the remaining active rams. It thus seems that by identi-fication and elimination of those Merino rams that have noheterosexual sex interest and/or poor mating dexterity, thebreeding rate could be substantially increased in practice.From the data in Table 1 it is apparent that it took the suc-cessful rams an average of 94,5 seconds to mate with a ewein oestrus, after an average of 4,2 attempts. According toPretorius (1967), rams that were classified as having a goodlibido and mating dexterity took an average of 114 secondsand made an average of 3,9 attempts to successfully mate witha ewe in oestrus. The Merino rams that mated successfully withewes during the present study, displayed good libido andmating dexterity in accordance with the results of Pretorius(1967).From Table 1 it is clear that the libido and mating dexterityof rams in the various age groups did not differ significantly(P > 0,05). This implies that rams with poor mating dexteritycan be successfully eliminated at a young age (two-tooth). Inaccordance with this, Walkley & Barber (1976b) emphasizedthat young, inactive rams must not be kept until they are older,as their libido and mating dexterity will not change significantlyover a period of one or two years. The significant correlationbetween the libido of mature rams and the libido of their sonsunder paddock conditions (Mattner, Braden & George, 1974)and the greater fertility of the daughters of highly active rams(Kilgour, 1979) are both indications of the genetic interactionthat has to be considered when selecting rams. Le Roux & Bar-nard (1975) pointed out that a simple libido test couldsignificantly contribute to the identification of aberrant ramsat an early age.The influence of season and of frontal skinfold develop-ment on mating dexterity of Merino rams, is indicated in Table2 and 3 respectively. It is clear that neither of these factorssignificantly (P > 0,05) influenced the libido and mating dex-terity of rams. However, it is important to point out that afar greater percentage of overdeveloped rams failed to matewith oestrous ewes, either because of lack of sexual interest(5,0 %) or poor mating dexterity (40,0 %), the latter beingTable 2 The influence of season on the mating abilityof Merino ramsParameter Autumn SpringNumber of rams 388 1530/0 Exhibiting no interest 7,2 7,8070 Mated unsuccessfully 17,7 11,1Average reaction time(sec) 25,3 25,3Average mating time(sec) 90,2 90,9Number of mating attemptsMated successfully 4,2 4,1Mated unsuccessfully 14,8 16,7Table 3 The influence of frontal skinfold develop-ment on the mating ability of Merino ramsPlain- Over-Parameter bodied Light Medium Full developedNumber of rams 43 169 176 133 20070 Exibiting no interest 6,9 7,6 7,3 7,5 5,0070 Mated unsuccess-fully 18,6 13,0 14,7 16,5 40,0Average reaction time(see) 34,9 24,5 22,9 27,6 18,8Average mating time(see) 93,9 73,3 94,7 108,9 65,2Number of matingattemptsMated successfully 4,7 3,6 4,5 4,3 3,2Mated unsuccessfully 14,3 19,4 12,0 15,7 13,3the most important cause of mating failure. It therefore seemsstrange that frontal skinfold development (and particularlyoverdevelopment) did not have a statistically significant effecton mating dexterity. Most likely the small number of overde-veloped rams (only 3,7 070 of the total) encountered during thepresent study, contributed to this anomalous fmding. Pretorius(1967) found that as the neckfold development increases, moretime is wasted prior to copulation and more unsuccessfulmating attempts are made.ConclusionsAccording to the results of this study, 7 and 16 0J0 of Merinorams displayed no heterosexual sex interest or any mating dex-terity respectively. These aberrant rams could contributesignificantly to a low lambing percentage in Merino flocksunder local extensive conditions. Because the mating behaviourof rams does not change noticeably with age, it is essential thatthese rams be identified and eliminated as early as possible.This measure, together with tests for semen quality, shouldbe standard practice in the evaluation of rams. The practiceof rearing male lambs in isolation from ewes, should beavoided.From the results, it is obvious that both season and frontalskinfold development do not significantly influence the matingbehaviour of Merino rams. This conclusion regarding frontalskinfold development's effect on mating dexterity should,however, be treated with caution, considering that 45,0 0J0 ofthe overdeveloped rams in the present study failed to mate withoestrous ewes.VerwysingsBANKS, E.M., 1964. Some aspects of sexual behaviour in domesticsheep. Ovis Aries Beh. 23, 249.HULET, C.Y., BLACKWELL, R.L. & ERCANBRACK, S.K., 1964.Observations on sexually inhibited rams. J. Anim. Sci. 23, 1095.KILGOUR, 8., 1979. The importance of the ram on flock fertility.Wool Tech. Sheep Breed. 27,41.LE ROUX, P.J. & BARNARD, J.P., 1975. The effect of heterosex-ual contact on libido and mating dexterity in Karakul rams.Karakul 1975. (17th edition) pp.99 - 107 Windhoek: KarakulBreeders Soc. S. Afr.LIGHTFOOT, R.J. & SMITH, J.A.C., 1968. Studies on the numberof ewes joined per ram for flock matings under paddock condi-tions 1. Mating behaviour and fertility. Aust. J. Agric. Res. 19,1029.MARINCOWITZ, G., PRETORIUS, P.S. & HERBST, S.N., 1966.Dominance in sexual behaviour and mating dexterity in Merinorams. S. Afr. J. Agric. Sci. 9, 971.MATTNER, P.E., BRADEN, A.W.H. & GEORGE, J.M., 1971.Studies in the flock mating of sheep. 4. The relation of libido teststo subsequent service activity of young rams. Aust. J. Exp. Agric.Anim. Husb. 11,473.MATTNER, P.E., BRADEN, A.W.H. & GEORGE, J.M., 1973.Studies in flock mating of sheep. 5. Incidence, duration and effecton flock fertility of initial sexual inactivity in young rams. Aust.J. Exp. Agric. Anim. Husb. 13, 35.MATTNER, P.E., BRADEN, A.W.H. & GEORGE, J.M., 1974.Ram libido C.S.I.R.O. Anim. Phys. Ann. Report. 1973/74, 3.PRETORIUS, P.S., 1967. Libido en dekbehendigheid by ramme,grootgemaak en gehou in isolasie van ooie. Hand. S. Afr. Ver.Diereprod. 6, 208.PRETORIUS, P.S., 1972. Mating behaviour in rams. J.S. Afr. Vet.Assoc. 43, 155.WALKLEY, J.R.W. & BARBER, A.A., 1976a. The relation betweenlibido score and fertility in Merino rams. Proc. Aust. Soc. Anim.Prod. 11, 141.WALKLEY, J.R.W. & BARBER, A.A., 1976b. Mating performancein Merino rams. Wool Tech. Sheep Breed. 23, 21.

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The effect of age, frontal skinfold development and season on libido and mating dexterity in Merino rams

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The effect of age, frontal skinfold development and season on libido and mating dexterity in Merino rams

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