Animal Reproduction Science, 20 (1989) 67-69 67 Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands

Short Communicat ion

Studies on the Age of Puber ty of Najdi Rams

S.E.A. ABDEL RAHIM, M.A. SHARABY and I.O. SULEIMAN

College of Agriculture and Veterinary Medicine, King Saud University, Gassim Branch, Bureidah, P.O. Box 1482 (Saudi Arabia)

(Accepted 28 December 1988)

ABSTRACT

Abdel Rahim, S.E.A., Sharaby, M.A. and Suleiman, I.O., 1989. Studies on the age of puberty of Najdi rams. Anita. Reprod. Sci., 20: 67-69.

The state of physiological puberty of 29 Najdi ram lambs was studied. Results indicated a gen- eral trend of increase in testicular and epididymal size and weight with the advancement of age. At 23 weeks of age, when body and carcass weights were less than 25 and 15 kg, respectively, 60% of the rams had mature spermatozoa. The mean body weight at puberty was 34.4 kg. Accordingly, it is recommended that Najdi ram lambs with higher growth rates and larger testicular size could be selected for breeding purposes.

INTRODUCTION

Earl ier studies on tempera te sheep breeds indicated tha t sexual development and puber ty are closely associated with age and body weight (Drymundson, 1973 ), photoper iod st imulat ion (Land, 1978), breeding season (Ducker et al., 1973) and test icular diameter (Land and Sales, 1977). However, only limited data are available on the sexual development of Najdi rams, the most predom- inant mut ton sheep of the Gulf region.

MATERIALS AND METHODS

A total of 29 purebred Najdi ram lambs were slaughtered at the age of 13-34 weeks. Slaughter and hot carcass weights were recorded to the nearest 0.5 kg. The weights of testes and epididymes were recorded to the nearest 0.5 g. Se- cretions were squeezed from different par ts of the epididymis and stained with 5% eosin-nigrosin stain and examined under the microscope. The state of physiological puber ty was established by the presence of mature spermatozoa (normal spermatozoa without protoplasmic droplets) in the tail of the epididymis.

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TABLE 1

Mean and standard error of body weight, carcass, testicular weight, testicular volume and epidi- dymis weight of pubertal Najdi ram lambs at different ages

Age No. Pub. 1 Body Carcass Testicular Testicular Epididymis group of (%) wt. wt. wt. volume wt. (weeks) lambs (kg) (kg) (g) (cm 3) (g)

13-18 6 0 19.6±2.1 12.7±1.6 19-20 4 37 27.5 ± 2.4 17.3 +- 2.4 21-23 10 60 32.4 _+ 2.4 19.2 ± 1.5 24-27 9 100 34.0 +- 5.1 20.3 ± 3.1 28-34 6 100 41.8±2.6 24.8± 2.3

73.4+6.0 131.4___32 10.8+6 76.8+26.0 142.8_+24.8 12.4+__3.2 83.4+26.4 168.7+_61.0 13.6+-3.3 86.1±41.6 193.6+-64.4 12.4+-5.0

106.3 +- 17.3 206.3 ± 61.6 16.4 + 3.7

1Percentage of lambs attaining physiological puberty.

RESULTS AND DISCUSSION

Testicular parameters, percentage of lambs attaining maturity with ad- vancement of age, live weight and carcass weight are given in Table 1. The results indicated a direct effect of age and body weight on testicular parameters of Najdi ram lambs. Similar results have been reported by Land and Carr (1975) and Skinner and Rowson (1968) for sheep, and by Land and Sales (1977), Willet and Ohms (1957) and Van Demark (1956) for bulls.

Spermatozoa first appeared in the epididymis at 18 weeks of age. At 20 and 23 weeks, mature spermatozoa were found in the epididymis of 37% and 60% of the ram lambs, respectively. However, at 24 weeks, 100% of the lambs had mature spermatozoa and attained physiological puberty. At this stage the an- imals weighed about 35-45% of their adult body weight. However, not only was a certain testicular size necessary to attain puberty but also a certain chrono- logical age was required. These results agree with those reported for temperate breeds (Drymundson and Lees, 1972). However, Galil et al. (1986) observed that ram lambs of the same breed may not show sexual interest or mate nor- mally with ewes upon attainment of puberty. Further studies are therefore required to pinpoint the factors related to libido at this critical state of attain- ing puberty. The results of the study also indicate that Najdi ram lambs with higher growth rates and larger testicular size could be selected for breeding purposes.

REFERENCES

Drymundson, O.R., 1973. Puberty and early reproductive performance in sheep. II. Ram lambs. Anim. Breed. Abstr., 41: 419-430.

Drymundson, O.R. and Lees, J.L., 1972. Pubertal development of Clun Forest ram lambs in rela- tion to time of birth. J. Agric. Sci., Camb., 79: 83-89.

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Ducker, M.J., Bowman, J.C. and Temple, A., 1973. The effect of constant photoperiod on the expression of oestrus in the ewes. J. Reprod. Fertil., Suppl., 19: 143-150.

Galil, A.K.A., Hammad, M.H. and EI-Hadi, H,M., 1986. Reproduction in Najdi ewes. Presented at the 9th Symposium on the Biological Aspects of Saudi Arabia, Saudi Arabia, Saudi Biolog~ ical Society, pp. 242-246.

Land, R.B., 1978. Reproduction in young sheep: some genetic and environmental sources of vari- ation. J. Reprod. Fertil., 52: 427-436.

Land, R.B. and Carr, W.R., 1975. Testis growth and plasma LH concentration following hemi- castration and its relation with female prolificacy in the sheep. J. Reprod. Fertil., 45: 495-501.

Land, R.B. and Sales, D.I., 1977. Mating behaviour and testis growth of Finnish Landrace, Tas- manian Merino and crossbred rams. J. Anim. Prod. 24: 83-90.

Skinner, J.D. and Rowson, L.E.A., 1968. Puberty in Suffolk and cross-bred rams. J. Reprod. Fertil., 16: 479-488.

Willett, E.L. and Ohms, J.I., 1957. Measurements of testicular size and its relation to production of spermatozoa by the bull. J. Dairy Sci., 40: 1559-1569.

Van Demark, N.L., 1956. Quantitative aspects of semen production in bulls. In: 3rd International Congress in Reproduction and Artificial Insemination, Cambridge.