Buffalo bull spermatozoa are rich in polyunsaturated fatty acids and are prone to lipid peroxidation. We hypothesised that lipid peroxidation in buffalo bull semen will increase with age and will affect the semen quality. The objective was to compare malondialdehyde (MDA) concentration and the quality of fresh and frozen-thawed semen between aged (13.6 ± 1.0 years; n ¼ 3) and young (3.4 ± 0.3 years; n ¼ 3) Nili-Ravi bulls. The concentration of MDA did not differ (p >.05) between aged vs. young bulls in fresh (2.3 ± 0.2 vs. 2.9 ± 0.7 nmol mL À1 ), frozen-thawed (53.1 ± 2.8 vs. 48.4 ± 2.6 nmol mL À1 ) semen and seminal plasma (5.71 ± 0.97 vs. 5.19 ± 1.36 nmol mL À1 ), respectively. In fresh semen, sperm motility and total concentration did not differ (p > .05) between aged and young bulls. The volume of fresh semen increased (p > .05) while sperm viability and DNA integrity decreased (p < .05) in aged vs. young bulls. In frozen-thawed semen, sperm motility, viability and DNA integrity decreased (p < .05) in aged vs. young bulls. In frozen-thawed vs. fresh semen, MDA level increased within young (48.4 ± 2.6 vs. 2.3 ± 0.2 nmol mL À1 ) and aged bulls (53.1 ± 2.8 vs. 2.9 ± 0.7 nmol mL À1 ). Conversely, sperm motility and viability decreased (p < .05) within the age groups between fresh and frozen-thawed semen.In conclusion, (1) lipid peroxidation (MDA) does not increase due to age; however, it is negatively associated with semen quality and (2) cryopreservation steps up lipid peroxidation irrespective of age and deteriorates semen quality of Nili-Ravi bulls.ARTICLE HISTORY

Artificial insemination is assuming great importance in the planning of livestock improvement in different countries. It has been estimated that 30 % of the total cows in Great Britain are inseminated artificially and in Denmark the number is as high as 80 %. Although sheep also play a very important role in the livestock economy of some countries, not much attention seems to have been paid to the artificial breeding of ewes. Russia is perhaps the only country where artificial breeding of sheep is done on a mass scale, and only some sporadic artificial breeding of sheep has been done in a few other countries.The preservation and storage of semen between the time of collection and the time of insemination has been in the past, and still remains at present, one of the major problems in artificial insemination. Numerous investigators have tried to prolong the storage period. Bovine semen is usually stored at 4° C. in media composed of either phosphate buffer (pH 7-4) or citrate buffer (pH 6-8) and egg yolk. The same media are used for the storage of ram semen. The motility and fertilizing capacity of bull spermatozoa in these media decline rapidly so that in practice samples are not used for insemination more than 3 days after collection. Since the concentration of egg yolk can be varied within wide limits without affecting survival, attempts have been made to improve the buffer solution. Kempschmidt, Mayer, Herman & Dickerson (1951) obtained increased survival of bull spermatozoa on storage by reducing the electrolyte concentration of the diluting medium. They found that sugar solutions, especially solutions of metabolizable sugars, were most satisfactory for replacing part of the buffer. Recently, Bishop & Salisbury (1954) have shown that phosphate and citrate buffers have certain deleterious effects on bovine spermatozoa. Investigations carried out by Roy & Bishop (1954) have further shown that replacement of the citrate or phosphate buffers by 3 % glycine markedly improved the survival time of spermatozoa. The present paper reports some observations made on the effect of these diluents on the survival of ram spermatozoa after storage at 4° C. METHODS AND MATERIALThe experiments were carried out during the months of June to August. Two rams out of the flock at the Animal Research Station were selected for the collection of semen, which was made with the artificial vagina by the method described by Walton (1945). Precautions were taken to avoid temperature shock, and after ejaculation the semen was taken in the vacuum collecting flask to the laboratory situated at a distance of about 30-40 yards from the collection site. For the most part, storage trials were done on single ejaculates, but if the volume was inadequate two ejaculates from the same ram were pooled.Motility scores with arbitrary grading on a 5-point scale were used; the highest motility scored 5 and no motility scored 0. Equal volumes of citrate buffer (2-9 % sodium citrate in H 2 O) and egg yolk served as the control diluent. Trial diluents were mad...

Experiments were made on twelve rams to determine the effects of hormonal treatment on rams with poor libido. Testosterone and PMS were used and sexual behaviour, and semen characteristics such as volume, motility, impedance-change frequency and dead percentage were studied. The libido was higher in testosterone-treated rams than in the PMS-treated, or in the control rams. Volume of ejaculate was also higher in the former group. There was not much difference in the motility ratings. Impedance change frequency was slightly lower and dead percentage higher in the semen produced by testosterone-treated rams than in other groups.