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This study was undertaken to assess the reproductive performances of sheep at field level of Rajshahi and Mymensingh district of Bangladesh during January to December, 2016. A total of 52 farms (26 each in Rajshahi and Mymensingh) were selected for determining the reproductive parameters of ewes. Ewe lambs in Mymensingh reached puberty at significantly (P<0.03) younger age (186.9±18.4 days) than in Rajshihi (199.9±24.9 days). The average age at first pregnancy was 201.4±20.0 days in two regions. Similarly, the ewes in Mymensingh was lambing at significantly (P<0.002) early age than ewes in Rajshahi (356.0±6.8 days vs. 372.7±27.8 days). The observed duration of oestrus at Rajshahi and Mymensingh was 36.0±6.7 hrs and 36.0±7.3 hrs, respectively. The gestation length varied from 145 to 150 days. The average gestation length was 147.9±3.4 days in two regions. The gestation length was not significant (P˃0.05) in the ewes between Rajshahi and Mymensingh (148.7±3.4 and 147.1±3.2 days; respectively). The pooled over litter size was 1.6±0.2 in two regions. However, there was no significant (P>0.05) difference in litter size of ewes in Rajshahi and Mymensingh region (1.7±0.2 vs. 1.6±0.2). The pooled lambing interval was 193.9±21.7 days in two regions. Mean birth weights of lambs, weaning weight and mature weight were 1.7±0.6 vs. 1.3±0.1 kg; 8.9±2.7 vs. 6.9±1.0 kg and 24.9±7.3 vs. 19.4±2.7 kg in Rajshahi and Mymensingh, respectively. These reproductive parameters were significantly higher (P<0.001) in Rajshahi compared with in Mymensingh. The reproductive parameters are almost similar between confined and the traditional management system if the farms are well managed.

This study was undertaken to study the AI conception rate using frozen semen at field level. Five farms in Mymensingh, Bangladesh were selected for AI Trial in field ewes. Four rams were selected for semen collection, evaluation, and frozen semen production and further to study conception rate followed by intracervical AI in both natural and synchronized ewes. Conception rate were confirmed by non-returned rate and ultrasound scanning at 30-40 days of post insemination. The volume, colour, mass activity, sperm motility, viability, concentration, HOST +ve (%) and normal spermatozoa percentages were 0.8±0.3 ml, 3.9±0.3, 4.4±0.6, 81.3±5.0%, 90.0±4.0%, 3519.0±545.6x10 6 /ml, 87.4±3.3% and 85.6±1.8%, respectively. The sperm concentration of ram R#6 was significantly higher (P<0.05) (4120.5±93.5x10 6 /ml) compared with other rams. The mean motility and viability of pre-dilution, 120 minutes of addition of Part-A, 240 minutes of addition of Part-B and post-thaw were (83.8±4.8%, 81.3±2.5%, 80.0±4.1% and 41.3±9.5%) and (93.3±1.0%, 90.0±1.4%, 88.8±1.0% and 58.3±8.7%), respectively. There were no significant difference (P˃0.05) between pre-dilution and post-dilution sperm motility and viability percentage however, post-thaw sperm motility and viability significantly (P<0.05) decreased compare with the motility and viability of pre-dilution and post-dilution values. Motility and viability percentages of frozen semen did not decrease significantly (P> 0.05) with the increase of preservation time. The mean motility and viability at 24 hrs, day 7, day 15 and day 30 were 41.3±9. 5%, 41.5±8.5%, 41.8±9.9% and 40.5±10.2%; and 59.0±10.1%, 58.5±7.7%, 59.0±8.8% and 57.8±8.3%, respectively. The conception rates in natural and synchronized estrous were 26.7% and 25%, respectively. There was no significant difference in conception rates between the natural and synchronized oestrous in field level. However, the present non-return rate and conception rate indicate the suitability of produced frozen semen application in the field level.

The experiment was conducted in a well-known private livestock research and development farm in Bangladesh to find out the variation of semen quality parameter among three generations (F1, F2 and F3) of Holstein Friesian upgraded breeding bulls. A total of 312 ejaculates were collected from 6 upgraded breeding bullsthrought the experimental year. The recorded data were summarized using Microsoft Excel 2010 and analyzed using GraphPad Prism 5 softwere. Out of the 312 ejaculates, 273 (87.50%) were found to be creamy in color followed by 26 (8.33%) and 13 (4.17%) as yellowish and watery, respectively. Generation had significant (P<0.05) effect on ejaculate volume, consistancy, mass activity, sperm concentration, initial and post freezing motility. The highest (7.389±0.19ml) and the lowest (5.156±0.13ml) volume of semen were found in third (F3) and first generation (F1), respectively. The mass activity ranges from 3.74±0.04 to 4.30±0.05. Sperm concentration and pH varied insignificantly (p>0.05) but initial motility and post freezing motility had the significant differences among the three generations. Initial motility ranges from 75.87±0.32 to 78.40±0.38 percent and the post freezing motility ranges from 50.38±0.41 to 52.16±0.43 percent. It could be concluded that most of the semen quality parameters were influenced by generation and freezing. Semen characteristics were better in F2 followed by F3 and F1 generation in upgraded Holstein Friesian bulls. Res. Agric., Livest. Fish.7(3): 457-463,  December 2020