Siddiqui M A R, Bhattacharjee J, Das Z C, Islam M M, Islam M A, Haque M A, Parrish J J, Shamsuddin M
Department of Surgery and Obstetrics, Faculty of Veterinary Science, Bangladesh Agricultural University, Mymensingh, Bangladesh.
Reprod Domest Anim. 2008 Feb;43(1):74-9. doi: 10.1111/j.1439-0531.2007.00857.x.
Shortening age at puberty of crossbred breeding bull is an important issue in the tropics. This study aimed at selecting crossbred bulls at earliest possible age with bigger scrotum and potential for donating quality semen. One hundred and 31 pre-joining crossbred bulls of Central Artificial Insemination Laboratory, Saver, Dhaka were examined. The bulls being trained by seeing semen collection from mature bulls were allowed ejaculation into the artificial vagina at homosexual mount during a 20 min time at three occasions, every three months. Eighty one of 131 bulls produced at least one ejaculate during the study and their mean +/- SD age and scrotal circumference (SC) were 20.3 +/- 4.7 months and 28.2 +/-2.7 cm, respectively. Bulls' body weight, body condition score (BCS) and SC influenced the attainment of their puberty (p < 0.05). Bull's body weight had positive effects on scrotal circumference and ejaculate volume (p < 0.05). Scrotal circumference positively influenced the percentages of normal spermatozoa (p < 0.05). Scrotal skin-fold thickness negatively influenced the proportion of spermatozoa with normal head (p < 0.05). Based on age at first ejaculate and SC, 29.6% bulls (n = 24) were selected by cluster analysis. Selected bulls had mean +/- SD age 17.9 +/- 2.2 months, body weight 287.3 +/-48.6 kg, SC 30.5 +/- 1.5 cm, ejaculate volume 3.4 +/- 1.3 ml, sperm motility 50.8 +/- 17.2%, total spermatozoa per ejaculate 2541.9 +/- 1699.2 million and normal spermatozoa 81.5 +/-14.5%. The selected pubertal bull group was different from the unselected pubertal bulls at MANOVA (p < 0.0001). About 30% of pubertal crossbred bulls can be selected with shorter age and larger scrotum at puberty under conditions prevailed in Bangladesh.
缩短热带地区杂交种公牛青春期的年龄是一个重要问题。本研究旨在尽早选择阴囊较大且有捐献优质精液潜力的杂交种公牛。对达卡萨弗中央人工授精实验室的131头配种前杂交种公牛进行了检查。通过观察成熟公牛采精对这些公牛进行训练，每三个月在20分钟内让它们在同性爬跨时向人工阴道射精三次。131头公牛中有81头在研究期间至少产生了一次射精，它们的平均年龄±标准差和阴囊周长（SC）分别为20.3±4.7个月和28.2±2.7厘米。公牛的体重、体况评分（BCS）和SC影响其青春期的到来（p<0.05）。公牛体重对阴囊周长和射精量有积极影响（p<0.05）。阴囊周长对正常精子百分比有积极影响（p<0.05）。阴囊皮肤褶皱厚度对头部正常精子的比例有负面影响（p<0.05）。根据首次射精年龄和SC，通过聚类分析选择了29.6%的公牛（n = 24）。所选公牛的平均年龄±标准差为17.9±2.2个月，体重287.3±48.6千克，SC 30.5±1.5厘米，射精量3.4±1.3毫升，精子活力50.8±17.2%，每次射精的总精子数2541.9±1699.2百万，正常精子81.5±14.5%。在多变量方差分析中，所选青春期公牛组与未选青春期公牛不同（p<0.0001）。在孟加拉国普遍存在的条件下，约30%的青春期杂交种公牛可以在青春期时以更短的年龄和更大的阴囊被选中。
