Aspects of artificial breeding in goats

This study examines some aspects of the application of artificial breeding technology to the breeding of Cashmere goats. The development of young male Cashmere and Angora goats was also studied. Experiments were undertaken to develop a simple procedure for freezing caprine semen in polyvinyl straws suspended in liquid nitrogen vapour. Such a methodology was determined and assessed in the laboratory against a more conventional method of freezing semen in pellets on solid carbon dioxide (dry ice). Acceptable rates of sperm survival after freeze-thawing were achieved for the straw freezing procedure. However, sperm survival was greater after freezing semen as pellets. Artificial insemination programs were conducted with the aim of improving fertility from both laparoscopic and cervical insemination procedures in Cashmere goats. The factors examined included the hormonal control of ovulation, the time of insemination relative to ovulation, the number of motile sperm inseminated, the depth of cervical insemination, and the age and parity of the females. Fertility was improved by insemination prior to the estimated time of ovulation, and with increasing depth of cervical insemination. Fertility was reduced in kid maidens compared with both hogget maidens and multiparous adult does. Fertility resulting from the laparoscopic insemination of semen processed and frozen as pellets and straws was also assessed. The fertility achieved with straw frozen semen was not significantly less than from semen frozen in pellets. A method was investigated for production of inseminate containing high densities of motile spermatozoa for use in cervical insemination. This semen was frozen at dilution rates of 1:0.5, and 1:1 (Semen:diluent). Whilst the percentage of spermatozoa surviving this process was lower than for conventional dilution rates (1:2), the concentration of motile spermatozoa was up to 1.8 times greater in semen frozen at 1:0.5. There was no benefit to fertility from this technique, although fertility was not significantly reduced. Fertility was not significantly affected by timing of insemination, double insemination or the number of motile sperm inseminated. In addition, a small study was also conducted to examine the affects of breed (Cashmere and Angora), early weaning and foster rearing on the early growth and development of young goat bucks. There was no significant affect of rearing strategy on live weight or testis weight. Testis weight was more closely related to live weight than age in the young buck, and was highly predictable from measures of scrotal circumference. The growth and development of the smaller group of Angoras studied was significantly slower than that of the Cashmeres. Late spermatids and released spermatozoa were observed in 48% of the semifflferous tubules of Cashmeres at mean age 19 weeks and mean live weight 16.8 Kg.