Factors affecting conception rate on artificial insemination in goats

Abstract

With the objective of evaluating the factors affecting conception rate on artificial insemination in goats, a study was carried out at Artificial Insemination Centre, under the department of Animal Reproduction, Gynaecology and Obstetrics, College of Veterinary and Animal Sciences, Mannuthy, Thrissur using 22 ejaculates collected thrice weekly from an adult Malabari crossbred buck. Semen samples for chilling were diluted in Tris-yolk buffer and preserved at 3-5oC for 72 hours. Cryopreservation was done in Tris yolk glycerol extender after the removal of seminal plasma. The semen was diluted and packed in 0.25 ml straws and each dose contained 200 million progressively motile sperms before processing.

A total of 44 adult healthy does brought to the AI Centre for insemination were selected for the study after detecting heat using buck jar technique. Selected does were at random allotted to four groups with eleven animals in each group. Does belonging to Group I, II and III were inseminated using chilled semen having motility over 35 per cent and stored for 0-24 h, 24-48 h and 48-72 h respectively. Animals of Group IV were inseminated using frozen semen having a minimum of 35 per cent post thaw motility. Transcervical insemination was carried out in the does in oestrus by speculum method. The depth of penetration of AI gun was assessed using another sheath as yardstick. Pregnancy diagnosis was performed at two months of gestation by ultrasonography or at three months of gestation by abdominal palpation.

Average volume, density and mass activity of buck semen were 1.25 ± 0.97 ml, DDDD and ++++ respectively. Colour of the semen was creamy with a yellowish tinge. Average semen pH and sperm concentration were 6.89 ± 0.21 and 2781.82 ± 51.69 millions per ml respectively. The mean percentage of initial motility, sperm viability, abnormality and intact acrosomes was 82.77 ± 0.33, 90.14 ± 0.53, 2.28 ± 0.12 and 92.27 ± 0.21 respectively.

The percentage of sperm motility at 24, 48 and 72 h of preservation at refrigeration temperature was 70.25 ± 0.60, 61.13 ± 0.72 and 42.81 ± 0.95 respectively. The live sperm percentage dropped to 83.42 ± 1.27 at 24 h, 78.84 ± 1.47 at 48 h and 74.57 ± 1.53 at 72 h of preservation by chilling. The percentage of sperm abnormalities increased to 2.97 ± 0.13 at 24 h, 4.12 ± 0.15 at 48 h and 5.34 ± 0.11 at 72 h of preservation. The percentage of intact acrosomes was 90.27 ± 0.18 at 24 h, 87.71 ± 0.37 at 48 h and 85.09 ± 0.44 at 72 h of refrigeration storage. There was significant difference between sperm motility, viability, abnormality and acrosome integrity at various storage periods.

The percentage of sperm motility of 78.50 ± 0.50 at the end of initial extension decreased to 37.67 ± 0.49 after cryopreservation. The mean live sperm percentage was 84.66 ± 0.91 at the end of initial extension which after freezing and thawing dropped to 60.36 ± 0.77. The mean percentage of sperm abnormalities increased from 3.82 ± 0.12 to 6.34 ± 0.22 at the end of cryo preservation. The mean percentage of intact acrosomes was 85.68 ± 0.72 at the end of initial extension which showed a decrease to 76.06 ± 1.41 after cryopreservation. There was significant difference (p<0.01) between semen quality of frozen semen and chilled semen at various storage periods.

Predominant behavioural signs observed using “Buck jar” technique were bleating, wagging of tail, frequent urination and flehmen reaction with an average intensity of heat score 2.91 ± 0.10. The major clinical signs were vulval oedema, moistness and hyperaemia of vagina, mucus discharge and opening of cervical os. Average depth of penetration of AI gun was 20.07 ± 1.35 mm.

Overall conception rate in does inseminated using chilled semen was 72.73 per cent. Conception rate in Group I, II and III were 81.82, 63.64 and 72.73 per cent respectively, which did not differ significantly. The conception rate in does inseminated using frozen semen was 27.27 per cent.

The study indicated that progressive motility and fertility of buck semen decrease on freezing causing a significant (p<0.01) reduction in conception rates compared to chilled semen. Intensity of heat and depth of penetration of AI gun have significant correlation with pregnancy status of does inseminated using frozen semen. The study revealed that liquid storage of buck semen under refrigeration is a viable alternative for propagation of germplasm of superior bucks with low freezability as it ensures better conception rates.