J. P. Mittal

Development and application of ovine reproductive technologies: an Indian experience

Sheep play an important role in the Indian economy by providing employment to a large population of marginal and landless farmers. The production from native breeds is relatively low due to their poor reproductive efficiency. Embryo transfer technology can be utilised for faster multiplication of elite animal to increase the genetic gain. A great deal of research is involved to overcome the constraints in the technology, i.e. expensive and complicated nature of the technology and low success rate. In order to avoid surgical involvement, procedures of laparoscope aided embryo collection and transfer have been developed. Although the use of FSH of ovine origin has given more consistent superovulatory response, but it is still too low to get sufficient numbers of progeny from a donor ewe. The progress made in cryopreservation of ram semen has opened the possibility for conservation and utilisation of frozen semen of elite rams in sheep improvement programme. The lambing rate obtained after laparoscope aided intrauterine artificial insemination with frozen semen is encouraging but the impetus is now to develop the non-invasive transcervical insemination technique.

Effect of freezing temperature, at which straws were plunged into liquid nitrogen, on the post-thaw motility and acrosomal status of ram spermatozoa

The present study was conducted to observe the effect of initial freezing temperature on subsequent survival and acrosomal integrity of Malpura and Bharat Merino ram spermatozoa during post-thawing incubation. Semen samples were diluted in TEST-yolk-glycerol extender, loaded in 0.25 ml straws and cooled down to -25, -75 or -125 degrees C freezing temperature using a programmable cell freezer. Computer assisted sperm analysis and acrosomal integrity of thawed samples were assessed after thawing and at hourly intervals during incubation at 37 degrees C for 4 h. The percentage of motile cells in samples frozen at -125 degrees C were 80.3 and 63.7 after post-thawing and -thawing incubation, compared to 75.9 and 39.7 at -25 degrees C or 73.9 and 51.8 at -75 degrees C temperatures, respectively. The spermatozoa with normal acrosome were also significantly, respectively, higher in samples frozen at -125 degrees C, compared to -25 and -75 degrees C temperatures. There were no significant breed variations on percentage of motile, percentage of rapidly motile cells, percentage of normal acrosomes, curvilinear velocity and lateral head displacement except straight line velocity and average path velocity of spermatozoa. The results indicated that -125 degrees C initial freezing temperature conferred the best cryopreserving ability to ram spermatozoa for post-thawing thermoresistance test compared to -25 or -75 degrees C freezing temperature.

Cervical penetration and transcervical AI of tropical sheep (Malpura) at natural oestrus using frozen-thawed semen

Abstract This study comprising of two trials was undertaken in ewes exhibiting natural oestrus to evaluate a simple transcervical artificial insemination technique suitably modified for use in tropical sheep. Twenty four adult multiparous Malpura ewes which had lambed 6 to 12 months prior to the experiment were utilized for two oestrous cycles during the autumn breeding season. The cervical penetration ( n =47) was conducted in both first ( n =24) and second ( n =23) trial ≤6 to 18 h following onset of oestrus, while lambing rate was assessed in the second trial ( n =23) following deposition of frozen-thawed semen having >70% mean post-thaw motility at os, mid cervix or uterus. The overall success achieved in cervical penetration was 44.7%. There was no difference in cervical penetration rate at ≤6 and 18 h after detection of oestrus (46.1% vs. 42.8%, respectively). A mean lambing rate of 22.7% was recorded in ewes inseminated using this technique. Mid cervical and transcervical insemination with frozen semen resulted in similar lambing rate (28.5 vs. 22.7%, respectively). However, no lambing was achieved on os-cervical insemination. Further efforts are needed to determine factors controlling the cervical penetration and conception rate following artificial insemination with frozen semen.

Sperm Motion Characteristics of Garole Rams Raised for a Prolonged Period in a Semi-arid Tropical Environment

The Garole is a prolific but less well known and rare breed of small sheep found in the hot and humid Sunderban region of West Bengal. An ability to breed throughout the year and to graze in knee-deep water, resistance to foot rot and a strong mothering instinct are some of the special features of this breed. Garole rams could provide germplasm to incorporate prolificacy traits by artificial insemination of the nonprolific sheep breeds found in abundance in the semi-arid and arid tropical climates of India. The aim of the present study was to evaluate the semen production by Garole rams maintained in a semi-arid climate for three years and to objectively assess their semen quality by a computer-assisted sperm analysis technique. The donor rams were randomly selected each year from the original flock procured from their natural habitat or from the offspring born at the Institute farm. Semen was collected weekly for three weeks each autumn for three consecutive years from 8 rams each year. The overall means (SD) of the traits that did not differ significantly with age or year were volume, concentration, curvilinear velocity, average path velocity, amplitude of lateral head displacement, beat frequency, motility and the percentages of rapid motile sperms and of slow motile sperms. The age of the rams had a significant effect (p<0.05) on the straight-line velocity but this was not significantly affected by the length of exposure to the semi-arid climate. However, the age and year had significant effects (p<0.05) on linearity, straightness and the percentage of medium motile sperms. It was concluded that Garole rams are capable of producing good-quality semen even after a prolonged period of exposure to a semi-arid tropical climate.

Effect of two doses of progesterone on estrus response and fertility in acycling crossbred Bharat Merino ewes in a semi-arid tropical environment

The efficacy of two doses of progesterone (P4), i.e. 350 and 300mg was evaluated in acycling crossbred ewes (50) during the autumn breeding season. Ewes were treated with intravaginal progesterone sponges with either 350mg or 300mg for 12 days. At standing estrus, ewes were hand mated (three cycles). Progesterone (350mg) gave a better (P<0.05) estrus response (75%), compared to 300mg dose (42%). Ewes treated with 350mg P4 also showed better (P<0.05) synchronization response (93%) than those treated with 300mg (56%) at 72h after sponge removal. Lower doses of progesterone (300mg) significantly delayed (P<0.01) the onset of estrus. However, dose had no significant influence(P>0.05) on estrus length, conception rate and the proportion of ewes lambing at term. This study indicates that dose of progesterone may have an effect on estrus exhibition and response time without altering the conception rate and lambing in acycling crossbred Bharat Merino ewes during the major breeding season in a semi-arid tropical environment.