MSCAGR (Animal Science) / Department of Animal Science / The use of in vitro culture media and assisted hatching techniques remain a challenging obstacle to hatching of blastocyst-stage embryos. Mechanical, chemical, enzymatic thinning and laser assisted techniques have been used previously, but there is still a lack of information on its application and implication in livestock. The aim of this study was to compare the effect of two in vitro culture media ((Ham’s F10 and Tissue Culture Medium 199 (TCM-199)) and four assisted hatching techniques (mechanical, chemical, enzymatic and laser) on blastocyst formation and hatching rate using murine embryos as a model. The C57BL/6 and BALB/c mouse breeds were bred and raised until they reach maturity and then bred naturally to produce a hybrid F1 generation. The light in the breeder house was controlled at 14 hours light and 10 hours darkness. Feed and water were provided ad libitum for the mice. Mature female mice were super-ovulated using equine chorionic gonadotropin (eCG) and human chorionic gonadotropin (hCG). A total of 400 blastocysts were collected from the F1 generation and these were allocated equally for the four assisted hatching techniques (laser, mechanical, chemical and enzymatic) as well as a non-treated control group. The blastocysts were paired into a group of 10 and replicated 4-four times for each assisted hatching techniques and control group. The embryos were then cultured for 24 hours and the hatching of the embryos were observed. Hatched embryos were stained for blastomere counting. The general linear model (GLM) of statistical analysis software (SAS) version 9.4 was used to analyze the data. Assisted hatching techniques (laser, mechanical, enzymatic and chemical) yielded 46.86±37.12; 51.07±40.19; 39.05±35.83 and 33.32±37.50% of hatching, respectively under in vitro culture in Ham’s F10. There was a significant difference (p<0.05) observed between assisted hatching techniques using Ham’s F10 as culture medium. In the TCM-199, laser, mechanical, enzymatic and chemical assisted hatching techniques yielded 56.25±43.30; 52.55±35.50; 49.16±37.50 and 33.85±35.50%, respectively, with significant differences (p<0.05). However, the hatching rate of embryos for all techniques was higher when in vitro cultured in TCM-199 compared to those cultured in Ham’s F10, and statistically higher than the control group. In conclusion, laser assisted hatching technique is the best of the techniques to use to assist the hatching of murine embryos and TCM-199 is the best of the two in vitro culture media for the hatching percentage.

An island subspecies endemic to the remote St Kilda archipelago, Apodemus sylvaticus hirtensis is considered of national importance but has been little studied, despite its inclusion in the criteria for the islands’ designation as a World Heritage Site. This study expands our knowledge of the core ecology of the mice; distribution, morphology, age structure, breeding phenology, population density, range size, survival and fecundity are all described and quantified using data collected from 4462 captures of 787 individuals between 2009-2012 on three sites (Carn Mor, Glen Bay & Village Bay), 1-2km apart on the main island of Hirta. Morphological analysis confirmed the reputed gigantism the mice, with maximum body weights of 60g for males and 50.5g for a non-gravid female both being approximately double that of a mainland specimen (the heaviest gravid female caught weighed 56g). Sexual dimorphism was evident, with males >1 year old being 8.7% heavier than females on average. Significant geographical variation in size was also found; mice on the seabird breeding colony of Carn Mor were heavier, longer and in better condition than mice elsewhere. Mice were observed to have a well-defined breeding season between April and September, shorter than on the mainland, with most individuals not breeding until their second year and very few surviving two winters. No geographical differences were found in the proportion of adult mice more than a year old that were in breeding condition at any given time, although there were significant geographical differences in the proportion of individuals in breeding condition for ‘young adult’ mice entering their first spring and sub adult mice in the autumn of the year in which they were. Spatially explicit capture-recapture (SECR) methods were used to quantify population densities free from ad hoc methods of trapping area estimation. Temporal variation in population size typical of temperate small mammals was found, with densities as low as 2 mice/ha in spring, increasing through summer and autumn with juvenile recruitment until reaching a peak at the beginning of winter of up to 50 mice/ha. Geographical variation was again observed, with frequent significant differences between trapping sites and an overall trend of highest population densities on the seabird breeding site. Mean individual range sizes varied between 0.3-3.0ha and were largest in Village Bay and in males in breeding condition. Pradel robust design recruitment models were used to quantify monthly survival (0.67-1.00) and fecundity (0.03- 0.41) and overall rate of population change (0.81-1.52) between sessions. Survival varied little between grids outside of the breeding season, but tended to be greater in Carn Mor than Village Bay during the summer. Fecundity rates varied little between years and grids, with one exception where increased summer fecundity followed a severe winter decline on Carn Mor. The possible role of differences in the quality of the food supply (in particular the seabird breeding colony and spatial variation in sheep grazing pressure) on creating geographical variation in body size, condition, breeding phenology, density and population dynamics are discussed in detail, as is the overall pattern of insular traits found in the mice.