Enrichment in laboratory mice: its effects upon reproductive physiology.

PONZIO M.F; LUQUE EM; RUIZ R.D,; FIOL DE CUNEO M; MARTINI AC,

Montreal

Congreso; 8th World Congress on Alternatives & Animal Use in the Life Sciences; 2011

Although a growing body of evidence indicates that environmental enrichment (EE) facilitates normal development and behaviour in laboratory mice, few studies were conducted to demonstrate its impact upon male and female reproductive physiology. Our study investigated the effects of EE on the development and reproductive success of Albino swiss mice, using PVC tubular devices and shredded paper as physical enrichment. Animals were allocated in regular housing cages in groups of five individuals and treated as non-enriched (control, C) or enriched from weaning to adulthood (E). To evaluate the EE effects upon pups development, a third group of females were enriched from the time the male was introduced to achieve pregnancy (EP). In males, evaluated parameters were body, testicular and accessory glands weight, sperm functional activity (motility, viability, acrosome and membrane integrity), testosterone concentration, in vivo fertilization rates, litter size and embryo degeneration percentages. In females, evaluated parameters included body, uterine and ovary weight, spontaneous ovulation, estradiol concentration, in vivo fertilization rates, litter size, pups neurobiological (cliff avoidance, negative geotaxis, surface righting reflex), physical (body weight at d 1, 7, 14 and 21, bilateral pinna detachment, low incisor eruption and eyes opening) and reproductive development (testicular descent, balano-prepucial opening and vaginal opening). No differences were evident in any of the parameters reflecting the basic reproductive physiology of males or females. However, a significantly higher number of pups were born from enriched mothers (C: 9.5±0.6, n=4; E: 10.7±0.2, n=5; EP: 12.2±0.7, n=5; p=0.03). A strong tendency was detected towards a faster development of the physical and reproductive parameters of pups born from both enriched groups, yet significant differences were only observed for testicular descent (day 19, C: 0±0%, n=16; E: 62.5±12.5%, n=17; EP: 21.6±9.7%, n=21; p=0.002). Although EE showed limited effects in this strain of laboratory mice reproductive physiology, a faster pups development appears to be favored by an increased physical complexity in the environment from birth.