Project Objectives

• Compare the efficacy of four breeding schemes for dystrophic mice: Permanent Trios (PT), Time‑mated Trios with Grouping of Pregnant Females (TT‑GP), Time‑mated Trios with Foster Females (TT‑PF), and Group Mating with Grouping of Pregnant Females (GM‑GP).
• Quantify key breeding outcomes, including the number of pups born (alive/dead), survival to weaning, and weekly pup growth.
• Determine how social, environmental and maternal‑care factors influence pup mortality and maternal stress.
• Identify the scheme(s) that optimise survival, welfare and the production of homogeneous experimental cohorts.
• Produce evidence‑based recommendations for facilities maintaining dystrophic and other fragile mouse strains.

How This Advances 3Rs Implementation

• Provides validated, humane breeding strategies that improve welfare of both male and female mice.
• Enables institutions to reduce total animal use while maintaining experimental output.
• Offers refinements that reduce stress, improve maternal behaviour, and minimise perinatal mortality.
• Supports harmonised breeding practices across Duchenne muscular dystrophy (DMD) and myopathy research communities.
• Facilitates production of synchronized cohorts, reducing repeated or failed experiments.
• Generates broadly applicable guidance for breeding fragile or high‑risk mouse lines.

Background

Duchenne muscular dystrophy (DMD) is a severe genetic disorder causing progressive muscle degeneration and early mortality. Preclinical research depends heavily on dystrophic mouse models such as mdx and mdx 5Cv, but these strains are notoriously difficult to breed. Challenges include male subfertility, female anxiety, poor maternal behaviour and increased nutritional demands. These issues lead to high pup mortality, inconsistent litter sizes and the need to breed excess animals to ensure adequate experimental cohorts.

Over the past two decades, the research team has used several alternative breeding schemes that appear more effective than the conventional permanent trio approach (i.e. one male housed with 2 females). However, preliminary observations also indicate that breeding outcomes, including number of pups born, survival to weaning, and pup growth, vary substantially between schemes, suggesting that refinements may dramatically reduce unnecessary breeding and improve animal welfare. This project systematically evaluates four breeding strategies, generating evidence-based guidance for laboratories working with dystrophic mouse lines and potentially other myopathy models.