‘Environmental enrichment’ is often considered to improve captive animal welfare. However, some studies using male mice, Mus musculus, indicate that increasing cage complexity increases aggression. Limited evidence suggests that enrichment differs in its effects on behaviour and physiology between strains; but behaviour also differs between strains in non-enriched environments. Differences in enrichment type, evaluation methods, and strains used, have caused difficulty in interpreting the efficacy of environmental enrichment in improving welfare. Using enrichment suitable for commercial laboratories (nesting material and a Perspex tunnel), we compared within-cage behavioural and physiological responses among males of six strains housed in non-enriched standard polypropylene cages with those housed in ‘enriched’ cages. Outbred ICR(CD-l) and TO mice, and inbred BALB/c mice were more aggressive than C57BL/6, CBA/Ca and DBA/2 mice, which exhibited low levels of aggression typical of most inbred strains. Enrichment did not significantly affect aggression levels. Animals in enriched cages spent more time investigating the internal cage environment, eating and drinking, and in stereotypic behaviour patterns, although levels differed between strains. The greatest increase in stereotypy levels (bar-related stereotypies) with enrichment was found in DBA/2 mice. Higher testosterone levels were maintained over the study period in mice housed in enriched cages, and in more aggressive strains. IgG levels were also higher in mice housed in enriched cages, and in the outbred strains ICR(CD-l) and TO compared with inbred strains. The relationship between aggression, testosterone and ‘enrichment ‘ suggests that increasing complexity in laboratory cages may increase a naturally selected territorial response in some strains. The implications for strain-specific welfare are discussed.

In different areas of the world, strains of Echinococcus granulosus have been described which appear to vary in their infectivity, and laboratory primates have been used as indicators of their infectivity to man. This phenomenon was evaluated in Kenya for hydatid material of human, camel, cattle, sheep and goat orgin. Viable eggs, produced by experimental infections in dogs with larval material from all the above intermediate hosts, were fed separately to four baboons (Papio cynocephalus) in each case. Baboons were autopsied between 373 and 501 days following infection and the liver, lungs, heart, spleen and kidneys were thoroughly inspected. Hydatid cysts were recovered from two baboons in each of the camel, sheep and goat groups, three baboons in the cattle group and none of the baboons in the human group. Fertile cysts were found in the cattle and goat groups and it is suggested that the baboon could be used as an experimental model for this parasite.

The objective of the present study was to compare growth curves for live weight (LW) and body size of three strains of female dairy cattle reared under common environments in Ireland. One strain (HP) was selected from a predominantly North-American/European Holstein-Friesian genetic pool selected for high milk production. The second strain (HD) represented a predominantly North-American/European Holstein-Friesian genetic pool selected for high milk production but with greater selection emphasis on functional non-production traits. The third strain (NZ) consisted of New Zealand Holstein-Friesian females of high genetic merit for profitability in New Zealand. The data consisted of 99 animals (33 animals in each strain) with records on LW, length, girth and height from birth to a minimum of 594 days of age. The von Bertalanffy growth function was fitted to each animal's records separately and least-squares analyses were used to investigate the effect of strain on birth LW/body size, parameters of the growth function and average daily gains. Average mature live weight of the HD animals (591 kg) was significantly larger than that of the HP (566 kg) or NZ (543 kg) strain; the HD strain matured more slowly. The HD (134 cm) and HP (135 cm) strains were significantly taller than the NZ (128 cm) strain. Although the data set was relatively small there are indications that dairy females of North-American genetic origin were heavier at birth, grew faster, and were heavier and taller at maturity than dairy females of New Zealand origin.