A test for linkage of the loci for dominant white and barring with loci controlling growth rate in the fowl 1

Females from a coloured inbred line of Leghorns (ii) were mated to three groups of males heterozygous for the dominant white gene (Ii). The parents transmitting the I gene to the three groups of males were respectively larger, smaller and of the same size as the parents transmitting the i gene. No differences were observed between the three types of crosses in the effect of colour genotype on body weight, providing no evidence for linkage between the dominant white locus and loci affecting body weight.

When comparisons were made between the colour genotype classes, pooled within full sib groups, the coloured genotype was larger in ten of the twelve test cross‐sex‐hatch combinations. Two of these differences, were statistically significant, but when the data were pooled over hatch, sex and test cross, no significant difference was found. The data thus offer meagre support for weight differences in favour of the coloured genotype, but the negative evidence of the pooled analysis raises considerable doubt that real differences in weights between the colour classes exist in these populations.

A similar comparison was made between the barred and non‐barred genotypes among the coloured female progeny in one test cross. The barred progeny were heavier in each hatch, in spite of the fact that the barring gene and sex chromosome were derived from the smaller grandparent. The differences were not statistically significant in either hatch or when the mean squares were pooled over hatches. It is concluded, therefore, that this experiment provides no evidence for any association between the barring locus and the genes for growth rate in this population.     

Comparison of two thiopental infusion rates for the induction of anaesthesia in dogs

OBJECTIVE: To compare the induction dose requirements of thiopental using two different infusion rates for induction of anaesthesia in dogs. STUDY DESIGN: Prospective, randomized study. ANIMALS: Fifty, healthy (ASA I or II) client-owned dogs with a mean age of 4.1 years and a mean mass of 20.4 kg undergoing elective surgery. MATERIALS AND METHODS: Animals were randomly assigned to receive an infusion of 2.5% thiopental at a rate of either 0.1 ml kg(-1) minute(-1) or 0.4 ml kg(-1)minute(-1), 30-40 minutes after pre-anaesthetic medication with intramuscular acepromazine (0.025 mg kg(-1)) and pethidine (3.5 mg kg(-1)). Thiopental administration was controlled by a precision syringe driver. Statistical analyses of the results, using the outcome 'mg kg(-1) required for induction' (log-transformed) included unpaired t-tests for all categorical data (thiopental infusion rate, breed, sex, obesity, sedation quality) and univariable linear regression for continuous variables (mass, age). All variables were then considered in a multivariable linear regression model. The quality of induction with the two different infusion rates was also assessed. RESULTS: After controlling for quality of sedation, the thiopental induction dose requirement was significantly less (p < 0.001) with the slower infusion rate (median = 7.5 mg kg(-1); range 4.9-13.7) compared with the faster infusion rate (median =11.0 mg kg(-1); range 6.6-18.0). The quality of sedation also affected the dose required (p = 0.03). The slower infusion rate was associated with a significantly poorer induction quality (p = 0.03) [corrected] CONCLUSIONS: Slow thiopental infusion (0.1 ml kg(-1) minute(-1)) for anaesthesia induction after acepromazine/pethidine pre-anaesthetic medication reduced the induction dose requirement, although the quality of induction was inferior. CLINICAL RELEVANCE: The induction dose of thiopental was reduced with a slower administration rate and so slow administration is recommended in thiopental-sensitive animals.     

Does occasional movement make pecking devices more attractive to domestic chicks?

1. Previous studies have shown that a bunch of string is a particularly attractive pecking stimulus for chicks and adult laying hens. Because movement is thought to be an important attribute of enrichment objects, this study determined whether occasional movement would affect the attractiveness of this device. 2. In experiment 1 the responses of pair-housed chicks to string were compared when devices in adjacent cages were either linked (so that pecking or pulling at the string in one cage moved the adjoining one) or not (separate). In experiment 2 the devices in half the cages were jigged remotely by the experimenter whereas the others remained static. In both cases, the string devices were introduced into the cages for 10 min on each of 5 consecutive days. 3. No treatment effects were apparent in experiment 1 when pooled data was analysed but comparison of responses on days 1 and 5 revealed that only the chicks presented with non-linked devices showed increased interest with repeated exposure. 4. Chicks given static devices in experiment 2 pecked sooner, more often and longer at them than did those exposed to similar ones that were jigged regularly by the experimenter. Jigged devices attracted slightly more pecking with repeated exposure, which may have reflected familiarity-induced fear-reduction, but chick responses showed no apparent changes from day 2 onwards. Conversely, rather than showing habituation, the chicks pecked progressively more at the static devices with repeated presentation. 5. The present results show that chicks pecked readily at bunches of white string, thus confirming its attractive properties but that static devices were more attractive than those incorporating occasional movement. These and previous findings are discussed in terms of their implications for the development of effective environmental enrichment.