Investigating individual learning behaviour of dogs during a yes/no detection task.

Detection dogs are frequently tested for their ability to detect a variety of targets. It is crucial to comprehend the processes for odour learning and the consequences of training on an expanding set of target scents on performance. To properly evaluate their ability to identify the target, the only true measure is the dogs' initial response to novel sources, since this excludes learning effects. In this study, we evaluated the individual learning processes of three detection dogs that were pre-trained to differentially respond to a faecal sample of a mare in oestrus (S+) and a faecal sample of the same mare in di-oestrus (S-). After reaching criterion during a test with known training samples, the dogs were tested for generalization to a novel source. Average responses to S+ and S- were calculated as a function of presentation sequence, and Signal Detection Theory was used to further analyse characteristic differences in learning. The results of this study suggest that the ability of individual scent detection dogs to learn within an olfactory discrimination test varies considerably. The information obtained in this study could be helpful for mitigation training. We show that through careful monitoring of individual learning processes, the strategy each dog followed becomes apparent: especially the observations on the dogs' responses to first encounters with novel sample sources. This provides us with more detailed information than the more traditional sensitivity and specificity measures and allows us to better predict the dog's capabilities.

Clinical and pathological findings in a HERDA-affected foal for 1.5 years of life.

A Quarter horse filly bred from two horses affected with HERDA (hereditary equine regional dermal asthenia) was observed clinically and its skin histologically for the 1.5 years of its life. Severe signs of the disease did not manifest until 1.5 years of age, and were not temporally related to saddling. Histological comparison to an age-, breed- and sex-matched control did not show any consistent diagnostic features. Monitoring of the proband substantiated previous reports of (i) the autosomal recessive nature of the disease, (ii) mares affected with HERDA being able to foal without damage to the skin or reproductive tract, (iii) HERDA foals appearing phenotypically normal throughout the first year of life, and (iv) demonstrated that histological interpretation of skin specimens from grossly normal skin may be insufficient to differentiate HERDA-affected horses from controls.

Step-wise dilution for removal of glycerol from fresh and cryopreserved equine spermatozoa.

Osmotic stress is an important component of the damage to spermatozoa during cryopreservation. Osmotic injury, due to hyperosmolar freezing extenders, changes in relative solute concentration in the extra cellular medium during freezing and differences in the relative permeabilities of penetrating cryoprotectants, such as glycerol, and water occur when cryopreserved spermatozoa are diluted into isosmotic media or when spermatozoa are placed in the female reproductive tract. The purpose of the study reported here was to evaluate the effect of step-wise dilution for the removal of the permeating cryoprotectant, glycerol, from both fresh and cryopreserved equine spermatozoa on their motility and viability. There were significant (P < 0.05) effects of osmolality and dilution method on both total and progressive motility as well as viability in fresh spermatozoa. With the rapid, one-step dilution being significantly more detrimental to viability and motility, compared to the fixed molarity and fixed volume-dilutions. With frozen-thawed spermatozoa there were significant effects of stallion on total and progressive motility of spermatozoa after cryopreservation and thawing; however, treatment (type of dilution after thawing) did not affect post-thaw motility. These data indicate that rapid, single-step removal of glycerol from fresh equine spermatozoa results in a post-hyperosmotic stress that is characterized by a reduction in both motility and membrane integrity. This post-hyperosmotic stress can be reduced by a step-wise dilution for removal of glycerol, which improved the maintenance of both motility and membrane integrity. However a similar benefit for step-wise dilution for removal of glycerol was not observed in cryopreserved equine spermatozoa.