No abstract

In studies of chromosome instability, the sister chromatid exchange (SCE) test is a particularly sensitive cytogenetic assay for detecting DNA damage. SCE tests of chromosome instability were performed in the group of 6 horse breeds (Pure-bred Arabian, Malapolski horse, Polish noble half-bred, Polish cold-blooded, Hucul and Polish Konik). The chromosome preparations were obtained from our in vitro culture of peripheral blood lymphocytes stained using the FPG technique. The mean number of SCEs/cell in the analysed population of horses was 5.14±1.44. The mean frequency of SCEs in the 6 analysed horse breeds varied depending on the breed. Statistically significant differences were observed between the horse breeds (P<0.01).No statistically significant differences in the number of SCEs per cell were found between the males and females (5.10±1.34 and 5.20±1.52, respectively). The horses were also assessed for the number of SCEs/cell in relation to the age of the animals. The differences between the age groups were statistically significant (P<0.01).

A significant factor in improving the performance of dairy cows is their physiological ability to correct a negative energy balance (NEB). This study, using Simmental (SIM) and Holstein-Friesian (HF) cows, aimed to assess changes in NEB (non-esterified fatty acid; body condition score; and C16:0, C18:0, and C18:1) and its effect on the metabolic efficiency of the liver (β-hydroxybutyrate and urea). The effects of NEB on daily yield, production at peak lactation and its duration, and changes in selected milk components were assessed during complete lactation. Up to peak lactation, the loss of the body condition score was similar in both breeds. Subsequently, SIM cows more efficiently restored their BCS. HF cows reached peak lactation faster and with a higher milk yield, but they were less able to correct NEB. During lactation, their non-esterified fatty acid, β-hydroxybutyrate, C16:0, C18:0, C18:1, and urea levels were persistently higher, which may indicate less efficient liver function during NEB. The dynamics of NEB were linked to levels of leptin, which has anorectic effects. Its content was usually higher in HF cows and during intensive lactogenesis. An effective response to NEB may be exploited to improve the production and nutritional properties of milk. In the long term, it may extend dairy cows’ productive life and increase lifetime yield.

Abstract. The study covered 11 376 horses registered in the six successive volumes of the Wielkopolski Herdbook. The level of variability in the body conformation indices and in the performance value indices was analysed. The genetic basis parameters for the body conformation and performance traits of the Wielkopolski horses were assessed. A high level of heritability was identified for the wither height (h2 = 0.566) and cannon circumference (h2 = 0.418), with an average heritability level of the other analysed characteristics (ranging from h2 = 0.205 – for the stallion performance test results to h2 = 0.350 – in the case of chest circumference). On the other hand, genetic correlation between the analysed indices produced the highest values for the relationship between wither height and cannon (rG = 0.636) and chest (rG = 0.551) circumference, as well as for the interrelation between the above dimensions and the following body structure indices: »boniness« (rG = 0.690) and »bulkiness« (rG = 0.541). Considering the extensive scope of the study – and the fact that the breed population was registered in the Wielkopolski Herdbook – the authors suggested the advisability of using the results of the present study for the modification of breeding programs with a view to improve the breed in question, both its principal population and the one included in the program of gene-pool protection.