Dispersion parameters for the number of piglets born alive were estimated using a repeatability and random regression model. Six sow breeds/lines were included in the analysis: Swedish Landrace, Large White and both crossbred lines between them, German Landrace and their cross with Large White. Fixed part of the model included sow genotype, mating season as month-year interaction, parity and weaning to conception interval as class effects. The age at farrowing was modelled as a quadratic regression nested within parity. The previous lactation length was fitted as a linear regression. Random regressions for parity on Legendre polynomials were included for direct additive genetic, permanent environmental, and common litter environmental effects. Orthogonal Legendre polynomials from the linear to the cubic power were fitted. In the repeatability model estimate of heritability was 0.07, permanent environmental effect as ratio was 0.04, and common litter environmental effect as ratio was 0.01. Estimates of genetic parameters with the random regression model were generally higher than in the repeatability model, except for the common litter environmental effect. Estimates of heritability ranged from 0.06 to 0.10. Permanent environmental effect as a ratio increased along a trajectory from 0.03 to 0.11. Magnitudes of common litter effect were small (around 0.01). The eigenvalues of covariance functions showed that between 7 and 8 % of genetic variability was explained by individual genetic curves of sows. This proportion was mainly covered by linear and quadratic coefficients. Results suggest that the random regression model could be used for genetic analysis of litter size.

The aim of the study was to assess the effect of subacute treatment with a low dose of atrazine (1,3,5-triazine-2,4-diamine, 6-chloro-N-ethyl-N-(1-methylethyl), an s-triazine herbicide, on endocrine oestrus regulation in gilts. A group of nine gilts (F generation of Swedish Landrace × Large Yorkshire) were treated with 1 mg atrazine/kg body mass daily, mixed to the feed for 19 days before the onset of expected oestrus. Blood samples were obtained by cranial vena cava puncture three times daily at 3-h intervals on five post-treatment days, i.e. before and during oestrus. The serum concentration of oestradiol-17> (E ) was determined by the fluoroimmunochemical method. On Day 2 before the onset of expected oestrus, a significantly lower (P < 0.001) E concentration was measured in the serum of treated gilts (31.25 ± 1.95 and 39.32 ± 1.38 pg/mL) than in the control pigs (51.43 ± 1.29 and 68.59 ± 2.99 pg/mL). In contrast, the E concentration measured in the serum of treated animals was significantly higher (P < 0.001) on the day of the expected onset of oestrus and on the subsequent two days (35.43 ± 1.85, 53.92 ± 1.98 and 60.32 ± 2.35 pg/mL, respectively) than in the control animals (13.52 ± 1.79, 21.53 ± 1.35 and 20.05 ± 1.46 pg/mL, respectively). Insufficient serum E concentration of the treated gilts resulted in a failure of expected oestrus, as indicated also by the state of dioestrus demonstrated by histopathological examination of the uterus.

This research is focused on the genetic diversity and population structure of the Black Slavonian pig, with the aim of assessing the situation regarding the endangerment of genetic diversity, and defining the further role of this breed in the preseration of its genetic diversity. Genetic population parameters were assessed in 42 animals at 8 microsatellite loci. On three of the observed loci there was a deviation from the Hardy-Weinberg (HW) equilibrium with P<0.01, one locus showed P<0.05, and in all of them the stated deviation resulted from a deficiency of heterozygous animals. The entire population's deviation from the HW equilibrium, with _ 2=92.8, Df=16, and P<0.0001 was also significant. Average PIC value for all 8 loci was 0.368. The average number of detected allelic variants was 2.50, with a standard deviation of 0.76 alleles. Such a small number of detected allelic variants, as well as the significant deviation from the HW equilibrium in four loci caused by a deficiency of heterozygotes, can be taken as one of the indicators of the reduced genetic diversity of the breed