Cow longevity and lifetime performance traits are good indicators of breeding effectiveness and animal welfare. They are also interrelated with the economics of dairy herd. Unfortunately, a high milk yield is often associated with deteriorated cow health and fertility and, consequently, with an increased culling rate. This situation, observed also in the Polish population of Holstein-Friesian cattle, inspired us to undertake a study on the associations between some factors and lifetime performance characteristics. The data set consisted of the records on 135 496 cows, including 131 526 of the Black and White strain (BW), and 3970 of the Red and White strain (RW) covered by performance recording and culled in 2012. It was found that cows of the BW strain and those from the largest herds (>100 cows) reached higher lifetime and mean daily energy-corrected milk (ECM) yields than cows of the RW strain and those from smaller herds culled at a similar age. Cows youngest at first calving (<2.0 years) were characterised by the highest lifetime ECM yield. It indicates that heifers can be bred even when they are younger than 15 to 16 months with no significant negative effect on their later performance. Infertility and reproduction problems (39.6%) and udder diseases (15.5%) constituted the most frequent reasons for cow culling. Cow longevity and lifetime productivity were considerably affected by the interactions between the studied factors.

Random regression models (RRM) have recently been used not only in the analysis of milk traits such as milk, fat and protein yield, but also somatic cell score (SCS), lactose yield and milk urea nitrogen (MUN), and very seldom they have been applied to analyze milk dry matter (DM) yield. RRM have many advantages over lactation models: 1) they account more accurately for environmental factors affecting the performance of cows in each day in milk (DIM) throughout the lactation, 2) they allow ABSTRACT: The objective of this research was to examine heritabilities and genetic, phenotypic and permanent environmental relationships between milk dry matter (DM) and milk traits such as milk, fat, protein and lactose yields, milk urea nitrogen (MUN) and somatic cell score (SCS) in extended (to 395 days) lactations of Holstein cows from a big farm in Poland. The data set consisted of 78 059 test day records from the first, second and third lactations of 3 792 cows, daughters of 210 sires and 1 677 dams. Single-or two-trait random regression models were used with fixed effects of calving year, calving month, dry period and calving interval and random additive genetic and permanent environmental effects. The last two fixed effects were not included in the analysis of first lactation data. The highest values of heritabilities for all traits, except DM, were observed in the second lactation. First lactation heritabilities for all traits -except milk yield and SCS -were smaller than those in the third lactation. Lactose yield was highly heritable, with average h 2 equal to 0.25, 0.29 and 0.28 in lactations 1, 2 and 3, respectively. Heritability for DM was slightly lower than that for lactose (0.22, 0.26 and 0.28 for lactations 1, 2 and 3, respectively). In all lactations heritabilities for SCS were below 0.1. Genetic correlations between DM and milk yield (0.64-0.74) were lower than those between MUN and milk yield (0.67-0.79) as well as between lactose and milk yield (0.72-0.82). In general, DM was much more closely correlated with fat or protein yield (0.55-0.79) than with MUN or lactose (0.38-0.76). Only in the third lactation the correlation between DM and protein (0.72) was lower than between lactose and protein (0.76). For all lactations there were very high genetic correlations between DM and lactose (0.96-0.98) and high correlations between ) and between lactose and MUN (0.70-0.85). The results suggest that further research is needed, focused on DM and its relationship with other traits in larger populations.

The studies were carried out on 614 animals slaughtered in winter and summer seasons. After slaughter and post-slaughter processing the carcasses were evaluated according to EUROP system. The meat pH and its colour were determined in m. longissimus thoracis after 48 hours of chilling. A significant effect of cattle category, season of slaughter and interactions between them on meat pH was found. High pH values were observed mainly in the summer season in the groups of young bulls (A) (6.1) and bulls (B) (6.07). Slightly lower values 5.94 and 5.65, respectively, were observed in both above-mentioned groups in winter. Meat collected from heifers was characterized by proper pH in both analysed seasons whereas meat obtained from cows had pH values above 5.8, independently of the season of slaughter. The differences in colour lightness L* observed among all analysed cattle categories were statistically highly significant (P &lt; 0.0001). The brightest red meat was obtained from heifers and the darkest from cows. The differences between young bulls and bulls in the same slaughter seasons were not large despite considerable variation in the age of slaughtered animals, especially in the summer season. Distinctly higher values of L* (brighter red meat) were found in the winter season in all cattle categories excluding meat from cows in which L* in summer was slightly higher than in winter. The differences in L* between seasons as well as the interaction of cattle category &times; slaughter season were statistically highly significant (P &lt; 0.0001). For the remaining colour parameters (a*, b*) higher values were also observed in winter compared to summer in all cattle categories. The highest values of a* and b* were found in bulls.

Seasonality in milk performance and reproduction was analysed in low-input mountain farms in the Czech Republic. Two different feeding regimes were distinguished: seasonal pasture and all-year silage feeding in confi nement. Seventeen pastured herds and sixteen confi ned herds of Czech Pied and Holstein breeds (total 12 158 cows) were included in the seven-year study. Seasonal variation of milk, fat and protein yields per lactation according to the month of calving was found in both groups of herds. The highest yields were achieved by autumn-calved, and the lowest yields, by summercalved cows (difference of 542 kg and 474 kg of milk on average in pastured and in confi ned herds, respectively). Higher individual daily yields (up to 2.9 kg on average) were recorded in the period between May and July than in the rest of a year. No effect of month of calving on days-to-fi rstservice and on days-open period was identifi ed.

Abstract. A study based on 150 carcasses of rabbit crosses of three breeds: Flemish Giant (FG), New Zealand White (NZW) and Californian (CAL) was conducted to determine the changes that occur within the first 24 h post mortem in the meat color parameters, i.e. lightness (L*), redness (a*), yellowness (b*), chroma (C*) and hue (H*), in the rabbits of different genetic groups and sexes. Four groups were formed: FN (FG bucks×NZW does); FC (FG bucks×CAL does); FN×C (FN bucks×CAL does); FN×FN (FN bucks×FN does). Meat colour was measured on the surface of Longissimus dorsi (LD) and biceps femoris (BF), 45 min and 24 h post mortem. The genetic groups differed significantly in the meat colour parameters of the LD and BF muscles at both times after slaughter. After 24 h, a* and b* values of the LD muscle were highest in FC group (18.05 and 6.65, respectively) and the lowest in FN×FN group (16.46 and 4.75, respectively). The greatest color difference (ΔE) of the LD muscle was in FN×FN rabbits (9.85) and the smallest in FC group (5.07). The differences between genetic group in color parameters of the BF muscle were smaller but significant, which indicates that crossbreeding may be used in practice to change meat color. Sex did not influence significantly the color parameters of the muscles at either time, although the a* and C* values of the BF muscle were higher in males than females.