Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 27

Liczba wyników na stronie
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników

Wyniki wyszukiwania

help Sortuj według:

help Ogranicz wyniki do:
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
Heritability and genetic correlations of monthly egg production under random regression models were estimated. Three layer lines (A22, A88, K66) in six consecutive generations were analysed. A22 (13,770 recorded hens) and A88 (13,950 recorded hens) are maternal lines of Rhode Island White birds selected on egg production and shell colour; K66 (9,351 recorded birds) is a paternal line of Rhode Island Red birds selected on egg weight. Eight models with different orders of Legendre polynomials were applied. Adequacy of the models was checked by the Akaike Information Criterion. According to the most adequate model including second order Legendre polynomials for fixed effects and third order for additive genetic and permanent environmental effects, relatively high heritabilities were estimated in the first (h²=0.3) and final (h² above 0.3) periods of production with a substantial decrease in heritability during the egg production peak. Methodology based on random regression animal models can be recommended for genetic evaluation of laying hens.
The objective of the study was to analyze effective population size and inbreeding level in populations of cat breeds registered in the Polish Studbook. The Association of Purebred Cat Breeders in Poland provided access to pedigrees of 26725 cats fromseven breeds. The most frequent breed was Persian, however increasing tendency in numbers of registered animals from other breeds was recorded in later years. Although the percentage of inbred individuals was increasing over time, mating of close relatives was avoided by most of the breeders, and the average inbreeding coefficient exceeded 5% only for Siberian and Russian breeds. Current analysis suggests that the Polish pedigree cat populations are not threatened by negative effects of inbreeding.
In a population of Rhode Island White hens heritability of egg formation, clutch characters and traditional selection traits as well as the genetic and phenotypic correlations between them were estimated via multitrait animal model. Over 1300 birds and about 4000 birds were recorded in two consecutive generations for oviposition time and traditional traits, respectively. The heritability estimates obtained for age at first egg (h2=0.42), egg weight (h2=0.50) and body weight (h2=0.42) were considerably higher than those for initial egg production (h2=0.22), clutch traits (h2 between 0.11 and 0.23) and oviposition time (h2 between 0.13 and 0.19). Both genetic and phenotypic correlations between clutch traits and traditional selection traits were low, except for initial egg production and maximal clutch length (rg=0.40 and rp=0.38). As expected, negative correlations were registered for number of clutches and average clutch length. It indicates an opportunity of selection aimed at improvement of egg production persistence by an increase in the average clutch size. Oviposition time was favourably correlated with traditional selection criteria.
Relationships were estimated between longevity, culling reasons and yield of milk and milk components in the I, II and III 305-day lactations and lifetime dairy performance. ANOVA with Duncan test was applied. Cows culled for health problems showed the highest lifetime dairy performance; those kept in the herd for a short of time were culled because of hard milking and behavioural problems or were sold for breeding.
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.