Genetic evaluation of laying performance in the Zatorska goose: contribution to the conservation programme.

1. The aim of the study was to estimate the heritability of the laying performance in the cumulative and partial production of eggs and predict the breeding values of native Zatorska geese in a conservation programme using Best Linear Unbiased Prediction (BLUP) methodology. Second, the trajectory of the egg production curve was examined. 2. The data contain information about the laying performance of 1831 individuals in the first year of laying. To describe the trajectory of the laying performance, 10 mathematical models were tested. For the genetic parameter estimation of egg production, data from 1038 birds were used with a production higher than 20 eggs during the first season of laying. 3. The analysis of egg production was based on single and multi-trait models. Heritability, genetic and phenotypic correlations between phases of the laying performance as well as breeding values were estimated. 4. The best adaptation to the goose egg laying curve was the Ali and Schaeffer model. The estimates of heritability were 0.20 (0.06 SE) using the single-trait model and ranged from 0.12 to 0.24 using the multi-trait model. 5. The results suggest that the BLUP method can support the conservation programme.

Sex steroids level in blood plasma and ovarian follicles of the chimeric chicken.

The study was performed to determine the hormonal status of mature germline chimeras obtained by blastodermal cell transfer from chicken embryos of a donor breed [Green-legged Partridgelike breed (GP) x Araucana (AR)] to those of a recipient breed [White Leghorn (WL)] being at the same stage of embryonic development. The egg-laying chimeras and WL hens (control) of the same age were used in the experiment. At first, blood samples were taken from each bird at 0.5, 5, 12.5 and 18.5 h following oviposition. Subsequently, the chimeras and the WL hens were decapitated 1-2 h after ovulation. A stroma and the following follicles were isolated from the ovary: white normal (1-4, 4-6 and 6-8 mm), white atretic and yellow preovulatory follicles (F4-F1). Sex hormones, progesterone (P4), testosterone (T) and oestradiol (E2) in blood plasma and ovarian follicles were determined radioimmunologically. The activity of the 3beta-hydroxysteroid dehydrogenase (3beta-HSD) in the granulosa and theca layers of the follicles was analysed histochemically. In chimeric chickens, a higher level of T in blood plasma during the ovulatory cycle was noticed. However, in the stroma, white prehierarchical and medium-size preovulatory ovarian follicles the level of T was significantly lower. With respect to E2, its elevated levels were found both in blood and in the ovarian follicles. There were no significant differences in P4 concentrations in blood plasma while in ovarian follicles a higher level was observed only in white 6-8 mm follicles. 3beta-HSD activity in granulosa and theca layers of the ovarian follicles in chimeras was not different from that in the WL hens. In conclusion, the results obtained indicate that germline chimeras exhibit significant alterations in sex hormone levels in the ovary and blood plasma, which in turn may affect their reproductive abilities.

Effects of fenfluramine on body weight, feed intake, and reproductive activities of broiler breeder hens.

Inherited overfeeding and fattiness reduce laying performance in broiler breeder pullets. Although feed restriction is used to compensate for overeating and weight gain, this management practice leads to increases in BW variation, labor cost, and bird stress. Dietary supplementation of anorectic agents, such as fenfluramine, may be an alternative. Anak female prebreeder hens (19 wk of age; n = 10 per group) were treated as follows: daily oral administration of 5, 10, 20, or 40 mg DL-fenfluramine/kg BW or saline with food provided for ad libitum intake or administration of saline and feed restriction. Daily feed intake (FI), laying rate, egg composition, and BW were measured. At 40 wk of age, adipose tissue and ovary weights were measured. Fenfluramine depressed (P < 0.05) BW and FI in a dose-dependent manner, but was less effective in reducing BW than feed restriction. Suppression of FI occurred in two phases: a dynamic phase, coinciding with the rapid growth phase, during which FI declined progressively and a static phase during which FI reached a plateau at a significantly low level until the end of the experimental period. Egg production peaked first in saline-treated hens fed for ad libitum intake, but soon after started to decline. In all fenfluramine-treated and feed-restricted hens, egg production peaked 3 to 4 wk later and remained high until the end of the experiment. There were no differences in egg and egg component weights among the experimental groups. Abdominal adipose tissue weight was reduced by fenfluramine in a dose-related manner, and its weight in the group treated with the highest dose was similar to that of feed-restricted hens. In these two groups, ovarian weight was significantly higher than in the saline-treated hens fed for ad libitum intake, and a small, nonsignificant increase in ovary size was observed in groups treated with the two median doses of fenfluramine. The effect of fenfluramine on egg production was similar to that of feed restriction, but it was not dose-dependent and, thus, not directly related to its leaning effect. In broiler breeder hens, oral fenfluramine may be used for chemical feed restriction and diminution of fattiness without reducing egg production relative to manually feed-restricted hens.