2. Selection indexes designed to maximise income over food costs (IOFC) were used to evaluate the usefulness of food consumption data for the genetic improvement of laying flocks.
3. Given reliable estimates correlating food consumption to egg mass, body weights and age at first egg it is possible to construct highly efficient selection indexes for genetic improvement of IOFC without the direct use of food consumption data.
4. Selection for genetic gains in egg mass appears to be the most important factor for genetic improvement of IOFC. Correlated increases in egg weight were observed for two of the populations.
5. Body weights showed very small and inconsistent genetic responses under index selection suggesting that a reduction in body weight need not be necessary for more efficient egg production.
6. Indexes which showed greatest genetic improvement also resulted in an increase of food consumption. Thus genetic efficiency in egg laying flocks would be achieved by increasing egg mass through earlier sexual maturity, larger eggs and higher production rates with increased food consumption and only slight, if any, reduction in body size.
7. Estimates of heritabilities and genetic correlations indicate that food consumption measurements can be based on partial records; high heritabilities were found for egg mass and food consumption measurements in both early (20 to 40 weeks) as well as late (40 to 60 weeks) production periods. 相似文献
2. Heritabilities of 0.39, 0.19 and 0.20 were found for IFC, FCR and FSC, respectively.
3. Genetic correlations of ?0.61, 0.15 and 0.06 were found between IFC and FCR, IFC and FSC, FCR and FSC, respectively.
4. A positive, that is unfavourable, correlated selection response for FSC was observed in both selection lines. 相似文献
2. Plasma VLDL concentrations were consistently higher at all ages in fat line hens but were not affected by dietary treatment.
3. Mature body weight did not differ between the lines in birds fed ad libitum but with food restriction throughout life, fat line birds were lighter at 34 weeks.
4. There was little difference between the lines in abdominal fatness of birds fed ad libitum up to 60 weeks. Fat line birds were always fatter than lean line counterparts under food restriction.
5. Egg production was higher in lean line birds fed ad libitum but food restriction improved egg production in both lines. Peak egg productions were similar in both lines but there was evidence that the optimal food allowances for egg production was higher in the lean compared with the fat line.
6. Ovarian yellow follicle numbers were highest at 34 weeks in ad libitum fed lean line birds and declined linearly with decreasing body weight caused by food restriction but there was no such relationship in fat line birds.
7. White follicle numbers were higher and follicular atresia was lower in the lean line.
8. It is concluded that poor reproduction in fat line birds was associated with inhibition of follicular development and atresia rather than by high plasma VLDL concentrations promoting excessive yolk formation. 相似文献
2. Differences in the 4 genotypes, additive direct and maternal crossbreeding effects and heterosis were estimated on the following traits: age at first egg, egg production to the ages of 30, 35, 40 and 52 weeks of age, egg weight at 30 weeks of age, and (egg) fertility by artificial insemination with Muscovy drakes’ pooled semen.
3. Egg production up to 52 weeks of age was higher in Ts than in Pk (respectively 214 ± 7 and 150 ± 8 eggs), but not statistically different from that of the reciprocal crossbreds. The ratio of settable eggs to total eggs was nearly 90%, without any difference between genotypes.
4. Average egg weight at the age of 30 weeks was 75 ± 0.9 g for Pk, which was higher than the corresponding values for Ts (62 ± 0.8 g), but not significantly different from the crossbreds.
5. An effect of genotype was found on egg fertility: the Pk strain exhibited the lowest value, 71.3 ±3.1% compared with 75.9 ±2.1% for Ts, 80.6 ± 2.6% for Ts × Pk and 74.6 ± 1.9% for Pk × Ts.
6. Crossbreeding genetic variables showed favourable direct genetic effects for egg production and (egg) fertility in Ts, while Pk had favourable direct genetic effects on egg weight. The Pk genotype had a favourable maternal effect on fertility. Direct heterosis was 34% and 10% for egg production up to 30 and 52 weeks of age respectively, 8.8% for egg weight and 5.4% for (egg) fertility.
7. Crossing Ts with Pk seems profitable for the production of mule ducklings. 相似文献
2. Egg production, egg weight and food consumption were recorded on 1200 hens in every generation. Parent females were selected on individual performance. Males were not recorded and selected at random within half sib families to minimise rate of inbreeding.
3. A linear selection response of 0.46 and 0.43 monetary units per generation was observed, which resulted in a total response of 19.8% and 18.2% of the phenotypic mean of the base population over the 5 generations. A large increase in egg weight was the most important reason for the selection response in income minus food cost.
4. Further changes in associated traits were: an increase in egg number and egg mass, and a decrease in age at first egg, body weight and food: egg mass ratio.
5. The direct and correlated selection responses were similar in both lines. The realised response was somewhat less than expected in both lines.
6. A summary of phenotypic and genetic parameters, estimated from the data, is given. All genetic correlations between income minus food cost and the associated traits analysed, were in a favourable direction. 相似文献
2. Over the first 10 generations with selection almost exclusively for number of eggs to the age of 273 d, all traits, except rate of mortality, showed significant changes. Regressions per year were: 273 d production, 3.07 eggs; 497 d production, 5.18 eggs; production from 274 to 497 d, 2.43 eggs; age at first egg, ‐2.33 d; mean weight of first 10 eggs, ‐0.82 g; body weight at 497 d, ‐19.02 g and rate of mortality, 0.19%.
3. Over the rest of the period increasing selection pressure for egg weight has been applied. This resulted in positive changes for this trait and no or small negative changes in egg number.
4. In general, heritabilities and genetic correlations did not change over the period of selection. The heritability of the main trait of selection, production to 273 d was 0.19 ± 0.04 and heritabilities of egg size traits about 0.50.
5. The genetic correlation between egg production to 273 d and mean weight of first 10 eggs was estimated as ‐0.37 ± 0.06 but from the observed response a realised genetic correlation of ‐0.97 was calculated. 相似文献
2. Body weight gain, age at 50% egg production, mortality, hen‐day egg production and food conversion values showed significant improvement with proportionate increase in cage space per layer.
3. Egg weight gradually increased with age but shell thickness was influenced neither by age of the hen nor by stocking density.
4. Yolk index and colour were superior in the lowest stocking density (more cage space) group; other egg quality traits and egg weight were not influenced by stocking density.
5. The albumen index, internal quality unit, yolk index and yolk colour values increased with age. 相似文献
(i) The heritability of weight gain declined sharply with age over consecutive periods after 12 weeks. The genetic correlation of body weight at 12 weeks with gain in subsequent periods was low. There appeared to be sufficient genetic variance in growth rate in these later periods to alter the growth curve substantially by selection. For example, it should be possible to breed strains with a rapid early growth and low mature body size.
(ii) There was evidence of genetic variation in the change of egg weight with time. The genetic variation was, however, so low that in any selection programme to improve 28‐week egg weight without changing 44‐week egg weight the progress would be very slow.
(iii) Body weight at 12 weeks was genetically negatively correlated with sexual maturity. Its correlation with production in the first 44 weeks was positive in both strains, but not significantly different from zero.
(iv) Body weights after 28 weeks were apparently uncorrelated with egg production or sexual maturity.
(v) Egg weight and production traits show considerable heterogeneity of variance between years, probably partly due to their distribution not being normal.
(vi) The pattern of genetic variation appeared to differ significantly between the two strains so that correlated responses would not necessarily be the same.
(vii) There was a suggestion of maternal effects acting upon body weight but the evidence was somewhat contradictory and inconclusive due to the high standard error of the estimates.
(viii) None of the 15 traits measured regressed over the 3 year period of relaxation of selection. 相似文献
2. Age at 50% production was significantly affected by both lighting treatment and rearing regimen.
3. The light pattern treatments had no significant effect on any cumulative performance variable measured from 20 to 80 weeks of age.
4. Breed had a significant effect on eggs/hen housed, rate of lay, egg weight, egg output and food intake.
5. Rationing feeding during rearing, by holding intake at its 6‐week level from 6 to 14 weeks of age, was associated with significantly lower egg production, but had no effect on egg weight or food intake during lay.
6. Although both rearing and light treatments influenced age at 50% production, this character was not correlated with egg weight or egg production.
7. It is suggested that modern hybrid laying stocks are so genetically predisposed to ovulate that they are becoming refractory towards treatments hitherto regarded as influential. 相似文献
The aim of this experiment was to determine the profit returned at 12 weeks by broiler chickens hatched from eggs ranging in weight from 44 g. to 58 g. at one gram intervals and to determine how competitive and separate rearing might modify the relationship.
A total of 6000 eggs were collected during 10 days from a 28‐week‐old, broiler breeding flock and graded into the above mentioned egg weight classes. From these, a total of 3480 day‐old broilers were housed. Each egg weight class was equally represented and balanced for sex.
Hatchability and fertility showed no consistent trend with egg weight for eggs above 46 g., but below the 47 g. level there was a trend of declining fertility and hatchability.
A strong positive relationship was found between the weight of the chick at 1 day of age and egg weight for both males and females with no significant difference overall in body weight between the two sexes.
Body weight to 12 weeks was found to be strongly related to egg weight, in a linear fashion, though this influence declined with age.
There was a greater influence of egg weight on body weight at all ages in the separate rearing treatment compared with competitive rearing but this was not significant after 10 weeks.
Egg weight had an important bearing on body weight and profit at 12 weeks, but no effect on food conversion or mortality.
The increased profit over food costs per 100 day‐old chicks was found to be 52.75 cents for the separately reared birds respectively for each 3 g. increase in egg weight. 相似文献
2. In 3 treatments the diet was supplemented with 0, 100 and 150 mg probiotic/kg food.
3. In the 100 mg probiotic group, egg production improved by 5%, and shell thickness improved slightly, with fewer thin‐shelled eggs than in the control (8.6% compared to 18.6%).
4. The initial serum cholesterol concentration of 170.2 mg/dl in control birds remained similar throughout the 10‐week experimental period, whereas in the 150 mg group the initial value of 176.5 mg/dl decreased to 114.3 mg by week 10.
5. Yolk cholesterol concentration was 14.69 mg in the control group and 11.28 and 11.37 mg/g in the 100 and 150 mg probiotic groups respectively. Overall mean total egg cholesterol was thus reduced by probiotic supplementation. 相似文献
2. Yolk cholesterol concentration decreases between 20 and 30 weeks of age, and then remains constant until 70 weeks of age. Yolk total lipid concentration increases to a maximum at 40 weeks of age before decreasing to its original value at 60 and 70 weeks of age.
3. Bird means for yolk cholesterol and total lipid concentration are negatively related at 20 weeks of age, and essentially independent for the remainder of the first year of egg production.
4. Variation for yolk cholesterol concentration between 30 and 70 weeks of age appears to be a consequence of differences in the proportion of cholesterol to other lipid components.
5. Uptake of plasma lipoproteins characteristic of the immature bird is likely to be responsible for the high yolk cholesterol concentration at 20 weeks of age. 相似文献
2. The inclusion of AA improved egg production, food intake and efficiency of utilisation, and decreased the cost of food per kg egg. The addition of 400 mg AA/kg diet gave the most efficient performance.
3. Palm oil inclusion reduced the effect of heat stress and increased egg production, egg weight, food intake and efficiency of utilisation.
4. When 200 mg AA and 50 g palm oil/kg were used, additive responses were obtained with further improvements in egg production, food cost and efficiency.
5. Ascorbic acid and palm oil when fed alone or in combination reduced the incidence of cracked eggs.
6. Thus, 400 mg ascorbic acid/kg of diet, 50 g palm oil or 200 mg AA plus 50 g palm oil/kg diet ameliorated the effects of heat stress in laying hens. 相似文献
2. Food intake was least when restrictions were started at 3 weeks.
3. Sexual maturity was delayed in proportion to the severity of restriction and resulted in lower percentages of small eggs.
4. Egg numbers decreased as restriction increased.
5. Mortality in restricted groups during rearing and laying was higher.
6. Optimal restriction was apparently intermediate between treatments producing 88 or 76% of ad libitum‐fed body weight. Body weight was so excessively affected by the most severe restriction that total production was adversely affected.
7. Restriction from 3 weeks was more profitable than restriction from 6 or 9 weeks, resulting in lower food cost during rearing and higher total egg production. 相似文献
2. Treatments did not affect egg numbers, food consumption, conversion efficiency of food to egg, bodyweight gain or mortality.
3. Increasing dietary calcium (Ca) significantly increased plasma Ca and inorganic phosphorus (P), breaking strength at the radius and egg specific gravity and significantly decreased plasma alkaline phosphatase and egg weight.
4. Increasing dietary phosphorus increased plasma P and decreased egg specific gravity significantly.
5. Plasma Ca, P and alkaline phosphatase and radius breaking strength were suitable indices of the Ca status of the hens. 相似文献
2. A total of 8534 records from 900 quail, hatched between 2014 and 2015, were used in the study. Average weekly egg weights and egg numbers were measured from second until sixth week of egg production.
3. Nine random regression models were compared to identify the best order of the Legendre polynomials (LP). The most optimal model was identified by the Bayesian Information Criterion. A model with second order of LP for fixed effects, second order of LP for additive genetic effects and third order of LP for permanent environmental effects (MTRR23) was found to be the best.
4. According to the MTRR23 model, direct heritability for EW increased from 0.26 in the second week to 0.53 in the sixth week of egg production, whereas the ratio of permanent environment to phenotypic variance decreased from 0.48 to 0.1. Direct heritability for EN was low, whereas the ratio of permanent environment to phenotypic variance decreased from 0.57 to 0.15 during the production period.
5. For each trait, estimated genetic correlations among weeks of egg production were high (from 0.85 to 0.98). Genetic correlations between EW and EN were low and negative for the first two weeks, but they were low and positive for the rest of the egg production period.
6. In conclusion, random regression models can be used effectively for analysing egg production traits in Japanese quail. Response to selection for increased egg weight would be higher at older ages because of its higher heritability and such a breeding program would have no negative genetic impact on egg production. 相似文献
2. There was no effect of age at restriction (15 to 18 compared with 19 to 22 weeks) on the number of yellow follicles.
3. The treatment with the larger body weight of two groups given the same degree of restriction (maintenance) had more follicles than the treatment which had a smaller body weight.
4. There was a positive linear relationship between the number of yellow follicles and body weight and food intake. Addition of the weight of fat or age at first egg to the model increased the residual mean squares.
5. The proportion of atresia among yellow follicles and the incidence of internal ovulation increased with body weight at first egg.
6. It was concluded that the physiological processes occurring during rearing which underlie ovarian function are reflected solely in the body weight and food intake of broiler breeders at first egg. 相似文献
2. Wheat reduced food intake by 8%, increased efficiency of food conversion and live‐weight gain while barley increased litter moisture content, and, during the first half of the laying year decreased egg production by 3.3% and yolk colour by 4%.
3. Hens offered whole grains ate 11% less food, converted food into eggs more efficiently, were heavier and laid larger eggs than those given the mash diets.
4. With whole grains yolk colour was less than with mash diets during the first 24 weeks of lay but this was reversed during the last 24 weeks of lay.
5. Either canthaxanthin or citranaxanthin or β‐apo‐8'‐carotenoic acid ethyl ester plus canthaxanthin in diets containing lucerne meal produced eggs with acceptable yolk colours. 相似文献
2. During the last 7 years a random breeding sample of the production flock served as a genetic control.
3. Regressions of deviations of the production flock from the control flock on years, were highly significant for age at sexual maturity (‐2.18 d), egg production up to 275 d old (3.04 eggs), egg production to 500 d old (5.04 eggs) and egg weight at 14 months old (October) ( — 0.79 g).
4. The heritability of egg production up to 275 d old declined significantly from 0.35 to 0.19.
5. The realised heritability of egg production up to 275 d old was estimated to be 0.14.
6. The genetic correlation between egg production up to 275 d old and production in the residual part of the year was 0.48.
7. The rate of inbreeding in the production flock was 0.515% per generation and the expected rate of inbreeding in the control flock 0.21% per generation. 相似文献
2. After feeding ad libitum in the rearing period, mean body weights of the three crossbred strains at 20 weeks of age were 1.75, 1.66 and 1.55 kg and that of the White Leghorn strain cross was 140 kg. The differing restrictions during rearing reduced mean body weight at 20 weeks by 14 to 33% and increased the time to sexual maturity by 8 to 23 d.
3. All restriction regimes during rearing increased mean egg weight and tended to reduce mortality in the laying period. Optimum hen‐day egg number over 64 weeks of lay was obtained following mild restriction (14% body weight reduction) of the two heavier strains or ad libitum feeding of the lighter strains. Over 48 or 64 weeks of lay, egg number per hen housed (at 18 to 20 weeks of age) was optimised after moderately restricting (14 to 21% body weight reduction) the crossbred strains or feeding the White Leghorn strain cross ad libitum.
4. Over 64 weeks of lay, mortality was reduced from 19.3% to 10.5% in the lightest crossbred strain, in which a high proportion of deaths were associated with Marek's disease and lymphoid leucosis, by restriction during rearing.
5. Restricting food intake by 7 or 8% throughout the laying period reduced hen‐day and hen‐housed egg number and mean egg weight of all four strains. The reduction in hen‐day egg number associated with food restriction during lay was less for the heavier strains that had also been restricted during rearing.
6. Metabolisable energy intakes required to support maximum production over 64 weeks of lay were 1.23 to 1.36 MJ/d. 相似文献