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1.
Response to selection for up (U) and (D) 3- to 9-wk gain in rats on average daily gain (ADG), average daily feed intake (ADI), gain/feed (G/F), body composition (BC), fasting metabolic rate per unit metabolic size (MR) and partial efficiency of weight gain (ADG/Fg) was evaluated after 34 generations of mass selection. At 3-wk weaning, 120 litters representing F1 crosses of two replicates within each of the U, D and control (C) selection lines were divided within sexes between bulk-feeder and tube-feeder cage types for recording feed intake until 9 wk of age. Rats from tube-feeder cages representing 16 litters/line were utilized for MR and BC data. Response in ADG was asymmetrical; 16% higher for U line but only 8% lower in D line, compared with C line. Correlated responses were positive and significant in both U and D lines for ADI (6% and -3%) and G/F (5% and -5%). Line differences in MR were not significant but both selected lines were slightly higher than C line in MR at 6 wk of age, and the reverse at 9 wk of age. Over the period of 6 to 9 wk of age, maintenance requirements per unit metabolic size and ADG/Fg were 1 and 5% above for the U and -1 and -4% for D lines, relative to C line. Females of both selected lines were fatter than C line (P less than .05) at 9 wk of age, but only D line males were fatter than C line. 相似文献
2.
本文估计了褐壳蛋鸡洛岛红(AA)和浅花苏赛克斯(BB)在正反反复选择(RRS)下的近交系数,分析了近交对选择标准饲料利用率及其相关性状和繁殖性状的影响。试验群体由两纯种及其正反交组合和相应的对照组组成。经过7个世代的RRS和近交试验,试验组AA和BB(括弧里为对照组1AA和1BB)用系谱材料计算出的平均累积近交系数分别为2.58％和3.23％(9.33和8.17%)或每代为0.43%(1.35%),用有效群体含量估计出的AA与BB的相应数值为2.91％与2.83％(5.84%与5.92％)或每代为0.42％(0.86％)。1％近交系数导致的孵化率和饲料利用率的近交衰退较严重(0.5％和0.4％),其次是产蛋性状(约0.3％),而体重和蛋重只有0.1％左右。在本研究中,通过连续7代的RRS与合适的留种率等措施,成功地将闭锁群体的近交系数控制在3%以下的低水平,消除或减轻了近交对饲料利用率等重要经济性状的不利影响。 相似文献
3.
Estimates of genetic parameters and selection strategies to improve the economic efficiency of postweaning growth in lambs 总被引：1，自引：0，他引：1
The objectives of this study were to estimate (co)variance components for growth and feed efficiency measures, and to compare selection strategies to improve economic efficiency of gain. Variance components for pre- and postweaning growth, body weight, and measures of feed efficiency were estimated from data collected on 1,047 Targhee lambs over 7 yr. Approximately 21 d after weaning, lambs were group-fed for 4 wk, with ad libitum access to a diet of 37% whole barley grain and 63% pelleted alfalfa hay. Lambs were then individually fed for 6 wk. Lambs were then returned to group feeding for another 4-wk period. The mean feed conversion ratio (gain/intake) for the individual feeding period was 0.11. Mean postweaning ADG for the total 14-wk feeding period was 0.26 kg. (Co)variance components were estimated from single- and two-trait animal models using REML. The selection strategies compared included direct selection, index selection, and restricted index selection. Estimates of (co)variances derived from single- and two-trait models were similar, except for mid-test body weight. Preweaning growth had a low heritability estimate (0.03 +/- 0.04) compared with postweaning growth measures (0.25 to 0.39), but all measures of growth were highly correlated (r2 > 0.98). Heritability estimates of measures of gain efficiency were variable (total feed intake = 0.39; feed conversion ratio = 0.26; residual feed intake = 0.26). Total feed intake was strongly correlated genetically with feed conversion ratio (0.79) and residual feed intake (0.77). The estimate of genetic correlation between feed conversion ratio and residual feed intake was low (0.23). Comparison of selection strategies showed the superiority of index selection (ADG, total feed, body weight) for economic improvement compared with other strategies. Economic response to direct selection for ADG was at least twice that for direct selection for feed conversion ratio or against total feed intake, and that for restricted indices (selecting against residual feed, while holding body weight and/or gain constant). Selection for ADG may be a practical approach for indirectly improving efficiency of gain in lambs. 相似文献
4.
C. Hagger 《British poultry science》1993,34(2):425-429
1. Phenotypic and genetic parameters were estimated tri‐variately for income minus food cost between 21 and 40 weeks (IFC), food conversion ratio between 41 and 60 weeks (FCR) and feather score at 60 weeks (FSC) from data of 6 generations of a selection experiment aimed at improving IFC genetically in brown egg layers.
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
5.
1. A selection experiment with two lines of White Leghorns originating from a common base population was carried out over 5 generations with the aims of maintaining an unchanged egg weight, reducing age at first egg and reducing adult body weight. Each line consisted of 14 male and 42 female breeders. 2. Males were mass selected for low body weight at 20 weeks of age. To compensate for the expected correlated loss in egg weight, hens were selected according to an index which counteracted this undesirable change while also reducing age at first egg and reducing body weight. 3. An index value was calculated for each individual hen from average egg weight, age at first egg and body weight at 20 weeks. Index weights had to be calculated for each generation and line in accordance with the expected change in egg weight due to male selection on body weight. 4. For control matings hens with an index near the population average were mated either to males with body weight near the population average (control C1) or to the selected males within lines (control C2). 5. Expected and observed total responses agreed well for all traits in line 1 and for body weight in line 2. 6. Phenotypic variances and covariances showed little change during the experiment. However, genetic variances and covariances estimated at the end of the experiment showed some differences, both between lines and compared to the parameters used for index construction. 相似文献
6.
V.H. Nielsen & I.R. Korsgaard 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2006,123(6):362-368
Mice selected for weight gain from 3 to 9 weeks of age on a normal (N) protein diet containing 19.3% protein and a reduced (R) protein diet with 5.1% protein were reared on both diets in generations 7 and 9. The lines NH, NC, NL, RH, RC and RL (H, high; C, control; L, low) were tested for weight gain on diet N and R and for feed intake and feed efficiency on diet N in generation 7. In generation 9, the lines were tested for body composition traits (fat, protein and water percentage) at 3, 6, 9 and 12 weeks of age on both diets. A significant (p < 0.0001) genotype × environment interaction for growth rate was observed in generation 7. Weight gain at both the protein levels was best improved by selection at the protein level itself. Furthermore, the ranking of the lines on diet N was similar for weight gain, feed intake and feed efficiency. In generation 9 at 9 weeks of age, the ranking of the lines for fat percentage was equal to the ranking for weight gain in generation 7 on both test‐diets. The association between weight gain and protein or water percentage was less pronounced, particularly on diet R. These results suggest that the largest genetic improvement in growth rate is obtained when the protein content of the feed is the same in selection and production. However, when selection is carried out in one environment while the animals have to perform under conditions with varying nutrient protein contents, selection in an inferior environment may be advantageous. 相似文献
7.
8.
《The Journal of Applied Poultry Research》2017,26(2):183-191
The objective of the present study was to determine the effect of broiler breeder egg weight on egg quality, chick quality, and broiler performance using Hubbard Classic broiler breeder flock. Hatching eggs from a commercial broiler breeder flock (Hubbard classic strain) were obtained at the age of 60 wk and divided into 3 egg-weight categories, namely small, medium, and large. For this purpose, 930 eggs having weights 63.09 ± 0.21, 68.85 ± 0.23, and 74.81 ± 0.11g were divided into 3 egg categories labeled small, medium, and large respectively. We further divided these eggs into 2 categories, eggs for quality parameters and eggs for incubation and posthatch performance parameters. Eggs from the small egg category had greater proportion of the shell weight and more shell strength. Egg weight did not significantly affect the albumen and yolk weight percentage. Egg weight affected the shape index and specific gravity for which lower values were observed for large eggs. Egg weight positively affected the chick weight, chick yield, and chick length (P < 0.05) of both male and female chicks. Results of the body weight gain showed that effect of egg weight on the posthatch performance of chick diminishes with the age of broilers. Egg weight significantly affected the body weight gain of male and female chicks up to 3 wk of age. Egg weights did not significantly affect the feed intake and mortality of broiler. Different egg-weight categories significantly affected the feed conversion ratio of female chicks at wk 2 and 3 of age and did not affect the feed conversion of male and female chicks at the end of wk 5. In conclusion, egg weight positively affected the chick characteristics (e.g., chick weight, chick length) and did not affect the final live body weight, feed conversion ratio, feed intake, and mortality in broilers. 相似文献
9.
本文报道了蛋鸡饲料利用率及其相关性状和孵化率的杂种优势。材料来源于一个正反反复选择饲料利用率的试验,8个世代共有蛋鸡13408只。试验组(括弧里为对照组)各性状的平均杂种优势分别为:饲料利用率-2.0％ (-0.8％)、饲料消耗量2.9％(3.0％)、产蛋量4.5％(3.6％)、产蛋率2.9％(3.1)、蛋重1.9％(0.8％)、试验期初体重3.7％ (4.5％)、试验期末体重4.3％(5.0％)、受精率2.1％(-0.2％)、受精蛋孵化率15.0％ (4.5％)和入孵蛋孵化率10.2％(7.6％)。正反交组合的杂种优势不同,这可能是由性连锁导致的。 相似文献
10.
1. Mass selection in two replicate lines of Leghorn chickens was practiced for low 20‐week body weight in males and by an index designed to reduce age at first egg, body weight at 20 weeks and maintain a constant early egg size in females.
2. Selection responses in body weights of hens at 40 and 60 weeks of age, as well as in average egg weight of all eggs, egg number, egg mass and feed conversion at the above ages are given for 5 generations of selection.
3. Estimation of genetic responses were made separately for selection on males (M i ) and females (F i ) using control groups of hens from matings between females with an index near the population average and either males with body weight near the population average (Cl) or the selected males within lines (C2).
4. Total genetic response to selection of both parents (CR i ) showed an expected decline in body weights of hens, small changes in egg weights and egg numbers, and an improved feed efficiency. 相似文献
11.
The present study compares embryonic mortality between lines selected for different production traits, assesses the effects of inbreeding of the hen and embryo on embryonic mortality, and estimates genetic parameters of embryonic mortality. The experiment covered 10 generations of selection for increased egg number (EN), egg weight (EW), egg mass (EM) and a control line (C). The data included age at 1st egg, egg number and egg weight. Percent fertile eggs (PF), percent hatched of fertile eggs (PHF) and percent dead chick at hatch (PDH) were also recorded for the selected parents. PDH was higher in the selected lines than in the control line. Among the selected lines, the EW line had the highest embryonic mortality. Inbreeding of the hen and embryo had no significant effect on PDH in any of the lines. Estimates of heritability for PDH were 0.10+/-0.05, 0.02+/-0.02, 0.03+/-0.02 and 0.02+/-0.02 for lines EN, EW, EM and C, respectively. There was a positive genetic correlation between egg weight and PDH in line EW indicating that selection for increased egg weight was associated with high embryonic mortality. A negative genetic correlation between PDH and reproductive traits in line EN was observed, which is favourable. 相似文献
12.
Seventy-six primiparous Duroc and Landrace sows from two genetic lines with or without selection for improved sow productivity were used to identify sow traits that affect postweaning gain (positive or negative) and feed intake. Sows lost weight (P less than .01) and consumed less feed (P less than .01) during wk 1 postweaning (37 d) compared with wk 2, 3, and 4. Sows gained more weight during wk 2 and 3 (P less than .01) than during wk 4. Weekly feed consumption was similar during wk 2 and 4 and highest during wk 3 (P less than .05). Sow weight gain postweaning was predicted by sow weaning weight (P less than .01) and adjusted 21-d litter weight (P less than .05) during wk 1, wk 1 to 2, and wk 1 to 4 feeding periods. Feed consumption was best predicted by adjusted litter weaning weight (P less than .01), sow weaning weight (P less than .01), average backfat at farrowing (P less than .01), average backfat change (P less than .05), and adjusted 21-d litter weight (P less than .05). Feed intake was positively correlated (P less than .01; r = .77) and sow weight at breeding, farrowing, and weaning was negatively correlated (P less than .05; r = -.23, -.21, and -.26, respectively) with sow weight gain. Average backfat at weaning was negatively correlated (P less than .05) with gain and feed intake during each period. Adjusted 21-d litter weight and adjusted litter weaning weight were positively correlated with postweaning feed intake (P less than .05; r = .22 and .23, respectively).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
13.
《The Journal of Applied Poultry Research》2008,17(4):432-439
An experiment was conducted to determine the influence of dietary energy on performance, egg composition, egg solids, egg quality, and profits of Hy-Line W-36 hens fed different protein levels. The experiment was designed as a 4 × 3 factorial arrangement with 4 added dietary energy levels (0, 79, 158, and 238 kcal of ME/kg) and 3 protein levels (14.89, 16.06, and 17.38%). The basal diets of 17.38, 16.06, and 14.89% protein contained 2,751, 2,784, and 2,815 kcal of ME/kg, respectively. This study lasted 12 wk. Molted Hy-Line W-36 hens (n = 1,440) in phase 1 (70 wk of age) were randomly divided into 12 treatments (8 replicates of 15 hens per treatment). Protein had a significant effect on egg production, egg mass, feed intake, feed conversion, egg weight, percentage of egg shell components, yolk color, and yolk and albumen weight. As dietary energy increased from 0 to 238 kcal of ME/kg by addition of poultry oil, feed intake linearly decreased. Increasing dietary energy also significantly increased BW and egg yolk color. As dietary energy increased, percentage yolk solids increased at the 2 greater dietary protein levels, whereas egg-specific gravity linearly decreased at the 17.38% protein level. Increasing dietary energy and protein significantly improved feed conversion. Increasing protein intake significantly increased albumen and yolk weight but had no influence on yolk, albumen, or whole egg solids. Because feed ingredient and egg prices vary, there can be no fixed ideal dietary energy level for optimal profits during molt phase 1 (70 to 81 wk). 相似文献
14.
1. Two‐way selection was performed in a White Leghorn population for percentage residual food consumption, defined as the percentage deviation of the observed from the expected food consumption. Expected food consumption was estimated using a multiple regression equation including weight gain, egg production and metabolic body size as independent variables.
2. Three selection lines were established from a common population, two low lines and one high line. In addition, one control line was kept. The generation interval was one year and the experiment lasted for 4 generations.
3. The direct selection response was considerable and the realised heritability was close to 0.5. Food intake and food conversion (FCR) were lower in the low lines than in the high line.
4. The correlated selection responses showed no phenotypic or genetic correlations between percentage residual food consumption and egg production, but one of the low lines had a heavier adult body weight than the high line. No undesirable correlated responses were observed. 相似文献
15.
Genetic relations of yolk proportion and chick weight with production traits in a White Leghorn line 总被引：1，自引：0，他引：1
1. The main purpose of this study was to estimate genetic correlations between yolk proportion, chick weight and production traits using an animal model. 2. Direct-direct genetic correlations were estimated between yolk proportion and age at first egg (-0.34), body weight at 20 (0.10), 40 (0.58) and 60 (0.52) weeks of age, egg number (0.56), egg mass (0.59), feed intake (0.64) and feed conversion (-0.25). 3. Maternal-direct genetic correlations were estimated between chick weight and age at first egg (0.40), body weight at 20 (0.57), 40 (0.66) and 60 (0.56) weeks of age, egg number (-0.50), egg mass (0.21), feed intake (0.45) and feed conversion (0.17), respectively. 4. In conclusion, the results suggest that selection on a higher yolk proportion would not have any unfavourable effects on egg production. Maternal-direct genetic correlations between chick weight and production traits resembled direct-direct genetic correlations between egg weight and production traits found in other studies. 相似文献
16.
C. Costa M. Baselga J. Lobera C. Cervera J. J. Pascual 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2004,121(3):186-196
An experiment was carried out to evaluate the response obtained in a three‐way cross of rabbits when the lines involved had undergone within‐line selection for litter size or postweaning daily gain. The interaction between the level of nutrition and genetic level of the crossbreds was also studied. Using frozen embryos, old (H1) and current (H2) crossbred does and young were compared contemporarily. Does were fed a standard diet or a diet having high digestible energy and protein. The difference in the number of generations between lines used to produce both crosses were: 13 or 0 for the maternal lines, and 12 for the paternal line. The traits studied in the crossbred does were: daily feed intake during gestation, during the first 3 weeks of lactation and during the last week before weaning; doe weight at mating and at kindling; litter weight at birth and at weaning; total litter size, number born alive and litter size at weaning. The recorded traits for the young were: individual weight at weaning and at 63 days; individual daily gain after weaning; daily feed intake and feed conversion index. The last two traits were recorded as averages per cage. A total of 1161 litters from 190 does were involved. Significant differences in litter‐size traits, between H1 and H2 does, were observed and were higher than the expected from the within‐line response. The doe effect was not significant for other doe traits, adjusted to a constant litter size. The estimated difference in postweaning daily gain between H1 and H2 young was significant and in favour of H2, but the value was considerably lower than expected. The effect of type of feed and the interaction with the type of doe was not significant for any doe trait. The type of feed consumed by the doe was significant for postweaning daily gain, and the interaction with the type of crossbreds was significant for this trait and for individual weight at 63 days. 相似文献
17.
Improvement in feed efficiency when selection is based on gain:feed ratio has often been accompanied by a reduction in feed intake. The following four criteria were used in mass selection for improved lean gain efficiency in mice with an objective of evaluating changes in lean gain and intake: 1) gain deviation, animals selected had the greatest gain in fat-free mass (FFM) after adjustment to a constant intake; 2) intake deviation, mice selected had the least feed intake after adjustment to a constant gain in FFM; 3) intrinsic efficiency, similar to the second criterion except that adjustment was also made for average weight maintained during the period; and 4) a positive control that used the ratio of gain in FFM: feed intake as the selection criterion. A fifth line, in which a male and a female were selected at random from each litter, served as a negative control. Experimental animals were outbred mice of the CF1 strain. Two replicates of the five lines were included in the study. Twelve males and females were pair-mated within each line-replicate combination each generation. Feed disappearance was measured from 25 to 42 d. Mice were scanned to obtain an electrical conductivity measurement for prediction of FFM. After six generations of selection, realized heritabilities for gain:feed, gain deviation, intake deviation, and intrinsic efficiency were .00 +/- .04, .04 +/- .29, .35 +/- .08, and .28 +/- .06, respectively. There were no differences among lines for gain:feed ratio. The correlated response in feed intake reduction was significant in the intake deviation and intrinsic efficiency lines (-.17 +/- .05 and -.21 +/- .04 g x d(-1) x generation(-1), respectively). The realized genetic correlations between the ratio and gain deviation, intake deviation, and intrinsic efficiency were .83 +/- .15, .01 +/- .04, and .21 +/- .12, respectively. Litter size was depressed in all selected lines. 相似文献
18.
1. Data from 16 inbred lines derived by three generations of full sib mating from a common outbred base population were used to estimate genetic correlations between body weight, abdominal fat content, follicle number, liver weight, egg weight and egg number using between‐line variances and covariances. 2. High genetic correlations were found between body weight, fat content and egg weight. Low genetic correlations were found between follicle number and all traits other than egg weights. 3. Theoretical expectations and low correlations within lines led to the conclusion that environmental correlations among the traits considered were very low. 相似文献
19.
Literature on the genetic variation in Voluntary Feed Intake (VFI) and traits related to VFI under ad lib. and restricted feeding has been reviewed. Also differences between breeds and selection lines are reviewed and discussed.Heritability estimates of VFI show average values of 0.12–0.59, with larger variation on real ad lib. feeding compared to “to appetite” feeding twice a day. It is also concluded that the genetic correlation between feed intake and gain is higher under ad lib. feeding than under restricted feeding, and that genetic correlation between daily gain and feed/gain decreases from about ?0.9 under restricted feeding to about ?0.6 under ad lib. feeding.Results from a Norwegian selection experiment indicate that there is no correlated response in daily feed intake (feeding “to appetite”) when selecting on backfat and daily gain, while other selection experiments, where feed conversion ratio has been the major component of the selection index, show reduced appetite.The present paper discusses the danger of reduced appetite in selection programmes that maximize short-term economic gain, and the importance of selection objectives and feeding regime on the genetic correlations between VFI and other production traits. A comparison is also made between population parameters of Norwegian and Danish Landrace pigs. 相似文献
20.
M E Davis 《Journal of animal science》1987,65(4):886-895
As part of a divergent selection experiment (high vs low feed conversion) designed to obtain realized genetic parameter estimates for postweaning feed conversion, 35 Angus bull calves were selected each year from 1979 through 1983 to be fed in a 140-d postweaning performance test. From these 35 individually-fed bulls, the three most efficient and three least efficient (in terms of kilograms of total digestible nutrients required per kilogram of gain) were selected each year to each be mated to approximately 20 purebred Angus cows in a test herd. In the last 2 yr of the experiment, feed:gain ratios were adjusted for differences in maintenance requirements before selection. An alternative to selection based on feed/gain or adjusted feed/gain would have been to select on an index of feed intake and gain (Index3 = -1.0 feed intake + 3.87 gain) where feed intake was either unadjusted or adjusted (AdjIndex3) for differences in maintenance requirements. Residual correlations (year effects removed) among the four selection critera were large ([r[ greater than or equal to .76; P less than .01) as were correlations among ranks of the bulls based on the four selection criteria ([r[ greater than or equal to .75). Predicted genetic change for fee:gain ratio in both the high and low directions was greatest when selection was based on feed:gain ratio or Index3. Genetic changes expected to result from selection for feed:gain ratio or Index3 were similar, as were genetic changes expected due to selection for adjusted feed:gain ratio or AdjIndex3.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献