Genetic Parameters For Growth Research Articles

Intraspecific hybridization in Pinus caribaea var. hondurensis II. Genetic parameters

Genetic parameters of growth and stemstraightness to seven years of age wereestimated from two field populations ofpure Pinus caribaea var. hondurensis provenances and theirintraspecific hybrids, (Mountain Pine Ridge(MPR) × coastal provenances). There were noconsistent differences in the geneticparameter estimates obtained for theparental provenances compared to those fromthe MPR × coastal inter-provenance hybridcrosses. Narrow-sense heritabilities ofgrowth traits (0.06–0.33) andstraightness (0.21–0.50) were within therange of estimates that have beenpreviously reported for this species andother tropical pines. In general, additivevariance was found to be more importantthan dominance variance for growth andstraightness traits. There was no strongevidence to affirm that the superiority ofthe MPR × coastal hybrid could be caused bydominance variance. The low magnitude ofthe type-B genetic correlations within theMPR × coastal hybrid crosses suggested thatthe genotype-by-environment interactionmight be of practical importance inbreeding. For future hybridization of theMPR and coastal provenances, a recurrentselection scheme based on the utilizationof additive genetic variance of both parentpopulations is recommended.

Genetic parameters for growth and feed efficiency in weaner versus yearling Charolais bulls

Data on young Charolais bulls were used to evaluate the effect of age of dam, and provide genetic parameter estimates for growth and feed efficiency traits in weaners compared with yearlings. Records on 510 performance test bulls born from 1985 to 1989 and 792 progeny test bulls born from 1988 to 1997 were used, plus available pedigree information (total n = 5493). After weaning (approximately 225 days of age), progeny test bulls were housed in barns and tested until 15 months for all bulls and 19 months of age for half of the bulls. From the records, the test period was artificially partitioned into a weaner and a yearling test. Both tests were for 140 days, with the weaner test commencing at approximately 274 days of age (6–8 weeks after weaning), and the yearling test commencing at approximately 430 days of age. For each test (weaner or yearling), average daily gain, daily feed intake, feed conversion ratio (feed intake per unit weight gain), and residual feed intake (feed intake net of the expected requirements for growth and maintenance) were calculated. Liveweights at 12 and 18 months of age were also studied. Age of dam effect was significant (P < 0.05) for weight at 12 and 18 months of age, and for all weaner traits except residual feed intake. All the traits studied were moderately heritable (0.20–0.46) except for feed conversion ratio in yearlings (0.10). Genetic correlations for the same traits measured in weaners and later in yearlings were less than unity (0.42–0.95), with the 3 highest correlations obtained for weight (0.950.03), feed intake (0.900.07), and residual feed intake (0.750.12). Therefore, for genetic improvement purposes, traits measured in weaners should be considered different from those measured in yearlings, except for weight and feed intake. However, the medium to very high genetic correlations between weaner and yearling tests for most of the traits studied indicate that selection based on weaners will have a positive correlated response in yearlings and vice versa.

Genetic parameters for growth and carcass traits of Japanese Black (Wagyu) cattle

AbstractRestricted maximum likelihood analyses fitting an animal model were conducted to estimate genetic parameters with a pooled-data set of performance tests (growth traits and food intake) on 661 bulls and progeny tests (growth traits and carcass traits) on 535 steers. Traits studied included concentrate intake (CONC), roughage intake (ROU), TDN conversion (TCNV), TDN intake (TINT) of bulls; rib eye area (REA), marbling score (MARB), dressing proportion (DRES) and subcutaneous fat depth (SCF) of steers. Body weight at start (BWS), body weight at finish (BWF) and average daily gain (ADG) of all animals were measured. Estimated heritabilities were 0·18 (CONC), 0·71 (ROU), 0·11 (TCNV) and 0·36 (TINT); 0·02 (REA), 0·49 (MARB), 0·15 (DRES), 0·15 (SCF), and from 0·20 to 0·38 for growth traits. Genetic correlations of ROU were different from those of CONC, probably due to inconsistent restrictions on concentrate intake; those of TINT with the weights, ADG and SCF were high. MARB showed positive genetic correlations with growth traits and low correlations with TINT and SCF. High potentiality for improvement of marbling score was suggested.

Long-Term Selection for Body Weight in Japanese Quail Under Different Environments

Long-term selection was conducted for high 4-wk BW in Japanese quail under different selection environments to investigate selection limits and to determine whether genetic parameters for growth are similar to those in chickens. Quail lines were selected under an adequate 28% CP diet (P line) and under a low 20% CP diet (T line). Mean realized heritabilities ranged from 0.32 (T line) to 0.49 (P line) during the first 10 generations. Although genetic variation remained following 97 generations of selection, realized heritabilities obtained agreed with theoretical predictions of loss of additive genetic variability with continuous selection. Similarity of heritability estimates indicates that Japanese quail are an excellent model for genetic studies of growth in meat-type chickens.Positive relationships accompanying selection for high 4-wk BW were increases in adult BW, age at first egg, and egg weight. Negative relationships were decreases in percentage fertility and hatchability, and egg production. Increased growth rate in selected lines was accompanied by an increase in feed and water intake, and by improvement in feed efficiency. Feed efficiency differences appeared to be important only immediately following hatch, whereas feed intake differences were present from 0 to 4 wk.Evidence of major physiological changes accompanying selection for growth were not observed. However, changes were observed in increased “resource allocations” to supply organs, during late embryonic stages and the 1st wk posthatch. Carcass composition was similar between unselected and selected lines except for higher fat and lower moisture levels in selected lines.

Genetic variation and covariation for growth, parasite resistance and heat tolerance in tropical cattle

Genetic parameters for growth, parasite resistance and heat tolerance in zebu-cross cattle in a tropical environment were estimated by restricted maximum likelihood procedures using various forms of an animal model. Heritability estimates for direct additive genetic effects for liveweights at birth, weaning, 12 and 18 months were 0.61, 0.20, 0.25 and 0.26, respectively and corresponding maternal additive genetic effects were 0.11, 0.32, 0.20 and 0.09. Estimates of genetic correlations between direct and maternal additive genetic effects were zero. Weight gains during the dry season were genetically uncorrelated or slightly negatively correlated to birth weight, preweaning weight gain or gains during the wet season. Heritability estimates for rectal temperature, numbers of ticks, buffalo flies and worms were 0.19, 0.34, 0.06 and 0.28, respectively, with corresponding repeatability estimates of 0.23, 0.45, 0.06 and 0.29. Phenotypic correlations between adaptive traits (heat tolerance and parasite resistance) and growth traits were low. Genetic correlations between growth and rectal temperature were negative. Genetic correlations of growth traits with worm and fly burdens were positive and with tick burdens were zero. It was concluded that in reasonably adapted genotypes, selection for growth in the Australian tropics would result in improved heat tolerance and reduced resistance to parasites. The effect of genotype on parameter estimates is discussed.

Genetic parameters of growth, feed intake, feed conversion and carcass composition of dual-purpose bulls in performance testing.

Genetic parameters for growth, total energy intake, feed conversion ratio, average daily energy intake and carcass composition were estimated in an experiment with 650 bull calves from 31 half-sib groups of Holstein Friesian or Brown Swiss sires. All traits analyzed had an amount of additive genetic variance that allows for considerable response to selection. No interaction between genotype (sire group) and proportion of roughage in the diet was found. Daily gain was strongly correlated negatively with feed conversion ratio but positively correlated with daily energy intake. Results indicate that genetic selection for either daily gain or average daily energy intake would decrease carcass fatness at a constant slaughter weight. However, the environmental correlation between daily energy intake and carcass fatness was positive.

Genetic parameters of growth in rainbow trout, Salmo gairdneri, as a function of age and maturity

The relative magnitude of additive genetic effects, non-additive genetic effects and maternal effects was determined for size, growth, condition factor and age at sexual maturity for rainbow trout at 2.5 and 4 years of age using a factorial mating system. The data consisted of 747 fish from seventeen 2×2 factorial mating sets. Heritability estimates for length and weight ranged from 0.13±0.17 to 0.38±0.22. Condition factors were more heritable than size, with heritability estimates ranging from 0.46±0.24 to 0.66±0.27. The heritability estimate of age at sexual maturity was 0.21±0.14. Maternal effects were not important for any traits. Non-additive genetic effects were important for all size and growth traits except instantaneous growth rate for weight at 2.5 years of age. Physiological status with respect to maturation and smolting was related to size and affected growth rates. Some of the additive and non-additive genetic variation in size and growth was due to family differences in physiological status. Selection on size after physiological differentiation should take into account the physiological status and history of each fish, if possible. Crossing of lines may be helpful for improving size in maturing fish. Genetic correlations between size or condition factors measured at different ages were all positive. Hence, selection at one stage should improve size or condition factor at another.

Genetic parameters of growth and carcass composition in crossbred lambs

ABSTRACTData were available on crossbred meat lambs for 10 live-weight and growth traits (2585 lambs), 5 carcass traits (1884 lambs) and 10 dissection traits (944 lambs). These were the progeny born on an experimental farm over 5 years, from 102, 79 and 65 sires respectively for the three groups of traits. Genetic parameters were estimated from the sire components in a nested analysis of variance within breed of sire and year subclass, adjusting for sex, dam age, rearing type and other factors.The heritabilities of the live-weight and growth traits were all low, the highest being average daily gain to slaughter (0·10, s.e. 0·06), and none was statistically significant. The heritabilities of the traits of carcass composition were much higher: percentage lean (0·41, s.e. 0·13), percentage fat (0·37, s.e. 0·13) and percentage bone (0·16, s.e. 0·10). Intermediate values were found for most other traits: killing-out percentage (0·16, s.e. 0·07), fat depth (0·21, s.e. 0·11), eye-muscle area (0·14, s.e. 0·10) and lean/bone ratio (0·13, s.e. 0·09).Phenotypic and genetic correlations among the traits were also estimated. No major incompatibilities were found among the traits. The results are discussed in relation to the genetic improvement of lean meat production in sheep.

Phenotypic and genetic parameters for growth in guinea pigs.

Data from 1664 guinea pigs of two non-inbred lines or strains were used to estimate phenotypic and genetic parameters of growth. This study suggests the presence of considerable additive genetic variance for growth in one additional mammal. Pooled estimates of heritability for weaning weight, final weight, gain from birth to weaning and gain from birth to 91 days ranged from 0.46 to 0.52. The estimates of heritability for birth weight and gain from weaning to 91 days were 0.25. Thus it appears that selection for increased growth rate should be effective. The high genetic correlation between weaning weight and final or market weight of 0.89 suggests that selection for market weight might be based upon weaning weight with only a slight loss in efficiency.

Genetic parameters of growth between birth and sixteen weeks in Down Cross Sheep

This paper reports a paternal half sib analysis of data collected over 3 years to estimate additive genetic variance of growth between birth and 16 weeks in crossbred progeny derived from Down rams. The data were divided into two groups and pooled estimates of parameters obtained by two methods. The paternal half sib intra-class correlations varied between 0·017 and 0·057 depending on pooling group and method. It is suggested that such low correlations arise because (a) most of the lambs in the study were still sucking at slaughter, close to 16 weeks of age, and the trait measured is thus largely influenced by maternal milking ability (b) the selection practised in the Down breeds may have been effective and reduced genetic variation and (c) there is considerable inbreeding in the Down breeds.In further analysis of data from four farms involving rams mated to more than one breed of ewe there was limited evidence of specific combining ability of growth between birth and 16 weeks of age for Welsh ewes compared to ewes of other breeds.