Traits In Progeny Research Articles

Individual variation in progeny size and quality in rainbow trout, Oncorhynchus mykiss (Walbaum)

Early life history traits of fish are very variable as a result of both genetic and environmental factors. In this study, we examine individual variation in early life history traits in progeny of seven females crossed with one male rainbow trout, Oncorhynchus mykiss (Walbaum). Individual eggs were followed from fertilization through hatching until death of the larvae by starvation. Larvae and yolksac size (size was shown to be a good indicator of energy content) increased with increasing egg size, but there were still differences between families after variation in egg size was accounted for. Incubation time was not correlated with egg size, and did not differ between families. The progeny from the different families utilized the available energy differently, as both longevity and growth-rate without food was independent of yolk-sac size, but strongly dependent on family. The observed between-family differences in early life history traits in rainbow trout were mainly caused by genetically based effects; egg size and thus probably egg quality, which differed strongly bet ween females, could not adequately explain these differences.

Effects of selection for scrotal circumference in Limousin bulls on reproductive and growth traits of progeny.

Nine pairs of Limousin bulls from nine contemporary groups were acquired, with each pair consisting of one large scrotal circumference (SC) bull and one small SC bull. Average adjusted yearling scrotal circumferences were 36.3 cm (SD 1.6 cm) and 28.5 cm (SD .9 cm) for large SC (LP) and small SC (SP) bulls, respectively. In addition to the phenotypic grouping, non-parent SC EPD were used to group bulls into high (HE, > .53 cm), average (AE), and low (LE, < -.61 cm) lines. Each bull was mated to a randomly assigned group of 15 to 20 Brangus x Hereford cows each yr for 1 to 3 yr. Birth weights, weaning and yearling weights and heights, and ultrasound measurements for backfat and ribeye measurements were taken on 407 progeny. Blood samples were collected on 210 heifer progeny when they averaged 11, 13, and 15 mo of age to determine whether they had reached puberty. When subjected to a breeding soundness exam (BSE), LP bulls scored higher (P < .01) for motility as well as total BSE score. The LP calves had heavier birth weights (P < .05) and greater testicular mass at weaning (P < .01) than SP calves. The HE and AE bull calves had greater (P < .02) testicular mass than did the LE bull calves. A greater (P < .05) percentage of HE heifers had reached puberty by the 11- and 13-mo measurements than either the AE or LE heifers. The HE heifers reached puberty at a younger age than AE (P < .01) or LE (P < .001) heifers. Selection using SC EPD was more effective than phenotypic selection in reducing age at puberty in daughters.

Inbreeding Depression and Maternal Effects in Aquilegia Caerulea, a Partially Selfing Plant

Little is known about how inbreeding depression and maternal effects change from the seed stage through offspring maturation or how these patterns differ for plants germinated under natural vs. artificial conditions. I measured these effects in perennial Aquilegia caerulea (Ranunculaceae) for both field—sown plants and greenhouse—sown progeny that were subsequently transplanted to the field. Overall, field—sown plants and transplants showed similar cumulative inbreeding depression, averaging 0.54 and 0.52, respectively. Selfed individuals had a lower success than outcrossed individuals in all fitness components measured from the number of seeds produced by the cross of size at year 3, and most effects were significant. Inbreeding depression in survival was worse for field—sown progeny in which mortality was much higher. Furthermore, effects of inbreeding on plant size increased each year for greenhouse—sown transplants, but not for field—sown plants, suggesting inbreeding depression is expressed later when survival is artificially high. The effect of seed mass was investigated in greenhouse—sown individuals. Although selfed seeds weighed significantly less than outcrossed seeds, seed mass was not correlated with emergence or survival. It did, however, correlate with leaf expansion rate, which, in turn, correlated with year 3 size in both transplants and field—sown plants. Maternal effects explained a much larger proportion of variance in seed mass than did level of inbreeding. In the greenhouse, effects of seed parent were strongest on early characters, becoming small and nonsignificant by year 3 when inbreeding effects again become significant. In contrast, maternal effects on juvenile traits of field—sown progeny were negligible.

Genetic Incompatibility and Offspring Quality in the Tristylous Plant Lythrum salicaria (Lythraceae)

The purpose of this study was to determine the incompatibility relationships among the three different morphs of the tristylous plant Lythrum salicaria, and to assess whether there are fitness consequences to breakdown in incompatibility. Twenty-four different types of pollinations were performed using all possible combinations of anthers and stigmas. These can be grouped as legitimate pollinations (pollinations from the appropriate anther level of a compatible morph), illegitimate intermorph pollinations (pollinations from the inappropriate anther level of a compatible morph), intramorph pollinations (pollinations between individuals of the same morph), and self pollinations. Legitimate pollinations produced significantly more seed than illegitimate intermorph pollinations, intramorph pollinations, and self pollinations. The difference between legitimate and illegitimate intermorph pollination success is particularly interesting because pollen for these crosses came from the same genetic individual. Pollination types also differed in offspring quality. In the rare examples where progeny were produced by illegitimate intermorph pollinations, the progeny did not have significantly lower values for seedling growth traits compared to legitimate progeny. Seedlings produced by self pollinations had significantly lower values for four out of six seedling growth traits measured. Comparisons of legitimate and self progeny traits indicate that inbreeding depression for most traits is close to or above 0.5. The finding that some seed were produced from illegitimate pollinations suggests that there is variation among individuals in incompatibility. There was a significant effect of parental morph type on the probability of breakdown in incompatibility with the midstyled maternal parents setting more seed from illegitimate pollinations.

Crossbreeding Ayrshire, Friesian, and Sahiwal Cattle for Milk Yield and Preweaning Traits of Progeny in the Semiarid Tropics of Kenya

Individual and maternal additive genetic and heterotic effects were estimated for preweaning, reproductive, and lactation traits of the Sahiwal breed and its crosses with Bos taurus (Ayrshire and Friesian). The individual additive genetic breed effect influenced all cow traits except annual milk yield, and the maternal additive genetic effect influenced all yield traits. The individual and maternal genetic effects between B. taurus and Sahiwal breeds for lactation milk yield were 746 and –601kg, respectively. Individual heterosis for lactation milk yield of 73kg (5%), estimated using the mean of the reciprocal F1 crosses, was not significant but increased to 374kg (28%) when estimated using only the F1 cross sired by B. taurus, showing the important influence of maternal effects. Individual additive genetic effects influenced preweaning daily gain and weaning weight. Maternal additive genetic and heterotic effects affected birth weight, and individual heterosis significantly influenced all calf traits. Maternal additive genetic effects may have biased the estimation of individual heterosis for milk yield in other tropical studies. When stratification is not possible or when reproductive rates are low, two-breed rotational crossbreeding is an efficient system to exploit additive and nonadditive genetic variation for tropical dairy production.

Prediction of performance of progeny from test station boars.

Data were obtained from 1,954 Duroc and 2,252 Yorkshire purebred and crossbred progeny sired by 34 Duroc and 32 Yorkshire boars, respectively. Boars were purchased from the North Carolina Swine Evaluation Station during August 1983 to December 1988. Boars were selected to represent high and low indexes at the test station. Progeny were raised and tested under conditions similar to commercial pig production at the Tidewater Research Station. For each breed of boar (Duroc and Yorkshire), breed type (purebred and crossbred), and sex (castrates and gilts) of progeny, regression coefficients of progeny traits on each sire trait were computed. Progeny traits were ADG, days to 104.3 kg BW (DAYS), backfat thickness (BF), and feed conversion ratio (FC). Sire traits were ADG, DAYS, BF, FC, and INDEX. Effects of boar test group and progeny test group were included in the models. Averaged over breed type and sex, a 25-unit (1 SD) increase in sire INDEX resulted in 14.5 g more ADG, 3.2 fewer DAYS, .57 mm more BF, and .017 lower FC in Durocs and 5.6 g more ADG, .01 more DAYS, .81 mm less BF, and .083 lower FC in Yorkshires. The low magnitude and variable signs of some regression coefficients suggested that predictions of progeny performance from performance of individual sires at the North Carolina Swine Evaluation Station were not very reliable. Differences between regressions for purebreds and crossbreds implied small correlations between the two breed types. Differences between Durocs and Yorkshires indicated that genetic parameters might not be the same for the two breeds.

Multivariate analysis of recombination between wild and cultivated genomes within the primary gene pool of pearl millet (Pennisetum typhoides)

Recombination between wild and cultivated genomes of pearl millet were studied by multivariate analysis on morphological and physiological traits in backcross progenies from four cultivated × wild crosses. The cultivated genotypes, Souna and Thiotandé, have evolved in sympatric and allopatric situations, respectively, with wild forms. The distinct evolutionary history of the cultivated genotypes seems to have an incidence on the segregation pattern of their progenies with the wild relatives. Segregation distortions favouring the recovery of "wild-like" phenotypes were observed in progenies with Thiotandé as the cultivated parent. They are probably a consequence of the genetic divergence between this genotype and wild forms already shown at different levels of observation (histological, physiological, and genetic). On the other hand, when Souna is the cultivated parent, the recovery of "cultivated-like" phenotypes was shown to be easier with Souna as the female. This could be due to preferential homogametic fertilization favouring "Souna-type" gametes on Souna pistils owing to intergametophytic competition through a pollen–pistil interaction, already evidenced on the genotypes used here.Key words: pearl millet, multivariate analysis, segregation distortion, wild/cultivated genome recombination, genetic resources.

Maternal breed of sire effects on postweaning performance of heifer and steer progeny: postweaning growth and carcass characteristics

Heifer and steer progeny of 2-yr-old first-cross (F1) heifers and 3- to 6-yr-old F1 cows, from Hereford dams and five sire breeds, were evaluated for postweaning feedlot growth and carcass composition. Breeds of sire of dam were Angus (A), Red Poll (RP), Tarentaise (T), Simmental (Sm), and Pinzgauer (P). Calves from 2-yr-old heifers were sired by Shorthorn, and calves from 3- to 6-yr-old dams were sired by Charolais. Breed of sire of dam was significant (P less than .05 to P less than .01) for total gain and final weight for female progeny from 2-yr-old dams. At all weights, Sm, P, and T ranked above A and RP. Progeny of A, P, Sm, and T F1 2-yr-old dams were not significantly different but were higher (P less than .05) than RP heifers in total feedlot gain. Breed of sire of dam was significant (P less than .05) for carcass weight and longissimus muscle area; T ranked highest and RP lowest. Breed was not significant for any growth traits of steer progeny of 2-yr-old dams. Breed was significant for marbling score; A ranked highest and exceeded (P less than .01) both RP and Sm steers. Breed was significant (P less than .05) for most growth traits in the heifer progeny of the 3- to 6-yr-old dams bred to Charolais sires. Heifer calves of the Sm group were heavier (P less than .05) than all other groups for most weights and total gain. For total gain, P and T were intermediate and A and RP lowest. For heifer carcass traits from 3- to 6-yr-old dams, breed was significant (P less than .05 to P less than .01) for carcass weight, longissimus muscle area, percentage of cutability, and estimated kidney, heart, and pelvic fat. Heifers from Sm-sired dams were heavier (P less than .05) than those from all other groups but ranked second to heifers from P for percentage of cutability. Marbling scores of RP heifer carcasses ranked highest of all groups. Breed was not significant (P greater than .05) for any of the weights or gains in steer progeny of 3- to 6-yr-old dams; however, the Sm and P groups ranked above A and RP for all feedlot test weights.(ABSTRACT TRUNCATED AT 250 WORDS)

Agronomic evaluation of tissue-culture-derived soybean plants

Genetic alterations of regenerated plants based on the tissue culture process (somaclonal variation) have become common for many plant species including soybean [Glycine max (L.) Merr.]. The objective of this study was to test for the presence of tissue-culture-derived genetic variation in eight agronomic traits in homozygous progeny regenerated by organogenesis using the commercially important cultivar Asgrow 'A3127.' A total of 86 lines derived by repeated self-pollination of nine regenerated plants was grown in two locations for 2 years. When compared to the unregenerated parent, statistically significant variation (P<0.05) was found for maturity, lodging, height, seed protein and oil, but not for seed quality, seed weight, or seed yield. All of the variation noted was beneficial and did not involve decreased yield. Since the differences were not large, the results indicate that the tissue culture process is not necessarily detrimental to plant performance, which is an important consideration since tissue culture techniques are used in many genetic engineering methods.

Inheritance of Selected Traits in Accessions of Vigna vexillata (L) a Rich of Australian and African Origin

The inheritance of several traits in Vigna vexillata was studied for crosses involving accessions of African and Australian origin. Anthocyanin stem pigmentation, silver leaflet midrib, leaflet hirsuteness, presence of long hairs on the calyx lobes, black pod colour, speckled seed testa and twining stem habit all appeared to be conditioned by single completely dominant gene action, as was apparent resistance to powdery mildew. Width of the floral standard, peduncle length, number of seeds per pod, weight of 100 seeds, tuberous root dry weight, total plant dry weight and harvest indices for seed and tuberous roots all appeared to be quantitatively inherited, with moderate broad sense heritabilities. Leaflet shape, the primary distinguishing attribute between the varieties occurring in Australia, angustifolia and youngiana, appeared to be simply inherited. No difficulties were encountered in obtaining F1 and backcross progenies in any crosses. Further, the inheritance of traits in progeny of Australian × African crosses appeared normal and, in the several instances where direct comparison was possible, similar to that observed in crosses within the Australian material.

Combining Ability for Plant and Fruit Traits of Interspecific Blueberry Progenies on Mineral Soil

Data from a four-parent diallel, involving one highbush (Vaccinium corymbosum L.) clone and three interspecific hybrids grown on mineral soil unamended with organic matter, were analyzed to determine combining ability effects for six traits: plant size, berry size, the number of days between flowering and fruiting (# DBF&amp;F), the ratio of total fruit weight to canopy volume (TFW: CYV), days to fruit ripe, and yield. General combining ability effects were significant for all characters tested, except yield and berry size in 1984. Specific combining ability effects were significant for plant size in 1983, #DBF&amp;F in 1984, TFW: CYV in 1984, and berry size in 1985. Vigorous and productive highbush cultivars can be developed for mineral soils by using the interspecific clones from this study and their selected recombinant to combine the genes for plant vigor with the high-quality fruit traits of highbush cultivars.

The expression and perpetuation of inherent somatic variation in regenerants from embryogenic cultures of Pennisetum glaucum (L.) R. Br. (pearl millet)

Genetic analysis was conducted on the qualitative and quantitative traits of sexual progeny derived from embryogenic cultures of two inbred lines of Pennisetum glaucum (L.) R. Br. (pearl millet). These lines included a genetically stable inbred of Tift 23 BE and a genetic marker line, derived from Tift 23BE, which bore qualitative genetic markers for a dominant purple plant trait (P) and two recessive traits, early flowering (e1) and yellow stripe (ys). Tissue culture regenerant populations (R0) and progeny populations (R1) produced from these plants by selfing showed no qualitative genetic variation when derived from the genetically stable inbred Tift 23BE. In contrast, stably inherited qualitative variation for a number of genetic markers was observed in R0, R1, and R2 progeny of the genetic marker line. In a population of 1,911 plants regenerated over a 12-month period, 0.02% of the population lost or showed reduced expression of the purple plant trait and 92% of plants were chlorophyll deficient. Plants showing reduction or loss of anthocyanin synthesis also flowered later. None of the purple plants showed any significant variation in flowering time. The incidence of chlorophyll deficiency increased with time in culture, 51 % of the progeny regenerated after 1 month were chlorophyll deficient, while 100% of the plants regnerated after 12 months were chlorophyll deficient. Qualitative variation was also observed in control populations of the genetic marker line where 1 plant in a total of 1,010 lacked purple pigmentation and a total of 6% showed chlorophyll variation in the first generation (S0). The presence of qualitative variation in controls suggests that the inherent variation present in the original explant was expressed and perpetuated in vitro. Quantitative variation was observed for a number of traits in the first sexual cycle (R1) of the marker line but did not occur in a subsequent generation, suggesting that this variation was epigenetic.

Adapting best linear unbiased prediction (BLUP) for timely genetic evaluation: I. Progeny traits in a single contemporary group for each sex.

The first step of a procedure to partially circumvent the voluminous calculations with extremely large matrices for the usual algorithms for a BLUP (best linear unbiased prediction) approach is presented. This procedure, specific for a hierarchical portion of a model relevant to many animal breeding populations, is pertinent especially for polytocous species such as swine and poultry. For these, the occurrence of full-sib families makes the inclusion of dam effects in the model more necessary than in dairy or beef cattle models, where dam effects often are omitted. The formulas are derived for the hierarchical model for sires, dams within sires, individuals within full-sib family, and records within individuals, showing a relatively simple structure for such predictors. These formulas provide the basis for an alternative computing algorithm for obtaining evaluations having the statistical properties of best linear unbiased prediction. Formulas also are developed to approximate the prediction error variances for such models. Following this, the methodology for combining separate BLUP predictors, both error-independent and correlated, is developed.

Adapting best linear unbiased prediction (BLUP) for timely genetic evaluation: II. Progeny traits in multiple contemporary groups within a herd.

The second step of a procedure to partially circumvent the voluminous calculations for some BLUP (Best Linear Unbiased Prediction) computing algorithms for genetic evaluation is presented. In addition, the procedure allows timely evaluations of each contemporary group. This procedure is pertinent especially for polytocous species such as swine and poultry, for which the occurrence of full-sib families makes the inclusion of dam effects in the model necessary and tests are completed throughout the year. Formulas are developed for a model including sires, dams, individuals within full-sib families and records within individuals. This model has a fundamentally hierarchical structure but includes some cross-classification. The formulas for predictors combine information across contemporary groups within a herd and incorporate relationships between sires and(or) dams in that herd. Formulas to approximate prediction error variances also are developed.

Yielding ability and phenotypic traits in the selfed progeny of protoplast-derived rice plants.

The first progeny plants (Pt2 generation) of original protoplast-derived plants of three Japanese rice cultivars, Nipponbare, Fujisaka 5 and Iwaimochi were respectively cultivated in submerged paddy fields on an ordinary scale. They were planted using an automatic planting machine and cultlvated according to the standard paddy field culture method applied in Ishikawa Prefecture. In the protoplast-derived plants of Fujisaka 5, about 25% of semi-1ethal segregants were observed among the flrst progenies of these plants (Pt2 plants). The agronomlc traits in Pt2 plants of Fujisaka 5 were recorded in viable and phenotypi-cally normal Pt2 plants. The common characteristics of the Pt2 plants were as follows, com-pared with the control: slight inc.rease of the number panicles, slight decrease of the number of spikelets per panlcle and similar grain yield. Progenies of the protoplast-derived plants of Nipponbare and Iwaimochi were phenotypically very uniform and stable, respectively. Culm length in the Pt2 plants of Nipponbare was uniform and slightly shorter than that of the control, whereas in the Pt2 plants of Iwaimochi, the culm was uniformly slightly longer. The viable Pt2 plants of Fujisaka 5 exhibited a considerably shorter culm, as compared with the control. The short culm of the Pt2 plants of Fujisaka 5 seems to be a heritable trait. The causes of the uniformity observed in the Pt2 plants of the three cultivars were dlscussed. The present results suggest that the progeny plants of the protoplast-derived rlce plants, except fcr Fujisaka 5, display a similar yielding ability and phenotypic uniformity to those of the control plants.

REGRESSIONS OF PROGENY PROOFS FOR CALVING EASE AND GROWTH ON TEST STATION PERFORMANCE OF CHAROLAIS AND HEREFORD BEEF BULLS

Performance records of 32 Charolais and 52 Hereford beef bulls tested at the Manitoba Bull Test Station for which progeny proofs were available (1984 Canadian Beef Sire Monitoring Program) were analyzed to determine if performance-tested bulls with progeny proofs were representative of the selected group of bulls which were eligible for sale (i.e, had station indexes of 95 or more) and to determine the regressions of progeny proofs on bull performance. The bull performance information included start and end of test weights, interim weights and gains, all expressed as deviations from their respective year-breed contemporary group means. This group of 84 bulls was not significantly different in test gains from the group of all bulls tested over the years 1976–1984 with station indexes of 95 or more. Regressions of progeny proofs for calving ease (CE, in score point units), preweaning gain (WG), yearling gain (YG) and postweaning growth (YG–WG) on bull weights and gains were estimated within breeds, weighting proofs by their prediction error variance. The only significant (P &lt; 0.05) regressions of CE proof on bull performance were for bull weights in the Charolais group. Regression coefficients of WG and YG proofs on bull weights and gains were similar in magnitude with the coefficients for the Hereford breed being significantly different from zero more often than those for the Charolais breed. Effective heritabilities and genetic correlations between bull performance traits and progeny traits were estimated and, for traits defined similarly on parent and progeny, the estimates were similar to literature values. Test station procedures seemed to be effective in that bull performance was an indicator of subsequent progeny performance. Key words: Beef cattle, performance test, progeny test, heritability

Variability in Quantitative Traits of Anther Culture-Derived Progenies

Variability in Quantitative Traits of Anther Culture-Derived Progenies

Genetic control of serum neutralizing-antibody response to rabies vaccination and survival after a rabies challenge infection in mice.

Quantitative differences in serum neutralizing-antibody (SNAb) responses to rabies vaccination and survival after a rabies challenge infection between two inbred mice strains, C3H/J and C57BL/6J, were shown to be under genetic control. A 99% confidence limit calculated from the SNAb response titers of 14 C57BL/6J mice resulted in an upper limit for the SNAb response titer of C57BL/6J mice at 50.63. A SNAb titer less than or equal to 50.63 in response to rabies vaccination was assigned the phenotype of hyporesponder, and a SNAb titer greater than 50.63 in response to rabies vaccination was assigned the phenotype of hyperresponder in this study. The hyper-SNAb response to rabies vaccination and the higher frequency of survival after rabies challenge infection behave as Mendelian dominant alleles in F1 hybrids (C3H/J X C57BL/6J) and backcross (BC) (F1 [C3H/J X C57BL/6J] X C57BL/6J) progeny. Both a relatively hyper-SNAb response and a higher frequency of vaccine-inducible survival phenotypes occur in C3H/J mice. On the other hand, both the relatively hypo-SNAb response and a lower frequency of vaccine-inducible survival phenotypes behave as Mendelian recessive alleles and occur in C57BL/6J mice. C3H/J mice are H-2 Kk, and C57BL/6J mice are H-2 Kb. All three phenotypic traits (H-2 type, SNAb response, and survival after rabies challenge infection) segregate as independent (unlinked) monogenic traits in BC progeny (F1 [C3H/J X C57BL/6J] X C57BL/6J). The genetically controlled survival trait is inducible by rabies vaccination, but SNAb response is not a parameter that measures successful vaccine induction of preexposure protection from a rabies challenge infection in the BC progeny. The essential role of vaccination in developing preexposure protection in genetically responsive mice is confirmed, but indicates that in vitro measurements other than SNAb titers need to be developed to identify mice that have failed to achieve preexposure protection by rabies vaccination. This study confirms Lodmell's findings (D. L. Lodmell and B. Chesebro, J. Virol. 50:359-362, 1984; D. L. Lodmell, J. Exp. Med. 157:451-460, 1983) that susceptibility to rabies infection is genetically controlled in some mice strains. Additionally, this study indicates that conventional rabies vaccination even with more potent vaccines may not induce protection from infection in some genetically susceptible individuals.

The development of male reproductive traits in progeny of Merino strains of different reproductive performance

Rams of the control South Australian Merino (Bungaree) (Bu) and of the highly fecund Booroola (Bo) and Trangie Fertility (TF) Merino strains were mated to Bu ewes to produce Bu, 1 2 Bo and 1 2 TF experimental progeny. Testicular volume, preputial adhesion score, the percentage of rams with spermatozoa, semen volume and density and components of mating performance were examined periodically between 5 and 15 months of age in the ram progeny. The 1 2 TF and 1 2 Bo outperformed the Bu in all traits; differences were most obvious in testicular volume, penis adhesion score, the percentage of rams with spermatozoa and semen density. Differences also existed between the 1 2 Bo and 1 2 TF ; significant differences occurred at least once during the study period in all traits except testicular volume and the components of mating performance. Most of the differences between the three experimental groups were evident at 5 months and some were still evident at 15 months of age. The ranking of strains on male development ( Bu 1 2 Bo s 1 2 TF ) was dissimilar to that already reported for female performance ( Bu s 1 2 TF 1 2 Bo ) and it is suggested that this inconsistency resulted from a gene of large effect influencing female performance but not male performance of the 1 2 Bo . A preliminary assessment, across strains, of the association between male traits and the reproductive performance of female relatives is provided.

Relationship between central performance test for growth in Hereford bulls and growth and carcass traits of progeny

ABSTRACTFour central performance tests of growth in Hereford bulls from about 10 to 19 months of age on pasture were conducted in New Zealand. From the 100 bulls performance tested 63 were representatively sampled, including bulls with high and low performance test rankings, and progeny tested in dairy herds. Crossbred progeny were purchased from the dairy herds at 3 to 4 months of age, assembled in one location and reared together on pasture for 14 to 15 months prior to slaughter. Regressions of progeny growth and carcass traits on a number of different performance traits for growth of their sires were in almost all cases not statistically significant. The effective heritability, from offspring-sire regression, was 0·07 (s.e. 0·05) for final live weight and 009 (s.e. 0·06) for post weaning gain from about 200 to 550 days of age. It is concluded that central performance tests, as presently conducted in New Zealand, are of limited value for ranking breeding values of bulls for growth. Possible reasons for these results are discussed. It is suggested that pre-test environmental effects and age at the start of the central test are critical factors.