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The aim of this study was to estimate genetic parameters for BW of Angus cattle up to 5 yr of age and to discuss options for including mature weight (MW) in their genetic evaluation. Data were obtained from the American Angus Association. Only records from herds with at least 500 animals and with >10% of animals with BW at ≥ 2 yr of age were considered. Traits were weaning weight (WW, n = 81,525), yearling weight (YW, n = 62,721), and BW measured from 2 to 5 yr of age (MW2, n = 15,927; MW3, n = 12,404; MW4, n = 9,805; MW5, n = 7,546). Genetic parameters were estimated using an AIREML algorithm with a multiple-trait animal model. Fixed effects were contemporary group and departure of the actual age from standard age (205, 365, 730, 1,095, 1,460, and 1,825 d of age for WW, YW, MW2, MW3, MW4, and MW5, respectively). Random effects were animal direct additive genetic, maternal additive genetic, maternal permanent environment, and residual. Estimates of direct genetic variances (kg(2)) were 298 ± 71.8, 563 ± 15.1, 925 ± 52.1, 1,221 ± 65.8, 1,406 ± 80.4, and 1,402 ± 66.9; maternal genetic variances were 167 ± 4.8, 153 ± 6.1, 123 ± 9.1, 136 ± 12.25, 167 ± 18.0, and 110 ± 14.0; maternal permanent environment variances were 124 ± 2.9, 120 ± 4.3, 61 ± 7.5, 69 ± 11.9, 103 ± 15.9, and 134 ± 35.2; and residual variances were 258 ± 3.8, 608 ± 8.6, 829 ± 34.2, 1,016 ± 38.8, 1,017 ± 52.1, and 1,202 ± 63.22 for WW, YW, MW2, MW3, MW4, and MW5, respectively. The direct genetic correlation between WW and YW was 0.84 ± 0.14 and between WW and MW ranged from 0.66 ± 0.06 (WW and MW4) to 0.72 ± 0.11 (WW and MW2). Direct genetic correlations ranged from 0.77 ± 0.08 (YW and MW5) to 0.85 ± 0.07 (YW and MW2) between YW and MW, and they were ≥ 0.95 among MW2, MW3, MW4, and MW5. Maternal genetic correlations between WW and YW and MW ranged from 0.52 ± 0.05 (WW and MW4) to 0.95 ± 0.07 (WW and YW), and among MW they ranged from 0.54 ± 0.14 (MW4 and MW5) to 0.94 ± 0.07 (MW2 and MW3). Genetic correlations suggest that a genetic evaluation for MW may be MW2-based and that including BW from older ages could be accomplished by adjusting records to the scale of MW2.

The study aimed at estimating variance components of racing ability traits in thoroughbred horses as a contribution to defining the breeding objective for this breed. Data collected were 12 143 placings at finish (square root) and 8641 earnings (log) won by 1414 horses running in 1693 races over the period of 1998-2001. Age of horses ranged from 2 to 5+ years, and the distances were from 1000 to 3200 m. Horses were from 11 state stables, from private breeders (one collective group), and from foreign breeding (another collective group within the factor ÔbreederÕ). Variance components were estimated by the residual maximal likelihood (REML) method. Statistical analysis accounted for fixed effects of year, age, race, breeder (optional), sex, weight carried and distance, and for the random effects of rider, permanent environment, and animal additive genetics. Pedigrees were at least three generations deep. When breeder effect was excluded from the model, heritability coefficients were 0.12 and 0.18, repeatability 0.23 and 0.34 for earnings and placings at finish, respectively.

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This study aimed to develop a methodology for using ultrasonic technology (USG) to record eggshell thickness for selection of layers. Genetic correlations between eggshell strength and its thickness have been reported to be around 0.8, making shell thickness a selection index candidate element. Applying ultrasonic devices to measure shell thickness leaves an egg intact for further handling. In this study, eggs from 2 purebred populations of Rhode Island White (RIW) and Rhode Island Red (RIR) hens were collected on a single day in the 33rd week of the farm laying calendar from 2,414 RIR and 4,525 RIW hens. Beginning from the large end of the egg, measurements were taken at 5 latitudes: 0º (USG0), 45º (USG45), 90º (USG90), 135º (USG135), and 180º (USG180). To estimate the repeatability of readings, measurements were repeated at each parallel on 3 meridians. Electronic micrometer measurement ( EMM: ) were taken with an electronic micrometer predominantly at the wider end of eggs from 2,397 RIR and 4,447 RIW hens. A multiple-trait statistical model fit the fixed effect of year-of-hatch × hatch-within-year, and random effects due to repeated measurements (except EMM) and an animal's additive genetic component. The shell was thinnest in the region where chicks break it upon hatching (USG0, USG45). Heritabilities of shell thickness in different regions of the shell ranged from 0.09 to 0.19 (EMM) in RIW and from 0.12 to 0.23 (EMM) in RIR and were highest for USG45 and USG0. Because the measurement repeatabilities were all above 0.90, our recommendation for balancing egg strength against hatching ease is to take a single measurement of USG45. Due to high positive genetic correlations between shell thickness in different regions of the shell its thickness in the pointed end region will be modified accordingly, in response to selection for USG45.

Abstract. The results of this study constitute a part of a project aiming at developing a cross-breed suitable for an extensive rearing system, utilising local biodiversity. Hybrids from mating a commercial broiler's male component (C) with Green-legged Partridgenous (GP) or Sussex (Sx) hens were compared with Cobb broilers. The study included 720 chickens of 3 genetic groups. Up to the third week of age, all birds were fed with balanced mixtures recommended for broiler chickens. From the fourth week, the mixture was weekly reduced by 10 % for the birds kept extensively (E). The deducted part was replaced with wheat bran, and from the seventh week with wheat. E groups had access to runs and received green fodder. Birds were slaughtered in 12th week of life. Carcass yield, giblets and proportion of carcass elements were estimated along with meat traits. The body weight at the 6th, 9th, 12th week of rearing and dissection results indicated a good suitability of Cobb chickens for an extensive rearing system. Hybrids were characterised by a considerably smaller proportion of breast muscle and slightly bigger of thighs and drumsticks, compared with Cobb, which could result from their greater motor activity. Results obtained by C × Sx and C × GP chickens, such as final body weight, proportions of abdominal fat and carcass elements, and appropriate value of meat traits, point at the usefulness of these hybrids as a meat-type chicken under extensive housing conditions. Darker colour of chicken meat, derived from C cocks and Sx or GP hens crossbred, can constitute an indicator for their carcasses' identification on the market.

The purpose of this study was to estimate correlations between purebred and F1 crossbred performance to verify the appropriateness of current models used in multibreed selection. Records on birth weight (WB) and weaning weight (WW) from purebred Limousins (LIM) and Limousin × Angus progeny (F1) were used to estimate genetic parameters using a multiple-trait (purebred and F1 weights were different traits) approach. For WB, there were 148,647 records for LIM and 17,981 for F1, and for WW, there were 81,585 records for LIM and 21,778 for F1. The fixed effect in models for LIM and F1 animals was contemporary group. Random effects for LIM animals were direct genetic, maternal genetic, and maternal permanent environment effects. Random effects for F1 were sire and dam. The pedigree for Angus dams used for crossing was unavailable and therefore these dams were assumed unrelated. The direct h2 estimates (SE) for purebred animals were 0.41 (0.05) and 0.24 (0.02) for WB and WW, respectively. For F1, the same estimates were 0.22 (0.09) and 0.32 (0.05). Genetic correlations estimates between purebreds and crossbreds were 0.84 (0.07) and 0.64 (0.18) for WB and WW, respectively. The genetic correlation for WW estimated in this study suggests that F1 and purebred information for this trait should not be treated, genetically, as the same trait due to different genetic effects molding it. However, the genetic correlation for WB was much higher, indicating that this trait in purebreds and F1 is essentially the same trait.