Direct Additive Effects Research Articles

Estimativas de (Co)Variâncias e Tendências Genéticas para Pesos em um Rebanho Canchim

Os objetivos deste trabalho foram obter estimativas de (co)variâncias e estimar a tendência genética para os pesos ao nascimento (PN), à desmama (PD) e a um ano de idade (P12) em um rebanho da raça Canchim. Foram utilizados dados de 6.517 animais, nascidos de 1953 a 1996, para estimar os valores genéticos pelo método da máxima verossimilhança restrita livre de derivadas, empregando-se um modelo que incluiu os efeitos fixos de grupo de contemporâneos (ano/época de nascimento/sexo do bezerro) e a covariável idade da vaca ao parto (efeitos linear e quadrático) e os efeitos aleatórios genéticos direto e materno e de ambiente permanente. Foram estimadas tendências genéticas para os efeitos aditivos diretos, maternos e do total maternal, pela regressão ponderada das médias anuais (ou de gerações) dos valores genéticos diretos, maternos e do total maternal sobre o ano de nascimento (ou geração) dos animais. As estimativas de herdabilidade direta foram iguais a 0,39; 0,48; e 0,63 para PN, PD e P12, respectivamente, enquanto as estimativas de herdabilidade materna foram, na mesma ordem, 0,03; 0,04; e 0,05, respectivamente. As tendências genéticas diretas anuais foram iguais a 0,046; 1,336; e 1,619 kg para PN, PD e P12, respectivamente, representando cerca de 0,13; 0,66; e 0,75% das médias do rebanho. Por geração, as tendências foram, na mesma ordem, 0,269; 7,715; e 9,599 kg, respectivamente. As tendências genéticas maternas e do total maternal foram, em geral, lineares e positivas. Os resultados mostraram que os critérios de seleção utilizados resultaram em progresso genético para PN, PD e P12, contudo, o progresso obtido ficou bem aquém do possível.

Antioxidative Effect of Maillard Reaction Products Added to Turkey Meat During Heating by Addition of Honey

ABSTRACT: Antioxidative effect of honey‐lysine Maillard reaction products (MRPs) was verified in a linoleic acid emulsion and a separate study was conducted comparing the antioxidative effects of direct honey addition to addition of preformed MRPs to meat. Antioxidative effects were measured using the TBA analysis and hexanal content in turkey. Antioxidative effects increased with increasing levels of MRP or honey addition to meat. Addition of honey to meat had a greater antioxidative effect than adding synthesized MRP to turkey. It is possible that meat with honey added had a greater antioxidative effect compared to MRP addition due to a better dispersion or solubility of the MRP formed in meat during heating.

Genetic parameters of weights, ultrasonic muscle and fat depths, maternal effects and reproductive traits in Welsh Mountain sheep

AbstractGenetic parameters of weight traits, ultrasonic fat and muscle depths, maternal effects and reproductive traits of Welsh Mountain sheep were estimated based on analyses of data from the nucleus flock of a cooperative breeding scheme. The traits analysed were 12 week weight (TW, no. = 11201), mature weight (MW, no. = 2376), weight at scanning (SW, no. = 1022), muscle depth (SM, no. = 1024), fat depth (SF, no. = 1024), litter weaning weight (LW, no. = 3445) and litter size (LS, no. = 3445). (Co)variance components were estimated in univariate and bivariate animal models. Heritability estimates from univariate analyses were 0.16, 0·49, 0·29, 0·24, 0·22, 0·20 and 0.15 for TW, MW, SW, SF, SM, LW and LS respectively. Genetic correlations among the weight traits were high. There was no detectable correlation between SF and SM. SF and SM were strongly correlated with SW but not with the other weight traits. LW was strongly correlated with MW and SW but not with TW, although the latter analysis was inconclusive. Maternal heritability was similar (0·11) for the univariate analysis of TW and all bivariate analyses involving TW (except for TW v. LW). The permanent environmental effect of dam was generally low (0.02 to 0.04) whilst litter effects were generally high (0·20 to 0·23). The correlation between direct and maternal genetic effects for TW were generally small and non-significant. The maternal genetic effect for TW was moderately correlated with the direct additive effect for MW and SW but was not significantly correlated with the direct additive effect for LS, SM or SF. A very large positive correlation was found between the maternal genetic effect for TW and the direct additive effect for LW. The implications of the results are discussed in the context of selection indices for Welsh Mountain sheep.

Maternal effects on traits measured during postweaning performance test of swine from four breeds.

The objective of this study was to investigate the importance of maternal genetic effects on postweaning performance traits of Yorkshire, Landrace, Duroc, and Hampshire breeds of swine. Data consisted of performance test records collected in a commercial swine operation from 1992 to 1999. Boars from 60% of the litters were culled at weaning based on a combination of maternal and performance indexes that differed by breed. Remaining boars and all females were grown to 100 d of age. At this time all pigs were weighed (WT100) and selected for testing using recalculated breed-specific indexes (n = 15,594, 55,497, 12,267, and 9,782 for Landrace, Yorkshire, Duroc, and Hampshire, respectively). All pigs were weighed at the end of the 77-d test, and backfat (BF) and loin eye area (LEA) were measured over the 12th rib by ultrasound. Average daily feed intake was calculated for boars, and ADG was calculated for all animals. Genetic parameters were estimated for each breed and trait using multiple-trait DFREML procedures. Fixed effects were contemporary groups and either initial or final test age as a covariate. Four models were examined. Model 1 included only the additive genetic effect of the animal. Model 2 added the common litter environmental effect; Model 3 added the maternal genetic value assumed to be uncorrelated with additive genetic effects. Model 4 was the same as Model 3 with additive and maternal genetic effects assumed to be correlated. All models were two-trait models with WT100 as the second trait. Ratios of likelihoods were used to compare models. Maternal effects were important (P < 0.05) for WT100, ADG, ADFI, LEA, and BF in Landrace; for WT100, ADG, LEA, and BF in Yorkshire; for WT100 and ADG in Duroc, and for WT100 in Hampshire. Estimates of heritabilities for direct additive effects using the appropriate model for ADG, ADFI, LEA, and BF were 0.28, 0.34, 0.48, and 0.63 for Landrace; 0.26, 0.31, 0.39, and 0.65 for Yorkshire; 0.14, 0.20, 0.26, and 0.35 for Duroc; and 0.17, 0.23, 0.25, and 0.31 for Hampshire, respectively. Heritability estimates for maternal genetic effects for ADG, ADFI, LEA, and BF were 0.02, 0.05, 0.06, and 0.07 for Landrace and 0.02, 0, 0.04, and 0.06 for Yorkshire, respectively. They were zero for all traits except ADG (0.03) in Duroc and for all traits in Hampshire. Maternal effects may need to be considered in genetic evaluation of performance traits in some breeds of swine.

Maternal effects on weight and ultrasonically measured traits of lambs in a small closed Suffolk flock

Early growth and ultrasonically measured muscle and fat depths (FD) are commonly used as selection criteria for the genetic improvement of meat species. Maternal effects on these traits have been recognised. This paper investigates how direct additive, maternal additive and maternal environmental effects influence early growth ( n=892) and carcass traits ( n=829) in lambs from a closed 100-ewe flock by fitting a series of mixed models, using a derivative-free maximum likelihood algorithm. These models included different combinations of the direct and maternal effects and some interactions between them. Maternal effects were found to influence all traits; birth weight (BWT), adjusted 8-week weight (8WT), adjusted 16-week weight (16WT), weight at scanning (SWT), muscle depth (MD) and FD. For the weight traits, the size of the maternal genetic effect declined with increasing age of the lamb. The direct genetic and maternal environmental effects remained constant at all ages studied. Maternal effects on FD and MD were environmental in origin. A high (negative) correlation was found between the direct and maternal genetic effects for lamb weight. This was particularly high (−0.95) for 8WT. These results indicate that genetic selection schemes for early weight and carcass traits should utilise models which account for more than just the direct additive effects. Failure to do so will lead to an overestimation of the genetic progress and will increase the chances of making sub-optimal selection decisions.

Genetic and phenotypic parameters for early growth traits in Emirati goat

The Emirati goat is the most common native breed of the United Arab Emirates adapted to the harsh environment. The data used in the present study were collected from a conservation flock at the Faculty of Agricultural Sciences Experimental Station. The traits recorded were body weights at birth (BWT), 30 days (WT30) and weaning weight (WWT), and average daily gains for the periods 0–30 (ADG1), 30–90 (ADG2) and 0 to weaning (ADG3) days of age. Season of birth, type of birth or rearing, sex of kid and dam age at kidding were the environmental factors investigated. Genetic parameters, and phenotypic and genetic correlations were estimated by REML procedures. By ignoring or including maternal genetic or environmental effects, five different models of analysis were fitted in order to determine the most effective model for each trait. Additive maternal effect was important ( P<0.05) for BWT, when compared with a model containing only additive direct effects. Inclusion of maternal permanent environmental effect provided a better fit ( P<0.05) for WT30, WWT and ADG1. Estimates of direct heritability from the most appropriate models were 0.18 for BWT, 0.16 for WT30, 0.32 for WWT, 0.11 for ADG1, 0.09 for ADG2 and 0.42 for ADG3. The estimates of genetic and phenotypic correlations were high and showed no genetic antagonisms among the growth traits analyzed. It can be concluded that maternal effects have to be accounted for when estimating genetic parameters for BWT, WT30, WWT and ADG1.

Genotype by environment interactions in lamb weight and carcass composition traits

AbstractThe systematic use of the same genotype in several different environments provides information that can be used to estimate genotype by environment interaction (G ✕ E) variances and parameters. Data from the UK Suffolk Sire Referencing Scheme Ltd were used to investigate a range of sire and dam by environment interactions in lamb weight (at 8 weeks and scanning) and body composition traits (muscle and fat depth). These interactions were calculated in a DFREML mixed model containing direct additive, maternal additive, maternal environmental random variance components and the covariance between direct and maternal additive effects. Sire interactions with year, flock and flock-year and dam effects within and between litters were investigated. The addition of all G ✕ E (co)variance components resulted in an improved fit of the model for all traits. Sire interactions accounted for between 2 and 3% of the phenotypic variance in all traits, usually at the expense of both additive effects. Maternal litter environmental variance components ranged from 10% (fat depth and muscle depth) to 20% (8-week weight) of phenotypic variance. Most of this variation was found in the residual component of variance when the term was omitted from the model. When fitting sire G✕ E components in a model the covariance between direct and maternal additive genetic effects, as a proportion of phenotypic variance, was reduced to a low level (from –0·36 to –0·08 for 8-week weight). Genotype by environment interactions form a significant source of variation in lamb growth and composition traits and reduce the high negative correlation between additive effects found previously in these traits.

Look ahead mate selection schemes for multi-breed beef populations

AbstractLook ahead mate selection (LAMS) schemes have been proposed to improve longer-term genetic merit when both selection and crossbreeding are important. We investigate the performance of a LAMS scheme which includes both predicted progeny merit and predicted grandprogeny merit in a mate selection index (MSI). Simulation of a multi-breed beef population, with additive breeding values, direct and maternal breed effects and direct and maternal heterosis was used to compare response from the LAMS scheme to mate selection on progeny merit only (PROG), selection on estimated breeding value (EBV) followed by random mating (RAND) and a structured crossbreeding scheme (CROSS). An additional strategy, LAMS + CO, was similar to LAMS but included a negative weighting on the coancestry of selected animals in the MSI to reduce inbreeding. LAMS gave up to 3% greater response in generation eight than PROG, 4·5% greater response than RAND, and 15% greater response than CROSS. Results from LAMS + CO were very similar to LAMS but inbreeding was 11% less from LAMS + CO at generation eight. The advantage of LAMS and LAMS + CO over PROG in later generations was hypothesized to be the result of positive assortative mating and greater use of maternal effects. Evidence to support the hypothesis of assortative mating was a positive significant correlation of EBVs of mates (sires and dams) in LAMS and LAMS + CO but not in PROG. Strategies PROG, LAMS and LAMS + CO all created closed populations of animals with optimum composite breed proportions.

Nuclear, cytoplasmic, and environmental effects on growth, fat, and muscle traits in suffolk lambs from a sire referencing scheme.

Maternal effects are an important source of variation in early growth and body traits in sheep but are often excluded from genetic analyses. Maternal additive genetic, maternal environmental, and cytoplasmic effects were investigated in a large Suffolk breeding scheme using a range of models involving different combinations of these effects with the direct additive genetic effect. Weights at 8 wk of age and at scanning (mean age 146 d) and ultrasonically measured muscle and fat depth were analyzed using an animal model on 55,683 (8-wk weight) and 28,947 (scanning traits) lamb records. Simple additive models always overestimated the heritability of all traits when compared to more complex models. The successive inclusion of maternal environmental, maternal genetic, and the covariance between direct and maternal additive effects in the model significantly improved the fit for almost all models and all traits, as indicated by a likelihood ratio test. Under the full model, the heritability of both weight traits was low (0.14 and 0.20 for 8-wk and scanning weight, respectively). The maternal additive and maternal environmental effects, as a proportion of the phenotypic variance, were similar (0.10 and 0.08 for 8-wk weight and 0.07 and 0.06 for scanning weight). The two scanning traits had higher heritabilities (0.29 and 0.27 for muscle depth and fat depth, respectively) with low levels of maternal genetic and maternal environmental variance. No evidence was found of a cytoplasmic effect on any of the traits studied under the full model. Breeding schemes for early growth and body traits in sheep should account for maternal effects in their genetic evaluations in order to improve their accuracy. The exact model to use will depend on the trait and individual circumstances of the scheme.

Estimation of Direct and Service Sire Genetic Parameters for Reproductive Traits in Yorkshire

Direct and service sire genetic parameters for total number of pigs born (TNB), number of pigs born alive (NBA), total pig weight at birth (TWB), and average pig birth weight (ABW) were estimated by DF-REML under a multiple trait animal model. Data on 3,078 litters of the Yorkshire from Jan, 1975 to Dec, 1998 at National Livestock Research Institute were obtained. The animal model included fixed contemporary group effects and random additive direct, service sire, and residual effects. Additive genetic relationships among animals were included. A separate relationship matrix for service sires and their sire was also included. Additive direct heritability estimates for TNB, NBA, TWB, and ABW were 0.19, 0.18, 0.25 and 0.39, respectively. Service sire heritability estimates for TNB, NBA, TWB, and ABW were 0.02, 0.01, 0.02 and 0.01, respectively. The genetic and phenotypic correlations of TNB with NBA estimated in this study were 0.81 and 0.81, respectively, and the genetic and phenotypic correlations of TNB with TWB estimated were 0.82 and 0.76, respectively. Results indicate that service sires account for 1 to 2% of the total variation for TNB, NBA, TWB, and ABW. Further investigation is needed to determine whether the service sire effect is primarily genetic or environmental. (Asian-Aust. J. Anim. Sci. 2002. Vol 15, No. 9 : 1232-1236)

Tendência Genética dos Efeitos Direto e Materno sobre os Pesos à Desmama e Pós-Desmama de Bovinos da Raça Tabapuã no Brasil

Os dados são relativos aos pesos de animais da raça Tabapuã, nascidos no período de 1959 a 1996 em várias regiões brasileiras. As observações foram analisadas com o objetivo de avaliar as mudanças genéticas aditivas diretas e maternas dos pesos padronizados para 205 (P205), 365 (P365) e 550 (P550) dias de idade. As estimativas dos componentes de (co) variância utilizadas no cálculo dos valores genéticos foram obtidas pelo método de máxima verossimilhança restrita livre de derivadas (REML), usando o aplicativo MTDFREML, cujo modelo continha os efeitos aleatórios aditivo direto, materno e de ambiente permanente, além dos efeitos fixos de grupo de contemporâneos (unidade da federação, fazenda, sexo, estação e ano de nascimento do animal) e a covariável idade da vaca ao parto (efeitos linear e quadrático). As tendências genéticas dos efeitos genéticos direto e materno foram estimadas pela regressão, ponderada, das médias anuais dos valores genéticos dos animais. As tendências genéticas dos efeitos direto no período estudado foram 0,134 ; 0,207, e 0,276 kg/ano, para P205, P365 e P550, respectivamente. Ainda para os três pesos, na mesma ordem, as estimativas das tendências genéticas maternas foram 0,019; -0,011; e -0,022 kg/ano. Em virtude da variação genética existente, os resultados observados estão bem aquém das mudanças possíveis.

Genetic parameters for growth traits of a local breed of sheep in the United Arab Emirates

Genetic parameters were estimated for purebred and crossbred lambs of a local breed using a single trait animal model. The traits recorded were: birth weight (BWT), weight at 30 days (WT30), weaning weight (WWT), average daily gain from 1 to 30 days (ADG1) and average daily gain from 30 to 90 days (ADG2). Five different animal models were fitted for each trait; all including additive direct genetic variance and various combinations of additive maternal and environmental maternal effects. The most appropriate model was chosen based on likelihood ratio tests. Additive maternal and permanent environmental effects were important (P &lt; 0·05) for birth weight in purebred and crossbred lambs, when compared with a model containing only additive direct effects. Inclusion of maternal permanent environmental effects provided a better fit (P &lt; 0·05) for weaning weight in purebred lambs than a model containing only additive direct effects. Estimates of heritability from the model containing additive direct, maternal effects and maternal permanent environmental effects, but not additive direct-maternal correlation, for combined purebred and crossbred lambs were 0·32 for BWT, 0·19 for WT30, 0·24 for WWT, 0·26 for ADG1 and 0·12 for ADG2. Estimates of additive maternal and maternal permanent environmental variances, respectively, as a proportion of phenotypic variance were 0·06 and 0·07 for BWT, 0·05 and 0·02 for WT30, 0·02 and 0·03 for WWT, 0·03 and 0·05 for ADG1 and 0·00 and 0·03 for ADG2. Estimates of direct-maternal correlation in subsequent analyses were significant and ranged from −0·16 to −0·95 for live weights and from −0·73 to −1·0 for daily gains. However, the very large negative correlations probably resulted from undefined non-genetic covariances as well as possible antagonistic genetic effects. These results indicate that it would be possible to improve growth traits in a local sheep breed through genetic selection.

Synthesis of MCM-48 via phase transformation with direct addition of NaF and enhancement of hydrothermal stability by post-treatment in NaF solution

The effects of direct addition of NaF to reacting solution and post-hydrothermal treatment in 0.1 N NaF solutions on phase transformation and hydrothermal stability of mesoporous material, M41S, have been investigated. Hydrothermally stable MCM-48 was successfully synthesized at 150 °C for various reaction times through phase transformation depending on the amount of NaF added to reacting solution. The results show that NaF as well as surfactant to silica ratio plays an important role for the formation of pure MCM-48. It was observed that pure MCM-48 appears to be formed easily but in limited region on ternary diagram such as SiO 2>45, HTA (surfactant) > 30 and NaF<20 in percent mole. The results also clearly show that a hydrothermal post-treatment in 0.1 N NaF solution as well as direct addition of NaF could further enhance the hydrothermal stability of MCM-48. XRD, 29 Si-MAS n.m.r. spectra, BET and TEM clearly support that a combined effect of NaF addition and hydrothermal post-treatment could maximize the hydrothermal stability of MCM-48.

The Impact of Residual Coagulant on the Respiration Rate and Sludge Characteristics of an Activated Microbial Biomass

Pre-precipitation is widely used in wastewater treatment to increase the removal of suspended solids (SS) and chemical oxygen demand (COD) in the primary sedimentation process. During pre-precipitation, a portion of the coagulant is removed from the treatment system in the primary settled sludge. However a residual amount will remain in the supernatant which is then treated by the secondary, biological treatment process. The effect of direct coagulant addition to the secondary biological treatment stage, known as simultaneous precipitation, is well documented but the effect of residual coagulant on secondary biological treatment as a result of pre-precipitation has received little attention. Jar tests were optimized with respect to SS, COD and phosphorus (P) removal at influent pH—between pH 7–8. Optimum dose was found to be 25 mgl −1 as metal ion for both alum and ferric sulphate coagulants. The residual metal concentration in the primary settled wastewater from the jar test experiments was identified as being 1.94 and 1.98 mg Fel −1 for ferric sulphate coagulants and 0.90 mg All −1 1 for alum. Primary effluent was fed to a settled activated microbial biomass to give total solids concentration of 2.0–2.5 g1 −1 . The impact of residual metal concentration on (i) respiration rate and COD removal and (ii) species diversity and floc structure were investigated. This paper presents the results of a laboratory-scale screening experiment undertaken to consider the impact of residual iron and aluminium coagulants on the secondary treatment process. Results identify a link between low level concentrations of coagulant, and reduction in microbial activity, changes in species diversity and floc morphology highlighting the importance of a bench/pilot-scale study.

Components of heterosis for growth traits and litter size in line crosses of mice after long‐term selection

Strains selected for 54 generations for large 8‐week weight (N8, S8), for small weight (N6, S6), for high 3–5‐week gain and low 8‐week weight (N1) as well as unselected randomly mated control strains (N9, S9) were crossed, and F1, F2 and both back crosses created. N strains are derived from a NMRI base, S strains from a synthetic four‐way cross among inbred lines. Heterosis for 8‐week weight (8‐ww) was some 6%, but 30% for 3–5‐week gain and it was on average negative (22%) for 5–8‐week gain. When epistatic effects were taken into account, it appeared that heterosis for 8‐ww was largely due to beneficial effects of non‐parental gene combinations, i.e. additive × additive epistatic effects were negative. These non‐parental combinations neutralized the mostly negative dominance effects. The latter were mostly positive for early gain but in all 9 line crosses negative for late gain. The digenic effects of the non‐parental origin were not large enough to balance the negative dominance effects for late gain, so that heterosis was negative. It appears therefore that early and late gain are affected by different sets of genes. Maternal additive effects on 8‐ww and early gain are smaller than direct additive effects but mostly of similar sign. For late gain there appears to be no connection with direct additive effects. Direct litter heterosis was almost 50% but much of this was due to positively acting recombinational gene combinations, while direct litter dominance was mostly negative. Maternal additive effects on litter size differed depending on whether they were estimated from dams with crossbred or with purebred litter. Heterosis was small in crosses between control strains. Heterosis caused by recombinant gene pairs should be amenable to improvement by selection.

Estimates of direct and maternal genetic effects for weights from birth to 600 days of age in Nelore cattle

Estimates of direct and maternal variance and heritability for weights at each week (up to 280 days of age) and month of age (up to 600 days of age) in Zebu cattle are presented. More than one million records on 200 000 animals, weighed every 90 days from birth to 2 years of age, were available. Data were split according to week (data sets 1) or month (data sets 2) of age at recording, creating 54 and 21 data sets, respectively. The model of analysis included contemporary groups as fixed effects, and age of dam (linear and quadratic) and age of calf (linear) effects as covariables. Random effects fitted were additive direct and maternal genetic effects, and maternal permanent environmental effect. Direct heritability estimates decreased from 0.28 at birth, to 0.12–0.13 at about 150 days of age, stayed more or less constant at 0.14–0.16 until 270 days of age and increased with age after that, up to 0.25–0.26. Maternal heritability estimates increased from birth (0.01) to a peak of 0.14 for data sets 1 and 0.07–0.08 for data sets 2 at about 180–210 days of age, before decreasing slowly to 0.07 and 0.05, respectively, at 300 days, and then rapidly diminished after 300 days of age. Permanent environmental effects were 1.5 to four times higher than genetic maternal effects and showed a similar trend.

Estimates of genetic parameters for direct and maternal effects on birth weight of local sheep in United Arab Emirates

Genetic parameters for birth weight were estimated for two sets of purebred and crossbred lambs in United Arab Emirates, using animal model methods. Data were analyzed by restricted maximum likelihood (REML). Five different animal models were fitted. Model 1 considered the animal as the only random effect. Models 2 and 3 included in addition to the additive direct effect of the animal, the additive maternal and the permanent maternal environmental effects, respectively. Model 4 fitted both the additive maternal and permanent environmental effects. Model 5 was the same as model 4, except that a covariance between the direct and the maternal additive effects was included. Estimates of direct heritability were substantially higher when maternal effects were ignored. Introducing the additive maternal effect to model 2 reduced the estimate of additive heritability by 28 and 14% of σ ̂ p 2 for the purebred and crossbred lambs, respectively. Estimates of additive direct and additive maternal heritabilities with model 4 were 0.10 and 0.33, and 0.45 and 0.10 for purebred and crossbred lambs, respectively. The correlation between direct and maternal genetic effects for the combined (purebred+crossbred lambs) data set was large and negative. These results indicate that in addition to additive direct effect, additive maternal effect for birth weight was important.

Direct and maternal genetic effects on birth and weaning traits in multibreed cattle data and predicted performance of breed crosses.

Direct and maternal additive effects and heterosis were estimated using data from straightbred Angus, Brahman, Charolais, Hereford, and four generations of rotational crosses among these breeds. Traits of interest were birth weight, Julian day of birth, average daily gain from birth to weaning, 205-d weight, and weaning weight per cow exposed. Complete data were available on 3,445 calves produced from 4,733 matings. Discrete generations of 4-yr duration were produced from 1970 through 1988. Brahman was included in each rotational crossbreeding system. Genetic effects were estimated by regression. Direct and maternal additive effects of Brahman, Charolais, and Hereford were estimated as deviations from Angus. Direct and maternal heterosis effects were assumed proportional to expected heterozygosity. The Brahman direct additive effect resulted in later-born calves (P < 0.01). Brahman, Charolais, and Hereford direct additive effects increased birth weight, and the Brahman maternal additive effect decreased birth weight compared with Angus (P < 0.05). Charolais direct and maternal additive effects were greater than Angus for average daily gain and 205-d weight (P < 0.01). The Hereford maternal additive effects on average daily gain and 205-d weight were less than those of the other breeds (P < 0.01). Breed combinations including Brahman had greater direct heterosis for birth weight, average daily gain, and 205-d weight than other combinations (P < 0.01). Angus, Charolais, and Hereford direct additive effects on weaning weight per cow exposed were greater than Brahman (P < 0.05). Predicted average daily gain, 205-d weight, and weaning weight per cow exposed were, on average, greater in four-breed rotation systems than in three- and two-breed systems. Among two-breed rotation systems, predicted average daily gain and 205-d weaning weight were greatest for Charolais-Brahman and least for Angus-Hereford. Calves from the Angus-Charolais-Hereford system weighed less at weaning than any other three-breed combination. However, weaning weight per cow exposed from the Angus-Charolais-Hereford system was greatest among three-breed systems. Within three- and four-breed rotation systems, ranges in predicted birth and weaning weights among generations varied by up to 10.0 and 25.2 kg, respectively. The choice of breeds affects performance, and the sequence of their use may affect intergenerational variation in performance.

Form of Government, Administrative Organization, and Local Economic Development Policy

Recent theoretical work has applied transaction cost theories to the public sector. This article extends transaction cost theories of organization to an empirical examination of bureaucratic influences on local government development programs. Extant research has paid little attention to the role that administrative organizations, institutions, and bureaucracies play in the local development process. Administrative organization can shape development choices in two ways. First, form of government may have direct additive effects on development because professional public managers have different orientations, values, and career interests than elected executives. Second, form of government may have nonadditive or interactive effect by influencing levels of government responsiveness to exogenous economic, political, and bureaucratic demands. We estimate the influence economic forces and bureaucratic arrangements had on development program activity in 1989 after accounting for development programs in place five years earlier in the same cities. Our finding calls into question the causal inferences regarding the direct effects of administration on local development policy found in the literature. In addition, we find that the form of government mediates effects of administrative arrangements and economic forces on development policy. In particular, the influences of strategic planning on development policy were evident in council-manager cities, but not mayor council communities. This finding suggests that commitments to take certain actions and not others embodied in strategic plan may be less credible in the context of high power electoral incentives.

Breed and heterotic effects on postweaning traits in Altex and New Zealand White straightbred and crossbred rabbits.

Postweaning data from 1,111 straightbred and reciprocally crossbred rabbits were analyzed to evaluate Altex and New Zealand White (NZW) breeds for individual growth and litter traits. The Altex is a recently developed sire breed, whereas the NZW is a popular commercial dam breed. Individual fryer growth traits were weaning (28 d; WW) and market (70 d; MW) weights and ADG. Litter traits included litter size (LSW) and total weight of litter at weaning (LWW), 28 to 70 d total feed intake (LFI), feed efficiency (LFE = total litter gain/LFI), survival rate, and within-litter MW uniformity. Least squares models consisted of fixed effects of sire breed, dam breed, season of weaning, doe parity, two- and three-way interactions, and random effects of sire within sire breed, litter within sire x dam breed, and(or) residual error (depending on whether an individual or a litter trait was analyzed). Crossbreeding parameters (direct breed additive, maternal breed, and individual heterosis) were estimated. Altex sires increased WW, ADG, and MW by 40 g (P < 0.10), 2.5 g/d, and 152 g (P < 0.001), respectively. Individual growth traits were not significantly influenced by the maternal breed effect. Litter size at weaning and LWW means were numerically similar for Altex and NZW dams. Direct heterosis increased ADG (1.7 g/d; P < 0.01) and MW (66 g; P < 0.10). In straightbred Altex compared to NZW fryers, ADG and MW were increased by 3.6 g/d and 216 g, respectively (P < 0.001). In Altex (sire) x NZW (dam) crossbred compared to NZW straightbred fryers, WW and MW were heavier (55 and 218 g; P < 0.10 and < 0.001) and ADG was more rapid (4.2 g/d; P < 0.001). For litter traits, Altex compared to NZW sires increased LFI by 1.28 kg (P < 0.10). Individual crossbreeding parameters did not affect (P > 0.05) other litter traits. No relationship existed between breed type of fryer and survival status (chi2 = 2.81; P > 0.25). For litter traits, straightbred Altex had significantly greater LFI by 2.45 kg and increased LFE by 0.015 units relative to NZW. Combined direct breed additive and heterosis effects increased LFI by 1.84 kg (P < 0.05) in Altex (sire) x NZW (dam) crossbreds compared to NZW straightbreds. Also, 25% more Altex (sire) x NZW (dam) crossbred fryers were marketable (body weight > or = 1.8 kg) by 63 d of age than NZW straightbred fryers. These data suggest that crossing Altex bucks to NZW enhanced breeding efficiency of fryer growth performance.