Kleiber Ratio Research Articles

Feed efficiency metrics in growing pigs.

The objective of the present study was to quantify the interrelationships between different feed efficiency measures in growing pigs and characterize pigs divergent for a selection of these measures. The data set included data from 311 growing pigs between 42 and 91 d of age from 3 separate batches. Growth-related metrics available included midtest metabolic BW (BW), energy intake (EI), and ADG. Ratio efficiency traits included energy conversion ratio (ECR), Kleiber ratio (ADG/BW), relative growth rate (RGR), residual EI (REI), and residual daily gain (RDG). Residual intake and gain (RIG; i.e., a dual index of both REI and RDG) and residual midtest metabolic weight (RMW) were also calculated. Simple Pearson correlations were estimated between the growth and feed efficiency metrics. In litters with at least 3 pigs of each sex, pigs were separately stratified on each residual trait as high, medium, and low rank. Considerable interanimal variability existed in all metrics evaluated. Male pigs were superior to females for all metrics ( < 0.001) except for both BW and EI, where no sex differences were evident. Feed efficiency metrics improved as birth BW increased ( < 0.05) except for RGR, where the contrary was observed. Correlations between most growth and feed efficiency metrics were strong to moderate ( < 0.05). Low-REI pigs (i.e., more efficient) had lower EI and ECR and were superior for RIG ( < 0.001) compared with high- and medium-REI pigs. High-RDG pigs (i.e., more efficient) had greater BW gain and better ECR ( < 0.001) compared with medium- and low-RDG pigs. Residual EI and RIG were both superior ( < 0.001) in high-RDG pigs compared with medium- and low-RDG pigs. Energy conversion ratio, REI, and RIG were superior ( < 0.05) in high-RMW pigs (i.e., more efficient) compared with medium-RMW pigs. High-RIG pigs (i.e., more efficient) had lower EI ( < 0.01) and superior ECR for RDG and REI compared with medium- and low-RIG pigs. In general, most of the correlations among the feed efficiency traits investigated in this study were different from unity, indicating that each trait is depicting a different aspect of efficiency in pigs, although the moderate to strong correlations suggest that improvement in one trait would, on average, lead to improvements in the others. Pigs ranked as more efficient on residual traits such as REI consumed less energy for a similar BW gain, which would translate into an economic benefit for pig producers.

Genetic and phenotypic aspects of growth rate and efficiency-related traits in sheep

A large set of Baluchi sheep growth data collected at Abbasabad Sheep Breeding Station, Mashhad, Khorasan Razavi, Iran, was used to estimate phenotypic and genetic parameters for growth rate from birth to weaning (GRa), weaning to six months of age (GRb), and weaning to 12 months of age (GRc) and corresponding Kleiber ratios (KRa, KRb, KRc), efficiency of growth (EFa, EFb, EFc) and relative growth rate (RGRa, RGRb, RGRc). Genetic parameters were estimated by REML procedure fitting a series of six univariate animal models including various combinations of maternal effects. The most appropriate model for each trait was determined by the Akaike Information Criterion (AIC). In addition, a multi-variate analysis was done to estimate (co)variance components between traits. Estimates of direct heritabilities (h2) were, respectively, 0.06, 0.03 and 0.10 for GRa, GRb, and GRc; 0.06, 0.06, and 0.05 for EFa, EFb and EFc; 0.07, 0.04 and 0.06 for KRa, KRb and KRc; and 0.07, 0.05 and 0.05 for RGRa, RGRb and RGRc. For traits measured in the pre-weaning growth phase, maternal genetic effect was significant. The estimates of maternal heritability (m2) for GRa, KRa, EFa and RGRa were 0.11, 0.11, 0.04 and 0.04, respectively. Estimates of the additive genetic coefficients of variation (CVA) were used as a measure of genetic variability and ranged between 1.68% (RGRa) and 14.67% (EFb). Genetic correlations between traits ranged from −0.81 (EFa-KRc) to 0.94 (ADGa-KRa) and phenotypic correlations ranged from −0.72 (KRa-EFc) to 0.99 (GRb-RGRb). Overall, results showed little additive genetic variation in growth rate or efficiency-related traits of Baluchi sheep, indicating little opportunity for genetic improvement of these traits in this breed through selection. In addition, significant maternal effects on traits related to pre-weaning growth indicated the importance of including maternal effects in genetic evaluation of traits measured early in life.

Estimated variance components and breeding values for pre-weaning growth criteria in Romney sheep

&lt;p class="abstrak2"&gt;This study was carried out to investigate variance components, direct heritability, maternal genetic parameters, estimated breeding values and factors affecting pre-weaning growth criteria of Romney sheep. Data were collected over the period from 2006 to 2012 with records of 4989 lambs descended from 76 rams and 2190 ewes of Romney sheep maintained at S. Island of New Zealand via Gene Marker Lab., Faculty of Agric. and Life Sci., Lincoln Univ., New Zealand. Results proved that genetic and non-genetic factors affecting studied criteria had significant effects (P&amp;lt;0.05). Genetic and environmental estimates of live body weights at birth (LBW), weaning (LWW) and Kleiber ratio (KR) were 0.20±0.074, 0.15±0.042 and 0.14±0.052 for direct heritability (h&lt;sup&gt;2&lt;/sup&gt;a±SE); 0.59±0.219, 0.41±0.023 and 0.08±0.002 for maternal heritability (h&lt;sup&gt;2&lt;/sup&gt;m±SE); 0.11684, 2.6378 and 0.27565 for additive variances (σ&lt;sup&gt;2&lt;/sup&gt;a), 0.34596, 7.1179 and 0.14532 for maternal variances (σ&lt;sup&gt;2&lt;/sup&gt;m); and 0.002395, 10.1262 and 0.509339 for permanent environmental variances (σ&lt;sup&gt;2&lt;/sup&gt;e), respectively. EBV’s of LBW, LWW and KR ranged from -0.555: 0.502, -1.554: 3.006 and -0.633: 0.242 direct, -0.863: 0.954, -4.942: 2.554 and -0.469: 0.179 maternal for rams, respectively; and -0.664: 0.830, -2.996: 4.586 and -1.651: 0.677 direct, 1.429: 1.142, -7.541: 4.920 and -1.223: 0.492 maternal for ewes, respectively. Results suggest the importance of considering the non-genetic factors in pre-weaning growth performance of lambs. Moderate heritability and positive coefficients of phenotypic and genetic correlation for studied criteria indicate to the possibility of improving them using traditional selection.&lt;/p&gt;

Genetic parameters for Kleiber ratio and its relation to other body weight traits in Nilagiri and Sandyno sheep

Kleiber ratio (KR) is an indicator of growth efficiency irrespective of body size. The trait was recommended as an efficient indirect selection criterion. The present study was done to estimate genetic parameters for KR and explore the possibility of its use as a selection criterion in Nilagiri and Sandyno sheep. KR for the pre-weaning (birth to 3-months) and post-weaning (3– 6, 6–9, 9–12 and 3–12 months) periods was studied. Pre-weaning KR was much higher than post-weaning KR in both the breeds. The mean pre-weaning KR for Nilagiri and Sandyno sheep was 14.37 and 14.52, respectively. All the post-weaning KR values were less than six. Animal model including or ignoring maternal effects was used to obtain REML estimates of (co)variances. The best model was chosen based on log-likelihood ratio test. Maternal effects and inbreeding were not significant for KR at any of the age intervals. Moderate estimates of heritability were obtained for pre-weaning KR in both the breeds. Among the post-weaning KR, the age interval from 3–6 months and 3–12 months showed moderate values in Nilagiri sheep. Post-weaning KR for Sandyno sheep showed negligible to low heritability estimates. The maximum heritability of 0.143 was for KR 3–6 months in Nilagiri sheep. In Nilagiri sheep, genetic correlation between pre-weaning KR and body weight traits ranged from 0.634 to 0.875. Similarly, in Sandyno sheep, the values ranged from 0.883 to 0.959. Thus pre-weaning KR could be used as a criterion for indirect selection to improve important body weight traits.

Genetic analysis and the estimates of genetic and phenotypic correlation of growth rates, Kleiber ratios, and fat-tail dimensions with birth to yearling live body weight traits in Makuie sheep.

Genetic parameter estimates of growth rates, Kleiber ratios, and fat-tail dimensions were aimed using 22, 253 records at the present study. The studied traits were average daily gain from birth to weaning, average daily gain from 9months of age to yearling, Kleiber ratio from birth to weaning, Kleiber ratio from 9months of age to yearling, fat-tail length, fat-tail width, and fat-tail thickness. Each trait was fitted by four different animal models, which are differentiated by including or excluding maternal effects. Beside the estimates of genetic and phenotypic correlation among the studied traits, the association of them with birth to yearling live body weights using series of bivariate animal models was investigated. The direct heritabilities were ranged from 0.04 to 0.20, which indicated a wide range of additive genetic variances of the traits. Genetic and phenotypic correlations between the main traits were ranged from -0.11 to 0.99 and -0.08 to 0.95, respectively. The results indicated that the traits could be improved by including them in the selection index due to their moderate to high heritability estimation.

Factors Affecting Pre-And Post-Weaning Kleiber Ratios and Genetic Parameters in Mehsana Goats

Factors Affecting Pre-And Post-Weaning Kleiber Ratios and Genetic Parameters in Mehsana Goats

Variance components and genetic parameters of growth traits and Kleiber ratio in Muzaffarnagari sheep

Estimates of (co)variance components and genetic parameters were obtained for birth weight (BW), weaning weight (WW), average daily weight gain from birth to weaning (ADG) and Kleiber ratio (KR) of Muzaffarnagari sheep maintained at the Central Institute for Research on Goats, Makhdoom, Mathura, India, over a period of 30 years (1976–2005). Records of 5835 lambs descended from 176 rams and 1703 ewes were used in the study. Analyses were carried out by restricted maximum likelihood (REML) fitting an animal model and ignoring or including maternal genetic or permanent environmental effects. Six different animal models were fitted for all traits. The best model was chosen after testing the improvement of the log-likelihood values. Direct heritability estimates were inflated substantially for all traits when maternal effects were ignored. Heritability estimates for BW, WW, ADG and KR were 0.15, 0.16, 0.15 and 0.13, respectively. Maternal genetic effects contributed only 12% of the total variance for birth weight. Estimates of fraction of variance due to maternal permanent environmental effects (c2) for BW, WW, ADG and KR accounted for 6–12% of the total phenotypic variance in this study. The estimates of the direct genetic correlation among studied traits were positive, ranging from 0.18 (BW–KR) to 0.98 (WW–ADG), whereas permanent maternal environmental correlations among traits varied from from 0.55 (BW–KR) to 0.99 (WW–ADG). The estimates of the phenotypic and environmental correlation between traits under study ranged from 0.10 to 0.99 and −0.05 to 0.99, respectively. Results suggest that maternal additive effect was only important for birth weight whereas permanent environmental maternal effects were important for other traits in our study. The moderate heritability estimates for early growth traits and Kleiber ratio of sheep in this study indicates that modest rates of genetic progress may be possible for these traits from selection under the prevailing management system.

Genetic parameter estimates for growth and reproductive traits in Lori sheep

Lori sheep is one of the well adapted and relatively heavy breeds in mountainous regions of Iran, primarily reared for mutton production. The current study was conducted to estimate the (co) variance components and genetic parameters by restricted maximum likelihood method using six univariate models for growth and four univariate models for reproductive traits. Data and pedigree information were collected at Agricultural Organization of Lorestan province, west of Iran from 2001 to 2012. Studied growth traits were birth weight (BW), weaning weight (WW), 6-month weight (6MW), average daily gain from birth to weaning (ADG0–3), average daily gain from birth to 6-month (ADG0–6), average daily gain from weaning to 6-month (ADG3–6), and corresponding Kleiber ratio (KR0–3, KR0–6, KR3–6). Reproductive traits were litter size at birth (LSB), litter size at weaning (LSW), litter mean weight per lambing (LMWL), litter mean weight per lamb weaned (LMWLW), total litter weight at birth (TLWB) and total litter weight at weaning (TLWW). Moreover, multivariate analyses were performed to estimate covariance between traits. Direct heritability estimates (h2a) for growth traits ranged from 0.000 (ADG0–3 and KR0–3) to 0.156 (6MW). Maternal heritability (h2m) decreased from 0.110 at birth to 0.022 at 6-month weight. The ratio of maternal permanent environmental variance to phenotypic variance (pe2) persisted into the post-weaning growth period and it was 0.115, 0.080, 0.087 and 0.081, for BW, ADG0–6, KR0–3 and KR0–6, respectively. Estimates of h2a for reproductive traits were significant for LSB, LSW, LMWL and LMWLW being 0.175, 0.213, 0.088 and 0.034, respectively, while TLWB and TLWW were more affected by the permanent environmental effects of ewes. Service sire effects (S2) were significant for LMWL. Genetic correlations between growth traits ranged from −0.425 (BW-KR0–3) to 1.000 (6MW-ADG0–3, 6MW-KR0–3, ADG0–3–ADG3–ADG3–6-KR0–3 and KR0–3–KR0–6), and phenotypic correlations ranged from −0.341 (ADG0–3–KR3−6) to 0.990 (6MW–ADG0−6). Genetic correlations between reproductive traits were higher than phenotypic ones, and ranged from −0.986 (LSB-LMWLW) to 0.999 (LMWLW-TLWB).

Selection for feed efficiency traits and correlated genetic responses in feed intake and weight gain of Nellore cattle1

The objectives of this study were to estimate genetic parameters for indicator traits of feed efficiency and to recommend traits that would result in better responses to selection for increased weaning weight (weaning weight adjusted to 210 d of age [W210]), ADG, and metabolic BW (BW(0.75)) and lower DMI. Records of W210 from 8,004 Nellore animals born between 1978 and 2011 and postweaning performance test records from 678 males and females born between 2004 and 2011 were used. The following feed efficiency traits were evaluated: G:F, partial efficiency of growth (PEG), relative growth rate (RGR), Kleiber's ratio (KR), residual feed intake (RFI), residual weight gain (RWG), and residual intake and gain (RIG). Covariance and variance components were estimated by the restricted maximum likelihood method using multitrait analysis under an animal model. Estimates of genetic gain and correlated responses were obtained considering single-stage and 2-stage selection. Heritability estimates were 0.22 ± 0.03 (W210), 0.60 ± 0.08 (DMI), 0.42 ± 0.08 (ADG), 0.56 ± 0.06 (BW(0.75)), 0.19 ± 0.07 (G:F), 0.25 ± 0.09 (PEG), 0.19 ± 0.07 (RGR), 0.22 ± 0.07 (KR), 0.33 ± 0.10 (RFI), 0.13 ± 0.07 (RWG), and 0.19 ± 0.08 (RIG). The genetic correlations of DMI with W210 (0.64 ± 0.10), ADG (0.87 ± 0.06), and BW(0.75) (0.84 ± 0.05) were high. The only efficiency traits showing favorable responses to selection for lower DMI were G:F, PEG, RFI, and RIG. However, the use of G:F, PEG, or RFI as a selection criterion results in unfavorable correlated responses in some growth traits. The linear combination of RFI and RWG through RIG is the best selection criterion to obtain favorable responses in postweaning growth and feed intake of Nellore cattle in single-stage selection. Genetic gains in feed efficiency are expected even after preselection for W210 and subsequent feed efficiency testing of the preselected animals.

Identification of QTL for live weight and growth rate using DNA markers on chromosome 3 in an F2 population of Japanese quail

The Japanese quail (Coturnix japonica) is an important agricultural species and is an animal model for genetic researches. This study was conducted to identify quantitative trait loci (QTL) affecting live weight and growth rate on chromosome 3 in quail. Two strains of Japanese quail including wild and white were crossed reciprocally and F1 generation was created. The birds from F2 generation were measured for growth traits and all of 472 birds (8 pairs from the parental strains, 34 F1 birds and 422 F2 birds) were genotyped for microsatellite markers on chromosome 3. The results indicated chromosome wide significant QTL for hatching weight (P<0.01) and weight at 1, 2, 3 and 4weeks of age, average daily gain from hatch to 1, 1-2 and 3-4weeks of age and Kleiber ratio (P<0.05), an indirect criterion of feed efficiency. The highest QTL additive and imprinting effects (2.72 and 0.79% of the trait variation in the F2 population, respectively) were related to hatching weight. The identified QTL for this trait (at 7cM relative to the centromeric region of the chromosome) had significant interaction with sex and hatch (P<0.01). The dominance effect of QTL was significant (P<0.05) for bodyweight at one week of age accounting for 1.69% of the trait variation in the F2 population.

(Co)variance components and genetic parameters for growth rate and Kleiber ratio in fat-tailed Mehraban sheep

Abstract. The aim of the present study was to estimate (co)variance components and genetic parameters for average daily gain from birth to weaning (ADGa), weaning to 6 months (ADGb), weaning to 9 months (ADGc), 6 months to 9 months (ADGd) and corresponding Kleiber ratios (KRa, KRb, KRc and KRd) in Mehraban sheep. A derivative-free algorithm combined with a series of six univariate linear animal models was used to estimate phenotypic variance and its direct, maternal and residual components. In addition, bivariate analyses were done to estimate (co)variance components between traits. Estimates of direct heritability (h2) were 0.10, 0.11, 0.16, 0.09, 0.13, 0.13, 0.15 and 0.08 for ADGa, ADGb, ADGc, ADGd, KRa, KRb, KRc and KRd, respectively and indicate that in Mehraban sheep genes contribute very little to the variance of the growth rate and Kleiber ratio. Estimates of maternal heritability (m2) were 0.10, 0.08 and 0.05 for ADGa, KRa and KRb, respectively. Direct additive genetic correlations ranged from −0.32 (KRa-KRd) to 0.99 (ADGb-KRb) and phenotypic correlations ranged from −0.53 (ADGa- ADGd) to 0.99 (ADGa-KRa). Estimates of direct heritability and genetic correlations show that genetic improvement in efficiency of feed utilization through selection programmes is possible, though it would generate a relatively slow genetic progress.

Model comparisons and genetic parameter estimates of growth and the Kleiber ratio in Shal sheep

Abstract. Genetic and phenotypic parameters were estimated for lamb growth traits for the Shal sheep using an animal model. Data on lamb growth performance were extracted from available performance records at the Shal sheep Station in Qazvin, Iran. Studied traits were body weights of lambs at birth (BW), at 3 months of age as weaning weight (WW), 6 months weight (6MW), 9 months weight (9MW), yearling weight (YW), average daily gain from birth to weaning (ADG) and Kleiber ratio from birth to weaning (KR). Significant random effects for each trait were determined by fitting additive direct genetic effects, additive maternal effects, covariance between additive direct and additive maternal effects, maternal permanent environmental and maternal temporary environmental (common litter) effects under twelve animal models. Univariate analyses were carried out under the most appropriate model, determined by AIC test. Direct heritability estimates for BW, WW, ADG, KR, 6MW, 9MW and YW were 0.13, 0.19, 0.18, 0.05, 0.16, 0.18 and 0.19, respectively. Maternal additive genetic effects were fitted only for BW and WW; corresponding estimates of 0.12 and 0.10 obtained for maternal heritability of BW and WW, respectively. Maternal permanent environmental effects have low contribution in expression of KR and lead to estimates of 0.06 and 0.06 for maternal permanent environmental variance as a proportion of phenotypic variance (c2) of these traits, respectively. All pre-weaning traits, except KR, were affected by litter effects. The magnitude of ratio of common litter variance to phenotypic variance (l2) was 0.05, 0.12 and 0.14 for BW, WW and ADG, respectively. Direct genetic correlations were positive and ranged from 0.09 for KR-YW to 0.80 for WW-ADG; phenotypic ones ranged from 0.18 for KR-YW to 0.87 for WW-ADG.

Genetics and non-genetics parameters of body weight for post-weaning traits in Raini Cashmere goats

Genetic parameters were estimated for 6-month weight (W6), 9-month weight (W9), 12-month weight (W12), average daily gain from birth to 6 months old (ADG6), and Kleiber ratio at 6 months (KL6) traits using 6,442 records obtained from a Raini Cashmere goat flock. The parameters were estimated using the restricted maximum likelihood procedure and applying four animal models excluding or including maternal additive genetic and permanent environmental effects. Heritability estimates for W6, W9, W12, ADG6, and KL6, under the most appropriate model were 0.028, 0.26, 0.29, 0.02, and 0.25, respectively. The estimates of genetic and phenotypic correlations among W6, W9, W12, and ADG6 were high and ranged from 0.73 to 0.99. The estimates of genetic and phenotypic correlations among KL6 and others traits were negative and low. Thus, these estimates of genetic parameters may provide a basis for deriving selection indices for postweaning growth traits also low genetic correlation between growth traits with KL6, it is possible to increase efficiency in Raini kids by multitrait selection.

Consumo alimentar residual e sua relação com medidas de desempenho e eficiência e características in vivo da carcaça de cordeiros

Avaliou-se o consumo alimentar residual (CAR) e a conversão alimentar (CA) de 20 cordeiros, com o objetivo de estimar as correlações entre essas variáveis com medidas de desempenho e com características in vivo da carcaça. Os animais tiveram o consumo de MS (CMS) mensurado por 65 dias e foram pesados a cada 13 dias para obtenção do ganho médio diário (GMD). Foram considerados o peso vivo inicial (PVI), o peso vivo final (PVF), o peso metabólico (PM), o GMD, a taxa de crescimento relativo (TCR), a taxa de Kleiber (TK), a CA, o CMS e o CMS em percentual do PV (CMSPV). As avaliações de carcaça foram realizadas por ultrassom. O CAR se mostrou correlacionado com o CMS (+0,81), o CMSPV (+0,90) e a CA (+0,63). Correlações significativas foram encontradas entre CA e GMD; CA e TCR; CA e TK; e CA e PVI (-0,63, -0,74, -0,75 e +0,51, respectivamente). O CAR e a CA não se mostraram correlacionados com características de carcaça, e, da mesma forma, não houve diferença entre as classes de CAR para essas variáveis. Confirmou-se o potencial do CAR como medida de eficiência alimentar para cordeiros em confinamento, sem existência de relações com o ganho de peso e o tamanho corporal e sem alterações na composição da carcaça.

Factors affecting post-weaning average daily gain and Kleiber ratios in Malpura sheep

The objective of this study was to determine effect of environmental factors on estimates of post-weaning growth traits. Study suggested that as the age advances growth rate and feed conversion efficiency declines in Malpura sheep. Hence, for higher economic gain selection should be made at earlier age, preferably at 6 month. Rearing male lambs can be more profitable as they achieved higher growth and better feed conversion efficiency. For unbiased estimates of breeding values, correction factors for significant non-genetic factors must be incorporated.

The estimation of (co)variance components and genetic parameters for growth traits and Kleiber ratios in Malpura sheep of India

Objective of the present study was to estimate the genetic parameters and (co)variance components for different economic traits in Malpura sheep. The traits analyzed were birth weight (BWT), weaning weight (WWT), 6-month weight (6WT), average daily gain from birth to weaning (ADG1), average daily gain from weaning to 6-month (ADG2), average daily gain from birth to 6-month (ADG3), Kleiber ratio from birth to weaning (KR1), Kleiber ratio from weaning to 6-month (KR2) and Kleiber ratio from birth to 6-month (KR3). Six different animal models including or ignoring maternal genetic or permanent environmental effects were fitted for all traits. Akaike information criterion (AIC) was applied to determine the most appropriate model for each trait. For BWT, WWT, 6WT, ADG1, ADG2 and KR2 the model including permanent environmental effects due to ewe over direct genetic effects was the most appropriate. Model which included only direct genetic effects was the best model for ADG3, KR1 and KR3. Direct heritability estimates of 0.21, 0.24, 0.23, 0.23, 0.13, 0.22, 0.20, 0.12 and 0.23 were obtained for BW, WW, 6MW, ADG1, ADG2, ADG3, KR1, KR2 and KR3, respectively. Ratios of phenotypic variance due to maternal permanent environmental effects were 0.24, 0.07, 0.01, and 0.05 for BW, WWT, 6WT and ADG1, respectively. Estimates of direct genetic correlation were very low to high in magnitude and varied from −0.27 for BW–KR2 to 0.97 for ADG1–KR1. Estimates of phenotypic correlation were very low to high in magnitude and varied from −0.27 for WW–KR2 to 0.96 for ADG3–KR3. The moderate estimate of direct heritability for body weight, growth rate and Kleiber ratio suggests that Malpura sheep can be improved through selection for economic mutton production.

Random heterosis effects on genetic parameters, estimation of birth weight, and Kleiber ratio in a population admixture of Thailand goats

The objective of this study was to compare models for suitable genetic parameter estimation of birth weight (BWT) and Kleiber ratio (KR) in a population admixture of Thai native, Anglo-Nubian, and Saanen goats. The data set from 51 bucks and 700 does contained 3020 records of BWT and KR. Data were analyzed using five bivariate animal models with different breed effects (breed fractions of Thai native genetics (NF), breed combination groups (BCG), and genetic composition of Anglo-Nubian and Saanen). Random heterosis and dominance effects were considered when comparing models. The results indicated that accounting for breed effects as NF and BCG breed fractions of Thai native genetics and breed combination groups was not suitable and gave an incorrect ranking of animals for selection; fitting breed effect as the genetic composition of exotic breeds gave higher predictive ability. Incorporation of random heterosis effects could reduce upward bias in direct heritability, while fitting dominance slightly improved the accuracy of variance components estimates. In conclusion, the appropriate model for genetic evaluation of BWT and KR in a genetic admixture of Thai goats was fitting breed effects as the genetic composition of exotic breeds, together with random heterosis.

Growth and feed efficiency of range performance tested beef bulls in the arid sweet bushveld of South Africa

Data consisting of test performance records of 725 bulls was analysed to evaluate trends for growth and feed efficiency, and to determine environmental factors that influence growth of range performance tested bulls in the arid sweet bushveld of South Africa. Performance data were subjected to regression procedures to estimate parameters of the slope (β) and intercept (α) for average daily gain (ADG) and Kleiber ratio (KR). Mixed procedures were applied to test for sources of variation in ADG and KR. There was an increase of 3.481 g/day/year and 0.528 g/day/ year in ADG for Nguni and Bonsmara bulls, respectively. The ADG trends’ respective feed efficiency as reflected by KR was 0.093 and 0.059. Herd of origin and test-year were the sources of variation for ADG while the variation in KR was due to the herd of origin, test-year, start-age and start-weight. Results indicated a steady increase in ADG and KR for range performance tested bulls in the arid sweet bushveld.

Genetic mapping of quantitative trait loci affecting bodyweight on chromosome 1 in a commercial strain of Japanese quail

This study was conducted to identify quantitative trait loci (QTL) affecting growth on chromosome 1 in quail. Liveweight data were recorded on 300 progeny from three half-sib families created from a commercial strain of Japanese quail. Three half-sib families were genotyped for nine microsatellite loci on chromosome 1 and QTL analysis was conducted applying the least-squares interval mapping approach. Significant QTL affecting bodyweight at 3, 4, 5 and 6 weeks of age, average daily gain, and Kleiber ratio, an indirect criterion for feed efficiency, were mapped at 0–23 cM on chromosome 1. The detected QTL segregated in two of the three half-sib families and the size of the QTL effect ranged from 0.6 to 1.1 in unit of the trait standard deviation. This is the first report of liveweight QTL segregating in a commercial strain of Japanese quail.

Evidence of residual feed intake reranking in crossbred replacement heifers

The objective of the study was to examine whether residual feed intake (RFI) reranking exists between 2 consecutive periods in replacement heifers fed the same diet. The study collected feed intake and BW data from 190 crossbred heifers over a 3-yr period (61 in 2007, 68 in 2008, and 61 in 2009) during the winter-spring season. The heifers were fed a roughage-based diet (90% barley silage and 10% rolled barley grain) throughout the feeding trial, which was broken down into 2 feeding periods with ADG of 0.94 and 0.90 kg•d(-1) in the first and second periods, respectively. The RFI was calculated for the entire period using different models, which included ADG, mid-metabolic BW, body composition, and feeding activity. Gain:feed ratio and Kleiber ratio were also calculated. Rank correlations among the RFI calculated from different models were obtained, as well as rank correlations between the 2 feeding periods for the feed efficiency measures. Including body composition and feeding activity only improved the R(2) by 1 to 5%. The rank correlations among the different models were high (90 to 95%) for RFI calculated for the entire feeding period. However, the RFI calculated within the second feeding period had greater rank correlation than the RFI calculated from the entire feeding period. Compared with G:F and Kleiber ratio, RFI gave lesser reranking between periods 1 and 2. About 49% of the heifers maintained their RFI class, whereas 51% of the heifers had a different RFI class in period 2. Furthermore, 41% of the heifers changed their RFI in period 2 by <0.5 SD, whereas the rest of the heifers changed by ≥0.5 SD. These results indicate that reranking exists in heifers despite receiving the same diet in the 2 feeding periods and that the reranking may be more serious in heifers (28%) with extreme RFI performances in each period.