Kleiber ratios and growth curves of African Black and Red Neck ostrich breeds and their crossbreeds

The selection of animals with lower production costs can be achieved by using feed efficiency and growth curve information. Kleiber ratio (KR) is an alternative option for discriminating against the animals that have the greatest weight gain about their final weight. Alternative feed efficiency and growth curves for ostriches of the African Black (AB) and Red Neck (RN) breeds and their crossbreeds (CB) were investigated using KR and Gompertz equation. Univariate and multivariate analyses were used. The highest adult weight was identified in the RN and CB. AB was more precocious than the RN and CB individuals. Only AB animals reached 75% of their mature weight at one year of age. At 180 days, AB showed better KR. AB was different from the others, mainly for KR at 90 days and 180 days. Considering multivariate analysis, AB animals were different from the others, regardless of sex, mainly for KR at 90 days and KR at 180 days. Other subgroups separated the animals by sex. In a market preferring animals of minor structure (smaller cuts) and greater precocity, it would be suitable to opt for AB. When animals with greater body structure (larger cuts) are desired, males RN and CR is the best option, however, it will be slaughtered with greater age and lower value for KR (may generate a bigger production cost ). It is possible to obtain animals with precocity and high KR, being well represented by the AB breed.

Evaluating animal models comprising direct and maternal effects associated with growth rates and the Kleiber ratio in Harnali sheep

Summary The present work evaluated animal models comprising direct and maternal effects to estimate (co)variance components and genetic parameters of growth rates and Kleiber ratio in Harnali sheep. The information on pedigree and targeted traits of 1862 lambs born to 144 sires and 591 dams was collected for the period from 1998 to 2018. The traits studied were average daily gain from birth to 3 months of age (ADG1), 3 months to 6 months of age (ADG2), and 6 months to 12 months of age (ADG3) and their corresponding Kleiber ratios as KR1, KR2 and KR3, respectively. The statistical methods included the general linear model for analyzing the effects of fixed factors and animal models for deriving variance components for targeted traits. According to best model evaluated on the basis of likelihood ratio test, the estimated direct heritability was low in magnitude and ranged from 0.04 to 0.14. Direct heritability estimates for ADG1, ADG2, ADG3, KR1, KR2 and KR3 were 0.06, 0.14, 0.05, 0.04, 0.11 and 0.05, respectively. The maternal genetic effects contributed (4–7%) significantly for ADG1, KR1 and KR2 traits. The genetic correlations ranged from −0.35 ± 0.11 (ADG1-KR2) to 0.98 ± 0.01 (ADG2-KR2 and ADG3-KR3) and phenotypic correlations ranged from −0.36 ± 0.02 to 0.98 ± 0.01 for ADG1-KR2 and ADG2-KR2, respectively. The significant maternal effects along with low levels of direct effects for average daily gain and Kleiber ratio at different age group should be considered while setting selection and managerial strategies to achieve anticipated growth rates in Harnali sheep.

Genetic and non-genetic parameters for growth traits and Kleiber ratios in Dorper x indigenous sheep

Genetic improvement program will only be successful when accompanied by a good understanding of the influence of environmental factors, knowledge of the genetic parameters, and the genetic relationships between the traits of interest. Thus, this study aimed to evaluate the influence of non-genetic factors on growth traits and Kleiber ratios and to estimate genetic parameters for early growth traits in Dorper x indigenous sheep. The effects of fixed factors were analyzed by the general linear model procedure of SAS and the genetic parameters were estimated by AI-REML algorithm using a WOMBAT computer program fitted animal model. The log-likelihood ratio test was used for selecting the best-fitted model from four models. The overall least-squares means for birth weight (BW), weaning weight (3MW), six-months (6MW), nine-month (9MW), and yearling (12WT) were 3.03 ± 0.02, 14.5 ± 0.18, 20.4 ± 0.26, 24.8 ± 0.31, and 28.3 ± 0.40 kg, respectively. The overall least-square means for Kleiber ratio from birth to weaning (KR1), weaning to six-month (KR2), six to nine-month (KR3) and nine-month to yearling age (KR4) were 16.8 ± 0.10, 6.41 ± 0.17, 4.55 ± 0.21 and 3.38 ± 0.20 g/kg of metabolic weight, respectively. The inclusion of maternal genetic effect exerted a significant influence on BW and it explains 20% of the phenotypic variation. The total heritability (h2t) estimates for BW, 3MW, ADG1 and KR1 were 0.10, 0.14, 0.16 and 0.12, respectively. The phenotypic correlation varied from − 0.11 to 0.98 whereas the direct genetic correlation ranged from − 0.32 to 0.98. The mean inbreeding coefficient was 0.105% with annual rate of 0.02%. The heritability estimates for growth traits and Kleiber ratio suggests that slow genetic progress would be expected from the selection. However it is, integration of selection with crossbreeding program with this level of variation would enhance the genetic gain. Therefore, selection should be conducted based on breeding values estimated from multiple information sources to increases the selection response.

Effectiveness of Genetic Parameter Estimation in a Small Flock of Merino Sheep with Shallow Pedigree

In this study, the genetic and non-genetic parameters were estimated for growth traits of Karacabey merino sheep. Growth performance data refer to 1863 lambs born between 2016 and 2018. Analyses were carried out by restricted maximum likelihood fitting animal models and disregarding or including maternal genetic or maternal permanent environmental effect. Six different animal model were fitted for all traits, and the most suitable model for each trait was chosen after Akaike information criterion test (AIC). Year of birth, age of dam, type of birth and lamb sex were significant sources of variation on birth weight (BW), average daily gain (ADG), Kleiber ratio (KR), weaning weight (WW) and six month weight (6MW). Direct heritability (h^2) for BW, ADG and 6MW were 0.12, 0.02 and 0.04, respectively, however, for KR and WW were 0.00 model 6 (which the best). The estimates of maternal heritability (m^2) for ADG, KR and WW were 0.12, 0.04 and 0.04, respectively in model 5, also maternal heritability were low for BW and 6MW. Maternal permanent environmental effects (c^2) have high contribution to the explanation growth traits and were estimated between 0.19 and 0.75 for these traits. These results showed that selecting for improved maternal and/or direct effects for Karacabey merino in the herd would generate very slow genetic improvement in growth traits.