Yazar "Mendes Malhado, Carlos Henrique" seçeneğine göre listele

Listeleniyor 1 - 5 / 5
  • [ X ]
    Öğe
    Age at first calving of Nellore cattle in the semi-arid region of northeastern Brazil using linear, threshold, censored and penalty models
    (Elsevier, 2013) Mendes Malhado, Carlos Henrique; Mendes Malhado, Ana Claudia; Martins Filho, Raimundo; Souza Carneiro, Paulo Luiz; Pala, Akin; Carrillo, Jose Adrian
    Data are typically discarded when there are inconsistencies in a database, or when information is discrepant or out of range for the biological characteristics of the species being analyzed. However, such loss of information could have considerable implications for genetic evaluation of cattle. Here, we use different models to estimate genetic parameters for age at first calving in order to prevent data elimination. We used five approaches based on trait distribution to define the limits of censure/disposal: linear model, censorship, penalty and missing methods, and threshold model (binary and polychotomous). Data splitting and Pearson correlation were used to evaluate fitting and comparison of models. The lowest heritabilities were estimated for the missing method and the binary model. Exclusion of outliers from the data considerably affects the estimation of genetic parameters and the ranking of sires. Moreover, models that suffered from data elimination generated the worst classifications in terms of the comparison of models. Researchers should be extremely careful when deciding to discard data. For example, an age at first calving up to 72 months could be considered an outlier for other countries or even other areas in Brazil. Although this value is very high, it could be realistic under arid or semi-arid conditions. In these situations, the penalty or censure models are the most appropriate methods of analyses. (C) 2013 Elsevier B.V. All rights reserved.
  • [ X ]
    Öğe
    Genetic parameters by Bayesian inference for dual purpose Jaffarabadi buffaloes
    (Archiv Fur Tierzucht, 2012) Mendes Malhado, Carlos Henrique; Mendes Malhado, Ana Claudia; Ramos, Alcides Amorim; Souza Carneiro, Paulo Luiz; Siewerdt, Frank; Pala, Akin
    Knowledge of genetic parameters is essential for improved reproductive management and increased yield. Quantitative analysis of genetic parameters is lacking for many breeds of buffaloes. This article provides the first estimate of genetic parameters for dual purpose (meat and milk) Brazilian Jaffarabadi buffaloes, using Bayesian inference. Data on milk yield (MY), lactation length (LL), weight at 205 days (W205) and 365 (W365) days of age, and average daily gain (ADG) from 205 to 365 days of age were collected in two herds. Bivariate analyses (using the program MTGSAM) were performed with the Gibbs sampler to obtain estimates of variance and covariance. Average lactation milk yield and lactation length were 1 620.2 +/- 450.9 kg and 257.6 +/- 46.8 days, respectively, and the mean values for weight traits (kg) were 181.6 +/- 63.3 (W205), 298.04 +/- 116.1 (W365), and 0.73 +/- 0.35 (ADG). Heritability estimates (modes) were 0.16 for MY, 0.10 for LL, 0.43 for W205, 0.48 for W365 and 0.32 for ADG. There was a high genetic correlation (0.96) between milk yield and lactation length and very high genetic correlations (0.99) between the three growth traits. Our data suggest that both milk production and growth traits have clear potential for yield improvement through direct selection in this dual purpose breed. The selection for weight at an early age would be successful and selection for MY can be performed in the first lactation.
  • [ X ]
    Öğe
    Genetic parameters for milk yield, lactation length and calving intervals of Murrah buffaloes from Brazil
    (Revista Brasileira Zootecnia Brazilian Journal Animal Sci, 2013) Mendes Malhado, Carlos Henrique; Mendes Malhado, Ana Claudia; Ramos, Alcides de Amorim; Souza Carneiro, Paulo Luiz; de Souza, Julio Cesar; Pala, Akin
    The major objective of this study was to estimate heritability and genetic correlations between milk yield (MY) and calving interval (CI) and lactation length (LL) in Murrah buffaloes using Bayesian inference. The database used belongs to the genetic improvement program of four buffalo herds from Brazil. To obtain the estimates of variance and covariance, bivariate analyses were performed with the Gibbs sampler, using the program MTGSAM. The heritability coefficient estimates were 0.28, 0.03 and 0.15 for MY, CI and LL, respectively. The genetic correlations between MY and LL was moderate (0.48). However, the genetic correlation between MY and CI showed large HPD regions (highest posterior density interval). Milk yield was the only trait with clear potential for genetic improvement by direct mass selection. The genetic correlation between MY and LL indicates that indirect selection using milk yield is a potentially beneficial strategy. The interpretation of the estimated genetic correlation between MY and CI is difficult and could be spurious.
  • [ X ]
    Öğe
    Inbreeding depression on production and reproduction traits of buffaloes from Brazil
    (Wiley-Blackwell, 2013) Mendes Malhado, Carlos Henrique; Mendes Malhado, Ana Claudia; Souza Carneiro, Paulo Luiz; Ramos, Alcides Amorim; Carrillo, Jose Adrian; Pala, Akin
    The objective of this study was to evaluate the influence of inbreeding depression on traits of buffaloes from Brazil. Specifically, the traits studied were body weight at 205 and 365 days of age, average daily gain from birth to 205 days (ADG_205), average daily gain between 205 and 365 days (ADG205_365) in Mediterranean buffaloes, and milk yield, lactation length, age of first calving and calving intervals in Murrah buffaloes. Inbreeding effects on the traits were determined by fitting four regression models (linear, quadratic, exponential and Michaelis-Menten) about the errors generated by the animal model. The linear model was only significant (P<0.05) for growth traits (exception of ADG205_365). The exponential and Michaelis-Menten models were significant (P<0.01) for all the studied traits while the quadratic model was not significant (0.05) for any of the traits. Weight at 205 and 365 days of age decreased 0.25kg and 0.39kg per 1% of increase in inbreeding, respectively. The inbred animals (F=0.25) produced less milk than non-inbred individuals: 50.4kg of milk. Moreover, calving interval increased 0.164 days per 1% of increase in inbreeding. Interestingly, inbreeding had a positive effect on age at first calving and lactation length, decreasing age of first calving and increasing lactation length.
  • [ X ]
    Öğe
    Population structure and genetic variability in the Murrah dairy breed of water buffalo in Brazil accessed via pedigree analysis
    (Springer, 2012) Mendes Malhado, Carlos Henrique; Mendes Malhado, Ana Claudia; Souza Carneiro, Paulo Luiz; Ramos, Alcides Amorim; Ambrosini, Diego Pagung; Pala, Akin
    The objective of this study was to use pedigree analysis to evaluate the population structure and genetic variability in the Murrah dairy breed of water buffalo (Bubalus bubalis) in Brazil. Pedigree analysis was performed on 5,061 animals born between 1972 and 2002. The effective number of founders (fe) was 60, representing 6.32 % of the potential number of founders. The effective number of ancestors (fa) was 36 and the genetic contribution of the 17 most influent ancestors explained 50 % of the genetic variability in the population. The ratio fe/fa (effective number of founders/effective number of ancestors), which expresses the effect of population bottlenecks, was 1.66. Completeness level for the whole pedigree was 76.8, 49.2, 27.7, and 12.8 % for, respectively, the first, second, third, and fourth known parental generations. The average inbreeding values for the whole analyzed pedigree and for inbreed animals were, respectively, 1.28 and 7.64 %. The average relatedness coefficient between individuals of the population was estimated to be 2.05 %-the highest individual coefficient was 10.31 %. The actual inbreeding and average relatedness coefficient are probably higher than estimated due to low levels of pedigree completeness. Moreover, the inbreeding coefficient increased with the addition of each generation to the pedigree, indicating that incomplete pedigrees tend to underestimate the level of inbreeding. Introduction of new sires with the lowest possible average relatedness coefficient and the use of appropriate mating strategies are recommended to keep inbreeding at acceptable levels and increase the genetic variability in this economically important species, which has relatively low numbers compared to other commercial cattle breeds. The inclusion of additional parameters, such as effective number of founders, effective number of ancestors, and fe/fa ratio, provides better resolution as compared to the inclusion of inbreeding coefficient and may help breeders and farmers adopt better precautionary measures against inbreeding depression and other deleterious genetic effects.