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    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.
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    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.