Características comportamentais e morfológicas das vacas que influenciam a sobrevivência e o desempenho de seus bezerros do nascimento a desmama
Data
2021-11-29
Autores
Menezes, João Vitor de Toledo
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
O objetivo deste estudo foi avaliar características comportamentais e morfológicas de vacas da raça Nelore que podem influenciar a sobrevivência e o desempenho dos bezerros do nascimento à desmama. O estudo foi realizado durante os meses de julho e agosto de 2019 na Fazenda São Marcelo®, localizada no município de Juruena, estado de Mato Grosso, Brasil. Os comportamentos das vacas foram registrados utilizando observação direta e amostragem focal. A coleta de dados de cada animal teve início quando o vaqueiro (a pé) caminhava pela remanga, em direção ao bezerro e a vaca e era finalizada quando ele colocava o bezerro dentro de uma área protegida. Nesse momento um dos vaqueiros, avaliava o comportamento de proteção materna (CPMat) e a condição corporal de cada vaca (ECC), enquanto os pesquisadores atribuíram escores visuais para a avaliação dos chifres, as condições de úbere (EUb) e dos tetos (ET) e o vigor do bezerro. Foram registrados também o sexo, o peso ao nascer, o mês e o retiro de nascimento dos bezerros. A idade das vacas foi obtida no banco de dados da fazenda. Foram obtidos registros de 975 díades vacas-bezerros. as variáveis com distribuição contínua foram avaliadas quando a normalidade utilizando o teste Shapiro-Wilk e as variáveis categóricas foram avaliadas utilizando o procedimento FREQ do SAS (SAS Inst. Inc., Cary, NC). As análises estatísticas foram realizadas considerando dois conjuntos de dados, o primeiro contendo informação de 975 partos, foi utilizado para verificar as diferenças observadas entre bezerros que sobreviveram e os que morreram do nascimento até a desmama. O segundo banco de dados contendo informação de todos os bezerros desmamados (n=936) foi utilizado para identificar características medidas diretamente nos bezerros e nas vacas que podem estar associadas ao desempenho pré-desmama. Para analisar o efeito da idade da vaca no desempenho do bezerro foram criadas 12 classes levando em consideração a idade das vacas ao parto e o retiro que estas se encontravam. Para avaliar o efeito das variáveis medidas nos bezerros e nas vacas sobre o peso corporal dos bezerros ao desmame (ajustados para 210 dias de idade) e no ganho média diário de peso pré-desmama utilizou-se modelos lineares generalizados (PROC GLM) do SAS. As médias ajustadas para peso e ganho de peso foram comparadas utilizando o teste de Tukey considerando p ≤ 0.05 como efeito significativo e 0.05 < P 0.10 como tendência. Foram estimadas as correlações de Pearson entre peso ao nascer, peso ao desmame e o ganho de peso médio diário (PROC CORR do SAS). A categoria de idade das vacas, o escore de úbere e a simetria dos tetos afetaram significativamente o desempenho do bezerro (P< 0,01). Vacas mais velhas desmamaram bezerros mais pesados quando comparadas as vacas mais jovens. Vacas com úberes intermediários produziram bezerros mais pesados que as vacas com úberes pequenos (não foi registrada nenhuma vaca com úbere muito grande). Vacas com todos os tetos simétricos também produziram bezerros mais pesados na desmama.
The aim of this study was to assess the behavioral and morphological traits of Nellore cows that can influence the survival and performance of their calves from birth to weaning. The study was carried out from July to August 2019 at Fazenda São Marcelo®, located in the municipality of Juruena, state of Mato Grosso, Brazil. Cows' behavior were recorded by using direct observation and focal sampling. Data collection for each animal began when a cowboy (on foot) walked through the handling area, towards the calf and the cow, and was completed when he placed the calf inside a protected area. At that time, other cowboys assessed the maternal protective behavior (CPMat) and the body condition of each cow (ECC), while one of the researchers assigned the visual scores for horns, udder conditions (EUb) and teats (ET) and calf vigor. Sex, birth weight and date and place of calves' birth were also recorded. The age of the cows at parturition was obtained from the farm's database. Records from 975 cow-calf dyads were obtained. Variables with continuous distribution were assessed for normality using the Shapiro-Wilk test and categorical variables were assessed using the SAS FREQ procedure (SAS Inst. Inc., Cary, NC). Statistical analyzes were performed considering two sets of data, the first, containing information on 975 births, was used to verify the differences observed between calves that survived and those that died from birth to weaning. The second database containing only information of weaned calves (n=936) was used to identify calves' and cows' traits that would be associated with pre-weaning performance. To analyze the effect of cow age on calf performance, 12 classes were created, taking into account the age of the cows and calving site. To assess the effect of calves' and cows' traits on the body weight of calves at weaning (adjusted for 210 days of age) and on the pre-weaning average daily weight gain, generalized linear models (PROC GLM) of the SAS were used. Adjusted means for weaning weight and weight gain were compared using the Tukey test considering p ≤ 0.05 as a significant effect and 0.05 < P 0.10 as a trend. Pearson correlations between birth weight, weaning weight and average daily weight gain were estimated (PROC CORR from SAS). The classes of cows' age, the udder score and the teat symmetry affected significantly the calf performance (P<0.01). Older cows weaned heavier calves when compared to younger ones. Cows with intermediate udders produced heavier calves than cows with small udders (no cows with a very large udder were recorded). Cows with all symmetrical teats also produced heavier calves at weaning.
The aim of this study was to assess the behavioral and morphological traits of Nellore cows that can influence the survival and performance of their calves from birth to weaning. The study was carried out from July to August 2019 at Fazenda São Marcelo®, located in the municipality of Juruena, state of Mato Grosso, Brazil. Cows' behavior were recorded by using direct observation and focal sampling. Data collection for each animal began when a cowboy (on foot) walked through the handling area, towards the calf and the cow, and was completed when he placed the calf inside a protected area. At that time, other cowboys assessed the maternal protective behavior (CPMat) and the body condition of each cow (ECC), while one of the researchers assigned the visual scores for horns, udder conditions (EUb) and teats (ET) and calf vigor. Sex, birth weight and date and place of calves' birth were also recorded. The age of the cows at parturition was obtained from the farm's database. Records from 975 cow-calf dyads were obtained. Variables with continuous distribution were assessed for normality using the Shapiro-Wilk test and categorical variables were assessed using the SAS FREQ procedure (SAS Inst. Inc., Cary, NC). Statistical analyzes were performed considering two sets of data, the first, containing information on 975 births, was used to verify the differences observed between calves that survived and those that died from birth to weaning. The second database containing only information of weaned calves (n=936) was used to identify calves' and cows' traits that would be associated with pre-weaning performance. To analyze the effect of cow age on calf performance, 12 classes were created, taking into account the age of the cows and calving site. To assess the effect of calves' and cows' traits on the body weight of calves at weaning (adjusted for 210 days of age) and on the pre-weaning average daily weight gain, generalized linear models (PROC GLM) of the SAS were used. Adjusted means for weaning weight and weight gain were compared using the Tukey test considering p ≤ 0.05 as a significant effect and 0.05 < P 0.10 as a trend. Pearson correlations between birth weight, weaning weight and average daily weight gain were estimated (PROC CORR from SAS). The classes of cows' age, the udder score and the teat symmetry affected significantly the calf performance (P<0.01). Older cows weaned heavier calves when compared to younger ones. Cows with intermediate udders produced heavier calves than cows with small udders (no cows with a very large udder were recorded). Cows with all symmetrical teats also produced heavier calves at weaning.
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Palavras-chave
Desempenho, Bem estar, Comportamento