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A atuação do médico veterinário na maximização reprodutiva de uma vacada de carne intervalo entre partos da raça Mertolenga como caso de estudo
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Este estudo teve como objetivos analisar a distribuição de partos na raça Mertolenga e a influência dos principais efeitos ambientais no intervalo entre partos (IEP) em bovinos da mesma raça. Foram utilizados os registos de 8 explorações de criadores, inscritas no livro genealógico da Associação de Criadores de Bovinos Mertolengos (ACBM), correspondendo a 17 090 partos e 13 510 IEP de 2 655 fêmeas, ocorridos entre 1990 e 2019. Os registos foram submetidos a várias análises preliminares com o programa SAS®, utilizando-se o PROC UNIVARIATE, o PROC MEANS e o PROC FREQ. Com um modelo misto, através do PROC MIXED do mesmo programa, analisou-se o IEP com um modelo que incluiu os efeitos fixos da exploração, ano e mês de parto, sexo e raça do vitelo e como covariável o efeito linear e quadrático da idade ao parto; a fêmea (vaca) foi considerada como efeito aleatório no modelo misto. A idade média ao primeiro parto (IPP) foi de 34,3 meses, a idade média de morte foi de 13,76 anos e o número médio de partos por vaca ao longo da vida foi de 5,3±3,4 partos/vaca. Neste estudo observou-se um IEP médio de 436,9 ±116,2 dias e as variáveis “exploração”, “mês do parto”, “ano do parto”, “raça do vitelo” e “idade da vaca ao parto” influenciaram significativamente o IEP (p<0,0001) enquanto que a variável “sexo do vitelo” não se revelou significativa (p=0,1127). Observou-se que a maior concentração de partos ocorre nos meses de verão, principalmente entre meados de julho e setembro e que existem grandes diferenças nos valores de IEP médios entre as distintas explorações e anos avaliados. Vacas paridas em abril tiveram o IEP médio mais curto (418,9±4,6 dias) e vacas paridas em janeiro e fevereiro apresentaram valores médios de IEP mais longos (451,9±3,5 dias versus 450,315±3,755 dias). Vacas que parem vitelos Mertolengos puros têm, em média, IEP inferiores (421,9) que vacas que parem vitelos cruzados (440,1). Apesar de não existirem diferenças significativas, observou-se que vacas que parem vitelas, em média, têm IEP cerca de 3 dias mais curtos que vacas que parem machos (432,5±1,9 dias versus 429,5±1,9 dias). Em relação à idade ao parto, verificou-se que se trata de uma variável com um efeito quadrático neste parâmetro reprodutivo, sendo que fêmeas mais novas apresentam IEP superiores e que este intervalo vai diminuindo com o avançar da idade das vacas até aos 9,3 anos (112 meses), idade em que se verificou o menor IEP médio (404 dias) e a partir da qual este valor volta a aumentar. Tendo em conta a influência significativa do maneio realizado na vacada no seu IEP médio, é fundamental a sensibilização dos produtores para o papel que o médico veterinário representa para a melhoria da eficiência reprodutiva dos seus efetivos.
ABSTRACT - The role of the veterinarian in the reproductive maximization in beef cattle: calving to calving interval of Mertolenga breed as a case study - This study aimed to analyse the distribution of Mertolenga calving and the influence of the main environmental effects on the calving-to-calving interval (CCI) in cattle of the same breed. The records of 8 farms of breeders, registered in the genealogical book of the Association of Mertolengo Bovine Breeders (ACBM) were used, corresponding to 17 090 births and 13 510 CCI of 2 655 females, which occurred between 1990 and 2019. The records were submitted to several preliminary analyses with the SAS® program, using PROC, PROC MEANS and PROC FREQ. With a mixed model, through the PROC MIXED of the same program, the CCI was analysed with a model that included the fixed effects of the herd, year and month of calving, sex and breed of the calf and as covariable the linear and quadratic effect of age to delivery; the female (cow) was considered as a random effect in the mixed model. The average age at first calving (AFC) observed was 34.3 months, the average age of death was 13.8 years and the average number of births per cow throughout life was 5.3 ± 3,9 calves per cow. In this study, an average IEP of 436.9 ± 116.2 days was observed and the variables “herd”, “month of calving”, “year of calving”, “calf breed” and “cow age at calving” influenced significantly the CCI (p <0.0001) while the variable “calf sex” was not significant (p = 0.1127). It was observed that the highest concentration of births occurs in the summer months, mainly between mid-July and September, and that there are large differences in the mean CCI values between the different farms and years evaluated. Cows calved in April had the shortest CCI average (418.9 ± 4.6 days), and cows calved in January and February had longer CCI values (451,9 ± 3,5 days / 450,3 ± 3,8 days). Cows that calve pure Mertolengos calves have, on average, lower CCI (421,9) that cows that calve crossed calves (440,1). Although there were no significant differences, it was observed that cows that calved female calves, on average, had CCI about 3 days shorter than cows that calved males (432.5 ± 1.9 days / 429.5 ± 1.9 days). Regarding the age at calving, it was found that this is a variable with a quadratic effect on this reproductive parameter and that younger females have higher CCI and that this interval decreases with the advancing age of the cows up to 9.3 years (112 months), age at which the lowest mean CCI (404 days) was observed and after which this value increases again. Bearing in mind the significant influence of the management carried out on the cow in its average CCI, it is essential to raise awareness among producers about the advantages that may arise from improving the reproductive efficiency of their herds and the role that the veterinarian plays to successfully achieve this goal.
ABSTRACT - The role of the veterinarian in the reproductive maximization in beef cattle: calving to calving interval of Mertolenga breed as a case study - This study aimed to analyse the distribution of Mertolenga calving and the influence of the main environmental effects on the calving-to-calving interval (CCI) in cattle of the same breed. The records of 8 farms of breeders, registered in the genealogical book of the Association of Mertolengo Bovine Breeders (ACBM) were used, corresponding to 17 090 births and 13 510 CCI of 2 655 females, which occurred between 1990 and 2019. The records were submitted to several preliminary analyses with the SAS® program, using PROC, PROC MEANS and PROC FREQ. With a mixed model, through the PROC MIXED of the same program, the CCI was analysed with a model that included the fixed effects of the herd, year and month of calving, sex and breed of the calf and as covariable the linear and quadratic effect of age to delivery; the female (cow) was considered as a random effect in the mixed model. The average age at first calving (AFC) observed was 34.3 months, the average age of death was 13.8 years and the average number of births per cow throughout life was 5.3 ± 3,9 calves per cow. In this study, an average IEP of 436.9 ± 116.2 days was observed and the variables “herd”, “month of calving”, “year of calving”, “calf breed” and “cow age at calving” influenced significantly the CCI (p <0.0001) while the variable “calf sex” was not significant (p = 0.1127). It was observed that the highest concentration of births occurs in the summer months, mainly between mid-July and September, and that there are large differences in the mean CCI values between the different farms and years evaluated. Cows calved in April had the shortest CCI average (418.9 ± 4.6 days), and cows calved in January and February had longer CCI values (451,9 ± 3,5 days / 450,3 ± 3,8 days). Cows that calve pure Mertolengos calves have, on average, lower CCI (421,9) that cows that calve crossed calves (440,1). Although there were no significant differences, it was observed that cows that calved female calves, on average, had CCI about 3 days shorter than cows that calved males (432.5 ± 1.9 days / 429.5 ± 1.9 days). Regarding the age at calving, it was found that this is a variable with a quadratic effect on this reproductive parameter and that younger females have higher CCI and that this interval decreases with the advancing age of the cows up to 9.3 years (112 months), age at which the lowest mean CCI (404 days) was observed and after which this value increases again. Bearing in mind the significant influence of the management carried out on the cow in its average CCI, it is essential to raise awareness among producers about the advantages that may arise from improving the reproductive efficiency of their herds and the role that the veterinarian plays to successfully achieve this goal.
Descrição
Dissertação de Mestrado Integrado em Medicina Veterinária
Palavras-chave
Eficiência reprodutiva Mertolenga intervalo entre partos carne bovinos Reproductive efficiency Mertolenga calving to calving interval beef cattle
Contexto Educativo
Citação
Bettencourt AHP 2021. A atuação do médico veterinário na maximização reprodutiva de uma vacada de carne intervalo entre partos da raça Mertolenga como caso de estudo [dissertação de mestrado]. Lisboa: FMV-Universidade de Lisboa.
Editora
Universidade de Lisboa, Faculdade de Medicina Veterinária