O balanço energético negativo e a cetose em bovinos leiteiros: avaliação da glucose e do β-hidroxibutirato sanguíneos
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2010
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As vacas leiteiras sofrem grandes alterações metabólicas durante o período final da gestação e início da lactação. O motor fundamental das mudanças fisiológicas é o inicio da lactação após o parto a partir dos quais às necessidades energéticas extras da vaca deixam de ser para o aporte adequado de nutrientes para o feto e passam a ser para a produção de leite. Após o parto a ingestão de alimentos não é suficiente para fornecer energia suficiente para as necessidades extra da vaca, conduzindo a um balanço energético negativo (NEB) no início da lactação. A cetose ocorre por uma inadaptação das vacas leiteiras ao NEB. Esta doença caracteriza-se pela elevação anormal na concentração de corpos cetónicos: ácido acetoacético, acetona e β-hidroxibutirato (BHBA) nos fluído e tecidos corporais.
Neste estudo de campo foram avaliados os níveis de BHBA e glucose sanguínea de animais com suspeita de cetose clínica e subclínica, para posterior confirmação, bem como os dias postpartum, o número de partos do animal, a associação a outras doenças e o índice de condição corporal (BCS). Também foi avaliado o maneio do período de seca e a preparação da alimentação dos efectivos onde se encontravam os animais positivos à cetose.
Verificou-se que a cetose era mais comum em vacas nas primeiras duas semanas postpartum e com BCS elevado. Uma maior percentagem de casos positivos refere-se à cetose secundária a outras doenças e uma menor percentagem a casos de cetose primária. Os níveis sanguíneos de BHBA destas vacas estavam acima de 1400μmol / L o que confirmam esta doença. Em casos de cetose secundária não foi observada uma hipoglicemia, como é característico da cetose primária. Devido ao número de amostras ser baixo os dados relativos ao maneio dos efectivos foram inconclusivos para este estudo. Com este estudo conclui-se que a medição do BHBA e glucose sanguíneos são de extrema importância no diagnóstico e monitorização da cetose. Um diagnóstico de cetose secundária é muito importante para diminuir as perdas económicas numa exploração de bovinos leiteiros e aumentar a taxa de sucesso no tratamento da doença primária.
Dairy cows suffer major metabolic changes during late pregnancy and early lactation. The mainspring of the physiological changes is the beginning of lactation after calving, when the extra energy requirements of the cow changes from supplying nutrients for the fetus to the milk production. After calving, food intake is not sufficient to provide enough energy for the extra needs of the cow, leading to a negative energy balance (NEB) in early lactation. Ketosis is caused by an inadequate response of dairy cows to the NEB. This disease is characterized by abnormal elevation in the concentration of ketone bodies: acetoacetic acid, acetone and β-hydroxybutyrate (BHBA) in body tissues and fluids. In this field study the blood levels of glucose and BHBA of animals with suspected clinical and subclinical ketosis were evaluated, for further confirmation, as well as the postpartum days, the number of births of the animal, the association with other diseases and body condition score (BCS). We also evaluated the husbandry during the dry period and the preparation of feeding in herds where the animals were positive to ketosis. It was found that ketosis was more common in cows in the first two weeks postpartum and with height BCS. A higher percentage of positive cases refers to ketosis secondary to other diseases and a lower percentage of cases of primary ketosis. Blood levels of BHBA of these cows were above 1400μmol / L which confirmed this disease. In cases of secondary ketosis, hypoglycemia was not observed, as in primary ketosis. Due to the relative low number of samples, the data related with husbandry for this study were inconclusive. This study concluded that the measurement of blood glucose and BHBA are very important in diagnosing and monitoring ketosis. A diagnosis of secondary ketosis is very important to reduce economic losses on a farm for dairy cattle and increase the success rate in treating the primary disease.
Dairy cows suffer major metabolic changes during late pregnancy and early lactation. The mainspring of the physiological changes is the beginning of lactation after calving, when the extra energy requirements of the cow changes from supplying nutrients for the fetus to the milk production. After calving, food intake is not sufficient to provide enough energy for the extra needs of the cow, leading to a negative energy balance (NEB) in early lactation. Ketosis is caused by an inadequate response of dairy cows to the NEB. This disease is characterized by abnormal elevation in the concentration of ketone bodies: acetoacetic acid, acetone and β-hydroxybutyrate (BHBA) in body tissues and fluids. In this field study the blood levels of glucose and BHBA of animals with suspected clinical and subclinical ketosis were evaluated, for further confirmation, as well as the postpartum days, the number of births of the animal, the association with other diseases and body condition score (BCS). We also evaluated the husbandry during the dry period and the preparation of feeding in herds where the animals were positive to ketosis. It was found that ketosis was more common in cows in the first two weeks postpartum and with height BCS. A higher percentage of positive cases refers to ketosis secondary to other diseases and a lower percentage of cases of primary ketosis. Blood levels of BHBA of these cows were above 1400μmol / L which confirmed this disease. In cases of secondary ketosis, hypoglycemia was not observed, as in primary ketosis. Due to the relative low number of samples, the data related with husbandry for this study were inconclusive. This study concluded that the measurement of blood glucose and BHBA are very important in diagnosing and monitoring ketosis. A diagnosis of secondary ketosis is very important to reduce economic losses on a farm for dairy cattle and increase the success rate in treating the primary disease.
Descrição
Dissertação de Mestrado em Ciências Veterinárias
Palavras-chave
Cetose , Balanço energético negativo , β-hidroxibutirato , Glucose , Bovinos leiteiros