Efeitos de estressores ambientais sobre indicadores fisiológicos, produtivos, de bem-estar e saúde de glândula mamária em vacas leiteiras girolando
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Data
2023-04-27
Autores
Mendonça, Leticia Caldas
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Universidade Estadual Paulista (Unesp)
Resumo
O presente trabalho teve como objetivo compreender como o estresse por calor em vacas Girolando afeta indicadores fisiológicos, de bem-estar, produção de leite e a resposta celular frente ao desafio com lipopolissacarídeo (LPS) de Escherichia coli imposto à glândula mamária destes animais. A tese foi dividida em três capítulos, sendo o primeiro de revisão sobre o tema. O segundo capítulo trata do estudo que avaliou o efeito isolado do estresse por calor em vacas Girolando. Para tanto, doze vacas em lactação foram submetidas a estresse por calor (HS) por oito horas diárias em câmara climática regulada para manter índice de temperatura e umidade de 85, enquanto as outras doze vacas permaneceram em “free-stall” com sistema de resfriamento (CTR). O terceiro capítulo trata do estudo que avaliou a resposta da glândula mamária destas vacas sob estresse por calor quando desafiados ao LPS. Os mesmos 24 animais do primeiro estudo receberam, no dia 10 do experimento, uma dose única de 100 µg de LPS diluídos em 10 mL de solução fisiológica (0,9% NaCl) no quarto mamário posterior esquerdo e o quarto mamário posterior direito recebeu 10 mL de solução salina 0,9% de NaCl, sendo considerado o quarto mamário controle. A duração dos dois estudos, realizados em sequência, foi de 17 dias. Frequência respiratória (FR), temperatura vaginal (TVag), concentração plasmática de cortisol (CORT), tiroxina (T4), triiodotironina (T3), IGF-1 e insulina (INS), produção de leite, cultivo microbiológico do leite, composição do leite, contagem de células somáticas (CCS), contagem diferencial de células, número de passos e coices, frequência de micção, defecação, ruminação, consumo de matéria-seca e expressão gênica em células do leite foram avaliados. No primeiro estudo, a TVag das vacas HS foi significativamente maior do que as vacas CTR (p<0,05), entretanto, FR não se diferenciou. Dosagem de cortisol foi significativamente maior nos dias 5 e 7, outros hormônios não sofreram efeito entre grupos. Produção de leite foi significativamente menor no grupo HS, já componentes do leite, incluindo a CCS não foi diferente (p>0,05). As vacas HS ruminaram menos em sala de ordenha (p<0,05) e consumiram menor volume de matéria seca (p<0,05) ao longo dos dias do experimento. A expressão de genes ligados a proteínas de choque térmico, receptores de insulina, e prolactina e de glicocorticoides foram alteradas. No segundo estudo, a TVag dos animais HS foi superior (p<0,05) a das vacas CTR na média do período em que foram submetidas ao estresse por calor (39,12°C x 38,75ºC), e nas doze horas seguintes à administração de LPS (39,25ºC x 39,00ºC). FR não se diferenciou entre grupos (p>0,05). CORT, T4 INS foram significativamente maiores para o grupo HS nas horas 12, 24 e 12 e 24 pós-LPS, respectivamente. Produção de leite não se alterou entre os grupos HS e CTR mas apresentou interação com as horas pós LPS, sendo estatisticamente menor para os dois grupos na hora 24 pós-LPS. Já a CCS também não foi significativamente diferente entre os grupos, mas apresentou elevação significativa em seis horas após o LPS, mantendo-se elevada até 72 horas. A porcentagem de neutrófilos presentes no leite dos quartos mamários tratados com LPS foi significativamente maior do que nos quartos mamários controle nos tempos 6 e 24 horas pós-LPS. A expressão de genes ligados a proteínas de choque térmico, resposta imune e estresse oxidativo foram alteradas. A conclusão geral dos estudos é que as vacas Girolando experienciaram alterações fisiológicas, de comportamento e de produção compatíveis com estresse por calor. Entretanto, este estressor não foi iv capaz de afetar a imunidade da glândula mamária destes animais nem quando desafiados a um potente indutor de resposta inflamatória como o LPS.
The present study aims to understand how heat stress in Girolando cows affects physiological and welfare indicators, milk production, and cellular response before the challenges posed by Escherichia coli lipopolysaccharide (LPS) on the udder. The thesis is divided into three chapters, the first of which is a review of the subject. The second chapter focuses on the study that evaluated the isolated effect of heat stress in Girolando cows. For this purpose, twelve lactating cows were subjected to heat stress (HS) for eight hours a day in a regulated, climatic chamber to maintain a temperature and humidity index of 85, while the other twelve cows remained in a free stall with a cooling system (CTR). The third chapter focuses on the study that evaluated the udder response of these heat stressed animals after to a LPS challenge. On day 10 of the experiment, the same 24 animals from the first study received a single dose of 100 µg of LPS diluted in 10 mL of saline (0.9% NaCl) in the left mammary quarter, and 10 mL of 0.9% NaCl saline in the right mammary quarter, being the control quarter. The total duration of the two studies, performed in sequence, was 17 days. Respiratory rate (RR), vaginal temperature (TVag), cortisol plasma concentrations (CORT), thyroxine (T4), triiodothyronine (T3), IGF-1, and insulin (INS), milk production, microbiological milk culture, milk composition, somatic cell count (SCC), differential cell count, number of steps and kicks, frequencies of urination, defecation and rumination, dry matter intake, and gene expression in milk cells were evaluated. In the first study, TVag of HS cows was significantly higher than that of CT cows (p<0.05). However, FR did not differ. The cortisol dosage was significantly higher on days 5 and 7, and other hormones had no effect among groups. Milk production was significantly lower in the HS group; milk components including SCC did not differ (p>0.05). HS cows ruminated less in the parlor (p<0.05) and consumed less dry matter (p<0.05) over the days of the experiment. The expression of genes linked to heat shock proteins, insulin, prolactin, and glucocorticoid receptors were altered. In the second study, TVag of HS animals was higher (p<0.05) than that of CT cows in the average period when they were subjected to heat stress, and in the twelve hours following LPS administration. RR did not differ among groups (p>0.05). CORT, T4 INS were significantly higher for the HS group at hours 12, 24 and 12, and 24 post-LPS, respectively. Milk production did not change between HS and CTR groups but showed interaction with hours post-LPS, being statistically lower for both groups at hour 24 post-LPS. SCC was also not significantly different between groups but showed a significant elevation 6 hours postLPS, remaining elevated until 72 hours. The percentage of neutrophils present in the milk from the LPS-treated breast quarters was significantly higher than in the control breast quarters at 6 and 24 hours post-LPS. Expression of genes linked to heat shock, immune response and oxidative stress proteins were altered. The overall conclusion of the studies is that Girolando cows experienced physiological, behavioral, and production changes consistent with heat stress. However, this stressor was not able to affect the udder immunity of these animals even with the challenges posed by a potent inducer of inflammatory response such as LPS.
The present study aims to understand how heat stress in Girolando cows affects physiological and welfare indicators, milk production, and cellular response before the challenges posed by Escherichia coli lipopolysaccharide (LPS) on the udder. The thesis is divided into three chapters, the first of which is a review of the subject. The second chapter focuses on the study that evaluated the isolated effect of heat stress in Girolando cows. For this purpose, twelve lactating cows were subjected to heat stress (HS) for eight hours a day in a regulated, climatic chamber to maintain a temperature and humidity index of 85, while the other twelve cows remained in a free stall with a cooling system (CTR). The third chapter focuses on the study that evaluated the udder response of these heat stressed animals after to a LPS challenge. On day 10 of the experiment, the same 24 animals from the first study received a single dose of 100 µg of LPS diluted in 10 mL of saline (0.9% NaCl) in the left mammary quarter, and 10 mL of 0.9% NaCl saline in the right mammary quarter, being the control quarter. The total duration of the two studies, performed in sequence, was 17 days. Respiratory rate (RR), vaginal temperature (TVag), cortisol plasma concentrations (CORT), thyroxine (T4), triiodothyronine (T3), IGF-1, and insulin (INS), milk production, microbiological milk culture, milk composition, somatic cell count (SCC), differential cell count, number of steps and kicks, frequencies of urination, defecation and rumination, dry matter intake, and gene expression in milk cells were evaluated. In the first study, TVag of HS cows was significantly higher than that of CT cows (p<0.05). However, FR did not differ. The cortisol dosage was significantly higher on days 5 and 7, and other hormones had no effect among groups. Milk production was significantly lower in the HS group; milk components including SCC did not differ (p>0.05). HS cows ruminated less in the parlor (p<0.05) and consumed less dry matter (p<0.05) over the days of the experiment. The expression of genes linked to heat shock proteins, insulin, prolactin, and glucocorticoid receptors were altered. In the second study, TVag of HS animals was higher (p<0.05) than that of CT cows in the average period when they were subjected to heat stress, and in the twelve hours following LPS administration. RR did not differ among groups (p>0.05). CORT, T4 INS were significantly higher for the HS group at hours 12, 24 and 12, and 24 post-LPS, respectively. Milk production did not change between HS and CTR groups but showed interaction with hours post-LPS, being statistically lower for both groups at hour 24 post-LPS. SCC was also not significantly different between groups but showed a significant elevation 6 hours postLPS, remaining elevated until 72 hours. The percentage of neutrophils present in the milk from the LPS-treated breast quarters was significantly higher than in the control breast quarters at 6 and 24 hours post-LPS. Expression of genes linked to heat shock, immune response and oxidative stress proteins were altered. The overall conclusion of the studies is that Girolando cows experienced physiological, behavioral, and production changes consistent with heat stress. However, this stressor was not able to affect the udder immunity of these animals even with the challenges posed by a potent inducer of inflammatory response such as LPS.
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Palavras-chave
Estresse termico, Mastite bovina, Lipopolissacarideos, Producao de leite, Resposta imune