ABSTRACT
This study addresses the hypothesis that different acute stressors can cumulatively decrease milk yield. In fact, in a time of global warming, the impact of environmental stress and farm management practices on milk production remains unclear. In this context, our objective was to investigate the effect of acute and cumulative stress on gene expression in mammary tissue and their interactions with physiological responses and milk yield in Saanen goats. Thirty lactating goats were subjected to two treatments: (1) control (CT), in which goats were maintained following a habitual routine under comfort conditions; (2) stress (ST), in which the goats were subjected to different types of environmental stress: heat stress, adrenocorticotropic hormone administration, hoof care management, and exposure to rain. These stressors were performed sequentially, with one stress per day on four consecutive lactation days, to evaluate their effect on milk quality and milk yield. Our results showed that compared to CT goats, cumulative stress increased the gene expression of glucocorticoid receptor (GR), interferon-gamma (IFN-γ), superoxide dismutase (SOD), and catalase (CAT) in mammary tissue, which are indicators of cortisol action, inflammatory response, and antioxidant enzymes. Furthermore, the acute challenges imposed on ST goats changed their rectal temperature and respiratory frequency and increased cortisol, glucose, cholesterol, triglycerides, and high-density lipoprotein release in plasma when compared to CT goats. Although these physiological and metabolic responses restore homeostasis, ST goats showed lower milk yield and higher somatic cell count in milk than CT goats. In conclusion, the results confirmed our initial hypothesis that different acute stressors cumulatively decrease the milk yield in Saanen goats.
ABSTRACT
Estudou-se no estuário de Cananéia, litoral do estado de São Paulo, Brasil, a presença de Ascocotyle (Phagicola) longa Ransom, 1920 (Digenea: Heterophylidae), trematódeo, em tainha (Mugil platanus, Günther, 1880). Foram realizadas amostragens a fresco e cortes histológicos em tecidos provenientes de 61 exemplares. A presença de metacercárias foi comprovada em 100 por cento dos peixes examinados, com a seguinte distribuição: coração (21,6 por cento), fígado (19,7 por cento) e rins (58,6 por cento). As alterações histológicas no tecido cardíaco foram caracterizadas pela presença de um granuloma parasitário formado por uma cápsula de tecido conjuntivo ao redor do parasita, levando a um edema generalizado. Para determinar a infecção em alevinos de tainha da espécie M. platanus, foram capturados 100 exemplares nas entradas de córregos da região estuarino-lagunar. Esses peixes foram eviscerados para a pesquisa de metacercárias pelo exame a fresco, verificando-se que 100 por cento dos alevinos não estavam infectados.
The present research was carried out the coast of the state of São Paulo, Brazil, when it was studied the presence of Ascocotyle (Phagicola) longa Ransom, 1920 (Digenea: Heterophylidae), trematode, in mullet (Mugil platanus, Günther, 1880). Fresh samples and histological tissues sections from 61 animals were obtained. The results showed presence of metacercariae of A. (P.) longa in 100 percent of the fish examined, with the following distribution: heart (21.6 percent), liver (19.7 percent) and kidneys (58.6 percent). Histological alterations in cardiac tissues were characterized by the presence of a parasitic granuloma formed by a connective tissue capsule around the parasite, leading to generalized edema. To determine the infection in juvenile grey mullets of the M. platanus species, 100 of them were captured in the stream entrances of the estuary region, each fish was individually sacrificed and fresh mounts were prepared to determine the presence of metacercariae, demonstrating that 100 percent of the juveniles were not infected.
