Effect of Acute and Cumulative Stress on Gene Expression in Mammary Tissue and Their Interactions with Physiological Responses and Milk Yield in Saanen Goats.

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.

Effect of experimental stress and cortisol release induced by ACTH administration on expression of key genes related to milk synthesis and apoptosis during mammary involution of Saanen goats.

This research paper addresses the hypothesis that stress, induced by ACTH administration and cortisol release increases somatic cell count (SCC) in mammary secretion, and improves the effectiveness of dry off in goats. We report indicators of milk synthesis and mammary gland involution during dry off. Thirty Saanen goats were subjected to abrupt dry off and treatments: (1) ACTH administration (ACTH) or (2) placebo (Control) on days 1, 3, 6, 9, 12, 15, 30, and 60 of dry off.

Acute and chronic effects of cortisol on milk yield, the expression of key receptors, and apoptosis of mammary epithelial cells in Saanen goats.

Cortisol (CORT) induces mammary development in late gestation and is fundamental to the differentiation of mammary epithelial cells and lactogenesis. The objective of this study was to investigate the relationship between CORT, insulin, prolactin, growth hormone, and insulin-like growth factor-1 in milk as well as the effect of CORT on the expression of receptors of insulin (INSR), prolactin (PRLR), growth hormone (GHR); we also studied the insulin-like growth factor-1 (IGF1R), glucocorticoid (NR3C1), mineralocorticoid (NR3C2), B-cell lymphoma 2 (BCL2), BCL-2-like protein X (BAX) genes, and the apoptosis rate of mammary epithelial cells of lactating Saanen goats in vivo and in vitro. The following experiments were conducted: (1) comparing hormone release in milk and blood after ACTH or a placebo administration; (2) evaluating the effect of acute CORT increases in mammary gland expression and milk yield in vivo; and (3) evaluating the effect of a chronic increase in CORT concentration in epithelial mammary cell apoptosis in vitro.

Long-term heat stress at final gestation: physiological and heat shock responses of Saanen goats.

The long exposure to heat negatively changes performance and productivity of animals, particularly when heat stress is associated with gestation. Indeed, little is known about the negative effects of long-term heat stress on the final gestation of dairy goats. In this context, the physiological and cellular responses of Saanen goats submitted to heat stress (37°C from 10:00 to 16:00 h) were investigated from day 60th pre-partum to day 60th post-partum.

Heat stress affects the expression of key genes in the placenta, placental characteristics, and efficiency of Saanen goats and the survival and growth of their kids.

Heat stress is detrimental during gestation; however, the effects of heat stress on goat placental characteristics and kid survival remain unclear. The objective of this study was to evaluate the effects of heat stress at final gestation on cortisol concentration, placenta characteristics, and the expression of genes related to placenta. Forty-six primiparous and multiparous Saanen goats were subjected to control (CT; under a thermoneutral environment: air temperature between 12°C and 25°C and the relative humidity from 45 to 73%, n = 23) or heat stress (HS; under a climatic chamber: air temperature at 37°C and the relative humidity at 60 to 70% from 0800 to 1600 h, n = 23) from the last 60 d of pregnancy until the first colostrum suckling.