The effects of diet supplementation with yeast on the expression of selected immune system genes in the milk somatic cells of dairy goats.

The aim of the study was to evaluate the impact of diet supplementation with active yeast culture (Saccharomyces cerevisiae) on the expression of selected immune system genes in goat milk somatic cells (MSC) and on milk production traits. Eighteen dairy goats were divided by breed and parity into two groups: control (n = 9) and supplemented (n = 9). Each group consisted of 5 Polish White Improved (PWI) and 4 Polish Fawn Improved (PFI) goats. Four goats (2 PWI and 2 PFI) were in their second lactation and five (3 WPI and 2 PFI) in more than second lactation. Beginning from a week before expected kidding, supplemented does were fed 10g yeast/day/goat until 100 day post-partum, after which the dose was increased to 20g/day/goat. On day 7, 30, 80, 120 and 240 of lactation milk samples were collected and used to SC isolation, microbiological analysis and to determine the physico-chemical composition of milk. Total RNA was isolated from SC and expressions of beta 1-defensin, beta 2-defensin, bactenecin 7.5, bactenecin 5, hepcidin and lyzozyme genes were measured with qRT-PCR using cyclophilin A (PPM) as a reference gene. Supplementation with yeast did not affect milk yield and composition (P>0.05). Genes encoding beta 2-defensin, bactenecin 7.5 and hepcidin were influenced by yeast diet supplementation resulting in their increased expression in MSC (P <= 0.05) regardless of the amount of supplement. The environmental bacteria did not affect the level of gene transcripts. However, the presence of beta 2-defensin, bactenecin 5 and 7.5, hepcidin and lysozyme transcripts in milk cells derived from pathogen-free udders proved their constitutive expression. The expression of beta 1-defensin gene was not found indicating that it is not constitutively expressed in milk cells and does not participate in the defense of the udder against environmental bacteria. These findings support that beta 2-defensin, bactenecin 5, bactenecin 7.5 and hepcidin may play a role in maintaining the health of the goat mammary gland.