The goat (Capra hircus) mammary gland secretory tissue proteome as influenced by weight loss: A study using label free proteomics.

Unlabelled: Seasonal weight loss (SWL) is a significant limitation to animal production. Breeds that have evolved in harsh climates have acquired tolerance to SWL through selection. Herein, label free proteomics was used to characterize the effects of SWL in two goat breeds with different levels of adaptation to nutritional stress: Majorera (tolerant) and Palmera (susceptible). Nine Majorera and 10 Palmera dairy goats were used, divided in 4 sets, 2 for each breed: underfed and a control group: Majorera Control (MC), Palmera Control (PC), Majorera Restricted (ME) and Palmera Restricted (PE). At day 22, mammary gland biopsy samples were obtained. Label free proteomic analysis enabled the identification of over 1000 proteins, of which 96 showed differential expression between two of the groups within studied comparisons. Majorera breed showed higher expression of immune system related proteins. In contrast, Palmera breed showed higher expression of proteins related to apoptosis. Results indicate that the two goat breeds have a distinct metabolism reaction to SWL, and that proteins related to the immune system and apoptosis such as cadherin-13, collagen alpha-1, nidogen-2, clusterin and protein s100-A8 could be considered putative candidates as markers of tolerance to SWL.

Biological Significance: Seasonal weight loss (SWL) is one of the major constraints to animal production in the tropics. We compared the proteomics profiles of two dairy goat breeds with different levels of tolerance to SWL under control and feed restriction conditions using label free proteomics. We have identified over 1000 proteins in the goat mammary gland, of which 96 showed differential expression. Despite the fact that both breeds showed a decrease in the number of proteins related to protein, carbohydrates and fat biosynthesis, the tolerant breed showed higher expression of immune system related proteins compared to the susceptible breed. On the contrary, the susceptible breed had higher expression of apoptosis related proteins indicating that both breeds reacted differently to weight loss and that proteins related to the immune system and apoptosis such as cadherin-13, collagen alpha 1, nidogen-2 or clusterin may be suggested as markers of tolerance to SWL.