Mammary immune allocation strategies under low-input systems: Density preservation versus volume-driven immune output...

Little is known about the allocation of immune resources by dairy breeds under low-input systems, especially when the immune density and functional secretion are measured concomitantly. This experiment examined physiological trade-offs among milk production, immune protein level, functional immune response, milk composition, and electrical conductivity (EC) in native Syrian Golani cows and Golani crossbreds with Friesians. Using a longitudinal repeated-measures design across colostrum and established lactation, we evaluated immunoglobulins (IgG, IgA, IgM), lactoferrin, immune density (g/L), functional immune secretion (g/day), milk composition, and EC. The effect of lactation stage (colostrum vs. milk) on all immune markers was highly significant which confirms the pronounced physiological change between early and established lactation. Effects of breed were selective. Golani cows were found to have greater immune concentrations of the selected markers, and crossbred cows were found to have greater functional immune secretion which was mainly due to increased milk yield. Notably, there were important Breed x Lactation stage interactions on IgM and lactoferrin, which showed breed-specific differences in the extent of the transition between colostrum and milk. Conversely, IgG did not indicate any significant interaction implying a more conserved pattern of stage-related decline among breeds. The relationship between immune concentration and milk yield was found to be negative, which is in line with the dynamics of dilution through secretion. Crossbred cows optimized the overall daily immune production, and Golani cows retained greater immune density per unit of milk and lower EC values, which suggest improved mammary ionic stability. The results show that the immune-production associations can be more effectively viewed in terms of integrative longitudinal models, which present a biologically sound method of assessing adaptive efficiency in successful dairy systems.