Repeatability of metabolic responses to a nutrient deficiency in early and mid lactation and implications for robustness of dairy cows

Nutrient partitioning toward the mammary gland during insufficient energy and nutrient supply is a strategy to ensure survival of the offspring in mammalian species. This homeorhetic priority of the mammary gland is also present in the modern dairy cow, in particular in early lactation. However, despite similar metabolic loads, the adaptive response to a given metabolic load varies considerably among animals. The aim of this study was to investigate if individual cows respond in a consistent manner to a negative energy balance (NEB) in early and mid lactation. Twenty-five dairy cows experienced the usual NEB after parturition and were subjected to a second 3-wk NEB induced by feed restriction in mid lactation. Animals were retrospectively ranked according to their highest plasma nonesterified fatty acid (NEFA) concentration in wk 1 to 4 postpartum. The animals with the 33% highest and 33% lowest values were selected and classified either as the high response (HR) or low response (LR) group. Before parturition, no differences in the studied parameters, dry matter intake, energy balance, concentrations of glucose, NEFA, β-hydroxybutyrate, cholesterol, triglycerides, growth hormone, and insulin-like growth factor-1, were detected between LR and HR. After parturition, milk yield and energy-corrected milk yield was higher for HR compared with LR in wk 2 to 14 and wk 1 to 6, respectively. During feed restriction in wk 15 to 17 postpartum, no differences in energy-corrected milk between LR and HR were found. Energy balance was more negative in HR during the NEB in early lactation, but not different from LR during feed restriction in mid lactation. Although plasma concentrations of glucose, growth hormone, triglycerides, and cholesterol showed group differences in early lactation, but not during feed restriction, the plasma concentrations of NEFA, β-hydroxybutyrate, and insulin-like growth factor-1 in HR changed repeatedly to a greater extent during the NEB at the 2 stages of lactation compared with LR despite the similar extent of the NEB itself in both groups. The repeatedly greater amplitude of adaptive responses in HR compared with LR at different time points might partly indicate an underlying genetic background to enable a sufficient and rapid supply of mobilization-derived nutrients. The individual characteristics of adaptation to an energy and nutrient shortage might be beneficial when implemented in breeding programs.