Methane emission, metabolism, and performance of Holstein dairy cows with low, medium, and high lymphocyte proliferation during transition

摘要

This study aimed to identify interactions betweenstate of lactation (dry or early lactating) and immuneresponder group (low, medium, or high) for energy metabolismtraits as well as metabolic and immunologicaltraits in dairy cows. In early lactation, when the energypriority of cows shifts toward the mammary gland, theenergy available to be partitioned toward the immunesystem may differ among individuals. The equilibriumbetween energy supply from feed, digestion, and bodyreserve mobilization and energy expenditure with milk,immune system, methane, and heat production isdelicate in this stage. Seventeen Holstein cows enteringtheir second to fifth lactation were kept under comparablefeeding, housing, and management conditionsand were studied from 14 ± 6 d before calving to 11 ±3 d after calving. Feed intake, milk yield, body condition,blood metabolites, and cortisol as well as gaseousexchange in respiration chambers were measured. Thelatter was used to quantify methane emission and tocalculate resting metabolic rate and heat production.Subsets of blood leukocytes and peripheral bloodmononuclear cells (PBMC) were monitored. Activationand proliferation of the PBMC in response to the mitogenphytohemagglutinin ante- and postpartum wereassessed using the oxygen consumption rate (24-h cellculture assay) and the 3-(4,5-dimethylthiazol-2-yl)-2,5diphenyl tetrazolium bromide (MTT) assay (72-h cellculture assay). Cows were classified based on the invitro proliferative response of the PBMC measuredpostpartum in low (n = 6), medium (n = 5), and high(n = 6) responders. We found no interaction of stateof lactation with responder group for feed intake, milkyield, efficiency, metabolic traits, and immune cell activationante- and postpartum. However, after calving,low-responder cows produced less methane per unitof body weight and per unit of energy-corrected milkcompared with the other cows. This might be indicativeof a low rumen fermentation intensity. Low respondersmight therefore suffer from a lower availability ofdigestible energy in early lactation and not be able tosustain the shift from immune cell activation to proliferation.If so, the selection of environmentally friendlylow-methane emitters could promote phenotypes witha compromised immune response in the critical earlylactation.