Hematology parameters as potential indicators of feed efficiency in pigs.

The identification of an inexpensive, indirect measure of feed efficiency in swine could be a useful tool to help identify animals with improved phenotypes to supplement expensive phenotypes including individual feed intakes. The purpose of this study was to determine whether hematology parameters in pigs at the beginning and end of a feed efficiency study, or changes in those values over the study, were associated with average daily gain (ADG), average daily feed intake (ADFI), or gain-to-feed (G:F). Whole blood samples were taken at days 0 and 42 from pigs ( n = 178) that were monitored for individual feed intakes and body weight gain during a 6-week study. Blood samples were analyzed for blood cell parameters including white blood cell (WBC), neutrophil, lymphocyte, monocyte, eosinophil and basophil counts, red blood cell (RBC) counts, hemoglobin, hematocrit, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC), platelet count, and mean platelet volume (MPV). Feed efficiency parameters were predicted using an ANOVA model including fixed effects of farrowing group and pen (sex constant) and individual hematology parameters at day 0, day 42 or their change as covariates. At day 0, platelet count was positively associated with ADFI ( P < 0.05) and negatively associated with G:F ( P < 0.1), and lymphocyte count was positively associated with ADFI ( P < 0.05). At day 42, neutrophil, RBC counts, hemoglobin and hematocrit were associated with ADFI ( P < 10 -3 ). Over the course of the study, changes in RBC measurements including RBC, hemoglobin, MCV, MCH, and MCHC ( P < 10 -4 ) which may improve oxygen carrying capacity, were associated with ADG and ADFI. The change in hematocrit over the course of the study was the only parameter that was associated with all three measures of feed efficiency ( P < 0.05). Changes in RBC parameters, especially hematocrit, may be useful measurements to supplement feed efficiency phenotypes in swine.