PSII-2 - Longitudinal investigation of reducing growth during gilt development period and 25(OH)D₃ on gilt’s complete blood cell counts from 9 weeks of ages through 4 parity cycles.

Abstract: Complete blood cell count (CBC) provides a preliminary insight on immune cells and red blood cells (RBC) characteristics. To evaluate the effect of growth rate reduction and 25(OH)D₃ on subsequent CBC of gilts through four reproductive cycles, three groups of gilts (n = 60 in each group, PIC Camborough) were received at 9 weeks of age (average BW: 21.2±0.67 kg) and assigned to one of four dietary treatments. Treatments comprised two levels of dietary nutrients (Adeq: optimal growing diets that exceed NRC 2012 recommendations or Low: moderate slow growing diet that SID Lys and ME levels were gradually reduced by 0.03% and 0 kcal/kg, 0.15% and 146 kcal/kg, and 0.15% and 150 kcal/kg, respectively) and two sources of vitamin D [StD: 1653 IU cholecalciferol/kg or HyD: 500 IU cholecalciferol/kg + 50 mcg calcifediol (ROVIMIX HY-D® DSM Nutritional Products North America)] during development phase 1 (22 to 57 kg), 2 (57 to 91 kg), and 3 (91 until breeding). Dietary nutrient level treatment was withdrawn during gestation and lactation stages, while sows remained on their vitamin D treatments through three reproduction cycles. Blood was collected into K₂EDTA vacuum tube from one gilt per pen upon arrival (four/treatment), and phase 1 and 2 of gilt development. Once they were moved to stalls (MTS), blood samples were collected from each individual pig on d 110 of gestation and when they were bred or rebred for subsequent cycles. CBC was determined from a total of 1155 samples using automatic hematological analyzer within 6 hours of collection. Data were analyzed using a GLIMMIX procedure of SAS (Cary, NC). WBCs continued a downward trend after reaching a peak at breeding in the first reproductive cycle. Afterward, WBC level followed a descending triangle pattern repeatedly at rebreeding and 110 d of gestation. RBC, hemoglobin and hematocrit % increased in an upward trend until MTS. Unlike RBC which held relatively constant levels throughout the reproduction cycles, hemoglobin and hematocrit % exhibited a comparable pattern as WBCs. Gilts that survived more than three cycles had a higher percentage of eosinophil, RBC, hemoglobin, hematocrit % and RDW at the breeding of the first cycle. Slow growth during the development stage increased eosinophils and the percentage of eosinophils over WBC and lymphocytes. The inclusion of HyD as the source of vitamin D increased RBC and hematocrit %, MCV, and MCHC at the rebred after the first cycle . Collectively, results demonstrate that the stages of maturation and pregnancy exert a distinguishing impact on CBC populations. We identified biomarkers that can be used to predict the longevity of sows from blood samples obtained at the breeding of the first and second reproductive cycles, which could further refine optimum sow dietary treatments.