PSXI-25 An evaluation of plasma folate and vitamin B12 concentrations of newly received feedlot heifers.

Abstract Newly received feedlot calves are at increased risk to bovine respiratory disease (BRD) due to multiple stressors including transportation and adaptation to novel environments and diet which can adversely influence metabolism and immunity. The objective was to evaluate plasma folate and vitamin B12 (B12) concentrations at feedlot arrival (d0) and 28 days later (d28) on 39 crossbred heifers (initial BW of 215 ± 30 kg) in relation to BRD morbidity. The DART (depression, appetite, respiration, and temperature) scoring system was daily assessed by three individuals to evaluate BRD morbidity status. A DART score ≥ 2 required antibiotic treatment. Throughout the 28-day period, the number of treatments was recorded and used to classify morbidity: 0 = no treatment (n=8); 1= one treatment (n=14); and 2 = two treatments or more (n=17). An indwelling temperature probe was vaginally inserted to measure vaginal temperature every 10 minutes for 28 days. Daily intake was measured by C-Lock SmartFeed system. Blood samples were collected by jugular venipuncture and BW recorded at d0 and d28. Plasma folate and B12 concentrations were analyzed by chemiluminescence. Proc MIXED of SAS with repeated measurements was used to analyze plasma folates at d0 and d28 with morbidity class and sampling time and its interaction as fixed effects. Proc CORR was used to evaluate the relationship with plasma folates and variables. Several samples were below the B12 detection limit of 150 pg/mL, therefore, proportion of samples below the detection limit was analyzed using Proc GLIMMIX with morbidity class as fixed effect, separately for d0 and d28. The interaction morbidity class x time tended to be significant for plasma folates (P=0.07). Plasma folates averaged 9.52 [standard error (SE): 1.13] ng/mL at d0 (P=0.73). At d28, it averaged 8.50, 6.41, and 5.43 (SE: 0.62) ng/mL for morbidity class 0, 1, and 2, respectively (P=0.001). Plasma folates tended to be higher for morbidity class 0 than 1 (P=0.10) and was higher for morbidity class 0 than 2 (P=0.003); with no difference between morbidity class 1 and 2 (P=0.63). Plasma folates at d28 were positively associated with average daily gain and DM intake (P=0.002). At d0, there was no difference in the proportion of samples below the detection limit for B12 between morbidity classes (P=0.70). At d28, heifers classified as morbidity class 2 had a lower proportion of samples below the detection limit for B12 [41 (SE: 12)%] than heifers in morbidity class 0 [88 (SE: 12)%] and 1 [86 (SE: 9)%, P=0.03]. It suggests that plasma B12 was higher for animals in morbidity class 2, which is in opposition with plasma folates. Additional research is required to confirm these results and evaluate potential implications on health and productivity.