Abstract
Transportation can compromise health and production performance in young calves. Although widely accepted that the younger calves are, the greater the probability of negative outcomes, there still is a lack of evidence-based recommendations on the minimum age at transportation. Our objective was to evaluate the impact of transport age on growth performance, incidence of scours, and plasma metabolites over the first 28 d post-transport in Charolais × Holstein crossbred calves. Calves (n = 36) ages 2, 4, 8 and 14-d old were transported in summer from a commercial farm to an on-campus calf rearing facility (410 miles). Calf body weight (BW) was recorded before departure, on arrival and d 28 post-transport. Dry matter intake (DMI) and fecal scores were recorded daily. Blood samples collected prior to transportation, on arrival, and d 7 and 28 post-transport were used for targeted metabolomics analysis (Biocrates MxP Quant 500 kit). Growth performance and fecal score data were analyzed using PROC MIXED (SAS) whereas R was used for predictive modeling of metabolomics data. Over the 28-d period post-transport, DMI was greater (P < 0.01) for 14 d than 2 and 4 d old calves; however, it did not differ between 2, 4, and 8 d old calves. Average daily gain (ADG) and feed efficiency (FE) were also greater (P < 0.01) for 14 d than 2, 4, and 8 d old calves. During wk 1 post-transport, the total number of days calves had scours was least (P < 0.01) for 2 and 14 d, intermediate for 4 d, and greatest for 8 d old calves. During wk 2, the total number of days with scours was less (P < 0.01) for 8 and 14 d (average of 2 d) compared with 2 and 4 d old calves (5 d). Additionally, the total number of days calves had scours during the first 2 wk post-transport tended (P = 0.08) to be greater for 2, 4, and 8 d than 14 d old calves. However, during wk 3 and 4 post-transport, there were no differences (P ≥ 0.58) in the total number of days with scours across transport age. Arginine methylation, d 7 of measurements, carnitine uptake defect, phosphatidic acid 16:0:18:2, methylenetetrahydrofolate reductase, sodium, triglyceride 18:2:34:4, threonine, α-aminobutyric acid, and glycolithocholic acid 3-sulfate were the most important features in terms of predicting the occurrence of scours. Overall, DMI, ADG and FE were less for calves transported at 2, 4, and 8 d than at 14 d of age, which could partially be attributed to differences in the incidence rate of scours. In addition, several plasma metabolites could be good predictors of scours in transported calves.