Document type: scientific Document type: published in Irish Veterinary Journal
Authors: Siegmann, Luca L. van Dijk, Niamh L. Field, Gearoid Sayers, Katie Sugrue, Cornelis G. van Reenen, Eddie A. M. Bokkers, Muireann Conneely
Abstract in French (translation): Effects of age and feeding protocols on the metabolic and physiological status of unweaned calves during and after long-distance transport
Long-distance transport and the associated prolonged periods of fasting place a heavy strain on the physiological status of young calves, leading to energy loss, dehydration, and potentially hunger and exhaustion. Older calves, with greater body reserves, can better tolerate fasting, while administering larger volumes of milk replacer before transport could help maintain energy balance and hydration. The objective of this study was to examine how calf age and pre-transport feeding protocols influence the physiological status of unweaned calves during and after long-distance transport by road and ferry. We monitored a commercial transport of 138 male dairy calves from a collection center (CC) in Ireland, via road and roll-on/roll-off ferry, to a holding pen in France, and then by road to a calf farm in the Netherlands (total transport time: 51 h). The study design was a 2 × 2 factorial design with the factors “calf age” (2–3 or 4–5 weeks) and “pre-transport feeding protocol” (2–4 L of milk replacer). We collected four blood samples (CA, holding pen, arrival, 7th day after transport) and analyzed them for 15 variables indicating energy balance, hydration status, muscle fatigue, and physiological responses to stress. Twenty calves were fitted with continuous glucose monitors (CGMs) to measure interstitial glucose levels from 13 hours before to 90 hours after departure. Body weight was recorded at the shipping center, the holding pen, upon arrival, and 7 and 21 days after transport. The effects of age and feeding protocol on physiological responses were evaluated using mixed-effects linear models with repeated measures and random effects for the calf and farm of origin. Younger calves weighed less overall than older calves (49.8 vs. 53.0 kg, P = 0.004) and at all sampling times; they had higher plasma glucose concentrations than older calves overall (4.61 vs. 4.42 mmol/L, P = 0.038) and at all sampling times except in the holding pen, lower sodium concentrations upon arrival (139.9 vs. 140.8 mmol/L, P = 0.034) and lower chloride concentrations at the reception center (97.4 vs. 99.0 mmol/L, P ≤ 0.001) and in the holding pen (96.6 vs. 97.5 mmol/L, P = 0.009). Calves fed 2 L prior to transport had lower CGM-measured glucose values for two hours after feeding at the receiving center and higher urea concentrations in the holding pen (4.01 vs. 3.10 mmol/L, P ≤ 0.001) than calves fed 4 L. Although feeding 4 L versus 2 L prior to transport had some positive effects on the calves’ energy balance and hydration, our results suggest that pre-transport feeding has only a limited capacity to mitigate the negative effects of transport and prolonged fasting on the calves’ physiological status, particularly during multi-day transports. The effects of age on calf resilience were few and inconclusive, and further research should include a broader age range.
Preview: Long-distance transport and associated extended fasting periods challenge the physiological state of young calves, leading to energy loss, dehydration, and potentially hunger and exhaustion. Older calves with greater body reserves may better withstand fasting, while providing larger volumes of milk replacer pre-transport could help sustain energy balance and hydration. The aim of this study was to investigate how calf age and pre-transport feeding protocols affect the physiological status of unweaned calves during and after long-distance road and ferry transport. We followed a commercial shipment of 138 male dairy calves from an assembly centre (AC) in Ireland via road and roll-on-roll-off ferry to a lairage in France and then via road to a veal farm in the Netherlands (total transport duration 51 h). Study design was a 2 × 2 factorial with factors calf age (2–3 or 4–5 weeks) and pre-transport feeding protocol (2–4 L of milk replacer). We collected four blood samples (AC, lairage, arrival, Day 7 post-transport) and analysed them for 15 variables indicating energy balance, hydration status, muscle fatigue, and physiological stress responses. Twenty calves were fitted with continuous glucose monitors (CGMs) to measure interstitial glucose from 13 h before to 90 h after departure. Body weight was recorded at AC, lairage, arrival, Day 7 and 21 post-transport. The effects of age and feeding protocol on physiological responses were assessed using linear mixed models with repeated measures and random effects for calf and farm of origin. Younger calves weighed less than older calves overall (49.8 vs. 53.0 kg, P = 0.004) and at all sampling moments; they had higher plasma glucose concentrations than older calves overall (4.61 vs. 4.42 mmol/L, P = 0.038) and at all sampling moments except lairage, lower sodium concentrations at arrival (139.9 vs. 140.8 mmol/L, P = 0.034) and lower chloride concentrations at AC (97.4 vs. 99.0 mmol/L, P ≤ 0.001) and lairage (96.6 vs. 97.5 mmol/L, P = 0.009). Calves fed 2 L pre-transport had lower CGM glucose readings for two hours after feeding at AC and higher urea concentrations at lairage (4.01 vs. 3.10 mmol/L, P ≤ 0.001) than calves fed 4 L. Although feeding 4 L compared to 2 L before transport had some positive effects on calf energy balance and hydration, our findings suggest that pre-transport feeding has only limited capacity to alleviate the negative impacts of transport and prolonged fasting on the physiological status of calves, especially during multi-day transport. Effects of age on calf resilience were few and inconclusive, and further research should include a larger age range.
