Effects of pre- and post-transport feeding protocols on the metabolism and physiological status of veal calves

Abstract

ABSTRACT: This experimental study aimed to investigate the effects of pre- and post-transport feeding protocols with varying volumes of milk replacer on metabolic and physiological variables of unweaned calves during and after long-distance transport by ferry and road. We monitored 2 commercial shipments of male dairy and beef × dairy calves (n = 116). Pre-transport, calves (n = 58/treatment) were fed 2 L the morning of transport or 6 L divided over 2 feeds the evening before and the morning of transport. Post-transport, calves were fed a conventional restricted protocol or 25% more volume per day (3.2 or 4.0 L/d, increasing to 5.8 or 7.2 L/d over 3 wk). We obtained blood samples and BW at 5 time points: (1) pre-transport at an assembly center (AC) in Ireland, (2) after 24 h of ferry and road transport at a lairage in France, (3) after a 13-h rest stop and 16.5 h of road transport at 2 veal farms in the Netherlands, (4) on d 12 and (5) on d 21 post-transport (total transport duration 53.5 h). Blood samples were analyzed for markers of energy balance (glucose, nonesterified fatty acids [NEFA], BHB), hydration (urea, electrolytes, albumin, hematological variables), physiological stress (cortisol), and muscle fatigue (lactate, creatine kinase). Linear mixed models were used to assess the effects of feeding protocols on physiological variables. Calves fed more milk replacer twice pre-transport had a better energy balance with significantly higher blood glucose at the lairage (estimated marginal mean [95% CI]: 3.68 [3.47–3.88] vs. 3.32 [3.13–3.51] mmol/L) and significantly less fat mobilization than calves fed less at the AC (NEFA: 0.10 [0.09–0.11] vs. 0.20 [0.18–0.23] mmol/L, BHB: 0.06 [0.05–0.07] vs. 0.11 [0.10–0.12] mmol/L) and lairage (NEFA: 0.60 [0.54–0.66] vs. 0.69 [0.62–0.76] mmol/L, BHB: 0.26 [0.22–0.29] vs. 0.35 [0.30–0.39] mmol/L), but not upon arrival at the veal farm (NEFA: 0.83 [0.75–0.92] vs. 0.65 [0.59–0.72] mmol/L). Calves fed more were also significantly less dehydrated throughout transport, with lower chloride levels overall (97.2 [96.3–98.0] vs. 95.6 [94.8–96.5] mmol/L) and lower urea (2.60 [2.21–2.99] vs. 3.68 [3.13–4.22] mmol/L) and potassium (6.67 [6.50–6.83] vs. 6.87 [6.71–7.04] mmol/L) at the lairage. By d 12 (next sampling after arrival), all blood variables except sodium and cortisol had normalized for all treatments. Post-transport, ADG was significantly increased for calves fed 25% more (0.47 [0.43–0.51] vs. 0.40 [0.36–0.43] kg/d). We conclude that feeding calves two 3-L milk feeds compared with one 2-L milk feed before long-distance transport reduced the negative impacts of prolonged fasting, especially regarding energy balance and hydration status. However, these positive effects were evident at the mid-transport lairage but were not sustained throughout the multiday journey. Calves fed more also experienced energy depletion, hypoglycemia, and dehydration, suggesting that even 6 L of milk replacer pre-transport does not fulfill the metabolic needs of calves during long-distance transport. These findings highlight significant welfare concerns with current transport practices, underscore the need to reassess feeding protocols during rest stops, and point to the importance of future research focused on shortening fasting periods and optimizing feeding protocols.

Keywords

• transport
• feed provision
• biomarkers
• calves