Blood parameters of young calves at abattoirs are related to distance transported and farm of origin

摘要

Nonreplacement dairy calves, or bobby calves, arefasted and transported to abattoirs from as young as 5d of age in Australia. The aims of this cross-sectionalobservational study were (1) to assess the welfarestatus, as measured by blood parameters, of bobbycalves in the commercial supply chain after transportand lairage, and (2) to assess whether distance andduration of transport are risk factors for poor bobbycalf welfare, as measured by blood parameters. Wehypothesized that bobby calves transported greaterdistances would be more likely to show evidence ofcompromised welfare, as measured by blood indicatorsof hydration, energy status, and muscle fatigue ordamage. We also hypothesized that there would be alarge amount of variability in indicators of energy statusbetween calves from different farms. We analyzedblood samples collected at slaughter over a spring andan autumn calving period from 4,484 Australian bobbycalves aged approximately 5 to 14 d old from 3 differentstates, after transport, fasting, and lairage. Packedcell volume (PCV), plasma glucose, and serum urea,total protein, β-hydroxybutyrate (BHB), and creatinekinase (CK) were measured. Radio frequency identificationear tag data were used to estimate the distancethat the calves were transported and to identify thefarm of origin. Data were analyzed using linear mixedmodels, except for BHB, which was analyzed using aGoodman-Kruskal gamma test due to left censoring ofthe data. Twelve percent of calves showed evidence ofanemia (PCV less than 0.23 L/L), and 11% had ureaconcentrations consistent with dehydration (urea morethan 7.7 mmol/L). Thirty-six percent of calves had CKactivity above normal resting values, and 1% of calveshad CK >2,000 U/L, indicating muscle fatigue or damage.Distance transported had significant effects on allblood variables except urea and BHB. With increasingdistance transported, calves were more likely to showevidence of a negative energy balance (low plasma glucose)or dehydration (high PCV or total protein). Theestimated effect of distance overall was small, but forcalves transported more than 500 km, plasma glucoseconcentration declined more per kilometer. The calves’farm of origin accounted for a reasonable amount ofthe random variation between calves for plasma glucose(20%). Our results suggest that longer transportdistances may increase the risk of poor calf welfare(dehydration, negative energy balance) after transport,and on-farm calf management (e.g., nutrition, timing offeeding before transport) may affect transported calves’energy status; improving this area could result in betterenergy availability during fasting.