Effect of the administration of different levels of solid feed on production performance, welfare, health status and antibiotic use in veal calves for white meat production

The study aimed at evaluating the effect of five different levels of solid feed administration on production performance, animal welfare, health status and antibiotic use in veal calves for white meat production. A total of 1750 male Friesian calves (49.61 +/- 2.06 kg initial live weight) were randomly divided into five different dietary treatments (193 +/- 2.59 days). The five experimental groups differed in terms of amount of solid feed (SF) and milk replacer (MR) administered during the entire fattening period: i) "Solid feed 180 kg" (SF180); ii) "Solid feed 225 kg" (SF225); iii) "Solid feed 270 kg" (SF270); iv) "Solid feed 330 kg" (SF330); v) "Solid feed 380 kg" (SF380). Growth performances were evaluated as final live weight (FW) and average daily gain (ADG). At slaughter, dressing percentage (DP), hot carcass weight (HCW), carcass colour classification, and percentage of calves with a carcass weight lower than 110 kg, were recorded. Welfare and health status were assessed in terms of morbidity, mortality, number of calves moved into hospital pen, haemoglobin value and the incidence of calves with haemoglobin level lower than 7.25 g/dL (4.5 mmol/L) at 80 days of breeding. Antibiotic use was included (grams of active principle/head). The results showed a positive effect of increasing solid feed in terms of production performance and health status. A solid feed administration higher than 225 and 330 kg, significantly improved the ADG (SF180: 1.12 +/- 0.08 kg/d; SF225: 1.13 +/- 0.08 kg/d; SF270: 1.17 +/- 0.07 kg/d; SF330: 1.19 +/- 0.06 kg/d and SF380: 1.23 +/- 0.07 kg/d) and the FW (SF180: 265.61 +/- 14.78 kg; SF225: 268.97 +/- 15.35 kg; SF270: 279.34 +/- 13.40 kg; SF330: 276.31 +/- 11.07 kg and SF380: 286.13 +/- 14.62 kg). Similar trends were found in HCW, with calves from the SF180 and SF225 groups showing the significantly lowest weights (SF180: 142.47 +/- 6.39 kg; SF225 143.66 +/- 7.07 kg), followed by SF270 and SF330 groups (SF270: 148.78 +/- 6.57 kg; SF330: 146.28 +/- 9.45 kg), and calves from SF380 the highest weight (SF380: 150.65 +/- 9.43 kg). The increase in solid feed administration reduced the incidence of carcasses in the << white >> colour category, while it increased in the pinkish category. Administration of solid feed above 270 kg, significantly reduced morbidity and mortality, with lower values in groups SF380 (morbidity 20.00% and mortality 3.71%) and SF330 (morbidity 22.85% and mortality 4.29%) compared to groups SF270 (morbidity 25.71% and mortality 5.14%), SF225 (morbidity 28.57% and mortality 5.71%) and SF180 (morbidity 28.57% and mortality 5.43%). Consequently, a consumption of solid feed above 270 kg significantly reduced the use of antibiotics (SF180: 120.83 +/- 45.10 g/head; SF225: 124.11 +/- 45.46 g/head; SF270: 118.97 +/- 50.25 g/head; SF330: 105.57 +/- 41.67 g/head; SF380: 103.70 +/- 40.30 g/head). Higher solid feed administration significantly increased the haemoglobin level, with less calves with haemoglobin lower than 7.25 g/dL in group SF270 compared to SF225 and SF180 and in group SF330 and SF380 groups compared to SF270. The results of the study show that the administration of solid feed oriented towards an ad libitum availability, significantly improves both welfare and growth performance, in agreement with the law's indications aimed at maximizing welfare and reducing the consumption of antibiotics in livestock production.