Effect of the administration of a blend of essential oils, bioflavonoids, and tannins to veal calves on growth performance, health status and methane emissions.
Abstract
The aim of the present study was to prove the efficacy of feeding a coated blend of essential oils, combined with bioflavonoids and tannins, in the solid feed of fattening veal calves on growth performance, health, and methane (CH4) emissions.
A total of 541 Holstein Friesian intact male calves were allotted at the arrival into two groups: i) Control, standard milk replacer and solid feed (280 calves; age: 24 days; arrival weight: 50 kg); ii) Treatment, standard milk replacer + standard solid feed supplemented with 0.3 g/100 kg live weight of the coated blend of natural compounds (261 calves; age: 24.5 days; arrival weight: 51 kg).
The growth performances, such as average daily gain (ADG), final weights, solid feed intake (FI), milk replacer intake, feed conversion rate (FCR) and carcass weights, were evaluated, as well as the mortality rate and the incidence of diseases. The emissions of CH4 were monitored continuously, using two Cynomys devices.
The Treatment have led to a significant improvement of the ADG (1.116 vs 1.055 kg/head/d in the Control group) (P=0.005). Consequently, the final (266.5 vs 255.7 kg live weights in the Control group) (P=0.0096) and carcass weights (137.9 vs 133.1 kg in the Control group) (P=0.034) were improved in treated animals. The total (333.48 vs 310.75 kg of solid feed per cycle in the Control group) (P<0.0001) and daily (1.697 vs 1.587 kg/head/day in the Control group) (P<0.0001) solid feed intakes were significantly higher in treated animals, while the milk replacer was fixed in the two groups. Also, there was a tendency toward a better FCR in treated animals (2.84 vs 2.93 in the Control group) (P=0.08). No effects were detected in terms of mortality rate, incidence of diarrhoea and of first cases of bovine respiratory disease (BRD). However, there was a tendency toward a significant reduction in the incidence of BRD relapses in the Treatment group (3.08 vs 16.4 % on the total animals and 15.17 vs 19.71 % on the first treatment in the Control group) (P=0.053). The treatment reduced also the average CH4 (90.97 vs 86.20 g/m3 in the Control group) (P<0.0001), starting to be effective from week 8 of the trial.
In conclusion, the results of the present trial highlighted that the inclusion of a blend of essential oils, bioflavonoids, and tannins in the solid feed of white veal calves can be an effective strategy to increase the production efficiency, while tackling the use of antimicrobials, improving animal welfare, and counteracting the environmental impacts.
