Evaluation of apple (Malus domestica) cider vinegar and garlic (Allium sativum) extract as phytogenic substitutes for growth-promoting dietary antibiotics in sexed broiler chickens

Abstract

Tightening global regulations on the use of sub-clinical dietary antibiotics to enhance broiler growth are in response to increasing concern about the risk of resistance and their residues in animal products. The study evaluated the potential of apple cider vinegar (ACV) and garlic extract (GAE) as safer, phytogenic alternatives. A batch of 390 mixed-sex Ross 308-day-old broiler chicks was received into an open, deep litter house, and feather-sexed in the second week into 30 experimental units of 13 birds per 2.03 m 2 pen. From days 1 to 22, all chicks were on a 200g/kg crude protein, coccidiostat treated commercial starter diet. During the grower (16-28 days) and finisher (29-42 days) phases, chick pens were assigned treatments in a 2 (sex) x 5 (additives) factorial experiment replicated three times. The GAE was a pure extract, while ACV was produced by fermenting 1000g fresh apple and 80g supplementary brown cane sugar in 1.3L water for 4 weeks. The five treatments comprised antibiotic (15% granular zinc bacitracin and 12% valinomycin sodium, each at 500g/tonne) grower (190 g kg -1 crude protein, 13.0 MJ ME kg -1) and finisher (165 g kg -1 crude protein, 13.2 MJ ME kg -1) commercial diets with untreated drinking water as positive controls (PC), antibiotic-free duplicates of the PC diets with untreated drinking water as the negative controls (NC), with 3ml/L filtered ACV in drinking water (T1), 2ml/L filtered GAE treated drinking water (T2), or mixed (3ml/L ACV + 2ml/L GAE) additive drinking water (T3). Males had higher (P<0.05) feed intake than females in both growth phases. Birds on the PC gained more (P<0.05) weight than others. Birds on the PC consumed more feed (P<0.05) during the finisher phase than T1, T2 and the NC. Birds on the PC had a lower (P<0.05) grower-phase FCR than others, though with lower (P<0.05) FCR during the finisher phase for birds on T1 and T3. Birds on the PC had higher (P<0.05) percent spleen weight than birds on T1, with smaller proventriculus (P<0.05) than on NC, T1, T2 and T3, and smaller gizzard weight than birds on the T2 and T3. Birds on the NC exhibited less dressing percentage (P<0.05) than all other treatments. Meat pH was higher (P<0.05) in males. In conclusion, in contrast to dietary antibiotics, except for improved dressing percentage, the ACV and GAE did not express phytogenic benefit at the experimental dosage.