Effect of the dietary oregano (Origanum vulgare) on Cu and Zn balance in weaned piglets

Abstract

A 4-week study conducted on 20 weaned piglets (average initial weight 15 kg) evaluated the effects of dietary oregano (Origanum vulgare) used in the presence/absence of phytase on the Cu and Zn balance, while reducing/eliminating their inclusion in the diet as inorganic salts. Oregano was harvested from the wild flora. The Cu and Zn concentrations that were taken into consideration (9.85 ppm and 53.31 pmm, respectively) were the consensus values obtained in an interlaboratory study. The piglets were assigned to 4 groups (C, E1, E2, E3), housed in individual metabolic cages and fed on corn-soybean meal-based diets. The diet of the control group (C) with addition of 1% inorganic mineral premix (MP), contained: 40.92 ppm Cu, 144.96 ppm Zn. The experimental diets differed from the C diet as follows: E1--3% oregano, 0% phytase (5000 PU/g), 0% MP; E2--3% oregano, 0.01% phytase, 0% MP; E3--3% oregano, 0% phytase, 0.5% MP, E4--3% oregano, 0.01% phytase, 0,5% premix. For groups E1, E2, E3 and E4, 0.5% Zn of the MP were included in the diet, because the dietary oregano amount did not meet the requirements (NRC) for piglets. The mineral balance was determined during 3 periods of 5 days each. The levels of Cu and Zn were measured by FAAS in the samples (weekly samples/piglet) of ingesta, faeces and urine. It was noticed that although the dietary Cu ingested by the groups without MP was 75% (10.08 ppm) lower than C, the absorption coefficients were only 47% (28.83) lower than for group C (54.22%), while in the groups with 0.5% MP, the absorption was just 10% (48.86%) lower than for group C. For Zn, where the amount ingested by the experimental groups was 33% (97.62 ppm) lower than for group C, the absorption coefficients were just 20% (46.3%) lower than for group C (57.64%). No significant differences were noticed for Cu and Zn in terms of apparent absorption, between the groups with/without phytase. The deposits of Cu and Zn in the main organs and serum (from slaughtered piglets) were also evaluated.