their reduction indirectly reduced the production of methane.
Antioxidant potency The study also investigated the antioxidant capacity of the leaf extract. It appeared that the plasma malondialdehyde (MDA) concentration decreased with leaf extract supplemen- tation, while the levels of glutathione peroxidase (GPx), su- peroxide dismutase (SOD) and catalase (CAT) enzymes in- creased. The reduced MDA concentration is an indicator of reduced oxidative degradation of lipids, while the increased level of plasma antioxidant enzymes indicates improved anti- oxidant capacity. Compounds of the leaf extract effectively impair the radical chain reactions by competing with the re- active host components, thus stopping the propagation of the oxidation chain.
Nutrient digestibility and growth The researchers found lower nutrient digestibility, growth and weight gain from the 20ml leaf extract diet, but the 10ml diet was not different from the unsupplemented (0ml) diet. These results could be attributed to the possible negative ef- fects of some of the extract’s plant secondary metabolites (e.g. condensed tannins, saponins, alkaloids) on nutrient di- gestibility, which in turn affects nutrient absorption. During the study feed in take was low, what probably contributed to low growth rates. Reduced feed intake could be related to re- duced palatability; encapsulation of these extracts would help overcome this.
In conclusion The leaf extract when supplemented at 10ml/calf/day manipulates rumen fermentation in mitigating methane production without any negative effects on the growth performance of calves. A reduction in methane production spares the energy for calf production and helps curb the negative effects of global warming due to this greenhouse gas emission. Apart from increasing the plasma antioxidant enzymatic activities, the leaf extract supplementation, irrespective of the dosage, shows a marked reduction in faecal pathogenic bacterial counts and increased antioxidant capacity, indicating improved health status.
This article is based on the original article by A. Hassan, S.H. Abu Hafsa, M.M.Y. Elghandour, et al. 2020. Influence of Corymbia cit- riodora leaf extract on growth performance, ruminal fermenta- tion, nutrient digestibility, plasma antioxidant activity and fae- cal bacteria in young calves, Animal Feed Science and Technology, Vol 261, 2020, 114394. 10.1016/j.anifeedsci.2020.114394.
Table 2 – Effect on calves fed C. citriodora leaf extract.
Parameter 0
Faecal pathogenic bacteria E. coli x 105
Enterococcus x 106 Clostridia x 106
Plasma antioxidant activity MDA (µmol/l) GPx (µkat/g Hb) SOD (µkat/g Hb) CAT (µkat/g Hb)
Protozoan count (x105 /ml)
ml CC/calf/day 10
20
18.67 11.33 8.67 17.67 12.67 7.67 8.33 5.67 2.67
35.85 30.88 26.93 3.62 5.28 6.44 11.96 13.43 14.63 2.57 3.65 4.37 6.01 5.07 4.17
▶ ALL ABOUT FEED | Volume 28, No. 7, 2020 9
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