Nutrient digestibility in lambs supplemented with different dietary manganese sources

The objective of this experiment was to compare the effect of different dietary manganese source on distribution of Mn, Zn and Cu in the ruminant digestive system and the nutrient coefficients of apparent total tract digestibility (CTTAD) of lambs supplemented with the current maximum total content of manganese allowed in the EU (150 mg Mn/kg). The CTTAD for Mn, dry matter (DM), organic matter (OM), crude protein (CP), acid (ADF) and neutral detergent fibre (NDF) were estimated using both the method of total faecal collection and titanium dioxide (TiO2) as an indigestible marker. In total, 18 female lambs of the Improved Valachian breed (21.1 ± 2.1 kg initial body weight) at the age of 7 months were randomly allocated into three dietary treatments and were fed for 16 weeks an unsupplemented diet (Control, 34.7 mg Mn/kg of DM) or the identical diet supplemented with manganese up to a total content 150 mg Mn/kg either from manganese sulphate (MnSO4) or manganese chelate of glycine hydrate (MnGly). Regardless of the source, feed supplementation with manganese increased Mn concentrations in the liver (P<0.001) and duodenal mucosa (P<0.01) compared to the control. Increased Mn concentration in the jejunum was only measured in lambs supplemented with sulphate. The greatest blood Mn levels were recorded in lambs fed the diet supplemented with the chelated Mn source (P<0.05) compared with animals receiving the control diet. Similarly, the bacterial fraction of the rumen content contained the highest Mn content in lambs given MnGly, while Mn concentration in the total rumen content and the protozoal fraction of rumen content was higher in both supplemented treatments, regardless of the Mn source. All supplemented lambs showed increased Zn levels and decreased Cu in the protozoal fraction in comparison with the control animals. The digestibility measurements showed greater CTTAD for CP and OM (P<0.01) in all supplemented lambs compared to the control, although the CTTAD for DM, NDF and ADF (P<0.05) was significantly increased in lambs fed the MnGly diet. The CTTAD for Mn was not influenced by the source of dietary Mn. The presented results showed no differences between dietary Mn sources either in mineral distribution in the ruminant digestive tract or the apparent total tract digestibility; however, it seems that intake of the manganese chelate of glycine hydrate in feed may increase fibre digestibility and Mn utilisation by rumen bacteria in lambs.