Digestibility, Ruminal Enzyme, Fermentation Characteristics and Certain Blood Biochemical Parameters in the Calves Supplemented with Humic Acid

Waleed K. Abouamra¹Abdelslam M. A. Amhabj²Hamdan M. Tawfik¹Ahmed A. Ayad¹Mohsen Farghaly³Hayam M. A. Monzaly⁴Mohsen A. Khormi⁵Ramadan Taha⁶Ahmed Ahmed^6,7Montaser Elsayed Ali^1*

• ¹Department of Animal Production, Faculty of Agriculture, Al-Azhar University,, Assiut, Egypt
• ²Department of Animal Production, Faculty of Agriculture, Sirte University,, Sirte, Libya
• ³Department of Animal Production, Faculty of Agriculture, Assiut University,, Assiut, Egypt
• ⁴Sheep and Goat Research Department, Animal Production Research Institute, Agriculture Research Centre,, Giza, Egypt
• ⁵Department of Biology, College of Science, Jazan University, P.O. Box. 114,, Jazan, Saudi Arabia
• ⁶Department of Biology, College of Science, King Khalid University,, Abha, Saudi Arabia
• ⁷Prince Sultan Bin Abdelaziz for Environmental Research and Natural Resources Sustainability Center, King Khalid University,, Abha, Saudi Arabia

This study aimed to evaluate the effect of humic acid (HA) on the growth performance, nutrient digestibility, ruminal fermentation, ruminal enzyme activity, and certain blood biochemistry. Forty-five calves (11 ± 0.25 months of age; 280 ± 5.55 kg BW) were divided into three equal groups: the control group received the basal diet composed of a concentrate feed mixture (CFM) with roughages. The treatment groups received the same basal diet with a supplement of 1% and 2% humic acids for CFM, respectively. The study revealed that the treatment groups had significantly lower total dry matter intake (P = 0.029). The treatment groups were higher (P = 0.013) in ether extract (EE) digestibility and digestible crude protein (DCP) (P = 0.001) than the CFM group. However, ammonia nitrogen (NH3-N, mg/100 ml) was significantly lower (P = 0.012) in the 1% HA and 2% HA groups compared to the CFM group. The 2% HA group had significantly higher (P = 0.001) proportions of acetate and propionate compared to the 1% HA and CFM groups. The treatment groups had significantly higher (P = 0.001) α-amylase, lipase, urease, and protease activities compared to the CFM group. Also, total soluble protein present in the rumen liquor concentration was higher (P = 0.006) in 1% HA groups compared to CFM groups. The 2% HA group had higher (P = 0.049) glucose concentrations than the CFM group. In conclusion, humic acid supplementation at 1% or 2% may improve nutrient digestibility and rumen fermentation efficiency, enhance enzymatic activity, and support normal blood profiles for calves.