# A Review of Biochar Properties and Their Utilization in Crop Agriculture and Livestock Production
## 5 Biochar as a Feed Additive
Researchers prepared a mixture of feed and BC (~7% of BC by mass) with a nutrient content similar to one in the regular feed, but where there was no need to include limestone, salt, and tricalcium phosphorus in the mixture. The results of the BC amendment, however, were negative, resulting in 8% higher feed intake, 2% lower weight gain, 11% worse feed conversion ratio, and higher mortality. Such an effect is explained by the high (99 ppm) As content in the BC and its toxic activity. In similar research conducted one year later, [PERSON] et al. [56] investigated 2% and 4% poultry litter BC feedamendment with lower toxic heavy metals content--birds fed with a 2% BC amendment had increased feed conversion ratio by 7% and birds fed with a 4% amendment had live weight gain decreased by 9%. Those negative effects had to be corrected with phytase inclusion to the feed. [PERSON] et al. [57] mixed jarrah wood BC with molasses in a 3:1 ratio and fed it directly to cows. The influence of BC supplementation of diet on cows was not the main subject of the investigation, but no negative effects on animals were reported, and beneficial effects were suggested to have occurred, such as toxin absorption and possibly transformation of organic matter to carbohydrates. Cow dung-BC mixture that was incorporated into the soil had a positive effect on soil properties, which was related to an easier transfer of nutrients from the cow's gut and dung to the soil. [PERSON] et al. [58] supplemented layer chicken diet with 4% (by mass) of woody green waste BC and investigated alterations to the overall richness and diversity of the intestinal bacterial community. Supplementation did not affect bird weight, but increased egg productivity by 1.2%, increased average egg weight by 3%, improved feed conversion ratio by 8%, and lowered feed intake by 2%. However, feed amendment with BC did not result in altered diversity and richness of the microbial community within the cloaca microbiota of the laying hens. In another research, [PERSON] et al. [59] point out that BC is a lesser-known yet promising alternative feed amendment compared to the more popular ones such as bentonite or zeolite. In the research, laying hens were under dietary treatments involving 1%, 2%, and 4% (_w/w_) of woody green waste BC where production parameters and exceta attributes of the hens were investigated. The addition of 2% and 4% of BC to the diet significantly increased egg weight by 5% and 4% respectively. Moreover, a 2% BC amendment significantly increased egg yield by 13%, while feed intake was 7% lower for birds fed twice higher BC concentration and the feed conversion ratio was lower for all the BC treatments by 10%, 14%, and 12%, respectively. For hens of 36 weeks of age, 2% and 4% BC treatments increased egg shell weight by 13% and 4%, respectively, increased shell thickness by 10%, and increased shell breaking strength by 19% but also reduced yolk color score by 19%. For exceta parameters, 2% and 4% BC treatments reduced exceta N content by 17% and 26%, respectively. Another research by [PERSON] et al. [60] investigated the effect of woody green waste BC diet inclusion on poultry manure properties. The addition of 1%, 2%, and 4% (by mass) of the BC to the laying hens and chicken broilers diet was made, and their exceta were examined. Increasing contents of BC were associated with a decreased water content of laying hens exceta. Furthermore, 2% and 4% BC amendments significantly lowered manure nitrogen (N) content by 17% and 27%, respectively; however after 35 days of manure decomposition, N losses of the 4% BC treatment were significantly lower and 45% more of N was retained in the exceta. Manure from the 2% and 4% BC amended feed treatments possessed 25% and 45% higher C content, respectively. Ammonia emission was higher from the 2% and 4% BC treatment groups by 47% and 43%, respectively. Manure from BC supplemented broilers, as well as laying hens, was also used to form size class favored granules used for application in fertilizer equipment.