Abstract
Iron is one of essential trace minerals for beef cattle while too much intake will have negative impacts on animal health and performance. In this study, we surveyed iron concentrations in feed ingredients and final diets for beef cattle in Kochi prefecture, Japan. In cow-calf operations and fattening beef cattle farms, all feed ingredients including roughage, concentrate, commercial compound feed, mixed ration and supplements which were given to cows (19 farms), growing calves (22 farms), early fattening cattle (12 farms) and late fattening cattle (19 farms) were collected. Iron concentrations of total 164 samples were measured by atomic absorption spectrometry. Iron concentrations were highly variable among samples from different farms in rice straw, timothy hay, Italian ryegrass hay, commercial compound feed labeled for growing calves, commercial compound feed labeled for milking cows, and own mixed concentrate ration prepared for growing cattle. Compared with iron concentration given in the Standard Tables of Feed Composition in Japan (2001), significantly (P<0.05) lower average concentration was found in Italian ryegrass hay, oats hay, fresh sorghum forage and wheat bran. Then we estimated iron concentration of final diet of each farm by calculation from iron concentration of each ingredient and its daily intake based on the information from feeders. In all farms and production stages, estimated iron concentrations in final diets met the requirement of iron (50 mg/kg) and were below the maximum tolerance level of iron (1,000 mg/kg) proposed by Japanese Feeding Standard for Beef Cattle (2008). However, iron concentration of final diet exceeded 250 mg/kg, which has been suggested to have a negative impact on copper status of cattle, in 7 farms for beef cows, 10 farms for growing calves, two farms for early fattening cattle and one farm for late fattening cattle.
