Influence of Mineral Supplements on the Growth of Calves, Digestibility of the Rations and Intra-Ruminal Environment

Abstract

Two experiments were conducted to study the influence of various supplements to a low-ash ration composed mainly of corn cobs and corn starch. In the first experiment feed consumption and growth were studied and in the second experiment digestibility and intra-rumen environmental factors were studied. The addition of a special mineral supplement composed of the carbonate or bicarbonate salts of calcium, magnesium, sodium and potassium, to a ration of corn cobs, corn starch, soybean oil meal and urea, improved feed consumption and tended to improve growth. Alfalfa hay or alfalfa ash supplements gave somewhat smaller responses that were not statistically significant in many cases. Feeding the special mineral supplement or alfalfa ash resulted in an alkaline urine while the basal ration resulted in an acid urine. Alfalfa ash supplementation did not improve the apparent digestibility or nitrogen retention of a low-quality roughage ration composed mainly of ground corn cobs and corn starch with small amounts of timothy hay and soybean oil meal. The alfalfa ash did significantly increase the percentage of water and ash in the rumen ingesta and the daily water consumption. The results of correlation analyses indicated that the more fluid rumen ingesta were associated with an increased rate of digestion as measured by the 24-hr, loss in weight of cotton loops suspended in the rumen. The results of the correlation analyses also indicated that rumen pH depends primarily on the concentration of volatile fatty acids but may also be influenced by the water and ash contents of the rumen ingesta. Fluctuations in freezing point of rumen fluid could be attributed primarily to variations in the volatile fatty acid content.