Studies on the Productive Value of Roughages and Concentrates for Lactation

Several workers have observed that when dairy cows are fed an all-roughage ration following parturition, milk production declines steadily as the body fat is depleted and then becomes relatively constant at a level which can be maintained by the roughage consumed. At this time, replacing part of the hay with concentrates supplying an estimated equivalent amount of total digestible nutrients (TDN) results in increased milk production. Huffman and Duncan They suggest that prolonged feeding of hay alone has depleted the reserves of this factor(s), which had been stored in the cow's body during previous grain feeding. The inclusion of concentrates in the ration at this time, it is postulated, supplies the factor(s) and gives the cow the capability for increased milk production. Since the feeding of purified starch or sugar, instead of corn grain, did not increase milk yield, it was thought that energy alone was ineffective.