UTILIZAÇÃO DO GRÃO DE CEVADA EM SUBSTITUIÇÃO AO MILHO EM DIETAS PARA VACAS EM LACTAÇÃO

In the present research work the effects of partial and total substitution of ground corn grain by dry rolled barley on the milk production and composition were evaluated. Twenty-eight Holstein cows with an average of 125 days in milk were used in a 4x4 latin square design. Once a day, the diet was supplied in a totally mixed ration. Four levels of corn substitution by barley were tested (T1 – 0% barley; T2 – 33% barley; T3 –67% barley; and T4 – 100% barley. The experiment was carried out during 105 days. Cows were milked twice a day and contents of fat, protein, milk total solids, and somatic cell count (SCC) were established twice in each treatment period and the milk urea nitrogen (MUN) at the end of each period. The dry matter intake decreased in a linear fashion when barley replaced corn in the diet. However, the ingestion of crude protein, neutral fiber detergent and acid fiber detergent were not affected when substituting corn by barley. Linear reduction was observed in milk yield, fat corrected milk production and fat and protein contents of the milk, while the protein percentages increased in a linear way. No effect was registered concerning the levels of substitution on the protein production, total solids of the milk, SCC, MUN and on the conversion efficiency.