Fineness and concentrate to low quality roughage ratio of complete diets for dairy cows 1. intake and digestibility under ad libitum feeding conditions

Liebenberg, L.H.P.

South African Journal of Animal Science 9(3): 215-220


ISSN/ISBN: 0375-1589
Accession: 005464289

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Lactating cows (36) were used in a trial with a partially balanced change-over design to determine the effect of the fineness of roughage and concentrate to roughage ratio on intake and digestibility. Nine rations were used with combinations of 3 screen sizes (6, 13, 19 mm) and 3 concentrate percentages (35, 50, 65). Maize straw was included as a poor quality roughage component. An increase in the concentrate component and a decrease in screen size resulted in an increased intake of 44%. Each combination of screen size and concentrate to roughage ratio resulted in a different intake. The fineness of a ration was less important at high concentrate levels. Intake increased with increasing concentrates in the diet which indicated that at the 65% concentrate level the possible point of constant DE and N digestibilities. Apparent fiber digestibility was significantly (P < 0.01) decreased by 0.3% and 0.5% with 1% increase in concentrate and 1 mm decrease in screen size, respectively.