Fineness and concentrate to low quality roughage ratio of complete diets for dairy cows. I. 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: 000889642

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II. From day 10 to day 130 of lactation, 12 groups of 3 Friesland cows were used in a changeover design trial with 3 periods of 40 days. 9 diets were used with roughage:concentrate ratios of 35:65, 50:50 or 65:35 ground through screen sizes 6, 13 and 19 mm. The roughage was maize straw and the concentrate was based on maize grain and sunflower oilmeal, diets were unpelleted and given to appetite. Increasing concentrate and decreasing screen size increased feed intake by 44% but decreased fibre digestibility (P <0.01). Mean daily FCM yield on diets with concentrate 35, 50 or 65% was 16.1, 16.7 and 17.0 kg with 6 mm screen size, 15.1, 16.6 and 16.8 kg with 13 mm and 14.9, 15.8 and 16.3 kg with 19 mm. Increasing concentrate from 35 to 50% significantly increased yield with the screen size 13 and 19 and decreasing screen size from 19 to 13 mm increased yield with 35% concentrates (P <0.01). Similar trends were observed for milk fat yield but differences were not significant, however decreasing screen size or increasing concentrate % significantly increased protein yield (P <0.01) except in the case of the diet with 65% concentrate. Changes did not affect milk fat content, 3.8-3.5%, TS or protein %.