Feeding of high yielding dairy cows. 3. Roughage intake in high yielding cows when fed grass silage ad libitum

Ekern, A.

Meldinger fra Norges Landbrukshoegskole 51(32): 30


Accession: 000093083

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3. Studies of intake of roughage, expressed in terms of corrected roughage DM which is the sum of DM in silage, in hay and in treated straw plus 0.4 X DM in roots, were made in the trials described in parts 1 and 2. Total daily intake of DM/100 kg liveweight for the average cow was close to 3.0 kg with a maximum 3.20 and 3.21 kg on the moderate plane of feeding, and was reached during week 10 after calving. Some cows took more than 4 kg DM/100 kg during several weeks; the maximum reached was 4.36 kg during week 8 after calving. Voluntary roughage intake differed among years. On the moderate plane the largest intake was 1.89 kg corrected roughage DM/100 kg liveweight, and the smallest were 1.47 and 1.54 kg. The low intakes may have been related to the high concentration of organic acids in the silage given in those instances. There was wide variation in intake among cows on the same treatment, with differences from 30% more to 40% less than the average. There was a negative correlation between the average daily yield of 4% fat-,corrected milk (FCM) and average intake of corrected roughage DM. Intake of corrected roughage DM increased during early lactation to the highest value during week 10 or 15 in different experiments on the moderate plane and during week 16 or 18 on the high plane. After the peak intake it tended to level off slightly. In weeks 2 to 10 of lactation there was a negative and after week 14 a positive correlation between daily intake of corrected roughage DM/100 kg liveweight and daily yield of FCM. The correlation between daily corrected roughage DM/100 kg liveweight and week after calving was positive in early lactation and negative in later. The highest correlations were when both daily yield of FCM and week after calving were used in the multiple regression for predicting daily intake. These variables accounted for 5 to 49% of total variation. Cows on moderate feeding reached a maximum intake of roughage at a daily yield of 26.4 kg 4% FCM. Intake of roughage fell at an increasing rate at larger or smaller yield. Greatest intake of roughage on the moderate plane was at about week 16 of lactation. On the high plane maximum roughage intake was greatest at a daily yield of 18 to 20 kg FCM and in weeks 18 to 19 of lactation. The high plane gave significantly smaller voluntary roughage intake than the moderate, more pronounced in early lactation. For an increase of 1 kg in intake of concentrate DM corrected roughage DM decreased by 0.91 to 0.93 kg during weeks 3 to 6 and by 0.31 to 0.36 kg during weeks 19 to 26. When 1.8 kg hay was given in a ration of roots, concentrates and grass silage to appetite silage DM intake was reduced significantly and the increase in forage DM intake was not significant. Intake of forage DM was significantly decreased when 20 kg roots were included in the daily ration. For intake of 1 kg root DM forage DM decreased by 0.46 kg so that roots in the diet significantly increased total roughage DM and FU intakes; 1 FU roots could replace 0.4 FU forage and 0.6 FU concentrates.