Field experiments at Sutton Bonington between 1970 and 1974 tested how crop yields were affected by hand weeding at different stages in the life of early-and latesown crops. Losses where weeds were never controlled ranged from 95 % where tallgrowing Chenopodium album L. predominated to 50% when Stellaria media (L.) Vill. and Tripleurospermum maritimum L.) Koch ssp. inodorum Hyl ex. Vaarama (T. inodorum) were most involved.

1985). Systems of concentrate allocation for dairy cattle 3. A comparison of two at-rate feeding systems at two amounts of concentrates. ABSTRACTIn a 20-week experiment beginning at week 3 post partum, autumn-calving dairy cows were offered either a flat rate of concentrates in which all the cows received the same daily amount throughout the experiment (G). or a flat rate based on their individual milk yield at 2 weeks post partum (I). Two amounts of concentrates were compared and grass silage was available ad libitum. The amounts of concentrate were 6 kg/day (6) and 12 kg/day (12). In the I treatments the ranges of individual inputs were 4 to 8 and 9 to 15 kg/day for the 6 and 12 kg/day treatments respectively. For treatments 6G, 61, 12G, and 121 respectively, mean milk yields were 25-5, 25-7, 28-9 and 27-6 kg/day; mean live-weight changes +0-05, +0-04, +0-19 and +0-27 kg/day; and mean silage dry-matter intakes 11-1, 11-2, 8-1 and 7-5 kg/day. The differences between systems of allocation were not significant, but differences between amounts of concentrate offered were significant. The system of allocation had no significant effect on milk composition. In the residual period (2 weeks indoors and 19 weeks grazing) there were no significant effects on performance. The mean 305-day milk yields for 6G, 61, 12G and 121 respectively were 6376, 6422, 6720 and 6597 kg.

Ninety-six lactating British Friesian cows were offered ad libitum two grass silages having the following analyses: 181 and 241 g dry matter per kg fresh weight, 108 and 96g digestible crude protein per kg dry matter and 617 and 619 g digestible organic matter per kg dry matter. In addition, four concentrate supplements were offered, containing either 360 g crude protein per kg on an air-dry basis and given at the rate of 015 kg/kg milk or 180 g crude protein per kg given at the rate of 030, 0375 and 0·45 kg/kg milk. Large and highly significant differences were recorded in silage intake, mil yield, milk composition, live weight and condition score during the winter feeding period. These differences in performance were associated more with differences in energy than in protein intake. During the post-experimental grazing period no significant differences between treatments were recorded in milk yield and composition, with the exception of fat concentration, and by midsummer no significant differences were apparent in live weight. The results of the experiment were appraised in economic terms and implications for commercial practice discussed.

In two experiments cows with access to self-feed grass silage were offered concentrates either twice daily in the milking parlour at a fixed level (controls) or in addition given free-access to a concentrate dispenser sited in the self-feed area (dispenser). A time-lapse mechanism on the dispenser limited successive 1 kg feeds to a minimum of 10 min in experiment 1 and 5 min in experiment 2. The 'dispenser' cows had significantly greater total concentrate intakes than had the controls (10-4 v. 71 kg/day in experiment 1, 13-4 v. 7-3 kg/day in experiment 2), but there was a large variation in intake between individuals. Access to the dispenser increased milk yields only slightly, reduced milk fat concentration and increased milk protein concentration and live-weight gain. Following turnout to grass in the spring, there was evidence that the cows that had been on the dispenser treatment showed a faster rate of decline in milk yield than did the controls, and this was supported by lower lactation yields in the dispenser group.