Feeding calcium salts of fatty acids in high-starch or high-fibre compound supplements to lactating cows at grass

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Abstract
In two experiments, the effects of protected fat and fibre were studied in compound supplements for grazing dairy cows. The protected fat used consisted of calcium salts of long-chain fatty acids. In experiment 1, 17 cows (group S) were given 4 kg/day of a starchy compound and 17 (group F) 4 kg/day of a high-fibre compound containing protected fat for the first 4 weeks after turn-out to grass. No significant difference was found between groups in milk yield, but cows in group F produced milk with a higher fat content (42·6 g/kg) than did those in group S (37·1 g/kg; P < 0·01) and had higher yields of fat (0·88 v. 0·79 kg/day; (P < 0·05). In experiment 2, four groups of five cows were given 4 kg/day of starchy (S) or fibrous (F) compounds, with (P) or without (C) protected fat for the first 4 weeks after turn-out. After 4 weeks, treatments (starchy or fibrous, added fat or none) were reversed for a further period of 4 weeks. There was no significant effect on milk yield, milk protein yield, live-weight change or change in condition score, although cows on treatment SC tended to produce less milk and have greater gains in live weight and condition. For groups SC, FC, SP and FP respectively, milk fat yields (kg/day) were 0·86, 0·98, 0·99 and 1·06 (s.e.d. 0·06); milk protein contents (g/kg) were 34·4, 34·8, 34·2 and 33·0 (s.e.d. 0·68) and calculated milk energy outputs (MJ/day) were 67/2, 74·3, 74·4 and 76·6 (s.e.d. 3·04). It is concluded that substituting fibrous compounds for starchy compounds tends to increase milk fat content and yield; adding calcium salts of fatty acids to either type of compound significantly increases milk fat content and yield but tends to decrease milk protein content.