Effect of protein and energy supplements on milk production in organic farming

The effects of protein and energy supplementation on milk production responses were studied in three experiments. In experiment 1, eight cows were used in a duplicated <F>4×4</F> Latin square design to study the effects of a commercial conventionally produced rapeseed meal and organically cultivated field pea (Pisum sativum L.) as protein supplements for organic grass-red clover silage-based diets. Silage was fed ad libitum and concentrates at a rate of 8 kg per day. A mixture (1:1) of oats and barley was used as a control supplement (C). Rapeseed meal (R), a mixture of (1:1 on a CP basis) of rapeseed and field pea (RP) or field pea (P) were incorporated into three other supplements. Compared with C, R increased (<F>P<0.05</F>) silage intake by 0.64 kg per day and improved the daily yields of milk (1.7 kg), energy corrected milk (ECM) (1.6 kg), and milk protein (78 g), but decreased (<F>P<0.001</F>) the efficiency of dietary N utilisation from 0.295 to 0.264. Replacement of R with P linearly decreased (<F>P<0.05</F>) ECM yield from 24.5 to 23.3 kg per day and milk protein yield from 764 to 719 g per day. In experiment 2, the effects of energy (organically grown oats–barley, 1:1) and protein (commercial rapeseed meal) supplements on milk production in cows grazing organic grass swards was studied in a duplicated <F>4×4</F> Latin square design. Treatments consisted of herbage alone (H), 4 kg per day of energy supplement (E), 1.25 kg per day of protein supplement (P) and 2.75 kg per day of energy and 1.25 kg per day of protein supplements (EP). Both E and P supplementation improved (<F>P<0.01</F>) the daily yields of milk (2.3 and 1.4 kg, respectively) and milk constituents. Yields of milk and milk protein were highest when part of the E supplement was replaced with P. In experiment 3, the effects of supplement (g per day, oats (450), barley (450), rapeseed meal (100)) level (2.5 or 5 kg per day) and herbage allowance (HA, 18 or 24 kg DM per day) on milk production of cows at pasture was studied in a duplicated <F>4×4</F> Latin square. Higher levels of supplementation increased (<F>P<0.01</F>) milk yield and protein output by 1.7 kg and 64 g per day, respectively. In conclusion, the protein value of pea was markedly lower than that of rapeseed meal, while both the use of energy and protein supplements improved milk production at pasture. [Copyright &y& Elsevier]