Economic Analysis of Offering Different Herbage Allowances to Dairy Cows Fed a Partial Mixed Ration

SIMPLE SUMMARY: In south-eastern Australia, most dairy cows consume grazed pasture, cereal grain fed in the dairy and hay in the paddock. Previous research has shown that feeding supplements to grazing cows as a well-formulated mixed ration can increase feed intake, milk production and profit. This previous work was conducted under a limited herbage allowance to represent the conditions of drought or a high stocking rate. Two subsequent animal experiments were performed, one in early lactation and the other in late lactation, where the herbage allowance was varied from low to high and used to investigate the economics of partial mixed ration (PMR) feeding. We found that offering a medium allowance (25 and 20 kg DM/cow per day in early and late lactation, respectively) resulted in higher profit (total milk income minus feed costs) than a low herbage allowance (15 and 12 kg DM/cow per day in early and late lactation). No additional profit was obtained by further increasing the herbage allowance from medium to high (40 and 32 kg DM/cow per day in early and late lactation). These findings will assist farmers to manage their PMR systems in a profitable way. ABSTRACT: The economics of grazing dairy cows offered a range of herbage allowances and fed supplements as a partial mixed ration (PMR) were examined where profit was defined as the margin between total milk income and the cost of pasture plus PMR supplement. The analysis made use of milk production and feed intake data from two dairy cow nutrition experiments, one in early lactation and the other in late lactation. In early lactation and at a PMR intake of 6 kg DM/cow per day, the profit from the cows with access to a medium herbage allowance (25 kg DM/cow per day) was AUD 1.40/cow per day higher than that for cows on a low allowance (15 kg DM/cow per day). At a higher PMR intake of 14 kg DM/cow per day, the profit from the cows on a medium herbage allowance was AUD 0.45/cow per day higher than the cows on a low allowance; there was no additional profit from increasing the herbage allowance from medium to high (40 kg DM/cow per day). In late lactation, the profit from the cows fed a PMR with a medium herbage allowance (20 kg DM/cow per day) was only higher than the cows on a low allowance (12 kg DM/cow per day) when the PMR intake was between 6 and 12 kg DM/cow per day. There was also a difference of AUD +0.50/cow per day between the PMR with medium and high herbage allowance (32 kg DM/cow per day). It was concluded that farmers who feed a PMR to dairy cows should offer at least a medium herbage allowance to optimize profit. While feeding additional PMR increases milk production and profit, further gains would be available by offering a higher herbage allowance. These findings provide an estimate of the net benefits of different herbage allowances when feeding a PMR and will enable farmers to manage their feeding systems more profitably.