The effect of reducing stocking rate and splitting the herd on spring dry matter intake on the Lincoln University Dairy Farm: A dissertation submitted in partial fulfilment of the requirements for the Degree of Bachelor of Agricultural Science With Honours at Lincoln University

Abstract

The pasture allowance and intake of cows on the Lincoln University Dairy Farm was measured from September to November 2011 and compared with automatically recorded milk production, live weight and body condition score data. The 638 cows on farm were milked in two separate herds, with cows assigned a herd based on parity and body condition score. The stocking rate was reduced from 4.18 to 3.98 cows.ha⁻¹ for the 2011 season with the objective of maintaining production, with a reduced environmental footprint. Production per hectare for the 2011 spring season was similar to that achieved in the previous season. The milk production per cow increased enough to offset the reduced production associated with the drop in stocking rate. This was most likely due to increased intake attributed to a number of management changes implemented for the 2011 season. The impact of the management decisions were unable to be quantified due to the large number of variables involved. The splitting of the herd into two, based on parity and BCS resulted in cows being grouped with cows of similar social standing. Even though both herds were treated similarly in terms of grazing management, splitting the herd most probably reduced the incidence of antisocial interaction and increased the grazing time and intake of cows. The mowing of pasture either pre- or post- grazing was used to reduce the cost of grazing and stimulate intake while meeting target residual. The result is a greater net energy benefit compared to 2010 when the mower was not used. The fact that milk production was maintained at the reduced stocking rate suggests that a split herd arrangement and the use of pre- and post- grazing mowing can improve the dry matter intake of grazing dairy cows.