Irish cheese maker Glanbia said its first half results will be significantly behind those of the same period the previous year after dairy market volatility severely impacted its performance.While the consumer foods business is performing 'reasonably well' Glanbia said its food ingredients business was having a detrimental effect on the whole company's performance. The US food ingredients division is performing in line with expectations though results will be below those of the first half of 2008.The firm said it is implementing a rationalisation programme.Glanbia said it reiterates its earnings guidance of between €0.30 and €0.32 a share in 2009.