The aim of this study was to investigate the effect of grain supplementation on the faecal pH of horses maintained at pasture. Data were obtained from twelve mixed age horses kept at pasture, six controls 530 ±9.4 kg and six carbohydrate supplemented 513 ±10.2 kg. The supplemented horses were each feed up to 6.15kg of crushed oats in two feeds (am and pm) per day over a 38 day period. The supplementation was divided into seven treatment periods; a four day period with no grain (block 1), six days with the addition of grain to the diet at a rate of +0.5kg per day (block 2), six days with 3.4kg per day (block 3), four days with the addition of 0.5kg oats per day (block 4), six days fed 6.16kg per day (block 5), six days decreasing grain fed (block 6) followed by a five day observation period with no grain fed (block 7). Faecal material was collected daily for analysis immediately after defecation during the am feeding time. Throughout the supplementation trial there were no significant differences between the supplemented and control groups. There was a significant effect of period on faecal pH (P<0.05). There was no interaction of treatment and period. There was a trend for faecal pH to decrease during the trial. Block 7 was significantly different to all other blocks. Block 5 was significantly different to Block 1 (P<0.01). Within the model horse was a significant effect (P<0.05). There was a strong correlation between the control and treatment groups for faecal pH throughout the trial (r2=0.86). There was a trend for increased rainfall in the 2nd half of the supplementation trial which was associated with increasing soil temperature (P<0.01). The lack of significant change in faecal pH with increased grain supplementation indicates that for pasture kept horses factors such as pasture intake and greater activity may have a role in buffering the negative effects of a high grain diet.

CW, Rogers, B Eastwood, EK Gee, and EC Firth

Proceedings of the New Zealand Society of Animal Production, Volume 64, Hamilton, 165-170, 2004
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