The Effect Of Different Feeds On Oral Ph

The Study – What Was Tested?

The aim of the research carried out by Daniels et al., (2024), was to understand how different feedstuffs affect salivary pH in horses and ponies after feeding.

Study 1 was a 5x5 Latin Square design, where 5 mature horses were given 5 different feedstuffs in a random order, over 5 days. The feedstuffs used were meadow hay, ryegrass hay, unmolassed alfalfa chaff, unmolassed sugar beet pulp, and rolled oats. Each of these feedstuffs were already part of the horse’s daily rations, so no adaptation period was required. Salivary pH was measured pre-feeding, immediately post-feeding, and at 15- and 30-minutes post-feeding.

Study 2 was a replicated 4x4 Latin Square design with 8 randomly paired ponies given 4 different haylages over 4 feeding periods (15 days each). Two were mixed meadow haylages, two were ryegrass haylages. Saliva samples were taken before and after consuming 500g haylage on day 1, 6, and 12 of each period. Haylage comprised 100% of the diet during this study.

Key Findings: What Happens to Oral pH?

1. Sugarbeet Pulp Lowered pH Temporarily
   The only feed that temporarily lowered oral pH was sugarbeet pulp, which dropped the pH to about 4.45. However, this decrease wasn’t long-lasting; within 15 minutes, the pH returned to baseline.
2. Hay, Oats, and Alfalfa had No Effect on Oral pH, While Haylage Increased Oral pH After Feeding
   Contrasting industry perceptions, haylage and oats did not lower oral pH. In fact, though being slightly acidic, haylage actually increased oral pH after feeding, indicating a less acidic oral environment.
3. Haylage (Ryegrass vs. Meadow)
   Differences in oral pH between the two haylage types were not significant, and overall pH increased after feeding all haylage types. The haylage's nutritional content did not appear to predict the change in pH either.

Saliva's Buffering Power
One of the biggest takeaways is that saliva plays a major role in neutralizing changes in oral pH. The horse’s saliva contains bicarbonate, which buffers excess acidity. A key factor in the buffering of saliva is how much chewing is involved. Hay and haylage require a lot more chewing than sugarbeet pulp, which means more saliva is produced, helping to neutralize any acidity. In contrast, soaked sugarbeet pulp doesn't require much chewing, meaning less saliva is produced, which may be why it caused a temporary drop in pH.

What Does This Mean for Horse Owners?

This research suggests that while some feeds might have the potential to lower pH in the mouth, your horse’s saliva is very effective at neutralizing these changes, and drops in oral pH are quickly regulated. Providing constant access to forage is a great way to promote saliva production to buffer not only the oral environment, but also gastric pH. To reduce the risk of tooth decay, prioritise the hygienic quality of your forage to reduce consumption of bacteria that could promote caries. Steaming hay to remove bacteria could be a good preventative step. Further research is required to understand the long-term effects of these feedstuffs, ideally taking both salivary and gingival (gum) pH measures to see the full picture.

Daniels, S.P., Whiteside, E.J., Martin, S., Moore-Colyer, M.J.S. and Harris, P., 2024. Straight from the horse's mouth: The effect of different feedstuffs on oral pH in horses and ponies. Journal of Equine Veterinary Science, 142, p.105181.