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  • Can a calcium supplement derived from seaweed, affect the pH of gastric juice in horses?

    The horse’s stomach consists of an upper non-glandular (squamous) area and a lower glandular area. The glandular area secretes acidic gastric juices, essential to support digestion. The non-glandular area lacks suitable protection against these acidic gastric juices and exposure to them via ‘acid splashing’, plays an important role in the development of ulcers in this area. Maintaining a buffered environment in the stomach may support gastric health and this can be achieved by regular access to forage, avoiding fasting periods and the provision of calcium-containing feed ingredients such as alfalfa. The ability of a calcium-containing supplement derived from seaweed to buffer equine gastric juices was examined in a recent study1.

    Nine, clinically healthy, mature TB cross horses (3 mares, 6 geldings) were included in the study, which consisted of a randomised, cross-over design of three single-day experimental periods and three treatment groups, all fed 2 kg/day concentrate feed and 1.5% BW of hay per day. On the testing days (day 0, 7 and 14 of the study) treatment groups were fed an additional pelleted supplement of either control (CON), with no added seaweed supplement, MIN1, supplemented with a single concentration of the seaweed-derived supplement or MIN2, supplemented with twice the supplement concentration. Test pellets were either A, CON (95% wheat middlings, 5% molasses; 0.2% calcium, no added seaweed supplement) or B, MIN (84% wheat middlings, 11% seaweed supplement, 5% molasses; 3.5% calcium). On study days, horses were fasted for 16 hours and fed treatment pellets 2 hours before first sample collection via gastroscopy. CON group was fed 45.4g/100kg BW pellet A (no supplement added), MIN1 fed 22.7g/100kg BW pellet A, plus 22.7g/100kg BW pellet B, and MIN2 group was fed 45.4g/100kg BW pellet B. Gastroscopy was performed on study horses by a veterinary surgeon blinded to the treatment groups, three times during each treatment period – before supplement consumption, 2 hours after supplement consumption and then 2 hours after the second gastroscopy. Gastric juice (approx. 60 mL) was collected at each gastroscopy and pH was measured.

    No differences were observed in gastric juice pH between treatment groups before consumption of the supplements (0 hours), with an average pH of 2.31. Two hours after consumption there was a significant increase in pH across all treatment groups (P < 0.0001) and horses in the MIN1 and MIN2 groups had higher average gastric juice pH readings than CON (MIN1 = 5.92+0.58; MIN2 = 5.92+0.57; CON = 5.08+0.58; P = 0.0122). Four hours after consumption, there were no differences between treatment groups, but gastric juice pH was elevated (pH = 3.60 ± 0.48) compared to that observed at 0 hours (pH = 2.31 ± 0.58; P < 0.0001), likely due to consumption of treatment pellets and not specific supplementation.

    The study suggests that this seaweed-derived, calcium containing supplement was readily consumed by study horses and increased the pH of gastric juices for two hours after consumption. These results suggest that the supplement provided an additional short-term acid buffering effect on gastric juices above that of feeding alone and might have a potential supportive effect on equine gastric health. The clinical relevance of this additional buffering is unclear however as maintaining stomach pH above 4 is recommended for gastric ulcer healing.


    1. Jacobs RD, Gordon MBE, Vineyard KR, Keowen ML, Garza F Jr, Andrews FM. (2020). The Effect of a Seaweed-Derived Calcium Supplement on Gastric Juice pH in the Horse. J Equine Vet Sci. 95:103265.Available HERE

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