August 14, 2019

Interpretive Summary: Sodium caseinate and fiber digestion in horses

Interpretive Summary: Effects of sodium caseinate on hindgut fermentation and fiber digestion in horses

By: Jackie Walling

Proper digestion of dietary fiber in horses is vital to gut health. An article published in the February 2019 Issue of the Journal of Animal Science evaluates the supplementation of sodium caseinate (casein) on hindgut fermentation and fiber digestion. Horses fed low-quality forage (low protein) face an increased likelihood of impaction colic and inadequate nutrient supply.  The concentration of nitrogen (N) reaching the hindgut is limited and reduces the efficiency of carbohydrate digestion in the cecum. By supplementing casein directly into the cecum, researchers hoped to improve digestion and utilization of a cool-season grass hay.

Eight mature Quarter Horses (4 mares, 4 geldings), cecally cannulated for a 56-day experiment consisting of 14-day treatment periods. Horses were divided into four treatments: CON (control, water); LOW (.125 g casein/kg BW); MED (.25 g casein/kg BW); HI (.5 g casein/kg BW).  Casein was solubilized in 800 mL of distilled water and dosed twice a day at 7 AM and 7 PM. Smooth Bromegrass hay (medium quality) was provided ad libitum at dosing times, and intake was recorded at 7 PM. Sample collection of cecal digesta began at 7 AM on day 12 and was collected every 6 hours until the end of day 14. Fecal output was also collected at this time.

Results showed treatment groups did not significantly differ in fecal pH, total volatile fatty acids (VFA), digestion of dry matter (DM), neutral detergent fiber (NDF), acid detergent fiber (ADF), or organic matter (OM). Six hours after each dosing time, cecal pH decreased while acetate, propionate, and butyrate levels elevated. Mean cecal pH was lowest in LOW and HI treatment groups. Ammonia concentration had a direct relationship with casein concentration. Levels were greatest at 7 AM and lowest at 1 AM correlating with previous studies.

Fecal pH did not reflect cecal parameters and was lower on average. The changes in VFA production and pH indicate feed reaches the cecum within six hours of being consumed. Minimal differences in the pH levels were attributed to the minimal changes in total VFA. No effect on digestibility of DM, NDF, ADF, and OM was attributed to the hay quality. The Bromegrass used was 8.5% crude protein, which could have provided enough ammonia for microbes and supplementation may not have been needed.

Overall, minimal effects were seen on fermentation and fiber degradation in horses supplemented directly with casein.  While quality of forage may have invalidated the effects of casein, researchers also note a small population size could have limited the results. To evaluate the use of casein further, different qualities of forage and larger sample size would be beneficial. 

To view the full article, visit the Journal of Animal Science.