Blood and fecal metabolic responses of mature horses fed rhizoma peanut hay.

Overview

• This study compared the effects of feeding rhizoma peanut (RP) hay versus alfalfa (ALF) and bermudagrass (BMG) hays on metabolic parameters in mature horses.
• Researchers measured changes in fecal and blood metabolites to assess how each forage impacted horse metabolism.

Introduction and Objectives

• Rhizoma peanut (Arachis glabrata Benth) is an alternative legume forage to alfalfa but contains lower amounts of non-structural carbohydrates and crude protein.
• Alfalfa is a commonly used legume forage known for its high-quality nutrition but may cause increased metabolic responses such as blood glucose and insulin spikes.
• The metabolic effects of RP hay in horses had not been evaluated prior to this study.
• The main objective was to investigate how feeding rhizoma peanut hay affects fecal and blood metabolic parameters in horses, in comparison to alfalfa and bermudagrass hays.

Methods

• Six mature Quarter Horse geldings, averaging about 596 kg, were used for the study.
• They were fed one of three hays: RP ‘Florigraze’, ALF ‘Legendary XHD’, or BMG ‘Coastal’.
• Study design: randomized replicated 3×3 Latin square with 21-day feeding periods per treatment.
• Fecal and blood samples were collected on day 19 at four time points: immediately before feeding (0 h), and at 2, 4, and 8 hours post-feeding.
• These samples allowed measurement of fecal dry matter, pH, ammonia-nitrogen, short-chain fatty acids (SCFA), and blood glucose, insulin, and plasma urea nitrogen (PUN).

Results – Fecal Metabolic Variables

• There was no significant difference in fecal dry matter content or fecal pH among the three hay types.
• Fecal ammonia-nitrogen levels were highest in horses fed alfalfa (significant at P=0.01), indicating greater nitrogen excretion or protein breakdown.
• Rhizoma peanut and bermudagrass had similar and lower fecal ammonia-nitrogen levels compared to alfalfa.
• Fecal short-chain fatty acids, which reflect microbial fermentation in the hindgut, tended to be highest in alfalfa-fed horses (P=0.07), with RP and BMG being lower.

Results – Blood Metabolic Variables

• Serum glucose concentration changed over time following feeding across all hay treatments; it peaked at 4 hours post-feeding (P=0.01).
• Alfalfa induced significantly higher blood glucose and insulin responses (P=0.01 for both) compared to bermudagrass, demonstrating a stronger glycemic and insulinemic effect.
• Rhizoma peanut’s glucose and insulin responses did not differ significantly from either alfalfa or bermudagrass, suggesting a moderate metabolic effect.
• Plasma urea nitrogen (PUN), a marker of protein metabolism and nitrogen balance, was lower in horses fed RP compared to those fed ALF (P=0.05), but similar to BMG.
• PUN levels decreased significantly 8 hours after feeding (P<0.01), indicating normal postprandial metabolic processing.

Conclusions

• Feeding rhizoma peanut hay produces more favorable metabolic responses than alfalfa, especially concerning protein metabolism and nitrogen excretion.
• Although RP is a legume forage, it leads to lower fecal ammonia and plasma urea nitrogen than alfalfa, which may be beneficial for long-term health and nutrient utilization.
• RP provides a high-quality nutritional alternative to alfalfa without causing excessive blood glucose and insulin spikes.
• This suggests RP hay could be a suitable forage choice for maintenance horses aiming for balanced nutrition and metabolic stability.