Original Research
The Effect of Soaking on Carbohydrate Removal and Dry Matter Loss in Orchardgrass and Alfalfa Hays

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Abstract

The objective of this research was to determine the impact of water temperature and soaking length on removal of nonstructural carbohydrate (NSC) fractions and dry matter (DM) from legume and cool-season grass hays. The experimental design was a randomized complete block with six replications. Hay types included bud and flowering alfalfa (Medicago sativa L.) and vegetative and flowering orchardgrass (Dactylis glomerata L.). Flakes were submerged for 15, 30, and 60 minutes in 25 L of cold (22°C) water, warm (39°C) water, and 12 hours in cold water, respectively. Water temperature at each soaking duration did not affect residual NSC fractions in alfalfa hays. Flowering and vegetative orchardgrass hays soaked for 30 and 60 minutes, respectively, in warm water had greater (P < .001) amounts of NSC fraction removal compared with soaking in cold water. Soaking bud and flowering alfalfa and vegetative orchardgrass hays for ≥15 minutes removed more NSC fractions compared with the control (P ≤ .005); however, soaking for 15-60 minutes resulted in similar NSC fraction removal. Conversely, in flowering orchardgrass hay, longer soaking times resulted in greater (P < .001) NSC fraction removal. Fructan removal in orchardgrass hay was greatest (P < .001) after soaking for 12 hours. DM losses were similar among hays after soaking for 15-60 minutes, but were greatest after soaking for 12 hours (P < .001). Soaking grass hay for 15-30 minutes is recommended to remove sufficient NSC fractions while minimizing DM losses.

Introduction

Laminitis is a debilitating and costly disease affecting equines [1]. Pasture-induced laminitis typically occurs during periods of increased or rapid intake of nonstructural carbohydrates (NSCs) [2], [3], and horses (Equus caballus) appear to be especially sensitive to small changes in dietary carbohydrate intake [4]. Fructan is considered to be a significant component of the NSC fraction, accounting for as much as 57% [5], and several researchers [6], [7], [8] have found that administrating a concentrated fructan bolus to clinically normal horses resulted in laminitis. NSC content has been shown to affect other diseased horses. Muscle pain in horses diagnosed with polysaccharide storage myopathy (PSSM) was exacerbated by feeding diets high in NSC [9], and Borgia et al. [10] recommended that only hay containing ≤10% NSC should be fed to horses affected by PSSM.

Although limiting pasture intake or feeding hay low in NSC should be the primary management tool for feeding horses with PSSM and laminitis, low NSC hay is not always readily available. Thus, horse owners have resorted to soaking hay in water to remove NSC to manage horses diagnosed with laminitis or PSSM. The current recommendation for carbohydrate removal is soaking hay for 30 minutes in warm water or for 60 minutes in cold water [11]. Previous research has confirmed removal of water-soluble carbohydrates (WSCs) from hay soaked in water [5], [12], [13], [14], but these results have limited applications because they are based on soaking of chopped hay [13], small amounts of hay (50-250 g) [11], [12], [14], or hays specific to a geographic region outside of the United States [5]. Although dry matter (DM) losses were not reported in previous hay soaking trials, in-field DM losses in cut hays have been observed after rainfall events. Collins [15] observed that alfalfa hay lost 13%-15% and 43%-44% of its DM after 2.5 and 4.1 cm of rainfall, respectively, and orchardgrass hay DM losses ranged from 5% to 9% after 2.5 to 7.6 cm of simulated rainfall, respectively [16].

The loss of carbohydrates has not been extensively evaluated in hays commonly fed to horses in the Midwest region of the United States, and DM losses and its effect on NSC fractions after soaking have yet to be explored. Our hypothesis was that legume and cool-season grass hays would lose increasing amounts of NSC fractions and DM as soaking length increased. The objective of this research was to determine the impact of water temperature and soaking length on removal of NSC fractions and DM from different harvests of legume and cool-season grass hays.

Section snippets

Material and Methods

The experimental design was a randomized complete block with six replications. Six bales of each hay type were used. Four different hay types, commonly fed to horses in the Midwestern area of the United States, were soaked during July 2009 in St. Paul, MN. Hay types included a second cutting early bud and first cutting flowering alfalfa (Medicago sativa L.), and a second cutting vegetative and first cutting flowering orchardgrass (Dactylis glomerata L.). To mirror hay purchases made by most

Forage Quality

The alfalfa and orchardgrass hays were typical of legume and grass hays (Table 1). Crude protein and calcium (Ca) levels were greater and NDF levels lower in alfalfa compared with orchardgrass. Sleugh et al. [24] observed similar differences between grass and legume hays. Orchardgrass hay had greater levels of NSC fractions compared with alfalfa, similar to previous studies [25]. More mature hays (flowering alfalfa and orchardgrass) had higher NDF levels and lower CP and DE concentration

Conclusions

Water temperature had little effect on carbohydrate removal in alfalfa and vegetative orchardgrass hays. However, warm water did result in greater NSC fraction removal in flowering orchardgrass hay, but only when the hay was soaked for 30 minutes. NSC fraction removal after soaking alfalfa and vegetative orchardgrass hays for 15 minutes was equivalent to soaking for 30 minutes in warm water or 60 minutes in cold water, the current recommendation for carbohydrate removal when feeding diseased

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