Original Research
The Effect of Steaming and Soaking on the Respirable Particle, Bacteria, Mould, and Nutrient Content in Hay for Horses

https://doi.org/10.1016/j.jevs.2015.09.006Get rights and content

Highlights

  • Steaming hay in a Haygain 600 reduces respirable particles by 99%.

  • Steaming hay in a Haygain 600 reduces bacteria and mould by 99%.

  • Partial steaming or soaking increases bacteria content of hay.

  • Steaming in a Haygain 1000 conserves protein and minerals in hay.

Abstract

Forage is crucial for stabled horses, promoting gut health, supplying valuable nutrients, and maintaining normal feeding behaviors. Forage can contain high levels of respirable dust predisposing horses to respiratory disorders. This study examined the effect of different treatments on the airborne respirable particles (ARPs), microbial and nutrient content of hay for horses in three experiments. Experiment 1a eight bales of meadow hay were subjected to five treatments n = 40: dry (D), 10-minute soak in water (W), steamed in a wheelie bin (TWB), steamed in a Haygain (HG) 600, and steamed with a kettle of boiling water (K) on ARP content. Experiment 1b microbial contamination was measured in five bales of meadow hay after treatments D, TWB, and HG in cold conditions (0–7°C) (n = 15). Experiment 2 measured the nutrient content of 30 different hays after D and HG treatments, n = 60. Data in experiments 1a and 1b were analyzed using analysis of variance and least significant difference test: hay and treatment as factors. Experiment 2 was analyzed using paired t-test with significance levels accepted P < .05. Results showed steaming in the HG reduced ARP and microbial contamination by 99%. TWB or K reduced ARP in hay by 88%. W, TWB, or K did not reduce microbial contamination. HG treatment preserved mineral and protein contents but reduced water-soluble carbohydrate by 18.3%. Steaming using an HG steamer is a feasible long-term strategy for reducing ARP and microbial contamination, while conserving mineral and protein content in hay and is thus suitable for providing hygienically clean forage to stabled horses.

Introduction

Grass hay is the most common fodder fed to stabled horses in the UK [1] and United States [2]. The nutrient content of both seed hay (monospecies) and meadow hay (multispecies) is mainly determined by the grass mixture and stage of growth at harvest, whereas the hygienic quality is more influenced by weather during the conservation process and storage conditions [3]. Feeding long forage to stabled horses can help maintain normal time budgets by satisfying the animal's innate need to chew [4]. Good hay or haylage can also supply a significant proportion of the daily nutrient requirements, although many owners find haylage too energy dense to be offered ad libitum and thus prefer to feed their horses a higher fiber lower energy forage such as grass hay.

Traditionally, farmers and horse owners assess hay visually and by smell; however, even well conserved hay can contain significant levels of respirable dust, and therefore, visual assessment is not a recommended method for selecting hygienic hay [5]. Respirable dust is composed of particles less than 5 μm in size and is referred by Hessel et al [6] as the thoracic fraction and by Art et al [7] and Clements and Pirie [8] as particles that are sufficiently small (0.5–5 μm) to penetrate the peripheral airways. Respirable dust contains potentially allergenic particles, such as mould and bacteria spores, mite feces, endotoxins, and beta glucans, all of which have the potential to contribute to the etiopathogenesis of equine environmental airway diseases including recurrent airway obstruction (RAO) in stabled horses [9], [10]. Although administration of corticosteroids and bronchodilators can alleviate the symptoms of RAO, these drugs contravene competition rules, and long-term use is expensive. Maintaining an RAO horse in an asymptomatic condition is best done by reducing the dust/animal interaction [11], [12], [13]. Woods et al [14] and Moore-Colyer and Auger [15] demonstrated that during feeding, dust in the breathing zone of the horse can be significantly higher than in the general stable environment thus minimizing dust released from feed is paramount. To reduce the dust released from hay fodder, many owners soak or steam their hay before feeding [16].

Soaking reduces the number of airborne respirable particles (ARPs) but has undesirable consequences as it leaches valuable minerals [17], [18] and water-soluble carbohydrates (WSCs) [19] from the hay, increases bacterial concentrations by 1.5-fold to fivefold [20], [21], and can produce postsoak liquor with a very high biological oxygen demand [22]. Poor forage hygiene derived from bacterial and mould proliferation has been associated with colic in horses [23]; thus, reducing the quality of forage by soaking is highly undesirable.

Steaming hay is rapidly becoming an acceptable alternative to soaking. Blackman and Moore-Colyer [18] reported that steaming hay for 80 minutes in 5-kg hay nets in a plastic dustbin fitted with a kettle element in the bottom, reduced ARP by 95% while conserving the mineral content of the hay. However, the impact of steaming in a dustbin on the bacterial and mould concentrations in the hay has not been established. Steaming using the specifically designed hay steamers such as the Haygain1000 (HG 1000) and HG 600 (Propress Equine Ltd, Hungerford, UK) has been shown to reduce ARP and microbiota in hay [20], [24], [25], but to date, there is no published information on the effect of high-temperature steaming on the nutrient content of hay.

The objective of the experiment 1a was to determine the effect of soaking and three different steaming techniques on the ARP numbers. In experiment 1b, the objective was to measure the effect of two different steaming techniques on the bacteria and mould content in hay, whereas experiment 2 determined the effect of high-temperature steaming on the nutrient content of hay for horses.

Section snippets

Experiment 1a

Eight square bales of field-dried UK meadow hay conserved in 2011 weighing approximately 25 kg were subjected to five different wetting treatments. Each bale was divided into five equal sections of approximately 5 kg and placed into small-holed (50 mm) hay nets. Before the steaming treatment took place, three wooden rulers containing nonreversible temperature strips (555-409, RoHS Scale B Self-adhesive, testo, www.testo.com) were pushed firmly into three different areas of the hay so that steam

Results

Hays used in all experiments were either meadow hay conserved from permanent pasture and contained a range of different grass species or seed hay which was all single species perennial rye grass (Lolium perenne). Hays were collected from across the UK and were thus a cross-section in terms of hygienic quality and nutrient content from the 2009 hay-making season.

Discussion

Across all the treatments examined, the results showed that steaming a range of hays in a high-temperature hay steamer conserved mineral and CP contents while being the most effective method for reducing ARP and viable microbial numbers.

Conclusions

The results of the present study show that when comparing dry, soaked, partially steamed, and high-temperature steaming, the most effective method for reducing ARPs, while conserving nutrients and improving the hygienic quality of hay fodder, is best achieved using the Haygain specifically designed high-temperature steamers. The present studies also show that partial steaming and soaking while effective at reducing ARPs in hay are contraindicated in terms of microbial contamination, and thus,

Acknowledgments

The authors thank Haygain Ltd for the use of the HG 1000 and HG 600 steamers for this work. There are no conflicts of interest for any of the authors.

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