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Simple Summary: Forage contaminated with pathogenic microorganisms such as bacteria, moulds and yeasts with abiotic deposits represents a serious risk for the health of horses. Due to associated allergens, horses can develop allergic reactions, which may trigger respiratory diseases and would require drastic interventions in feeding regimens and housing conditions. Therefore, horse owners have started to treat hay with steam to achieve a reduction in inhalable allergens. However, the present study has shown that steaming led to the formation of Maillard reaction products, which decreased the proportions of precaecal digestible crude protein and precaecal digestible amino acids. As a consequence, these losses should be considered in ration calculation for horses that receive steam-treated hay. Steaming hay is increasingly used to treat low-quality forage because it was proven to reduce inhalable allergens such as mould spores, bacteria, and airborne dust particles. Preliminary results have shown a substantial loss of precaecal (pc) digestibility (D) of crude protein (CP) and amino acids (AA). For this purpose, six different batches of hay from central Germany were divided into four subsamples, and each one was individually steamed. Native hay and four replicates of each steamed subsample were analysed for CP, AA, neutral detergent insoluble crude protein (NDICP), neutral detergent soluble crude protein (NDSCP) as well as pepsin insoluble CP (piCP). Based on the analytical parameters, pcD of CP, protein solubility (PS), piCP (% CP) and precaecal digestible (pcd) CP and pcdAA contents were calculated. Selected Maillard reaction products (MRP), namely furosine and carboxymethyllysine (CML), were also analysed. Steaming did not affect CP content (native = 69, steamed = 67 g/kg dry matter, DM; p > 0.05), but it had an impact on the insoluble part of CP. Thus, NDICP increased by 57% (native = 27, steamed = 42 g/kg DM; p < 0.05) and piCP by 15% overall (native = 40, steamed = 46% of CP; p < 0.05). This could be a consequence of the heat damage and the associated increase in MRP. The content of furosine rose by 67% (native = 17.6, steamed = 29.4 mg/100 g DM; p < 0.05). The content of CML increased by 120% (native = 5.1, steamed = 11.3 mg/100 g DM; p < 0.05). We chose to analyse these two MRPs because they represent the reaction products with the limiting AA lysine. In contrast, the soluble fractions of CP declined, while PS as a percentage of CP decreased by 38% as a result of the treatment, and NDSCP was reduced by as much as 41% (p < 0.05). In line with this, the steaming process decreased the pcD of CP (native = 56%, steamed = 35%; p < 0.05) and pcdCP (native = 37.9, steamed = 22.5 g/kg DM; p < 0.05), respectively. The same effects were shown for selected AA; e.g., sulphuric AA pcd methionine plus pcd cysteine decreased by 45%, pcd threonine decreased by 41%, and the limited AA pcd lysine decreased by more than 50% (p < 0.05). In conclusion, the high temperatures generated during steaming lead to protein damage and consequently to a reduction in the pcD of CP and essential AA. Nevertheless, steaming successfully reduces viable microorganisms and binds dust particles. Therefore, steamed hay is still a proper and sometimes the only possible roughage for horses suffering from respiratory diseases such as equine asthma. Essentially, horse diets based on steamed hay should be balanced accordingly. [ABSTRACT FROM AUTHOR]

Abstract: The recent review of the German feeding standards for horses results in a change in recommendations for protein and energy. Part of the new approach was presented by Zeyner and Kienzle at a recent conference in the United Kingdom (Ellis et al. 2010, The impact of Nutrition on Health and performance of horses, European Association of Animal Production (EAPP) publication 128) and illustrated the proposed new system for feed evaluation with respect to prececally digested protein and metabolizable energy. This in turn is linked with an updated formulation of requirements. The major areas identified for change were the energy and nutrient requirements for mares as well as the energy requirements for exercise. A new growth curve for the fetus and the inclusion of fetal oxygen consumption form the basis of the new structure for the description of requirements during gestation. The allometric model for lactation is still unsatisfactory because of the wide variation in published data related to milk yield. Although the new recommended model is a compromise, it seems to be reasonably adjusted to the actual needs of the foal. The accurate determination of energy requirements for exercise is a problem in practice. Using the heart rate as a predictor of energy expenditure enables an estimate of the demand for energy to be made by means of a direct signal from an individually exercising live horse. However, the proposed method to allow for the integration of anaerobic energy metabolism still needs experimental confirmation. Finally, aspects of behavior are intensively discussed as a non-nutrient part of requirements. The recommendation to limit starch intake per meal and to have a minimum recommended intake of roughage should help support the health of the digestive system and reduce the risk of nutrition-associated behavioral problems. [Copyright &y& Elsevier]