Hay for Horses: the good, the bad and the ugly

Transcription

1 Why the concern about forages for horses? Hay for Horses: the good, the bad and the ugly Mary Beth Gordon, Ph.D. Purina Mills Minimum 1-1.5% body weight per day What is the most important factor influencing the quality of hay? a. Fertilization b. Climate conditions c. Age (time since cutting) d. Storage conditions e. Plant species f. None of the above What is the most important factor influencing the quality of hay? g. Maturity at time of harvest Factors that affect hay quality Maturity at time of harvest More mature plants -> more indigestible fiber Plant species (grass vs. legume) Fertilization Primarily affects yield at a given maturity Climate conditions Excessive moisture/drought affect lignin content Age Factors that affect hay quality Time since cutting Storage conditions Exposure to rain/sunlight Primarily affects vitamin content 1

2 Characteristics of good quality hay High leaf to stem ratio Small diameter stems Few seed heads or blooms Fresh smell and appearance Cleanliness Color Legumes Alfalfa Clover Lespedeza Grasses Types of Hays Bermudagrass Kentucky bluegrass Orchardgrass Timothy Prairiegrass Cereal grasses Bromegrass Fescue Alfalfa Legumes High protein, high calcium, more energy than most grasses High quality alfalfa can have low fiber Stage of maturity when harvested greatly affects nutrient content Potential blister beetle toxicity Clovers Legumes Intermediate protein, about the same energy as many grasses May contain mold that causes slobbering Lespedeza Less protein and energy than alfalfa, similar to alfalfa in Ca and P The wonders of alfalfa Grass hays Vary greatly in nutritive value and palatability Generally provide less protein and energy than good quality alfalfa Good quality grass hays may be more digestible than medium to poor quality alfalfa May safely be fed free choice to most horses 2

3 Fescue toxicity Endophyte-infected fescue can cause serious reproductive problems in broodmares Prolonged gestation Abortion Thickened placenta Agalactia (no milk) No fescue hay or grazing last 90 days of gestation or during lactation Horses gaining weight on hay Glycemic response to hay Testing Hay What is Important? Crude fiber NDF (Neutral Detergent Fiber) and ADF (Acid Detergent Fiber) Soluble Carbohydrates Crude Protein Minerals and Vitamins RFV (Relative Feed Value) A calculated value, estimates digestibility and nutritive value of the hay NDF and ADF Crude Fiber Is variable (poor repeatability in testing) Is of low value to non-ruminant 3

4 NSC Nonfiber CHO Sugars Starches NDSF Total CHO Hemicellulose Pectins Fructans β-glucans Neutral Detergent Fiber (NDF) ADF Cellulose Lignin Maillard protein Things to keep in mind As ADF and NDF increase, digestibility decreases as does voluntary intake Increasing maturity at time of cutting will increase ADF At exceptionally low ADF (mid 20 s) hay may not contain enough fiber for healthy hindgut Soluble Carbohydrates Testing for soluble carbs is still not well defined Different labs different procedures Variability even within the same lab, same feed samples NSC Nonfiber CHO Sugars Starches NDSF Total CHO Hemicellulose Pectins Fructans β-glucans Neutral Detergent Fiber (NDF) ADF Cellulose Lignin Maillard protein Crude Protein NDF ADF Starch WSC ESC ESC + Starch NSC (WSC+Starch( WSC+Starch) Calcium Phosphorus Ca:P Zinc Copper RFV Brome Brome Brome Soaking Hay Soaking hay (30 min hot H 2 O; 60 min cold H 2 O) will remove some WSC Will also remove other nutrients (some minerals, protein) 4

5 New research about soaking hay Crude Protein Tells nothing about protein quality Tells nothing about site of digestion Protein Review Horses do not have a protein requirement; they have an amino acid requirement Protein digestion in the upper gut yields amino acids Protein digestion in the hindgut yields nitrogen and a carbon skeleton - no amino acids Hays vary greatly in upper tract digestibility The amount of protein digested in the upper gut is influenced by the amount of fiber in the hay The relative role of the small intestine in the digestion of protein is limited even with top quality forage In one study, true digestibility of N in high quality alfalfa in the upper tract was only 37%, although apparent total tract digestibility was 74% Protein Content in Alfalfa July - June observations ADF Content in Alfalfa July - June Observations Observations Protein, % Observations Acid Detergent Fiber, %

6 2nd Cut Alfalfa Alfalfa Hay Analysis CP% ADF% NDF% Ca% 1.76 P%.30 K% 2.85 Lignin% 9.11 RFV Washington Alfalfa CP% ADF% NDF% Ca% 1.35 P%.22 K% 1.82 Lignin% 6.21 RFV Prececal N Absorption With Different Hays Coastal Low Alfalfa High Alfalfa Protein, % N intake, g/fd Prececal N dis, g Postileal N dis, g Prececal, % Postileal, % Gibbs, et al., 1988 Summary The primary factor influencing the quality of hay is maturity at time of harvest. It is easy to overestimate the contribution of amino acids to the total diet from hay. Crude protein content of hays is of little use in determining if amino acid requirements are being met. The contribution of amino acids from hay is highly variable and largely determined by the site of digestion. Vitamins Expensive to assay Fairly unstable Aged hay is poor source of several vitamins Minerals Usually stable over time Some are expensive to assay (Se) Hays (forages) tend to be deficient in some minerals Zinc, Copper, Phosphorus Crude Protein NDF ADF NFC Starch WSC ESC ESC + Starch NSC (WSC+Starch) Calcium Phosphorus Zinc Copper RFV Tim Forage hay Alfalfa Alfalfa Tim/ Orch BG BG Orch

7 Relative Feed Value (RFV) Index for ranking forages based on digestibility and intake potential Calculated from ADF, NDF, CP, etc. Estimates digestibility and nutritive value The higher the RFV, the better the quality Hay Market Task Force of the American Forage and Grasslands Council ( Relative Feed Value Quality Standard Prime 1 (Excellent 2 ) (Good) 3 (Fair) 4 (Poor) 5 (Reject) % ADF < >46 % NDF < >66 DMI % of BW > <1.8 RFV > <74 Hay Market Task Force American Forage and Grasslands Council ( Recommendations Judging Hay Horses with high energy/nutrient requirements (lactating mares, growing horses, working horses) Utilize high quality hays (RFV good - excellent) Horses with low energy requirements Utilize medium quality hays (RFV fair - good) Carb intolerant horses Utilize medium quality hays; warm season grasses Analytical Resources Feeding Round Bales Dairy One 730 Warren Road Ithaca, New York (800) Equi-analytical Laboratories 730 Warren Road Ithaca, New York (877)

8 Feeding Round Bales Not the optimal way to feed hay to horses (more risky), but possibly the best option in some situations Hay should still be of high quality for horses Management is essential Higher potential for mold Horses tend to avoid moldy hay if good hay is available Set out new bale before existing bale is down to moldy hay Round bale feeders specifically for horses will help minimize waste Recommendations It is difficult to maintain nutritional consistency in hay When the roughage source is critical, a complete feed (Equine Junior, Equine Adult, Equine Senior, Horse Chow) may be a better choice to maintain consistent nutrient balance Recommendations Keep in mind: Hays that are low NSC may have low RFV; therefore low digestibility of essential nutrients Horses that maintain weight on hay alone still need adequate amino acids, vitamins and minerals to meet their nutritional demands Nature s s Essentials Enrich 32 or Enrich 12 Questions? 8