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1346 Effect of narasin on rumen metabolism and dry matter intake in wethers fed high-forage diets
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2016
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NutritionAgricultural EconomicsHigh-forage DietsFeed UtilizationDry Matter IntakeOrthogonal PolynomialsFeed AdditiveAnimal FeedPublic HealthHealth SciencesIn Vitro FermentationAnimal NutritionFeed EvaluationRumen MetabolismPharmacologyFood PreservativesProtozoa ConcentrationAnimal SciencePhysiologyFeed IntakeNutritional SciencesMetabolism
The objectives in this trial were to determine the effects of increasing levels of narasin on short chain fatty acid profile, pH and rumen protozoa concentration in whethers fed high-forage diets. Five White Dorper × Santa Inês wethers (BW 68.7 ± 2.1 kg), cannulated in the rumen, were used in 5 × 5 Latin Square design. Animals were fed daily and diet was composed of coastcross hay (91.0% DM; 67.2% NDF; 32.1% ADF; 6.8 CP; 5.5% ash). Narasin was offered twice a day and levels were 0 (control), 8, 16, 24 or 32 mg/kg DM, corresponding to 0, 80, 160, 240, and 320 mg of Zimprova 100®. The delivery vehicle of narasin was 20 g of ground corn containing the set dosage of narasin in 1 kg of DM. Every experimental period lasted 20 d and rumen fluid was collected in the last day, every 3 h, starting prior feeding, 3, 6, 9, and 12 h after feeding. Dry matter intake (DMI) was measured on d 20. Short-chain fatty acids (SCFA) and pH were analyzed as repeated measures over time. Protozoa concentration was analyzed at 3 h after feeding. Data were analyzed using MIXED procedure (SAS Inst. Inc.) and the LSMEANS option was used to generate individual means. Orthogonal polynomials for diet responses were determined by linear and quadratic effect. The effects were considered significant when P < 0.10. Increasing levels of narasin did not affect DMI (1.00 ± 0.12 kg/d; P = 0.45). There was an increased linear response for total SCFA (77.24, 81.30, 90.04, 83.65, 89.60 mM/L, P = 0.02). Acetate (78.40 ± 0.64 mM/100Mm, P = 0.93), propionate (15.03 ± 0.41 mM/100mM, P = 0.79), isobutyrate (0.62 ± 0.11 mM/100mM, P = 0.97), butyrate (4.34 ± 0.24 mM/100mM, P = 0.62), isovalerate (0.97 ± 0.19 mM/100mM, P = 0.95), valerate (0.64 ± 0.07 mM/100mM, P = 0.30) acetate-propionate ratio (5.28 ± 0.28, P = 0.76), pH (6.64 ± 0.13, P = 0.46) and rumen protozoa concentration (2.44 ± 0.22 × 105/ml, P = 0.69) were unaffected by the experimental diets. Increasing doses of narasin resulted in higher concentration of total SCFA.