EFFECT OF SULFUR SUPPLEMENTATION ON IN VITRO CELLULOSE DIGESTION AND ON NUTRIENT UTILIZATION AND NITROGEN METABOLISM OF LAMBS FED LOW QUALITY FESCUE HAY

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Abstract
Experiments were conducted to determine the effects of supplementing low quality tall fescue hay, containing 0.26% total sulfur, with an iso-sulfurous quantity of either sodium sulfate or D,L-methionine. In vitro experiments were carried out where rumen fluid was collected from sheep fed a similar low quality tall fescue hay. In experiment 1, the addition of 1% urea to the low quality fescue ration stimulated in vitro cellulose digestion (P <.001). The addition of 0.05%, 0.10% and 0.15% sulfur from either sodium sulfate or methionine also stimulated cellulose digestion (P <.001) with no difference due to sulfur source. In experiment 2, the addition of 0.8% nitrate-N added as potassium nitrate depressed in vitro fescue cellulose digestion (P <.001) regardless of whether the donor sheep were adapted or unadapted to nitrate in the ration. Addition of sulfur appeared to overcome the depression in cellulose digestion due to nitrate. In vivo experiments involved the use of 12 crossbred female lambs (average initial weight, 34 kg) which were randomly assigned to one of three treatments (fescue, no added sulfur; fescue plus 0.15% sulfur as sodium sulfate; and fescue plus 0.15% sulfuras D,L-methionine). After completion of trial 1, lambs were re-randomized and the trial was replicated. Acid detergent fiber (ADF) and neutral detergent fiber (NDF) digestibilities were improved (P <.01) by supplemental sulfur, regardless of sulfur source. Nitrogen retention was not significantly affected by treatment. Essential amino acids, expressed as a percent of the total amino acids, were higher (P <.01) for lambs receiving the 0.15% sulfate-S diet. Molar percentage of methionine was increased (P <.01) by the addition of sulfur to the control diet whereas phenylalanine and glutamine concentrations decreased with sulfur addition. Serum taken from lambs fed 0.15% methionine-S contained more histidine (P <.05) while lambs fed 0.15% sulfate-S had less (P <.05) serum glycine.