Effect of Physical Form of Different Parts of Lamb Fattening Rations on Feedlot Performance and Digestibility

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Abstract
During a 3-year period feeding and digestion trials were conducted to study the effect of physical form of the hay, the concentrate and complete lamb fattening ration on feedlot performance, incidence of rumen parakeratosis and digestibility of ration components. The physical forms used were long, finely ground and pelleted hay; finely ground and pelleted concentrates; and finely ground, pelleted, and pelleted and reground complete ration. In the first experiment fine grinding the hay significantly increased rate of gain, which was not increased further by pelleting. In the second experiment fine grinding the hay did not significantly affect rate of gain, but pelleting the hay significantly increased gain. In experiment 1 feed efficiency was increased 14% when long hay was ground and was further increased 5% when the hay was pelleted. In experiment 2 feed efficiency was not substantially affected when hay was ground, but was increased 8% when hay was pelleted. When pelleted hay was fed a significant depression in crude fiber digestibility resulted, compared with long hay. In experiment 2 feeding finely-ground hay had a similar effect. Pelleting the concentrate portion consistently resulted in a depression in feed intake, with no effect on rate of gain, and consequently resulted in an improvement in feed efficiency. In experiment 1 pelleting the complete ration did not alter feedlot performance. In experiment 2 pelleting the finely-ground ration resulted in a significant increase in rate of gain and a 16% increase in feed efficiency. In this experiment performance of lambs fed reground pellets was intermediate between the performance of the lambs fed ground feed and those fed pelleted feed. Pelleting the entire ration consistently lowered crude fiber digestibility; the original value was approximately restored when the pellets were reground. Pelleted feeds resulted in an increased (P<.01) in incidence of rumen parakeratosis only in the first of three feeding trials.