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Effects of Substituting Various Levels of Feed-Grade Macadamia Nuts for Grain upon the Nutritive Value of Concentrate Rations for Sheep^{1, 2,}

Hawaii Agricultural Experiment Station³, Hilo

Abstract

Digestibility and growth trials were conducted to determine the effects of substituting various levels of feed-grade macadamia nuts containing 60.9% crude fat for grains upon the nutritive value of concentrate rations for sheep. The macadamia nuts were ground and mixed in the rations at levels of 0, 12, 24 and 36%, replacing equal parts of cracked corn and rolled barley by weight.

Average daily dry matter consumption and organic matter, nitrogen-free extract and energy digestibility were higher (P<.01) for the control ration when orthogonally compared with all rations containing macadamia nuts. However, the ration containing 12% macadamia nuts most nearly approached the control ration when these criteria were considered, and the greatest reductions occurred when the macadamia nut levels were increased to 24 or to 36%. Crude fiber and crude protein digestibility were not significantly affected by treatment. A quadratic response (P<.05) was obtained in nitrogen retention by increased retention with the ration containing 12% macadamia nuts and decreased retention as the nut levels were increased. Ether extract digestibility was lower (P<.01) for the control ration than for the rations containing macadamia nuts. Crude fat digestibility was lower (P<.05) than ether extract digestibility for all rations, and the differences in crude fat digestibility were not significant when the control ration was compared with the other treatments. These data add further evidence to the importance of correcting for fecal soap excretion when determining fat digestibility of ruminant rations containing high fat levels.

In a lamb growth trial average daily feed consumption and average daily gain were successively reduced with each increment of macadamia nuts in the ration. As was observed in the digestibility trial, the greatest reductions occurred with the higher nut levels. Feed conversion was also less efficient when the macadamia nuts were fed.

The combined results of both trials in this study indicate that low levels of feed-grade macadamia nuts can be used as feed grain replacements in ruminant rations.

¹ Approved by the Director of the Hawaii Agricultural Experiment Station as Technical Paper No. 776.

² The authors express appreciation to the Royal Hawaiian Macadamia Nut Co., Keaau, Hawaii, for supplying the feed-grade macadamia nuts used in this study.

³ Department of Animal Science.