| Summary: | A preliminary in vitro digestion study was conducted to investigate the effect of roughage level in the diet of steers producing fecal waste, drying method and NaOH treatment, on in vitro dry matter digestibility of cattle fecal waste. All three factors significantly (P<.01) affected in vitro dry matter digestibility of cattle fecal wastes.
In vivo digestion trials were conducted to study the apparent digestibility of untreated and NaOH treated fecal waste from steers fed rations containing different roughage levels. In each of two trials, three yearling steers were fed a 50% roughage ration and three were fed a 10% roughage ration. High- and low-roughage rations contained 13.4 and 13.6% crude protein, dry basis. Apparent digestibility of dry matter was 67% for the steers fed the high-roughage and 78% for those fed the low-roughage ration. One-half of the feces from steers fed each ration was treated by adding 3% NaOH (w/w), wet basis. All feces were then dried at 120 C for 24 hours. Dried, untreated high-roughage (UHR) fecal waste, treated high-roughage (THR) fecal waste, untreated low-roughage (ULR) fecal waste, and treated low-roughage (TLR) fecal waste contained 18.0, 14.9, 20.7 and 17.0% crude protein and 20.5, 17.8, 15.7 and 12.4% crude fiber, dry basis, respectively. A digestion trial was conducted with 30 wether lambs fed the following rations: (1) 100% basal, (2) 75% basal and 25% UHR fecal waste, (3) 75% basal and 25% THR fecal waste, (4) 75% basal and 25% ULR fecal waste, and (5) 75% basal and 25% TLR fecal waste. The basal contained 30% roughage and analyzed 11.7% crude protein, dry basis. Apparent digestibility of proximate and Van Soest components in the basal ration was generally decreased by substitution of all kinds of fecal waste, with the exception of fiber components in the ration containing NaOH treated low-roughage waste. TDN and metabolizable energy content of all the rations containing dried cattle fecal waste were lower (P<.01) than for the basal ration.
Apparent digestion coefficients for cattle fecal wastes, calculated by difference, were: 24.3, 52.9, 52.9 and 67.0 for dry matter; 32.1, 20.8, 49.1 and 29.1 for crude protein; and 3.2, 43.0, 32.6 and 60.1 for crude fiber in UHR, THR, ULR and TLR waste, respectively. In general, apparent digestion coefficients for ULR waste were much higher than those for UHR waste. Untreated high-roughage waste appears to be of limited protein and energy value for refeeding to ruminants. However, untreated low-roughage waste appears to have considerable refeeding value, being comparable to good quality orchardgrass hay with respect to digestible protein and energy content. NaOH treatment of high- and low-roughage cattle fecal wastes resulted in a significant increase in apparent digestibility of most components studied. The increases in apparent digestibility of fiber components of the NaOH treated wastes were sizable, especially for the high-roughage waste. Addition of the high level of NaOH used in this study may not be economically feasible. However, addition of lower levels, as have been used in treatment of other low quality roughages, may result in sufficient improvement in nutritive value to be economically feasible. === Doctor of Philosophy
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