The objective of this study was to examine the effects of an Aspergillus oryzae extract in combination with a yeast culture (Saccharomyces cerevisiae) on milk yield and composition, rectal temperatures, and rumen parameters in a commercial dairy herd. Pluriparous Holstein cows (n = 521) in early lactation were assigned to a 130-d trial from May to September 1992. Treatments were control (no additive) and yeast culture (56 g/d) plus A. oryzae (3 g/d). Both groups were fed a TMR composed of alfalfa silage, alfalfa hay, corn silage, rolled barley, rolled corn, grass screenings, whole cottonseed, wet citrus pulp, molasses supplement, protein pellet, and minerals. No differences were detected in actual milk, 3.5% FCM, or percentages of milk fat or protein. Percentages of lactose and SNF were lower for the group fed yeast culture plus A. oryzae. Rectal temperatures were lower for cows fed yeast culture plus A. oryzae for 7 of 17 readings made during the summer. The greatest difference occurred during hotter months.

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Single cell protein (SCP) derived from secondary clarifiers of pulp mills is a potential commercial protein supplement in many areas. Samples of SCP were collected from several pulp mills in the Pacific Northwest and evaluated by laboratory procedures. Six in vivo digestion trials were conducted to determine the relative nutritive value of SCP that was dewatered by centrifugation or by the addition of a polyacrylamide polymer before being put through a belt press and dried with a sonic dehydrator. Amino acid analyses showed that SCP was higher in methionine than was cottonseed meal (CSM) and had a similar level of lysine. True protein, based upon amino acids recovered in SCP samples, ranged from 51.6 to 65.9% of the crude protein (CP). Pepsin digestibility of the CP ranged from 16.2 to 36.8%. Pepsin digestibility increased by 6.3 to 11.3 percentage units when SCP were incubated in a buffered rumen fluid for 24 hours. Solubility of the nitrogenous components in 10% Burroughs' buffer solution ranged from 12.4 to 36.5%. The range in mineral composition was : P, .62 to 1.55%; Ca, .14 to .99%; K, .21 to 5.52%; Mg, .07 to .59%. The concentration of trace minerals and heavy metals varied considerably from sample to sample. Digestion trials were conducted with sheep to compare SCP with CSM; 20 to 50% of the total CP was provided by the SCP sources. The CP digestibilities of the centrifuged and the polymer-dewatered SCP were 70.5 to 70.8% and 66.3 to 69.9%, respectively, of that observed for CSM. In all digestion trials, sheep consumed the SCP diets readily, and no digestive disturbances were observed. On the basis of laboratory and in vivo results, pulp mill SCP has the potential to be a viable protein supplement for livestock.

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