CHAPTER XXVI. ; 



THE LACTIC ACID BACTERIA IN THE PREPARATION 

 OF FODDER. 



5 154. Brown Hay. 



ONE of the processes wherein micro-organisms play an active part 

 for the preservation of juicy fodder, viz., that dealing with burnt 

 hay, has already been noticed in 106; and we will now briefly 

 sketch a second and more general practice, viz., the preparation of 

 brown hay. As in the former case, the warmth necessary for 

 driving off the water in the fodder has to be supplied by thermo- 

 genic bacteria. In addition to these, however, another series of 

 organisms, converting part of the carbohydrates into lactic acid, 

 butyric acid, &c., comes into play. The percentage of water in 

 the green fodder employed for making brown hay must be smaller 

 than in that worked up into burnt hay. The materials (grass, &c.) 

 are built up into a round or square rick from 16 to 24 feet in 

 diameter, and 13 to 16 feet high, well trodden down, and thatched 

 in the roof to prevent the incursion of rain-water. At the end of 

 about three days, spontaneous heating (" sweating ") will become 

 manifest, and its progress can be conveniently followed by means of 

 a metal pipe laid in the stack and containing a thermometer (pro- 

 vided with a couple of attached strings), which can be drawn out as 

 required, for the purpose of reading off the temperature prevailing 

 in the interior of the heap. In proportion as the temperature rises 

 .(generally up to 70 C., and frequently still higher), the mass begins 

 to steam, and this goes on for eight to fourteen days, a further 

 four to eight weeks being allowed to pass before the brown hay 

 can be considered as finished. The product forms a firm, dry 

 mass, the colour of which, under normal conditions, is between 

 pale and dark brown, but is black when overheating has occurred. 

 In point of cohesion this brown hay is preferable to air-dried hay, 

 l)eing less brittle than the latter, but tough and suitable for fodder. 

 Its odour is aromatic, and recalls that of freshly-baked bread or 

 honeycomb. Comparative investigations into the chemical changes 

 produced in this method of preparation have been made by Dietrich, 

 Moser, Weiske, and others. The results obtained by Dietrich are 

 given below, since they afford material for judging the process 

 from the Fermentation Physiologist's point of view. A parcel of 

 .aftermath was divided into two portions, the one being worked up 



259. 



