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February, 1942

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Modern warfare is largely a question of supplies. This obtains not only for direct munitions of war but also for the whole gamut of our civilian and industrial reserves. Total war demands the application of all our energies and resources to the national effort, and anything we do, either individually or as an industry, to conserve our supplies is both elementary wisdom and a service to the country.

All of us acknowledge this principle in our acceptance of food rationing, and a similar control has to be exercised in the feeding of the country's livestock. Those collieries employing pit ponies — and in spite of the phenomenal increase in underground mechanisation there are still some 32,000 pit ponies in service — are faced with this problem in the reduced reserves of hay and oats now available for colliery use, and it is important that such collieries should investigate the possibilities of substitute feeding stuffs.

The true position is not yet realised at many collieries which are likely to be vitally affected; it is so easy for some local condition to mask the general situation and for individual judgment to be correspondingly vitiated. Normally no horsekeeper would feed his stock with hay under 3-5 months old, for reasons that will be obvious to him; but this actually happened last summer at quite a number of collieries. Certain collieries ran entirely out of stock, and had to feed newly cut grass during the latter weeks of the season, and there were cases where hay was sent down the pit straight from the pike. We have been allowed to examine figures demonstrating that in the Northern Division — where over one-third of our pit ponies are employed — the hay stocks available to the collieries last summer actually fell short of requirements. This implies that the 25 per cent. carry-over of stock necessary to ensure feeding three-month-old hay has been consumed, and is not available for the present season. Even in normal times it is not possible to estimate with any accuracy the stocks of hay available to industry, because the farmer naturally satisfies his own requirements first, and it is only the surplus hay that comes on to the market. This year that surplus may very well be less than usual because artificial foods will be so much scarcer, and the farmer is likely to use more hay for his cattle. This does not take into account the reduction due to the ploughing up of grassland, although some alleviation is to be found in the fewer cattle now on the hoof.

Collieries maintaining pit ponies will therefore consult both the national cause and their own interests by taking the question of substitute feeding stuffs seriously. Our reserve must be supplemented in every way possible, and it is obvious commonsense to accustom our livestock now to a mixed diet which is likely to remain uniform throughout the season rather than to be forced to change them abruptly to an ill-balanced diet towards the close of the season owing to a shortage of normal supplies. A substitute food that is being satisfactorily fed to ponies at certain pits in the Northumberland and Durham coalfield is straw pulp. Straw pulp is coming into increasing use on farms, and it is the purpose of this article to discuss its feeding value, how it is prepared, and the experiences of some of the collieries at which it has been tried.

Straw pulp

Wheat straw in its natural state is not a suitable animal food. This is not because its food value as revealed by analysis is low, but because it is indigestible. Straw fibres are covered with a woody skin which prevents the gastric juices from acting upon the nutritive substances in the straw. This woody skin, however, can be broken down by pickling chopped straw in a solution of caustic soda, and after the soda has been removed by washing, the straw becomes a pulp the solid content of which has a starch equivalent roughly equal to dry hay. Untreated wheat straw has a starch equivalent of 15 per cent. After the treatment just described it yields 3½ times its weight of pulp, having a starch equivalent of 9 per cent., or a total yield of 31½ per cent, starch equivalent on the original straw. This corresponds to an increase in actual food value of 110 per cent. The corresponding increases for other straws are as follows: Barley straw, 57 per cent.; good oat straw, 37 per cent.; very best oat straw, chaff, and cavings, 26 per cent. The pulps from all these straws are of roughly the same food value, the differences in the percentage increases just quoted being due to differences in the food values of the original straws. The 3½ tons of pulp produced from 1 ton of straw supplies the same weight of starch as 7¾ cwt. of maize, 8¾ cwt. of barley or rice meal. 10½ cwt. of crushed oats or best dried pulp, or 20½ cwt. of hay. The increase in weight during pulping is due to the absorption of water, and although this renders straw pulp a bulky food, the ponies compensate for this by drinking less.

It is not, of course, suggested that ponies should be expected to exist on straw pulp, but that it should be used to replace a portion of the oat or hay ration and thus assist to conserve these vital commodities. The maximum daily feed advised for a pit pony is 20 lb., and this will replace 3 lb. of oats or 6 lb. of hay. It is better to replace part of the oats and part of the hay rather than to replace only one of these, so that 20 lb. of straw pulp might usefully replace 1½ lb. of oats and 3 lb. of hay. Straw pulp is eaten rather slowly, and it is better to give it in two or three feeds rather than all at once. Ponies take to it without much difficulty, but it is, of course, a good policy to commence with a small ration and gradually increase it.

Some colliery straw-pulping plants

A simple and practical straw-pulping plant for use on farms has been devised by Imperial Chemical Industries Limited for the Ministry of Agriculture, and at the request of the Mines Department two experimental plants have been installed at collieries in the Northumberland and Durham coalfield. Certain other collieries in the district have installed similar plants of their own volition. By the courtesy of the managements of the collieries concerned we have been able to inspect the experimental plants and to ascertain the companies' experiences with this method of feeding.

The I.C.I. straw-pulping plant is exceedingly simple, and can be built by the colliery bricklayers. Its capital cost is low — about £40 should cover it — and its total operating cost, including capital charges, labour, and caustic soda, is about £3 per ton of straw treated. Although the plant has been designed to conserve foodstuffs and not to secure financial economies, substantial savings have actually been effected in foodstuff costs in certain cases owing to the replacement of part of the hay ration by much cheaper straw.

The first colliery experimental plant was erected at the pony farm of Lambton, Hetton & Joicey Collieries Limited, and was brought into operation on August 21, 1941. It is illustrated in Figs. 1, 2, and 3, which clearly show the construction. The standard plant consists of two concrete or cemented-brickwork tanks separated by a concrete draining ramp. One tank is at a slightly lower level than the other to accommodate the slope of the draining ramp, and contains the pickling solution. It is 12 ft. long, 3 ft. wide and 1 ft. 10 in. deep, and has no outlet. On the first filling it is charged with water to a mark on the wall giving a depth of 10½ in., and 30 lb. of flaked caustic soda is added, but once the plant is in use, the solution is merely made up with water after each batch of straw has been pickled, and 16 lb. of soda is added. This tank holds 200 lb. of chopped straw at one filling; it is held below the surface of the bath by wire-netted frames loaded with concrete weights, as can be seen in Figs. 2 and 3. A minimum soaking period of 3 hours is required, but any additional time can be given without causing the pulp to deteriorate. After pickling, the pulp is forked to the draining ramp, whence surplus liquor flows back to the pickling tank.

After a convenient draining period, the pulp is drawn over to the second tank, where the soda solution is thoroughly washed out. The washing tank is 12 ft. long, 2 ft. wide and 2 ft. deep. It is provided with a bottom outlet to which is connected a flexible hose, the outlet of which is secured in a position to give the requisite depth of water in the tank. In Fig. 3 this hose can be seen in the far right-hand corner. To prevent the outlet from becoming clogged, the bottom of the tank is covered with a wire-netted grid covered with canvas, leaving a continuous gully, 2 in. deep, under the pulp and throughout the length of the tank. Wire-netted frames and concrete weights are again used to hold the pulp compactly below the water level. Running water is fed to the top of the tank either by a hose or by sprays, as shown in Fig. 1, and a washing period of at least 3 hours is necessary, or until all feeling of soapiness in the effluent has disappeared. Some doubt may be expressed as to the effect on livestock of improperly washed pulp; the safeguard is simple and automatic — the animals will not eat it.

On a basis of one batch a day, the daily output from this plant is 700 lb. of pulp, sufficient for 35 ponies on the maximum ration; but the stages of the process can be overlapped to produce either two or three batches daily, with a corresponding increase in throughput.

The Lambton, Hetton & Joicey Company's pony farm has a stock of 90 young ponies out at grass. The pulping plant was brought into commission last August to compensate for the shortage of grass, each pony having a ration of 8 lb. of pulp daily. From November onwards 2 lb. of oats and 3-4 lb. of oat straw were fed in addition to the 8 lb. of pulp. The stock have therefore been fed on straw pulp for about five months, and the chief horsekeeper reported to us that the animals were perfectly fit and that he had been unable to detect the slightest difference in condition due to change of diet.

The company then decided to experiment with straw pulp for ponies in full work, and built an underground plant at New Herrington colliery, this plant being started in December. The ponies commenced with a feed of 4 lb. of pulp daily, which was given as they came in from work. This was subsequently increased by a 2 lb. feed before starting work in addition to the 4 lb. feed after work, this 6 lb. of pulp replacing about 2 lb. of the normal hay ration. At the time of our visit it was too early to draw any definite conclusions as to the effect on working ponies, but there had been absolutely no sign of disorder.

The second experimental plant installed at the suggestion of the Mines Department is belowground in the Five-Quarter seam at Ashington colliery, and is illustrated in Fig. 4. It is almost identical in construction with the plant we have already described, and was brought into commission in the middle of November. Forty ponies are stabled here, and as a commencement each pony was given 5 lb. of straw pulp daily on returning from work, and four or five hours later was fed with 10-12 lb. of choppy consisting of equal quantities of hay and oats with a sprinkling of bran. The 5 lb. of pulp replaced about 1 lb. of choppy.

Here again, no change in condition was noticeable. Ponies working a really hard shift were affected adversely at first, but picked up again on getting used to the diet, and with the majority of ponies there was no change in condition. The colliery farm manager and the colliery veterinary surgeon reported that the condition of the ponies was satisfactory, and a decision has been taken to increase the straw-pulp ration to 10 lb. per day, equal to about 15 per cent. food value on their total ration.

We have also had leading particulars of a plant at another colliery in the locality. This plant was brought into use at the end of September, and supplies roughly 10 lb. of pulp per head daily to 94 ponies, 85 of which are underground. Oat straw was used for some time, a change to wheat straw being made later. Some 2 tons of hay are saved per month, with a corresponding financial saving.

Imperial Chemical Industries Limited have prepared data sheets giving full building details and specifications to enable any colliery to build a plant either in brick or in concrete as desired. All necessary particulars and advice can be obtained from that company's Agricultural Department. Information is also available from the District Supplies Officers of the Mines Department and from the local War Agricultural Executive Committee of the Ministry of Agriculture.

Drawings and Photographs accompanying the article