Use of Antibiotic Supplements with Separated Milk in Pig Feeding

New Zealand Journal of Agriculture, Volume 90, Issue 1, 15 January 1955, Page 85

Use of Antibiotic Supplements with Separated Milk in Pig Feeding

SINCE 1949 numerous experiments have been conducted in Europe and America to measure the response of pigs to the feeding of a growing array of antibiotic supplements. None of this research has included the use of antibiotics as supplements to a main diet of skimmed milk, which is the major pig food in New Zealand but not elsewhere. In this article D. M. Smith, Research Officer, Department of Agriculture Animal Research Station, Ruakura, discusses trials with antibiotic supplements for fattening pigs fed on separated milk.

IN general the published results of overseas trials have indicated that antibiotics may have five major effects: (1) They increase daily food intake, (2) They increase growth-rate. (3) They increase efficiency of conversion of feed to pig meat. (4) They improve the feed value of plant proteins to a stage where they can satisfactorily replace most, if not all, of the more expensive animal proteins in pig feeds. (5) They are assumed to control many unspecified types of bacterial gut infections which depress growth. When the results of overseas research are being interpreted it is necessary to understand the conditions under which the experiments were conducted. The most - important feature is that the basic feed consisted of some type of grainmaize, wheat, oats, or barley. These grains were

supplemented with some protein-rich food. The second feature of importance is that the pigs were usually fed to appetite; that is, they ate from selffeeders in which meal was available to them at all times. This self-feeding of grain mixtures is common commercial practice in the U.S.A., so that such experimental techniques were in line with farming methods. New Zealand pig feeding methods differ greatly from these. Separated mk 90 per cent, o which is water, s the main, often the only, feed available to sows, litters, and fattening pigs. Since no country other than New Zealand uses separated milk as the major diet of pigs, no overseas experiments have been conducted on this material. For this reason a series of trials was begun at Ruakura in 1952 to see if antibiotic supplements to

separated milk had any effect when fed to fattening pigs. In addition, as there was. evidence from the U.S.A, that young pigs showed greater responses than older pigs, experiments were also conducted on. litters suckling sows. A summary of the results of these experiments follows. Effect on Creep-fed Pigs 1. Effect of penicillin supplement in milk and meal fed to pigs in the creep: This investigation was carried out over two seasons. Eight sows and litters were used in each season; four of the litters were fed antibiotics from the end of the third week to weaning at 8 weeks and the other four received no supplement. The litters were weighed once a week and the creep food consumption was measured daily. One of the difficulties with this type of experiment is that the growth of a litter suckling the sow is the result of the sow’s milk production as well as creep intake. It would be very easy to give credit to the particular type of creep feeding used for any extra gains which were the result of higher sow production. For this reason the milk production of all the sows used in this investigation was measured and its composition determined. The combined results of the two experiments are shown in Table 1. The period covered is the last 5 weeks,

since creep feed was available over this time. The litters on the two treatments received approximately the same amount of milk from their mothers, but those receiving penicillin ate more feed from the creep. As a result they

gained an extra 21b. per pig over the last 5 weeks. Two features of this experiment which are not shown in the table were: —

(a) In the first season the heaviest litter and the lightest litter at weaning were in the no penicillin group and in the second season the heaviest and the lightest litters were both in the penicillin group.

TABLE I No. of No. of Feed per pig from: Gain per Weaning Treatment sows pigs Sow Creep ' pig weight lb. " lb. lb. lb. Penicillin in creep ..8 77 18.12 19.47 27.07 37.2 No penicillin .. ..8 78 18.74 16.03 25.1 35.7

TABLE 2 Treatment Control Penicillin Control Aureomycin Weight at start (lb.) ..40 40 40 41 Weight at finish (lb.) 100 101 101 102 Days on experiment .. 56 . 54 60 56 Gallons per lb. of gain 2.22 2.26 2.40,. . 2.32 ■ Group fed ' ' ' „ „ Gallons per lb. of gain 2.37 2.37

(b) The total feed required to produce a pound of gain in the litters (sow’s milk and creep combined) was the same for the two groups. Efficiency, therefore, was not increased as a result of penicillin feeding. The following conclusions may be drawn: —

The addition of penicillin to a creep mixture will in most cases result in an increased feed intake by the suckling pig. This increased intake will result . in slightly heavier weaning weights. This conclusion is true only where milk and meal, especially meal, are available to the litter at all times. It would be quite false if a small quantity of meal were fed twice a day in the creep as it so often is on farms. Effect on Fattening Pigs 2. The effect of antibiotics fed to fattening pigs: One of the effects of antibiotic feeding found by overseas workers was an increase in feed conversion efficiency. Obviously an improvement in the amount of meat produced from each gallon of milk fed on New Zealand dairy farms is most desirable. The second experiment of the series at Ruakura was therefore aimed at finding the effect of antibiotics on feed economy when antibiotics were fed with separated milk. In this experiment every pig received the same feed at any given weight. Both antibiotics were added to the milk at the rate of 5 gm. per ton of dry matter. Any effect of antibiotics on appetite was therefore eliminated. The treatments used were: (a) No antibiotic, (b) penicillin, (c) no antibiotic, and (d) aureomycin. Four lots of pigs were fed individually and two

lots of pigs were fed in groups. The results are shown in Table 2.

TABLE 3 Treatment Control Penicillin Weight at start (lb.) 49 50 Weight at finish (lb.) 98 100 Days on experiment .. 36 36 Gallons per lb. gain .. 2.63 2.61 Mean intake per day (gallons) .. .. 3.58 3.61

None of the differences shown in the table is statistically significant. In each experiment some of the control pigs grew better than their litter

mates that received antibiotics and some did not. Tt was ennclnd ed therefore, that

it was conciuaea, rnereiore, iuai neither penicillin nor aureomycin increased the efficiency of feed conversion of separated milk when the milk was fed in rationed amounts. However, as was stated earlier, overseas experiments with antibiotics were mainly conducted under ad lib. feeding conditions. Therefore, if antibiotics stimulated the pig to eat more, increased growth-rate, but not necessarily improved feed economy, should result.

The next experiment was therefore conducted with pigs fed in groups and having access to milk at all times. The results of this experiment are shown in Table 3. Again there is no difference in response between the pigs receiving penicillin and those not receiving it. All the pigs in this experiment scoured badly and showed the usual signs of overfeeding associated with the practice of ping the trough full of milk at all times. it was concluded that under separated milk feeding conditions the use of antibiotics did not increase intake an( j hence growth-rate. It appeared that sheer “ hysical holding capacity rather than appetite was the factor limiting intake. It should be realised that a pig weighing 1001 b. will drink about 4| gallons of milk per day. This represents 45 per cent, of its bodyweight. On the other hand a grain-fed P 1? °n e same weight needs to. eat This failure of antibiotics to improve performance. in . either rate or efficincy -X, + in + the . tr^ already described led to two further expenmenf In one the possible effects of the high dilution of antibiotics resulting when normal doses were fed with

separated milk was tested by using 50 gm. per ton of dry matter against the normal rate of 5 gm. In the second experiment the suggestion that the high standard of cleanliness and management at Ruakura prevented the possibility of any beneficial effects from antibiotics through control of sub-clinical infections was tested in trials under farm conditions. The first experiment involved five groups as follows: (a) Control, (b) penicillin at the rate of 5 gm. per ton of dry matter fed, (c) penicillin at the rate of 50 gm. per ton of dry matter, (d) streptomycin at the rate of 5 gm. per ton, and (e) streptomycin at the rate of 50 gm. per ton. The second experiment was' conducted on two farms where housing and handling conditions were typical of those found in the Waikato. On one farm penicillin was fed and on the other streptomycin,: both at the standard rate of 5 gm. per ton of dry matter. A member of the Ruakura staff visited both farms twice daily and fed the experimental animals. The pigs were weighed each week and the rations adjusted according to liveweights as in the first fattening experiment. The results of this third series of trials are shown in Table 4. Both penicillin and streptomycin reduced feed requirements per pound of gain by approximately 6 per cent., and the time required to reach 1101 b. liveweight by 6 per cent. As discussed later these differences are so small as to have little, if any, practical significance. There was no difference between the two levels of supplement. In the farm field trials the control and supplemented animals grew equally well, with no benefit from antibiotics. Summary of Results Results of the 10 trials can .be summarised as follows: 1. The response of litters fed antibiotics in the creep was small and expressed by increased appetite and rate of gain, which was possible only because of the ad lib. creep feeding system used. 2. The bulkiness of separated milk imposes a physical limit to the daily intake of pigs fed solely on this food, so that the addition of antibiotics cannot increase food consumption. One of the main claims for antibiotics is that they increase feed intake and therefore result in faster growth. This particular response (that is, faster growth through greater intake) is not likely to be expressed under New Zealand conditions. 3. In 6 trials of the 10 carried out with fattening pigs there was no response.. In 4 trials a small gain was

measurable. This represented a saving of 4 days in the time taken, and 10 gallons in the feed needed, to bring a pig from weaning to pork weight.

TABLE 4 (a) Ruakura experiments Treatment Control Penicillin Streptomycin 5 gm. 50 gm. 5 gm. 50 gm. Mean weight, at start (lb.) .. 50 52 51 . 52 51 Mean weight at finish (lb.) .. 110 110.5 111 110.8 110 Days to gain 601 b. .... 65 63 61 62 61 Gallons per lb gain .. .. 2.84 2.69 2.66 2.69 2.66 (b) Farm trials Farm I Farm 2 Treatment Control Penicillin Control Streptomycin Weight at start (lb.) .... 28 28 29 29 Weight at finish (lb.) .... 79 80 89 90 Days on experiment .. .. .. 63 63 68 68

. An important question is whether the above ; results cases out of 10 showing a small improvement sent a recommendation for the use of antibiotics with separated milk in fattening pigs. It may well be asked just what 4 days earlier marketing and 10 gallons of milk saved per pig mean in practice to the New Zealand farmer. The feeding. of : antibiotics does not increase the number of pigs carried at any one time. This number depends entirely on the amount of milk available from the dairy herd ' daily, milk which must be consumed as it is produced. If antibiotic-fed pigs can be marketed 4 days earlier, there is left available the.milk which would otherwise have been used to feed them over that period. The saving, therefore, consists of a perishable product available daily for a few days. Where cereals are fed, as in Europe and America, the feed saved is still in the barn. It can be stored there until needed or sold. This situation does not apply with separated milk. Where the number of pigs kept on a New Zealand farm is such that they can readily and economically drink every gallon produced without overfeeding and this is true of only a few farms todaythe milk saved by antibiotic feeding could be used economically. Where the pigs are already being overfed the extra milk would be an embarrassment. It is suggested, therefore, that where antibiotics produce results advantage

can be taken of the beneficial effects only on farms where pig numbers are high and really efficient use is already being made of the milk produced. In other words, any beneficial effect of antibiotics is a useful adjunct to already high production efficiency, but is not a means of improving basically low-efficiency units. The experiments indicate that even where production efficiency is high there is only a 40 : 60 chance that any improvement will result. As the antibiotics used cost approximately 2s. per pig at 1954 prices and 10 gallons of milk if used to produce extra pig meat would be worth about 3s. 6d. on an efficient farm, there is a profit from antibiotics of Is. 6d. per pigFinally, antibiotics will not make pigs grow faster or more economically if slow growth and low efficiency are due to poor management, poor housing, and inherently poor stock. Similarly, no farmer would expect a positive response in his pastures from lime if phosphate was the element lacking. On present theories the position may be interpreted as follows: — 1. The possibility of increased intake with antibiotic feeding may be ruled out. In any case research at Ruakura has shown that overfeeding of young pigs leads to chronic digestive upsets, so that methods of increasing intake of bulky milk diets should be avoided rather than , encouraged.

2. The improvement of the value of proteins by antibiotics to a stage where plant proteins can replace animal proteinsan important feature of their use overseasis of no interest in New Zealand, where separated milk, an animal protein of high biological value, is the main feedstuff. 3. The remaining possibility arises from the theory that the antibiotic acts on the bacteria of the gut, depressing harmful organisms and encouraging those of value to the host. If antibiotics are expected to produce results wherever tried in New Zealand, it must be accepted as fact that all pigs harbour harmful organisms in sufficient quantity to depress growth and affect feed conversion. This is unlikely. It is not suggested that these experiments represent the last word on the use of antibiotics in pig feeding in New Zealand. As yet there is nofactual explanation available on the way these materials operate in the gut.. To date experimental work has merely measured gross effects. Until more' detailed research at present in progress in England and America has; yielded precise information on the mode of action of the various types of antibiotics there is no point in continuing experiments which measure end results without providing an explanation of the process involved. - In the meantime, however, the experiments described, interpreted on the basis of present knowledge, suggest that the indiscriminate use of antibiotics with separated milk is unwarranted.