1. A review of the literature relating to the frequency at which pigs suckle under natural conditions was made. The evidence indicated that the average interval between successive sucklings is approximately 1–1¼ hr.2. A number of sows and their litters were continuously observed for varying periods of time under natural conditions and a similar average interval between sucklings was observed.3. A review of the literature relating to the determination of milk production of sows was made. This showed that the majority of previous workers imposed, during the periods when the litters were being weighed before and after every suckling, a suckling frequency that did not simulate the natural behaviour of the animals. Evidence suggesting that the imposition of such unnatural conditions invalidated the findings, in so far as they might indicate the true milking capacity of the animals, was discussed.4. An experiment to obtain direct evidence on the importance of the suckling interval in relation to the milk obtained by the pigs was carried out. Conclusive evidence was obtained that when suckling was allowed every hour, both the quantity of milk obtained by the litters and their live-weight gain in 24 hr. periods were much greater than was the case when suckling was allowed only every 2½ or 3 hr. In addition, the pigs on the hourly suckling frequency utilized their milk intake more efficiently.5. An experiment was carried out in which an attempt was made to obtain, under natural conditions, a valid estimate of the 56 days' lactation yield of three Large White gilts. The method of weighing the individual pigs before and after suckling was used, and the animals were allowed to suckle every hour.6. The estimated average lactation yield was 768 lb., with a range of from 882 to 655 lb., although it was suggested that the true yield might be some 5–10% higher. The figures obtained in this work were shown to be very much higher than the yields reported by most of the previous workers.7. The nursing and suckling behaviour of the dams and their litters was studied. Observations of significance in relation to the variation in growth of pigs within a litter were made.8. Data were obtained concerning the average amount of milk obtained by individual pigs at a suckling, the total amount ejected at a suckling, the effect of daylight and of darkness on the amount of milk obtained, the relative productivity of the individual mammary glands and the efficiency with which the milk intake was utilized by the individual pigs in the litter.9. A close positive relation between milk intake and live-weight gain during the first 3 weeks of life was found. During the last 5 weeks of lactation, when supplementary food was available, this close relationship was not seen.10. The growth rate of the suckling pig, as related to the supply of food, was discussed. The evidence available suggested that the supply of sow's milk was frequently insufficient to meet the requirements of the pigs for optimum growth.11. The chemical composition of sow's milk in relation to the stage of lactation was studied.

I. Pigs were weaned from the sow at 2 d of age and reared on a diet of cow's milk supplemented with vitamin D, and antibiotics. The effects of four levels and two frequencies of feeding, and the temperature of the environment were studied in relation to the performance of the pigs and the digestion of the milk protein. Pigs fed at the two lower levels receivedadiet of cow's milk, but at the two higher levels cow's milk was spray-dried and reconstituted to 20 % total solids. A comparison was also made between cow's milk and spray-dried reconstituted milk, both fed hourly with 12.5 % total solids. The pigs were slaughtered at 28 d of age. 2.No differences in the nutritive value or digestion of the milk protein were found when cow's milk and reconstituted milk were fed with a total solids content of 12.5 yo.3. Increasing the level of feeding resulted in a faster growth rate, and some deterioration in the feed conversion efficiency. The growth rate of the pigs from 2 to 28 d of age when fed at a high level greatly exceeded that of sucking pigs reared on the sow. The retention of the dietary nitrogen also improved with increased feed intake. A highly significant inverse linear correlation of N retention with age was found at all levels of feeding. The milk protein was efficiently digested at all levels of feeding. 4.The mortality rate was very low but there appeared to be some association of losses with a high level of feeding during the first few days of life.5. Feeding hourly compared with feeding twice daily improved the feed conversion efficiency, although the effect on growth rate and N retention was small. The retention of digesta in the stomach appeared to be an important factor in the regulation of the amount of digesta in the small intestine and in the maintenance of digestive efficiency. The stomachs of pigs fed twice daily contained considerably greater amounts of digesta than those of pigs fed at hourly intervals. There was little difference in the amount and composition of digesta in the small intestine and caecum at either frequency of feeding.6. No differences were found in the performance of the pigs, N retention or the efficiency of digestion of the milk protein when the environmental temperature was maintained either at zoo throughout the experiment, or at 30' gradually reducing to zoo during the first 14 d.Artificial rearing methods which involve removal of the pigs from the sow soon after birth and rearing them on milk substitutes could have the following advantages over the conventional rearing on the sow: reduction of losses of pigs through control of environment, improvement in their growth rate by making available more nourishment than that supplied by the sow, elimination of lactation and shortening of the reproductive cycle of the sow, thus increasing her productivity by enabling her to produce a larger number of pigs per year. The economic advantages of a successful artificial rearing routine could be considerable.Earlier work at Shinfield provided basic information on the qualitative and q...

SUMMARY Streptococci, lactobacilli and coli‐aerogenes organisms were isolated from pigs receiving penicillin, chlortetracycline or copper sulphate as dietary supplements. Changes in their numbers, physiological type and sensitivity to the supplements fed are described. Penicillin and chlortetracycline rapidly induced a population resistant to the antibiotic fed, but no changes were detected in numbers or types of organisms isolated. Copper sulphate caused a reduction in the numbers of streptococci and a change of predominant type from non‐lactose‐fermenting to lactose‐fermenting; there was also a change from a flora in which L. acidophilus predominated to one in which L. brevis and L. cellobiosus tended to become dominant.

I . Thirty-five pigs were fitted with single re-entrant cannulas in either the duodenum, jejunum or ileum. A further twenty-four pigs were used in a conventional digestibility trial.2. Methods for collecting, sampling and returning digesta were developed. 3.A 'practical-type' diet and two purified diets were used, fed twice daily. 4.Flow and p H of digesta were measured hourly in the duodenum and jejunum, and every 6 h in the ileum.5 . In the duodenum and jejunum there were clear flow responses to feeding, while such an effect was not found in the ileum where the flow-rate was much lower and more uniform than in the former sites.6. In the duodenum and jejunum, and within 6 h periods in the ileum, there was considerable variation in the flow-rate between different pigs within each hour but there was less variation in pH.7. The pattern of flow in the duodenum and jejunum was similar for each of the diets but the total flow and the average pH in 24 h differed significantly between diets. There were more digesta of a lower p H from the 'practical-type' diet than the purified diets.8. The p H in the duodenum was highest after feeding and decreased with increasing time after feeding. In the jejunum and ileum the p H varied over a much smaller range than in the duodenum.9. Collections for 6 h periods appeared to be insufficiently long to predict the values obtained in 24 h collections with reasonable accuracy.Interest in improving the utilization of feeding-stuffs by farm livestock has led to a wide range of studies on the function of the gut, particularly in ruminants and, in recent years, in pigs, using animals surgically fitted with simple or re-entrant cannulas. The methods used in such work on simple-stomached species have been reviewed by Laplace (1972) and the results of trials with pigs have been discussedThe re-entrant cannula method was used to study the general characteristics of the digestion of a variety of diets in the intestines of growing pigs. Particular attention was paid to developing methods of surgery, housing and digesta collection. A sufficient number of animals was used to assess the variability of the processes. An estimate of the extent of digestion and absorption in the large intestine was made by comparing results from pigs with re-entrant cannulas sited in the terminal ileum with results from pigs without cannulas participating in a conventional digestibility trial. This paper describes the flow of digesta and their pH; studies on the contents of dry matter, ash, water, nitrogen, amino acids and enzymes in the same digesta will be described in subsequent papers.

No abstract