Effect of lactic acid supplementation on pancreatic secretion in pigs after weaning

The effect of lactic acid supplementation to the starter diet, on pancreatic secretion in pigs after weaning was studied in three crossbred piglets (Duroc, Danish Landrace and Yorkshire). The pigs were weaned at 28 days of age, and adapted to live in metabolic cages for one week, after which the piglets were surgically fitted with a pancreatic duct catheter and a duodenal T-cannula for chronic collection of the pancreatic juice. Studies were then carried out over a period of three weeks, during which the piglets were fed three times a day (at 08.00, 15.00, and 22.00 h). During period I , the piglets were fed with a standard weaner diet (control), during period I I with a standard weaner diet supplemented with 2.5 % lactic acid period (lactic acid) and during period I I I with a standard wea­ ner diet (control). Beginning four days after surgery, samples of pancreatic juice were taken hourly from 08.00 to 16.00 h. During period I I , when lactic acid was added to the feed, the mean for all measured parameters of pancreatic secretion, except bicarbonate, increased in comparison to their values during period I . However this increase was only significant for volume and protein content. In contrast, during period I I I , when lactic acid was removed, there were no statistically significant changes in any of the measured parameters of pancreatic secretion compared to their values in period I I . Our data strongly indicate that dietary supplementation with lactic acid stimulates pancre­ atic secretion in piglets after weaning.


INTRODUCTION
The performance of piglets is often poor during the first few weeks after wea ning.It has been suggested that this postweaning lag phase may be partly related \ LACTIC ACID AND PANCREATIC SECRETION to an inability of the piglets to secrete sufficient endogenous digestive enzymes and gastric acid (Ravindran and Kornegay, 1993).Lindemann et al. (1986), andPierzynowski et al. (1995) reported that piglets have insufficient pancreatic en zyme activity during the period shortly after weaning.One strategy that suckling pigs employ to overcome insufficient acid secretion, is the conversion of lactose, ingested in the sow's milk, to lactic acid, by lactobacilli bacteria.(Ravindran and Kornegay, 1993).Recent reports have shown that replacing feed antibiotics by acidifying agents in the diets for early weaned pigs may not only provide a pro phylactic measure, but could be beneficial rather than harmful (Gabert and Sauer, 1994).Bearing all these facts in mind, our study attempts to determine the effect of adding lactic acid to the starter diet, on pancreatic secretion in pigs after weaning.

MATERIAL AND METHODS
Three crossbred piglets (Duroc, Danish Landrace and Yorkshire) were weaned at 28 days of age, and adapted to live in metabolic cages.Afterwards, the piglets were surgically fitted with a pancreatic duct catheter and a duodenal T-cannula for chronic collection of the pancreatic juice.During a period of three weeks, piglets were fed three times a day at 08.00, 15.00, and 22.00 h.All the pigs received a standard weaner diet (control) during period I ; a standard weaner diet supplement ed with 2.5% lactic acid (lactic acid) during period II ; and a standard weaner diet (control) during period III .Beginning four days after surgery, hourly samples of pancreatic juice were taken, from 08.00 to 16.00 h.After measurement of the volume, approx.1.5 ml of pancreatic juice was stored for analysis and the rest of the juice was reintroduced into the duodenum.Protein, bicarbonate, and digestive enzymes in the pancreatic juice were measured utilising methods described by Jensen (1997).

RESULTS AND DISCUSSION
During period II , when lactic acid was added to the feed, the mean for all measu red parameters of pancreatic secretion except bicarbonate, increased in compari son to their values during period I (Table 1).However this increase was only sig nificant for volume and protein content.During period III , when lactic acid was removed, the mean values for all measured parameters of pancreatic secretion except bicarbonate, showed a tendency to decrease when compared to period II , although none of these decreases were statistically significant.
It was previously suggested that the growth promoting effects of organic acids could be the result of an increase in nutrient digestibility, a decrease in dietary pH, a lowering of gastric pH and a decrease in bacterial growth (see Gabert and Sauer, 1994).Our data strongly indicate that lactic acid supplementation of feed for pig lets after weaning stimulates pancreatic secretion.Furthermore, Ravindran and Kornegay (1993) reported that low pH in the stomach stimulates the secretion of pancreatic bicarbonate.However, in our studies bicarbonate secretion was almost unaffected by lactic acid supplementation, which makes it unlikely that the stimu lation of pancreatic secretion observed was via a decrease in dietary and gastric pH.More studies need to be conducted to elucidate the mechanism of this effect of lactic supplementation on pancreatic secretion

TABLE 1
The mean and standard deviation for pancreatic juice variable, per unit body-weij *ht 0 7 5