Pig International - November 2017 - 25
PigInternational ❙ 25 prerequisite for efficient feed digestion and good gut health. Neonatal pigs have a rather high gastric pH (5 to 6) facilitated by the strong buffering capacity of colostrum. This might appear contradictory to the above, but there is a reason. A more tolerant gastric pH allows passage of ingested environmental bacteria (not all of them are pathogens, after all) from the stomach to the small and large intestines for the establishment of normal gastrointestinal microflora. This is considered essential and even beneficial for the animal's long-term health. Usually, the predominant beneficial bacteria in the stomach are lacto- and bifido-bacteria, whereas in the intestines there is a mix of bacteria. Nevertheless, after the first few hours of suckling, gastric pH drops to about 4 to remain there until weaning, and in most cases, during the first three to four weeks post-weaning. Afterwards, gastric pH drops gradually until it reaches mature levels (2 to 3). The benefits of early high pH A moderate gastric pH of about 4 in suckling pigs is favorable for the activation of chymosin (rennin), the enzyme responsible for milkclotting in the stomach. Without the action of chymosin, milk would pass quickly and largely undigested in the small intestine where it would serve as substrate to pathogens. Although pepsin, also a protease, can also clot milk, albeit at reduced efficacy than chymosin, the latter (chymosin) has weaker proteolytic activity. This might again appear counterproductive, but it is beneficial as it protects the very important milk immunoglobulins from digestion. Having a moderate gastric pH also benefits proliferation of lactobacteria while excluding other pathogenic organisms. A healthy population of lactobacteria produces copious quantities of lactic acid that stabilize gastric pH. However, this results in the depression of hydrochloric acid. In other words, in the presence of lactic acid, there is no incentive for the secretion of another acid. This is one of the reasons why many post-weaning diets are fortified with lactic acid, among many other organic acids. Thus, in brief, it is apparent that suckling piglets exhibit very limited capacity for secretion of hydrochloric acid, which is not strongly stimulated by sow's milk. This is erroneously considered as a negative aspect, but in contrast it is important for the survival of piglets receiving sows' milk. Weaning upsets pH balance At weaning, usually too early for piglets to consume enough creep feed, gastric pH remains relatively high. A lower pH is required for the efficient digestion of plant- and animal-derived proteins (other than milk) found in most post-weaning diets. This is because the activity of pepsin peaks at November/December 2017 ❙ www.WATTAgNet.com very low pH levels about 2 to 3.5. Some resistant proteins (mostly of plant origin) are digested only at the lower optimum pH, whereas no significant digestion of any protein source occurs above pH 4. Provision of dairy products (mimicking the sow's milk diet preweaning) in post-weaning diets has been shown to reduce gastric pH in weaned pigs, aiding digestion. Read more: Learn how to optimize pig gut health, www. WATTAgNet.com/articles/19946 Protein indigestion in the young pig not only reduces efficiency of feed utilization but it also gives rise to intestinal microflora populations that thrive on protein, especially to opportunistic pathogens such as Escherichia coli. This situation usually ends with the development of diarrheas, and occasionally death, unless pigs are treated with antimicrobial agents (antibiotics, zinc oxide, copper sulfate, organic acids, phytogenics, etc.) that control intestinal pathogens. Thus, in many cases, enhancing protein digestion eliminates the need for expensive medications and prevents the outbreak of costly diseases. In most commercial farms, however, feed digestibility is ignored when diarrhea problems are encountered. Prevent protein indigestion To prevent protein indigestion in newly weaned pigs, several