Despite natural defence mechanisms, enteric problems continue to be the main concern in intensive poultry production. This is reinforced by the progressive limitation on the use of antibiotics. Therefore digestive health, in its broadest sense, has become the main priority in livestock production.
Over the last decades the poultry industry, but chicken meat production in particular, has witnessed steady progress in its production results. This development is certainly a success story that continues to improve both production and demand for poultry meat and eggs. There are many factors driving this progress. The genetic evolution of the broiler chicken is a determining factor in the poultry industry’s success story, with several publications showing the amazing progress made by genetics companies over the last 60 years. Although analysis of production improvements shows proof of a job well done, this should also help us to understand the problems that modern poultry production faces.
A higher carcass yield, as shown in Table 1, means that there has been a greater increase in nutrient demanding parts (muscles and bones) in relation to supply tissues (cardio-respiratory and digestive). The modern chicken has greatly increased its growth capacity (more and faster weight gain), but their digestive and respiratory systems are proportionately behind in this development. This means that the tissues responsible for providing the resources for growth are under pressure, which increases the chance for dysfunction and disease (ascites, thermal stress, enteric problems). The case is particularly complex for the digestive system because it is responsible for the digestion and absorption of nutrients, but it is the main immune organ as well. An optimal and fast development of the digestive tract is a key factor for optimal utilisation of feed and prevention of enteric problems. To support the genetic potential of broilers to produce meat, we have to understand how to support the three key elements of a good gut function; the gut wall, the microflora and the immune system.
Growth and intestinal development
Already in the last third of the incubation period, the development of the digestive tract exceeds other embryonic tissues. This faster growth, both in length and diameter, remains during the chicken’s first days of life. The intestinal mucosa is part of this fast development by increasing the volume of the villi three to five times. In the first few days of a chicken’s life, the digestive system develops much faster than the rest of the body. The development of digestive structures goes along with the activation of their functional capacity. Enzyme activity increases rapidly in the first week of life but not in a homogeneous way. The presence of lipids and proteins in the yolk sac may explain an earlier development of lipases and proteolytic enzymes. There are studies that show a close relationship between the presence of enzymes produced by enterocytes (sucrase and glycosyltransferase) with the number of enterocytes or the size of the villi. Amylase, lipase and trypsin substantially increase their presence among the days in the first week of life and continue to grow rapidly until day 14.
It is known that the gut of newly hatched chickens has a virtually non-existent microbial load. After hatching, the colonisation of the gut by different groups of bacteria happens very fast and the profile of the populations that constitute the microflora varies depending on age, intestinal section, type of diet, etc. Already in the first day of life there are bacteria counts up to 108 CFU/g in ileum and 1010 CFU/g in the caecum, while the maximum populations are established around one week later: 109 CFU/g in ileum and 1011 CFU/g in caecum. However, the type of bacteria populations is not stable before day 21 in the small intestine or day 40 in caecum, where microbial load is greater and more diverse.
The interaction between the microflora and digestive tract development and functionality is rather clear and includes aspects such as active participation in the digestive processes, control of potentially pathogenic microbial populations, development and epithelial repair and local immune responses. It is important for proper development of birds to maintain a healthy and balanced intestinal microflora from the first day of life. To illustrate this relevant point, populations of E. coli and Streptococcus in faeces of chickens can already be detected two hours from hatching, thus promoting good bacteria to settle from the very first hours of life can be crucial.
The intestines are particularly susceptible to external aggression. Together with feed, pathogenic bacteria, protozoa, fungi, mycotoxins, and other elements that pass the digestive tract, are a constant challenge throughout the entire life of the birds. These threats can be more dangerous in the early days of life, when the chick is subjected to a period of fasting before reaching the fattening farm. This forced fasting is associated with a delay in the process of maturation of the intestine and even with lesions in the intestinal mucosa that limit the production results and increase the risk for sickness. To reduce the negative impact of fasting, minimising injuries and promoting the development of the intestinal mucosa become critical factors for an optimal start of the flock. When considering the fact that as much as 75% of the immune cells in the birds are found in the small intestine, this indicates the importance of a healthy and well protected digestive tract.
The use of feed additives to support intestinal development is common practice nowadays. Among them butyric acid plays a prominent role due to its unique properties that have been scientifically proven in the field of digestive health. The effects related to the inclusion of butyric acid in the diets of animals have been known for many years. They include: the positive role on the development and repair of the gut wall, modulation of the microflora and modulation of inflammation.
Perstorp has introduced ProPhorce SR, an efficient butyric acid solution with optimal handling properties. Due to the esterification with glycerol, the product is free of the unpleasant butyric acid smell. The esters are also able to bypass the stomach so they will be fully available at intestinal level. With ProPhorce SR, animals will get the extra support needed to perform, especially when their intestines are under a lot of pressure (Figure 1).
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