Article by Phoebe Zhao, Shandong Longchang Animal Health Product CO.,LTD – Regional Manager
During the cycle of 42 days, broilers (for example) grow rapidly from about 42 grams to about 2735 grams with a weight gain of more than 65 times. In this process, the growth of each stage is very critical and interlocking. Under the same feeding conditions, if the weight of the chicks on the 7th day is 1g less, the slaughter weight of broilers on the 42nd day will have 10g less. To achieve the best slaughter weight, we must understand the characteristics of visceral growth and development in the early stage of the chicks, especially in the first 7 days, because this is closely related to weight gain.
1. Digestive organ
The small intestine of newly hatched chick grows and develops very quickly, accounting for 3.8% of the body weight at the time of hatching, and 8.9% of the body weight after 48 h, and the fasting chicken intestine accounts for 4.5% of the body weight after 48 h. Feed intake in time will be beneficial to the development of the digestive tract in the later period. At 6 days of age, the length of the duodenum increases nearly twice than before, and the length of the ileum and jejunum increases by nearly 50%.Then the emptying rate of the intestine also decrease, that is, the time that the diet stays in the intestine prolongs. The relative weight of glandular stomach and muscular stomach is the highest at 4 to 7 days old, and that is 7 to 10 days for the relative weight of liver and pancreas and 7 days for the relative weight of small intestine. From the perspective of allometric growth indicators, the maximum growth rate of muscular stomach is 1.5 times more than the weight growth rate, the maximum growth rate of glandular stomach is 2 times more than the weight growth rate, the maximum growth rate of the liver is 2.3 times the weight growth rate The maximum growth rate of the small intestine is 3 times more than the weight growth rate, and the maximum growth rate of the pancreas is 6 times more than the weight growth rate.
2. Development of intestinal mucosa
The development of the jejunal epithelium is completed 72 to 144 h after hatching, and the duodenum is progressed to 216 h after hatching. From 7 days before hatching to 7 days after hatching, the height and girth of the chicks increase about 9 to 11 times. The proportion of differentiated crypt intestinal epithelial cells reduce to 50% to 60% around 2 days after hatching, and the proportion of proliferating villi cells reduce to 10% to 20% 6 days after hatching. The recession process is completed 48 hours after hatching, and the number of villi is increased by branching and splitting, and the maximum number arrives at 7 days.
From 4 days to 21 days, the secretion of bile increases by 8 to 10 times, and the peak period of secretion was 10 to 14 days old. From the time of hatching to 21 days of age, the amount and activity of amylase, trypsin, and lipase secretion in the duodenum is the lowest at 4 days of age. The activity of the enzyme decreases with increase of distance from the duodenum. The difference becomes more significant as the age of the chicks increases. Amylase, trypsin, chymotrypsin, and lipase activities in the intestine reach peak at 10 days.
4. Changes in the absorption capacity of the digestive tract
From 4 days to 10 days, feed consumption increases fourfold, and the rate of emptying decreases by 30%. After 10 days of age, feeding increases, but the emptying rate doesn’t change significantly, indicating that the digestive capacity of chicks is rapidly improving. Starch digestibility of chicks from 1 to 22 days old, starch digestibility of egg-laying chicks increased rapidly after hatching, reaching 98.6% at 4 days of age. The diet consumed by meat-producing chicks was twice that of the former. Starch digestibility The peak value was not observed until 8 days of age, after which the digestibility decreased slightly. The digestibility of nitrogenous compounds in the small intestine increased from 78% at 4 days of age to 92% at 21 days of age. The small intestine has a good intake of carbohydrates and methionine, but due to the influence of early liver development, the secretion of bile is insufficient. The intake of fat and fat-soluble vitamin A is suppressed.
In summary, we can see that broiler chickens are far from reaching maturity during their lifetime growth and development, and their internal organs are not yet perfect, especially in the first 7 days. In the early stage, adding appropriate amount of endogenous Runeon (Bile acids) in feed or drinking water can alleviate and solve the problem of poor absorption of nutrients like lipid due to inadequate development of the internal organs especially the liver,. Runeon (Bile acids) play an important role in the whole fat metabolism process such as emulsification, activation of lipase, enhancement of lipase activity, operation of fatty acids, etc. At the same time, bile acids as a signal molecule can regulate the metabolic activities of lipids, sugars and other substances in the body, which can promote the early growth of chick of great significance.
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