Chick Length and Organ Development

HatchTech Incubation Technology has put a lot of efforts in research on the relation between chick length at day 0 and the chick weight at day 7. Results showed a positive relation between chick length at day 0 and chick weight at day 7. A longer chick at day 0, has a higher development and growth potential than a shorter chick. A longer chick has probably on day 7 also better developed organs than a shorter chick. To investigate this, a trail was set up.

Experimental design

Chicks of a breeder flock of 33 weeks old, were selected for this trial. Birds were housed at a broiler farm of 9.000 birds and were fed a starter diet. At the day of hatch, chick length and weight was measured and sixty birds were selected and divided in three groups. The largest group contained chicks with a length between 20,0-20,6 cm, the middle group between 19,2-19,8 cm and the small group between 18,2-18,8 cm. At day 7, chicks were weighed again and the weight of the residual yolk, bursa of Fabricius, liver, heart, spleen and length of the intestines was measured.

Results

The correlation coefficient (R) of chick length at day 0 and chick weight at day 7 was positive again (R= 0,68; pThere was hardly any residual yolk found after 7 days. In 42%, 59% and 20% of the chicks of respectively the large, middle and small group was some residual yolk found. The amount of residual yolk varied between 0,03 and 0,32 grams.

The weight of the heart and liver was significant different between the large and small group. The weight of the spleen was significant different between all three groups. The chick with the largest chick length at day 0 had the heaviest heart, liver and spleen. There was no difference found between the weight in the bursa of Fabricius and the length of the intestine between the three different groups (Table 1).

Table 1. Average weight and length of c hick parameters per group of chick length

	Chick length day 0 (cm)*	Heart (gr)*	Liver (gr)*	Spleen (gr)*	Bursa (gr)*	Intestine (cm)*
large chick length group	20,2a	1,49a	7,78a	0,149a	0,30	92,56
middle chick length group	19,6b	1,43a	7,71a	0,122b	0,28	92,31
small chick length group	18,6c	1,25b	6,51b	0,120c	0,26	88,85
significant difference (p<0,05)	Yes	yes	yes	yes	no	no

*columns with different letters are significant different (p<0,05)

Conclusion

There was a positive relation between chick length at day 0 and chick weight at day 7. The heart, liver and spleen were better development at day 7 in the large chick length group compared to the small chick length group. The difference in heart and liver weight was not significant different between the largest and middle chick length group, probably due to the small difference between the group in chick length.

The heart is an important organ for blood supply with oxygen and nutrients for the main organs. The heart can contribute to an optimal development and growth of the chicks, which helps expressing the genetic potential. The liver and spleen are important organs as well for development and growth of the chick. The liver is the largest glandular organ of the bird and has different important functions like synthesis of different substances and maintaining the homeostasis of nutrients in the body. The spleen is a lymph organ and part of the blood filtering system and contributes to the immune system.

The length of the intestines and the bursa of Fabricius was in this trial not related to chick length. The size of the bursa of Fabricius might not be related to the development of the chick. The length of the intestine showed a lot of variation and was difficult to measure precisely, which might be the cause that no difference was found.
It can be concluded that chick length is positive related to the chick weight and the development of important organs like heart, liver and spleen. Chick length is, therefore, an important aim for hatcheries and broiler farmers. Chicks with a large chick length have better developed organs and may have a better potential for growth.

Note:
The Bursa of Fabricius
The bursa of Fabricius is a round sac and is located just above the cloaca in birds. Mammals generally have no bursa. The chicks’ bursa reaches its largest size a few weeks after hatching and then gradually decreases. B-cells, which are part of the immune system, develop, mature and migrate from the bursa to other part of the body.