Analysis of Factors Affecting the Pigmentation of Sanhuang Chickens and Existing Problems
In recent years, with the development of the domestic poultry industry and the continuous improvement of people's living and consumption standards, consumers have become increasingly discerning in their demand for meat products, and people in East China are particularly fond of Sanhuang chickens. In fact, the yellow color deposited in the shanks and subcutaneous fat of chickens is all lutein, and lutein is a general term for a class of natural pigments. Since chickens cannot synthesize lutein themselves, all lutein present in the chicken body comes from the feed. So, what causes the differences in chicken pigmentation? The following analysis examines this one by one.
1 Genetic factors
1.1 The ability of broilers of different breeds and strains to deposit lutein differs genetically; in particular, the current Sanhuang chicken breeds and strains are quite chaotic, with inferior ones passed off as superior.
1.2 When fed the same feed, hens pigment better than roosters, and older chickens pigment more deeply than younger ones.
2 Dietary factors (the raw material composition of the feed)
2.1 The feed ingredients that can provide valuable lutein are mainly corn and corn gluten meal, and the lutein content in corn and corn gluten meal varies greatly depending on the variety, harvest season, storage time and so on; therefore, where conditions permit, the lutein content of each batch of corn and corn gluten meal should be measured.
2.2 The content of rice bran, vitamin A, calcium and antioxidants in the feed affects the absorption of pigments.
2.3 Mycotoxin contamination in feed and litter (mycotoxins affect the metabolic and absorption pathways of lutein in chickens), anti-nutritional factors, dietary nutrient concentration, feed processing technology and so on all reduce pigment deposition.
2.4 Fat content in the feed. Only when lutein is deposited in the subcutaneous fat of chickens can the yellow color appear, so the amount of subcutaneous fat directly affects the pigmentation effect on chicken skin. Studies have shown that as the amount of added oil in the feed increases, the lutein content in chicken serum increases correspondingly. For example, adding more fat (especially vegetable oils) to the feed can significantly improve the pigmentation effect of lutein on the skin.
3 Environmental factors
3.1 Since light can promote the absorption of pigments, chickens raised in conventional transparent chicken houses pigment better than those in windowless, dark chicken houses.
3.2 A high-temperature, high-humidity environment, excessive stocking density and poor ventilation all reduce the utilization of lutein and affect pigment deposition.
4 Feeding management factors
4.1 Pigmentation of the chicken body is a cumulative process. From the start of intake of lutein-containing feed to the appearance of yellow on the shanks and skin, at least 2 to 3 weeks are needed (if a high degree of yellowness is required, a longer time is needed); at the same time, pigment deposition is not evenly distributed over the entire chicken skin, but is somewhat selective.
4.2 Feed intake. The amount of feed intake directly affects the pigmentation effect. The more they eat, the better the pigmentation effect.
4.3 Feed storage time. The longer the feed is stored, the worse the pigmentation effect of the chickens after use.
5 Chicken health factors
The health status of chickens directly affects pigment deposition in the chicken body, and the effect is even more obvious when the intestinal absorption function is impaired. Diseases such as coccidiosis, salmonellosis, Newcastle disease and chronic respiratory disease all severely reduce pigment deposition.
6 Pigmenting product factors
The vitamin A activity, physical form, utilization rate and stability of pigmenting agents are all related to pigment deposition, and the pigment deposition rate of different pigmenting agents also differs to a certain extent.
7 The relationship between the color of chicken skin and shanks and taste
Research in animal nutrition has so far found no nutritional role for lutein. However, when purchasing chickens, besides relying on past purchasing experience and choosing chickens with brand labels, consumers mainly judge whether a chicken is good by relatively intuitive methods such as the color of the feathers, skin and shanks. They generally believe that the yellower the chicken, the longer the rearing time, and therefore the better the taste after cooking; this view actually reflects a misunderstanding. As we know, the important substance determining chicken meat flavor is inosinic acid, and the quality of the flavor depends on the type and content of inosinic acid. Fast-growing Sanhuang chickens currently on the market are generally fed compound feed containing lutein and have a short rearing period.
All sectors of society and the relevant departments should provide correct guidance so that consumers gradually reduce their requirements regarding chicken pigmentation, and feed manufacturers should also strengthen self-regulation; in this way, the extra feed costs caused by excessive addition of pigments can be reduced. Poultry breeding institutions should breed white chicken varieties similar to or even better than "Sanhuang chickens", breaking the prejudice that yellow chickens must taste better than white chickens.