Thau Kiong Chung, Moises John Reyes
THAU KIONG CHUNG and MOISES JOHN REYES* present the proven advantages of 25(OH)D3, a more bioactive form of vitamin D3 to support skeletal health, promote immunity, boost production and processing performance, to reduce the number of birds either condemned or downgraded by the processor.
Advances in broiler genetics have improved feed efficiency rates and accelerated body weight gains. However, genetic advancement comes with shortcomings. Modern broilers are less immune-competent. Also, bone development has not kept pace with body weight gain, resulting in increased incidence of locomotion problems in broilers. This translates into lameness, reduced performance, as well as increased carcass and processing condemnations at slaughterhouses. Clearly, nutrition- based solutions are important to support skeletal development and deliver stronger and healthier birds. Vitamin D in the form of 25-hydroxycholecalciferol (25(OH)D3) certainly plays a vital role in broiler production.
Dietary vitamin D3 vs 25(OH)D3
25(OH)D3 (Hy-D, DSM Nutritional Products), a commercially available and regulatory approved feed additive is routinely used in combination with vitamin D3 in broiler diets. Chickens fed 25(OH)D3 rapidly increase and sustain the blood circulating level of 25(OH)D3. The absorption of 25(OH)D3 is faster than that of vitamin D3 because molecular polarity is greater in the former than in the latter. 25(OH)D3 is absorbed via portal circulation through passive diffusion and does not rely on bile acid secretion, micelle formation, and fat absorption. In contrast, vitamin D3 is absorbed via intestinal lymph through an active process and generally depends on bile acid secretion, micelle formation, and fat absorption. This gives 25(OH)D3 distinct advantages over vitamin D3 because vitamin D3 absorption is impaired during malabsorption or intestinal disorders and/or the bioconversion of vitamin D3 to 25(OH)D3 is compromised when liver function is negatively affected by aflatoxins.
Table 1: Impact of 25(OH)D3 on production performance of broilers.
Young broilers need dietary 25(OH)D3
In young broilers, the blood circulating levels of 25(OH)D3 are low following hatch. This may be due to the poor absorption efficiency of vitamin D3. Young broilers secrete low levels of bile acids and inefficiently form micelles at the point of absorbing fat-soluble compounds. That low activity of hepatic 25-hydroxylase detected in young broilers may limit the conversion of vitamin D3 to 25(OH)D3. Thus, providing 25(OH)D3 in the young broiler diet eliminates the need of bile acid and micelle formation for absorption and conversion of vitamin D3 to 25(OH)D3 in the liver. Moreover, directly supplementing 25(OH)D3 could prevent the reduction in blood circulating 25(OH)D3 during the early part of broiler’s life.
25(OH)D3 supports bone health
Foraging behaviors post brooding predisposes broilers to subclinical enteritis, which is linked to malabsorption-associated skeletal disorders. Subclinical enteritis is usually undetected nor treated due to the absence of clinical signs or change in mortality rate. It causes poor growth, less feed efficiency, and a lack of flock uniformity. Furthermore, broilers with subclinical enteritis have impaired absorption of vitamin D3 as well as calcium and phosphorus. This translates to low blood circulating 25(OH)D3 levels and the development of skeletal disorders such as field rickets and angular deformities as broilers advance in age and body weight. Supplementing diets with 25(OH)D3 during the grow-out cycle, broilers maintain and sustain optimal blood circulating 25(OH)D3 level. This minimizes the incidence of skeletal disorders and post-enteritis leg breakdown.
25(OH)D3 promotes immunity
Promoting the fast development and maturation of the chick’s immune system after hatch is critically important for early health. Because of the “short” feeding period of broilers, activation of the innate immune system is very important for “inflammation” control and disease resistance during the “short” grow-out period. Nutritional interventions such as supplemental vitamin D in the form of 25(OH)D3 can effectively promote the development and maturity of the early immune system and enhance the formation of the innate immunity of broilers soonest possible.
25(OH)D3 boosts production performance
Supplementing broiler diets with 25(OH)D3 has been positively correlated with increased body weight, improved feed conversion, and higher breast meat yield (Table 1). Observations gathered from commercial operations show that broiler flocks fed with supplemental 25(OH)D3 produce better growth performance, livability, and body weight uniformity. Also, they have better animal welfare as they have less skeletal disorders. The commercial broiler production index is thus improved as evidenced indirectly by the reduction of whole bird condemns (i.e., whole bird condemns at the time of arrival at the slaughterhouse; Table 1).
It is also worth highlighting the years of research and field experiences across continents demonstrating a “significant and consistent” increase in breast meat yield by 1% of liveweight from broilers fed with supplemental 25(OH)D3. An increase in breast meat yield may be attributed to 25(OH)D3 by the rate of enhancing protein synthesis and promoting the activity of satellite cells in breast muscle. Satellite cells are a source of DNA, which is required when muscle fibers increase in size (hyperplasia) postnatally. Moreover, 25(OH)D3 may modulate the expression of specific genes linked to muscle development mediated by extra-renal 1-hydroxylase and vitamin D receptor.
25(OH)D3 boosts processing performance
Enhancing the immunocompetence of broilers may help bring down the rate of processing condemnation at slaughterhouses. Broilers fed with 25(OH)D3 experience less processing condemnations, which are due to cellulitis (inflammatory process) and airsacculitis (Table 2). Cellulitis is usually undetected until broilers are slaughtered and processed. It is characterized by discoloration and thickening of the skin and “inflammation” of the subcutaneous tissues. E. coli is the most frequent and abundant bacterium causing the cellulitis.
Broilers raised under conditions with poor ventilation and high ammonia content are at high risks of succumbing to airsacculitis. Airsacculitis is the “inflammation” of the mucus membrane of the air sacs of broilers. It is caused by bacteria such as E. coli and Mycoplasma spp.
Table 2: Impact of 25(OH)D3 on broiler processing performance.
Conclusion
The form of vitamin D must be considered when supplemented in broiler diets. In the end, the ability of vitamin D to fulfill all its biological functions depends on the ability of broilers to effectively absorb and maintain adequate and optimal levels of blood circulating 25(OH)D3. Because of its fast and efficient absorption and no requirement for bioconversion in the liver, 25(OH)D3 is the excellent choice of vitamin D for commercial broiler production. Supplementing broiler diets with 25(OH)D3 supports skeletal health, promotes immunity, boosts production and processing performance, and enhances animal welfare. In essence, 25(OH)D3 delivers stronger and healthier broilers and food safety.
*Dr. Thau Kiong Chung (thau-kiong.chung@ dsm.com), based in Singapore, is Manager, Special Nutrients (Hy-D), Greater Asia Pacific and Moises John Reyes (john.reyes@ dsm.com), based in The Philippines, is Manager, Special Nutrient Hy-D, Asia Pacific. Both are with DSM Nutritional Products Asia Pacific.