Effects of canthaxanthin and 25-hydroxycholecalciferol on the productive and reproductive performance of broiler breeders

In the poultry industry, productive and reproductive efficiency of broiler breeders are critical, since these two factors determine maximum economic returns from the numbers and quality of both hatching eggs and chicks produced per hen housed. The use of biotechnology-derived feed additives is primordial since they complement nutrition, resulting in increased productivity. Vitamin D₃, in the form of its metabolite 25-(OH)D₃, (25-hydroxycholecalciferol), can be involved in a better skeletal development, increased egg production, improved eggshells, and better reproduction, since this vitamin is directly involved in the metabolism of calcium (Ca) and phosphorus (P) (Smith et al., 2007). It is important to emphasize that vitamin D₃ is transmitted from the hen to the egg in the form of its metabolites 25-(OH)D₃ and 1,25-(OH)₂D₃ (Macari et al., 2005). The embryo also metabolizes vitamin D₃ present in the yolk sac, and uses it for de development of the skeleton (Rosa et al., 2009). The egg is known as one of the most complete foods that exist, since it is actually a nutrient-rich source. ln other words, the egg contains an excellent balance of fats, carbohydrates, minerals, vitamins and mainly proteins. Nevertheless, the egg is an ideal medium for the growth of pathogenic organisms and, being an animal-origin product - same as mead and meat derivatives - it is a highly perishable food that is prone to loose its quality quickly (Theron et al., 2003). This is why the search of an additive with the ability of improving hatching egg production and quality, is fundamental for improved broiler breeder performance.

Twenty five week-old Coob 500 broiler breeders (264 females and 24 males) were used. Birds were housed in 12 experimental units, in the Poultry Laboratory, Federal University of Santa María, Brazil. The animals were distributed at random observing uniform body weits at experiment start, to have 2 treatment groups (T) with 6 repetitions each. Isonutrient feeds were formulated as follows:  T1: control dieta (CD) based on corn and soybean meal; T2: CD + 1,000 g/ton^-1 MaxiChick^® (a patented product by DSM Nutritional Products Ltd, São Paulo, SP, Brazil, that includes 6,000 mg canthaxanthin/kg + 2,760,000 IU of 25-OHD₃/kg). Performance and incubation parameters were evaluated. Body weight (BW) was evaluated by weighing the entire lot on weeks 25, 28, 32, 36, 40, 44, 48 and 52 of age. In all other weeks samples of 50% of each lot were weighed. Laying rate was calculated by adding the total amount of eggs collected 6 times per day, and considering the number of birds in each repetition. Eggs collected from week 28 of age on were identified and selected as hatching eggs (malformation- dirt- crack-free) in order to evaluate egg mean weight and egg specific gravity as per the methodology recommended by Hamilton (1982) on a weekly basis. Afterwards, 3 eggs within a band of 2.5% of mean egg weight in the repetition, in order to determine the % weight of both albumin and yolk, in addition to egg yolk color using the DSM color fan, that includes the entire range from light yellow to dark orange, in a 1-15 scale. The chemical analysis of the eggs (3 egg yolks per repetition) was performed every 4 weeks by a 3rd-party lab, using the methodology recommended by Ohkawa et al. (1979), that analyses the levels of malondialdehyde (MDA) and thiobarbituric acid (TBA), resulting in a color complex that can be quantitated by spectrophotometry and the results are expressed in nmol MDA/mg protein. The higher the MDA level the higher the lipid peroxidation in the egg yolk. In the incubation experimental phase, approximately 24,000 eggs were used, that were disinfected with 37% formaldehyde + potassium permanganate vapors. Hatch occurred at 21 days of incubation. Good quality (abnormality-free; properly healed navels) chicks were weighed. Non hatched eggs were subjected to embryo diagnosis to calculate % mortality rates (M1 - 48 hours; M2 - 1st week; M3 - 2nd week, and M4 - 3rd week) and the percent rates of contaminated, pipped-non-hatched, and infertile eggs. All data was subjected to analysis of variance (ANOVA) using the SAS (2000) package.

The addition of MaxiChick® to broiler breeder diets had on affect on BW in the period from 25 to 52 weeks of age. No effects were seen of the treatments on % lay, egg specific gravity, egg weight or % hatching egg components (Table 1). Nonetheless, increased carotenoid deposition was seen in egg yolks from the breeders receiving the dietary canthaxanthin + 25-hydroxycholecalciferol combination, supposedly because of the presence of canthaxanthin in product. These results corroborate those reported by Rosa et al. (2009), whose 45-week-old breeders fed the same combination showed no effect on performance, but the egg yolk was more pigmented. Regarding incubation parameters (Table 2) using the product resulted in significantly increased hatch (P<0.0075), increased hatch of fertile (P<0.0237) and reduced embryo mortality % during the first 48 hours of incubation (P<0.0178) during the evaluation period. These results agree with those reported by Scher et al. (2009a) who found that using 25-OHD₃ associated to canthaxanthin resulted in higher total hatch and higher hatch of fertile, in addition to improve the fertility of broiler breeder roosters and reduce embryo mortality. The lipid peroxidation level was not reduced with the use of the product, which differs from the results published by Scher (2009b) when using canthaxanthin in the feed of broiler breeders at 45 weeks of age.

Table 1. % Lay and quality of hatching eggs

Table 2. Incubation parameters

The inclusion of the canthaxanthin - 25-hydroxycholecalciferol combination (MaxiChick^®) in the feed of the Cobb 500^® broiler breeders during the period from 25 to 52 weeks of age had no effect on bird productive performance or hatching egg quality. Nevertheless, such inclusion led to increased carotenoid deposition in the yolk sac, increased total hatch, and increased hatch of fertile. In addition, embryo mortality was reduced in the first 48 hours of incubation. All other parameters showed no effect of the treatments during the period evaluated.

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