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Carotenoids are a diverse group of fat-soluble pigments that influence antioxidant status and immunity. Studies investigating the effect of carotenoid pigments on immune function indices in chicks are few, and most focus on the effects beyond the first week of life. The objectives of this research were 3-fold: To determine the effect of maternal CXN supplementation on indices of chick early innate immune function; to determine the effect of hen age on chick early innate immune response; and to determine how indices of innate immune response change with chick and hen age. It was hypothesized that chicks from hens supplemented with CXN would have a more robust innate immune response than chicks from non-supplemented hens and further that a higher level of CXN supplementation would increase the robustness of the innate immune response in chicks. Second, chicks from older hens would have a more robust innate immune response than chicks from younger hens; and third, that the innate immune response of chicks would increase as chicks aged. To assess the rate of incorporation of dietary CXN into eggs, Single-comb White Leghorn hens were fed the same levels of CXN. Egg levels of CXN were measured over a 40-day period to model the rate of incorporation in hatching eggs.
Experiment 1: Ross 308 broiler breeder hens were managed to maintain growth curves as recommended by Ross 308 Breeder Performance Objectives until 21 weeks of age, at which point they were transferred to individual cages. Photostimulation and dietary treatments (n = 45 hens per treatment) were initiated at 22 weeks of age. They were fed a standard commercial-type broiler breeder basal diet supplemented with either 0 (Control), 6 (Low), or 12 (High) mg of CXN per kg of diet. Analyzed dietary values of egg CXN were 0, 7.62 and 15.84 mg CXN per kg diet for the respective treatments. Individual BW were determined weekly and averaged within treatment. Egg production was recorded daily, production was calculated for Early (23 to 33 wk); Mid (34 to 47 wk); and Late (48 to 61 wk) production periods. At three hen ages (Early, 31 to 33; Mid, 45 to 47; and Late, 57 to 59 wk of age), each hen was artificially inseminated with 0.5 mL of pooled semen from Ross 308 roosters fed the Control diet. The settable eggs were stored and then placed in an incubator at weekly intervals. Fertility as a percent of settable eggs placed and the % hatch of fertile were determined within a treatment for each egg placement. The chicks were weighed and feather-sexed at hatch. Ten eggs per treatment at each egg placement were sampled to determine whole egg, yolk, and albumen weights. Plasma was collected from 15 hens per treatment at each hen age and stored at −20°C for subsequent total antioxidant capacity determination. After hatching, 24 male chicks per maternal treatment from the first hatch within each breeder age were placed in Petersime battery brooders for determination of innate immune function. At each of one and four days of age, 12 chicks from each maternal treatment were weighed and bled via decapitation. The whole blood from 8 chicks/maternal treatment was used for the innate immune function assays. Male chicks were separated by maternal treatment and placed in Specht cages for a 3-week grow-out trial. Ten female chicks per maternal treatment were weighed, bled, and dissected for liver collection at each of 0, 7, 14, and 21 days of age. Egg, liver and feed CXN were evaluated.
Experiment 2: Single-comb White Leghorn laying hens, 44 weeks of age, were individually housed in battery cages and were fed a nutritionally complete, commercial-type laying hen diet containing either 0 mg/kg CXN (Control), Low (6 mg/kg feed) CXN, or High (12 mg/kg feed) CXN (n = 14 hens/treatment). Feed and water were available ad libitum. Egg samples were taken at days 0, 2, 4, 7, 9, 11, 14, 18, 21, 25, 28, 35, and 40 to determine the kinetics of maternal dietary CXN incorporation into eggs. Whole egg and combined albumen and yolk weights were recorded. Yolk and albumen were homogenized together and a sample was weighed and kept for analysis of CXN content via HPLC. Samples were frozen at −20°C until HPLC analysis.
Hen BW increased as hens aged, and was slightly depressed by CXN across hen ages. Total egg production was lower during the Late production period and was greater for the Control and Low hens relative to the High hens. Fertility was affected by neither hen age nor the interaction of hen age and dietary treatment. Hatchability of fertile eggs was not affected by maternal CXN supplementation. Calculated chick yield was greater for the Low CXN hens than for the Control and High CXN treatments (P < 0.001). Among the Early hens, the Low male chick hatch weights were not different from the Control chicks, but were lower than for the High chicks (P < 0.004). There were no treatment differences during the Early production phase for female chick hatch weight. At the Mid and Late breeder phases, chicks from the Low hens had lower hatch weight than chicks from the other two maternal dietary treatments. Canthaxanthin supplementation did not affect egg traits. Higher levels of dietary supplementation resulted in greater amounts of CXN being deposited into the egg in Experiment 1, but breeder hen age did not affect egg CXN deposition. In Experiment 2, the deposition rate of CXN into eggs by Single-comb White Leghorn (SCWL) hens reflected the level of dietary supplementation, and by 7 days of supplementation, very little further increase in egg CXN was observed. Similar to Experiment 1, doubling the dietary level of CXN resulted in an approximately 20% greater transfer of CXN to the egg. Egg CXN content increased with increasing maternal supplementation level, however the increased availability of CXN to the embryo did not result in a greater innate response, as chicks from Low hens had greater EBC relative to Control and High chicks. Hen dietary CXN did not affect chick BW or gain. CXN was not detected in the liver of chicks at hatch from Control hens at any hen age, but in both the Low and High treatment groups, there was a decline in chick liver CXN at hatch from Early- to Mid-aged hen ages, with no further decline thereafter.
Hen dietary CXN decreased hen BW, although the Low diet increased settable egg production and as hypothesized, the higher level of supplementation resulted in a greater amount of CXN being deposited into the egg and chick liver. Hen plasma total antioxidant capacity was not affected by CXN supplementation nor did it affect hatchability, or chick performance. As hypothesized, chicks from hens supplemented with 6 mg CXN/kg diet had a more robust early innate immune response than chicks from non-supplemented hens. However, increasing maternal diet CXN to 12 mg/kg diet did not further increase chick innate immune function as chicks from Low hens had the greatest EBC and d 1 OB. Chick d 0 plasma total antioxidant capacity increased with increasing dietary level of CXN in chicks from Mid and Late hens. The profile of chick plasma total antioxidant capacity as chicks aged differed by hen age and treatment, but the reason why is unclear. The current data support that CXN is immuno-modulatory and suggest that hen age affects chick innate immune function and chick plasma total antioxidant capacity.