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Effect of Maternal and Dietary 25-OH Vitamin D3 on Broiler Production and Immunity

by 5m Editor
25 February 2010, at 12:00am

The effects of maternal and dietary 25-OH vitamin D3 (25OHD) on chick immunity and growth were determined. Embryonic mortality was lower in the 25OHD maternal treatment than in the vitamin D3 (D3) treatment. Broiler BW was improved for the broilers fed 25OHD. In vitro chick leukocyte E. coli killing capability was improved with maternal 25OHD. In vitro E. coli killing was increased from immune cell of chicks on maternal and dietary 25OHD. Both maternal and dietary 25-OH D3 improved aspects of broiler production and immune function.

J.L. Saunders-Blades and D.R. Korver

I. INTRODUCTION

Vitamin D and its metabolites are required for growth, health and bone development in the chick. The natural hepatic production of 25OHD can become impaired, either due to stress such as infection or mycotoxin feed toxicity (Waldenstedt, 2006) or perhaps due to immaturity of enzyme development required for vitamin D absorption in the young chick (Ward, 2004). Providing maternal or dietary 25-OH D3 to the chick may allow more ready conversion to 1,25(OH)2D3 and therefore may enhance the functions that vitamin D metabolites serve within the body. Previous studies have shown dietary 25OHD to increase BW (Yarger et al., 1995; Mitchell et al., 1997; Aburto et al. , 1998), improve feed conversion efficiency and increase breast muscle yield (Yarger et a l., 1995) in broilers in comparison with D3.

Some reports indicate that selection for fast growth rates of commercial broilers and turkeys has had a negative impact on the immune response, making modern birds more susceptible to infections than in the past (Bayyari et al., 1997; Yunis et al., 2000). Vitamin D has been shown to be involved in various aspects of the immune system in humans and other species (Gray and Cohen, 1985; Reinhardt and Hustmyer, 1987) but its potential function within the chicken has not been well studied.

We have previously shown that 25OHD improved broiler production efficiency and bone quality, and that maternal supplementation improved hatchability and chick early innate immune function (unpublished data). The objectives to the current research were to investigate the potential effects of maternal dietary 25OHD on hatchability as well as maternal and direct dietary supplementation of 25OHD on broiler production and ex vivo innate immune function of the progeny. We hypothesized that maternal 25OHD would support normal broiler breeder production, as well as lead to a more mature innate immune system of the chicks at hatch. In addition, we hypothesized that dietary supplementation of 25OHD would improve broiler production traits.

II. MATERIALS AND METHODS

(a) Experimental diets
Wheat-based basal maternal diets devoid of supplemental vitamin D were formulated for each breeder phase to meet or exceed current primary breeder and NRC (National Research Council, 1994) recommendations. Each basal diet was subdivided and supplemented with either 2,760 IU of dietary vitamin D3 per kg of feed or 69 µg of dietary 25-OH D3 (Rovimix D3 500® or Rovimix HyD® equivalent to 2,760 IU of vitamin D3 activity, respectively. DSM Nutritional Products Inc., Parsippany, NJ; per kg of feed, was used as the sole source of supplemental vitamin D activity.

(b) Experimental design and data collection
At 23 wk of age, Cobb 500 broiler breeder hens (n=200) were randomly allocated to four floor pens (50 birds per pen; two pens per treatment). In addition, five Ross 308 male broiler breeders were placed in each pen. Birds were weighed and feed allocation adjusted on a weekly basis (separate for males in females) for the average BW of the four pens to maintain the breeder-recommended BW curve. At broiler breeders ages of 31 to 33 weeks (Early), 46 to 48 weeks (Mid) and 61 to 63 weeks (Late), eggs were collected for incubation and hatching. Two complement hatches were done at each broiler breeder age. At hatch, embryonic mortality, hatchability and chick BW were assessed for each maternal dietary treatment group.

(c) Broiler innate immune function and production traits
At hatch, chicks were separated based on maternal treatment, and further separated in two additional dietary treatments, resulting in four broiler treatments: Maternal D3 + Dietary D3 (DD); Maternal D3+ Dietary 25OHD (DH); Maternal 25OHD+Dietary D3 (HD); and Maternal 25OHD+Dietary 25OHD (HH). For one hatch, chicks were place in battery cages and assessed at one and four d post -hatch (n=10 chicks per treatment) were assessed for in-vitro innate immune function. White blood cells phagocytosis of fluorescen tly- labe led E. coli was analyzed (Millet et al., 2007), with modifications to allow analysis by flow cytometry. Oxidative burst was measured using a modified version of that given by He et al., (2003) for analysis by flow cytometry. White blood cell bactericidal (E. coli ) capability was measured (Millet et al., 2007). At two weeks of age, five birds per pen were injected intraperitoneally with 3 ml of a 100 µg/ml solution of Salmonella typhimurium lipopolysaccharide (LPS) to simulate an infectious challenge (Korver et al., 1998). Within each pen, five additional chicks were chosen at random to serve as noninjected controls. At 24-hr post-hatch, 10 injected and 10 control birds per treatment were assessed for in-vitro bactericidal capability after an inflammatory immune challenge. For the other hatch per breeder age, chicks were placed in floor pens (four per treatment), assessed for innate immune function as described previously at 1 and 4 d post-hatch as well as for production traits to slaughter weight. Chicks from the Early hatch received a starter ration (0 to 14 d), a grower ration (15 to 27 d) and a finisher ration (28 to 39 d). For the Mid and Late hatches, chicks were fed starter (0 to 10 d), grower (11 to 28 d) and finisher (29 to 41 d) phases. BW on a pen basis was obtained and feed consumption measured for the starter, grower and finisher phases. Mortality-corrected feed conversion ratios (FCR; g feed/g gain) were calculated.

(d) Statistics
Broiler breeder and hatching egg data were analyzed as a one-way ANOVA with diet as the main effect using the Proc Mixed procedure (SAS Institute, 1999). Broiler data were analyzed as a 2 X 2 factorial with maternal and dietary treatments as the main effects using the Proc Mixed procedure (SAS Institute, 1999). Means were separated using the LSmeans procedure (SAS Institute, 1999); significance was assessed at P<0.05.

III. RESULTS AND DISCUSSION

(a) Hatchability and broiler production traits
There were no differences in hatch of fertile eggs at any breeder age. Hatchability was on average 92.6, 91.7 and 85.8 % for the Early, Mid and Late hatches respectively. For the Late hatch, the 25OHD breeder treatment group had lower mid (8 to 14 d) embryonic mortality in the vitamin D3 breeder treatment group (0.67% versus 2.80%, respectively). Chick BW was greater for chicks from 25OHD fed breeders for the Early hatch, however the opposite was found for the Mid and Late hatches. Overall, dietary 25OHD yielded the same hatchability with little difference in embryonic mortality except for the late hatch in which it reduced embryonic mortality. We have previously found that 25OHD significantly reduced embryonic mortality (unpublished data), although the replication was much greater in that study. There were no maternal treatment effects on broiler production traits for the Early hatch, however dietary 25OHD supplementation resulted in greater broiler BW at 21, 27 and 39 d of age. The broilers fed 25OHD tended to eat more feed (significant only for the two weeks feed consumption), but there were no differences in FCR. For the Mid hatch, there were no differences in broiler BW, gain or feed consumption for either the maternal or broiler dietary treatments. However, the maternal vitamin D3 treatment group had lower FCR for the finisher period than the maternal 25-OH D3 broilers (1.88 vs 1.94, respectively). For the Late hatch, a nearly significant interaction of maternal and dietary treatment for 10 d BW (P=0.054) and gain (P=0.060) for the starter period. There was an interaction of maternal and dietary treatments in which dietary 25OHD reduced starter period FCR in chicks from the 25OHD maternal treatment but not from the D3 maternal treatment (P=0.038). Dietary 25-OH D3 resulted in increased broiler BW, although with increased feed consumption for the Early hatch. The improved FCR during the starter period of the Late hatch may have improved overall production efficiency for those birds.

(b) Innate immune function
There were no broiler diet effects on innate immune cell killing of E. coli at either 1 or 4 d post hatch for the Early, Mid or Late hatches. However, broiler innate immune cell killing of E. coli at 1 d post-hatch for the Early hatch was greater in those chicks from the 25OHD fed breeders (56.1 vs 41.2%, respectively) but not different at 4 d post-hatch. For the Mid hatch, killing of E. coli by immune cells from 25OHD chicks was not different at 1 d post-hatch, but was nearly greater (P=0.063) than the D3 treatment at 4 d post-hatch (32.36 vs 26.36 %, respectively). There were no maternal treatment effects on immune cell killing of E. coli for the Late hatch. After injection with LPS at 2 wk of age, there was no maternal treatment or dietary effects on immune cell E. coli killing for the Mid hatch. However, for the Late hatch, the LPS-injected HH birds had a greater amount of E. coli killing (29.6%), than the LPS injected DD (12.0%) and DH (10.3%) birds; none were different than the HD LPS injected birds (23.4%). These results suggest an improvement in the maturation of the innate immune cell killing capability in young chicks when the hens receive dietary 25OHD. During an inflammatory response, birds from th e maternal 25OHD that received dietary 25OHD had among the highest of killing capability.

IV. CONCLUSION

Both maternal and dietary 25OHD improved aspects of broiler production and innate immune function at all 3 broiler breeder ages. Maternal supplementation decreased embryonic mortality in the Late hatch, and improved early innate immune function of the progeny. Dietary supplementation of 25OHD improved certain aspects of broiler production for the Early and Mid hatches. Therefore 25OHD may be a nutritional means to enhance immune function of poultry without compromising production traits.

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