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METABOLISM AND NUTRITION |
-OH Vitamin D3Department of Poultry Science, University of Georgia
1 Corresponding author: gpesti{at}uga.edu
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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–OH cholecalciferol (1-OH vitamin D3). Breeder age had significant effects (P = 0.0003) on 0 to 16 d chick growth (272 ± 7 vs. 339 ± 8 for 26- and 60-wk-old breeders, respectively) and chick mortality (P = 0.0134). The P rickets score increased with breeder age (P = 0.0186) and egg storage time (P = 0.1057). The factors influencing the incidence of P rickets in broilers should include breeder age and egg storage time as well as genetics and dietary levels of Ca, P, and vitamin D activity of the P-deficient diets.
Key Words: phosphorus deficiency • vitamin D • age • egg storage • broiler
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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The occurrence of TD as a spontaneously occurring cartilage abnormality in broiler chickens was first described by Leach and Nesheim (1965). Edwards (1984) stated that TD usually appears between 3 and 8 wk of age and is caused by a low level of dietary calcium and a high level of dietary phosphorus (Edwards, 1983). The bone lesion is characterized by an abnormal white, opaque, unmineralized, and unvascularized mass of cartilage occurring in the proximal end of the tibia (Farquharson and Jefferies, 2000). The abnormal cartilage is irregular in shape and size. There is also a persistence of prehypertrophic cartilage that is not calcified and has not been invaded by vessels from the metaphysis below the growth plate (Riddell, 1975; Edwards, 1984).
Another bone abnormality that sometimes occurs in commercial flocks is rickets, which is a disease of the young birds and animals characterized by continued growth of cartilage and failure of mineralization and calcification of cartilage (Jubb and Kennedy, 1970). It is generally considered to be the result of an imbalance of vitamin D3, calcium, and phosphorus or a deficiency of one of these nutrients. Itakura et al. (1979) provided a detailed description of an outbreak of rickets. Bones were soft, but cortical bone was thickened with narrowing of the marrow cavity. There are 2 types of rickets: hypocalcemic rickets (calcium deficiency) is characterized by an accumulation of proliferating cartilage, and hypophosphatemic (phosphorus deficiency) rickets in which the hypertrophic cartilage accumulate with normal metaphyseal vessel invasion (Lacey and Huffer, 1982).
There is variation in phytate phosphorus (PP) utilization between broilers of the same strain related to growth, livability, and skeletal strength (Punna and Roland, 1999). They conducted an experiment with cornsoybean diets with 0.95% Ca and 0.5% available P (aP), and collected feces after the second and fourth weeks revealed that those birds which demonstrated normal growth, no leg problems and no visible signs of a phosphorus deficiency were able to utilize phosphorus far more efficiently than birds which did display problems. Even PP utilization within single strains of chickens had differences (Carlos and Edwards, 1998; Zhang et al., 1998; Smith et al., 2001).
Driver et al. (2006) observed a decrease in progeny TD from 85 to 24% as one flock of breeders aged from 39 to 64 wk. Shim et al. (2006) confirmed the breeder age effect with broilers raised at the same time from breeders of different ages.
Egg storage time influences both the score and incidence of P deficiency-rickets in the progeny (Shim et al., 2006). When eggs were stored for 10 d, young chicks tended to have lower rickets scores and incidence of P-rickets than when the eggs had not been stored. Bone ash was affected by diet, breeder age, and egg storage time (3-way interaction; Shim et al., 2006). Egg storage time had its biggest effect on bone ash with chicks from older breeders given a P rickets-inducing diet. Bone ash was higher in chicks from young breeders on all diets except the P rickets-inducing diet, in which bone ash was higher in chicks from the older breeders. The common factor between breeder age, egg storage time, and diet seems to be reducing bone ash that leads to P rickets.
Vitamin D and several of its carbon-1, hydroxylated derivatives have been shown to improve PP and total P (tP) uptake in chicks. The mechanisms by which this occurs are as yet unclear; however, several theories have been suggested. Harrison and Harrison (1961) proposed that vitamin D stimulates a Ca-dependent P pump in cells lining the intestine by increasing the Ca content of these cells. There is also evidence that suggests that vitamin D acts as a P transport hormone stimulating P transport in many tissues in the body including the intestine (Tanaka and DeLuca, 1974). Cross and Peterlik (1988) and Sechman et al. (1996) concluded that the presence of high plasma 1,25-(OH)2D3 increases the number of Na-P transport proteins within the intestine of the chick.
Vitamin D and its derivatives may also increase P absorption simply by increasing Ca absorption. Less Ca increases the proportion of soluble P in contact with the gut mucosa as Ca forms the Ca2PO4 salt at the normal intestinal pH (Hurwitz and Bar, 1971). Phosphates in this insoluble state are unavailable for absorption.
The significant improvement in PP retention obtained with dietary 1,25-(OH)2D3 and 1-OH vitamin D3 is consistently achieved when either is fed to modern fast-growing chicks (Edwards, 1993; Roberson and Edwards, 1994; Biehl et al., 1995; Elliot et al., 1995; Mitchell and Edwards, 1996; Biehl and Baker, 1997).
The experiments reported here were conducted to test the hypotheses that 1) breeder age and egg storage can also affect the incidence of P rickets, and 2) 1-OH vitamin D3 may overcome the negative impacts of young breeders and egg storage time.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Eggs obtained from a commercial breeder company were stored at 12°C and 66% relative humidity for 0 or 10 d and warmed at room temperature (20°C) 12 h before setting. Each egg was individually marked with date of lay. All eggs were collected the morning they were laid, eggs not stored were placed in egg trays at room temperature (20°C) for 12 h overnight before they were placed in the incubator. Eggs were set at 37.7°C and 55% RH in a single-stage NatureForm NMC-2000, 1,980 egg capacity setter (NatureForms Hatchery System Inc., Jacksonville, FL) with automatic temperature regulation (accurate to 0.10°C), relative humidity (accurate to ±2% relative humidity), and an automatic turning system (24 times/d).
The chicks were housed in Petersime wire-floored battery brooders for 16 d and were provided with water and the dietary treatments ad libitum. At the conclusion of each experiment, birds were weighed and killed by asphyxiation using carbon dioxide. Body weight and feed intakes were measured from 0 to 16 d and body weight gain (BWG) and feed conversion ratio (FCR) were calculated. Left tibias from all chicks were collected on d 16 for percentage tibia ash determination on a fat free dry-weight basis (Association of Official Analytical Chemists, 1995), whereas right tibias were sliced and scored for the severity of bone abnormalities including P rickets as described by Edwards and Veltmann (1983).
Experiment 1
Eggs were laid by Ross x Ross 308 breeders. Two hundred seventy eggs from each of the 4 breeder treatments (26-wk-old stored, 27-wk-old fresh, 60-wk-old stored, and 61-wk-old fresh) were incubated. On d 11, eggs were candled, and all eggs with no live embryos were removed. On d 18, eggs were transferred into hatcher baskets and placed into the hatcher at 36.7 to 36.9°C and 70% relative humidity. Twelve replicates pens of 5 chicks from each breeder age and egg storage time combination were placed in each of 48 pens. The progeny were fed 2 cornsoybean based diets (control vs. P-deficient diet; Table 1
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Eggs were laid by 25 wk old (stored), 26 wk old (fresh), 59 wk old (stored), and 60 wk old (fresh) Ross x Ross 308 breeders. Two hundred seventy eggs from each of 4 treatments were incubated. On d 14, eggs were candled, and all eggs without live embryos were removed. On d 19, eggs were transferred into hatcher baskets and placed into the hatchery as above. Twelve replicates pens of 10 chicks from each breeder age and egg storage time combination were placed in each of 48 pens. The progeny were fed a diet based on corn, soybean meal, and soybean oil with or without 5 µg/g of 1-OH vitamin D3 (Table 1
). Feed and excreta samples were analyzed for phytate P (Latta and Eskin, 1980) and chromic oxide (Brisson, 1956). Phytate P retention was calculated using the methods of Edwards and Gillis (1959).
Statistical Analysis
The ANOVA was performed on all data for both experiments using the general linear model procedure of SAS (version 8.02, 2001) appropriate for a randomized block design. Treatment means were separated using Duncan’s multiple range test at P < 0.05 (Duncan, 1955) and orthogonal contrasts.
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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and 3). Day-old chick weights were different (P = 0.0934, P < 0.0001) due to breeder age in both experiments. Chicks from the younger breeders were smaller when the eggs were stored for 10 d in experiment 1 but not experiment 2. Breeder age effects were significant for day-old chicks and for 16-d-old chicks in experiment 2. Because of variation, the 38-g difference in 16-d weights was not significant at P < 0.05 in experiment 1, but a 33-g difference was significant in experiment 2.
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). The P-deficient diet decreased BWG (418 ± 14 vs. 270 ± 13 for control and P-deficient diets, respectively) in experiment 1 (Table 4).
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). The longer egg storage time of chicks from older breeders resulted in higher P rickets scores and incidences, but the longer egg storage time of chicks from younger breeders resulted in lower P rickets score and incidences when chicks were fed the P-deficient diet (interaction P = 0.0455; Table 5).
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-OH vitamin D3 increased 16-d BWG by 30.5 g for chicks from older breeders, but only 15.0 g for chicks from younger breeders (P = 0.0348; experiment 2; Table 6). The P-deficient diet with 1-OH vitamin D3 increased BWG, bone ash, and phytate P retention in experiment 2 (Tables 6 and 7). The P-deficient diet with 1-OH vitamin D3 also decreased the score and incidence of P rickets and chick mortality. Breeder age decreased P rickets score and incidence (Table 7). The chicks from the older breeders showed higher P rickets scores (P = 0.0186) and incidence (P = 0.1135).
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-OH vitamin D3 had significant effects on 0 to 16 d chick mortality (4.58 ± 1.34 vs. 17.50 ± 3.52; P = 0.0005). Breeder age also had significant effects on 0 to 16 d chick mortality (15.83 ± 3.71 vs. 6.25 ± 1.45 for 26- and 60-wk-old breeders, respectively; P = 0.0071). Mortality of chicks from eggs with 10 d storage was higher (12.92 ± 2.98) than those from fresh eggs (9.17 ± 2.94), P = 0.0134. |
DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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In experiment 1, egg size was increasing rapidly so that the chick weights from the 26-wk-old breeders whose eggs had been stored for 10 d were considerably smaller than chicks from the 27-wk-old breeders that had not been stored. The fertility of this flock was also increasing rapidly, from 36 to 77% over the 10-d storage period. In contrast, in experiment 2, chick weights were very similar and actually slightly smaller for the 26-wk-old breeders and no egg storage than those from the 25-wk-old breeders with 10-d storage. Fertility in this flock was higher than from the slightly older flock in experiment 1. Fertility increased from 58 to 90% over the 10-d storage period. Therefore, although these flocks were raised under identical protocols, there are differences in their performance that may influence the results of progeny trials. Experiment 1 was conducted in the fall, and experiment 2 was conducted in the spring. In the spring, male chickens were stimulated sooner and their fertility was higher. The weather might be a complicating factor that changes chicks’ performance. Changes in environmental temperature quickly affect egg production and egg size.
The significant improvement in PP retention obtained with dietary 1,25-(OH)2D3 and 1-OH vitamin D3 is consistently achieved when either is fed to modern fast growing chicks (Edwards, 1993; Roberson and Edwards, 1994; Biehl et al., 1995; Elliot et al., 1995; Mitchell and Edwards, 1996; Biehl and Baker, 1997), which would have increased the amount of P available to chicks. Experiment 2 demonstrates that 1-OH vitamin D3 does affect PP retention in chicks because the breeder genotypes and rearing protocols were identical and chicks were raised under identical conditions. The P-deficient diet with 1-OH vitamin D3 decreased the score and incidence of P rickets, which is usually associated with increased PP retention in chicks. Thus the increase in P rickets from older breeders and egg storage does not appear to be due to a lack of vitamin D or lack of an active hydroxylated vitamin D hormonal form.
Percentage hatch from very young breeders (26 wk of age) was slightly higher than breeder company expectations. However, percentage hatch from young breeders (27 wk of age) and old breeders (60 and 61 wk of age) were lower than breeder company expectations (Ross x Ross Management Guide, Aviagen, Huntsville, AL), and lower than observations by Wineland and Brake (1984). In experiment 1, fertility was increased from 77.41 to 79.26% when breeder age increased (from 27 wk to 61 wk old) although these were different flocks. In experiment 2, fertility decreased from 89.64 to 79.64% with increasing breeder age (from 26 wk to 60 wk old), although again these were different flocks. The HES was approximately 6 to 8% lower than fertility in both experiments.
The effect of storage time on P rickets incidence was opposite in young versus old breeders, emphasizing the complex nature of the interactions among the causes or contributors of P-deficiency rickets. The differences may have been due to the increased growth rate potential of chicks from the different sizes of eggs. There was a strong relationship between growth rate and the incidence of P-deficiency rickets in the chicks from eggs that were stored, but not when the eggs were set shortly after production (Figure 1). This suggests that whatever factors affect growth rate will affect P-deficiency rickets, at least when the eggs are stored.
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Petek and Dikmen (2004) conducted experiments with 2 quail breeder ages (20 vs. 37 wk) and 2 egg storage times (5 vs. 15 d). They had significantly lower chick mortality (6.74 to 8.29%) in their study that could be declared significant because the variation between replicates was low. Chick mortality in experiment 1 and 2 from 3.3 to 19.2% could not be declared significantly different by age of broiler breeders or egg storage.
In experiment 2 (Table 3), breeder age had significant effects on 0- to 16-d chick growth confirming the findings of other studies that the progeny from older breeders had higher growth than the progeny from young breeders (Whiting and Pesti, 1982; Reis et al., 1997).
Vitamin D3 supplementation of breeders might have influenced egg and chick parameters in experiment 2. Bethke et al. (1936) found that the level of vitamin D3 in the breeder diet influenced chick weight and bone calcification at 5 wk of age when fed a rachitic diet. Stadelman et al. (1950) and Stevens et al. (1984) have since shown that growth and calcification in turkey poults fed a vitamin D3-free diet was directly proportional to the vitamin D3 level in the diet of breeders during the first 4 wk. Griminger (1966) reported that chicks from broiler breeders fed different levels of vitamin D3 showed no differences in weight after 1 wk of age. However, vitamin D3 might also have an important role to prevent defects causing field rickets in poultry (Olson et al., 1981; Bar et al., 1987). The BWG, bone ash, and incidence of rickets might be changed by different sources of vitamin D3 (Kasim and Edwards, 2000).
These studies confirm and extend those of Driver et al. (2006) and Shim et al. (2006). Not only is the age of the breeders important in determining the incidence of TD in the progeny (Driver et al., 2006), but also the appearance of P rickets (Tables 4, 5, and 7). Clearly, it is important to know the age of the breeders as well as their vitamin D3 status whenever factors affecting the leg health of broilers are studied. To maximize broiler performance, Ca and P requirements and their interactions need to be investigated with chicks from young and old breeders. Although egg storage time can be demonstrated to be a significant contributor to P deficiency in broilers, the magnitude of the effects is relatively small, even when extremes like 0 and 10 d of egg storage are compared (Tables 4, 5, and 7). These results suggest that the P requirements of broiler chickens may be different for progeny of young and older (at least post-peak) breeders. When other factors predispose broilers to leg problems, the progeny of younger hens may be particularly susceptible.
The conclusion of the effects of breeder age and egg storage time only applies to P-deficient birds. Whenever phosphorus prices are high, marginal levels are fed. These findings may be important for the half of birds receiving below average phosphorus levels and especially for the approximately 16% of birds receiving phosphorus levels more than 1 standard deviation below the mean.
Received for publication September 11, 2007. Accepted for publication February 23, 2008.
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