Performance, Body Temperature and Egg Quality of Laying Hens Fed Vitamins D and C Under Three Environmental Temperatures

Desempenho, Temperatura Corporal e Qualidade dos Ovos de Poedeiras Alimentadas com Vitaminas D e C em Três Temperaturas Ambiente

Desempenho, Temperatura Corporal e Qualidade dos Ovos de Poedeiras Alimentadas com Vitaminas D e C em Três Temperaturas Ambiente

Performance, Body Temperature and Egg Quality of Laying Hens Fed Vitamins D and C Under Three Environmental Temperatures

Autor(es) / Author(s)

FariaDE¹

JunqueiraOM²

SouzaPA²

TittoEAL¹

1-Depto. de Zootecnia da FZEA/USP - Pirassununga

2- FCAV/UNESP – Jaboticabal – SP

Correspondência / Mail Adress

Douglas Emygdio de Faria

Depto. de Zootecnia da FZEA/USP

Av. Duque de Caxias Norte, 225

13630-000 - Pirassununga - SP - Brasil

E-mail: [e-mail]

Unitermos / Keywords:

ácido ascórbico, colecalciferol, estresse calórico,

ovos, poedeiras

ascorbic acid, cholecalciferol, egg, heat stress,

laying hens

Observações / Notes

The authors wish to acknowledge the financial

support of Fundação de Amparo à Pesquisa do

Estado de São Paulo (FAPESP).

RESUMO

O experimento foi conduzido em câmara climática para determinar os efeitos das vitaminas D₃ e C sobre o desempenho, temperatura corporal e qualidade dos ovos de poedeiras em três temperaturas: termoneutra (24,8^º a 27,0º C), estresse calórico cíclico (26,2º C por 16h e 32,1º C por 8h) e estresse calórico constante (30,0^º a 32,0º C). Foram utilizadas 144 galinhas brancas com 31 semanas num delineamento inteiramente ao acaso em arranjo fatorial 3x3x3: vitamina D₃ (2500, 3000 e 3500 UI/kg), vitamina C (0, 200 e 400 ppm) e temperatura ambiente (termoneutra, estresse calórico cíclico e constante). As características avaliadas foram: consumo de ração (CR), produção de ovos (PO), peso dos ovos (PE), massa de ovos (MO), conversão alimentar (CA), porcentagens de albúmem (AL) e de gema (GE), unidade Haugh (UH), índice de gema (IG), porcentagem de casca (PC), espessura de casca (EC), gravidade específica dos ovos (GO), temperaturas dorsal (TD) e retal (TR). A vitamina D₃ interferiu nas características PC, EC, GO e TD; a vitamina C no IG, PC e GO. A temperatura ambiente não afetou somente a UH. Concluiu-se que níveis mais altos de vitamina D₃ e níveis de 200 ou 400 ppm de vitamina C na dieta podem melhorar a qualidade da casca e que o estresse calórico prejudicou as principais características avaliadas.

ABSTRACT

Three experiments were conducted in a climatic chamber to determine the effects of vitamins D₃ and C supplementation on performance, body temperature, and egg quality under thermoneutral temperature (24.8 ^º to 27.0^º C), a cyclic heat stress (26.2^º C for 16 h and 32.1^º C for 8 h) and a constant heat stress (30.0^º to 32.0^º C) for three weeks in each temperature. One hundred forty-four White Leghorn hens aged 31 weeks were used in a completely randomized design with a factorial arrangement of 3 x 3: vitamin D₃ (2,500, 3,000, and 3,500 IU/kg) and vitamin C (0, 200, and 400 ppm), with a total of nine treatments with four replicates of four hens each. Parameters measured included feed intake (FI), feed:gain (FG), egg production (EP), egg weight (EW), egg mass (EM), rectal (RT) and dorsal temperatures (DT), percentages of albumen (AP) and yolk (YP), Haugh units (HU), yolk index (YI), shell percent (SP), shell thickness (ST) and egg specific gravity (ESG). Vitamin D₃ influenced the parameters SP, ST, ESG and DT; vitamin C influenced YI, SP and ESG. There was no influence of environmental temperature only on HU. It was concluded that higher levels of vitamin D₃ and 200 or 400 ppm of vitamin C can be improve eggshell quality and that heat stress impaired the main characteristics evaluated.

INTRODUCTION

For layers, the main consequences of heat stress are a reduction in feed intake, a decrease in intestinal blood flow and ionized calcium levels in blood, a reduction in partial pressure of carbon dioxide (pCO₂) and an interference in GnRH action, the hypothalamic hormone that regulates the release of luteinizing hormone (El Hadi & Sykes, 1982; Bahr, 1995; Harrison, 1995). The effects of heat stress on performance parameters, internal and external egg quality were also studied by Leeson (1986), Willians (1992) and Sakomura et al. (1993).

According to Scott et al. (1982) vitamin C is required only for humans, other primates, guinea pigs and fishes, and the majority of other species synthesize it in adequate quantities. Thus, dietary necessity may be limited to some species but the metabolic necessity is general (McDowell, 1989). The inclusion of vitamin C in chicken feed generally is not necessary according to North & Bell (1993). NRC (1994) did not establish the level of supplementation but suggested that there would be a favorable response in chickens that were under stress.

In a review paper, Pardue & Thaxton (1986) commented that many stressing agents altered either the use or the synthesis of ascorbic acid by the chickens. Under non-stressing environmental conditions, Benabdeljelil et al. (1990) established that ascorbic acid had little practical value for brown layers. Krautmann et al. (1990) provided many recommendations of vitamin C supplementation in the feed or in drinking water when the chickens were submitted to chronic and acute stresses. Orban et al. (1993) reported that the egg weight was increased up to 5% and specific gravity was improved when vitamin C supplementation was 2,000 or 3,000 ppm. Volker & Weiser (1993) studied the interaction of vitamin C and vitamin D₃ on bone metabolism in laying hens from 71 to 84 weeks of age, and suggested that an adequate level of vitamin C is needed for efficient hydroxylation of vitamin D to its active form, 1,25(OH)₂D₃. Levels above 200 ppm of ascorbic acid were shown to promote an increase in egg production, egg weight, egg specific gravity and decrease of the cracked eggs (Zapata & Gernat, 1995; Gardini, 1996).

Cholecalciferol (Vitamin D₃) is important for adequate calcium and phosphorus metabolism and for the development of bones, beaks, legs and eggshell (Scott et al., 1982; McDowell, 1989; De Blas & Mateos, 1991). The dietary supplementation of vitamin D is not required when there is enough sunlight (McDowell, 1989). However, the poultry industry is characterized by intensive production systems and birds are kept in covered facilities, protected from direct sunlight. Literature values for dietary supplementation levels of vitamin D vary widely. Suggested levels of vitamin D are 1,000 IU, 500 IU and 300 IU, 750 IU, 2,500 IU, 500 IU and 2,000 IU/kg feed, according to Scott et al. (1982), NRC (1984, 1994), Rostagno et al. (1985), Leeson & Summers (1997), De Blas & Mateos (1991) and Feedstuffs (1998), respectively. Despite the fact that Yannakopoulos & Morris (1979) did not observe positive results testing cholecalciferol levels of 0, 120, 360 and 720 IU/kg, Abdulrahim et al. (1979) found that, except for the level zero, all the other treatments provided similar results on egg production, egg weight, shell weight and percentage of eggs with soft shell. Testing six levels of cholecalciferol (0, 125, 250, 375, 500 and 5,000 IU/kg) in 30-week-old layers, Shen et al. (1981) verified an immediate decrease in egg production and eggshell quality (deformities) in the non-supplemented birds. After four weeks, egg production fell to 30% and the eggs were thin-shelled or shell-less. Feed intake, egg weight, body weight and Haugh unit scores were not affected by treatments. Keshavarz (1996) used vitamin D levels from 250 to 4,400 IU/kg and vitamin C levels from 0 to 1,000 ppm and concluded that supplemental vitamin C did not have beneficial effects on eggshell quality and bone mineralization.

The present study was performed to evaluate the effects of supplementation with different levels of vitamins D and C on performance traits, internal and external egg quality and back and rectal temperatures in layers submitted to three different environmental temperatures regimens.

MATERIAL AND METHODS

The experiment was conducted in a climatic chamber during a 9-week period. One hundred forty-four Hy-Line W36 layers, aged 31 weeks were randomly assigned to 36 experimental units with four birds each, and allotted to cages measuring 50 x 45 x 40 cm (front, depth and height, respectively). A light schedule of 17 hours of light per day was maintained.

A 3x3x3 factorial design was used, with 3 levels of vitamin D₃ (2,500, 3,000 and 3,500 IU/kg), vitamin C (0, 200 and 400 ppm) and environmental temperature (thermoneutrality – 24.8^º to 27.0^º C, cyclic heat stress – 32.1^º C for 6-8h and 23.0^º to 25.0^º C for 16-18h and constant heat stress – 30.0^º to 32.0^º C). In each environmental temperature used there was one week of adaptation and two weeks of experimental period. Temperature and humidity were monitored using graded and globe thermometers and a thermohygrograph four times per day, at 7 am, 11 am, 3 pm and 7 pm.

A corn-soybean meal diet (Table 1) with 2,500 IU/kgof vitamin D₃ and no supplementation with vitamin C was prepared. The other levels of vitamin D and vitamin C in diet were obtained by adding different quantities of the respective premixes. 500 IU of vitamin D₃/kg and 200 ppm of vitamin C were added per kilogram of pre-mixture. The sources of Vitamin D and C were Rovimix^â D₃-500 (Cholecalciferol) and Lutavit^â C Aquastab (L-Ascorbic acid-2-monophosphate-calciumsalt with minimum vitamin C activity of 42%).

Feed intake (g/bird/day), egg production (% eggs/bird/day), egg weight (g), egg mass (g/bird/day) and feed conversion (g ration/g egg mass) were evaluated. Egg production was registered daily and the eggs produced in the last two days of each experiment were used to evaluate the other parameters.

Eggshell quality was evaluated by the following parameters: egg shell percentage, shell thickness (mm) and egg specific gravity (g/mL H₂O). Saline solutions to determine egg specific gravity were prepared according to Moreng & Avens (1990). Densities varied from 1.0650 to 1.0950 at 0.0025 intervals. Internal quality was evaluated by yolk and albumen percentages, Haugh unit score and yolk index. The last two characteristics were calculated according to Nesheim et al. (1979).

Back temperature was measured with an infrared digital thermometer (HORIBA^â) and rectal temperature with a clinical thermometer. In each experiment, temperature values were recorded from one bird of each experimental unit for seven days at 7 am and 3 pm.

Data were tabulated and analyzed by ESTAT 2.0 (1992) and means were compared by the Tukey's test.

RESULTS AND DISCUSSION

There were no interactions among the studied factors for all characteristics evaluated (Tables 2, 3, 4 and 5). Performance traits were not influenced by using vitamins D₃ and C (Table 2). However, feed intake, egg production, egg weight and egg mass were impaired (p<0.05) when hens were exposed to constant heat stress. On the other hand, feed:gain ratio was improved in this condition (Table 2).

Performance traits are not affected if adequate levels of vitamin D are supplemented in diet (Yannakopoulos & Morris, 1979; Abdulrahim et al., 1979; Shen et al., 1981; Frost et al., 1990). Nevertheless, very low levels in diet or no supplementation at all will have prejudicial effects on egg production and other characteristics (Abdulrahim et al., 1979; Shen et al., 1981). No influence of the supplementation with 2,200 and 4,400 IU vitamin D/kg and 0, 125 or 250 ppm of vitamin C on feed intake, egg production, egg mass or egg weight were reported (Keshavarz, 1996). Similarly, the results presented herein showed no influence of vitamins D and C on performance characteristics (Table 2). Previous researches generally have shown little influence of supplementation with vitamin C on the main performance traits. Increases in egg production were found in broiler breeders supplemented with 50 and 100 ppm of vitamin C (Peebles & Brake, 1985) and in second cycle layers supplemented with 250 and 500 ppm (Zapata & Gernat, 1995). On the other hand, Bell & Marion (1990) and Gardini (1996) did not observe any beneficial effect of vitamin C on egg production. Pardue & Thaxton (1986) reviewed some papers and found that only 37.5% of them reported benefits to egg production. Other characteristics such as feed intake (Zapata & Gernat, 1995; Gardini, 1996), egg weight (Bell & Marion, 1990; Zapata & Gernat, 1995; Gardini, 1996) and feed:gain (Gardini, 1996) also were not changed due to vitamin C supplementation. Pardue & Thaxton (1986) reported that only 21.43% of the reviewed papers showed increases in egg weight. This was seen only when vitamin C was added in extremely elevated doses such 2,000 and 3,000 ppm (Orban et al., 1993).

On the other hand, very marked effects of environmental temperature on performance were seen. A lower feed intake immediately reduces body heat production. The first thermoregulatory benefit is subtracting the specific dynamic effect, it is, the heat of digestion, absorption and uptake of feed, from the total thermal load (Harrison, 1995). The reduction in ionized calcium levels in blood and subsequently in cells will affect the transmission of hormonal signaling to the cell (Bahr, 1995). As an example, the GnRH action that regulates LH release (a hormone that is essential for the follicle growth and ovulation) will be reduced in lower concentrations of calcium. Similarly, many functions of the ovaries and other organs related to reproduction will be impaired. These biological responses will affect not only the quantity, but also the quality of production in layers (Harrison, 1995). In the range of temperature between 30.0 C and 32.0 C, the results of the present study are similar to those found by Cheng et al. (1990), who did not observe any significant effect of vitamin C supplemented up to 200 ppm on egg production. Vitamin C supplementation in drinking water could have some benefits, since the decrease in feed intake was marked in heat stress conditions (Table 2). Nevertheless, Krautmann et al. (1990) suggested the supplementation in drinking water in situations such as vaccinations, beak trimming, diseases and 24 hours before slaughter.

The highest levels of vitamins D₃ and C positively influenced (p<0.01) the parameter yolk index (Table 3). A lower yolk index was found during constant heat stress. Percentage of albumen was lower at thermoneutrality when compared to cyclic heat stress. The higher value for yolk percent was verified at constant heat stress (Table 3). Haugh unit was not altered by each factor studied. Willians (1992) studied the effect of some factors on egg internal quality (Haugh unit). Besides some diseases, the author considered that the most important factor that changes albumen quality in fresh eggs is the age of the layers. Also, even if environment temperature is high, it does not affect directly the albumen quality during oviposition. On the other hand, the author considers all aspects of environmental temperature during storage of the eggs. These considerations about environmental temperature corroborate the results showed in Table 3. In the review of Pardue & Thaxton (1986), 50% of the papers that studied the addition of vitamin C to layer ration resulted in better Haugh unit scores, while Gardini (1996) did not find any differences in Haugh unit score and yolk index using up to 200 ppm of vitamin C. However, Cheng et al. (1990) reported an increase in Haugh unit score when the diet was supplemented with 100 or 200 ppm of vitamin C under constant heat stress. Although some significant differences among the means of albumen and yolk percentages and yolk index were noticed, the values are compatible with a good score of internal quality, according to Nesheim et al. (1979).

Eggshell quality expresses as shell percent, shell thickness and egg specific gravity, was improved (p<0.01) when hens were fed two highest levels of vitamins D₃ (Table 4). Vitamin C supplementation was beneficial for shell percent (400 ppm) and egg specific gravity (200 and 400 ppm). Cyclic heat stress impaired shell thickness and constant heat stress negatively influenced all eggshell quality traits studied.

The characteristics that express external quality of eggs were improved according to Peebles & Brake (1985), who reported higher values of specific gravity in the eggs of broiler breeder fed with 50 or 100 ppm de supplemental vitamin C. Other authors used levels between 200 and 400 ppm and 250 to 500 ppm (Bell & Marion, 1990; Zapata & Gernat, 1995) also reported higher values of specific gravity, but not shell thickness. Orban et al. (1993) also reported an improvement of this trait with levels much higher than these (2,000 and 3,000 ppm). Gardini (1996) observed a significant reduction of cracked eggs with the addition of 200 ppm of vitamin C. Pardue & Thaxton (1986) reported a beneficial effect on shell thickness in only 33.33% of the reviewed papers. Keshavarz (1996) did not report any benefit on egg specific gravity in layers fed with 2,200 and 4,400 IU vitamin D/kg and with 0, 125 or 250 ppm of vitamin C. Under constant heat stress, Cheng et al. (1990) observed higher values of shell weight per unit surface area when layers were fed with 100 or 200 ppm of vitamin C. External quality of the eggs is also affected by environmental temperature. The reduction in feed intake, the decreased intestinal blood flow and ionized calcium in blood are prejudicial to these traits, and also the pCO2 reduction interferes with the production of carbonate ions in the uterus mucosae. A marked prejudicial effect on egg external quality was seen as a function of environmental temperature (Table 4).

Vitamins D₃ and C supplementation did not alter both back and rectal temperatures (Table 5). On the other hand, when hens were exposed to cyclic and constant heat stress was observed higher values of back and rectal temperatures when compared to thermoneutrality, as explained by Harrison (1995). This author states that a higher temperature of the body surface enables the bird to dissipate more heat from the body to the colder surrounding area and to reduce the thermal gradient between the bird and hotter surrounding area at the same time. The process of increasing surface temperature occurs as a response to the increase of the blood flow to the skin surface (peripheral vasodilatation) and this process is more important in the naked areas of the body. The results of rectal temperature presented herein are different from those reported by Pardue & Thaxton (1986), who observed in layers kept at 32.0 ^o C a reduction of 0.56 ^o C in those fed with 100 ppm of vitamin C when compared to control birds.

CONCLUSIONS

The results show that vitamin D₃ can be used in a little higher level than those normally used and vitamin C supplementation (200 or 400 ppm) may be beneficial to egg external quality. High environmental temperature negatively affects performance traits and external quality of the eggs.

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Publication Dates

• Publication in this collection
  30 Oct 2002
• Date of issue
  Jan 2001