Primary Audience: Broiler Managers, Live Production Managers, Nutritionists, Researchers

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1 2004 Poultry Science Association, Inc. Live Performance and Immune Responses of Straight-Run Broilers: Influences of Zinc Source in Broiler Breeder Hen and Progeny Diets and Ambient Temperature During the Broiler Production Period 1 B. P. Hudson,* W. A. Dozier, III,*,2 B. D. Fairchild,* J. L. Wilson,* J. E. Sander, and T. L. Ward *Department of Poultry Science, University of Georgia, Athens, Georgia ; Department of Avian Medicine, University of Georgia, Athens, Georgia ; and Zinpro Corp., Eden Prairie, Minnesota Primary Audience: Broiler Managers, Live Production Managers, Nutritionists, Researchers SUMMARY Supplemental zinc in broiler diets has been reported to be more available to the chick when provided as a zinc-amino acid complex rather than an inorganic source. Previous work with broiler breeder and turkey hens has indicated that supplementing diets with zinc-amino acid complexes enhances immune status and livability of progeny. This study examined the effects of supplemental dietary zinc source [ZnSO 4 or Availa Zn 100 zinc-amino acid complex (ZnAA)] provided to broiler breeder hens and their progeny on live performance and immune status of broilers. Broiler breeder and progeny diets were supplemented with 160 and 140 ppm zinc, respectively. In addition to the dietary treatments, the broilers were subjected to either optimum or suboptimum temperatures during the first weeks of production. Supplementing broiler breeder hen and progeny diets with ZnAA and ZnAA + ZnSO 4, respectively, improved cumulative feed conversion (FC) of broilers. Providing diets supplemented with ZnSO 4 to hens or exposing broilers to optimum temperatures enhanced humoral immune response of progeny. Subjecting broilers to suboptimum brooding temperatures increased feed intake, but a higher incidence of mortality occurred primarily encompassing the first week of the growout. These data indicate that brooding temperature affected broiler performance, whereas the response to dietary zinc source was less pronounced. Key words: broiler, dietary zinc, immune status, temperature 2004 J. Appl. Poult. Res. 13: DESCRIPTION OF PROBLEM Feeding purified zinc-deficient diets to hens has been reported to decrease hatchability and increase skeletal abnormalities of progeny [1, 2, 3, 4]. Hens receiving zinc supplied from only grain and oilseed meals may exhibit adverse hatchability and chick quality, while supple- 1 Use of trade names does not imply endorsement by the University of Georgia or of similar ones not mentioned. 2 To whom correspondence should be addressed: bdozier@msa-msstate.ars.usda.gov.

2 292 JAPR: Research Report TABLE 1. Ingredient composition and calculated nutrient analysis of the diets provided to broiler breeder females A Starter B Developer c Layer D Ingredient, % as is ZnAA ZnSO 4 ZnAA ZnSO 4 ZnAA ZnSO 4 Corn Soybean meal (48% CP) Poultry oil Wheat middlings Limestone Dicalcium phosphate Sodium chloride L-Lysine HCl DL-Methionine Trace mineral premix E Vitamin premix F Copper sulfate Availa Zn Zinc sulfate Total Calculated analyses CP (%) ME (kcal/kg) 2,865 2,819 2,900 Calcium (%) Available phosphorus (%) Lysine (%) Methionine (%) TSAA (%) Sodium (%) Copper (ppm) Zinc (ppm) A Broiler breeder females received diets supplemented with 160 ppm zinc from ZnSO 4 or Availa Zn zinc-amino acid complex (ZnAA) from 0 to 65 wk of age. Analyzed zinc concentrations in the finished diets averaged 192 ppm zinc. B Diets were provided from 0 to 19 d of age to all females. C Diets were provided from 20 d to 22 wk of age to all females. D Diets were provided from 23 to 45 wk of age to all females. E Trace mineral premix provided the following (mg/kg of diet): selenium, 0.3; manganese, 121; iron, 75; iodine, 0.8. F Vitamin premix provided the following per kilogram of diet: vitamin A, 11,000 IU; vitamin D 3, 2,200 IU; vitamin E, 22 IU; vitamin K, 2.2 mg; vitamin B 12, 0.2 mg; thiamine 4.4 mg; riboflavin, 8.8 mg; vitamin B 6, 4.4 mg; niacin, 88 mg; pantothenic acid, 22 mg; folic acid 1.1 mg; biotin, 2.2 mg; choline, 380 mg. menting hen diets with zinc enhanced fertility and hatchability [5], eggshell quality [6], egg production [7], progeny livability [8, 9], and progeny immune status [10, 11, 12, 13, 14]. Broilers provided diets supplemented with organic zinc sources have greater zinc accumulation in bone and pancreas tissue than birds given diets with supplemental zinc from inorganic sources [15, 16]. Pimental et al. [15] reported that pancreatic zinc concentrations were elevated by 33% when chicks were provided zinc-methionine rather than ZnO. Wedekind et al. [16] used slope ratio analyses to estimate the bioavailabilities of zinc from organic zinc-methionine, inorganic ZnSO 4,and inorganic ZnO in corn-soybean meal diets fed to broiler chicks. Relative bioavailability of zinc from zinc-methionine was estimated at 206% compared with ZnSO 4 (set at 100%) using tibia zinc concentration as the response criterion. Diets supplemented with zinc-amino acid complexes have been shown to improve feed conversion (FC) in broilers. Hess et al. [17] supplemented practical broiler diets (55 ppm zinc from ZnSO 4 ) with 40 ppm zinc from 3 different zinc-amino acid complexes. Feed conversion was improved from 0 to 35 d and from 0 to 42 d of age when supplemental zincamino acid complexes were provided to female broilers. Sanford and Kawchumnong [18] reported improved feed utilization by broilers

3 HUDSON ET AL.: DIETARY ZINC AND AMBIENT TEMPERATURE 293 TABLE 2. Ingredient composition and calculated nutrient analysis of the diets fed to straight-run broilers during a 42-d production period A Starter B Developer C Finisher D Ingredient, % as is ZnAA ZnSO 4 ZnAA ZnSO 4 ZnAA ZnSO 4 Corn Soybean meal (48% CP) Poultry meal (60% CP) Poultry oil Limestone Dicalcium phosphate L-Lysine HCl DL-Methionine Sodium chloride Copper sulfate Coban Mineral premix E Vitamin premix F Availa Zn Zinc sulfate Total Calculated analyses CP (%) ME (kcal/kg) 3,075 3,165 3,240 Calcium (%) Available phosphorus (%) Lysine (%) Methionine (%) TSAA (%) Sodium (%) Copper (ppm) Zinc (ppm) A Broilers received diets supplemented with ZnSO 4 (140 ppm zinc) or a combination of Availa Zn (40 ppm zinc) and ZnSO 4 (100 ppm zinc) from 0 to 42 d of age. Analyzed zinc concentrations in the finished broiler diets averaged 151 ppm. ZnAA = zinc-amino acid complex. B Diets were provided from 0 to 17 d of age. C Diets were provided from 18 to 30 d of age. D Diets were provided from 31 to 42 d of age. E Trace mineral premix provided the following (mg/kg of diet): selenium, 0.3; manganese, 121; iron, 75; iodine, 0.8. F Vitamin mineral premix provided the following per kilogram of diet: vitamin A, 11,000 IU; vitamin D 3, 2,200 IU; vitamin E, 22 IU; vitamin K, 2.2 mg; vitamin B 12, 0.2 mg; thiamine 4.4 mg; riboflavin, 8.8 mg; vitamin B 6, 4.4 mg; niacin, 88 mg; pantothenic acid, 22 mg; folic acid 1.1 mg; biotin, 2.2 mg; choline, 380 mg. when dietary zinc was supplemented as zincmethionine rather than ZnO. Providing zinc-amino acid complexes in broiler breeder and turkey hen diets enhanced the cellular immune response of progeny as measured by cutaneous basophil hypersensitivity tests compared with inorganic zinc supplementation [10, 11, 12, 13, 14]. Progeny livability improved when hens were given supplemental zinc as a zinc-amino acid complex [8, 9]. This enhanced cellular immune response with zinc-amino acid complexes may relate to increased bioavailability compared with ZnO or ZnSO 4 [16]. The inability of young chicks to regulate their body temperature during the first days of life requires the use of supplemental heat in growout facilities [19, 20, 21, 22]. In practice, it is a challenge with some contract growers to maintain proper brooding temperatures, especially when fuel costs are elevated. Broiler chicks subjected to suboptimum brooding temperatures have decreased activity, which results in reduced feed and water intake. This situation is known to increase chick mortality. Previous research has evaluated the influences of delayed feed intake and low brooding temperature on broiler performance. Brooding

4 294 JAPR: Research Report TABLE 3. Temperature setpoints and actual temperatures provided to straight-run broilers subjected to 2 different brooding programs during a 42-d production period A Temperature setpoint( C) Actual temperature B ± SD ( C) Age (d) Normal Low Normal Low 0 to ± ± to ± ± to ± ± to ± ± to ± ± to ± ± to ± ± to ± ± to ± ± 0.6 A Broilers were exposed to normal or low brooding temperatures prior to 20 d of age. B Calculated as an average of the average daily temperatures during the periods indicated. temperatures at or below 26.7 C increases the mortality of broilers [23, 24, 25] possibly due to inadequate feed intake or nutrient absorption early in life. According to Uni et al. [26], withholding feed for 36 h slows development of the intestinal tract in chicks. Nutrients and antibodies from the yolk sac are poorly absorbed and immune status may be depressed [27] when chicks are exposed to suboptimum ambient temperatures during the first weeks of life. TABLE 4. Live performance responses of broilers originating from hens fed diets supplemented with 2 different zinc sources, subjected to 2 different brooding temperatures, and fed diets containing 2 different zinc sources from placement until 17 d of age A Treatment Feed CV of BW intake BW gain Mortality at 17 d Hen Zn B Progeny Zn C Temperature D (kg) (kg) FC E (%) (%) ZnSO 4 ZnSO 4 N ZnSO 4 ZnSO 4 L ZnSO 4 ZnAA N ZnSO 4 ZnAA L ZnAA ZnSO 4 N ZnAA ZnSO 4 L ZnAA ZnAA N ZnAA ZnAA L SEM Source of variation Hen Zn NS F NS NS NS NS Progeny Zn NS NS NS NS NS Temperature NS NS NS * NS Hen Zn progeny Zn NS NS NS NS NS Hen Zn temperature NS NS NS NS NS Progeny Zn temperature * NS NS NS NS Hen Zn progeny Zn temperature NS NS NS NS NS A Values are least squares means, involving 48 pens, each with 42 chicks at placement. Chicks resulted from eggs laid during 29 and 30 wk of age. Average chick weight with standard error was 37.5 ± 0.2 g at hatch. B Broiler breeder hens were given diets supplemented with 160 ppm zinc from ZnSO 4 or Availa Zn. ZnAA = zinc-amino acid complex. C Broilers were given diets supplemented with 140 ppm zinc from ZnSO 4 or a mixture of Availa Zn (40 ppm zinc) and ZnSO 4 (100 ppm zinc). D Broilers were exposed to normal (N) or low (L) brooding temperatures prior to 20 d of age. E Feed conversion (FC) values are corrected for mortality. F P *P 0.05.

5 HUDSON ET AL.: DIETARY ZINC AND AMBIENT TEMPERATURE 295 TABLE 5. Live performance responses of broilers originating from hens fed diets supplemented with 2 different zinc sources, subjected to 2 different brooding temperatures, and fed diets containing 2 different zinc sources from 18 to 30 d of age A Treatment Feed intake BW gain Mortality Hen Zn B Progeny Zn C Temperature D (kg) (kg) FC E (%) ZnSO 4 ZnSO 4 N ZnSO 4 ZnSO 4 L ZnSO 4 ZnAA + ZnSO 4 N ZnSO 4 ZnAA + ZnSO 4 L ZnAA ZnSO 4 N ZnAA ZnSO 4 L ZnAA ZnAA + ZnSO 4 N ZnAA ZnAA + ZnSO 4 L SEM Source of variation Hen Zn NS F NS NS NS Progeny Zn NS NS NS NS Temperature * *** NS NS Hen Zn progeny Zn NS NS NS NS Hen Zn temperature NS NS NS NS Progeny Zn temperature NS NS NS NS Hen Zn progeny Zn temperature NS NS NS NS A Values are least squares means, involving 48 pens, each with 42 chicks at placement. B Broiler breeder hens were given diets supplemented with 160 ppm zinc from ZnSO 4 or Availa Zn. ZnAA = zinc-amino acid complex. C Broilers were given diets supplemented with 140 ppm zinc from ZnSO 4 or a mixture of Availa Zn (40 ppm zinc) and ZnSO 4 (100 ppm zinc). D Broilers were exposed to normal (N) or low (L) brooding temperatures prior to 20 d of age. E Feed conversion (FC) values are corrected for mortality. F P *P ***P The increased bioavailability of ZnAA complexes in broilers [16] has been directly associated with increased egg yolk zinc content when these complexes are fed to hens [28]. Therefore, the chick may retain additional zinc during embryonic development, when broiler breeder hens are fed diets containing zincamino acid complexes. Increasing zinc retention in chicks may enhance immune function and lower the incidence of morbidity or mortality when broilers are subjected to less than favorable environmental conditions. This study evaluated the effects of zinc source in hen and progeny diets and brooding temperature profiles of progeny chicks on live performance and immune status of broilers. MATERIALS AND METHODS Breeder Husbandry and Dietary Zinc Two hundred fifty Cobb [29] broiler breeder males and 750 broiler breeder females (slow-feathering Cobb 500) were obtained from a local hatchery and reared by primary breeder recommendations in single-sex floor pens. In order to determine feed allotments and achieve target BW, a sample of 24 hens per dietary treatment was weighed weekly. At 21 wk of age, all birds were housed in cages and provided 16 h light per day. The facility was evaporatively cooled and forced-air heated. Although the dietary zinc requirement for broiler breeder hens has not been established, personal communication with nutritionists in the US poultry industry revealed that broiler breeder diets typically contain supplemental zinc in the range of 120 to 180 ppm. Therefore, supplemental zinc (160 ppm) was added to the starter, developer, and layer diets of female broiler breeders from either ZnSO 4 or Availa Zn 100 zinc-amino acid complex (ZNAA) [30] from 0 to 65 wk of age (Table 1). Including the supplemental zinc, the starter, developer,

6 296 JAPR: Research Report TABLE 6. Live performance responses of broilers originating from hens fed supplemented with 2 different zinc sources, subjected to 2 different brooding temperatures, and fed diets containing 2 different zinc sources from 31 to 42 d of age A Treatment Feed intake BW gain Mortality Hen Zn B Progeny Zn C Temperature D (kg) (kg) FC E (%) ZnSO 4 ZnSO 4 N ZnSO 4 ZnSO 4 L ZnSO 4 ZnAA + ZnSO 4 N ZnSO 4 ZnAA + ZnSO 4 L ZnAA ZnSO 4 N ZnAA ZnSO 4 L ZnAA ZnAA + ZnSO 4 N ZnAA ZnAA + ZnSO 4 L SEM Source of variation Hen Zn NS F NS NS NS Progeny Zn NS NS NS NS Temperature NS NS NS * Hen Zn progeny Zn NS NS * NS Hen Zn temperature NS NS NS NS Progeny Zn temperature NS NS NS NS Hen Zn progeny Zn temperature NS NS NS NS A Values are least squares means, involving 48 pens, each with 42 chicks at placement. B Broiler breeder hens were given diets supplemented with 160 ppm zinc from ZnSO 4 or Availa Zn. ZnAA = zinc-amino acid complex. C Broilers were given diets supplemented with 140 ppm zinc from ZnSO 4 or a mixture of Availa Zn (40 ppm zinc) and ZnSO 4 (100 ppm zinc). D Broilers were exposed to normal (N) or low (L) brooding temperatures prior to 20 d of age. E Feed conversion (FC) values are corrected for mortality. F P *P and layer diets were formulated to contain 172 ppm zinc, respectively. After conducting inductively coupled plasma analyses [31] on duplicate feed samples throughout the experiment, zinc concentrations for basal- and zincsupplemented diets for the broiler breeder females were found to have 37 ± 8 and 192 ± 37 ppm zinc, respectively (n = 8). Slight differences between formulated and determined values were likely due to an underestimation of actual zinc concentration in corn and soybean meal. All males received a common diet containing ZnSO 4. Semen was collected from males by the abdominal massage technique [32]. Hens were artificially inseminated for four consecutive weeks with neat semen, and hatching eggs laid during 29 and 30 wk of age were incubated. Temperature settings from 0 to 18 and 19 to 21 d of incubation were 37.8 and 37.2 C, respectively. Relative humidity settings at 0 to 19 and 20 to 21 d of incubation were 53 and 70%, respectively. Chicks were removed from the hatcher and counted after 21.5 d of incubation. Broiler Husbandry and Dietary Zinc A total of 2,016 1-d-old straight-run chicks were vent sexed, and 21 of each sex were commingled and randomly assigned to 1 of 48 floor pens (0.084 m 2 /bird). Broilers were provided diets with 140 ppm supplemental zinc from either ZnSO 4 (140 ppm) or a mixture of ZnAA (40 ppm) and ZnSO 4 (100 ppm) (Table 2). Broiler starter, grower, and finisher diets were formulated to contain a total of 169, 169, and 166 ppm zinc, respectively, using NRC [33] ingredient compositions for zinc. Actual zinc concentrations as determined by inductively coupled plasma analyses [31] revealed that finished broiler diets contained 151 ± 14 ppm zinc (starter, grower, and finisher; analysis of each feed was performed in triplicate). Slight differ-

7 HUDSON ET AL.: DIETARY ZINC AND AMBIENT TEMPERATURE 297 TABLE 7. Final live performance responses of broilers originating from hens fed diets supplemented with 2 different zinc sources, subjected to 2 different brooding temperatures, and fed diets containing 2 different zinc sources from placement to 42 d of age A Treatment Feed Total intake BW gain Cumulative mortality Hen Zn B Progeny Zn C Temperature D (kg) (kg) FC E (%) ZnSO 4 ZnSO 4 N ZnSO 4 ZnSO 4 L ZnSO 4 ZnAA + ZnSO 4 N ZnSO 4 ZnAA + ZnSO 4 L ZnAA ZnSO 4 N ZnAA ZnSO 4 L ZnAA ZnAA + ZnSO 4 N ZnAA ZnAA + ZnSO 4 L SEM Source of variation Hen Zn NS F NS NS NS Progeny Zn NS NS NS NS Temperature * NS NS ** Hen Zn progeny Zn NS NS * NS Hen Zn temperature NS NS NS NS Progeny Zn temperature NS NS NS NS Hen Zn progeny Zn temperature NS NS NS NS A Values are least squares means, involving 48 pens, each with 42 chicks at placement. Chicks resulted from eggs laid during 29 and 30 wk of age. Average chick weight with standard error was 37.5 ± 0.2 g at hatch. B Broiler breeder hens were given diets supplemented with 160 ppm zinc from ZnSO 4 or Availa Zn. C Broilers were given diets supplemented with 140 ppm zinc from ZnSO 4 or a mixture of Availa Zn (40 ppm zinc) and ZnSO 4 (100 ppm zinc). D Broilers were exposed to normal (N) or low (L) brooding temperatures prior to 20 d of age. E Feed conversion (FC) values are corrected for mortality. F P *P **P ences between formulated and determined values were likely due to an overestimation of actual zinc concentrations in corn and soybean meal. Normal (N) or low (L) brooding temperatures were provided from 0 to 20 d of age, and initial temperatures were 33.3 or 28.9 C for the N and L treatments, respectively. Temperatures were reduced at 5-d intervals and were the same (26.7 C) for both treatments by 20 d of age (Table 3). Each brooding room contained 2 forced air furnaces. Daily temperatures were determined from a sensor located in the center of each room at 9 cm above the floor. An average of the high and low temperatures was calculated daily. Feed and water were offered ad libitum, and the lighting program provided 23 h light (20 lx) from 0 to 3 d, 16 h light (5 lx) from 4 to 22 d, and 23 h light (20 lx) from 23 to 42 d. The lighting program was modified from those described by Classen and Riddell [34]. This lighting schedule is similar to those being employed in commercial practice. All birds were weighed individually at 17 d and by pen at 30 and 42 d. Feed intake was determined during the starter (0 to 17 d), grower (18 to 30 d), finisher (31 to 42 d), and cumulative (0 to 42 d) periods. Immune Measurements To assess humoral immune status, 2 randomly selected birds per pen were intravenously injected with a 0.1 ml of suspension of SRBC in phosphate-buffered saline (0.5% SRBC in PBS) at 10 d of age. Birds used for humoral status and other immune tests were identified by applying a small amount of paint to the wing feathers. At 15 d, blood was collected from the brachial vein in sodium heparin tubes and centrifuged at 700 g for 15 min. After obtaining plasma, it was stored at 4 C until

8 298 JAPR: Research Report TABLE 8. Immune responses of broilers originating from hens fed diets supplemented with 2 different zinc sources, subjected to 2 different brooding temperatures, and fed diets containing 2 different zinc sources A Treatment SRBC Bursa Thymus Spleen titer E PHA-P F Hen Zn B Progeny Zn C Temperature D (% of BW) (% of BW) (% of BW) (log 2 ) (mm) ZnSO 4 ZnSO 4 N ZnSO 4 ZnSO 4 L ZnSO 4 ZnAA + ZnSO 4 N ZnSO 4 ZnAA + ZnSO 4 L ZnAA ZnSO 4 N ZnAA ZnSO 4 L ZnAA ZnAA + ZnSO 4 N ZnAA ZnAA + ZnSO 4 L SEM Source of variation Hen Zn NS G NS NS * NS Progeny Zn NS NS NS NS NS Temperature NS NS NS * NS Hen Zn progeny Zn NS NS *** NS NS Hen Zn temperature NS NS NS NS NS Progeny Zn temperature NS NS NS NS NS Hen Zn progeny Zn temperature NS NS NS NS NS A Spleen, thymus, and bursa of Fabricius were harvested from 17-d-old broilers. No differences in BW of the sampled birds were observed among the treatments (P > 0.05). Values are least squares means, involving 48 pens, each with 42 chicks at placement. Immune measurements were conducted on 2 randomly selected birds from each pen. B Broiler breeder hens were given diets supplemented with 160 ppm zinc from ZnSO 4 or Availa Zn. ZnAA = zinc-amino acid complex. C Broilers were given diets supplemented with 140 ppm zinc from ZnSO 4 or a mixture of Availa Zn (40 ppm zinc) and ZnSO 4 (100 ppm zinc). D Broilers were exposed to normal (N) or low (L) brooding temperatures prior to being sampled. E Hemagglutination tests were done to assess antibody titers to SRBC after intravenously injecting 0.1 ml of a suspension (0.5% SRBC) at 10 d of age, then collecting plasma at 15 d of age. F At 10 d of age, birds were given a 0.1-mL intradermal injection of saline and phytohemagglutinin-p (0.1 mg PHA-P in suspension) between the second and third digits of the left and right feet, respectively. At 18 h postinjection, the width of the left (saline-injected) toe web was subtracted from the postinjection width of the right (PHA-injected) toe web. G P *P ***P used to determine antibody titers to SRBC by hemagglutination testing [35]. Titers were determined by serially diluting 25 µl of serum in PBS and adding 25 µl SRBC (0.75% in PBS) and incubating for 6 h at 37 C. Titers are expressed as log 2 of the reciprocol of the lowest dilution of plasma, which produced agglutination [36]. At 10 d of age, 2 additional birds per pen were given a 0.1 ml intradermal toe web injection of PBS and phytohemagglutinin-p (PHA- P) (0.1 mg PHA-P in PBS) in the left and right feet, respectively. Digital calipers [37] were used to measure toe web thickness prior to injection and 18 h postinjection. To calculate cellular immune response, the postinjection thickness of the left (PBS injected) toe web was subtracted from the postinjection thickness of the right (PHA-P injected) toe web [38]. After measuring BW of 2 birds per pen at 17 d of age, the spleen, thymus, and bursa of Fabricius weights were determined to evaluate development of immune organs. No birds were used for more than 1 immune test. Statistical Analysis Data were analyzed using the general linear model of SAS software [39]. Each treatment was represented by 6 replicate pens, and pen served as the experimental unit. Within each brooding temperature split-plot treatment, birds were subjected to a randomized complete block design arrangement of 2 hen diets and 2 progeny diets. All possible 2-way and 3-way

9 HUDSON ET AL.: DIETARY ZINC AND AMBIENT TEMPERATURE 299 interactions were included in the model, and a significance level of P 0.05 was used. Body weight uniformity was calculated as the CV, and mortality data were subjected to arc sine transformation prior to statistical analysis. While inferences were determined from the transformed data, only nontransformed data are presented for relevance. RESULTS AND DISCUSSION Differences in growth rate, nutrient utilization, and livability of broilers attributable to dietary zinc were not obvious from placement to 17 d of age (Table 4). However, a significant progeny zinc temperature interaction (P 0.04) occurred for feed intake, indicating that broilers provided supplemental ZnSO 4 consumed more starter feed than broilers provided ZnAA + ZnSO 4 when subjected to suboptimum brooding temperatures. Brooding temperature did not alter feed intake, BW gain, FC, or BW uniformity of broilers. Birds subjected to L temperatures had a higher incidence of mortality than birds exposed to N temperatures at 7 (3.1 vs. 1.3%; P < 0.02) and 17 d of age (3.8 vs. 1.8%; P < 0.03). From 18 to 30 d of age, zinc source in hen and progeny diets did not influence broiler performance (Table 5). Broilers subjected to suboptimum brooding temperatures had increased feed intake (1.48 vs kg; P < 0.001) and growth rate (1.05 vs kg; P < 0.001), but FC and the incidence of mortality were unaffected. In agreement, the indirect relationship between feed intake and temperature has been previously reported [40]. By optimizing brooding temperature, the maintenance needs of the broiler should be reduced, thus allowing more nutrients for growth [41]. Perhaps broilers initially subjected to moderately low temperatures can have compensatory growth if early development is not severely limited by temperature effects. During the final phase of growout, supplemental zinc source in the hen and progeny diets did not alter broiler performance with the exception of FC (Table 6). A significant hen zinc progeny zinc source interaction (P < 0.04) indicated that FC was optimized, when both hens and their progeny consumed ZnAA and ZnAA + ZnSO 4, respectively. Feed intake and FC during the finisher period were not influenced by brooding temperature, but mortality was significantly increased (1.7 vs. 0.5%; P < 0.02) for broilers brooded at suboptimum temperatures. Zinc source in hen or progeny diets did not alter final BW or cumulative feed consumption (Table 7). Although previous research has shown that feeding zinc-amino acid complexes to broiler breeder hens [9] or Leghorn-type laying hens [8] reduced early mortality of progeny, zinc source in hen and progeny diets did not influence mortality in this experiment. A significant hen zinc source progeny zinc source interaction (P < 0.04) indicated that cumulative FC was lowest when both hens and their progeny consumed ZnAA and ZnAA + ZnSO 4, respectively. Brooding temperature did not influence cumulative FC in the present study, but broilers subjected to L temperatures consumed more feed and had a higher incidence of total mortality throughout the 42-d growout period. The increase in feed consumption due to low brooding temperatures led to a numerical difference in final BW that approached significance (P = 0.055). Previous research has reported that final BW was unaffected by brooding temperature [42, 43], but feed intake was increased with low ambient temperatures [40]. Other research has demonstrated poor nutrient utilization when broilers were subjected to low ambient temperatures [27, 40, 42, 43, 44], but temperatures were considerably lower (7.2 to 26.7 C) than those used in this experiment. Thymus weight, bursa weight, and cellular immune response of broilers were unaffected by zinc source in hen or progeny diets (Table 8). Spleen weights were lower (P < 0.001) when hens and their progeny both consumed diets supplemented with ZnSO 4 compared with treatments containing ZnAA in either the hen or progeny diet. Although a significant treatment effect was observed, the difference was small and ready interpretation is elusive. Broilers expressed higher antibody titers to SRBC when their parent hen consumed ZnSO 4 (3.22 vs log 2 ; P < 0.04). Reasons for this occurrence are not apparent because previous research has reported that humoral immune response of progeny is not affected by supple-

10 300 JAPR: Research Report mental zinc source in broiler breeder hen diets [10, 11, 14]. However, Kidd et al. [11] reported that progeny from broiler breeder hens consuming diets with supplemental ZnO had greater SRBC titers than progeny from hens not provided supplemental zinc in their diet. Prior research has documented enhanced cellular immune response of progeny when turkey or broiler breeder hens consume diets containing zinc-amino acid complexes rather than inorganic zinc sources [10, 11, 13, 14]. However, zinc source in hen or progeny diets did not influence the swelling response after PHA- P injection in progeny, possibly due to higher concentrations of dietary zinc used in this experiment compared with previous reports. If more immunocompetent breeders and progeny can consistently result from modifications to the zinc components in breeder diets, then vaccine and antibiotic use may be reduced. Brooding temperature did not influence organ weights or cellular immune response, but antibody titers to SRBC were greater (3.22 vs log 2 ; P < 0.04) for broilers kept at N temperatures (Table 8). Previous research has not observed reduced antibody titers to SRBC in cold-stressed poultry [45, 46, 47], but a relationship has been reported in heat-stressed broilers [48]. Thaxton and Siegel [48] suggested that elevated concentrations of plasma adrenocorticotropic hormone or glucocorticoids were responsible for immunodepression in heat-stressed chicks, possibly from reduced antigen affinity of circulating antibodies. A similar phenomenon may have occurred in chicks subjected to low temperatures in this experiment, suppressing humoral immune response. Subba Rao and Glick [45] suggested that activities of the thyroid and the adrenal cortex interacted to increase humoral immune responsiveness in birds that were cold stressed more severely than those in this experiment. Variations in temperature and duration of temperature treatments between the 2 experiments may alter thyroid and adrenal function differently, resulting in contrasting effects on humoral immune response. These data indicate that brooding temperature influenced broiler livability and feed intake, while zinc sources in parent and broiler diets had interacting effects on FC. CONCLUSIONS AND APPLICATIONS 1. Cumulative FC was improved when broiler breeder hens and their progeny consumed diets having added ZnAA and ZnAA + ZnSO 4, respectively. 2. The main effects of zinc source in the hen or progeny diets did not alter broiler performance. Humoral immune response of broilers was greater when hens consumed diets supplemented with ZnSO 4 rather than ZnAA. 3. Subjecting broilers to suboptimum brooding temperatures enhanced feed intake, suppressed humoral immune response and increased the incidence of 17-d mortality. The majority of the early-mortality occurred from placement to 7 d of age. REFERENCES AND NOTES 1. Supplee, W. C., D. L. Blamberg, O. D. Keene, G. F. Combs, and G. L. Romoser Observations on zinc supplementation of poultry rations. Poult. Sci. 37: Turk, D. E., Sunde, M. L., and W. G. Hoekstra Zinc deficiency experiments with poultry. Poult. Sci. 38(Suppl. 1):1256. (Abstr.) 3. Blamberg, D. L., U. B. Blackwood, W. C. Supplee, and G. F. Combs Effect of zinc deficiency in hens on hatchability and embryonic development. Proc. Soc. Exp. Biol. Med. 104: Kienholz, E. W., D. E. Turk, M. L. Sunde, and W. G. Hoekstra Effects of zinc deficiency in the diets of hens. J. Nutr. 75: Anshan, S Effect of zinc and calcium levels in hen diets on fertility. Sci. Agric. Sin. 23(6): Guo, Y. M., R. Yang, J. Yuan, T. L. Ward, and T. M. Fakler Effect of Availa Zn and ZnSO 4 on laying hen performance and egg quality. Poult. Sci. 81(Suppl. 1):40. (Abstr.) 7. Khajarern, J., C. Ratanasethakul, S. Kharajarern, T. L. Ward, T. M. Fakler, and A. B. Johnson Effect of zinc and manganese amino acid complexes (Availa Z/M) on broiler breeder production and immunity. Poult. Sci. 81(Suppl. 1):40. (Abstr.) 8. Flinchum, J. D., C. F. Nockels, and R. E. Moreng Aged hens fed zinc methionine had chicks with improved performance. Poult. Sci. 68(Supp.1):55. (Abstr.) 9. Virden, W. S., J. B. Yeatman, S. J. Barber, C. D. Zumwalt, T. L. Ward, A. B. Johnson, and M. T. Kidd Responses of

11 HUDSON ET AL.: DIETARY ZINC AND AMBIENT TEMPERATURE 301 chicks from broiler breeders fed supplemental zinc and manganese: Live performance and processing. Poult. Sci. 81(Suppl. 1):119. (Abstr.) 10. Kidd, M. T., N. B. Anthony, and S. R. Lee Progeny performance when dams and chicks are fed supplemental zinc. Poult. Sci. 71: Kidd, M. T., N. B. Anthony, L. A. Newberry, and S. R. Lee Effect of supplemental zinc in either a corn-soybean or a milo and corn-soybean meal diet on the performance of young broiler breeders and their progeny. Poult. Sci. 72: Kidd, M. T., P. R. Ferket, and M. A. Qureshi Zinc metabolism with special reference to its role in immunity. World s Poult. Sci. J. 52: Kidd, M. T., M. A. Qureshi, P. R. Ferket, and L. N. Thomas Turkey hen zinc source affects progeny immunity and disease resistance. J. Appl. Poult. Res. 9: Virden, W. S., J. B. Yeatman, S. J. Barber, K. O. Willeford, T. L. Ward, T. M. Fakler, and M. T. 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