Effects of feeding high carbohydrate or high fat diets. 1. Growth and metabolic status of the posthatch poult following immediate or delayed access to feed

Effects of Feeding High Carbohydrate or High Fat Diets. 1. Growth and Metabolic Status of the Posthatch Poult Following Immediate or Delayed Access to Feed1 K. A. TURNER,2 T. J. APPLEGATE, and M. S. LILBURN3 Department of Animal Sciences, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster, Ohio 44691 addition, one-half of the WH poults fed the CHO diet had plasma glucose concentrations in excess of 500 mg/ dL at 2 DPF. In Experiment 3, similar feeding regimens and diets were used with the addition of a third diet containing a synthetic medium-chain triglyceride emulsion (MCT) as the supplemental fat source. Poults fed the FAT and MCT diets were 41 g heavier than poults fed the CHO diet at 13 DPF (P ≤ 0.05). Similar to the results of Experiment 2, poults fed the CHO diet had increased hepatic glycogen concentrations at 2 DPF, and within the WH treatment at 2 DPF, 30% of the poults had plasma glucose concentrations in excess of 500 mg/dL. Metabolic consequences of delayed placement were also found. At both 4 and 7 DPF, WH poults had a reduced capacity for glucose clearance 60 min after a glucose load (250 mg; P ≤ 0.05). The current experiments demonstrate that supplemental fat may ease the metabolic shift toward glycolysis after hatching, thereby improving growth through 2 wk of age.

(Key words: poult, fat, carbohydrate, delayed placement, glycogen) 1999 Poultry Science 78:1573–1580

INTRODUCTION The turkey poult enters postembryonic life deriving energy from the gluconeogenic and ketogenic precursors found within yolk sac reserves and hepatic stores (Romanoff, 1960; Freeman and Vince, 1974), thereby sparing muscle protein (Moran and Reinhart, 1980). In the commercial turkey industry, considerable variability exists in hatching time because of factors such as commercial genotype and differences in egg size and age of hen. As a result, some eggs may be held in the hatcher after 28 d to ensure maximal poult yield (poults hatched per eggs set) followed by a series of standard hatchery procedures

Received for publication January 19, 1999. Accepted for publication July 8, 1999. 1 Salaries and research support provided by state and federal funds appropriated to the Ohio Agricultural Research and Development Center, The Ohio State University. 2 Present address: Akey, Inc., Lewisburg, OH 45338. 3 To whom correspondence should be addressed: [email protected]

(i.e., sexing, desnooding, toe clipping, beak trimming). These procedures could further compromise remaining energy reserves (Donaldson et al., 1991). After processing, poults may face additional holding and transport periods of 24 to 48 h before arrival at a growing farm. It would not be uncommon, therefore, for poults to rely on body reserves for more than 2 d after hatching. Poults have the capacity for considerable glycogenesis if they have access to dietary carbohydrate, but this could serve as an additional metabolic stress (Donaldson and Christensen, 1991). Some researchers have questioned the ability of poults to regulate glucose metabolism after hatch and have suggested that this may contribute to peaks in early mortality beginning at approximately 4 d

Abbreviation Key: β-HBA = β-hydroxybutyrate; CHO = diet containing a high proportion of carbohydrate from corn; DPF = days postfeeding; FAT = diet containing 10% supplemental animal-vegetable fat; FED = immediate access to feed and water; MCFA = medium-chain fatty acid; MCT = diet containing 10% supplemental medium-chain triglyceride; WH = feed and water withheld for 48 h.

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ABSTRACT Three experiments were conducted with turkey poults to determine the effects of diet and delayed placement on growth and selected aspects of carbohydrate metabolism. Immediately after hatch, poults were placed in batteries and allowed either immediate access to feed and water (FED) or feed and water withdrawal for 48 h (WH). In the first two experiments, diets contained a high proportion of carbohydrate from corn (CHO; 60% of diet) or a lower proportion of corn (26%) and 10% supplemental animal-vegetable fat (FAT). The WH poults weighed less than FED poults at 5 d postfeeding (DPF; P ≤ 0.05) but not at 13 DPF. Similarly, poults fed the CHO diet were heavier 5 DPF, whereas poults fed the FAT diet were heavier at 13 DPF (P ≤ 0.05). Regardless of feeding regimen (WH vs FED), all poults were nearly depleted of hepatic glycogen prior to feeding. At 2 DPF, poults fed the CHO diet had more hepatic glycogen concentrations compared with those fed the FAT diet (P ≤ 0.002). In

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TABLE 1. Ingredient composition and determined and calculated analyses of diets containing a high proportion of carbohydrate supplied by corn (CHO; 60% of diet) or 10% supplemental fat from an animal-vegetable fat blend (FAT) or fat containing medium-chain triglyceride (MCT; Experiment 3 only) Ingredients and analysis

CHO

FAT

MCT

(%)

. . . . . .

. . . . . .

..

60.7 2.0 5.0 22.0 8.0 . . . . . . 0.2 . 0.1 2.0

3,082 25.6 26.1 1.64 0.68 1.23

.. .. ..

..

..

26.0 1.0 . . . 54.0 1.5 10.8 . 3.0 1.1 0.3 0.3 . 2.0

3,049 25.8 27.9 1.68 0.71 1.16

.. .. .. ..

..

26.0 1.0 . . . 54.0 1.5 . 10.8 3.0 1.1 0.3 0.3 . 2.0

3,049 ... 28.0 1.68 0.71 1.16

1

Captex 8000, Capital City Products, Columbus, OH 43215-1141. The premix contains (in kilograms per 100 kg premix): ground corn, 54.0; amprolium (25%), 2.5; selenium premix (200 mg Se/kg), 5.00; bacitracin MD, 2.5; choline chloride (60%), 6.00; vitamin premix, 25.00; and trace mineral premix, 5.00. 3 The vitamin premix contributed the following per kilogram of diet: vitamin A, 8,745 IU; cholecalciferol, 3,745 ICU; vitamin E, 60 IU; vitamin K (menadione sodium bisulfite), 2.91 mg; thiamin HCl, 2.2 mg; riboflavin, 6.6 mg; niacin, 99 mg; pantothenic acid, 15.4 mg; folic acid, 1.2 mg; pyridoxine, 2.2 mg; biotin, 165 mg; vitamin B12, 15 mg; and ethoxyquin, 113.5 mg. 4 The trace mineral premix contributed the following per kilogram of diet: zinc oxide (72% Zn), 147 mg; manganous oxide (55% Mn), 152 mg; copper sulfate (25.2% Cu), 35 mg; ferrous sulfate monohydrate (31% Fe), 72 mg; and potassium iodide, 1.5 mg. 5 Determined CP of CHO and FAT diets used in Experiments 1 and 2. Diet samples were analyzed in duplicate. 6 Determined CP of CHO, FAT, and MCT diets used in Experiment 3. Diet samples were analyzed in duplicate. 2

MATERIALS AND METHODS of age (Phelps et al., 1987a). When newly hatched chicks are fed a typical starter diet, incorporation of glucose into hepatic glycogen stores is highly variable until 12 d of age, which supports the hypothesis of less than optimal glucose metabolism during the early posthatch period (Goodridge, 1968). The form of glucose administration can also have effects on posthatch metabolism. For example, a subcutaneous injection of glucose at the hatchery may temporarily shift the poult from a gluconeogenic and ketogenic metabolic condition over to a glycolytic state. This shift would be exacerbated if feed and water were not immediately available after the initial glucose surge (Moran, 1989, 1990). There have been previous reports in which dietary intervention has been used in an attempt to manipulate the

4

Petersime Inc., Gettysburg, OH 45328.

Three experiments were conducted with newly hatched poults. Diets containing different sources of ME were fed on the day of hatch or following a 48-h holding period. During the holding period, all poults were kept in the same heated battery brooders.

Experiment 1 Eggs from a growth-selected line of Large White turkeys (F line; Nestor, 1977) were incubated and hatched at the Ohio Agricultural Research and Development Center, Wooster, Ohio. On the morning of Day 28 of incubation, 240 mixed sex poults were removed from the hatcher and wing-banded. Immediately following wing banding, the poults were taken to an adjacent building and randomly allocated to 40 pens in two heated battery brooders4. Poults in one-half of the pens were allowed immediate access to feed and water (FED), whereas feed and water

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Corn Meat and bone meal Corn gluten meal Fish meal 48% soybean meal 44% soybean meal Wheat middlings Animal-vegetable fat MCT1 Dicalcium phosphate Ground limestone Sodium chloride DL-methionine L-lysine Premix2,3,4 Dietary analyses MEn, calculated kcal/kg CP, determined5 CP, determined6 Lysine, calculated Methionine, calculated TSAA, calculated

posthatch metabolism of poults. Rosebrough and Begin (1976) reported that poults fed a high-fat diet had increased glucose-6-phosphatase activity when compared with poults fed a high-carbohydrate diet. The high-fat diet sustained the gluconeogenic state of the poult without dramatically shifting the metabolic state toward glycolysis. Digestion and absorption of dietrary fat by young poults is considerably less than at older ages (Sell et al., 1986); however, diets with excessively high levels of fat might induce hypoglycemia, ketonemia, and reduced hepatic glycogen concentrations (Brambila and Hill, 1966). Moran (1978) reported that poults fed a nutrient-dense diet (protein and energy fed at 107% of NRC recommendations) had increased BW and feed efficiency at 2 wk of age, but early mortality was concomitantly increased. Donaldson and Christensen (1994) reported that a high carbohydrate diet (51% available carbohydrate; 20% CP) substantially increased hepatic glycogen concentrations compared with a normal starting ration (34% available carbohydrate; 28% CP) after 1 d of feeding. Synthetic medium-chain triglycerides containing predominantly medium-chain fatty acids (MCFA; C6:0 to C12:0) represent an interesting alternative energy source for the young poult. Largely because of their size and solubility characteristics, MCFA can be absorbed without the need for bile acids and the hydrolytic activity of pancreatic lipase (Bach and Babayan, 1982). Metabolically, MCFA can be transported across the mitochondrial membrane independent of the carnitine transport system, thereby providing a preferential source of acetyl CoA (Bach and Babayan, 1982). In chicks, MCFA have been shown to have beneficial effects on overall growth during the first few weeks after hatch (Mabayo et al., 1993). The objectives of the experiments reported herein were to determine the effects of delayed placement and energy source on poult growth, carbohydrate metabolism, and overall metabolic homeostasis during the first 2 wk of age.

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Experiment 2 Commercial turkey eggs (Nicholas Large White6) were obtained and incubated in a Petersime incubator4. On the morning of Day 28 of incubation, 280 male poults were wing-banded and randomly allocated to 40 pens in the same battery brooders described for Experiment 14. The diets (CHO and FAT) and feeding regimens (FED and WH) were similar to those described for Experiment 1. Ten replicate pens were utilized per feeding regimen and dietary treatment. One poult per pen was randomly selected for liver and blood measurements at 0, 2, and 5 DPF. Blood was collected in a manner similar to Experiment 1, and plasma was analyzed for glucose (Glucose Oxidase5). Immediately following blood collection, livers from 0 and 2 DPF poults were excised, weighed, and frozen in liquid nitrogen. Livers were stored at −80 C for later determination

5 Glucose Oxidase, Procedure No. 315, β-HBA, Procedure No. 310UV, Sigma Chemical Co., St. Louis, MO 63178-9916. 6 Nicholas Turkey Breeding Farms, Sonoma, CA 95476. 7 Captex 8000, Capital City Products, Columbus, OH 43215-1141.

TABLE 2. Determined total lipid and fatty acid composition of diets containing a high proportion of carbohydrate supplied by corn (CHO; 60% of diet) or 10% supplemental fat from an animal-vegetable fat blend (FAT) or fat containing medium-chain triglyceride (MCT) (Experiment 3)

Total lipid, % of diet Fatty acid, % of total methyl esters C8:0 C10:0 C12:0 C14:0 C16:0 C16:1 C18:0 C18:1 C18:2 (n-6) C18:3 (n-3) Other

CHO

FAT

MCT

5.12

12.03

11.32

ND1 ND 3.28 6.65 28.87 6.46 6.83 20.86 25.03 1.04 1.01

0.30 ND 3.83 3.45 25.57 1.60 18.75 29.03 12.41 0.79 4.28

75.90 0.45 2.55 1.32 3.30 0.60 0.73 3.09 10.60 1.02 0.44

ND = fatty acid was not detected.

1

of hepatic glycogen content according to the method of Dreiling et al. (1987). All remaining poults were individually weighed at 0, 5, and 13 DPF. Daily feed consumption was determined for each pen from 2 to 13 DPF. At 13 DPF, all remaining poults were weighed and killed by cervical dislocation; the right half of the Pectoralis major breast muscle was excised and weighed.

Experiment 3 Commercial turkey eggs6 were incubated and hatched at the Ohio Agricultural Research Development Center. On the morning of Day 28 of incubation, all poults were sexed by a commercial sexer, and 360 males were wingbanded and randomly allocated to 30 pens in the same batteries described for the previous experiments. The same feeding regimen treatments (FED and WH) and diets (CHO and FAT) were similar to those described for Experiments 1 and 2 together with a third experimental diet (MCT; Table 1) containing a commercial source of medium-chain triglyceride7 (10%) in place of the animalvegetable fat blend. The lipid content of each feed sample was determined by extraction with chloroform:methanol (2:1) as reported by Folch et al. (1957). The fatty acid composition of feed samples was determined by the direct methylation procedure described by Sukhija and Palmquist (1988). Total lipid and fatty acid composition of diets are presented in Table 2. Poults were individually weighed at 0, 5, and 13 DPF. Feed consumption was determined daily for each pen from 1 to 4 DPF. Livers and blood were collected from 10 poults per diet and feeding regimen at 0, 2, and 5 DPF. Plasma and livers were analyzed for glucose and glycogen, respectively, as described in Experiment 2. Plasma from the WH poults was analyzed further for βhydroxybutyrate5 (β-HBA) at 0, 2, and 5 DPF. A glucose challenge assay was conducted at 4 and 7 DPF. At 4 DPF, 10 poults per diet and feeding regimen were feed deprived for 12 h and injected i.m. (Pectoralis major) with 0.5 mL 50% (wt/vol) glucose solution in 0.9%

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were withheld for 48 h (WH) from the remaining pens. All age comparisons in the present experiments are defined in terms of the initiation of ad libitum access to feed and water or days postfeeding (DPF), which would represent the onset of the production period, or Day 0 in a commercial situation. Chronologically, the day of hatch would represent 0 DPF, and 2 d after hatch would represent 2 DPF in FED poults. In WH poults, however, 0 DPF would occur 2 d posthatch, so that poults in this treatment would always be chronologically 2 d older than FED poults at the same DPF. Two experimental diets were formulated to contain a high proportion of corn (CHO; 60.7%) or 10% supplemental animal-vegetable fat (FAT; Table 1). The objective of using the high quantity of corn was to provide a practical source of carbohydrate to this treatment group. The CHO and FAT diets in Experiments 1 and 2 contained, by analysis, 25.6 and 25.8% CP and 3,082 and 3,049 kcal ME/kg (calculated), respectively. Ten replicate pens were used per feeding treatment (FED and WH) and diet (CHO and FAT). An additional 45 poults were kept in extra pens and had feed and water withheld for plasma measurements at 0, 24, and 48 h posthatch. Body weights were recorded individually at hatch (FED) or on the initial day of feed and water (WH). At 5 DPF, one poult per pen was randomly selected, weighed, killed by cervical dislocation, and used for liver weight determination. This procedure resulted in 10 poults per feeding regimen and diet. All remaining poults were individually weighed at 5 and 12 DPF. At 0, 24, and 48 h, 15 of the extra WH poults were also weighed and killed by decapitation. Blood was collected into individual heparinized tubes and centrifuged. The plasma was frozen for later determination of glucose concentration (Glucose Oxidase5).

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saline. At 0, 30, and 60 min postinjection, blood samples were collected from the brachial vein into heparinized capillary tubes. Plasma was collected after centrifugation and frozen for later glucose determinations (Glucose Oxidase5).

Statistical Analyses Data were analyzed by two-way analysis of variance using the General Linear Model of SAS威 (SAS Institute, 1986). The main effects tested were diet, feeding regimen (FED and WH), and their interaction. In Experiment 3, differences between diets were tested using Duncan’s multiple range test when the significance of the main effect of diet was ≤0.05.

and WH poults at 0 DPF. Feeding markedly increased hepatic glycogen concentrations by 2 DPF, and poults fed the CHO diet had higher glycogen concentrations than poults fed the FAT diet (P ≤ 0.002). Feeding regimen did not influence hepatic glycogen concentrations at 2 DPF. Plasma glucose concentrations were lower in WH poults at 0 DPF than in FED poults (P ≤ 0.05; Table 4). At 2 and 5 DPF, however, WH poults had higher plasma glucose concentrations. At 2 DPF, much of this difference could be attributed to the WH poults fed the CHO diet (feeding regimen by diet interaction; P ≤ 0.05). Of the poults sampled at 2 DPF, 50% of the WH poults fed the CHO diet had plasma glucose concentrations in excess of 500 mg/dL.

Experiment 3 Experiment 1 At 5 DPF, FED poults were heavier than WH poults (97.5 vs 94.8 ± 1.1 g; mean ± SEM; P ≤ 0.05), and poults fed the CHO diet were heavier than poults fed the FAT diet (103.1 vs 89.7 ± 1.1 g; P ≤ 0.05). No differences because of feeding regimen or diet were observed at 12 d of age (data not shown). At 5 DPF, there was an increase in mean liver weight in poults fed the CHO diet compared with those fed the FAT diet (4.10 vs 3.29 ± 0.12 g; P ≤ 0.05). No interactions of diet by feeding regimen were observed for BW or liver weight (P > 0.05). In those poults sampled during the initial feed and water withdrawl period, no significant differences were noted in plasma glucose concentrations and averaged 283.6, 280.6, and 280.3 ± 11.7 mg/dL at 0, 24, and 48 h after hatching, respectively.

Experiment 2 The interaction of diet by feeding regimen was not significant (P > 0.05) so that only the main effect means of poult BW at 0, 5, and 13 DPF are presented in Table 3. The WH poults were lighter than FED poults at 0 and 5 DPF (P ≤ 0.05). As in Experiment 1, poults fed the CHO diet were heavier at 5 DPF (P ≤ 0.05), but, at 13 DPF, poults fed the FAT diet were heavier (P ≤ 0.05). At 13 DPF, the relative weight of the Pectoralis major was also higher in poults fed the FAT diet (5.2 vs 4.6% ± 0.07; P ≤ 0.05). Feed intake by poults fed the CHO diet was greater between 3 and 6 DPF (P ≤ 0.05; Table 3). After 7 DPF, however, poults fed the FAT diet consumed more feed (P ≤ 0.05), and this paralleled the increase in BW observed at 13 DPF. At 0, 2, and 5 DPF, liver weights were lighter in WH vs FED poults (P ≤ 0.05; Table 4). Most of the effect caused by feeding regimen at 5 DPF was due to the increase in liver weight in poults fed the CHO diet, which resulted in a feeding regimen by diet interaction (P ≤ 0.02). At 2 DPF, however, liver weight in WH poults was heavier than that in FED poults (P ≤ 0.05). Hepatic glycogen concentrations were nearly depleted prior to feeding in FED

Following the initial 2-d feed deprivation, WH poults were inadvertently given access to water for 1.5 h prior to weighing; therefore, BW differences between FED and WH poults at 0 DPF were significant (P ≤ 0.05; Table 5) but were not as great as the differences observed in Experiment 2. The FED poults were heavier than the WH poults at 5 DPF, but not at 13 DPF. Poults fed the FAT diet were heavier than poults fed the CHO or MCT diet at 5 DPF (P ≤ 0.05). At 13 DPF, poults fed the FAT and MCT diets were heavier than those fed the CHO diet (P ≤ 0.05). As in Experiment 2, the relative weight of the

TABLE 3. Body weight and feed consumption of poults fed diets containing a high proportion of carbohydrate from corn (CHO; 60% of diet) or 10% supplemental fat from an animal-vegetable fat blend (FAT) immediately after hatching (FED) or after a 48-h delay in access to feed and water (WH) (Experiment 2) Days post-feeding Measurement

Treatment

BW

Dietary regimen WH FED SEM Diet CHO FAT SEM

0

5

13 (g)

46.08*,1 55.10 0.01

105.5* 109.2 1.2

283.8 281.5 4.5

... ... ... 3 to 6

111.1† 103.6 1.2 7 to 10

270.4† 294.9 4.5 11 to 13

(g/bird per period) Feed consumption

Dietary regimen WH FED SEM Diet CHO FAT SEM

57.1 57.5 0.3

113.8* 101.4 0.6

97.4* 105.1 0.7

60.8† 53.8 0.3

102.4† 112.8 0.6

93.4† 109.1 0.6

*Main effect means of dietary regimen within 1 d postfeeding are different (P ≤ 0.05). † Main effect means of diet within 1 d postfeeding are different (P ≤ 0.05). 1 Means represent 10 pens per diet and dietary regimen (four to seven poults per pen).

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RESULTS

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METABOLIC STATUS OF THE POSTHATCH POULT TABLE 4. Liver weight, liver glycogen concentration, and plasma glucose concentration of poults fed diets containing a high proportion of carbohydrate from corn (CHO; 60% of diet) or 10% supplemental fat from an animal-vegetable fat blend (FAT) immediately after hatching (FED) or after a 48-h delay in access to feed and water (WH) (Experiment 2)

Measurement

Dietary regimen

Liver weight

WH

Days postfeeding 0

2

5

CHO FAT CHO FAT

1.36*,1 ... 1.45 ... 0.03

3.37* 2.98 2.72 2.59 0.14 (mg/g)

CHO FAT CHO FAT

4.00* ... 6.93 ... 0.90

131.89† 69.38 103.29 74.51 13.53

CHO FAT CHO FAT

264.9*,1 ... 284.5 ... 6.2

(g)

FED SEM Liver glycogen

WH FED SEM

3.54*,† 3.50 4.61 3.62 0.20 . . . . .

. . . . .

. . . . .

(mg/dL) Plasma glucose

WH FED SEM

482.1*,†,‡ 283.5 276.6 309.5 34.5

358.3*,† 300.8 289.0 278.1 20.7

*Main effect means of dietary regimen within 1 d postfeeding are different (P ≤ 0.05). † Main effect means of diet within 1 d postfeeding are different (P ≤ 0.05). ‡ The interaction of dietary regimen and diet within 1 d postfeeding is significant (P ≤ 0.05). 1 Means represent 20 poults per dietary regimen and diet.

Pectoralis major at 13 DPF was greater in poults fed the FAT and MCT diets than in poults fed the CHO diet (5.2, 5.3, and 4.3%, respectively; P ≤ 0.05). The WH poults consumed more feed on the first day of access to feed than FED poults (P ≤ 0.05), but not at older ages (Table 5). Most of the difference in feed consumption between diets at 1 and 2 DPF could be attributed to the WH poults fed the CHO diet (time of placement by diet interaction, P ≤ 0.05). At 3 and 4 DPF, poults fed the FAT diet consumed more than those fed the MCT diet (P ≤ 0.05), but not the CHO diet. Feeding regimen did not significantly affect liver weight at 0, 2, or 5 DPF (Table 6). Much of the dietary effect observed at 2 and 5 DPF was attributed to poults fed the CHO diet vs the MCT or FAT diets. Hepatic glycogen concentration in both FED and WH poults was nearly deplete at 0 DPF. Poults fed the CHO diet had greater hepatic glycogen concentrations at 2 and 5 DPF (P ≤ 0.05), similar to the results from Experiment 2. In addition, WH poults had less glycogen than FED poults at 5 DPF (P ≤ 0.0001). The initial 2-d feed deprivation resulted in decreased plasma glucose concentrations in WH poults at 0 DPF but not at later ages (P ≤ 0.02; Table 6), similar to what was observed in Experiment 2. Thirty percent of the WH poults fed the CHO diet had glucose concentrations over 500 mg/dL at 2 DPF; however, the main effect of diet was not significant (P ≤ 0.07). Neither diet nor time of

TABLE 5. Body weight and feed consumption of poults fed diets containing a high proportion carbohydrate supplied by corn (CHO; 60% of diet) or 10% supplemental fat from an animal-vegetable fat blend (FAT) or fat containing medium-chain triglyceride (MCT) immediately after hatching (FED) or after a 48-h delay in access to feed and water (WH) (Experiment 3) Days postfeeding Measurement

Treatment

BW

Dietary regimen WH FED SEM Diet CHO FAT MCT SEM

0

5

13 (g)

51.5*,1 56.5 0.2

109.3* 114.5 1.0

308.2 302.5 5.4

. . . .

110.2b 115.4a 110.1b 0.8 2

275.3b 324.3a 316.5a 3.6 3

.. .. .. .. 1

4

(g/bird per d) Feed consumption

Dietary regimen WH FED SEM Diet CHO FAT MCT SEM

10.58* 8.30 0.31

8.50 8.41 0.17

11.36 11.56 0.24

11.80 11.91 0.19

11.52a 8.40b 8.40b 0.20

9.04a 8.33a,b 7.99b 0.23

11.69a 12.22a 10.48b 0.31

11.96a,b 12.38a 11.22b 0.25

*Main effect means of dietary regimen within 1 d postfeeding are different (P ≤ 0.05). a,b Diet means within 1 d postfeeding with different superscripts are different (P ≤ 0.05). 1 Means represent five pens per dietary regimen and diet (eight to 12 poults per pen).

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Diet

placement significantly affected plasma glucose concentrations at 5 DPF. Because of the large proportion of WH poults with plasma glucose concentrations over 500 mg/ dL, plasma samples from all WH poults were also analyzed for β-HBA concentrations at 0, 2, and 5 DPF. Plasma concentrations of β-HBA decreased with increasing age of the poult (22.5, 9.2, and 5.4 mg/dL at 0, 2, and 5 DPF). The additional 2-d feed deprivation did not significantly increase plasma β-HBA concentrations (plasma concentrations of β-HBA at hatch of poults were 25.22 mg/dL). Diet did not significantly affect plasma β-HBA concentrations in WH poults at 2 or 5 DPF. When poults were subjected to the glucose challenge at 4 and 7 DPF, poults fed the CHO diet had lower plasma glucose concentrations at 0, 30, and 60 min postinjection (P ≤ 0.05; Table 7). Differences caused by feeding regimen were not apparent at 0 or 30 min postinjection. At 60 min postinjection, however, glucose concentrations in WH poults were 67.8 mg/dL higher than in the FED poults. Similarly, when poults were subjected to the glucose challenge at 7 DPF, the WH poults had plasma glucose concentrations 50.5 mg/dL greater than FED poults at 60 min postinjection.

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TABLE 6. Liver weight, liver glycogen concentration, and plasma glucose concentrations of poults fed diets containing a high proportion of carbohydrate from corn (CHO; 60% of diet) or 10% supplemental fat from an animal-vegetable fat blend (FAT) or fat containing medium-chain triglyceride (MCT) immediately after hatching (FED) or after a 48-h delay in access to feed and water (WH), Experiment 3 Days postfeeding Measurement

Ditary regimen

Diet

Liver weight

WH

CHO FAT MCT CHO FAT MCT

0

2

5 (g)

FED

. . . .

SEM

1.381 .. .. 1.50 .. .. 0.48

3.43† 2.89 2.49 3.15 2.81 2.83 0.14

3.96† 3.73 4.00 4.61 3.73 4.06 0.22

(mg/g) WH FED

CHO FAT MCT CHO FAT MCT

SEM Plasma glucose

WH FED SEM

CHO FAT MCT CHO FAT MCT

. . . .

4.59* .. .. 1.92 .. .. 0.59

252.5* ... ... 274.2 ... ... 6.11

157.2† 81.7 45.8 151.8 72.8 64.5 11.1 (mg/dL) 425.1 340.3 316.1 335.2 316.9 335.3 25.61

43.5*,† 9.1 2.9 83.4 21.2 52.5 9.96 370.7 330.6 328.7 333.8 331.6 330.6 26.7

*Main effect means of dietary regimen within 1 d postfeeding are different (P ≤ 0.05). † Main effect means of diet within 1 d postfeeding are different (P ≤ 0.05). 1 Means represent 11, 10, and 10 poults per dietary regimen and diet at 0, 2, and 5 d postfeeding, respectively.

TABLE 7. Glucose tolerance assay1 of poults 4 and 7 d postfeeding (DPF) of diets containing a high proportion of carbohydrate from corn (CHO; 60% of diet) or 10% supplemental fat from an animalvegetable fat blend (FAT) or fat containing medium-chain triglyceride (MCT) immediately after hatching (FED) or after a 48-h delay in access to feed and water (WH) (Experiment 3) Time postinjection

DISCUSSION Prior to hatch, yolk sac lipid and protein are metabolized, and glucose is derived via gluconeogenesis. Some authors have concluded that, after hatch, the residual yolk sac serves as an energy reserve for the poult before complete resorption occurs at 5 to 6 d of age (Phelps et al., 1987b). The yolk sac of the poult only contains 0.6 to 2.5 g of residual lipid at hatch, of which up to 120 mg is triglyceride (Ding et al., 1995; Ding and Lilburn, 1996). This triglyceride would potentially supply only 8 to 9 kcal ME to the poult after hatching (Lilburn, 1998). Poults fed the CHO diet had increased feed intake and heavier BW through 5 DPF, after which poults fed the CHO diet consumed significantly less feed than those fed the FAT diet. The CHO diet contained a high proportion of corn to achieve the desired level of carbohydrate and resulted in the utilization of high amounts of fish meal (22%) to meet the NRC (1994) protein and amino acid requirements for starting poults. In other reports in the literature, the inclusion of fish meal at 10 to 15% had no adverse effects on feed intake, and the poults used in the experiments reported herein exhibited no other symptoms of gizzerosine toxicity (i.e., gizzard erosion) (Alenier

DPF

Treatment

4

Dietary regimen WH FED SEM Diet CHO FAT MCT SEM Dietary regimen WH FED SEM Diet CHO FAT MCT SEM

0 min

30 min

60 min

(plasma glucose, mg/dL)

7

231.62 229.5 3.4

561.8 498.3 13.3

540.2* 472.4 17.4

210.4b 242.7a 236.4a 2.7

450.4b 559.4a 567.2a 12.3

409.3b 547.8a 548.9a 15.8

241.0 252.0 5.4

541.2 535.7 14.4

499.9* 449.4 13.7

232.4b 255.7a 251.4a 6.6

472.5b 573.2a 563.9a 17.7

408.1b 513.3a 496.7a 16.8

*Main effect means of dietary regimen within a time postinjection are different (P ≤ 0.05). a,b Diet means within a time postinjection with different superscripts are different (P ≤ 0.05). 1 Poults were fasted for 12 h prior to an i.m. injection of 250 mg glucose. 2 Means represent 10 poults per dietary regimen and diet.

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Liver glycogen

and Combs, 1981; Cantor and Johnson, 1983; Sugahara, 1995). There is a perception within commercial practice that fat supplementation should be minimized in diets fed to young poultry, and there is body of literature that circumstantially supports this view, at least from a digestibility standpoint (Whitehead and Fisher, 1975; Salmon, 1977; Sell et al., 1986). In a companion paper, Turner et al. (1999) reported the apparent lipid digestibility of the FAT diet to be 71% between 3 and 11 d of age. The reduction in overall lipid digestibility was attributed to the low apparent digestibility of C16:0 and C18:0 fatty acids (52.7 and 26.8%, respectively). However, the apparent digestibility of the polyunsaturated fatty acids and MCFA in the FAT and MCT diets was consistently high (>80 and ≥95%, respectively). Previous reports have noted that poults fed starter diets containing 8 to 10% animal-vegetable fat were heavier and had improved feed efficiency at 2 wk of age (Moran, 1978; Sell et al., 1986), similar to the results of the current experiments. The relative weight of the Pectoralis major represented muscle protein accretion and was increased at 13 DPF in poults fed the FAT and MCT diets. This increased muscle weight could have been the result of improved efficiency of protein utilization in poults fed the FAT and MCT diets or simply a function of increased protein intake in those poults fed the FAT diet.

METABOLIC STATUS OF THE POSTHATCH POULT

ately posthatch. Initial feed deprivation resulted in only a short-term restriction in growth; however, prolonged metabolic effects were still evident 7 d postfeeding. Feeding the CHO diet improved BW gain and feed intake only through the first 5 DPF, after which a high-fat diet (FAT or MCT) had the most beneficial effects. The presence of elevated plasma glucose and hepatic glycogen concentrations in CHO-fed poults following access to feed may provide some insight into the depressed growth and feed intake observed after 5 DPF. The current experiments demonstrate that supplemental fat sources may ease the metabolic shift toward glycolysis after hatching, thereby improving growth through 2 wk of age.

REFERENCES Alenier, J. C., and G. F. Combs, Jr., 1981. Effects of feed palatability of ingredients believed to contain unidentified growth factors in poultry. Poultry Sci. 60:215–224. Al-Rawashdeh, O. F., S. Q. Lafi, N. Q. Hailat, T. A. Abdul-Aziz, K. I. Ereifij, and A.Y.M. Nour, 1995. Effect of feed deprivation on the blood levels of glucose, β-hydroxybutyrate, triglycerides, and cholesterol and on body weight and yolk sac weight in one-day-old broiler chicks. Acta Vet. 45:175–186. Bach, A. C., and V. K. Babayan, 1982. Medium-chain triglycerides: An update. Am. J. Clin. Nutr. 36:950–962. Best, E. E., 1966. the changes of some blood constituents during the initial post-hatching period in chickens-II. Blood total ketone bodies and the reduced glutathione/ketone body relationship. Br. Poult. Sci. 7:23–28. Brambila, S., and F. W. Hill, 1966. Comparison of neutral fat and free fatty acids in high lipid-low carbohydrate diets for the growing chicken. J. Nutr. 88:84–92. Cantor, A. H., and T. H. Johnson, 1983. Effects of unidentified growth factor sources on feed preference of chicks. Poultry Sci. 62:1281–1286. Ding, S. T., and M. S. Lilburn, 1996. Characterization of changes in yolk sac and liver lipids during embryonic and early posthatch development of turkey poults. Poultry Sci. 75:478–483. Ding, S. T., K. E. Nestor, and M. S. Lilburn, 1995. The concentration of different lipid classes during late embryonic development in a randombred turkey population and a subline selected for increased body weight at sixteen weeks of age. Poultry Sci. 74:374–382. Donaldson, W. E., and V. L. Christensen, 1991. Dietary carbohydrate level and glucose metabolism in turkey poults. Comp. Biochem. Physiol. 98:347–350. Donaldson, W. E., and V. L. Christensen, 1994. Dietary carbohydrate effects on some plasma organic acids and aspects of glucose metabolism in turkey poults. Comp. Biochem. Physiol. 109A:423–430. Donaldson, W. E., V. L. Christensen, and K. K. Krueger, 1991. Effects of stressors on blood glucose and hepatic glycogen concentrations in turkey poults. Comp. Biochem. Physiol. 100A:945–947. Dreiling, C. E., D. E. Brown, L. Casale, and L. Kelly, 1987. Muscle glycogen: Comparison of iodine binding and enzyme digestion assays and application to meat samples. Meat Sci. 20:167–177. Folch, J., M. Lees, and G. H. Sloan-Stanley, 1957. A simple method for the isolation and purification of total lipids from animal tissues. J. Biol. Chem. 226:497–509. Freeman, B. M., and M. A. Vince, 1974. Development of the Avian Embryo. Chapman and Hall, London, UK. Goodridge, A. G., 1968. Conversion of [U-14C] glucose into carbon dioxide, glycogen, cholesterol and fatty acids in liver slices from embryonic and growing chicks. Biochem. J. 108:655–661.

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In the FED poults at hatch and WH poults at 0 DPF, hepatic glycogen stores were nearly depleted, similar to other reports in the literature (Rosebrough et al., 1978; John et al., 1988). Therefore, any statistical differences at this age may not be biologically relevant. A normal avian liver contains 25 to 50 mg glycogen/g (Hazelwood, 1976), and the hepatic glycogen concentration at 2 DPF in poults fed the FAT and MCT diets was close to this general range. Poults fed the CHO diet, however, had a twofold increase in glycogen, concomitant with higher circulating glucose concentrations. By 5 DPF, the mean hepatic glycogen concentrations in poults fed the CHO diet was close to the 25- to 50-mg/g range, yet the WH poults fed the FAT and MCT diets had markedly lower concentrations. We hypothesize that the low hepatic glycogen concentrations at 5 DPF in the WH poults fed the FAT and MCT diets may represent a suboptimal level of glycogen reserves. Poults fed the CHO diet had significantly increased plasma glucose concentrations at 2 DPF, particularly those that were WH. Thirty to fifty percent of the WH poults had glucose concentrations in excess of 500 mg/dL at this time, concomitant with increased hepatic glycogen concentrations. The results reported here with a diet containing a practical source of carbohydrate (corn) is similar in scope to the results of Donaldson and Christensen (1991), who also observed increased circulating glucose concentrations 1 d posthatch with diets containing 15 to 50% carbohydrate supplied as corn starch. In that study, glucose-6-phosphatase, an intermediate enzyme in glycogen catabolism, decreased as dietary carbohydrate increased. In the present study, plasma glucose concentrations remained elevated at 5 DPF; however, variability precluded any significant differences from being observed. Whether the elevated plasma glucose concentrations associated with “loading” of hepatic glycogen stores is beneficial or detrimental is open to question. Circulating β-HBA was elevated at hatch, similar to that observed by Best (1966). Concentrations did not increase any further in WH poults; it was, however, similar to what has been reported in chicks (Al-Rawashdeh et al., 1995). Whether the concentrations at hatch are detrimental or merely sufficient to sustain the posthatch poult is uncertain. The concentrations of β-HBA decreased after feeding and continued to decline through 5 DPF. Although MCFA are reported to be ketogenic (Bach and Babayan, 1982), the 10% inclusion rate of MCT in the diet did not affect circulating concentrations of β-HBA. At 4 and 7 DPF, WH poults were unable to regulate plasma glucose concentrations 60 min after a glucose challenge. Poults fed the CHO diet had reduced plasma glucose concentrations at 30 and 60 min postinjection compared with those fed the FAT and MCT diets, thereby suggesting that the CHO diet might have preconditioned these poults with respect to glucose metabolism, although the exact mechanism(s) were not investigated. The main objectives of these experiments were to determine the effects of a 2-d delay in feed access and primary nutrient source on poult growth and metabolism immedi-

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TURNER ET AL. Phelps, P. V., F. W. Edens, and V. L. Christensen, 1987a. The posthatch physiology of the turkey poult-I. Growth and development. Comp. Biochem. Physiol. 86A:739–743. Phelps, P. V., F. W. Edens, and R. P. Gildersleeve, 1987b. The posthatch physiology of the turkey poult-III. Yolk depletion and serum metabolites. Comp. Biochem. Physiol. 87A:409– 415. Romanoff, A. L., 1960. The Avian Embryo. Structural and Functional Development. MacMillan Co., New York, NY. Rosebrough, R. W., and J. J. Begin, 1976. The effect of nonprotein energy sources on the ability of the chick to synthesize glucose-6-phosphatase. Poultry Sci. 55:1031–1035. Rosebrough, R. W., E. Geis, K. Henderson, and L. T. Frobish, 1978. Glycogen metabolism in the turkey embryo and poult. Poultry Sci. 57:747–751. Salmon, R. E., 1977. Effects of age on the absorption of fat by turkeys fed mixtures of beef fat and rapeseed oil. Can. J. Anim. Sci. 57:427–431. SAS Institute, 1986. SAS威 User’s Guide: Statistics. 1986 Edition. SAS Institute, Inc., Cary, NC. Sell, J. L., A. Krogdahl, and N. Hanyu, 1986. Influence of age on utilization of supplemental fats by young turkeys. Poultry Sci. 65:546–554. Sugahara, M., 1995. Black vomit, gizzard erosion and gizzerosine. World’s Poult. Sci. J. 51:293–306. Sukhija, P. S., and D. L. Palmquist, 1988. Rapid method for determination of total fatty acid content and composition of feedstuffs and feces. J. Agric. Food Chem. 36:1202–1206. Turner, K. A., T. J. Applegate, and M. S. Lilburn, 1999. Effects of feeding high carbohydrate or fat diets. 2. Apparent digestibility and apparent metabolizable energy of the posthatch poult. Poultry Sci. (In press). Whitehead, C. C., and C. Fisher, 1975. The utilization of various fats by turkeys of different ages. Br. Poult. Sci. 16:481–485.

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Hazelwood, R. L., 1976. Carbohydrate metabolism. Pages 210– 232 in: Avian Physiology. P. D. Sturkie, ed. Springer-Verlag, New York, NY. John, T. M., J. C. George, and E. T. Moran, Jr., 1988. Metabolic changes in pectoralis muscle and liver of turkey embryos in relation to hatching: Influence of glucose and antibiotictreatment of eggs. Poultry Sci. 67:463–469. Lilburn, M. S., 1998. Practical aspects of early nutrition for poultry. J. Appl. Poult. Res. 7:420–424. Mabayo, R. T., M. Furuse, K. Kita, and J. Okumura, 1993. Improvement of dietary protein utilization in chicks by medium chain triglyceride. Br. Poult. Sci. 34:121–130. Moran, E. T., Jr., 1978. Performance and carcass quality of broiler tom turkeys subjected to a post-hatch fast and offered starting rations of different nutrient compositions. Can. J. Anim. Sci. 58:233–243. Moran, E. T., Jr., 1989. Effects of posthatch glucose on poults fed and fasted during yolk sac depletion. Poultry Sci. 68:1141–1147. Moran, E. T., Jr., 1990. Effects of egg weight, glucose administration at hatch, and delayed access to feed and water on the poult at 2 weeks of age. Poultry Sci. 69:1718–1723. Moran, E. T., Jr., and B. S. Reinhart, 1980. Poult yolk sac amount and composition upon placement: Effect of breeder age, egg weight, sex and subsequent change with feeding and fasting. Poultry Sci. 59:1521–1528. National Research Council, 1994. Nutrient Requirements of Poultry. 9th rev. ed. National Academy Press, Washington, DC. Nestor, K. E., 1977. Genetics of growth and reproduction in the turkey. 5. Selection for increased body weight alone and in combination with increased egg production. Poultry Sci. 56:337–347.