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Lysine Supplementation of Low-Protein Diets for Broiler Breeder Males1
Lysine Supplementation of Low-Protein Diets for Broiler Breeder Males1 W. H. REVINGTON,2 E. T. MORAN, JR., S. F. BILGILI, and R. D. BUSHONG Poultry Science Department, Alabama Agricultural Experiment Station, Auburn University, Alabama 36849-5416 (Received for publication May 10, 1991) ABSTRACT Two experiments were conducted to assess the impact of supplemental L-lysine HC1 on N balance in broiler breeder males fed 8% CP corn-based diets (3,220 kcal ME„/kg; .15% supplemental DL-methionine; .24% basal lysine). In Experiment 1, 78-wk-old males were fed the basal diet with either 0, .05, .10, or .25% supplemental L-lysine HC1. Birds were allowed to eat for 1 h each day to a maximum intake of 325 kcal MEj, per bird per day. Total excreta were collected for 8 consecutive days. Nitrogen retention and balance were not different among treatments (P>.05) and responded neither linearly nor quadratically to dietary lysine level. Removing the variation due to differences in N intake with analysis of covariance did not change the response. In Experiment 2, 30-wk-old males were fed the same basal diet with supplemental lysine levels of 0, .15, .30, .45, .60, and .75% L-lysine HC3 for 5 consecutive days. Nitrogen balance and retention were different among diets, and both variates responded linearly to increases in dietary lysine. Removing the variation due to differences in N intake removed treatment effects, however, suggesting that at least part of the difference was the result of variable levels of intake. Regression analysis indicated a significant linear increase in both N balance and retention with increasing dietary lysine level (R2 = .82). These results suggest that young broiler breeder males can make better use of the protein of corn if supplemental lysine is provided. However, older birds do not demonstrate improved N balance as a result of supplemental dietary lysine. {Key words: broiler breeder male, protein, lysine, nitrogen retention, age) 1992 Poultry Science 71:323-330
INTRODUCTION Wilson et al, (1987a,b) reported improved reproductive performance in broiler breeder males fed low-protein feeds (12% CP). Although reports are inconclusive, there is some evidence to suggest that even lower protein levels can be used to improve the reproductive performance of males (Leveille and Fisher, 1958; Arscott and Parker, 1963; Wilson et
Alabama Agricultural Experiment Station Journal Number 12-902498P. 2 Present address: New-Life Mills, Ltd., 1400 Bishop St., Cambridge, ON, N1R 6W8, Canada.
al., 1965; Wilson et al., 1987b). Success of low-protein regimens seems to depend on provision of balanced dietary protein, and on the implementation of such regimens subsequent to the onset of sexual maturity (Wilson et ah, 1971). Practical diets formulated to low levels of dietary protein are likely to have a high proportion of grain and a high proportion of energy relative to protein. They may also be low in lysine, particularly when corn is the primary ingredient. Revington et al. (1991a) fed caged breeder males either an all-corn diet (AC, 8% CP) or a standard corn and soybean meal diet (ST, 12% CP) at a rate of 325 kcal MEn per bird per day from 24 to 68 wk of
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age. Although BW of males fed the AC diet was significantly less than BW of birds receiving the ST diet, there was no apparent detriment to reproductive performance. Carcasses from birds fed 8% CP were proportionally fatter than those from birds that received the 12% CP control diet. Furthermore, Revington et al. (1988) showed that N intake paralleled N retention as dietary regimens were proportionally shifted from ST to AC. However, the relative proportion of N retained by birds was less for the 8% CP diet than for the 12% CP feed despite equal energy intakes and positive N balance. Taken together, these results suggest the possibility of improving protein utilization by supplementing corn-based diets with specific essential amino acids. Because the lysine content of corn is low relative to energy, and this amino acid is easily supplemented in free form, two experiments were conducted to determine the effect of supplemental lysine on N utilization in low-protein, all-corn diets. MATERIALS AND METHODS Experiment 1 Sixteen 78-wk-old broiler breeder males (Ross) were divided into four groups of approximately equal average BW. Each group was assigned to a set of four individual male breeder cages in a lighttight breeder facility. Water was available for ad libitum intake through nipple drinkers and the birds received 15 h of light/day during the experiment. Temperature averaged 25 C throughout the experimental period. Each group was randomly assigned to one of four dietary treatments consisting of different levels of supplemental L-lysine HC1 at the expense of corn (.05, .10, .25% Llysine H O ) . The basal diet (0% added Llysine HC1; Table 1) was formulated to approximate the amino acid requirements as reported by Leveille et al. (1960) for the Single Comb White Leghorn (SCWL) male. Birds received their respective test diets for 3 days prior to formal excreta collections, and for 45 min/day. All diets were fed to provide approximately 325 kcal AME„ per bird per day. Actual intake was determined
TABLE 1. Composition of the basal diet fed to caged broiler breeder males Ingredients and composition Ground corn DL-methionine Dicalcium phosphate Limestone Salt Vitamin-mineral mix1 Total Assayed composition CP, % MEn, kcal/kg
Percentage 96.00 .15 1.25 1.75 .35 .50 100.00 82 3,070
Supplied the following to each kilogram of finished feed: vitamin A palmitate, 8,000 IU; cholecaldferoL 2,200 ICU; vitamin E (DL-a-tocopheryl acetate), 8.0 IU; menadione, 2.0 mg; riboflavin, 5.5 mg; pantothenic acid, 13.0 mg; niacin, 36 mg; choline, 500 mg; vitamin B12, .02 mg; folic acid, .50 mg; thiamine, 1.0 mg; pyridoxine, 22 mg; iron, 55 mg; copper, 6 mg; zinc, 55 mg.
by weighing the feeders before and after the feeding period, and correcting for spilled feed. Corrections for availability of natural (88%) and synthetic (92%) lysine sources were made according to the findings of Sibbald and Wolynetz (1985) and are reflected in Table 2. Total excreta collections were made by a cup-and-harness collection procedure previously described b y Revington et al. (1991b). Collections were made daily for 8 consecutive days. Individual daily samples were analyzed. Total daily excreta were weighed, then frozen at -20 C until completion of the experiment, when all samples were lyophilized to determine moisture content. Duplicate samples of feed and excreta were analyzed by semi-micro Kjeldahl for N content and by adiabatic oxygen bomb calorimetry for gross energy. The AME and AMEn values for the diets were calculated according to methods outlined by Wolynetz and Sibbald (1984). Nitrogen retention and balance data were also determined from these variables. Experiment 2 Twenty-four broiler breeder males at 30 wk of age were arranged into six groups of approximately equal average BW. Groups were then assigned at random to sets of
LYSINE FOR BROILER BREEDER MALES TABLE 2. Dietary supplemental L-lysine HC1 and total lysine intake of 78-wk-old caged broiler breeder males. Experiment 1 L-lysine HC1 Added Total1
Lysine intake
(mg/kg BW (mg/dayr per dayr 503 122 25.4 .05 239 184 40.0 .10 .275 198 41.2 35 .383 258 535 ^Based on the National Research Council (1984) value for corn of .24% lysine and 88% availability. Llysine H Q assumed 78.8% lysine and 92% available (Sibbald and Wolynetz, 1985). Based on mean DM intake for each diet. %ased on mean BW of birds in each treatment group-
(%)
individual metabolism cages located in a single 3 x 3 m room. Water was available for ad libitum intake, and temperatures averaged 25 C for the duration of the experiment. Six diets each containing different levels of supplemental L-lysine HC1 were fed (0, .15, .30, .45, .60, and .75%). The basal diet (0% added L-lysine H Q ) was a remix of the same diet used in Experiment 1, however the same corn source as in Experiment 1 was used. Birds were allowed to eat for 45 m i n / d a y to a maximum daily intake of 325 kcal AMEj! per bird. Total excreta collections were made daily for 5 consecutive days, and daily feed intake was recorded. Corrections for lysine availability were made as in Experiment 1. All other conditions were as reported in Experiment 1.
325
1...4 in Experiment 1; i = 1...6 in Experiment 2); (Dy X Dt)jj = the corresponding day by diet interaction term; and e ^ = a random error term associated with each individual observation (k = 1...4). Orthogonal polynomial contrasts were applied to diet means. Coefficients for four unequally spaced treatment levels (Gill, 1978) were used to test for first- and secondorder polynomial responses in Experiment 1, and coefficients for six equally spaced treatments were used in Experiment 2 (Snedecor and Cochran, 1980). The day by diet interaction was used for testing significance of all diet effects, in accordance with a random model. For specific variables, analysis of covariance (ANCOVA) was also employed. Least-squares means are reported in the tables when the covariate was significant, and regression techniques were applied where indicated.
RESULTS Experiment 1
As expected, supplementing the diet with L-lysine HC1 resulted in increased lysine intake (Table 2). However, variation in DM intake and BW resulted in levels of lysine intake that were not greatly different among some of the treatment groups. Daily DM intake, ME intake, and N intake were different among the four dietary treatments (P<.001; Table 3) and each responded quadratically to increasing lysine level. However, N retention and balance were not different between treatments. Similarly, there were no linear or quadratic responses to dietary lysine supplementation. Day effects were not consistently seen in any of the variables measured, and were thus Statistical Analysis excluded from presentation. Data were analyzed using the General To test that the differences in DM intake Linear Models procedure of the SAS Insti- (and thus lysine intake) among treatments tute (1988) according to the following did not affect retention and balance data, model: ANCOVA was employed with N intake (milligrams) as the covariate. This tested the % = |A + Dyi + Dtj + (Dy x Dt)ij effect of dietary lysine on N balance if all birds had identical N intake. Under these + e^ circumstances, treatment differences would where: Y^ = an individual observation; |X = relate to the total proportion of intake N the overall population mean; DyA = the r * that was derived from lysine. The results of day effect (i = 1...8 in Experiment 1; i = 1...5 this analysis are given in Table 4. Although in Experiment 2); Dtj = the j™ diet effect (i = there were differences in N intake (P<.001;
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TABLE 3. Daily intake of dry matter, metabolizable energy, and nitrogen and nitrogen retention and balance data for caged 78-wk-old broiler breeder males fed lysine-supplemented, all-corn diets, Experiment 1 Lysine added
(%) !05 .10 .25 Source of variation (df) Diet (3) Linear (1) Quadratic (1) SEM
Nitrogen
Intake DM
ME
(g) 60.0 77.0 72.0 67.3
(kcal) 186 298 256 218
*** NS *** 2.5
*** NS *** 13
Retention
N
(mg)
—
880 1,130 1,060 1,020 Significance *** NS *** 40
-
Balance (mg/kg BW)
237 394 249 398
53.4 89.1 50.4 845
NS NS NS 48
NS NS NS 105
*Each value represents the mean of four birds per day over 8 days. •*P<.001.
Table 3), N retention and balance differences were still nonsignificant, indicating that both variates were unrelated to dietary lysine level. As expected, least-squares means of ME intake were virtually identical with ANCOVA. At ME intakes realized in this experiment, there were no differences in N retention or N balance that could be attributed to supplemental L-lysine HC1. Regression analysis of least-squares means confirmed the lack of relationship with lysine, as both linear and quadratic components were nonsignificant. Experiment 2 Because the birds used in this experiment were lighter in BW than those in the first
experiment [4,917 ±43 (SE) g in Experiment 1 versus 3,803 ± 30 g in Experiment 2], higher lysine levels and a greater range of supplementation were used (Table 5). The birds in this experiment were younger (circa 30 wk) and had higher lysine intake per kg BW than did the 78-wk-old birds of Experiment 1, despite similar levels of DM intake (Table 6). As in Experiment 1, day effects were not significant, and are excluded from presentation. Nitrogen retention and balance differed between diets and increased linearly with supplemental L-lysine H Q (Table 6). When ANCOVA was applied as in Experiment 1, diet effects were no longer significant (P>.05; Table 7) for N retention or balance.
TABLE 4. Least-squares means of daily metabolizable energy intake and nitrogen retention and balance of caged 78-wk-old broiler breeder males fed lysine-supplemented, all-corn diets after analysis of covariance, Experiment l 1 Lysine added
(%) !05 .10 .25 variation (df) Diet (3) Covariate (1) SEM
Nitrog en
ME Intake
Retention
(kcal) 254 250 249 248
(mg) 404 280 221 404 Significance NS
NS
<**
1
***
Balance (mg/kg BW) 92 63 44 86 NS
***
36 7 x Each value represents the mean of four birds per day over 8 days. Covariate is N intake (grams). *WP<.001.
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LYSINE FOR BROILER BREEDER MALES TABLE 5. Dietary supplemental L-lysine HC1 and total lysine intake of 30-wk-old caged broiler breeder males. Experiment 2 L-lysine H Q Total1
Added
(%) . . . .15 .30 .45 .60 .75
.203 .311 .420 .528 .637 .745
Lysine intake (mg/day)'' 159 209 220 417 494 600
(mg/kg BW per day) 3 40.0 55.2 54.8 105.6 146.3 160.1
1
Based on the National Research Council (1984) value for corn of .24% lysine and 88% availability. Llysine H Q assumed 78.8% lysine and 92% available (Sibbald and Wolynetz, 1985). 2 Based on mean DM intake for each diet. ^ased on mean BW of birds in each treatment group.
Thus, the differences noted in Table 6 were attributed to differences in N intake rather than to different levels of supplemental Llysine HQ. Regression analysis was applied to the N balance data in Table 7. A linear model gave the best fit to the data (Figure 1). Thus, at equalized N intakes, the birds in Experiment 2 retained more N when a higher proportion of the total was supplied by supplemental L-lysine HC1.
DISCUSSION In the present study, force-feeding was purposely avoided because of its impracticality with large numbers of birds. The original intent was to have the birds consume similar amounts of feed voluntarily, based on an energy intake of 325 kcal per bird per day. This caloric intake has previously been shown to be adequate for the broiler breeder male (Anonymous, 1987). However, the birds did not consume their feed (100 g per bird per day on an as-is basis) in the time allotted. If the assumption that birds generally eat to fulfill their energy requirement is valid, then it would appear that energy availability was not a limiting factor in determining N retention in these experiments. Although ME intake was similar to that experienced in previous trials of this type (Revington et ah, 1988), variability was greater. When this variability in intake is coupled with variations in BW, values for the intake of available lysine on a per kilogram of BW basis did not follow the same pattern of linearity as the original treatments. For this reason, lysine supplementation level was used as the independent variable in the analyses, rather than lysine intake. The results presented here for Experiment 1 indirectly agree with the results reported by Leveille and Fisher (1959) for
TABLE 6. Daily intake of dry matter, metabolizable energy, and nitrogen and nitrogen retention and balance data for caged 30-wk-old broiler breeder males fed lysine-supplemented, all-corn diets, Experiment 2 1 Lysine added
(%) .15 .30 .45 .60 .75 Source of -variation (df) Diet (3) Linear (1) Quadratic (1) SEM
Nitrogen
Intake DM
ME
Retention
N
(g)
(kcal)
- ( m ir) [
78.3 67.1 52.3 78.9 77.5 80.6
273 234 184 276 270 280
1,186 1,023 838 1,245 1,233 1,298
**# ***• ***
*** *** **#
<#* *** ***
1.4
5
&>
Balance (mg/kg BW)
390 329 265 526 481 528
975 89.4 65.6 133.3 141.8 142.8
*** ***
*** ***
NS 18
NS 4.8
22
Each value represents the mean of four birds per day over 5 days. ***P<.001.
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TABLE 7. Least-squares means of daily metabolizable energy intake and nitrogen retention and balance of caged 30-wk-old broiler breeder males fed lysine-supplemented, all-corn diets after analysis of covariance, Experiment 2 Lysine added
ME Intake
Retention
(%)
(kcal) 262 260 251 251 247 243
Omg) 364 390 426 469 429 441
Nitrogen Balance (mg/kg BW) 91 104 105 119 129 122
.15 .30 .45 .60 .75 Source of variation (df) *** Diet (3) NS NS **+ Covariate (1) *** *** SEM 1 12 3 1 Each value represents the mean of four birds per day over 5 days. Covariate is N intake (grams). «*P<001.
the SCWL male. They used birds at 52 wk of age and showed the maintenance requirement for lysine to be very low (no greater than 29 m g / k g BW per day). At levels of lysine intake below those experienced in the present study (no lysine in a purified diet), positive N balance was still maintained. On the other hand, Ishibashi (1973) used birds ranging in age from 40 to 104 wk of age, and the maintenance lysine requirement was found to be 40 m g / k g BW per day. These are high values by comparison and may have resulted from the use of birds from the younger side of this range, although the exact age of the birds used for the lysine determination was not reported. Neither Leveille and Fisher (1959) nor Ishibashi (1973) appear to have taken lysine availability into account in their calculations, however. The N intake of birds receiving no supplemental L-lysine HC1 was approximately 180 mg N / k g BW per day in Experiment 1, and 310 m g / k g BW per day in Experiment 2. Leveille and Fisher (1958) determined the minimum N requirement for the SCWL male to be 280 mg N / k g BW per day. Presumably, the lysine requirement is greater in younger birds than in older birds because additional needs for growth are superimposed. Breeder mana g e m e n t procedures involve severe weight restriction at 28 to 30 w k of age
(Anonymous, 1987), however, Revington et al. (1991a) showed that broiler breeder males fed corn-based diets identical to those used in the present study from 24 to 68 w k of age had BW lower than breeder 130
120
110
100
.00 %
.15 .30 SUPPLEMENTAL
.45 .60 L-LYSINE
HCI
FIGURE 1. Regression of least-squares means of N balance on supplementary L-lysine H Q in Experiment 2. The model is significantly linear (P<.05). The N balance = 94.2 + 465(Lys%). Both intercept and slope are significant (P<.05). The R2 = .82. The same data from Experiment 1 were not significant.
LYSINE FOR BROILER BREEDER MALES
recommendations at equal ME intakes. This decrease in growth may have been the result of insufficient lysine to support muscle accrual prior to the cessation of growth, as lysine is relatively high in muscle tissue (Block and Boiling, 1951). Nitrogen excretion is an energy-intensive process in avian species, and excess lysine supplementation might be expected to affect dietary energy intake. In both experiments, lysine supplementation showed a significant quadratic effect on ME intake (Tables 3 and 4). However, the curves described by the two data sets are opposite in nature; Experiment 1 indicates a ME intake maximum at the .05% level of lysine supplementation (78 wk of age), and Experiment 2 indicates a ME intake minimum at the .30% level of lysine supplementation (30 w k of age). In experiments of this type, maxima typically indicate optimal levels of supplementation. On the other hand, minima can be difficult to interpret. In light of the significant linear effects seen in Experiment 2, it is probable that the optimal level of supplementation was not reached, and the quadratic effect is a spurious artefact of the data. In Experiment 1, ANCOVA did not alter the conclusions regarding the effect of dietary lysine level on 78-wk-old breeder males. Neither N retention nor N balance responded to dietary lysine, suggesting that requirements for lysine are relatively low in birds of this age. Although diet effects on N retention and balance were removed by ANCOVA in Experiment 2, significant regression effects confirm that young broiler breeder males retain more N when lysine is supplemented in corn-based diets. Thus, the lysine requirement of caged broiler breeder males declines through the breeder period to the point where lysine levels inherent in good-quality corn are adequate to meet minimal maintenance needs. ACKNOWLEDGMENTS The technical assistance of Chen Benxu and Steve Welch is greatly appreciated.
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REFERENCES Anonymous, 1987. Guidelines for male separate feeding in the laying period. Ross Tech: A Technical Bulletin from the Ross People. Ross Poultry Breeders, Inc., Elkmont, AL. Arscott, G. H., and J. E. Parker, 1963. Dietary protein and fertility of chickens. J. Nutr. 80:311-314. Block, R. J., and D. Boiling, 1951. Pages 485-492 in: The Amino Acid Composition of Proteins and Foods. Chapter X: Summary Tables. 2nd ed. Charles C. Thomas, Publishers, Springfield, IL. Gill, J. L., 1978. Design and Analysis of Experiments in the Animal and Medical Sciences. Vol. 3, appendices. Iowa State University Press, Ames, IA. Ishibashi, T., 1973. Amino acid requirements for maintenance of the adult rooster. Jpn. J. Zootech. Sci. 44:39-49. Leveille, G. A., and H. Fisher, 1958. The amino acid requirements for maintenance in the adult rooster I. Nitrogen and energy requirements in normal and protein-depleted animals receiving whole egg protein and amino acid diets. J. Nutr. 66:441-453. Leveille, G. A., and H. Fisher, 1959. Amino acid requirements for maintenance in the adult rooster. II. The requirements for glutamic acid, histidine, lysine and arginine. J. Nutr. 69: 289-294. Leveille, G. A., R. Shapiro, and H. Fisher, 1960. Amino acid requirements for maintenance in the adult rooster IV: The requirements for methionine, cystine, phenylalanine, tyrosine and tryptophan; the adequacy of the determined requirements. J. Nutr. 72:8-15. National Research Council, 1984. Nutrient Requirements of Poultry. 8th rev. ed. National Academy Press, Washington, DC. Revington, W. H., N. Acar, and E. T. Moran, Jr., 1991b. Cup versus tray excreta collections in metabolizable energy assays. Poultry Sci. 70: 1265-1268. Revington, W. H., E. T. Moran, Jr., and S. F. Bilgili, 1988. Nitrogen retention of broiler breeder males fed standard vs. all-corn diets. Poultry Sci. 67(Suppl. l):144.(Abstr.) Revington, W. H., E. T. Moran, Jr., and G. R. McDaniel, 1991a. Performance of broiler breeder males given low protein feed. Poultry Sci. 70: 139-145. SAS Institute, 1988. SAS/STAT® User's Guide, Release 6.03 Edition. SAS Institute Inc., Cary, NC. Sibbald, I. R., and M. S. Wolynetz, 1985. The bioavailability of supplementary lysine and its effect on the energy and nitrogen excretion of adult cockerels fed diets diluted with cellulose. Poultry Sci. 64:1972-1975. Snedecor, G. W., and W. G. Cochran, 1980. Statistical Methods. 7th edition. The Iowa State University Press, Ames, IA. Wilson, H. R., L. O. Rowland, Jr., and R. H. Harms, 1971. Use of low protein grower diets to delay sexual maturity of broiler breeding males. Br. Poult. Sci. 12:157-163. Wilson, H. R., P. W. Waldroup, J. E. Jones, D. J.
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Duerre, and R. H. Harms, 1965. Protein levels in growing diets and reproductive performance of cockerels. J. Nutr. 85:29-37. Wilson, J. L., G. R. McDaniel, and C. D. Sutton, 1987a. Dietary protein levels for broiler breeder males. Poultry Sci. 66237-242. Wilson, J. L., G. R. McDaniel, C. D. Sutton, and J. A.
Renden, 1987b. Semen and carcass evaluation of broiler breeder males fed low protein diets. Poultry Sci. 66:1535-1540. Wolynetz, M. S., and I. R. Sibbald, 1984. Relationships between apparent and true metabolizable energy and the effects of a nitrogen correction. Poultry Sci. 63:1386-1399.
INTRODUCTION Wilson et al, (1987a,b) reported improved reproductive performance in broiler breeder males fed low-protein feeds (12% CP). Although reports are inconclusive, there is some evidence to suggest that even lower protein levels can be used to improve the reproductive performance of males (Leveille and Fisher, 1958; Arscott and Parker, 1963; Wilson et
Alabama Agricultural Experiment Station Journal Number 12-902498P. 2 Present address: New-Life Mills, Ltd., 1400 Bishop St., Cambridge, ON, N1R 6W8, Canada.
al., 1965; Wilson et al., 1987b). Success of low-protein regimens seems to depend on provision of balanced dietary protein, and on the implementation of such regimens subsequent to the onset of sexual maturity (Wilson et ah, 1971). Practical diets formulated to low levels of dietary protein are likely to have a high proportion of grain and a high proportion of energy relative to protein. They may also be low in lysine, particularly when corn is the primary ingredient. Revington et al. (1991a) fed caged breeder males either an all-corn diet (AC, 8% CP) or a standard corn and soybean meal diet (ST, 12% CP) at a rate of 325 kcal MEn per bird per day from 24 to 68 wk of
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age. Although BW of males fed the AC diet was significantly less than BW of birds receiving the ST diet, there was no apparent detriment to reproductive performance. Carcasses from birds fed 8% CP were proportionally fatter than those from birds that received the 12% CP control diet. Furthermore, Revington et al. (1988) showed that N intake paralleled N retention as dietary regimens were proportionally shifted from ST to AC. However, the relative proportion of N retained by birds was less for the 8% CP diet than for the 12% CP feed despite equal energy intakes and positive N balance. Taken together, these results suggest the possibility of improving protein utilization by supplementing corn-based diets with specific essential amino acids. Because the lysine content of corn is low relative to energy, and this amino acid is easily supplemented in free form, two experiments were conducted to determine the effect of supplemental lysine on N utilization in low-protein, all-corn diets. MATERIALS AND METHODS Experiment 1 Sixteen 78-wk-old broiler breeder males (Ross) were divided into four groups of approximately equal average BW. Each group was assigned to a set of four individual male breeder cages in a lighttight breeder facility. Water was available for ad libitum intake through nipple drinkers and the birds received 15 h of light/day during the experiment. Temperature averaged 25 C throughout the experimental period. Each group was randomly assigned to one of four dietary treatments consisting of different levels of supplemental L-lysine HC1 at the expense of corn (.05, .10, .25% Llysine H O ) . The basal diet (0% added Llysine HC1; Table 1) was formulated to approximate the amino acid requirements as reported by Leveille et al. (1960) for the Single Comb White Leghorn (SCWL) male. Birds received their respective test diets for 3 days prior to formal excreta collections, and for 45 min/day. All diets were fed to provide approximately 325 kcal AME„ per bird per day. Actual intake was determined
TABLE 1. Composition of the basal diet fed to caged broiler breeder males Ingredients and composition Ground corn DL-methionine Dicalcium phosphate Limestone Salt Vitamin-mineral mix1 Total Assayed composition CP, % MEn, kcal/kg
Percentage 96.00 .15 1.25 1.75 .35 .50 100.00 82 3,070
Supplied the following to each kilogram of finished feed: vitamin A palmitate, 8,000 IU; cholecaldferoL 2,200 ICU; vitamin E (DL-a-tocopheryl acetate), 8.0 IU; menadione, 2.0 mg; riboflavin, 5.5 mg; pantothenic acid, 13.0 mg; niacin, 36 mg; choline, 500 mg; vitamin B12, .02 mg; folic acid, .50 mg; thiamine, 1.0 mg; pyridoxine, 22 mg; iron, 55 mg; copper, 6 mg; zinc, 55 mg.
by weighing the feeders before and after the feeding period, and correcting for spilled feed. Corrections for availability of natural (88%) and synthetic (92%) lysine sources were made according to the findings of Sibbald and Wolynetz (1985) and are reflected in Table 2. Total excreta collections were made by a cup-and-harness collection procedure previously described b y Revington et al. (1991b). Collections were made daily for 8 consecutive days. Individual daily samples were analyzed. Total daily excreta were weighed, then frozen at -20 C until completion of the experiment, when all samples were lyophilized to determine moisture content. Duplicate samples of feed and excreta were analyzed by semi-micro Kjeldahl for N content and by adiabatic oxygen bomb calorimetry for gross energy. The AME and AMEn values for the diets were calculated according to methods outlined by Wolynetz and Sibbald (1984). Nitrogen retention and balance data were also determined from these variables. Experiment 2 Twenty-four broiler breeder males at 30 wk of age were arranged into six groups of approximately equal average BW. Groups were then assigned at random to sets of
LYSINE FOR BROILER BREEDER MALES TABLE 2. Dietary supplemental L-lysine HC1 and total lysine intake of 78-wk-old caged broiler breeder males. Experiment 1 L-lysine HC1 Added Total1
Lysine intake
(mg/kg BW (mg/dayr per dayr 503 122 25.4 .05 239 184 40.0 .10 .275 198 41.2 35 .383 258 535 ^Based on the National Research Council (1984) value for corn of .24% lysine and 88% availability. Llysine H Q assumed 78.8% lysine and 92% available (Sibbald and Wolynetz, 1985). Based on mean DM intake for each diet. %ased on mean BW of birds in each treatment group-
(%)
individual metabolism cages located in a single 3 x 3 m room. Water was available for ad libitum intake, and temperatures averaged 25 C for the duration of the experiment. Six diets each containing different levels of supplemental L-lysine HC1 were fed (0, .15, .30, .45, .60, and .75%). The basal diet (0% added L-lysine H Q ) was a remix of the same diet used in Experiment 1, however the same corn source as in Experiment 1 was used. Birds were allowed to eat for 45 m i n / d a y to a maximum daily intake of 325 kcal AMEj! per bird. Total excreta collections were made daily for 5 consecutive days, and daily feed intake was recorded. Corrections for lysine availability were made as in Experiment 1. All other conditions were as reported in Experiment 1.
325
1...4 in Experiment 1; i = 1...6 in Experiment 2); (Dy X Dt)jj = the corresponding day by diet interaction term; and e ^ = a random error term associated with each individual observation (k = 1...4). Orthogonal polynomial contrasts were applied to diet means. Coefficients for four unequally spaced treatment levels (Gill, 1978) were used to test for first- and secondorder polynomial responses in Experiment 1, and coefficients for six equally spaced treatments were used in Experiment 2 (Snedecor and Cochran, 1980). The day by diet interaction was used for testing significance of all diet effects, in accordance with a random model. For specific variables, analysis of covariance (ANCOVA) was also employed. Least-squares means are reported in the tables when the covariate was significant, and regression techniques were applied where indicated.
RESULTS Experiment 1
As expected, supplementing the diet with L-lysine HC1 resulted in increased lysine intake (Table 2). However, variation in DM intake and BW resulted in levels of lysine intake that were not greatly different among some of the treatment groups. Daily DM intake, ME intake, and N intake were different among the four dietary treatments (P<.001; Table 3) and each responded quadratically to increasing lysine level. However, N retention and balance were not different between treatments. Similarly, there were no linear or quadratic responses to dietary lysine supplementation. Day effects were not consistently seen in any of the variables measured, and were thus Statistical Analysis excluded from presentation. Data were analyzed using the General To test that the differences in DM intake Linear Models procedure of the SAS Insti- (and thus lysine intake) among treatments tute (1988) according to the following did not affect retention and balance data, model: ANCOVA was employed with N intake (milligrams) as the covariate. This tested the % = |A + Dyi + Dtj + (Dy x Dt)ij effect of dietary lysine on N balance if all birds had identical N intake. Under these + e^ circumstances, treatment differences would where: Y^ = an individual observation; |X = relate to the total proportion of intake N the overall population mean; DyA = the r * that was derived from lysine. The results of day effect (i = 1...8 in Experiment 1; i = 1...5 this analysis are given in Table 4. Although in Experiment 2); Dtj = the j™ diet effect (i = there were differences in N intake (P<.001;
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REVINGTON ET AL.
TABLE 3. Daily intake of dry matter, metabolizable energy, and nitrogen and nitrogen retention and balance data for caged 78-wk-old broiler breeder males fed lysine-supplemented, all-corn diets, Experiment 1 Lysine added
(%) !05 .10 .25 Source of variation (df) Diet (3) Linear (1) Quadratic (1) SEM
Nitrogen
Intake DM
ME
(g) 60.0 77.0 72.0 67.3
(kcal) 186 298 256 218
*** NS *** 2.5
*** NS *** 13
Retention
N
(mg)
—
880 1,130 1,060 1,020 Significance *** NS *** 40
-
Balance (mg/kg BW)
237 394 249 398
53.4 89.1 50.4 845
NS NS NS 48
NS NS NS 105
*Each value represents the mean of four birds per day over 8 days. •*P<.001.
Table 3), N retention and balance differences were still nonsignificant, indicating that both variates were unrelated to dietary lysine level. As expected, least-squares means of ME intake were virtually identical with ANCOVA. At ME intakes realized in this experiment, there were no differences in N retention or N balance that could be attributed to supplemental L-lysine HC1. Regression analysis of least-squares means confirmed the lack of relationship with lysine, as both linear and quadratic components were nonsignificant. Experiment 2 Because the birds used in this experiment were lighter in BW than those in the first
experiment [4,917 ±43 (SE) g in Experiment 1 versus 3,803 ± 30 g in Experiment 2], higher lysine levels and a greater range of supplementation were used (Table 5). The birds in this experiment were younger (circa 30 wk) and had higher lysine intake per kg BW than did the 78-wk-old birds of Experiment 1, despite similar levels of DM intake (Table 6). As in Experiment 1, day effects were not significant, and are excluded from presentation. Nitrogen retention and balance differed between diets and increased linearly with supplemental L-lysine H Q (Table 6). When ANCOVA was applied as in Experiment 1, diet effects were no longer significant (P>.05; Table 7) for N retention or balance.
TABLE 4. Least-squares means of daily metabolizable energy intake and nitrogen retention and balance of caged 78-wk-old broiler breeder males fed lysine-supplemented, all-corn diets after analysis of covariance, Experiment l 1 Lysine added
(%) !05 .10 .25 variation (df) Diet (3) Covariate (1) SEM
Nitrog en
ME Intake
Retention
(kcal) 254 250 249 248
(mg) 404 280 221 404 Significance NS
NS
<**
1
***
Balance (mg/kg BW) 92 63 44 86 NS
***
36 7 x Each value represents the mean of four birds per day over 8 days. Covariate is N intake (grams). *WP<.001.
327
LYSINE FOR BROILER BREEDER MALES TABLE 5. Dietary supplemental L-lysine HC1 and total lysine intake of 30-wk-old caged broiler breeder males. Experiment 2 L-lysine H Q Total1
Added
(%) . . . .15 .30 .45 .60 .75
.203 .311 .420 .528 .637 .745
Lysine intake (mg/day)'' 159 209 220 417 494 600
(mg/kg BW per day) 3 40.0 55.2 54.8 105.6 146.3 160.1
1
Based on the National Research Council (1984) value for corn of .24% lysine and 88% availability. Llysine H Q assumed 78.8% lysine and 92% available (Sibbald and Wolynetz, 1985). 2 Based on mean DM intake for each diet. ^ased on mean BW of birds in each treatment group.
Thus, the differences noted in Table 6 were attributed to differences in N intake rather than to different levels of supplemental Llysine HQ. Regression analysis was applied to the N balance data in Table 7. A linear model gave the best fit to the data (Figure 1). Thus, at equalized N intakes, the birds in Experiment 2 retained more N when a higher proportion of the total was supplied by supplemental L-lysine HC1.
DISCUSSION In the present study, force-feeding was purposely avoided because of its impracticality with large numbers of birds. The original intent was to have the birds consume similar amounts of feed voluntarily, based on an energy intake of 325 kcal per bird per day. This caloric intake has previously been shown to be adequate for the broiler breeder male (Anonymous, 1987). However, the birds did not consume their feed (100 g per bird per day on an as-is basis) in the time allotted. If the assumption that birds generally eat to fulfill their energy requirement is valid, then it would appear that energy availability was not a limiting factor in determining N retention in these experiments. Although ME intake was similar to that experienced in previous trials of this type (Revington et ah, 1988), variability was greater. When this variability in intake is coupled with variations in BW, values for the intake of available lysine on a per kilogram of BW basis did not follow the same pattern of linearity as the original treatments. For this reason, lysine supplementation level was used as the independent variable in the analyses, rather than lysine intake. The results presented here for Experiment 1 indirectly agree with the results reported by Leveille and Fisher (1959) for
TABLE 6. Daily intake of dry matter, metabolizable energy, and nitrogen and nitrogen retention and balance data for caged 30-wk-old broiler breeder males fed lysine-supplemented, all-corn diets, Experiment 2 1 Lysine added
(%) .15 .30 .45 .60 .75 Source of -variation (df) Diet (3) Linear (1) Quadratic (1) SEM
Nitrogen
Intake DM
ME
Retention
N
(g)
(kcal)
- ( m ir) [
78.3 67.1 52.3 78.9 77.5 80.6
273 234 184 276 270 280
1,186 1,023 838 1,245 1,233 1,298
**# ***• ***
*** *** **#
<#* *** ***
1.4
5
&>
Balance (mg/kg BW)
390 329 265 526 481 528
975 89.4 65.6 133.3 141.8 142.8
*** ***
*** ***
NS 18
NS 4.8
22
Each value represents the mean of four birds per day over 5 days. ***P<.001.
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REVINGTON FT AL.
TABLE 7. Least-squares means of daily metabolizable energy intake and nitrogen retention and balance of caged 30-wk-old broiler breeder males fed lysine-supplemented, all-corn diets after analysis of covariance, Experiment 2 Lysine added
ME Intake
Retention
(%)
(kcal) 262 260 251 251 247 243
Omg) 364 390 426 469 429 441
Nitrogen Balance (mg/kg BW) 91 104 105 119 129 122
.15 .30 .45 .60 .75 Source of variation (df) *** Diet (3) NS NS **+ Covariate (1) *** *** SEM 1 12 3 1 Each value represents the mean of four birds per day over 5 days. Covariate is N intake (grams). «*P<001.
the SCWL male. They used birds at 52 wk of age and showed the maintenance requirement for lysine to be very low (no greater than 29 m g / k g BW per day). At levels of lysine intake below those experienced in the present study (no lysine in a purified diet), positive N balance was still maintained. On the other hand, Ishibashi (1973) used birds ranging in age from 40 to 104 wk of age, and the maintenance lysine requirement was found to be 40 m g / k g BW per day. These are high values by comparison and may have resulted from the use of birds from the younger side of this range, although the exact age of the birds used for the lysine determination was not reported. Neither Leveille and Fisher (1959) nor Ishibashi (1973) appear to have taken lysine availability into account in their calculations, however. The N intake of birds receiving no supplemental L-lysine HC1 was approximately 180 mg N / k g BW per day in Experiment 1, and 310 m g / k g BW per day in Experiment 2. Leveille and Fisher (1958) determined the minimum N requirement for the SCWL male to be 280 mg N / k g BW per day. Presumably, the lysine requirement is greater in younger birds than in older birds because additional needs for growth are superimposed. Breeder mana g e m e n t procedures involve severe weight restriction at 28 to 30 w k of age
(Anonymous, 1987), however, Revington et al. (1991a) showed that broiler breeder males fed corn-based diets identical to those used in the present study from 24 to 68 w k of age had BW lower than breeder 130
120
110
100
.00 %
.15 .30 SUPPLEMENTAL
.45 .60 L-LYSINE
HCI
FIGURE 1. Regression of least-squares means of N balance on supplementary L-lysine H Q in Experiment 2. The model is significantly linear (P<.05). The N balance = 94.2 + 465(Lys%). Both intercept and slope are significant (P<.05). The R2 = .82. The same data from Experiment 1 were not significant.
LYSINE FOR BROILER BREEDER MALES
recommendations at equal ME intakes. This decrease in growth may have been the result of insufficient lysine to support muscle accrual prior to the cessation of growth, as lysine is relatively high in muscle tissue (Block and Boiling, 1951). Nitrogen excretion is an energy-intensive process in avian species, and excess lysine supplementation might be expected to affect dietary energy intake. In both experiments, lysine supplementation showed a significant quadratic effect on ME intake (Tables 3 and 4). However, the curves described by the two data sets are opposite in nature; Experiment 1 indicates a ME intake maximum at the .05% level of lysine supplementation (78 wk of age), and Experiment 2 indicates a ME intake minimum at the .30% level of lysine supplementation (30 w k of age). In experiments of this type, maxima typically indicate optimal levels of supplementation. On the other hand, minima can be difficult to interpret. In light of the significant linear effects seen in Experiment 2, it is probable that the optimal level of supplementation was not reached, and the quadratic effect is a spurious artefact of the data. In Experiment 1, ANCOVA did not alter the conclusions regarding the effect of dietary lysine level on 78-wk-old breeder males. Neither N retention nor N balance responded to dietary lysine, suggesting that requirements for lysine are relatively low in birds of this age. Although diet effects on N retention and balance were removed by ANCOVA in Experiment 2, significant regression effects confirm that young broiler breeder males retain more N when lysine is supplemented in corn-based diets. Thus, the lysine requirement of caged broiler breeder males declines through the breeder period to the point where lysine levels inherent in good-quality corn are adequate to meet minimal maintenance needs. ACKNOWLEDGMENTS The technical assistance of Chen Benxu and Steve Welch is greatly appreciated.
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Duerre, and R. H. Harms, 1965. Protein levels in growing diets and reproductive performance of cockerels. J. Nutr. 85:29-37. Wilson, J. L., G. R. McDaniel, and C. D. Sutton, 1987a. Dietary protein levels for broiler breeder males. Poultry Sci. 66237-242. Wilson, J. L., G. R. McDaniel, C. D. Sutton, and J. A.
Renden, 1987b. Semen and carcass evaluation of broiler breeder males fed low protein diets. Poultry Sci. 66:1535-1540. Wolynetz, M. S., and I. R. Sibbald, 1984. Relationships between apparent and true metabolizable energy and the effects of a nitrogen correction. Poultry Sci. 63:1386-1399.