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Starter and subsequent grower response of Pekin ducks to low-protein diets in starter phase
Author’s Accepted Manuscript Starter and subsequent grower response of Pekin ducks to low-protein diets in starter phase M. Xie, Y. Jiang, J. Tang, Q. Zhang, W. Huang, S.S. Hou www.elsevier.com/locate/livsci
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S1871-1413(17)30201-9 http://dx.doi.org/10.1016/j.livsci.2017.07.005 LIVSCI3256
To appear in: Livestock Science Received date: 22 January 2017 Revised date: 13 June 2017 Accepted date: 7 July 2017 Cite this article as: M. Xie, Y. Jiang, J. Tang, Q. Zhang, W. Huang and S.S. Hou, Starter and subsequent grower response of Pekin ducks to low-protein diets in starter phase, Livestock Science, http://dx.doi.org/10.1016/j.livsci.2017.07.005 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Starter and subsequent grower response of Pekin ducks to low-protein diets in starter phase M. Xie, Y. Jiang, J. Tang, Q. Zhang, W. Huang, S.S. Hou* State Key Laboratory of Animal Nutrition, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing, 100193, China *
Corresponding author. Tel.: +86 10 6281 6227; fax: +86 10 6281 5832. [email protected]
Abstract A dose-response experiment was conducted to investigate the effects of feeding 6 starter diets containing the analyzed crude protein (CP) contents (168.6, 178.9, 184.2, 192.0, 195.8, and 203.3 g/kg) from d 1 to 19 on growth performance and carcass traits of starter Pekin ducks and the subsequent growth performance and carcass traits of ducks fed a common grower diet from d 20 to 35. The 480 one-d-old male White Pekin ducks were divided to 6 experimental treatments and each treatment had 8 replicate pens of 10 ducks. All starter experimental diets were formulated to contain similar dietary energy concentration and standardized ileal digestible amino acid contents. At d 19 and 35, the growth performance of each pen were determined and 2 ducks were randomly selected from each pen and harvested to evaluate carcass traits. During the starter period, as dietary CP decreased from 203.3 to 168.6 g/kg, the body weight, weight gain, and feed intake were not affected but feed/gain increased linearly (P = 0.017). According to broken-line regression, the 196.8g/kg was the minimum dietary CP requirement necessary to obtain the optimal feed/gain during the starter period. Moreover, the breast meat percentage of starter ducklings was not influenced by reducing dietary CP, but the leg meat percentage decreased linearly (P = 0.024) and abdominal fat percentage increased linearly (P = 0.018). During the grower period from d 20 to 35, the protein restriction during the starter phase had no negative effects on the subsequent growth 1
performance from d 20 to 35 or carcass traits at d 35. It was concluded that reducing dietary CP had negative effects on the performance of starter ducks but the protein restriction during the starter phase had no adverse effects on the performance of grower Pekin ducks. Keywords: Duck; Protein; Growth response.
1. Introduction With use of crystalline amino acids in diet formulation, it was possible to reduce dietary crude protein (CP) without negative effects on growth performance and carcass yield and it was also accompanied with the environmental benefit of less nitrogen excretion and ammonia emission. The research on the use of low-protein diets in ducks was very few. In grower muscovy ducks from 8 to 12 wk of age, no substantial modifications in growth performance or carcass quality were observed when dietary CP was reduced from 160 or 150 to 120 g/kg based on similar digestible amino acid contents (Baeza and Leclercq, 1998). In grower Pekin ducks, based on a constant standardized ileal digestible amino acid contents, it was possible to formulate the low-protein diets containing about 15% CP for Pekin ducks without adverse effects on the growth performance and carcass yield of these ducks (Xie et al., 2017). In starter Australian Pekin ducks from 1 to 14 d of age, , when the total amino acid contents kept constant in all diets, the growth performance was not changed markedly among the ducks fed diets with 180, 200, and 220 g CP/kg , respectively (Siregar et al., 1982). However, Chen et al.(2016) and Wilson (1975) found that Pekin ducks given starter diets with 220 or 240 g CP/kg were substantially heavier at d 14 than those given diets with 180 or 200 g CP / kg. Therefore, the use of low-protein diet in starter ducks is debating and the research on this topic should be continued. Recently, it is feasible for broilers to reduce dietary CP by 3% without undermining the performance of early stage broiler chickens (Award et al., 2014; Ospina-Rojas et al., 2014). 2
However, when dietary CP was reduced by more than 3% during the starter period, the broiler chickens fed low-CP diets could not have the growth performance which was equal to that of the broiler chickens fed high-CP diets (Namroud, et al., 2008). Fortunately, the early protein restriction could not influence the subsequent growth of broiler chickens. In the studies of Moran (1979) and Plavnik and Hurwitz, (1990), although the poor body weight and feed efficiency of broiler chickens was caused by low-protein diets during the starter period, the growth performance and the carcass or meat yield at market age would not be reduced markedly by early protein restriction during the starter period. Therefore, it can be hypothesized that the later growth can compensate for the starter growth loss caused by low-CP diets. In broiler chickens, in order to keep amino acid balance, the formulation of low-protein diets was based on the similar total or digestible amino acid contents (Award et al., 2014; Kerr and Kidd, 1999; Namroud et al., 2008; Ospina-Rojas et al., 2014). In Pekin ducks, when dietary amino acids did not keep constant in all diets and the amino acid density decreased as dietary CP decreased, the poorer growth performance would be caused by low-protein diets compared with ducks fed high-protein diets (Chen et al., 2016; Wilson, 1975). Currently, the standardized ileal digestibilities (SID) of amino acids in corn and soybean meal for Pekin ducks were determined successfully and the additivity of SID amino acids in the mixed diets including these 2 feedstuffs was confirmed (Kong and Adeola, 2013). Moreover, Xie et al.(2017) have successfully developed the low-protein diet for grower Pekin ducks based on the SID amino acids and thus it was reasonable to formulate low-protein diet on the SID amino acid basis . Therefore, the objective of our study was to examine the effects of feeding low-protein starter diets with similar SID amino acid contents from d 1 to d 19 on growth performance and carcass traits of starter Pekin ducks and the subsequent growth performance and carcass traits of ducks fed a common grower diet from d 20 to 35. 3
2. Materials and methods 2.1. Experimental design and duck husbandry All procedures of our experiments were approved by the animal care and use committee of Institute of Animal Sciences of Chinese Academy of Agricultural Sciences (Beijing, China). A dose-response experiment with 6 diets based on the analyzed CP contents was used in the study. The 480 one-d-old male White Pekin ducks were allocated randomly to 6 experimental treatments and each treatment contained 8 replicate pens of 10 ducks. All ducks were fed experimental starter diets from 1 to 19 d of age and then only 1 common grower diet with 184.0 g analyzed CP/kg from 20 to 35 d of age. Ducks were reared in raised wire-floor pens (2 m2/pen) from 1 to 35 d of age. During these periods, ducks had free access to water and feed. Water was provided by drip-nipple water supply lines and feed was fed in pellet form (1.5 mm for starter diets and 3 mm for grower diets). In the duck barn, lighting was continuous. The temperature was kept at 33°C from 1 to 3 d of age and then it was reduced gradually to approximately 25°C until 14 d of age and was kept at approximately 16 to 22°C thereafter. 2.2. Diet and feed analysis To keep similar SID amino acid contents, the experimental starter diets with 6 dietary CP concentrations were prepared by mixing highest-CP and lowest-CP diets (Table 1) according to dilution technology (Xie et al., 2017). Firstly, the CP concentrations of corn and soybean meal were determined by Kjeldahl procedure according to the method recommended by Standardization Administration of China (1994). The amino acids of these 2 feedstuffs were analyzed by using ion-exchange chromatography with an amino acid analyzer (L-800; Hitachi, Tokyo, Japan) according to the method recommended by Standardization Administration of China (2000). Tryptophan was analyzed by reverse-phase high performance liquid chromatography and fluorometric detection (Waters, Inc., Milford, US) 4
after alkali hydrolysis at 110°C for 20 h with 4M barium hydroxide. Afterwards, according to the analyzed amino acids of corn and soybean meal and the SID of amino acids in corn and soybean meal for Pekin ducks published by Kong and Adeola (2013), the SID amino acid contents of corn and soybean meal were calculated by multiplying analyzed amino acid contents by SID of the corresponding feedstuffs, respectively. The highest-CP and lowest-CP diet were all formulated to have the same SID amino acid contents including Met, Lys, Thr, Trp, Arg, Ile, Val, and Gly, with formulated dietary CP of 160.0 and 210.0 g/kg for these 2 diets, respectively. Supplemental crystalline amino acids were assumed to be 100% SID digestible. These 2 diets also had similar dietary energy concentrations. The contents of Lys, Met, Arg, Ile, Trp, and Val of these two diets met the NRC(1994) recommendation of Pekin ducks from 0 to 2 wk of age. Dietary threonine content of these two diets met the requirements provided by Xie et al. ( 2014 ) and Jiang et al.( 2016 ) and their glycine+serine content met the NRC (1994) recommendation of broilers from 0 to 3 wk of age due to the lack of this value for ducks. The experimental diets with 6 formulated dietary CP contents ( 160, 170, 180, 190, 200, and 210 g/kg ) were produced by blending the lowest-CP and highest-CP according to different mixing ratio of these 2 diets (5:0, 4:1, 3:2, 2:3, 1:4, and 0:5 ). All experimental diets were cold-pelleted at room temperature and the CP and amino acids of these diets were also analyzed ( Table 2 ) according to the aforementioned methods. The analyzed dietary CP contents of these 6 experimental diets were 168.6, 178.9, 184.2, 192.0, 195.8, and 203.3 g/kg, respectively. In addition, the CP and amino acids of common grower diets ( Table 1 ) were also analyzed by the aforementioned methods. 2.3. Experimental data collection At d 19 and d 35, the weight gain, feed intake and feed/gain of each pen were determined and feed intake and feed/gain were adjusted for mortality. In addition, 2 ducks were randomly 5
selected from each pen at d 19 and 35, fasted for 12h, and harvested by cutting neck and eviscerated manually. The abdominal fat, breast meat (including pectoralis major and pectoralis minor), and leg meat (including thigh and drum stick) were all removed manually from carcasses and weighed, and the percentages relative to live body weight at processing were also calculated. Breast and leg meat were all skinless and boneless. 2.4. Statistical analysis The data were analyzed using SAS software (SAS Inst. Inc., Cary NC, US), and the pen was the experimental unit for analysis. Linear and quadratic polynomial contrasts were used to determine the effect of dietary CP. The variability in the data was expressed as the standard error of the means. A probability level of P < 0.05 was considered to be statistically significant. In present study, the broken-line regression analysis (Robbins et al., 2006) was used to estimate the minimum CP requirements of starter ducks using the NLIN procedure of SAS software (SAS Inst. Inc., Cary NC, US). The broken-line model was: y = l + u (r - x), where y = feed/gain, x = analyzed dietary CP ( g/kg ), r = dietary CP requirement ( g/kg ), l = the response at x = r, and u = the slope of the curve. In this model, y = l when x > r. 3. Results and discussion 3.1. Starter response to low-protein diets in starter phase The effects of low-protein diets on growth performance of Pekin ducks from d 1 to 19 are shown in Table 3. Lowering dietary CP from 203.3 to 168.6 g/kg had no linear or quadratic negative effects on body weight, weight gain and feed intake of ducks but feed/gain increased linearly (P = 0.017). Our results were different from those observed by Chen et al.(2016) and Wilson (1975) in which Pekin ducks given starter diets with 220 or 240 g CP /kg were considerably heavier at d 14 than those given diets with 180 or 200 g CP/kg. In their study, amino acid density decreased as dietary CP decreased and the deficiency of amino acids may lead to growth retardation of ducks fed low-CP diets. Unlike the aforementioned studies, in 6
our study, the amino acids of all diets with varying dietary CP were adequate to support duck growth and the SID amino acid contents were all formulated to be the same, which may be the reason for the difference between our results and others. Furthermore, our results was supported by the early results of Siregar et al.(1982) in which there was no considerable difference in the 1 to 14d growth performance among Australian Pekin ducks fed diets with 180, 200, and 220 g dietary CP /kg. In their study, the diets with 180, 200, and 220 g dietary CP /kg had the similar total amino acid contents including Lys, Met, Thr, Val, Leu, and Ile and it indicated that the amino acids of their low-protein diets were balanced well. These similar phenomena were also observed in finishing muscovy ducks from 8 to 12 wk of age (Baeza and Leclercq, 1998) and grower Pekin ducks from 14 to 35 d of age (Xie et al. 2017 ). In their study, lowering dietary CP by 3% had no considerable negative effects on final body weight, weight gain, and feed intake when the amino acids in diets were balanced by supplementation of crystalline amino acids. In our study, although the breast meat percentage of starter ducklings was not influenced by reducing dietary CP (Table 4), the leg meat percentage decreased linearly (P = 0.024) and abdominal fat percentage increased linearly (P = 0.018).
For starter ducks, Leg meat
developed more earlier and faster than breast meat, which was supported by our data in which leg meat had much higher percentage than breast meat during starter period (Table 4). Therefore, compared with breast meat, leg meat may be more sensitive to decreasing dietary CP and the ducks had the lowest percentage of leg meat when dietary CP was reduced to 168.6 g/kg (Table 4). The reduction of meat yield at low CP level may be due to decreasing nitrogen retention at this instance. In Pekin ducks from 17 to 19 d of age, the nitrogen retention was reduced by about 3% when dietary CP decreased from 190 to 150 g/kg (Zeng et al., 2015). On the other hand, the increase of abdominal fat at low-CP levels in our study was supported by Siregar et al.(1982) who found that the carcass fat of 2-week-old ducklings 7
increased as dietary CP decreased from 220 to 180 g/kg. The increasing fat deposition caused by low-CP diet may be explained by amino acid imbalance in diets. As dietary CP decreased, more and more other amino acid would be growth-limiting and thus it would lead to amino acid imbalance. This amino acid imbalance was most likely to lead to increasing amino acid catabolism and the carbon skeletons from amino acids would be converted to intermediates for carbohydrate and lipid biosynthesis, which may be an explanation for increasing fat deposition at low dietary CP level. A low-protein diets are an useful nutritional strategy to reduce nitrogen excretion and ammonia emission from poultry houses (Hernández, et al., 2012; Namroud, et al., 2008; Ospina-Rojas et al., 2014).
In our study, the CP intake decreased linearly (P = 0.010) or
quadratically (P = 0.001) as dietary CP decreased to 168.6 g/kg (Table 3), which indicated the possible reduction of the ammonia emission and nitrogen excretion when low-CP diet was used. In our study, the broken-line regression was used to predict the minimum protein requirement of starter ducks. According to these regression [ y = 1.426 + 0.0027× ( 196.8 x ), P = 0.035, R2 = 0.893 ], the estimated protein requirements for feed/gain (Figure 1) was 196.8 g/kg and the estimated feed/gain ( 1.426 ) were identical with the observed response data in which the feed/gain was optimized when dietary CP was 203.3g/kg (Table 3). The estimated protein requirements of starter ducks was lower than the NRC (1994) recommendation (22%) for Pekin ducks from 0 to 2 wk of age and it also indicated that dietary CP level could be reduced when the amino acids in diet was balanced well. 3.2 Subsequent grower response to low-protein diets in starter phase The effects of low-protein diets in starter phase on growth performance and carcass traits of Pekin ducks from 20 to 35 d of age are presented in Table 3 and 4. Although higher feed/gain and more abdominal fat were caused by low-CP diets during starter period, the protein restriction during starter period had no linear or quadratic negative effects on body 8
weight and weight gain of ducks during subsequent grower period and it was the same for yield of carcass, breast and leg meat, and abdominal fat. Moreover, as dietary CP decreased, the feed intake of grower ducks decreased linearly (P = 0.007) and it may lead to the linear decrease of feed/ gain (P = 0.008), which indicated the improvement of feed efficiency. Our results were supported by the results in broilers of Moran (1979) and Plavnik and Hurwitz (1990).
In their study, when the low-protein diets were fed to broiler chickens as a way to
restrict early growth, the broiler chickens showed poor body weight and feed efficiency during restriction period. After that protein restriction was removed during the subsequent grower period, the loss of body weight and feed efficiency were recovered and the yields of thigh meat, breast meat, and carcass at market age were not influenced by early protein restriction. Therefore, the later growth could compensate for the earlier poor growth performance and carcass yield caused by low-protein diets.
4. Conclusion According to broken-line regression, the 196.8g/kg was the minimum dietary CP requirement necessary to obtain the optimal feed/gain during the starter period. Reducing dietary CP had negative effects on the performance of starter ducks but the protein restriction during the starter phase had no adverse effects on the performance of grower Pekin ducks.
Conflict of interest statement There is no conflict of interest.
Acknowledgments Our research was sponsored by the Earmarked Fund for China's Agriculture Research System (CARS-42, Beijing, China) and the Science and Technology Innovation Project of the 9
Chinese Academy of Agricultural Sciences (cxgc-ias-09, Beijing, China).
References Award, E.A., Fadlullah, M., Zulkifli, I., Farjam, A.S., Chwen, L.T., 2014. Amino acids fortification of low-protein diet for broilers under tropical climate: ideal essential amino acids profile. Ital. J. Anim. Sci. 13, 3166-3170. Baeza, E., Leclercq, B., 1998. Use of industrial amino acids to allow low protein concentrations in finishing diets for growing Muscovy ducks. Br. Poult. Sci. 39, 90-96. Chen, X., Murdoch, R., Zhang, Q., Shafer, D., J. Applegate, T.J., 2016. Effects of dietary protein concentration on performance and nutrient digestibility in Pekin ducks during aflatoxicosis. Poult. Sci. 95, 834-841. Hernández, F. López, M., Martínez, S., Megías, M.D., Catalá, P., Madrid, J., 2012. Effect of low-protein diets and single sex on production performance, plasma metabolites, digestibility, and nitrogen excretion in 1- to 48-day-old broilers. Poult. Sci. 91, 683-692. Jiang, Y., Uzma, M., Tang, J., Wen, Z.G., Hou, S.S., Huang, W., Xie, M., 2016. Effects of dietary protein on threonine requirements of Pekin ducks from hatch to 21 days of age. Anim. Feed Sci. Technol. 217, 95-99. Kerr, B.J., Kidd, M.T., 1999. Amino acid supplementation of low-protein broiler diets: 2. formulation a n ideal amino acid basis. J. Appl. Poult. Res. 8: 310-320. Kong, C., Adeola, O., 2013. Additivity of amino acid digestibility in corn and soybean meal for broiler chickens and White Pekin ducks. Poult. Sci. 92, 2381-2388. Ministry of Agriculture of China, 2004. Feeding Standard of Chicken. Standards Press of China, Beijing, China. Moran, E.T. Jr., 1979. Carcass quality changes with broiler chickens after dietary protein 10
restriction during the growing phase and finishing period compensatory growth. Poult. Sci. 58, 1257-1270. Namroud, N.F., Shivazad, M., Zaghari, M., 2008. Effects of fortifying low crude protein diet with crystalline amino acids on performance, blood ammonia level, and excreta characteristics of broiler chicks. Poult. Sci. 87, 2250-2258. NRC, 1994. Nutrient Requirements of Poultry. 9th rev. ed. Natl. Acad. Press, Washington, DC, US. Ospina-Rojas, I.C., Murakami, A.E., Eyng, C., Duarte. C.R.A., 2012. Commercially available amino acid supplementation of low-protein diets for broiler chickens with different ratios of digestible glycine+serine:lysine. Poult. Sci. 91, 3148-3155. Plavnik, I., Hurwitz, S., 1990. Performance of broiler chickens and turkey poults subjected to feed restriction or to feeding of low-protein or low-sodium diets at an early age. Poult. Sci. 69, 945-952. Robbins, K.R., Saxton, A.M., Southern, L.L., 2006. Estimation of nutrient requirements using broken-line regression analysis. J. Anim. Sci. 84, E155-E165. SAS Institute, 2003. SAS User's Guide: Statistics.SAS Inst. Inc., Cary, NC, US. Siregar, A.P., Cumming, R.B. Farrell, D.J., 1982. The nutrition of meat-type ducks. І the effects of dietary protein in isoenergetic diets on biological performance. Australian J. Agri. Res. 33, 857-864. Standardization Administration of China, 1994. Method for the Determination of Crude Protein in Feedstuffs.Standards Press of China, Beijing, China. Standardization Administration of China, 2000. Determination of Amino Acids in Feeds. Standards Press of China, Beijing, China. Xie, M., Zhang, L., Wen, Z.G., Tang, J., Huang, W., Hou, S.S., 2014. Threonine requirement of White Pekin ducks from hatch to 21 d of age. Br. Poult. Sci. 55, 553-557. 11
Xie, M., Jiang, Y., Tang, J., Wen, Z.G., Zhang, Q., Huang, W., Hou, S.S., 2017. Effects of low-protein diets on growth performance and carcass yield of growing White Pekin ducks. Poult. Sci, 96, 1370-1375. Wilson, B.J., 1975. The performance of male ducklings given starter diets with different concentrations of energy and protein. Br. Poult. Sci. 16, 617-625. Zeng, Q.F., Cherry, P., Doster, A., Murdoch, R., Adeola, O., Applegate, T.J., 2015. Effect of dietary energy and protein content on growth and carcass traits of Pekin ducks. Poult. Sci. 94, 384-394.
1.54
P=0.035, R2=0.893 Breakpoint = 196.8g/kg 95%CI=177.3 to 216.4 g/kg
Feed / gain, g/g
1.52 1.50 1.48 1.46 1.44 1.42 1.40 160
170
180
190
200
210
Dietary CP, g/kg
Figure 1. Fitted broken-line plot of 1-19d feed/gain as a function of dietary CP level. Broken-line equation is y = 1.426 + 0.0027× ( 196.8 - x ), y=1.426 when x > 196.8. 95 g/kg CI = 95% confidence interval of the breakpoint.
12
Table 1. Composition of Lowest-CP diet and Highest-CP diets from 1 to 19 d of age and common grower diets from 20 to 35 d of age (as-fed). Item
Lowest-CP diet
Highest-CP diet
Grower diet
Ingredients, g / kg Corn Soybean meal Sodium chloride Dicalcium phosphate Limestone Soybean oil Vitamin and mineral premixa DL-Met L-Lys·HCl L-Trp L-Arg L-Ile L-Thr L-Val Gly Corn starch Total Calculated composition Metabolizable energyb, MJ / kg Crude protein, g / kg
744.7
577.0
657.0
195.0 3. 0 15.5 11.0 10.0 2.2 6.3 0.6 3.7 2.3 2. 0 1.9 1.8 1,000. 0
340.0 3.0 15.0 10.0 24.2 10.0 1.7 2.7 0.4 16.0 1,000.0
280.0 3.0 16.0 9.0 24.0 10.0 1.0 1,000.0
12.05 160.0 8.3
12.05 210.0 8.3
12.56 180.0 8.0
Ca, g / kg Nonphytate P, g / kg 3.9 3.9 4.0 Analyzed compositionc , g / kg Crude protein, g / kg 168.6 203.3 184.0 Met, g / kg 4.8 (4.5) 4.7 (4.5) 4.1 Cys, g / kg 2.7 (2.5) 3.3 (3.0) 3.0 Lys, g / kg 13.0 (11.0) 13.2 (11.0) 10.0 Trp, g / kg 2.3 (2.2) 2.5 (2.2) 2.2 Arg, g / kg 13.3 (12.5) 13.5 (12.5) 11.9 Ile, g / kg 8.8 (7.2) 9.2 (7.2) 7.9 Thr, g / kg 7.9 (7.5) 7.7 (7.5) 7.1 Val, g / kg 9.3 (8.2) 9.6 (8.2) 8.9 Gly, g / kg 8.3 (7.2) 8.5 (7.2) 7.7 Ser, g / kg 7.8 (7.2) 10.1 (9.6) 9.2 a Supplied per kilogram of total diet: Cu (CuSO4•5H2O), 8 mg; Fe (FeSO4•7H2O), 60 mg; Zn (ZnO), 60 mg; Mn (MnSO4•H2O), 100 mg; Se (NaSeO3), 0.3 mg; I (KI), 0.4 mg; choline chloride, 1,000 mg; vitamin A (retinyl acetate), 1,376 µg; vitamin D3 (cholecalciferol), 50 µg; vitamin E (DL-α-tocopheryl acetate), 20 mg; vitamin K3 (menadione sodium bisulfate), 2 mg; thiamin (thiamin mononitrate), 2 mg; riboflavin, 10 mg; pyridoxine hydrochloride, 4 mg; cobalamin, 0.02 mg; calcium-D-pantothenate, 20 mg; folic acid, 1 mg; and biotin, 0.15 mg. b
The value was calculated according to the apparent metabolisable energy of broiler chickens (Ministry of Agriculture of
China, 2004). c
The values in parentheses are calculated standardized ileal digestible amino acids.
Table 2 Analyzed concentration of nutrients of experimental starter diets on an as-fed basis. 13
Item
Formulated crude protein (g/kg)
Crude protein, g/kg
160.0 168.6
Indispensable amino acid, g/kg Met 4.8 Lys 13.0 Thr 7.9 Trp 2.3 Arg 13.3 Ile 8.8 Leu 14.5 Val 9.3 His 4.2 Phe 7.9 Dispensable amino acid, g/kg Ala 8.6 Asp 15.1 Cys 2.7 Glu 28.4 Gly 8.3 Ser 7.8 Pro
10.2
170.0 178.9
180.0 184.2
190.0 192.0
200.0 195.8
210.0 203.3
4.6 12.4 7.6 2.2 12.7 8.5 14.6 9.1 4.4 7.9
4.7 12.9 7.8 2.3 13.2 8.9 15.6 9.4 4.9 8.9
4.8 13.1 7.8 2.3 13.4 9.0 16.1 9.4 5.1 9.4
4.8 13.3 7.8 2.4 13.6 9.2 16.9 9.7 5.4 10.0
4.7 13.2 7.7 2.5 13.5 9.2 17.5 9.6 5.6 10.4
8.7 15.6 3.1 29.0 8.1 7.9
9.2 17.5 3.0 31.6 8.3 8.7
9.5 18.6 3.2 33.2 8.4 9.1
9.9 20.0 3.1 35.3 8.5 9.7
10.3 21.0 3.3 36.8 8.5 10.1
10.2
10.6
11.2
11.7
12.2
Table 3 Effects of various dietary crude protein contents during the starter phase on growth
performance of starter and subsequent grower Pekin ducks a. Item
Analyzed dietary CPb (g/kg) 168.6 178.9 184.2
SEM 192.0
195.8
203.3
P-value Linear
Quadratic Starter phase ( d0 to 19) Initial weight, g/duck 48.2 47.9 48.0 48.6 48.2 47.7 0.2 0.763 0.787 d 19 weight, g/duck 958.3 958.8 949.2 944.8 987.6 976.2 16.1 0.325 0.457 Daily gain, g/duck 47.9 47.9 47.4 47.2 49.4 48.9 0.9 0.306 0.413 Daily CP intake, g/duck 12.2 12. 5 12.8 13.7 13.7 14.2 0.3 0.010 0.001 Daily feed intake, g/duck 72.2 70.1 69.2 71.4 70.1 69.7 1.3 0.382 0.519 Feed/gainc, g/g 1.507 1.462 1.461 1.455 1.419 1.426 0.017 0.017 0.065 Mortality, % 3.13 3.13 0.00 3.13 3.13 1.56 2.25 0.707 0.909 Grower phase (d20 to 35) d 35 weight, g/duck 2,636.9 2,622.3 2,616.2 2,636.9 2,634.4 2,642.9 39.0 0.427 0.168 Daily gain, g/duck 103.5 103 104.7 106.4 102.3 103.8 2.2 0.848 0.851 Daily feed intake, g/duck 221.4 224.2 228.2 230.7 228.3 231.7 4.6 0.007 0.033 Feed/gain, g/g 2.14 2.18 2.18 2.18 2.23 2.24 0.04 0.008 0.051 a These ducks were fed with experimental diets with different dietary CP from hatch to 19 d of age and then with the same standard growing diets from 20 to 35 d of age. b
All diets were formulated to have the same standardized ileal digestible amino acid contents including Met, Lys, Thr,
Trp, Arg, Ile, Val, and Gly. c
Feed/gain was adjusted for corrected for mortality.
14
Table 4 Effects of various dietary crude protein contents during the starter phase on carcass
traits of starter and subsequent grower Pekin ducks a. Analyzed dietary CPb (g/kg) 168.6 178.9 184.2 192.0
Item
SEM 195.8
203.3
P-value Linear
Quadratic d 19 Breast meat, % 0.427 0.707 2.63 2.61 2.6 2.73 2.79 2.62 0.12 Leg meat, % 0.024 0.100 11.2 11.4 11.8 11.6 11.7 11.9 0.25 Abdominal fat, % 0.018 0.085 0.43 0.43 0.34 0.34 0.32 0.32 0.03 d 35 Carcass, % 0.135 0.206 73.9 73.3 73.5 73.3 73.5 73.3 0.5 Breast meat, % 0.325 0.302 10.9 10.9 10.4 10.5 10.6 10.7 0.3 Leg meat, % 0.746 0.892 10.1 10.0 10.4 10.1 9.9 10.1 0.2 Abdominal fat, % 0.177 0.458 0.61 0.63 0.6 0.58 0.54 0.59 0.04 a These ducks were fed with experimental diets with different dietary CP from d 0 to d 19 d of age and then with 1 common grower diets from 20 to 35 d of age. b
All diets were formulated to have the same standardized ileal digestible amino acid contents including Met, Lys, Thr, Trp,
Arg, Ile, Val, and Gly.
Highlights
Low-protein diet led to poorer feed efficiency and more abdominal fat in starter Pekin ducks. The 196.8g/kg was the minimum dietary CP requirement necessary to obtain the optimal feed/gain during the starter period. Starter protein restriction had no subsequent negative effects on performance of growing ducks.
15
PII: DOI: Reference:
S1871-1413(17)30201-9 http://dx.doi.org/10.1016/j.livsci.2017.07.005 LIVSCI3256
To appear in: Livestock Science Received date: 22 January 2017 Revised date: 13 June 2017 Accepted date: 7 July 2017 Cite this article as: M. Xie, Y. Jiang, J. Tang, Q. Zhang, W. Huang and S.S. Hou, Starter and subsequent grower response of Pekin ducks to low-protein diets in starter phase, Livestock Science, http://dx.doi.org/10.1016/j.livsci.2017.07.005 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Starter and subsequent grower response of Pekin ducks to low-protein diets in starter phase M. Xie, Y. Jiang, J. Tang, Q. Zhang, W. Huang, S.S. Hou* State Key Laboratory of Animal Nutrition, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing, 100193, China *
Corresponding author. Tel.: +86 10 6281 6227; fax: +86 10 6281 5832. [email protected]
Abstract A dose-response experiment was conducted to investigate the effects of feeding 6 starter diets containing the analyzed crude protein (CP) contents (168.6, 178.9, 184.2, 192.0, 195.8, and 203.3 g/kg) from d 1 to 19 on growth performance and carcass traits of starter Pekin ducks and the subsequent growth performance and carcass traits of ducks fed a common grower diet from d 20 to 35. The 480 one-d-old male White Pekin ducks were divided to 6 experimental treatments and each treatment had 8 replicate pens of 10 ducks. All starter experimental diets were formulated to contain similar dietary energy concentration and standardized ileal digestible amino acid contents. At d 19 and 35, the growth performance of each pen were determined and 2 ducks were randomly selected from each pen and harvested to evaluate carcass traits. During the starter period, as dietary CP decreased from 203.3 to 168.6 g/kg, the body weight, weight gain, and feed intake were not affected but feed/gain increased linearly (P = 0.017). According to broken-line regression, the 196.8g/kg was the minimum dietary CP requirement necessary to obtain the optimal feed/gain during the starter period. Moreover, the breast meat percentage of starter ducklings was not influenced by reducing dietary CP, but the leg meat percentage decreased linearly (P = 0.024) and abdominal fat percentage increased linearly (P = 0.018). During the grower period from d 20 to 35, the protein restriction during the starter phase had no negative effects on the subsequent growth 1
performance from d 20 to 35 or carcass traits at d 35. It was concluded that reducing dietary CP had negative effects on the performance of starter ducks but the protein restriction during the starter phase had no adverse effects on the performance of grower Pekin ducks. Keywords: Duck; Protein; Growth response.
1. Introduction With use of crystalline amino acids in diet formulation, it was possible to reduce dietary crude protein (CP) without negative effects on growth performance and carcass yield and it was also accompanied with the environmental benefit of less nitrogen excretion and ammonia emission. The research on the use of low-protein diets in ducks was very few. In grower muscovy ducks from 8 to 12 wk of age, no substantial modifications in growth performance or carcass quality were observed when dietary CP was reduced from 160 or 150 to 120 g/kg based on similar digestible amino acid contents (Baeza and Leclercq, 1998). In grower Pekin ducks, based on a constant standardized ileal digestible amino acid contents, it was possible to formulate the low-protein diets containing about 15% CP for Pekin ducks without adverse effects on the growth performance and carcass yield of these ducks (Xie et al., 2017). In starter Australian Pekin ducks from 1 to 14 d of age, , when the total amino acid contents kept constant in all diets, the growth performance was not changed markedly among the ducks fed diets with 180, 200, and 220 g CP/kg , respectively (Siregar et al., 1982). However, Chen et al.(2016) and Wilson (1975) found that Pekin ducks given starter diets with 220 or 240 g CP/kg were substantially heavier at d 14 than those given diets with 180 or 200 g CP / kg. Therefore, the use of low-protein diet in starter ducks is debating and the research on this topic should be continued. Recently, it is feasible for broilers to reduce dietary CP by 3% without undermining the performance of early stage broiler chickens (Award et al., 2014; Ospina-Rojas et al., 2014). 2
However, when dietary CP was reduced by more than 3% during the starter period, the broiler chickens fed low-CP diets could not have the growth performance which was equal to that of the broiler chickens fed high-CP diets (Namroud, et al., 2008). Fortunately, the early protein restriction could not influence the subsequent growth of broiler chickens. In the studies of Moran (1979) and Plavnik and Hurwitz, (1990), although the poor body weight and feed efficiency of broiler chickens was caused by low-protein diets during the starter period, the growth performance and the carcass or meat yield at market age would not be reduced markedly by early protein restriction during the starter period. Therefore, it can be hypothesized that the later growth can compensate for the starter growth loss caused by low-CP diets. In broiler chickens, in order to keep amino acid balance, the formulation of low-protein diets was based on the similar total or digestible amino acid contents (Award et al., 2014; Kerr and Kidd, 1999; Namroud et al., 2008; Ospina-Rojas et al., 2014). In Pekin ducks, when dietary amino acids did not keep constant in all diets and the amino acid density decreased as dietary CP decreased, the poorer growth performance would be caused by low-protein diets compared with ducks fed high-protein diets (Chen et al., 2016; Wilson, 1975). Currently, the standardized ileal digestibilities (SID) of amino acids in corn and soybean meal for Pekin ducks were determined successfully and the additivity of SID amino acids in the mixed diets including these 2 feedstuffs was confirmed (Kong and Adeola, 2013). Moreover, Xie et al.(2017) have successfully developed the low-protein diet for grower Pekin ducks based on the SID amino acids and thus it was reasonable to formulate low-protein diet on the SID amino acid basis . Therefore, the objective of our study was to examine the effects of feeding low-protein starter diets with similar SID amino acid contents from d 1 to d 19 on growth performance and carcass traits of starter Pekin ducks and the subsequent growth performance and carcass traits of ducks fed a common grower diet from d 20 to 35. 3
2. Materials and methods 2.1. Experimental design and duck husbandry All procedures of our experiments were approved by the animal care and use committee of Institute of Animal Sciences of Chinese Academy of Agricultural Sciences (Beijing, China). A dose-response experiment with 6 diets based on the analyzed CP contents was used in the study. The 480 one-d-old male White Pekin ducks were allocated randomly to 6 experimental treatments and each treatment contained 8 replicate pens of 10 ducks. All ducks were fed experimental starter diets from 1 to 19 d of age and then only 1 common grower diet with 184.0 g analyzed CP/kg from 20 to 35 d of age. Ducks were reared in raised wire-floor pens (2 m2/pen) from 1 to 35 d of age. During these periods, ducks had free access to water and feed. Water was provided by drip-nipple water supply lines and feed was fed in pellet form (1.5 mm for starter diets and 3 mm for grower diets). In the duck barn, lighting was continuous. The temperature was kept at 33°C from 1 to 3 d of age and then it was reduced gradually to approximately 25°C until 14 d of age and was kept at approximately 16 to 22°C thereafter. 2.2. Diet and feed analysis To keep similar SID amino acid contents, the experimental starter diets with 6 dietary CP concentrations were prepared by mixing highest-CP and lowest-CP diets (Table 1) according to dilution technology (Xie et al., 2017). Firstly, the CP concentrations of corn and soybean meal were determined by Kjeldahl procedure according to the method recommended by Standardization Administration of China (1994). The amino acids of these 2 feedstuffs were analyzed by using ion-exchange chromatography with an amino acid analyzer (L-800; Hitachi, Tokyo, Japan) according to the method recommended by Standardization Administration of China (2000). Tryptophan was analyzed by reverse-phase high performance liquid chromatography and fluorometric detection (Waters, Inc., Milford, US) 4
after alkali hydrolysis at 110°C for 20 h with 4M barium hydroxide. Afterwards, according to the analyzed amino acids of corn and soybean meal and the SID of amino acids in corn and soybean meal for Pekin ducks published by Kong and Adeola (2013), the SID amino acid contents of corn and soybean meal were calculated by multiplying analyzed amino acid contents by SID of the corresponding feedstuffs, respectively. The highest-CP and lowest-CP diet were all formulated to have the same SID amino acid contents including Met, Lys, Thr, Trp, Arg, Ile, Val, and Gly, with formulated dietary CP of 160.0 and 210.0 g/kg for these 2 diets, respectively. Supplemental crystalline amino acids were assumed to be 100% SID digestible. These 2 diets also had similar dietary energy concentrations. The contents of Lys, Met, Arg, Ile, Trp, and Val of these two diets met the NRC(1994) recommendation of Pekin ducks from 0 to 2 wk of age. Dietary threonine content of these two diets met the requirements provided by Xie et al. ( 2014 ) and Jiang et al.( 2016 ) and their glycine+serine content met the NRC (1994) recommendation of broilers from 0 to 3 wk of age due to the lack of this value for ducks. The experimental diets with 6 formulated dietary CP contents ( 160, 170, 180, 190, 200, and 210 g/kg ) were produced by blending the lowest-CP and highest-CP according to different mixing ratio of these 2 diets (5:0, 4:1, 3:2, 2:3, 1:4, and 0:5 ). All experimental diets were cold-pelleted at room temperature and the CP and amino acids of these diets were also analyzed ( Table 2 ) according to the aforementioned methods. The analyzed dietary CP contents of these 6 experimental diets were 168.6, 178.9, 184.2, 192.0, 195.8, and 203.3 g/kg, respectively. In addition, the CP and amino acids of common grower diets ( Table 1 ) were also analyzed by the aforementioned methods. 2.3. Experimental data collection At d 19 and d 35, the weight gain, feed intake and feed/gain of each pen were determined and feed intake and feed/gain were adjusted for mortality. In addition, 2 ducks were randomly 5
selected from each pen at d 19 and 35, fasted for 12h, and harvested by cutting neck and eviscerated manually. The abdominal fat, breast meat (including pectoralis major and pectoralis minor), and leg meat (including thigh and drum stick) were all removed manually from carcasses and weighed, and the percentages relative to live body weight at processing were also calculated. Breast and leg meat were all skinless and boneless. 2.4. Statistical analysis The data were analyzed using SAS software (SAS Inst. Inc., Cary NC, US), and the pen was the experimental unit for analysis. Linear and quadratic polynomial contrasts were used to determine the effect of dietary CP. The variability in the data was expressed as the standard error of the means. A probability level of P < 0.05 was considered to be statistically significant. In present study, the broken-line regression analysis (Robbins et al., 2006) was used to estimate the minimum CP requirements of starter ducks using the NLIN procedure of SAS software (SAS Inst. Inc., Cary NC, US). The broken-line model was: y = l + u (r - x), where y = feed/gain, x = analyzed dietary CP ( g/kg ), r = dietary CP requirement ( g/kg ), l = the response at x = r, and u = the slope of the curve. In this model, y = l when x > r. 3. Results and discussion 3.1. Starter response to low-protein diets in starter phase The effects of low-protein diets on growth performance of Pekin ducks from d 1 to 19 are shown in Table 3. Lowering dietary CP from 203.3 to 168.6 g/kg had no linear or quadratic negative effects on body weight, weight gain and feed intake of ducks but feed/gain increased linearly (P = 0.017). Our results were different from those observed by Chen et al.(2016) and Wilson (1975) in which Pekin ducks given starter diets with 220 or 240 g CP /kg were considerably heavier at d 14 than those given diets with 180 or 200 g CP/kg. In their study, amino acid density decreased as dietary CP decreased and the deficiency of amino acids may lead to growth retardation of ducks fed low-CP diets. Unlike the aforementioned studies, in 6
our study, the amino acids of all diets with varying dietary CP were adequate to support duck growth and the SID amino acid contents were all formulated to be the same, which may be the reason for the difference between our results and others. Furthermore, our results was supported by the early results of Siregar et al.(1982) in which there was no considerable difference in the 1 to 14d growth performance among Australian Pekin ducks fed diets with 180, 200, and 220 g dietary CP /kg. In their study, the diets with 180, 200, and 220 g dietary CP /kg had the similar total amino acid contents including Lys, Met, Thr, Val, Leu, and Ile and it indicated that the amino acids of their low-protein diets were balanced well. These similar phenomena were also observed in finishing muscovy ducks from 8 to 12 wk of age (Baeza and Leclercq, 1998) and grower Pekin ducks from 14 to 35 d of age (Xie et al. 2017 ). In their study, lowering dietary CP by 3% had no considerable negative effects on final body weight, weight gain, and feed intake when the amino acids in diets were balanced by supplementation of crystalline amino acids. In our study, although the breast meat percentage of starter ducklings was not influenced by reducing dietary CP (Table 4), the leg meat percentage decreased linearly (P = 0.024) and abdominal fat percentage increased linearly (P = 0.018).
For starter ducks, Leg meat
developed more earlier and faster than breast meat, which was supported by our data in which leg meat had much higher percentage than breast meat during starter period (Table 4). Therefore, compared with breast meat, leg meat may be more sensitive to decreasing dietary CP and the ducks had the lowest percentage of leg meat when dietary CP was reduced to 168.6 g/kg (Table 4). The reduction of meat yield at low CP level may be due to decreasing nitrogen retention at this instance. In Pekin ducks from 17 to 19 d of age, the nitrogen retention was reduced by about 3% when dietary CP decreased from 190 to 150 g/kg (Zeng et al., 2015). On the other hand, the increase of abdominal fat at low-CP levels in our study was supported by Siregar et al.(1982) who found that the carcass fat of 2-week-old ducklings 7
increased as dietary CP decreased from 220 to 180 g/kg. The increasing fat deposition caused by low-CP diet may be explained by amino acid imbalance in diets. As dietary CP decreased, more and more other amino acid would be growth-limiting and thus it would lead to amino acid imbalance. This amino acid imbalance was most likely to lead to increasing amino acid catabolism and the carbon skeletons from amino acids would be converted to intermediates for carbohydrate and lipid biosynthesis, which may be an explanation for increasing fat deposition at low dietary CP level. A low-protein diets are an useful nutritional strategy to reduce nitrogen excretion and ammonia emission from poultry houses (Hernández, et al., 2012; Namroud, et al., 2008; Ospina-Rojas et al., 2014).
In our study, the CP intake decreased linearly (P = 0.010) or
quadratically (P = 0.001) as dietary CP decreased to 168.6 g/kg (Table 3), which indicated the possible reduction of the ammonia emission and nitrogen excretion when low-CP diet was used. In our study, the broken-line regression was used to predict the minimum protein requirement of starter ducks. According to these regression [ y = 1.426 + 0.0027× ( 196.8 x ), P = 0.035, R2 = 0.893 ], the estimated protein requirements for feed/gain (Figure 1) was 196.8 g/kg and the estimated feed/gain ( 1.426 ) were identical with the observed response data in which the feed/gain was optimized when dietary CP was 203.3g/kg (Table 3). The estimated protein requirements of starter ducks was lower than the NRC (1994) recommendation (22%) for Pekin ducks from 0 to 2 wk of age and it also indicated that dietary CP level could be reduced when the amino acids in diet was balanced well. 3.2 Subsequent grower response to low-protein diets in starter phase The effects of low-protein diets in starter phase on growth performance and carcass traits of Pekin ducks from 20 to 35 d of age are presented in Table 3 and 4. Although higher feed/gain and more abdominal fat were caused by low-CP diets during starter period, the protein restriction during starter period had no linear or quadratic negative effects on body 8
weight and weight gain of ducks during subsequent grower period and it was the same for yield of carcass, breast and leg meat, and abdominal fat. Moreover, as dietary CP decreased, the feed intake of grower ducks decreased linearly (P = 0.007) and it may lead to the linear decrease of feed/ gain (P = 0.008), which indicated the improvement of feed efficiency. Our results were supported by the results in broilers of Moran (1979) and Plavnik and Hurwitz (1990).
In their study, when the low-protein diets were fed to broiler chickens as a way to
restrict early growth, the broiler chickens showed poor body weight and feed efficiency during restriction period. After that protein restriction was removed during the subsequent grower period, the loss of body weight and feed efficiency were recovered and the yields of thigh meat, breast meat, and carcass at market age were not influenced by early protein restriction. Therefore, the later growth could compensate for the earlier poor growth performance and carcass yield caused by low-protein diets.
4. Conclusion According to broken-line regression, the 196.8g/kg was the minimum dietary CP requirement necessary to obtain the optimal feed/gain during the starter period. Reducing dietary CP had negative effects on the performance of starter ducks but the protein restriction during the starter phase had no adverse effects on the performance of grower Pekin ducks.
Conflict of interest statement There is no conflict of interest.
Acknowledgments Our research was sponsored by the Earmarked Fund for China's Agriculture Research System (CARS-42, Beijing, China) and the Science and Technology Innovation Project of the 9
Chinese Academy of Agricultural Sciences (cxgc-ias-09, Beijing, China).
References Award, E.A., Fadlullah, M., Zulkifli, I., Farjam, A.S., Chwen, L.T., 2014. Amino acids fortification of low-protein diet for broilers under tropical climate: ideal essential amino acids profile. Ital. J. Anim. Sci. 13, 3166-3170. Baeza, E., Leclercq, B., 1998. Use of industrial amino acids to allow low protein concentrations in finishing diets for growing Muscovy ducks. Br. Poult. Sci. 39, 90-96. Chen, X., Murdoch, R., Zhang, Q., Shafer, D., J. Applegate, T.J., 2016. Effects of dietary protein concentration on performance and nutrient digestibility in Pekin ducks during aflatoxicosis. Poult. Sci. 95, 834-841. Hernández, F. López, M., Martínez, S., Megías, M.D., Catalá, P., Madrid, J., 2012. Effect of low-protein diets and single sex on production performance, plasma metabolites, digestibility, and nitrogen excretion in 1- to 48-day-old broilers. Poult. Sci. 91, 683-692. Jiang, Y., Uzma, M., Tang, J., Wen, Z.G., Hou, S.S., Huang, W., Xie, M., 2016. Effects of dietary protein on threonine requirements of Pekin ducks from hatch to 21 days of age. Anim. Feed Sci. Technol. 217, 95-99. Kerr, B.J., Kidd, M.T., 1999. Amino acid supplementation of low-protein broiler diets: 2. formulation a n ideal amino acid basis. J. Appl. Poult. Res. 8: 310-320. Kong, C., Adeola, O., 2013. Additivity of amino acid digestibility in corn and soybean meal for broiler chickens and White Pekin ducks. Poult. Sci. 92, 2381-2388. Ministry of Agriculture of China, 2004. Feeding Standard of Chicken. Standards Press of China, Beijing, China. Moran, E.T. Jr., 1979. Carcass quality changes with broiler chickens after dietary protein 10
restriction during the growing phase and finishing period compensatory growth. Poult. Sci. 58, 1257-1270. Namroud, N.F., Shivazad, M., Zaghari, M., 2008. Effects of fortifying low crude protein diet with crystalline amino acids on performance, blood ammonia level, and excreta characteristics of broiler chicks. Poult. Sci. 87, 2250-2258. NRC, 1994. Nutrient Requirements of Poultry. 9th rev. ed. Natl. Acad. Press, Washington, DC, US. Ospina-Rojas, I.C., Murakami, A.E., Eyng, C., Duarte. C.R.A., 2012. Commercially available amino acid supplementation of low-protein diets for broiler chickens with different ratios of digestible glycine+serine:lysine. Poult. Sci. 91, 3148-3155. Plavnik, I., Hurwitz, S., 1990. Performance of broiler chickens and turkey poults subjected to feed restriction or to feeding of low-protein or low-sodium diets at an early age. Poult. Sci. 69, 945-952. Robbins, K.R., Saxton, A.M., Southern, L.L., 2006. Estimation of nutrient requirements using broken-line regression analysis. J. Anim. Sci. 84, E155-E165. SAS Institute, 2003. SAS User's Guide: Statistics.SAS Inst. Inc., Cary, NC, US. Siregar, A.P., Cumming, R.B. Farrell, D.J., 1982. The nutrition of meat-type ducks. І the effects of dietary protein in isoenergetic diets on biological performance. Australian J. Agri. Res. 33, 857-864. Standardization Administration of China, 1994. Method for the Determination of Crude Protein in Feedstuffs.Standards Press of China, Beijing, China. Standardization Administration of China, 2000. Determination of Amino Acids in Feeds. Standards Press of China, Beijing, China. Xie, M., Zhang, L., Wen, Z.G., Tang, J., Huang, W., Hou, S.S., 2014. Threonine requirement of White Pekin ducks from hatch to 21 d of age. Br. Poult. Sci. 55, 553-557. 11
Xie, M., Jiang, Y., Tang, J., Wen, Z.G., Zhang, Q., Huang, W., Hou, S.S., 2017. Effects of low-protein diets on growth performance and carcass yield of growing White Pekin ducks. Poult. Sci, 96, 1370-1375. Wilson, B.J., 1975. The performance of male ducklings given starter diets with different concentrations of energy and protein. Br. Poult. Sci. 16, 617-625. Zeng, Q.F., Cherry, P., Doster, A., Murdoch, R., Adeola, O., Applegate, T.J., 2015. Effect of dietary energy and protein content on growth and carcass traits of Pekin ducks. Poult. Sci. 94, 384-394.
1.54
P=0.035, R2=0.893 Breakpoint = 196.8g/kg 95%CI=177.3 to 216.4 g/kg
Feed / gain, g/g
1.52 1.50 1.48 1.46 1.44 1.42 1.40 160
170
180
190
200
210
Dietary CP, g/kg
Figure 1. Fitted broken-line plot of 1-19d feed/gain as a function of dietary CP level. Broken-line equation is y = 1.426 + 0.0027× ( 196.8 - x ), y=1.426 when x > 196.8. 95 g/kg CI = 95% confidence interval of the breakpoint.
12
Table 1. Composition of Lowest-CP diet and Highest-CP diets from 1 to 19 d of age and common grower diets from 20 to 35 d of age (as-fed). Item
Lowest-CP diet
Highest-CP diet
Grower diet
Ingredients, g / kg Corn Soybean meal Sodium chloride Dicalcium phosphate Limestone Soybean oil Vitamin and mineral premixa DL-Met L-Lys·HCl L-Trp L-Arg L-Ile L-Thr L-Val Gly Corn starch Total Calculated composition Metabolizable energyb, MJ / kg Crude protein, g / kg
744.7
577.0
657.0
195.0 3. 0 15.5 11.0 10.0 2.2 6.3 0.6 3.7 2.3 2. 0 1.9 1.8 1,000. 0
340.0 3.0 15.0 10.0 24.2 10.0 1.7 2.7 0.4 16.0 1,000.0
280.0 3.0 16.0 9.0 24.0 10.0 1.0 1,000.0
12.05 160.0 8.3
12.05 210.0 8.3
12.56 180.0 8.0
Ca, g / kg Nonphytate P, g / kg 3.9 3.9 4.0 Analyzed compositionc , g / kg Crude protein, g / kg 168.6 203.3 184.0 Met, g / kg 4.8 (4.5) 4.7 (4.5) 4.1 Cys, g / kg 2.7 (2.5) 3.3 (3.0) 3.0 Lys, g / kg 13.0 (11.0) 13.2 (11.0) 10.0 Trp, g / kg 2.3 (2.2) 2.5 (2.2) 2.2 Arg, g / kg 13.3 (12.5) 13.5 (12.5) 11.9 Ile, g / kg 8.8 (7.2) 9.2 (7.2) 7.9 Thr, g / kg 7.9 (7.5) 7.7 (7.5) 7.1 Val, g / kg 9.3 (8.2) 9.6 (8.2) 8.9 Gly, g / kg 8.3 (7.2) 8.5 (7.2) 7.7 Ser, g / kg 7.8 (7.2) 10.1 (9.6) 9.2 a Supplied per kilogram of total diet: Cu (CuSO4•5H2O), 8 mg; Fe (FeSO4•7H2O), 60 mg; Zn (ZnO), 60 mg; Mn (MnSO4•H2O), 100 mg; Se (NaSeO3), 0.3 mg; I (KI), 0.4 mg; choline chloride, 1,000 mg; vitamin A (retinyl acetate), 1,376 µg; vitamin D3 (cholecalciferol), 50 µg; vitamin E (DL-α-tocopheryl acetate), 20 mg; vitamin K3 (menadione sodium bisulfate), 2 mg; thiamin (thiamin mononitrate), 2 mg; riboflavin, 10 mg; pyridoxine hydrochloride, 4 mg; cobalamin, 0.02 mg; calcium-D-pantothenate, 20 mg; folic acid, 1 mg; and biotin, 0.15 mg. b
The value was calculated according to the apparent metabolisable energy of broiler chickens (Ministry of Agriculture of
China, 2004). c
The values in parentheses are calculated standardized ileal digestible amino acids.
Table 2 Analyzed concentration of nutrients of experimental starter diets on an as-fed basis. 13
Item
Formulated crude protein (g/kg)
Crude protein, g/kg
160.0 168.6
Indispensable amino acid, g/kg Met 4.8 Lys 13.0 Thr 7.9 Trp 2.3 Arg 13.3 Ile 8.8 Leu 14.5 Val 9.3 His 4.2 Phe 7.9 Dispensable amino acid, g/kg Ala 8.6 Asp 15.1 Cys 2.7 Glu 28.4 Gly 8.3 Ser 7.8 Pro
10.2
170.0 178.9
180.0 184.2
190.0 192.0
200.0 195.8
210.0 203.3
4.6 12.4 7.6 2.2 12.7 8.5 14.6 9.1 4.4 7.9
4.7 12.9 7.8 2.3 13.2 8.9 15.6 9.4 4.9 8.9
4.8 13.1 7.8 2.3 13.4 9.0 16.1 9.4 5.1 9.4
4.8 13.3 7.8 2.4 13.6 9.2 16.9 9.7 5.4 10.0
4.7 13.2 7.7 2.5 13.5 9.2 17.5 9.6 5.6 10.4
8.7 15.6 3.1 29.0 8.1 7.9
9.2 17.5 3.0 31.6 8.3 8.7
9.5 18.6 3.2 33.2 8.4 9.1
9.9 20.0 3.1 35.3 8.5 9.7
10.3 21.0 3.3 36.8 8.5 10.1
10.2
10.6
11.2
11.7
12.2
Table 3 Effects of various dietary crude protein contents during the starter phase on growth
performance of starter and subsequent grower Pekin ducks a. Item
Analyzed dietary CPb (g/kg) 168.6 178.9 184.2
SEM 192.0
195.8
203.3
P-value Linear
Quadratic Starter phase ( d0 to 19) Initial weight, g/duck 48.2 47.9 48.0 48.6 48.2 47.7 0.2 0.763 0.787 d 19 weight, g/duck 958.3 958.8 949.2 944.8 987.6 976.2 16.1 0.325 0.457 Daily gain, g/duck 47.9 47.9 47.4 47.2 49.4 48.9 0.9 0.306 0.413 Daily CP intake, g/duck 12.2 12. 5 12.8 13.7 13.7 14.2 0.3 0.010 0.001 Daily feed intake, g/duck 72.2 70.1 69.2 71.4 70.1 69.7 1.3 0.382 0.519 Feed/gainc, g/g 1.507 1.462 1.461 1.455 1.419 1.426 0.017 0.017 0.065 Mortality, % 3.13 3.13 0.00 3.13 3.13 1.56 2.25 0.707 0.909 Grower phase (d20 to 35) d 35 weight, g/duck 2,636.9 2,622.3 2,616.2 2,636.9 2,634.4 2,642.9 39.0 0.427 0.168 Daily gain, g/duck 103.5 103 104.7 106.4 102.3 103.8 2.2 0.848 0.851 Daily feed intake, g/duck 221.4 224.2 228.2 230.7 228.3 231.7 4.6 0.007 0.033 Feed/gain, g/g 2.14 2.18 2.18 2.18 2.23 2.24 0.04 0.008 0.051 a These ducks were fed with experimental diets with different dietary CP from hatch to 19 d of age and then with the same standard growing diets from 20 to 35 d of age. b
All diets were formulated to have the same standardized ileal digestible amino acid contents including Met, Lys, Thr,
Trp, Arg, Ile, Val, and Gly. c
Feed/gain was adjusted for corrected for mortality.
14
Table 4 Effects of various dietary crude protein contents during the starter phase on carcass
traits of starter and subsequent grower Pekin ducks a. Analyzed dietary CPb (g/kg) 168.6 178.9 184.2 192.0
Item
SEM 195.8
203.3
P-value Linear
Quadratic d 19 Breast meat, % 0.427 0.707 2.63 2.61 2.6 2.73 2.79 2.62 0.12 Leg meat, % 0.024 0.100 11.2 11.4 11.8 11.6 11.7 11.9 0.25 Abdominal fat, % 0.018 0.085 0.43 0.43 0.34 0.34 0.32 0.32 0.03 d 35 Carcass, % 0.135 0.206 73.9 73.3 73.5 73.3 73.5 73.3 0.5 Breast meat, % 0.325 0.302 10.9 10.9 10.4 10.5 10.6 10.7 0.3 Leg meat, % 0.746 0.892 10.1 10.0 10.4 10.1 9.9 10.1 0.2 Abdominal fat, % 0.177 0.458 0.61 0.63 0.6 0.58 0.54 0.59 0.04 a These ducks were fed with experimental diets with different dietary CP from d 0 to d 19 d of age and then with 1 common grower diets from 20 to 35 d of age. b
All diets were formulated to have the same standardized ileal digestible amino acid contents including Met, Lys, Thr, Trp,
Arg, Ile, Val, and Gly.
Highlights
Low-protein diet led to poorer feed efficiency and more abdominal fat in starter Pekin ducks. The 196.8g/kg was the minimum dietary CP requirement necessary to obtain the optimal feed/gain during the starter period. Starter protein restriction had no subsequent negative effects on performance of growing ducks.
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