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Net energy and ractopamine levels for barrows weighing 70 to 100kg/ Niveis de energia liquida e ractopamina para suinos machos castrados dos 70 aos 100kg.

INTRODUCTION

Full expression of the potential of swine of high genetic standard requires diets that meet the animal nutritional requirements. One approach to achieve maximum feed efficiency and carcass quality is the addition of ractopamine to the diets of finishing pigs.

Ractopamine has been shown to improve performance and carcass characteristics (CORASSA et al., 2009) without affecting meat quality (ALMEIDA et al., 2010), while increasing daily weight gain, improving feed conversion, and reducing back-fat thickness, and increasing ribeye area, meat percentage, and carcass meat-to-fat ratios.

In swine, lysine concentrations in deposited protein are higher when diets are supplemented with ractopamine. However, the lysine-to-energy ratios and energy levels required for optimizing performance and carcass characteristics are higher than those recommended in the literature addressing dietary ractopamine (APPLE et al., 2004).

Reassessing the energy levels of diets supplemented with ractopamine is critical, since constraints to ractopamine activity may limit full expression of productive potential in swine.

The purpose of this study was to evaluate the effect of net energy and ractopamine levels, as well as their interaction, on the performance and carcass characteristics of finishing barrows weighing 70 to 100kg.

MATERIALS AND METHODS

One hundred and fifty barrows of a commercial line exhibiting high potential for protein deposition were used in this study. Mean initial weight was 70.80 [+ or -] 3.84kg. Animals were distributed in a randomized block design with a 5x3 factorial arrangement, comprising five levels of net energy (2,300; 2,425; 2,550; 2,675; and 2,800Kcal [kg.sup.-1] of diet) and three levels of ractopamine (5, 10, and 20ppm [kg.sup.-1] of diet), with five replicates, and two animals per experimental unit. Blocks were based on initial weight. The animals were housed in pens equipped with semi-automatic feeders and bite nipple drinkers, located in a masonry shed roofed with ceramic tiles.

The experimental diets (Table 1), prepared with soybean meal and corn, were supplemented with amino acids, minerals, and vitamins to meet the nutritional requirements proposed by ROSTAGNO et al. (2011) for barrows of high genetic potential and superior performance weighing 70 to 100kg. Dietary net energy was calculated based on the mean composition of raw materials (ROSTAGNO et al., 2011). Different energy levels were obtained by replacing kaolin with soybean oil while maintaining an optimal protein pattern across diets. Feed and water were provided ad libitum throughout the 30-day experimental period.

Animals were weighed at the beginning and end of the experiment. Weights of supplied feed, leftovers, and wastage were employed to calculate lysine and daily net energy intakes, as well as, daily weight gain and feed conversion for each experimental unit.

Following the final weighing, animals were transported to a commercial abattoir where they remained in stall rest with access to water, but without solid food, for 10h. For slaughter, the animals were subjected to electronarcosis and subsequently bled, scalded, and eviscerated.

At the end of the slaughter line, the heads were removed, carcasses halved lengthwise, and half-carcasses weighed individually. Left half-carcass was cut at P2 (the point corresponding to the orthogonal projection of the last rib 4cm from the spine) to expose the Longissimus dorsi and back-fat layer for measurements of muscle depth and back-fat thickness using digital calipers, before carcass temperature reduced.

Calculations of meat percentage and lean meat amount were based on hot carcass weight, back-fat thickness, and muscle depth using the equations proposed by BRIDI & SILVA (2007): lean meat percentage (%) = 60 - (back-fat thickness x 0.58) + (muscle depth x 0.1); lean meat amount (kg) = (hot carcass weight x lean meat percentage)/100.

Performance variables (weight gain, feed, energy intake, and feed conversion) and quantitative carcass traits (hot carcass weight, back-fat thickness, muscle depth, and carcass meat percentage) were subjected to analysis of variance (general linear model), using SAS software version 9.0. A 5% significance level was adopted. Initial weight was used as a covariate in the statistical model. Models of best fit were applied using linear and/or quadratic regressions to net energy and ractopamine levels.

RESULTS AND DISCUSSION

No effect of interaction (P>0.05) between net energy and ractopamine levels (Table 2) was observed on performance variables, corroborating the results obtained by MOURA et al. (2011a), who reported no effect of interaction between net energy (2,300; 2,424; 2,548; and 2,668Kcal [kg.sup.-1]) and ractopamine levels (0 and 20ppm) on the performance of finishing gilts subjected to high ambient temperatures.

No influence of net energy levels of the experimental diets was observed on final body weight (P>0.05), but feed intake decreased linearly (P<0.01) with increasing energy levels, a result explained by the fact that pigs can modify feed intake to adjust to dietary energy levels (REZENDE et al., 2006) the higher the dietary energy, the lower the voluntary feed intake. Therefore, finishing pigs provided diets with high energy densities, reduced voluntary consumption, and such diets have been associated with improved feed efficiency. The result corroborated the findings reported by KIL et al. (2011) for net energy levels of 2,056; 2,206; and 2,318Kcal [kg.sup.-1] and by QUINIOU & NOBLET (2012) for 3,100; 3,230; 3,370; and 3,500Kcal [kg.sup.-1].

No effect (P>0.05) of net energy levels on daily weight gain was observed. This response is possibly associated with the linear reduction in feed intake with increasing dietary energy levels. Similar results were reported by APPLE et al. (2004) for barrows and gilts and by MOURA et al. (2011a) for finishing gilts.

Feed conversion improved linearly (P<0.01) with increasing net energy levels. This result can be explained by the positive effects on nutrient digestibility of the oil used as an energy source, as well as by possible improvement in dietary energy-to-protein ratios. Similar results were obtained by PAIANO et al. (2008), who observed that feed conversion improved in finishing barrows and gilts fed diets with increasing net energy concentrations (2,410; 2,450; 2,490; 2,530; and 2,570Kcal [kg.sup.-1]), and by YI et al. (2010) who investigated the effects of net energy levels (2,250; 2,300; 2,400; and 2,450Kcal [kg.sup.-1]) in diets fed to pigs with 20-30kg live weight.

Moreover, ractopamine levels in the experimental diets did not affect performance variables (P>0.05). This absence of effect may be related to the range of body weights (70-100kg) in the experimental period, as prior research has demonstrated the benefits of ractopamine addition to the diets of pigs weighing over 100kg at slaughter time, particularly in terms of weight gain (CORASSA et al., 2009) and feed conversion (ALMEIDA et al., 2010). Genotypic features may be another reason why ractopamine did not affect performance, since variability in the genetic materials employed in different studies may affect the variables evaluated (HINSON et al., 2011).

No effect of interaction (P>0.05) between net energy and ractopamine levels was observed on carcass characteristics (Table 3). In addition, no effect of net energy levels (P>0.05) was observed on the quantitative characteristics of carcasses. These results suggested that the experimental diets provided the nutritional input required for the expression of productive potential. Similar results were obtained by MOURA et al. (2011a) for hot carcass weight and dressing percentage and by PAIANO et al. (2008) for hot carcass weight and yield. QUINIOU & NOBLET (2012), however, observed higher dressing percentages in barrows for net energy levels of 1,935; 2,078; 2,221; 2,365; 2,508; and 2,651Kcal [kg.sup.-1].

Net energy levels did not influence either muscle depth or back-fat thickness (P>0.05). This finding corroborates the results observed for net energy intake, which did not vary across diets, indicating that energy intake was regulated by dietary energy content-i.e., constant energy concentration resulted in uniform quantitative compositions of carcasses. MOURA et al. (2011b) obtained similar results for muscle depth and DE LA LLATA et al. (2001) and REZENDE et al. (2006) for back-fat thickness.

Lean meat percentage was affected (P>0.05) by net energy levels. These findings are similar to those obtained by REZENDE et al. (2006), PAIANO et al. (2008), and QUINIOU & NOBLET (2012), demonstrating the ability of pigs to adjust feed intake even in the presence of wide variability in dietary net energy concentrations, resulting in carcasses with consistently similar protein deposition patterns.

Ractopamine levels had no effect (P>0.05) on carcass characteristics. The literature reports a positive effect of ractopamine on carcass characteristics, particularly in decreasing back-fat thickness; this effect is explained by the ability of this compound to reduce fatty acid synthesis in adipose tissue and to increase protein synthesis in muscle tissue (SANCHES et al., 2010). In the present study, however, ractopamine levels had no effect on back-fat thickness, corroborating results obtained by HINSON et al. (2011).

MOURA et al. (2011a) reported that the effectiveness of ractopamine in reducing lipogenesis in porcine adipose tissue is more pronounced when diets have higher energy content, particularly in the form of lipids. Nonetheless, this response was not observed in the present study-even with the increased net energy levels provided by lipid supplementation, back-fat thickness was unaffected, possibly because net energy consumption remained constant.

CONCLUSION

A dietary net energy level of 2,800Kcal [kg.sup.-1] is proposed for pigs weighing 70-100kg, improving feed conversion without affecting carcass characteristics, regardless of dietary ractopamine levels. Ractopamine levels above 5ppm did not affect performance or modified the quantitative characteristics of carcasses, regardless of dietary net energy levels.

http://dx.doi.org/10.1590/0103-8478cr20151115

BIOETHICS AND BIOSSECURITY COMMITTEE APPROVAL

The investigation complied with ethical standards and was approved by the Ethics Committee on Animal Use (permit 429/2012) of the Universidade Federal de Mato Grosso do Sul (UFMS).

ACKNOWLEDGEMENTS

The authors thanks Coordenacao de Aperfeijoamento de Pessoal de Nivel Superior (CAPES) for post-doctoral fellowship the first author.

REFERENCES

ALMEIDA, V.V. et al. Ractopamine, chromium-methionine and their combinations as metabolism modifier feed additives of growing and finishing pigs. Revista Brasileira de Zootecnia, v.39, p.1969-1977, 2010. Available from: <http://www.scielo. br/pdf/rbz/v39n9/a15v39n9.pdf>. Accessed: Nov. 20, 2013. doi:

10.1590/S1516-35982010000900015.

APPLE, J.K. et al. Effects of dietary lysine and energy density on performance and carcass characteristics of finishing pigs fed ractopamine. Journal of Animal Science, v. 82, p.3277-3287, 2004. Available from: <https://www.animalsciencepublications. org/publications/jas/pdfs/82/11/0823277>. Accessed: Jan. 28, 2014. doi: 2004.82113277x.

BRIDI, A.M.; SILVA, C.A. Metodos de avaliafao da carcafa e da carne suina. Londrina: Midiograf, 2007. 97p.

CORASSA, A. et al. Ractopamine and phytase in diets for finishing pigs. Revista Brasileira de Zootecnia, v.38, p.2174-2181, 2009. Available from: <http://www.scielo.br/pdf/rbz/ v38n11/a15v3811.pdf>. Accessed: Nov. 20, 2013. doi: 10.1590/ S1516-35982009001100015.

DE LA LLATA, M. et al. Effects of dietary fat on growth performance and carcass characteristics of growing-finishing pigs reared in a commercial environment. Journal of Animal Science, v.79, p.2643-2650, 2001. Available from: <http:// www.journalofanimalscience.org/content/79/10/2643.full. pdf+html?sid=f1075de6-f71b-4090-9c3e-564b87624481>. Accessed: Nov. 20, 2013.

HINSON, R.B. et al. Impact of dietary energy level and ractopamine on growth performance, carcass characteristics, and meat quality of finishing pigs. Journal of Animal Science, v.89, p.3572-3579, 2011. Available from: <https://www.animalsciencepublications. org/publications/jas/pdfs/89/11/3572>. Accessed: Jan. 26, 2014. doi: 10.2527/jas.2010-3302.

KIL, D.Y. et al. Net energy of soybean oil and choice white grease in diets fed to growing and finishing pigs. Journal of Animal Science, v.89, p.448-459, 2011. Available from: <http://www. journalofanimalscience.org/content/89/2/448.long>. Accessed: Nov. 20, 2013. doi: 10.2527/jas.2010-3233.

MOURA, M.S. et al. Net energy and ractopamine to finishing gilts under high temperature environment. Ciencia Rural, v.41, p.888-894, 2011a. Available from: <http://www.scielo.br/pdf/cr/v41n5/ a964cr4196.pdf>. Accessed: Nov. 20, 2013. doi: 10.1590/S010384782011000500025.

MOURA, M.S. et al. Net energy and ractopamine levels for finishing gilts under thermal comfort. Revista Brasileira de Zootecnia, v.40, p.1968-1974, 2011b. Available from: <http:// www.scielo.br/pdf/rbz/v40n9/a18v40n9.pdf>. Accessed: Nov. 20, 2013. doi: 10.1590/S1516-35982011000900018.

PAIANO, D. et al. Digestible threonine: lysine ratios and net energy levels in growing/finishing pigs. Revista Brasileira de Zootecnia, v.37, p.2147-2156, 2008. Available from: <http://www. scielo.br/pdf/rbz/v37n12/11.pdf>. Accessed: Nov. 08, 2013. doi: 10.1590/S1516-35982008001200011.

QUINIOU, N.; NOBLET, J. Effect of the dietary net energy concentration on feed intake and performance of growing-finishing pigs housed individually. Journal of Animal Science, v.90, p.4362-4372, 2012. Available from: <http://www.journalofanimalscience. org/content/90/12/4362.full.pdf+html>. Accessed: Nov. 08, 2013. doi: 10.2527/jas.2011-4004.

REZENDE, W.O. et al. Metabolizable energy levels maintaining digestible lysine: calorie ratio in diets for finishing barrows. Revista Brasileira de Zootecnia, v.35, p.1101-1106, 2006. Available from: <http://www.scielo.br/pdf/rbz/v35n3s0/30723.pdf>. Accessed: Nov. 08, 2013. doi: 10.1590/S1516-35982006000400022.

ROSTAGNO, H.S. et al. Tabelas brasileiras para aves e suinos: composicao de alimentos e exigencias nutricionais. 3.ed. Vijosa: UFV, 2011. 252p.

SANCHES, J.F. et al. Ractopamine levels for finishing barrows maintained in heat stress. Revista Brasileira de Zootecnia, v.39, p.1523-1529, 2010. Available from: <http://www.scielo.br/pdf/ rbz/v39n7/a19v39n7.pdf>. Accessed: Oct. 10, 2013. doi: 10.1590/ S1516-35982010000700019.

YI, X.W. et al. Influence of dietary net energy content on performance of growing pigs fed low crude protein diets supplemented with crystalline amino acids. Journal of Swine Health and Production, v. 18, p.294-300, 2010. Available from: <http://www.aasv.org/shap/ issues/v18n6/v18n6p294.pdf>. Accessed: Nov. 08, 2013.

Liliane Maria Piano Goncalves (I) Charles Kiefer (I) * Karina Marcia Ribeiro de Souza (I) Danilo Alves Marcal (I) Rodrigo Caetano de Abreu (I) Viviane Maria Oliveira dos Santos Nieto (I) Gabriela Puhl Rodrigues (I) Stephan Alexander da Silva Alencar (I)

(I) Programa de Pos-graduacao em Ciencia Animal, Universidade Federal de Mato Grosso do Sul (UFMS), 97070-900, Campo Grande, MS, Brasil. E-mail: charles.kiefer@ufms.br. * Corresponding author.

Received 08.04.15 Approved 01.18.16 Returned by the author 04.12.16 CR-2015-1115.R1
Table 1--Composition of experimental diets.

Net energy (Kcal [kg.sup.-1] of diet)

Ingredients                      2,300   2,425   2,550   2,675   2,800
Corn                             70.15   70.15   70.15   70.15   70.15
Soybean meal (45%)               20.44   20.44   20.44   20.44   20.44
Soybean oil                      0.000   1.697   3.394   5.091   6.800
Inert matter (kaolin)            6.800   5.103   3.406   1.709   0.000
Dicalcium phosphate              0.832   0.832   0.832   0.832   0.832
Calcitic limestone               0.445   0.445   0.445   0.445   0.445
Vitamin and mineral              0.100   0.100   0.100   0.100   0.100
  supplement (1)
Salt                             0.305   0.305   0.305   0.305   0.305
L-lysine HCl                     0.451   0.451   0.451   0.451   0.451
DL-methionine                    0.159   0.159   0.159   0.159   0.159
L-threonine                      0.177   0.177   0.177   0.177   0.177
L-tryptophan                     0.037   0.037   0.037   0.037   0.037
Ractopamine or                   0.100   0.100   0.100   0.100   0.100
  inert matter (2)

Calculated nutritional values

Net energy (Kcal [kg.sup.-1])    2,300   2,425   2,550   2,675   2,800
Metabolizable energy             3,045   3,186   3,327   3,468   3,608
  (Kcal [kg.sup.-1])
Gross protein (%)                16.00   16.00   16.00   16.00   16.00
Digestible lysine (%)            1.000   1.000   1.000   1.000   1.000
Digestible methionine +          0.617   0.617   0.617   0.617   0.617
  cystine (%)
Digestible threonine (%)         0.667   0.667   0.667   0.667   0.667
Digestible tryptophan (%)        0.187   0.187   0.187   0.187   0.187
Calcium (%)                      0.484   0.484   0.484   0.484   0.484
Available phosphorus (%)         0.248   0.248   0.248   0.248   0.248
Sodium (%)                       0.160   0.160   0.160   0.160   0.160

(1) Content per kilogram of diet: vit. A, 1 250
000IU; vit. [subset or equal to]3, 250 000IU; vit. E, 6250IU; vit.
[K.sub.3], 750mg; vit. Bi, 375mg; vit. [B.sub.2],
1000mg; vit. [B.sub.6], 375mg; vit. [B.sub.12],
4500 [micro]g; niacin, 4500mg; pantothenic acid,
2300mg; folic acid, 125mg; iron, 25g; copper,
3750mg; manganese, 12.5g; zinc, 31.25g; iodine,
250mg; selenium, 75mg; excipient q.s.p. 1000g. (2)
Ractopamine hydrochloride instead of kaolin.

Table 2--Performance of finishing barrows fed diets
supplemented with ractopamine.

Var          Rac (ppm)   NE (Kcal [kg.sup.-1])

                         2.300   2.425   2.550   2.675   2.800

FW (kg)      5           95.42   94.46   94.68   95.25   95.61
             10          99.73   98.90   98.43   97.86   96.87
             20          96.28   99.54   94.84   96.89   95.25
             Mean        97.14   97.63   96.07   96.67   95.91
DFI (kg)     5           2.34    2.27    2.21    2.09    2.06
             10          2.46    2.30    2.34    2.33    1.98
             20          2.36    2.45    2.11    2.14    1.99
             Mean        2.38    2.34    2.22    2.19    2.01
NEI (kcal)   5           5376    5519    5616    5598    5777
             10          5653    5564    5976    6245    5537
             20          5417    5937    5373    5729    5558
             Mean        5482    5673    5658    5857    5624
DWG (kg)     5           0.81    0.8     0.79    0.84    0.83
             10          0.93    0.92    0.9     0.89    0.86
             20          0.86    0.97    0.81    0.88    0.83
             Mean        0.87    0.89    0.84    0.87    0.84
FC           5           2.94    2.91    2.82    2.49    2.49
             10          2.65    2.5     2.61    2.72    2.29
             20          2.77    2.55    2.62    2.45    2.42
             Mean        2.79    2.65    2.68    2.55    2.4

Var          Rac (ppm)   Mean    P-value                   CV (%)

                                 NE        Rac     Int.

FW (kg)      5           95.10
             10          98.36
             20          96.56
             Mean        --      0.830     0.206   0.926   4.73
DFI (kg)     5           2.19
             10          2.28
             20          2.21
             Mean        --      0.013 *   0.558   0.878   13.72
NEI (kcal)   5           5576
             10          5795
             20          5603
             Mean        --      0.780     0.565   0.873   13.86
DWG (kg)     5           0.82
             10          0.90
             20          0.87
             Mean        --      0.843     0.125   0.945   17.67
FC           5           2.73
             10          2.55

             20          2.56
             Mean        --      0.013 *   0.147   0.875   13.73

Var: variable; Rac: ractopamine (ppm); NE: net energy; CV:
coefficient of variation; FW: finishing weight; DFI: daily
feed intake; NEI: net energy intake; DWG: daily weight gain;
FC: feed conversion; * LE: linear effect (P<0.05); DFI =
4.02127-0.00072x; FC = 4.44195-0.00069707x.

Table 3--Carcass characteristics of finishing barrows fed
diets supplemented with ractopamine.

Var        Rac (ppm)   NE (Kcal [kg.sup.-1])

                       2.300   2.425   2.550   2.675   2.800

HCW (kg)   5           70.42   70.60   69.70   70.42   71.08
           10          74.30   72.56   73.64   72.34   72.70
           20          70.02   71.20   69.60   71.18   69.68
           Mean        71.58   71.45   70.98   71.31   71.15
MD (mm)    5           76.60   74.86   73.36   78.67   70.99
           10          75.78   70.84   69.77   75.13   70.17
           20          77.31   71.09   77.05   72.57   73.43
           Mean        76.56   72.26   73.39   75.46   71.53
BFT (mm)   5           12.98   11.46   11.67   14.02   12.95
           10          11.00   12.87   13.61   13.61   12.75
           20          13.32   12.44   14.32   10.47   11.35
           Mean        12.43   12.26   13.20   12.70   12.35
LMP (%)    5           60.13   60.84   60.57   59.74   59.59
           10          61.20   59.62   59.09   59.62   59.62
           20          60.01   59.89   59.4    61.18   60.76
           Mean        60.45   60.12   59.68   60.18   59.99

Var        Rac (ppm)   Mean    P-value                 CV (%)

                               NE      Rac     Int.

HCW (kg)   5           70.44
           10          73.25
           20          70.34
           Mean        --      0.997   0.062   0.995   6.49
MD (mm)    5           74.90
           10          72.34
           20          74.29
           Mean        --      0.210   0.348   0.757   9.18
BFT (mm)   5           12.62
           10          12.77
           20          12.38
           Mean        --      0.900   0.900   0.341   24.16
LMP (%)    5           60.17
           10          59.83
           20          60.25
           Mean        --      0.861   0.706   0.556   3.16

Var: variable; Rac: ractopamine; NE: net energy; CV: coefficient
of variation; HCW: hot carcass weight; MD: muscle depth; BFT:
backfat thickness; LMP: lean meat percentage.
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Title Annotation:produccion animal; texto en ingles
Author:Goncalves, Liliane Maria Piano; Kiefer, Charles; de Souza, Karina Marcia Ribeiro; Marcal, Danilo Alv
Publication:Ciencia Rural
Date:Jul 1, 2016
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