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.
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.
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.
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).
The authors thanks Coordenacao de Aperfeijoamento de Pessoal de Nivel Superior (CAPES) for post-doctoral fellowship the first author.
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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: firstname.lastname@example.org. * 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|
|Date:||Jul 1, 2016|
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