понедельник, 24 сентября 2012 г.

Net energy system may have benefits for performance.(Nutrition And Health/Swine) - Feedstuffs

Net energy provides the closest estimate of the true energy available for maintenance and production. The nutritional and economic ranking of feedstuffs depends on the energy system. For practical purposes, the superiority of the net energy System (in comparison with the digestible or metabolizable systems) for predicting performance and carcass quality can be demonstrated.

The effect of reducing the protein level in diets for growing pigs has been investigated in a number of experiments, showing no detrimental effect on performance and nitrogen retention--but markedly reduced nitrogen excretion--when sufficient amounts of the essential amino acids are supplied to this type of diet (Bourdon et al., 1995; Canh et al., 1998). However, there is a trend for fatter carcasses when pigs are fed low protein diets supplemented with amino acids (Kerr et al., 1995; Tuitoek et al., 1997; Raj et al., 2000).

Lowering the dietary crude protein (CP) level is accompanied by a more efficient utilization of energy, due to a significant reduction in heat production and energy lost in urine. This results in a greater quantity of retained energy with low protein diets at identical digestible (DE) or metabolizable energy (ME) intake. The net energy (NE) system is able to take this effect into account. The superiority of the NE system for predicting performance and carcass quality has been confirmed especially when reduced protein diets are fed (Dourmad et al., 1993; Le Bellego et al., 2000 and 2001).

The following article will discuss the applicability of the NE system in comparison to the DE and ME system. Special emphasis is placed on the effects of energy system on performance, carcass quality, nitrogen excretion as well as least-cost diet formulation.

Comparison of energy systems

In theory, a reduced protein, amino acid-supplemented diet should be nutritionally superior to an all-intact protein diet. By feeding low-protein, amino acid-supplemented diets with less excess of amino acids, fewer amino acids are deaminated, converted to urea and excreted in the urine. As a result, less energy is needed for these energy requiting metabolic processes. However the savings in energy as a result of not having to deaminate excess amino acids is, in some cases, simply deposited as body fat in pigs fed low-protein diets. The reason for the increase in carcass back fat is likely due to a higher NE content of the low-protein, amino acid-supplemented diet.

Although the ME content in corn and soybean meal is the same (3,650 kcal/kg; Table 1), the NE content in corn is considerably higher (2,970 versus 1,930 kcal/kg; Table 1). Therefore in the case of a corn-soybean meal diet a reduction of 2 percentage units in dietary protein results in an increase in dietary NE content by about 2%.

The data in Table 1 shows that the efficiency of utilization of DE or ME for NE is not constant. Therefore, the hierarchy among feedstuffs is different in the DE, ME or NE system. Comparing some typical feedstuffs clearly illustrates that both the DE and ME system in general overestimate the energy value of high-protein and high-fiber feedstuffs, whereas feedstuffs high in starch or fat are underestimated.

NE values are defined as ME minus heat increment associated with metabolic utilization of ME and the energy cost of ingestion and digestion of the feed (Noblet, 1996). NE values provide the closest estimate of the 'true' energy available for maintenance and production purposes.

Energy utilization, performance

The increase in fat deposition in pigs fed low-protein, amino acid-supplemented diets can be prevented by maintaining the same ratio of digestible amino acids to NE as in the intact protein diet (Dourmad et al., 1993; Le Bellego et al., 2000 and 2001).

In a performance trial (Canh et al., 1998), the effect of three levels of dietary protein (16.5, 14.5 and 12.5%) on performance and carcass characteristics of growing-finishing pigs (52 to 104 kg bodyweight) were examined. All diets were formulated to contain 0.76 g digestible lysine/MJ NE. The level of dietary CP did not influence feed intake, daily gain, .feed conversion and carcass characteristics (Table 2, p. 13).

With the reduction in dietary CP level--at similar DE or ME intakes--Le Bellego et al. (2001) observed a significant reduction in heat production and urinary energy loss (Table 3).

The significantly lower heat production was due to a reduction of the thermic effect of feed, which is reduced when the dietary protein level is lowered, and corresponded to 18.7 ,and 15.2% of ME intake for the high- and low-CP diets, respectively. Due to the reduction of urinary energy losses and heat production, the efficiencies of DE and ME for NE are improved when dietary CP level is reduced (Table 4). The NE system is able to take this effect into account.

For each 1 g decrease in protein intake (and its replacement by starch), urinary energy and heat loss are reduced 3.5 and 7.0 kJ, respectively (Le Bellego et al., 2001).

Le Bellego et al. (2000) conducted a study to determine the effect of low-protein diets with or without fat addition on growth performance and body composition of growing-finishing pigs in thermoneutral (22[degrees]C) or high (29[degrees]C) ambient temperature.

Daily weight gain, lean meat and fat tissue (Table 4) were not affected by treatment. Feed conversion was significantly affected by diet with best feed conversion observed for the low CP + fat diet.

The effect of heat stress on performance of pigs is shown in Table 5. Feed intake was significantly reduced 15% by increasing the ambient temperature from 22 to 29[degrees]C. Weight gain was not affected by diet but by temperature with a significant reduction of 13% at high ambient temperature. Feed conversion was not affected by temperature but by diet with a significant advantage for the low CP and low CP + fat diets. The increase of ambient temperature also resulted in a reduction in fat tissue (-8%).

Pigs under heat stress showed a significant reduction in feed intake and daily gain. However, the depression in feed intake (Figure 1) and weight gain (Figure 2) tended to be higher for the high CP diet-than for the low CP or low CP + fat diet.

[FIGURES 1-2 OMITTED]

This effect holds especially true for the finishing phase (64-100 kg bodyweight), showing a clear advantage of feeding low-protein diets under heat stress conditions.

Practical diet formulation

For least-cost formulation purposes, it is important to predict the energy values of the different feed ingredients. Today, it is well accepted that NE is the closest estimate of the true energy value of ingredients. Since the NE value of feedstuffs and diets cannot be measured routinely, regression equations can be used for predicting the dietary NE content from DE or ME and chemical characteristics (Table 6). The NE value of free amino acids is 75% of their gross energy content (Noblet et al., 1994).

It is important to express the energy requirement of the animal on the same basis as the energy value of the feed. In order to transfer energy requirements expressed on a DE or ME basis to NE requirements, one should simply multiply the present DE or ME specification by 0.71 or 0.74, respectively (Noblet et al., 1994).

Results of least-cost formulation will depend on the energy system. For instance, diets formulated based on the NE concept generally have a lower CP content and subsequent higher supplementation of amino acids, while dietary costs can be reduced.

The potential effect of the energy system on least-cost formulation is shown in Table 7. In this example, corn-soybean meal diets were formulated based on ME or NE for the growing (25-40 kg bodyweight) and finishing (70-105 kg bodyweight) phases, respectively.

Within each phase, diets were formulated on ME basis and standardized digestible amino acids. In the growing phase, diet 1 was formulated to contain 13.5 MJ/kg ME, which resulted in dietary NE and CP contents of 9.88 MJ/ kg and 18.7%, respectively.

Formulating diet 2 with the same ingredients to a NE content of 9.88 MJ/ kg as well as equal levels of amino acids compared with diet 1 resulted in a slight reduction in dietary CP content. The actual diet composition moved to a lower level of soybean meal with elevated inclusion levels of corn and amino acids.

The same principles were applied and observations were made for the finishing phase (diet 3 versus diet 4).

The economic benefit of formulating diets based on NE versus ME can also be deducted from Table 7. Feed costs are reduced about 2% in both phases when diets are formulated on NE basis.

Conclusions

NE provides the closest estimate of the true energy available for maintenance and production. The nutritional and economic ranking of feedstuffs depends on the energy system; therefore, the result of least-cost formulation depends on the energy system as well. DE and ME systems systematically overestimate the energy content of protein-or fiber-rich feeds and underestimate the energy value of starch- or fat-rich feeds.

For practical purposes, the superiority of the NE system (in comparison with the DE or ME system) for predicting performance and carcass quality--especially when reduced-protein diets are fed--can be demonstrated. Diets formulated according to the NE concept are characterized by a lower CP content, a higher supplementation of amino acids and reduced dietary costs.

 TABLES  1. Energy values (kcal/kg) of some ingredients in DE, ME and NE system (Noblet et al., 1994)  Ingredients    DE     ME     NE    ME:DE  NE:ME  Corn          3,780  3,650  2,970  0.97   0.81 Wheat         3,870  3,780  2,900  0.98   0.77 Tapioca       3,790  3,720  3,080  0.98   0.83 Peas          3,880  3,750  2,640  0.97   0.70 Soybean meal  3,910  3,650  1,930  0.93   0.53  2. Effect of reducing dietary protein on performance and carcass characteristics of pigs (52-104 kg bodyweight; Canh et al., 1998)                                High     Medium     Low      Diet Dietary CP (%)               (16.5)    (14.5)    (12.5)   effect  Weight gain, g per day        805       805       797       NS Feed intake, g per day      2,249     2,245     2,257       NS Feed:gain ratio                 2.75      2.75      2.79    NS Back fat thickness, mm         15.2      15.4      15.9     NS Lean meat, %                   57.2      57.1      56.7     NS Muscle thickness, mm           56.9      56.5      57.0     NS Digestible lysine, g/MJ NE         0.76 for all treatments  TABLES  3. Effect of dietary CP level on energy balance and utilization in growing pigs (50-70 kg bodyweight; Le Bellego et al., 2001)  CP (%)                            18.9        16.7        14.6  Energy intake (2)  DE intake                         2.74        2.75        2.76  ME intake                         2.61        2.65        2.67  Urinary energy, % DE intake       3.80 (a)    3.32 (a)    2.87 (c)  Heat production, % ME intake     56.7 (a)    55.2 (ab)   53.2 (bc)  Thermic effect of feed,   % ME intake                     18.7        16.9        16.9 Energy utilization  NE/DE, %                         69.6 (a)    72.1 (b)    73.2 (bc)  NE/ME, %                         72.8 (a)    74.9 (ab)   75.8 (b)  N[E.sub.measured]/   N[E.sub.calculated] (3), %      97.9       100.0       100.3  CP (%)                             12.3          Diet effect (1)  Energy intake (2)  DE intake                          2.67               NS  ME intake                          2.60               NS  Urinary energy, % DE intake        2.27 (d)           **  Heat production, % ME intake      52.8 (c)            **  Thermic effect of feed,   % ME intake                      15.2                NS Energy utilization  NE/DE, %                          74.5 (c)            **  NE/ME, %                          76.6 (b)            **  N[E.sub.measured]/   N[E.sub.calculated] (3), %      101.0                NS  (1) Statistical significance: analysis of variance with diet as main effect. Statistical significance: NS: P > 0.05; **: P < 0.01. Different superscripts indicate significantly different means (P < 0.05).  (2) MJ per day per kilogram [bodyweight.sup.0.60].  (3) Calculated according to Noblet et al. (1994).  4. Effect of low heat increment diets on feed intake, performance and body composition of pigs (27-100 kg bodyweight; Le Bellego et al., 2000)  Temperature                       22[degrees]C Diet CP level (%)         High,        Low,          Low, (27-64 kg BW/             19.7/        15.3/        + fat, 64-100 kg BW)             17.5         12.5       16.4/13.3  Feed intake  g per day              2,752 (a)    2,575 (b)     2,544 (b)  MJ NE per day          28.14 (a)    27.02 (a)     28.26 (a) Performance  ADG, g per day         1,098 (a)    1,057 (a)     1,078 (a)  Feed conv. ratio        2.52 (a)     2.44 (ab)     2.36 (bc) Body composition at slaughter  Lean meat,   % of carcass           58.7 (a)     59.7 (ac)     59.7 (ac)  Fat tissues,   % of carcass           25.7 (a)     24.1 (ac)     24.5 (ac)  Temperature                       29[degrees]C Diet CP level (%)         High,        Low,           Low, (27-64 kg BW/             19.7/        15.3/         + fat, 64-100 kg BW)             17.5         12.5        16.4/13.3  Feed intake  g per day              2,265 (c)    2,243 (c)     2,202 (c)  MJ NE per day          23.16 (c)    23.55 (bc)    24.45 (b) Performance  ADG, g per day           930 (b)      917 (b)       955 (b)  Feed conv. ratio        2.46 (ab)    2.45 (ab)     2.30 (c) Body composition at slaughter  Lean meat,   % of carcass           61.4 (b)     60.6 (bc)     60.3 (bc)  Fat tissues,   % of carcass           22.0 (b)     23.1 (bc)     23.3 (bc)  Temperature Diet CP level (%)               Statistics (1) (27-64 kg BW/                                   Diet x 64-100 kg BW)           Diet         Temp.       Temp.  Feed intake  g per day               **           **          NS  MJ NE per day           **           **          NS Performance  ADG, g per day          NS           **          NS  Feed conv. ratio        **           NS          NS Body composition at slaughter  Lean meat,   % of carcass           NS           **           *  Fat tissues,   % of carcass           NS           **          NS  Diets based on wheat, corn and soybean meal, with 0.85 g standardized ileal digestible lysine per MJ NE.  (1) Statistical significance: analysis of variance with diet as the main effect. Statistical significance: NS: P > 0.05; *: P < 0.05; **: P < 0.01. Different superscripts indicate statistically different means (P < 0.05).  5. Effect of heat stress on performance of pigs (27-100 kg bodyweight; Le Bellego et al., 2000)  Temperature                   22[degrees]C   29[degrees]C  Feed intake, g per day        2,624 (1)      2,237 Daily bodyweight gain, g      1,078 (1)        934 Feed conversion                   2.44           2.40 Lean meat, % carcass             59.4 (1)       60.8 Fat tissues, % carcass           24.8 (1)       22.8                                29 vs. 22[degrees]C, Temperature                      % difference  Feed intake, g per day              -15 Daily bodyweight gain, g            -13 Feed conversion                      +2 Lean meat, % carcass                 +2 Fat tissues, % carcass               -8  (1) P < 0.01.  6. Prediction of NE content (kcal/kg DM) of diets from DE or ME content (kcal/kg DM) and/or chemical characteristics (g/kg DM; Noblet et al., 1994) (1)  Number                         Equation [R.sup.2]  1    NE = 0.703 x DE  + 1.58 x EE + 0.47 x        ST - 0.97 x CP - 0.98 x CF                          0.97 2    NE = 0.700 x DE  + 1.61 x EE + 0.48 x        ST - 0.91 x CP - 0.87 x ADF                         0.97 3    NE = 0.730 x ME  + 1.31 x EE + 0.37 x        ST - 0.67 x CP - 0.97 x CF                          0.97 4    NE = 0.726 x ME  + 1.33 x EE + 0.39 x        ST - 0.62 x CP - 0.83 x ADF                         0.97 5    NE = 2875 + 4.38 x EE + 0.67 x        ST - 5.50 x Ash - 2.01 x (NDF - ADF) - 4.02 x ADF   0.93  (1) EE, ST, CF, ADF, NDF for ether extract, starch, crude fiber, acid detergent fiber and neutral detergent fiber, respectively.  7. Effect of energy system on least-cost formulation                                               Growing phase                                           (25-40 kg bodyweight)  Ingredients (%)                       Diet 1 (ME)    Diet 2 (NEb)  Corn                                     60.06          66.16- Wheat middlings                          10.00           5.83 Soybean meal (48% CP)                    24.86          24.67 DL-methionine (99%)                       0.04           0.04 L-lysine hydrochloride                    0.11           0.12 L-threonine                              --             -- Soybean oil                               1.82          -- Dicalcium phosphate                       1.01           1.14 Calcium carbonate                         0.78           0.71 Sodium chloride                           0.32           0.33 Premix                                    1.00           1.00  Nutrients (%)  ME, MJ/kg (kcal/kg)                 13.50 (3,230)   13.31 (3,180) NE, MJ/kg (kcal/kg)                  9.88 (2,360)    9.88 (2,360) CP                                      18.7            18.5 Std. digestible lysine (a)               0.90            0.90 Std. digestible methionine (a)           0.31            0.31 Std. digestible methionine + cysteine (a)                0.57            0.57 Std. digestible threonine (a)            0.59            0.59 Std. digestible tryptophan (a)           0.17            0.17 Cost ($/100 kg) (c)                     13.59           13.38                                              Finishing phase                                          (70-105 kg bodyweight)  Ingredients (%)                       Diet 3 (ME)     Diet 4 (NE)  Corn                                     58.17          63.97 Wheat middlings                          20.00          19.57 Soybean meal (48% CP)                    17.30          13.06 DL-methionine (99%)                       0.01           0.03 L-lysine hydrochloride                    0.07           0.20 L-threonine                              --              0.06 Soybean oil                               1.40          -- Dicalcium phosphate                       0.80           0.89 Calcium carbonate                         0.95           0.93 Sodium chloride                           0.31           0.31 Premix                                    1.00           1.00  Nutrients (%)  ME, MJ/kg (kcal/kg)                  13.00 (3,100)   12.75 (3,050) NE, MJ/kg (kcal/kg)                  9.62 (2,300)    9.62 (2,300) CP                                      16.4            15.0 Std. digestible lysine (a)               0.71            0.71 Std. digestible methionine (a)           0.25            0.25 Std. digestible methionine + cysteine (a)                0.49            0.48 Std. digestible threonine (a)            0.50            0.50 Std. digestible tryptophan (a)           0.15            0.14 Cost ($/100 kg) (c)                     12.11           11.91  (a) Ratios of standardized digestible methionine + cystine, threonine and tryptoptnan to lysine were at least 62:, 65: and 19:100 or 65:, 70: and 19:100 for the growing and finishing period, respectively, with methionine:methionine + cysteine set at 55:100.  (b) Formulated to contain equal NE and standardized digestible amino acid levels as diet formulated on ME.  (c) Basis: U.S. ingredient prices, spring 2001. 

REFERENCES

Bourdon, D., J.Y. Dourmad and Y. Henry. 1995. Reduction des rejets azotes chez le porc en croissance par la raise en oeuvre de l'alimentation multiphase, associee a l'abaissement du taux azote. J. Rech. Porc. Ft. 27:269-278.

Canh, T.T., A.J.A. Aarnink, J.B. Schutte, A. Sutton, D.J. Langhout and M.W.A. Verstegen. 1998. Dietary protein affects nitrogen excretion and ammonia emission from slurry of growing-finishing pigs. Livest. Prod. Sci. 56:181-191.

Dourmad, J.Y., Y. Henry, D. Bourdon, N: Quiniou and D. Guillou. 1993. Effect of growth potential and dietary protein input on growth performance, carcass characteristics and nitrogen output in growing-finishing pigs. In: M.W.A. Verstegen, L.A. den Hartog, G.J.M. van Kempen and J.H.M. Metz (eds.). Nitrogen flow in pig production and environmental consequences. Pudoc. Wageningen, The Netherlands. p. 206-211.

Kerr, B.J., F.K. McKeith and R.A. Easter. 1995. Effect of performance and carcass characteristics of nursery to finisher pigs fed reduced crude protein, amino acid-supplemented diets. J. Anita. Sci. 73:433-440.

Le Bellego, L., J. van Milgen, M. Rademacher, S. van Cauwenberghe and J. Noblet. 2000. Utilization of low heat increment diets at high ambient temperatures in growing pigs. J. Anita. Sci. 78 (Suppl. 1):186.

Le Bellego, L., J. van Milgen, S. Dubois and J. Noblet. 2001. Energy utilization of low-protein diets in growing pigs. J. Anim. Sci. 79:1259-1271.

Noblet, J. 1996. Digestive and metabolic utilization of dietary energy in pig feeds: Comparison of energy systems. In: P.C. Garnsworthy, J. Wiseman and W. Haresign (eds.). Recent advances in animal nutrition. Nottingham University Press, Nottingham, U.K. p. 207-231.

Noblet, J., H. Fortune, X.S. Shi and S. Dubois. 1994. Prediction of net energy value of feeds for growing pigs. J. Anita. Sci. 72:344-354..

Raj, S., H. Fanrejewski, D. Weremko, G. Skiba, L. Buraczewska, T. Zebrowska and I.K. Han. 2000. Growth performance, body composition and protein and energy utilization of pigs fed ad libitum diets formulated according to digestible amino acid content. Asian-Aust. J. Anita. Sci. 13:817-823.

Tuitoek, K,, L.G. Young, C.F.M. de Lange and B.J. Kerr. 1997. The effect of reducing excess dietary amino acids on growing-finishing pig performance: An evaluation of the ideal protein concept. J. Anita. Sci. 75:1575-1583.

Dr. Meike Rademacher is senior manager for animal nutrition in the feed additives division of Degussa AG.