Development of a model to describe the compositional growth and dietary lysine requirements of pigs fed ractopamine

The objective of this research was to use recent ractopamine research data to develop an updated mathematical model to describe the daily compositional growth of pigs fed ractopamine. Mean increases of 18.2, 23.1, and 25.0% for daily protein accretion were assumed for 5, 10, and 20 ppm of ractopamine for an overall gain of 40 kg of BW gain during the feeding period. The relative effect of ractopamine described the rapid increase and subsequent decrease in the effect of ractopamine as a function of BW gain or days on test and ractopamine concentration (RC, ppm). The reduction in ME intake produced by ractopamine was described as 0.036 x (RC/20)(0.7) multiplied by the ME intake for the first 20 kg of BW gain, and then increasing to 0.078 x (RC/20)(0.7) at 40 kg of BW gain feeding period. The ratio of fat-free muscle gain to protein accretion increased by 14 to 16% with the feeding of ractopamine, depending on the dietary lysine/essential AA levels. The ratio of carcass fat gain to empty body lipid gain was increased when lysine and essential AA requirements were met. Daily protein accretion and fat-free lean growth were described as functions of dietary lysine/essential AA intakes. The percentage of lysine in protein accretion increased with the feeding of ractopamine from 6.80 to 7.15%, depending on ractopamine concentration. Equations predicting carcass measurements, such as fat and longissimus muscle depths from carcass weight and composition, were modified to incorporate prediction biases produced by ractopamine. For the four concentrations of ractopamine (0, 5, 10, and 20 ppm, respectively) during a 78 to 110 kg of BW feeding period, the model predicted performance levels for ADG (1.03, 1.15, 1.16, and 1.16 kg/d), gain:feed (kg of ADG/kg of ADFI; 0.360, 0.401, 0.412, and 0.425), dressing percentage (75.1, 76.0, 76.3, and 76.4), percentage fat-free lean (48.7, 51.0, 51.5, and 52.2), longissimus muscle area (38.8,41.8,42.5, and 43.5 cm2), 10th-rib fat depth (22.1, 19.8, 19.3, and 18.7 mm), and fat-free lean gain (321, 446, 467, and 495 g/d), comparable to recent research data. The model allows the effect of ractopamine to be added to farm specific pig growth curves. It can be used to evaluate ways to optimize the use of ractopamine, including duration of ractopamine feeding, concentration of ractopamine, and dietary lysine concentration.     

Effects of dietary lysine and energy density on performance and carcass characteristics of finishing pigs fed ractopamine

Two hundred sixteen crossbred barrows and gilts (84.3 kg BW) were used to test the effects of dietary energy density and lysine:energy ratio (Lys:ME) on the performance, carcass characteristics, and pork quality of finishing pigs fed 10 ppm ractopamine. Pigs were blocked by BW and gender, allotted to 36 pens (six pigs per pen), and pens were assigned randomly within blocks to dietary treatments (as-fed basis) arranged in a 2 x 3 factorial design, with two levels of energy (3.30 or 3.48 Mcal/kg) and three Lys:ME (1.7, 2.4, or 3.1 g lysine/Mcal) levels. Pigs were fed experimental diets for 28 d, and weights and feed disappearance were recorded weekly to calculate ADG, ADFI, and G:F. Upon completion of the feeding trial, pigs were slaughtered and carcass data were collected before fabrication. During carcass fabrication, hams were analyzed for lean composition using a ham electrical conductivity (TOBEC) unit, and loins were collected, vacuum-packaged, and boxed for pork quality data collection. Energy density had no (P > 0.22) effect on ADG or ADFI across the entire 28-d feeding trial; however, pigs fed 3.48 Mcal of ME were more (P < 0.02) efficient than pigs fed 3.30 Mcal of ME. In addition, ADG and G:F increased linearly (P < 0.01) as Lys:ME increased from 1.7 to 3.1 g/Mcal. Carcasses of pigs fed 3.48 Mcal of ME were fatter at the last lumbar vertebrae (P < 0.08) and 10th rib (P < 0.04), resulting in a lower (P < 0.03) predicted fat-free lean yield (FFLY). Conversely, 10th-rib fat thickness decreased linearly (P = 0.02), and LM depth (P < 0.01) and area (P < 0.01) increased linearly, with increasing Lys:ME. Moreover, FFLY (P < 0.01) and actual ham lean yield (P < 0.01) increased as Lys:ME increased in the diet. Dietary energy density had no (P > 0.19) effect on pork quality, and Lys:ME did not (P > 0.20) affect muscle pH, drip loss, color, and firmness scores. Marbling scores, as well as LM lipid content, decreased linearly (P < 0.01) as Lys:ME increased from 1.7 to 3.1 g/Mcal. There was a linear (P < 0.01) increase in shear force of cooked LM chops as Lys:ME increased in the finishing diet. Results indicate that 3.30 Mcal of ME/kg (as-fed basis) is sufficient for optimal performance and carcass leanness in pigs fed ractopamine. The Lys:ME for optimal performance and carcass composition seems higher than that currently used in the swine industry; however, feeding very high Lys:ME (> 3.0 g/Mcal, as-fed basis) to ractopamine-fed pigs may result in decreased marbling and cooked pork tenderness.     

Evaluation of strategies for selection for lean growth rate in pigs

Lean growth rate (LGR) in pigs is a nonlinear biological function of growth rate and lean quantity. According to animal breeding theory, genetic progress for LGR is maximized with selection on a linear index of its component traits, but selection on direct EBV for LGR is also common. In this study, the performance of five criteria for selection on estimated LGR in pigs was evaluated through simulation over five generations: linear indexes of multiple-trait EBV of component traits with or without updating index weights in each generation; a nonlinear index of multiple-trait EBV of component traits; and direct selection on EBV for LGR from a single-trait model or a multiple-trait model that included LGR and component traits. The nonlinear index yielded the highest response in LGR in Generation 5, but the linear index with updating performed almost as well. Not updating weights for the linear index reduced response in LGR by 1.1% in Generation 5 (P < 0.05). Direct selection on single-trait EBV for LGR yielded the lowest responses in Generation 5. Direct selection on EBV for LGR from a multiple-trait animal model yielded a 3.1% greater response in LGR in Generation 5 than direct selection on EBV for LGR based on a single-trait animal model (P < 0.05), but yielded a 1.9% lower response than the nonlinear index. Although differences in response in LGR were limited, alternative selection criteria resulted in substantially different responses in component traits. Linear index selection for LGR placed more emphasis on lean quantity, whereas direct selection for LGR emphasized growth rate. Based on the relative changes in the responses in LGR, selection for estimated LGR based on a nonlinear index or a linear index with updating is recommended for use in the swine industry.     

Effects of dietary energy density and lysine:calorie ratio on growth performance and carcass characteristics of growing-finishing pigs

We conducted two experiments to evaluate the effects of dietary energy density and lysine:calorie ratio on the growth performance and carcass characteristics of growing and finishing pigs. In Exp. 1, 80 crossbred barrows (initially 44.5 kg) were fed a control diet or diets containing 1.5, 3.0, 4.5, or 6.0% choice white grease (CWG). All diets contained 3.2 and 2.47 g of lysine/Mcal ME during growing (44.5 to 73 kg) and finishing (73 to 104 kg), respectively. Increasing energy density did not affect overall ADG; however, ADFI decreased and feed efficiency (Gain:feed ratio; G:F) increased (linear, P < .01). Increasing energy density decreased and then increased (quadratic, P < .06) skinned fat depth and lean percentage. In Exp. 2, 120 crossbred gilts (initially 29.2 kg) were used to determine the effects of increasing levels of CWG and lysine:calorie ratio fed during the growing phase on growth performance and subsequent finishing growth. Pigs were fed increasing energy density (3.31, 3.44, or 3.57 Mcal ME/kg) and lysine:calorie ratio (2.75, 3.10, 3.45, or 3.80 g lysine/Mcal ME). No energy density x lysine:calorie ratio interactions were observed (P > .10). Increasing energy density increased ADG and G:F and decreased ADFI of pigs from 29.5 to 72.6 kg (linear, P < .05). Increasing lysine:calorie ratio increased ADG and ADFI (linear, P < .01 and .07, respectively) but had no effect on G:F. From 72.6 to 90.7 kg, all pigs were fed the same diet containing .90% lysine and 2.72 g lysine/Mcal ME. Pigs previously fed with increasing lysine:calorie ratio had decreased (linear, P < .02) ADG and G:F. Also, pigs previously fed increasing CWG had decreased (linear, P < .03) ADG and ADFI. From 90.7 to 107 kg when all pigs were fed a diet containing .70% lysine and 2.1 g lysine/Mcal ME, growth performance was not affected by previous dietary treatment. Carcass characteristics were not affected by CWG or lysine:calorie ratio fed from 29.5 to 72.6 kg. Increasing the dietary energy density and lysine:calorie ratio improved ADG and G:F of growing pigs; however, pigs fed a low-energy diet or a low lysine:calorie ratio from 29 to 72 kg had compensatory growth from 72 to 90 kg.     

日粮消化能与可消化赖氨酸水平对断奶仔猪生产性能的影响

本文旨在研究日粮不同消化能与可消化赖氨酸水平对断奶仔猪生产性能的影响.采用2×3因子设计,以消化能(3500 kcal/kg 与3400 kcal/kg)与可消化赖氨酸水平(1.10%、1.25%和1.40%)为两个主效应.选用288头23日龄断奶健康的杜X长X大三元杂交仔猪[初始体重(6.64±0.39)kg],公母各半,随机分为6个处理,每个处理6个重复,每个重复8头猪,试验期14 d.结果表明:在本试验条件下,与低消化能水平相比,高消化能组显著提高了仔猪日增重(4.6%)和饲料转化率(8.9%)(P＜0.01),降低了日采食量(5%)(P＜0.01).日粮消化能水平对腹泻率无显著影响(P＞0.05).随着日粮赖氨酸水平的提高.断奶仔猪日增重也相应提高(P=0.04).高赖氨酸比低赖氨酸组日增重提高12.4%,饲料转化率也提高5.3%(P＜0.01).日粮赖氨酸水平对日采食量和腹泻率影响并不显著.消化能与赖氨酸互作对试验猪日增重、日采食量、饲料转化率及腹泻率交互作用不明显.综合考虑,日粮消化能水平为3500 kcal/kg,可消化赖氨酸水平为1.25%时,断奶仔猪发挥最大的生长性能,日增重最大,饲料转化率最佳.     

Effect of dietary energy concentration and apparent ileal digestible lysine:metabolizable energy ratio on nitrogen balance and growth performance of young pigs

Two experiments were conducted to determine the optimal apparent ileal digestible lysine:ME (Lys:ME) ratio and the effects of lysine and ME levels on N balance (Exp. 1) and growth performance (Exp. 2) in growing pigs. Diets were designed to contain Lys:ME ratios of 0.6, 0.7, 0.8, and 0.9 g/MJ at 13.5 and 14.5 MJ of ME/kg of diet in a 4 x 2 factorial arrangement. In Exp. 1, conventional N balances were determined on 48 crossbred barrows (synthetic line 990, initial BW = 13.1 +/- 0.7 kg) at approximately 15, 20, and 25 kg of BW with six pigs per diet. At 15 kg of BW, an energy density x Lys:ME ratio interaction on daily N retention was observed (P < 0.05). At each BW, N retention improved with an increase in N intake associated with increasing ME concentration. In 15-kg BW pigs, increasing the Lys:ME ratio increased daily N retention at the 13.5 (linear, P < 0.001) and 14.5 MJ of ME level (linear, P < 0.01; quadratic, P < 0.05). In 20-kg BW pigs, N retention (g/d) increased (linear, P < 0.001; quadratic, P < 0.01) and N retention (percentage) increased (linear, P < 0.001) as the Lys:ME ratio increased. At 25 kg of BW, N retention (g/d) increased quadratically (P < 0.05) with an increase in Lys:ME ratio. The Lys:ME ratios that maximized daily N retention at 15 kg of BW were 0.88 and 0.85 g/MJ at the 13.5 and 14.5 MJ of ME levels, respectively and 0.81 and 0.77 g/MJ (for both ME levels) at 20 and 25 kg of BW, respectively. Over the 28-d trial, an energy density x Lys:ME ratio interaction on ADG was observed (P < 0.05). Increasing energy density increased growth performance, whereas increasing the Lys:ME ratio in high-energy diets increased ADG (linear, P < 0.05; quadratic, P < 0.01) and gain:feed ratio (G/F) quadratically (P < 0.01). Average daily gain and G/F ratio were greatest in pigs fed the 14.5 MJ of ME diet and the Lys:ME ratio of 0.82 g/MJ. In Exp. 2, 128 individually housed crossbred barrows and gilts (initial BW = 12.8 +/- 1.6 kg) were used to determine the effect of diets used in Exp. 1 on growth performance in a 4 x 2 x 2 factorial arrangement. The ME level increased ADG and G/F from d 0 to 14 and from d 0 to 28. Increasing the Lys:ME ratio increased ADG from d 0 to 14, whereas growth performance was maximized in pigs fed Lys:ME ratio of 0.82 g/MJ. These results suggest that pigs from 13 to 20 and from 20 to 30 kg of BW fed diets containing 14.5 MJ of ME/kg had maximum N retention and ADG at 0.85 and 0.77 g of apparent ileal digestible lysine/MJ of ME, respectively.     

The effect of energy intake, genotype, and body weight on protein retention in pigs when dietary lysine is the first-limiting factor

This study tested the hypothesis that the effect of lysine intake, if first-limiting, on protein retention in growing pigs is completely independent of the effects of energy intake, differences in the protein retention capacity among genotypes and gender, and body weight. Protein retention, using the nitrogen balance technique, was measured in 12 castrated male German Landrace and Pietrain pigs at 44 and 77 kg of BW and at two energy intake levels (1.1 and 1.3 MJ ME/kg BW.75). All animals received a constant amount of a basal diet that provided a protein intake of 220 g/d and a total lysine intake of 13 g/d. Appropriate amounts of cornstarch were offered additionally to reach the intended energy intake levels. The results show that neither energy intake nor breed had any effect on the level of protein retention, whereas, at 77 kg BW, protein retention was significantly lower than at 44 kg (117.8 and 123.5 g/d, respectively), which can be attributed to the higher requirement for maintenance. The results of this experiment and the linearity of the relationship between protein retention and lysine intake as shown by several authors simplify both the prediction of protein retention from lysine intake and the calculation of the lysine requirement for a particular protein retention. However, to ensure accuracy of these predictions, it is essential to know when ratios of lysine to other amino acids and to energy and capacity for protein retention in the animal become first-limiting.     

Effect of apparent ileal digestible lysine to energy ratio on performance of finishing pigs at different dietary metabolizable energy levels

A study with a total of 96 crossbred barrows and gilts fed ad libitum in a body weight range of 56-110 kg was carried out in order to investigate whether the optimum ratio of apparent ileal digestible lysine : energy (ME) depends on the energy density of the diet. Dietary treatments were ratios of 0.34, 0.42, 0.50 and 0.58 g digestible lysine/MJ ME either at an energy density of 13 or 14 MJ ME. Body weight gain as well as feed and ME conversion rate were improved when lysine : ME ratio increased from 0.34 to 0.50, whereby all parameters showed a significant ratio x sex interaction. Feed intake and feed conversion rate were higher at a dietary energy density of 13 MJ ME than at an energy density of 14 MJ ME but energy density did not influence daily growth rate, ME intake and ME conversion rate. Fat area above eye muscle and meat : fat ratio were lower and eye muscle area and lean percentage were higher at a ratio of 0.42 compared with a ratio of 0.34. Daily feed intake, body weight gain, feed conversion rate and parameters of fatness were higher in barrows than in gilts. Conversely, gilts had higher eye muscle area and lean percentage. Optimum ratio for body weight gain, feed and ME conversion rate calculated by exponential regression analysis were 0.42-0.43 in barrows. In gilts, feed and ME conversion rate were optimized at a ratio of 0.53 and 0.54. Because growth showed a linear response to increasing digestible lysine : ME ratios, optimum ratio for daily gain in gilts is considered to be at least 0.58.     

Influence of the dietary ratio between sulphur containing amino acids and lysine on performance of growing-finishing pigs fed diets with various lysine concentrations.

This study was conducted to determine the optimal ratio between sulphur containing amino acids and lysine in diets for growing-finishing pigs. Therefore, a total of five trials was carried out in which growing-finishing pigs (live weight range between 53 and 105 kg) were fed diets with various concentrations of lysine (0.62, 0.70 and 0.78%) and various ratios between sulphur containing amino acids to lysine. The diets contained 12.9 MJ ME per kg and 13.5% CP; the ratio between sulphur containing amino acids to lysine was adjusted by individual supplementation of the diets with DL-methionine. Increasing dietary levels of lysine from 0.62 to 0.78% continuously increased daily body weight gains and improved feed conversion efficiency as well as carcass characteristics. There was no significant interaction between the dietary lysine supply and the ratio between sulphur containing amino acids to lysine on animal performance parameters. This means that the effect of the ratio of sulphur containing amino acids to lysine was similar for various dietary lysine concentrations. The optimum ratio between sulphur containing amino acids to lysine according to quadratic regression analysis was 0.60, for both, growth and feed conversion. Reducing the ratio between sulphur containing amino acids to lysine from 0.59 to 0.53 and 0.47 reduced body weight by 3 and 12%, resp., and elevated the feed conversion ratio by 2 and 12%, resp. An increase of the ratio between sulphur containing amino acids to lysine from 0.59 to 0.65 failed to increase the animal performance. In contrast to animal performance parameters, optimum carcass characteristics (eye muscle area, fat area above eye muscle, meat-fat ratio and lean percentage) were achieved already at a ratio of sulphur containing amino acids to lysine of 0.53.     

杜长大中猪饲粮适宜蛋白质及赖氨酸水平试验

试验采用1×3因子设计,选取杜长大三元杂种中猪60头,阉公和母猪各半,随机分为3个处理组,每个处理组设2个重复(阉公和母猪各一个重复),每个重复10头猪,同性别的猪饲养在一个栏内。按3种粗蛋白质水平(17.5%,16.1%,15.1%)、3种赖氨酸水平(0.92%,0.83%,0.75%)组合配制3种试验饲粮(能量水平一致,消化能均为13.5MJ/kg),分别饲喂3个处理组。试验结果表明,40～70kg的混养猪群,饲粮以粗蛋白质15.1%、总赖氨酸0.75%的水平为适宜。40～70kg杜长大阉公猪,饲粮以粗蛋白质15.1%、总赖氨酸0.75%的水平为适宜;同阶段青年母猪,饲粮以粗蛋白质17.5%、总赖氨酸0.92%的水平为适宜。     

Influence of genetic capacity for lean tissue growth on rate and efficiency of tissue accretion in pigs fed ractopamine.

The influence of genetic capacity for lean tissue (LT) growth on responses of pigs to ractopamine, in terms of rate and efficiency of body growth and the distribution and accretion rate of body tissues, was determined in this study. Two sources of pigs representing low and high LT genotypes were used. Within each source, two littermate barrows from each of eight litters were individually penned and given ad libitum access to a lysine-supplemented, corn-soybean meal diet (17.7% CP, 1.08% lysine) containing 0 or 20 ppm of ractopamine hydrochloride from 63 to 104 kg. Carcasses were physically dissected into muscle, fatty tissue, skin, and bone. Within each source, four additional pigs were killed for determination of initial body composition. Pigs of high LT genotype gained BW and muscle faster (P < .01), required less (P < .01) feed per unit of gain, and produced carcasses that contained more (P < .01) muscle and bone and less (P < .01) fatty tissue. Ractopamine increased (P < .01) weight gain and improved (P < .01) feed:gain ratio in both genotypes. Ractopamine enhanced the accretion rate and the amount of carcass muscle in both genotypes, but the degree of improvement was greater in pigs of the high than in those of the low LT genotype (genotype x ractopamine, P < .02). Ractopamine also reduced the accretion rate and amount of dissectible fat by a greater magnitude in the high LT genotype (genotype x ractopamine, P < .04). Based on these data, ractopamine increases muscle accretion to a greater degree in pigs with a high genetic capacity for LT growth than in those with a low capacity.     

Two on-farm data collection methods to determine dynamics of swine compositional growth and estimates of dietary lysine requirements

An experiment was conducted to evaluate the use of two real-time ultrasound data-collection methods to develop a dynamic assessment of live weight growth, protein and lipid accretions, and lysine requirement curves on two commercial swine operations. For the first method, pigs (40 barrows and 40 gilts) were weighed (ranging from 18 to 121 kg) and scanned ultrasonically to collect backfat depth and longissimus muscle area measurements every 3 wk in the finishing facility on two farms (serial method). For the second method, pigs (200 gilts and 200 barrows) of similar corresponding ages on the same two farms were weighed and scanned on 1 d (mass scan) at three different times (February, April, and May). Thirty-two pigs/sex were measured at approximately the same ages as with the serial scans. Pigs on farm 1 grew faster and had smaller backfat depths and larger longissimus muscle areas (P < 0.01) than those on farm 2, irrespective of method. These measurements were used to predict empty-body protein and lipid contents using nonlinear functions, which then were converted to accretion rates and lysine requirements at each BW. Protein accretion (g/d) and daily lysine requirements increased and then decreased for each sex on each farm and were higher on farm 1 than on farm 2. Data from the individual mass scans had larger standard errors for modeled live weight growth than data from the serial scans. Combining data from the three mass scans yielded growth curves with standard errors similar to those for the curves from the serial scans. For the protein accretion curves, the standard errors of the combined mass scans were approximately 20% lower than the standard errors of the serial scans. The standard errors for the modeled lysine:calorie ratio requirement from the serial scans were approximately 1% of the requirement at each BW. These results indicated that either the serial or mass scan data-collection method is a practical means of determining on-farm growth and daily protein and lipid accretion rates, which can be used to determine the farm-specific lysine requirements of growing-finishing pigs.     

低蛋白日粮中氨基酸含量及其与赖氨酸的比率、净能浓度对育肥猪生长性能、胴体组分和饲料成本的影响

随着遗传育种的不断改良,现代猪的瘦肉增重会越来越快,而且随着低蛋白氨基酸加强型日粮的广泛使用,在过去的几十年里,人们对于育肥猪氨基酸的需求做了大量的研究。本文主要概述了体重70 kg左右至出栏的育肥猪对氨基酸和净能的需求。过去几年里,对于现代高瘦肉型的猪,在70～115 kg这一阶段,赖氨酸的需求量有所提高,而最佳的净能需要略微下降。结果显示,低蛋白日粮和额外添加晶体氨基酸对于控制成本是可行有效的,只要日粮中氨基酸和净能的水平可以满足产肉需要就不会影响猪的生长性能和胴体参数。     

Evidence of a specific dietary selection for lysine by the piglet

The ability of animals to appropriate sources of food and select among them to obtain a nutritionally adequate diet that is best suited for their physiologic status has been examined in numerous species, but considerable research has addressed self-selection trials with chicks. Observations on diet preference have led to the assumption that birds have an innate ability to regulate their intake of macro- and micronutrients, and that they can do so with a considerable degree of precision (e.g. Holcombe et al. 1975, 1976; Elkin et al. 1985; Harper and Peters 1989; Emmerson et al. 1991; Steinruck et al. 1991a,b; Steinruck and Kirchgessner 1993a,b,c; Shariatmadari and Forbes 1993; Forbes and Shariatmadari 1994, 1996). Experimental evidence also shows that domesticated pigs which are offered a choice between two diets will select a diet containing an adequate amount of protein in preference to one that is deficient in protein, or will select specific proteins among various protein sources (Robinson 1974; Kyriazakis et al. 1990; Kyriazakis and Emmans 1992, 1993; Bradford and Gous 1992; Roberts and Azain 1997). The characteristic amount of a specific protein selected by the animals appeared to be related to the quality of the protein source. This was obvious from a few amino acid selection studies showing that growing-finishing pigs have the ability to select preferentially amino acid-adequate diets over amino acid-deficient diets within a few days (Devilat et al. 1970; Robinson 1975a,b; Davey 1978; Henry 1987, 1993). In contrast, there are also some exceptions to the hypothesis that selection of diet is related to the nutritional quality of the protein fed (Ashley and Anderson 1975). However, some of those studies are not conclusive due to changes in preferences by the animals over time and differences in protein source, palatability and amino acid pattern between the test diets. Since, an investigation of a self-selection behaviour by piglets has rarely been studied in detail, the purpose of this research was to determine whether piglets that are given a choice of diets with high or low lysine contents can regulate the intake of each to optimize lysine intake and performance. The objectives of this study were to determine the preference of piglets for diets varying in lysine content and to determine whether the preferences for these diets change with time. This indispensable amino acid was selected for study because it is first limiting in conventional diets for growing pigs.     

日粮能量、粗蛋白和赖氨酸水平对生长肥育猪采食量的影响

本文对Journal of animal science杂志上近9年（1997-2005）发表的17篇文献进行了日粮能量，粗蛋白，赖氨酸水平和体重对生长肥育猪（15kg-110kg）采食量影响的分析，得出回归方程，日采食量（ADFI）＝6.19＋0.018BW（体重，kg）-1.502ME（代谢能，Mcal/kg）（R^2=0.65,n=127）,并将议程计算数值与NRC的推荐进行了比较，结果表明该回归议程具有一定的实用性.     

The effect of energy density and the lysine to energy ratio of diets on the performance of piglets

Introduction   The aim in the feeding of piglets is to realize the maximum growth rates, according to the high growth capacity of these animals. In this respect, the supply of energy and essential amino acids is of particular significance. Among the essential amino acids, lysine, as the first growth-limiting amino acid, plays a predominate role. In the practical feeding of piglets, the recommendation is to start feeding, after weaning at 4 weeks of age, with a diet containing 13.4–13.8 MJ metabolizable energy (ME) per kg and a lysine concentration of 12.1–12.4 g/kg, which represents a ratio between lysine and energy of 0.9 g/MJ ME. After the initial phase, when the live weight is in the range 20–30 kg, it is recommended that the dietary energy is reduced to 13.0–13.4 MJ ME/kg and the lysine concentration to a range of 10.7–11.0 g/kg (representing a lysine : energy ratio of 0.82 g/MJ ME) (DLG 1996). The present study was carried out to investigate whether this recommended phase-feeding system allows maximum growth performance in piglets, or whether a constant high energy and lysine concentration during the whole rearing period is superior with regard to growth performance of piglets. Therefore, two experiments were carried out with early-weaned piglets. The first experiment, using a bifactorial design, investigated the effects of the dietary energy density and the ratio between lysine and energy on the growth performance of piglets at constant levels during the whole phase of 8–30 kg live weight. The second experiment, using a similar experimental design, was conducted to investigate the combined effect between those factors in the second phase, at live weights between 20 and 30 kg.     

The effect of dietary lysine restriction during the grower phase and subsequent dietary lysine concentration during the realimentation phase on the performance, carcass characteristics and nitrogen balance of growing–finishing pigs

Two experiments (exp.) were conducted to determine the effect of dietary lysine restriction during the grower phase and subsequent dietary lysine concentration during realimentation on the performance, carcass characteristics and nitrogen (N) balance of growing–finishing pigs. Seventy-two pairs of crossbred [meatline sires × (Large White × Landrace) dams] pigs (36 pairs entire male, 36 pairs female) were used in a 2 × 4 factorial performance study (exp. 1, 35 to 96 kg). The two factors were Diet1 (two lysine levels: LO or HI, day (d) 0 to 35) and Diet2 (four lysine levels: LO, M1, M2 and HI, d36 to slaughter). A further 30 boars were used in a 2 × 3 factorial N-balance study (exp. 2, 31 to 42 kg; Diet1: LO or HI; Diet2: LO, M3 and HI). The crude protein (CP) and lysine contents of the five isoenergetic (14.0 MJ DE/kg) diets were: LO (139 g/kg CP, 8.1 g lysine/kg), M1 (162 g/kg CP, 9.7 g lysine/kg), M2 (190 g/kg CP, 11.4 g lysine/kg), M3 (180 g/kg CP, 10.7 g lysine/kg) and HI (217 g/kg CP, 13.1 g lysine/kg). Diets were based on barley, wheat and soyabean meal with added vitamins, minerals and amino acids. Ratios of amino acids relative to lysine were similar for all diets. From d0 to 35 in exp. 1, pigs fed LO had lower daily gains (ADG: 785 vs. 939 g/day; P < 0.001), daily lysine intakes (DLYIN: 14.4 vs. 22.6 g/day; P < 0.001) and poorer feed conversion ratios (FCR: 2.28 vs. 1.84 kg/kg; P < 0.001) than pigs fed HI. From d36 to slaughter, pigs initially fed LO had higher ADG than those initially fed HI (948 vs. 879 g/day; P < 0.01). However, from d0 to slaughter, pigs initially fed LO had lower ADG (868 g/day; P < 0.01) and DLYIN (19.1 g/day; P < 0.001) than those fed HI (913 g/day and 23.3 g/day respectively). There was a Diet1 × Diet2 interaction for FCR from d36 to slaughter and d0 to slaughter (P < 0.05). FCR of pigs previously fed LO improved with each increase in dietary lysine concentration up to 13.1 g/kg (HI), but improvement was only evident for lysine concentrations up to 11.4 g/kg (M2) for pigs previously fed HI. In exp. 2, Diet1 was fed for an initial 5-day collection period (after adjustment to crate; C1). Diet2 was then fed and immediately there were 2 successive 5-day collection periods (C2 and C3). A Diet1 × Time interaction (P < 0.001) indicated that although N retention (NRET) during C1 was lower for pigs fed LO, there was no difference during C2 and C3 in NRET of pigs initially fed either LO or HI (14.5 vs. 25.0 g/day; 23.2 vs. 23.0 g/day; 26.0 vs. 26.6 g/day, for C1, C2 and C3, respectively). However, a similar interaction indicates that although N excretion (NEX) was 23% lower for LO compared with HI pigs during C1, there was no residual reduction in NEX of pigs initially fed LO (P < 0.01: 8.9 vs. 11.6 g/day; 12.3 vs. 12.7 g/day; 13.8 vs. 14.0 g/day, for C1, C2 and C3, respectively). Exp. 1 indicated improved performance and an ability to respond positively to higher lysine concentrations during realimentation for previously restricted compared with unrestricted pigs, however, overall performance was reduced. However, exp. 2 indicated that although NRET of initially restricted pigs increased during realimentation, it did not surpass that of unrestricted pigs. This apparent discrepancy may have been due to the time period of the N balance study.     

Nitrogen balance during compensatory growth when changing the levels of dietary lysine from deficiency to sufficiency in growing pigs

Two experiments were conducted to elucidate the nitrogen (N) balance of pigs exhibiting compensatory growth when changing the dietary lysine levels from deficiency to sufficiency. Experiment 1 elucidated whether pigs exhibited compensatory growth with dietary lysine sufficiency. Twenty 6‐week‐old males were assigned to one of two treatments: control and LC (lysine and control). Control pigs were fed a control diet throughout the 24‐day experimental period, whereas LC pigs were fed a low lysine diet until day 21 of the experiment, followed by the control diet until the end of experiment. The dietary lysine sufficiency treatment induced an 80% increase in the growth rate of LC pigs (P < 0.05). Experiment 2 focused on the N balance of pigs that exhibited compensatory growth with dietary lysine sufficiency. Eighteen 6‐week‐old males were assigned to one of three treatments: control, LC, and LL (low lysine). LL pigs were fed a low lysine diet throughout the 24‐day experimental period. Pigs that exhibited compensatory growth with dietary lysine sufficiency tended to retain a higher amount of N than control pigs (P = 0.10). These finding suggest that the compensatory growth induced in pigs by dietary lysine sufficiency was partly attributable to a higher level of N retention.     

Evaluation of energy values of high-fiber dietary ingredients with different solubility fed to growing pigs using the difference and regression methods

The objective of this study was to compare the energy values of high-fiber dietary ingredients with different solubility (sugar beet pulp [SBP] and defatted rice bran [DFRB]) in growing pigs using the difference and the regression methods. A total of 21 barrows (initial BW, 40.5 ± 1.2 kg) were assigned to 3 blocks with BW as a blocking factor, and each block was assigned to a 7 × 2 incomplete Latin square design with 7 diets and two 13-d experimental periods. The 7 experimental diets consisted of a corn-soybean meal basal diet and 6 additional diets containing 10%, 20%, or 30% SBP or DFRB in the basal diet, respectively. Each of the experimental periods lasted 12 d, with a 7 d dietary adaptation period followed by 5-d total fecal and urine collection. Results showed that the digestible energy (DE) and metabolizable energy (ME) of the SBP determined by the difference method with different inclusion levels (10%, 20%, or 30%) were 2,712 and 2,628 kcal/kg, 2,683 and 2,580 kcal/kg, and 2,643 and 2,554 kcal/kg DM basis, respectively. The DE and ME in the DFRB evaluated by the difference method with 3 different inclusion levels were 2,407 and 2,243 kcal/kg, 2,687 and 2,598 kcal/kg, and 2,630 and 2,544 kcal/kg DM basis, respectively. Different inclusion levels had no effects on the energy values of each test ingredient estimated by the difference method. The DE and ME of the SBP and the DFRB estimated by the regression method were 2,562 and 2,472 kcal/kg and 2,685 and 2,606 kcal/kg DM basis, respectively. The energy values of each ingredient determined by the regression method were similar to the values estimated by the difference method with the 20% or 30% inclusion level. However, the energy values of the SBP and DFRB estimated by the difference method with the 10% inclusion level were inconsistent with the values determined by the regression method (P < 0.05). In conclusion, the regression method was a robust indirect method to evaluate the energy values for high-fiber ingredients with different solubility in growing pigs. If the number of experimental animals was limited, the difference method with a moderate inclusion level (at least 20%) of the test high-fiber ingredient in the basal diet could be applied to substitute the regression method.     

Effects of dietary lysine/protein ratio and fat levels on growth performance and meat quality of finishing pigs

This study aimed to evaluate the effects of dietary lysine/protein ratio and fat levels on the growth, carcass characteristics and meat quality of finishing pigs fed feed made from food waste, including noodles and chocolate. Four dietary treatments, 2 levels of lysine/protein ratio (0.035 and 0.046) and 2 levels of fat (3.3% and 6.0%), were adapted to a 2 × 2 factorial arrangement. Each diet for the finishing pigs contained the same levels of adequate crude protein (16%) and lysine (0.58–0.75%), and similar levels of high total digestible nutrients (90.2–92.6%). In total, 32 LWD pigs with an average body weight of 57.2 kg were assigned to 4 dietary groups. The pigs were slaughtered at about 115 kg. Growth performance was not influenced by the dietary treatments. Carcass characteristics were slightly influenced by the dietary fat level. As the dietary lysine/protein ratio decreased, the marbling score of Longissimus dorsi muscle increased and the intramuscular fat (IMF) increased from 6.82% to 9.46%. Marbling score was not significantly influenced by the dietary fat level. These results indicate that IMF increased without adverse effects on growth, carcass characteristics and meat quality, when pigs were fed a diet with low lysine/protein ratio.