The effect of amino acid restriction during the grower phase on compensatory growth, carcass composition and nitrogen utilisation in grower–finisher pigs

Three hundred and ninety six pigs weighing 42 kg (s.d. +/− 2.5 kg), (progeny of Landrace × Large White sows × Meatline boars) (216 boars and 180 females) were assigned to four dietary treatments to determine the effects of restricting dietary lysine during the grower period (approximately 42 to 63 kg) on nitrogen (N) intake, retention and excretion during the finisher period (approximately 63 kg to slaughter at 94 kg). Two experiments, a performance experiment (nine replicates/treatment) and a N balance experiment (four replicates/treatment) were carried out. The experimental treatments were (1) 1.25% lysine from d 0 to d 28 and 1.05% lysine from d 29 to slaughter (HM), (2) 1.05% lysine from d 0 to slaughter (MM), (3) 0.85% lysine from d 0 to d 28 and 1.05% lysine from d 29 to slaughter (LM) and (4) 0.85% lysine from d 0 to slaughter (LL). All diets were pelleted and formulated to contain 13.8 MJ DE/kg. The pigs were group fed in mixed sex pens using single space feeders (11 pigs/feeder, 6 boars and 5 females). In the N balance experiment, sixteen entire male pigs, after 16 days on the diets were placed individually in metabolism crates and urine and faeces were collected. The pigs offered the 0.85% lysine diets during the grower period had a lower average daily gain (ADG) and a poorer feed conversion ratio (FCR) than the pigs offered 1.25% and 1.05% lysine diets (P < 0.05). During the early finisher period (days 29–42) and overall finisher period (days 29–56) pigs on treatment LM had a higher ADG (P < 0.01) and a better FCR (P < 0.05) than pigs on treatment LL. Pigs on treatment LM also had a better FCR than pigs on treatment HM and MM (P < 0.05) during the early finisher period. Pigs on treatment LM had a significantly (P < 0.05) higher lean meat proportion than pigs on treatment LL. During the grower N balance, pigs on the 0.85% lysine diets (treatments LM and LL) had lower N intakes (P < 0.001), N excretions (P < 0.001) and a higher (P < 0.001) nitrogen utilisation than pigs on treatments MM and HM. During the finisher N balance, pigs on treatment LL had a lower N intake (P < 0.001), N excretion (P < 0.01) and N retention (P < 0.05) than pigs on all other treatments. In conclusion, restricting dietary lysine during the grower period reduced growth rate but resulted in a more efficient growth during the early finisher period once dietary lysine was restored.     

Growth performance and carcass traits of pigs subjected to marginal dietary restrictions during the grower phase.

Sixty-four individually housed pigs were used to investigate the effect of amino acid content of finisher diets on growth performance of pigs subjected to marginal dietary amino acid restrictions (80% of the 1988 NRC lysine recommendation) during the grower phase. In each of the two trials, low- and high-amino-acid grower diets (.421 and .765 g lysine/MJ DE, respectively) and four finisher diets (.421, .516, .612, and .707 g lysine/MJ DE) were randomly assigned within sex to 16 gilts and 16 castrated males weighing 23.0 +/- 2.0 kg in a 2 x 4 factorial arrangement of treatments. The average weight of pigs after a completion of diet change was 50.4 +/- 2.1 kg. All pigs were slaughtered at an average weight of 105.2 +/- 4.1 kg. Ultrasound backfat thickness was measured at the time of diet change and before slaughter. Pigs were allowed ad libitum access to feed and water. During the grower phase, pigs fed the high-amino-acid diet grew faster (P < .001) and more efficiently (P < .001) and had less ultrasound backfat (P < .001) than those fed the low-amino-acid diet. The grower diet had no effect on weight gain during the finisher phase. Consequently, pigs fed the high-amino-acid grower diet had better overall weight gain (P < .01) than those fed the low-amino-acid diet. The rate of lean accretion was, however, similar between the two groups of pigs. Furthermore, pigs fed the low-amino-acid grower diet seemed to have better carcass quality, as indicated by less ultrasound backfat (P < .01) and larger carcass longissimus muscle area (P < .05). Average and 10th rib carcass backfat decreased linearly (P < or = .05) and lean accretion rate improved linearly (P < .05) as the amino acid content of finisher diets increased, but there was no grower x finisher diet interaction in these and other response criteria. Although no evidence of compensatory weight gain was observed, it is possible that compensatory lean tissue growth may have occurred in pigs subjected to early amino acid restrictions at the expense of fatty tissue growth.     

Lysine restriction during grower phase on growth performance,blood metabolites,carcass traits and pork quality in grower finisher pigs

Abstract

The effects of lysine restriction during grower phase and realimentation during finisher phase on growth performance, nutrient digestibility, blood metabolites, carcass traits and pork quality were studied. Sixty-four pigs (two castrated males and two females per pen) weighing 34.34±5.22 kg were assigned to four dietary treatments. During grower (35–55 kg), pigs were fed isoenergetic lysine-restricted diets. The different lysine content of diets were 0.950 (NRC recommendation), 0.760, 0.665 and 0.570%, corresponding to lysine restriction of 20, 30 and 40%. Then all pigs were fed with common finisher 1 (55–85 kg) and 2 (85–115 kg) diets. Lysine restriction during the grower phase resulted in poor performance and lower concentration of blood metabolites but improved the nutrient digestibility and efficiency of lysine utilization. Compensatory growth response in terms of improved weight gain and feed efficiency was observed in pigs previously fed lysine-restricted diets during finisher 1, but the concentration of blood urea nitrogen and total protein were lower. No differences in growth performance, digestibility of nutrients and blood metabolites were noted during finisher 2. Lysine restriction of grower diets decreased the dressing percentage (quadratic, P=0.024), and protein content of longissimus muscle (linear P=0.034, and quadratic P=0.009). Thus, it could be concluded that pigs subjected to lysine restriction during grower phase exhibited compensatory growth responses in weight gain and improved efficiency of feed and lysine utilization for weight gain and lean accretion during finisher phase.     

Selection for lean growth efficiency in Duroc pigs influences pork quality

A unique line of Duroc pigs was established by intensive selection for increased lean growth efficiency. The objective of this study was to determine the influence of this selection strategy on fresh pork quality traits. Two lines of Duroc pigs originating from the same foundation herd were evaluated. One line was selected for lean growth efficiency over five generations (Select line), and the other was a contemporary line maintained from the foundation herd (Control line). All pigs in the trial tested negative for the halothane gene. Selection for lean growth efficiency resulted in improved lean gain, carcass lean, increased loin eye area, and less overall carcass fat. The Select line had significantly lower subjective firmness scores in longissimus and significantly greater amounts of moisture and protein lost as measurable drip in longissimus, semimembranosus, and semitendinosus. There were no differences in subjective color scores or in Hunter L, a, and b values between lines. No selection line differences were observed in glycolytic potential or ultimate pH. The longissimus and the semitendinosus exhibited significantly lower early postmortem pH values in Select line pigs. Warner-Bratzler shear values were higher for Select line longissimus chops. Degradation of troponin-T was decreased in the Select line longissimus samples. This result suggests that reduced degradation of myofibrillar proteins may be associated with increased moisture and protein lost during storage. This research points out that elimination of the halothane gene will solve some but not all of the genetically influenced pork quality problems faced by the industry. The Select line of pigs appears to be more prone to producing pork that is soft and exudative, indicating a link between soft and exudative pork and some genetic selection strategies may exist. Therefore, it appears that selection for some economically important traits, such as feed efficiency or increased lean growth in the absence of the halothane gene, may compromise pork quality.     

Serum neuropeptide Y (NPY) and leptin concentrations in pigs selected for components of efficient lean growth

Responses in log transformed serum neuropeptide Y (NPY) concentration and leptin concentration after six generations of divergent selection on components of efficient lean growth in pigs were measured. From an animal breeding perspective, serum NPY and/or leptin concentrations could be used as physiological predictors of genetic merit if there were significant responses to selection. At 90 kg liveweight, log transformed serum NPY concentrations were increased with divergent selection for low food conversion ratio (LFC) (6.31 versus 5.72, SED 0.09 log(pmol/L)) or for high lean growth rate (LGA) (5.80 versus 5.37 log(pmol/L)) but not with selection on daily food intake (DFI) (6.26 versus 6.14 log(pmol/L)). Selection for high DFI was associated with increased serum leptin concentration (3.06 versus 2.45, SED 0.21 ng/mL human equivalent (HE)) as was selection for low LFC (3.04 versus 2.46 ng/mL HE). Correlations between leptin and predicted lipid weight increased with stage of test (0.13, 0.34 and 0.43, SE 0.08 at 30, 50 and 75 kg). The high correlations between successive serum NPY concentrations (0.80, SE 0.11) suggest that changes in body composition with time would not be reflected in serum NPY concentrations. Serum NPY and, to a lesser extent, serum leptin concentrations were insensitive to dietary differences in total lysine: energy and indicated that studies using a genetic resource population of animals may be more powerful than nutritional studies using isoenergetic diets differing in lysine content to examine aspects of function of serum concentrations of NPY and leptin in pigs.     

The efficiency of and requirements for selected amino acids in growing female pigs. 3. Threonine

With the help of an N utilization model by Gebhardt (1963) and its further development the threonine efficiency coefficients (kThr) of wheat, barley, maize, rye and peanut oil meal of different charges with a supply of L-lysine monohydrochloride, DL-methionine and DL-tryptophan was ascertained with a total of 59 female pigs of the local breed (35-45 kg live weight) by means of an N balance method. The variation range of kThr was between 0.61 and 0.87 based on a threonine effectivity of wheat gluten with lysine as standard. The derived threonine requirement for 100 g daily protein retention with a live weight of 40 kg was ascertained as 6.9 g (kThr = 1) and 9.6 kg (kThr = 0.71 as mean values of the protein sources studied). The proof of threonine limitation in the protein sources was provided by the supplementation of DL threonine.     

Effects of long-chain fatty acid supplementation on the growth performance of grower and finisher pigs: a meta-analysis

Background: Supplementation of feed with long-chain fatty acids(LCFAs) during the grower and finisher phases has long been discussed as a growth promotion strategy in pigs, but its effects are inconsistent. The purpose of our study was to comprehensively evaluate its effects on the growth performance based on the average daily gain(ADG), average daily feed intake(ADFI) and gain: feed(G:F) ratio and to unveil the roles of the basal diet, LCFA concentration and LCFA saturation.Results: We searched the Pub Med and Web of Science databases(articles published from Jan 1 st, 2000, to Sep 30 th,2018; restricted to English) and compared LCFA-supplemented diets with control diets. We retrieved 2346 studies, 18 of which(1314 pigs, 26 records) were eligible for our analysis. We used a random-effects model to calculate the weighted mean differences(WMDs) and 95% confidence intervals(CIs). LCFA supplementation in the grower-finisher phase improved the ADG(WMD = 41.74 g/d, 95% CI: 8.81 to 74.66, P = 0.013) and G:F ratio(WMD = 0.019, 95% CI: 0.006 to 0.032, P = 0.003). For supplementation solely in the finisher phase, we found a similar performance in the ADG(WMD = 39.93 g/d, 95% CI: 26.48 to 53.38, P 0.001) and G:F ratio(WMD = 0.019, 95% CI: 0.006 to 0.032, P 0.001) but a reduction in the ADFI(WMD =-83.863 g/d, 95% CI:-156.157 to-11.569, P = 0.023). Specifically, approximately 5%LCFA supplementation in the finisher phase had significant effects on the ADG(WMD = 51.385 g/d, 95% CI: 35.816 to66.954, P 0.001), ADFI(WMD =-102.869 g/d, 95% CI:-189.236 to-16.502, P = 0.02) and G:F ratio(WMD = 0.028, 95%CI: 0.018 to 0.039, P 0.001), whereas a concentration of approximately 1% exhibited no effects.Conclusions: Overall, regardless of the basal diet and saturation, LCFA supplementation greatly improves the growth performance of grower and finisher pigs, primarily by increasing the energy density.     

The efficiency of nitrogen retention during compensatory growth of food-restricted broilers

1. Two experiments were conducted to investigate the influence of compensatory growth, induced by early quantitative food restrictions, on the efficiency of nitrogen-retention in two lines of Ross broilers. 2 . Birds were restricted to 80% of the ad libitum intake of the previous 24 h of the control group from d 4 to d 7. After the period of restrictions all birds were fed ad libitum . 3 . In both trials, the final body weight of the restricted Ross 208(308) birds was similar or even higher than that of the control group. For the Ross 508 line, compensatory growth was substantial in the first trial, but non-existent in the second trial. In all cases, the mortality of restricted birds was lower than in control birds. 4. Not only environmental factors, but mainly chick quality, seemed to have a major influence on the capacity of the chickens to establish compensatory growth. 5. As compensatory growth was established, some improvement in N retention was induced. Although differences were not significant, they may be environmentally important. 6. It is concluded that a retardation of the early growth of fast growing broiler chickens can, in certain circumstances, reduce mortality and increase performance and N retention.     

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.     

Changes in the muscle proteome after compensatory growth in pigs

Sixteen female pigs (Duroc x Landrace x Large White) were divided into 2 groups, which had either free access to the diet (control group) or were feed-restricted from d 28 to 80 and then had free access to the diet (compensatory growth group). The sensory analysis showed that the pigs exhibiting compensatory growth produced meat with increased tenderness compared with control pigs (P < 0.05). To gain further knowledge of the influence of compensatory growth on meat tenderness, the sarcoplasmic protein fraction of muscle tissue was studied at the time of slaughter and 48 h postmortem using proteome analysis. At slaughter, 7 different proteins were found to be affected by compensatory growth: HSC70, HSP27, enolase 3, glycerol-3-phosphate dehydrogenase, aldehyde dehydrogenase E2, aldehyde dehydrogenase E3, and biphosphoglycerate mutase. The HSC70 and HSP27 both belong to the heat shock family and are known to play a role during muscle development. Hence, they may be affected by compensatory growth and increased protein turnover. Forty-eight hours after slaughter, 8 different proteins were found to be affected by compensatory growth: myosin light chain (MLC) II, MLC III, sulfite oxidase, chloride intracellular channel 1, 14-3-3 protein gamma, elongin B, and phosphohistidine phosphatase 14. The changes observed on MLC II and MLC III could be a consequence of enzymatic cleavage in the neck region of the globular myosin head domain that causes the release of MLC II and MLC III from the actomyosin complex. It has previously been hypothesized that compensatory growth results in an increased postmortem proteolysis; thus it was presumed that the intensity of some protein fragments would be affected by compensatory growth. However, the peptides that were found to be affected at 48 h postmortem were all full-length proteins. The 14-3-3 protein gamma has been proposed to play a role in the contraction of muscle during rigor and may thereby have an effect on meat tenderness. This study reveals some very interesting changes in the muscle proteome affected by compensatory growth, which may be useful in understanding the relationship among compensatory growth, protein turnover, and meat tenderness.     

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.     

Reduced dietary protein level influences the free amino acid and gene expression profiles of selected amino acid transceptors in skeletal muscle of growing pigs

This study was conducted to evaluate the effect of reduced dietary protein level on growth performance, muscle mass weight, free amino acids (FAA) and gene expression profile of selected amino acid transceptors in different fibre type of skeletal muscle tissues (longissimus dorsi, psoas major, biceps femoris) of growing pigs. A total of 18 cross‐bred growing pigs (Large White × Landrace × Duroc) with initial body weight (9.57 ± 0.67 kg) were assigned into three dietary treatments: 20% crude protein (CP) diet (normal recommended, NP), 17% CP diet (low protein, LP) and 14% CP diet (very low protein, VLP). The results indicated improved feed‐to‐gain ratio was obtained for pigs fed LP and NP diets (p < 0.01), while the pigs fed VLP diet showed the worst growth performance (p < 0.01). There was no significant difference in the weights of longissimus dorsi and psoas major muscle between LP and NP groups (p > 0.05). Majority of the determined FAA concentration of LP group were greater than or equal to those of NP group in both longissimus dorsi and psoas major muscle (p < 0.01). Further, the mRNA expression levels of sodium‐coupled neutral amino acid transceptor 2, L‐type amino acid transceptor 1 and proton‐assisted amino acid transceptors 2 were higher in skeletal muscle tissue in LP group compared to those of the pigs fed NP or VLP diet. These results suggested that reduced dietary protein level (3 points of percentage less than recommended level) would upregulate the mRNA expression of amino acid transceptors to enhance the absorption of FAA in skeletal muscle of growing pigs. There seems to be a relationship between response of AA transceptors to the dietary protein level in skeletal muscle tissue of different fibre type. To illustrate the underlying mechanisms will be beneficial to animal nutrition.     

Effects of individual or combined xylanase and phytase supplementation on energy, amino acid, and phosphorus digestibility and growth performance of grower pigs fed wheat-based diets containing wheat millrun

The objective of these studies was to determine if dietary enzymes increase the digestibility of nutrients bound by nonstarch polysaccharides, such as arabinoxylans, or phytate in wheat millrun. Effects of millrun inclusion rates (20 or 40%), xylanase (0 or 4,375 units/kg of feed), and phytase (0 or 500 phytase units/kg of feed) on nutrient digestibility and growth performance were investigated in a 2 x 2 x 2 factorial arrangement with a wheat control diet (0% millrun). Diets were formulated to contain 3.34 Mcal of DE/kg and 3.0 g of true ileal digestible Lys/Mcal of DE and contained 0.4% chromic oxide. Each of 18 cannulated pigs (36.2 +/- 1.9 kg of BW) was fed 3 diets at 3x maintenance in successive 10-d periods for 6 observations per diet. Feces and ileal digesta were collected for 2 d. Ileal energy digestibility was reduced (P < 0.01) linearly by millrun and increased by xylanase (P < 0.01) and phytase (P < 0.05). Total tract energy digestibility was reduced linearly by millrun (P < 0.01) and increased by xylanase (P < 0.01). For 20% millrun, xylanase plus phytase improved DE content from 3.53 to 3.69 Mcal/kg of DM, a similar content to that of the wheat control diet (3.72 Mcal/kg of DM). Millrun linearly reduced (P < 0.01) ileal digestibility of Lys, Thr, Met, Ile, and Val. Xylanase improved (P < 0.05) ileal digestibility of Ile. Phytase improved ileal digestibility of Lys, Thr, Ile, and Val (P < 0.05). Millrun linearly reduced (P < 0.05) total tract P and Ca digestibility and retention. Phytase (P < 0.01) and xylanase (P < 0.05) improved total tract P digestibility, and phytase and xylanase tended to improve (P < 0.10) P retention. Phytase improved Ca digestibility (P < 0.05) and retention (P < 0.01). The 9 diets were also fed for 35 d to 8 individually housed pigs (36.2 +/- 3.4 kg of BW) per diet. Millrun reduced (P < 0.05) ADFI, ADG, and final BW. Xylanase increased (P < 0.05) G:F; phytase reduced (P < 0.05) ADFI; and xylanase tended to reduce (P = 0.07) ADFI. In summary, millrun reduced energy, AA, P, and Ca digestibility and growth performance compared with the wheat control diet. Xylanase and phytase improved energy, AA, and P digestibility, indicating that nonstarch polysaccharides and phytate limit nutrient digestibility in wheat byproducts. The improvement by xylanase of energy digestibility coincided with improved G:F but did not translate into improved ADG.     

Effects of ractopamine, genotype, and growth phase on finishing performance and carcass value in swine: II. Estimation of lean growth rate and lean feed efficiency

A replicated factorial experiment using 183 individually fed crossbred barrows was conducted. The pigs were fed an 18.5% CP (.95% lysine) diet with 3.594 kcal of ME/kg. The effects of five genotypes (GT): 1) Hampshire (H) X (H X Duroc [D]), 2) synthetic terminal sire line, 3) (H X D) X (Landrace [L] X [Yorkshire (Y) X D]), 4) L X (Y X D), and 5) Y X L; two levels of ractopamine (RAC) treatment: 0 and 20 ppm; and three treatment weight periods (WT): 1) 59 to 100, 2) 73 to 114, and 3) 86 to 127 kg live weight on ADG of dissected lean (ADLG) and fat standardized lean adjusted to 10% fat content (ADSLG) and feed efficiency of ADLG (LFE) and ADSLG (SLFE) were evaluated. Initial carcass lean quantity of each individual animal was determined by a regression equation (R2 = .95) generated from 30 additional barrows (six per GT) slaughtered at 59 kg and 30 (six per GT) untreated pigs slaughtered at 100 kg average live weight. Logarithmic and reciprocal transformations of dependent variables were used to stabilize heterogeneous variances and to improve normality of the residuals. Ractopamine increased (P less than .0001) ADLG, ADSLG, LFE, and SLFE, respectively, by 19.5, 25.0, 19.6, and 25.5%. Differences (P less than .001) were observed among genotypes for all traits, showing that considerable variation existed in the data and indicating that genetic improvement can be realized through the identification and selection of superior genotypes.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Interactive effects of thermal environment and dietary amino acid and fat levels on rate and efficiency of growth of pigs housed in a conventional nursery.

In four trials, 480 weanling pigs were housed in a conventional nursery maintained at 20 or 30 degrees C, which represented a cool and hot thermal environment, respectively. They were allowed ad libitum access to corn-soybean meal-dried whey diets containing .7, 1.0, or 1.3% lysine and 0 or 5% added fat (choice white grease). The pigs were weaned between 27 and 33 d of age (7.27 +/- .90 kg) and penned in groups of five for the duration of the 42-d trials. Pigs housed in the cool environment consumed more feed (P < .01), gained more weight (P < .01), and utilized feed more efficiently (P < .01) than those in the hot environment. As dietary lysine levels were increased in the 20 and 30 degrees C environments, daily weight gains and gain:feed ratios increased linearly (P < .01) from d 0 to 21 and quadratically (P < .01) from d 21 to 42. However, the magnitudes of the increases were less in the cool environment, resulting in temperature x lysine interactions (P < .05). As the pig's feed intake, body weight, and heat production increased over time, the 20 and 30 degrees C environments became progressively warmer relative to the animal's zone of thermoneutrality. The associated reductions over time in energy and lysine intakes relative to the pigs' maintenance needs resulted in an increase in the concentration of dietary lysine needed to maximize rate and efficiency of gain in the 30 degrees C environment but not in the 20 degrees C environment (temperature x lysine x period interaction, P < .10).(ABSTRACT TRUNCATED AT 250 WORDS)     

猪氨基酸消化率测定中指示剂的应用

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