Growth performance, diet apparent digestibility, and plasma metabolite concentrations of barrows fed corn-soybean meal diets or low-protein, amino acid-supplemented diets at different feeding level

Effects of electrolyte balance on intestinal barrier, amino acid metabolism, and mTORC1 signaling pathway in piglets fed low-protein diets

A proper dietary electrolyte balance (dEB) is essential to ensure optimal growth performance of piglets. In the low-protein diet, this balance may be affected by the reduction of soybean meal and the inclusion of high levels of synthetic amino acids. The objective of this experiment was to evaluate the optimal dEB of low-protein diets and its impact on the growth performance of piglets. A total of 108 piglets (initial age of 35 d) were randomly divided into 3 groups with 6 replicates of 6 pigs each as follows: low electrolyte diet (LE group; dEB = 150 milliequivalents [mEq]/kg); medium electrolyte diet (ME group; dEB = 250 mEq/kg); high electrolyte diet (HE group; dEB = 350 mEq/kg). Results indicated that the LE and HE diet significantly decreased the average daily gain, average daily feed intake, and crude protein digestibility (P < 0.05) in piglets. Meanwhile, LE diets disrupted the structural integrity of the piglets' intestines and decreased jejunal tight junction protein (occludin and claudin-1) expression (P < 0.05). Additionally, the pH and HCO3- in the arterial blood of piglets in the LE group were lower than those in the ME and HE groups (P < 0.05). Interestingly, the LE diet significantly increased lysine content in piglet serum (P < 0.05), decreased the levels of arginine, leucine, glutamic acid, and alanine (P < 0.05), and inhibited the mammalian target of rapamycin complex 1 (mTORC1) pathway by decreasing the phosphorylation abundance of key proteins. In summary, the dietary electrolyte imbalance could inhibit the activation of the mTORC1 signaling pathway, which might be a key factor in the influence of the dEB on piglet growth performance and intestinal health. Moreover, second-order polynomial (quadratic) regression analysis showed that the optimal dEB of piglets in the low-protein diet was 250 to 265 mEq/kg.

Effects of Protease in Soybean Meal-Reduced Diets on Growth Performance, Nutrient Digestibility, and Intestinal Health of Weaned Piglets

This experiment was conducted in weaned piglets to determine the effects of exogenous protease to low soybean meal (SBM) diets on growth performance, diarrhea rate, nutrient digestibility, and intestinal morphology. Seventy-two Duroc × Landrace × Yorkshire weaned barrows (21-day-old, 5.88 ± 0.95 kg) were randomly divided into four treatments with six replicates in each following a 2 × 2 factorial arrangement of SBM levels (0 to 14 d, 9%, 7.5%; 15 to 42 d, 20%, 18.5%) and protease (0 or 150 mg/kg) for a 42-day trial. Fecal samples were collected on days 11 to 14 and 38 to 42 of the experiment, and serum, intestinal tissue, and chyme samples were taken at the end of the experiments. Adding protease in low SBM diets had a significant increase in ADG (p < 0.05) and a decrease in F/G (p < 0.05). Protease significantly reduced the diarrhea rate (p < 0.05). Low SBM level decreased the apparent total tract digestibility (ATTD) of crude protein (CP) and ash (p < 0.05) but increased the ATTD of dry matter (DM), ash, organic matter (OM), and CP after the addition of protease (p < 0.05). The apparent ileal digestibility (AID) of aspartic acid (Asp), threonine (Thr), serine (Ser), alanine (Ala), lysine (Lys), and total amino acids (AAs) were significantly increased by protease supplementation (p < 0.05). Both the SBM-reduced and protease-added diets lead to lower albumin (ALB), albumin/globulin (A/G), and urea nitrogen (UREA) (p < 0.05), but greater globulin (GLOB) with low SBM diets (p < 0.05). The SBM-reduced and protease-added diets decreased the duodenum pH, respectively (p < 0.05). The protease increased the villus:crypt (V:C) in the duodenum and ileum, and ileal villus length (p < 0.05). In conclusion, the dietary supplementation of 150 mg/kg protease improved the intestinal health and performance of the weaned piglets and reversed the negative effect of a 1.5% SBM reduction in nutrient utilization, intestinal pH, and intestinal morphological parameters of weaned piglets.

Effects of dietary niacinamide and CP concentrations on the nitrogen excretion, growth performance, and meat quality of pigs

Reducing the dietary CP concentration in the formulation of low-protein diets without adverse effects on animal growth performance and meat quality remains challenging. In this study, we investigated the effects of nicotinamide (NAM) on the nitrogen excretion, growth performance, and meat quality of growing-finishing pigs fed low-protein diets. To measure the nitrogen balance, we conducted two trials: in nitrogen balance trial 1, four crossbred (Duroc × Landrace × Large White) barrows (40 ± 0.5 kg BW) were used in a 4 × 4 Latin square design with four diets and periods. The diets consisted of a basal diet + 30 mg/kg NAM (a control dose), basal diet + 90 mg/kg NAM, basal diet + 210 mg/kg NAM, and basal diet + 360 mg/kg NAM. In nitrogen balance trial 2, another four barrows (40 ± 0.5 kg BW) were used in a 4 × 4 Latin square design. The diets consisted of a basal diet + including 30 mg/kg NAM (control), basal diet + 360 mg/kg NAM, low-protein diet + 30 mg/kg NAM, and low-protein diet + 360 mg/kg NAM. To measure growth performance, two trials were conducted. In growth performance trial 1, 40 barrows (37.0 ± 1.0 kg) were randomly allocated to one of four dietary treatments (n = 10 per group), whereas in growth performance trial 2, 300 barrows (41.4 ± 2.0 kg) were randomly allocated to one of four dietary treatments, with each dietary treatment conducted in five repetitions with 15 pigs each. The four diets in the two growth performance trials were similar to those in nitrogen balance trial 2. Supplementing the diet with 210 or 360 mg/kg NAM reduced urinary nitrogen excretion and total nitrogen excretion and increased nitrogen retention comparted with the control diet (P < 0.05). Compared with the control diet, the low-protein diet with 360 mg/kg NAM reduced faecal, urinary, and total nitrogen excretion (P < 0.05) without affecting nitrogen retention and average daily gain (P > 0.05). Pigs fed the low-protein diet with 360 mg/kg NAM showed a decreased intramuscular fat content in the longissimus thoracis muscle when compared with pigs fed the control diet (P > 0.05). Our results suggest NAM as a suitable dietary additive to reduce dietary CP concentration, maximise nitrogen retention and growth performance, and decrease fat deposition in pigs.

Effects of Dietary Coated Lysozyme on the Growth Performance, Antioxidant Activity, Immunity and Gut Health of Weaned Piglets

The purpose of this study was to evaluate the effects of dietary coated lysozyme on growth performance, serum biochemical indexes, antioxidant activity, digestive enzyme activity, intestinal permeability, and the cecal microbiota in weaned piglets. In total, 144 weaned Large White × Landrace piglets were divided into six treatment groups, with 3 replicates and 8 piglets per replicate: CN, a basal diet; CL-L, CL-M, and CL-H, basal diet supplemented with 100, 150, 500 mg/kg coated lysozyme; UL, basal diet supplemented with 150 mg/kg lysozyme; and Abs, basal diet supplemented with 150 mg/kg guitaromycin for 6 weeks. Compared with the CN and UL diets, dietary CL-H inclusion increased the average daily gain (ADG) and decreased the feed/gain (F/G) ratio of piglets (p < 0.05). The addition of 500 mg/kg coated lysozyme to the diet significantly increased the total protein (TP) and globulin (Glob) plasma levels of weaned piglets (p < 0.05). Supplementation with 500 mg/kg coated lysozyme significantly increased the serum IgM concentration and increased lipase activity in the duodenum (p < 0.05). The addition of coated lysozyme and lysozyme significantly decreased the malondialdehyde (MDA) content, while the superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and total antioxidant capacity (T-AOC) levels all increased (p < 0.05). High-throughput sequencing results showed that CL-H treatment effectively improved the intestinal microbiome. The relative abundance of Terrisporobacter in the CL-H and CL-M groups was significantly lower than that in the other groups (p < 0.05). LEfSe analysis results showed that the relative abundance of Coprococcus_3 was higher in the CL-M treatment group. The marker species added to the CL-H treatment group was Anaerofilum. In summary, as a potential substitute for feed antibiotics, lysozyme is directly used as a dietary additive, which is inefficient. Therefore, we used palm oil as the main coating material to coat lysozyme. Lysozyme after coating can more effectively improve the growth performance of piglets by improving the intestinal flora, improving the activity of digestive enzymes, reducing the damage to intestinal permeability and oxidative stress in piglets caused by weaning stress, and improving the immunity of piglets.

Effects of adding potassium bicarbonate to diets with high or low crystalline lysine to influence dietary cation–anion difference on finishing pig growth performance

Dietary cation–anion difference (DCAD), calculated as Na+ + K+ – Cl− in mEq/kg of the diet, represents the influence that monovalent cations and anions from these minerals have on the acid–base status of the animal. However, the recommended range of DCAD for optimal grow-finish swine performance is variable, which may indicate an interaction between DCAD and other ingredients. The hypothesis for this study was that the addition of potassium bicarbonate (KHCO3) to increase diet DCAD when high levels of l-Lys HCl (&gt;0.35% diet) are used may potentially improve growth performance. A total of 1,944 pigs (PIC L337 × 1050, initially 35.2 ± 0.85 kg) were used in a 120-d study. Pens of pigs were blocked by BW and randomly allotted to 1 of 4 dietary treatments in a randomized complete block design. Treatments were arranged in a 2 × 2 factorial with main effects of KHCO3 (0% or 0.4%), and l-Lys HCl level (low or high). l-Lys HCl was included between 0.13% and 0.21% in low diets, and between 0.36% and 0.43% in high diets. There were 27 pigs per pen and 18 replicates per treatment. Treatment diets were corn-soybean meal-based and formulated in four dietary phases (35–60 kg, 60–85 kg, 85–105 kg, and 105–130 kg). Dietary treatments were formulated such that in each phase the diet containing a low level of l-Lys HCl without KHCO3 and the diet containing a high level of l-Lys HCl with KHCO3 had similar calculated DCAD values (169–232 mEq/kg). Additionally, the diet with a low level of l-Lys HCl with KHCO3 was formulated to have the highest DCAD in each phase (220–281 mEq/kg), while the diet with a high level of l-Lys HCl without KHCO3 was formulated to have the lowest DCAD (118–182 mEq/kg). Overall, there was no evidence (P &gt; 0.10) for a KHCO3 × l-Lys HCl interaction or main effect for final BW or any observed growth response or carcass characteristics. The results of this study suggest that supplementing KHCO3 to finishing pig diets with either high or low levels of l-Lys HCl and the corresponding changes in DCAD values did not impact growth performance or carcass characteristics.

Effect of low protein diets added with protease on growth performance, nutrient digestibility of weaned piglets and growing-finishing pigs

The objective of this study was to evaluate the effects of low protein diets added with protease on growth performance, nutrient digestibility, and blood profiles of weaned piglets and growing-finishing pigs. A total of 96 weaned pigs ([Yorkshire × Landrace] × Duroc) with average body weight (BW) of 6.99 ± 0.21 kg were used in a 20-week experiment. The dietary treatments were arranged in a 2 × 3 factorial design. Treatments were as follows: In phase 1 (1–2 weeks), two protein levels as high protein (HP; 19.0%), low protein (LP; 17.0%), and three protease (PT) levels (PT0, 0%; PT1, 0.3%; and PT2, 0.5%); in phase 2 (3–4 weeks), protein levels (HP, 18.05%; LP, 16.15%) and protease levels (0%, 0.3%, and 0.5%); in phase 3 (5–12 weeks), protein levels (HP, 17.1%; LP, 15.3%) and protease level (0%, 0.15%, and 0.3%); in phase 4 (13–20 weeks), protein levels (HP, 16.15%; LP, 14.45%) and protease level (0%, 0.15%, and 0.3%). At 4 weeks and 20 weeks after treatment, BW was higher (p < 0.050) in the PT2 group than PT0 group. From weeks 0 to 4, average daily gain (ADG) and feed efficiency (G/F) were higher (p = 0.006 and p = 0.014; p = 0.014 and p = 0.044, respectively) in the PT2 group than PT0 and PT1 groups. From weeks 16 to 20, ADG and G/F were higher (p < 0.001 and p = 0.009; p = 0.004 and p = 0.033, respectively) in the PT2 group than PT0 and PT1 groups. Crude protein (CP) digestibility was higher (p = 0.013, p = 0.014, and p = 0.035, respectively) in the low protein (LP) group than high protein (HP) group at weeks 4, 12, and 20. At weeks 4 and 20, the LP diet group had lower (p < 0.001 and p = 0.001, respectively) blood urea nitrogen (BUN) levels than the HP diet group. Therefore, a low CP diet added with protease could increase growth performance and CP digestibility of weaned piglets and growing-finishing pigs.

Comparison of absorption kinetics and utilisation of DL-methionine (DL-Met), Met-Met product (AQUAVI® Met-Met), and protein-bound methionine (PB-Met) by female broiler chickens

1. Two experiments were conducted to determine the effects of different methionine (Met) sources regarding their absorption kinetics and utilisation in female single-meal-fed broiler chickens.2. A total of 340, one day old female Ross 308 broiler chickens were fed commercial starter and grower diets for 38 d. Birds were then allocated to treatment diets in two experiments as a completely randomised design with four replicates of five chicks per each until 60 d of age. In experiment 1, a 2 × 5 factorial design was used to investigate the effect of two sources (DL-Met and AQUAVI®Met-Met) and five equimolar levels (0.4, 0.8, 1.2, 1.6, and 2 g/kg) in the diet. In experiment 2, different proportions of protein-bound methionine (PB-Met) to DL-Met (0.4:1.6, 0.8:1.2, 1.2:0.8: 1.6:0.4, and 2:0 g/kg) were incorporated into a basal diet deficient in Met. During the experiment, chickens received 90 g of pelleted feed for a time period of 17 ± 2.5 min, once daily.3. The results indicated that chickens fed diets supplemented with DL-Met and Met-Met showed a rapid rise in plasma Met 1 h after feeding, with a sudden drop at 2 h after feeding. In contrast, chickens fed PB-Met substituted diets showed a gradual plasma peak at 1 and 2 h postprandial (P < 0.01). Plasma homocysteine (HCY) content increased to 34.38 and 40.43 μmol/l with DL-Met_2.0 and Met-Met_2.0 diets, while it decreased to 25.68 μmol/l with PB-Met_2.0(P ≤ 0.01). Chickens that received the PB-Met_2.0 diet had higher (P ≤ 0.01) protein utilisation (0.54 g/g) and lower excreta nitrogen content (4.04 g/100 g excreta), which demonstrated the benefits of feeding a protein-bound Met source. The efficiency of Met utilisation was 0.69 g/g in chickens fed PB-Met_2.0 diet, but only 0.36 and 0.41 g/g in those fed DL-Met_2.0 and Met-Met_2.0 (P ≤ 0.01).4. The observed utilisation coefficient of DL-Met and Met-Met for single-meal meat-type chickens was lower than expected. The synchronisation of intestinal Met absorption maintained the efficiency of utilisation, which was related to the sources of added Met, with protein-bound Met showing the best utilisation and least excretion.

Impact of reduced dietary crude protein levels and phytase enzyme supplementation on growth response, slurry characteristics, and gas emissions of growing pigs

This experiment was carried out to evaluate the effect of reduced dietary crude protein (CP) levels supplemented with or without exogenous phytase on growing pigs. Six dietary treatments arranged in a 3 × 2 factorial arrangements of 3 CP levels (containing 14%, 16%, and 18% CP) supplemented each with or without 5,000 FTU/g phytase enzyme. Thirty growing pigs (average weight of 17.80 ± 0.10 kg) were allotted to the six dietary treatments in a complete randomized design. The final weight, daily weight gain, and feed conversion ratio (FCR) increased significantly with increasing CP levels. While, phytase supplementation improved (p = .044) FCR in pigs. Total solid and volatile solid content of the slurry were higher (p = .001) in pigs fed 14% and 16% CP diets supplemented with phytase when compared with other treatment groups. Concentration of methane gas emitted was lowest (p = .001) in the slurry of pigs fed 14% CP diet with or without phytase and those fed 16% CP diet with phytase supplementation. In conclusion, reduction in dietary CP levels resulted in reduced weight gain and poor FCR. While, reduced CP with phytase supplementation reduced concentration of methane gas emitted.

Protease em dietas com baixa proteína contendo farinha de Penas para codornas de corte

RESUMO Objetivou-se avaliar a suplementação de protease em dietas com baixa proteína contendo farinha de penas (FP) sobre o desempenho e o rendimento de carcaça de codornas de corte. Foram utilizadas 240 codornas, machos, distribuídas em delineamento inteiramente ao acaso, em esquema fatorial 2x 3 (com e sem protease x 3 níveis de FP (0%, 5% e 10%)), totalizando seis tratamentos (dieta reduzida (DR) em 8% da exigência de proteína bruta e aminoácidos + 0% FP; DR + 5% FP; DR + 10% FP; DR + 0% FP + protease; DR + 5% FP + protease e DR + 10% FP + protease), quatro repetições de 10 codornas por parcela, nas fases de oito-21 dias e oito-35 dias de idade. Observou-se interação (P≤0,05) entre os níveis de FP e protease no ganho de peso de oito-21 dias. Os níveis de FP influenciaram (P≤0,05) o consumo de ração e o ganho de peso de oito-21 e oito-35 e a conversão alimentar de oito-21 dias. Verificou-se interação (P≤0,05) entre aprotease e a inclusão de FPpara o peso corporalaos 35 dias. Conclui-se que aFP pode ser utilizada em até 5% em dietas para codornas de corte semsuplementação comprotease.

Valine and isoleucine supplementation improve performance and serum biochemical concentrations in growing gilts fed low-protein diets

This study evaluated the effects of valine and isoleucine supplementation in low-crude-protein (CP) diets on performance, serum parameters, and carcass traits in growing gilts. Two-hundred gilts (29.1 ± 1.7 kg) were allotted randomly to one of five diets that included a control CP (177 g kg−1) or four low-CP (135 g kg−1) diets for 45 d. The low-CP diets were added with lysine + threonine + methionine (LCM), LCM+ tryptophan (LCT), LCT + valine (LCV), or LCV + isoleucine (LCI), respectively. Non significant difference in average daily gain was obtained in gilts receiving the control, LCV, or LCI diets, which was higher than that of pigs fed the LCM or LCT diets (P < 0.05). The supplementation of crystalline tryptophan, valine, and isoleucine improved the average daily feed intake and serum levels of total protein, tryptophan, and isoleucine (linear and quadratic effects, P < 0.05) and serum valine concentration (linear effect, P < 0.05). The results indicated that the valine supplementation, or the both combination of valine and isoleucine, could further improve the performance in 29–62 kg gilts fed the 135 g kg−1 CP diet.

Optimal dietary standardized ileal digestible lysine and crude protein concentration for growth and carcass performance in finishing pigs weighing greater than 100 kg1,2

Three experiments were conducted to determine the optimal dietary standardized ileal digestible (SID) lysine and CP concentrations for finishing pigs over 100 kg BW. In Exp. 1, 253 pigs (DNA 600 × 241, initially 102.0 kg) were used in a 23-d trial with 7 to 8 pigs per pen and 8 pens per treatment. Dietary treatments contained 4 SID lysine concentrations (0.45, 0.55, 0.65, or 0.75%). To formulate the experimental diets, a corn-soybean meal diet with 0.45% SID lysine was formulated without L-lysine HCl. Then, a corn-soybean meal diet containing 0.75% SID lysine was formulated including 0.23% L-lysine HCl. The 0.45 and 0.75% SID lysine diets were blended to provide the 0.55 and 0.65% SID lysine diets. Increasing SID lysine increased (quadratic, P < 0.05) ADG and ADFI with pigs fed 0.55% SID lysine having the greatest final BW. Marginal improvements in gain:feed (G:F; quadratic, P = 0.058) and carcass yield (linear, P = 0.051) and reduction in backfat (quadratic, P = 0.074) were also observed with increasing SID lysine. The quadratic polynomial models predicted maximum ADG and G:F at 0.62 and 0.63% SID lysine, respectively. The broken-line linear model predicted no further improvement in G:F over 0.55% SID lysine. In Exp. 2, 224 pigs (PIC 327 × 1050, initially 109.4 kg) were used in a 20-d trial with 7 pigs per pen and 7 to 8 pens per treatment. Dietary treatments included 4 concentrations of CP (10, 11, 12, or 13%) that were formed by reducing the amount of L-lysine HCl in a corn-soybean meal diet. Increasing CP increased (linear, P < 0.05) ADG and ADFI with the greatest responses observed in pigs fed the diet with 12% CP. Increasing dietary CP also improved (linear, P < 0.05) G:F, final BW, and hot carcass weight (HCW). In Exp. 3, 238 pigs (DNA 600 × 241, initially 111.8 kg) were used in a 26-d trial with 7 to 8 pigs and 6 pens per treatment. Dietary treatments included 5 concentrations of CP (9, 10, 11, 12, or 13%). Increasing CP improved (quadratic, P < 0.05) ADG and G:F with the greatest response observed in pigs fed 13% CP. Increasing CP marginally increased (quadratic, P < 0.074) HCW, with the greatest response observed in pigs fed 12% CP. In conclusion, the SID lysine requirement for pigs from 100 to 122 kg was 0.55 to 0.63% depending on the response criteria with performance maximized with diets containing 12 to 13% CP.

Effects of dietary supplementation with lysozyme during late gestation and lactation stage on the performance of sows and their offspring

This study investigated the effects of supplementing sow diets with lysozyme during the late gestation to lactation stage on the performance of sows and their offspring. Sixty sows (Yorkshire × Landrace, 3 to 6 of parity) at day 85 of gestation were allocated to the following 3 dietary treatments: 1) sows fed a basal diet from late gestation to lactation (control, n = 20), 2) sows fed a basal diet with lysozyme 150 g/t (LZM 150, n = 20), and 3) sows fed a basal diet with lysozyme 300 g/t (LZM 300, n = 20). During the lactation period, sows fed diets containing lysozyme had increased average daily feed intake (ADFI) (P < 0.01) and decreased weaning-to-estrus interval (WEI, P < 0.05), but there were no significant effects on backfat during the trial among treatments. Sows fed lysozyme diets had increased (P < 0.05) serum concentration of total protein (TP) compared with those fed the control diets. Serum immunoglobulin M (IgM) of the sows increased (P < 0.05) on day 1 of lactation, immunoglobulin A (IgA) and interleukin-10 (IL-10) increased (P < 0.05) on day 7 of lactation, and immunoglobulin G (IgG) had a tendency to increase (P = 0.05) during the lactation. Milk concentration of IgA increased (P < 0.05) on day 1 and 7 of lactation and tended to be greater (P = 0.06) on day 21 of lactation. No significant differences among the dietary treatments were observed in placental tissue mRNA expression of interleukin-6 (IL-6), IL-10, tumor necrosis factor-α (TNF-α), polymeric immunoglobulin receptor (pIgR), or the concentrations of IL-6, IL-10, TNF-α, or secretory immunoglobulin A (sIgA). Moreover, there was a decrease (P < 0.05) in stillborn in sows fed lysozyme diets. The diarrhea rate decreased (P < 0.05) and serum concentrations of IgA, IgG, IgM, and IL-10 increased (P < 0.05) in piglets from sows fed the diets containing lysozyme compared with piglets from sows fed the control diet. The serum concentrations of TP increased (P < 0.05), and albumin (ALB) and globulin (GLB) had a tendency to increase (P = 0.08, P = 0.06) in piglets from sows fed the diets containing lysozyme compared with piglets from sows fed the control diet. In conclusion, this study indicates that feeding sows diets supplemented with lysozyme from the late gestation through lactation stage increased sow ADFI during the lactation, shortened the WEI, and improved the maternal and offspring health status as indicated by immunological characteristics and a reduced incidence of diarrhea in piglets.

Influence of low-protein diets and protease and bromelain supplementation on growth performance, nutrient digestibility, blood urine nitrogen, creatinine, and faecal noxious gas in growing–finishing pigs

A total of 180 crossbred pigs [(Landrace × Yorkshire) × Duroc] with an average body weight of 22.61 ± 1.23 kg were used in an 18 wk study to determine the effect of protease and bromelain in low-protein diets in grower–finisher pigs. Dietary treatments included: T1, basal diet treatment; T2, low-protein treatment; T3 (T2 + 0.2 g kg−1 protease); and T4 (T2 + 0.3 g kg−1 bromelain). Pigs fed protease- and bromelain-supplemented diets increased average daily gain and gain to feed ratio at week 18, dry matter and nitrogen digestibility at week 6, as well as energy digestibility at week 12, compared with low-protein diet (P < 0.05). Pigs fed T3 and T4 diets led to a trend of decreased (P < 0.05) blood urine nitrogen (BUN) and creatinine concentrations at the 12th wk. A reduction of ammonia (NH3) and hydrogen sulfide (H2S) emission was observed in pigs fed the dietary protease and bromelain supplementation at the 6th wk (P < 0.05). There was no effect on all parameters between the protease and bromelain supplementation treatments. In conclusion, supplementation of protease and bromelain to low-protein diet enhanced growth performance, nutrient digestibility, and reduced NH3 and H2S in growing–finishing pigs.

Low-protein diet improves meat quality of growing and finishing pigs through changing lipid metabolism, fiber characteristics, and free amino acid profile of the muscle

The objective of the study was to investigate the effect of feeding reduced CP, AA-supplemented diets on meat quality in growing and finishing pigs as well as the related mechanism. In experiment 1, 18 growing pigs (36.5 kg BW) were assigned randomly and fed 1 of 3 corn-soybean meal diets containing either 18% CP (normal protein, NP), 15% CP (low protein, LP), or 12% CP (very low protein, VLP). In experiment 2, 18 finishing pigs (62.3 kg BW) were allotted randomly into 1 of the following diets: 16% CP (NP), 13% CP (LP), or 10% CP (VLP). In both experiments, the LP and VLP diets were supplemented with crystalline AA to achieve equal content of standardized ileal digestible lysine, methionine, threonine, and tryptophan. At the end of each experiment, all pigs were slaughtered to collect longissimus dorsi muscle (LM) samples. Samples were used for determining meat quality, intramuscular fat (IMF) content, fatty acid composition, free AA profile, and expression of genes for myosin heavy chain isoforms. Results showed that growing and finishing pigs fed the LP diets increased (P < 0.05) redness value of LM, while finishing pigs fed the LP and VLP diets decreased (P < 0.05) the shear force values. Compared with the NP diet, growing and finishing pigs fed lower CP diets had higher (P < 0.05) contents of IMF and MUFA, and lower (P < 0.05) contents of PUFA. Besides, higher (P < 0.05) expression levels of type I and/or IIa muscle fibers were observed in LP diet-fed growing and finishing pigs, and greater concentrations of taurine and tasty AA in VLP diet-fed growing and finishing pigs. Taken together, our results indicate that low-protein diets could positively affect meat quality of growing and finishing pigs, and likely through regulation of IMF content and fatty acid composition, fiber characteristics, and free AA profile in the muscle.

Blood parameters in fattening pigs from two genetic types fed diet with three different protein concentrations

The study aimed to evaluate possible differences between two genetic groups (GG) of pigs, fed diets varying in dietary CP level, in hematological and biochemical plasma profiles. The study was carried out in an experimental farm and involved 36 barrows (average BW 129 ± 11 kg) from two GG: group A (18 Italian Duroc boars × Italian Large White sows) and group D (18 DanBred Duroc), fed three experimental diets: a conventional diet and two low-protein diets (LP1 and LP2). A digestibility/balances trial was carried out on 12 pigs A and 12 pigs D that were housed individually in metabolic cages during four digestibility/balances periods. The experimental design was a factorial design, with 3 diets × 2 GG × 4 periods. The experiment lasted 56 d. Blood was sampled from jugular vein in the morning before feed distribution from all barrows in pens at the start and the end of the experimental period; a supplementary blood sample was collected from the 24 pigs at the end of the four digestibility periods (six pigs per period). Blood was analyzed for hematological and biochemical parameters and serum protein profile using automated analyzers. The GG D showed lower white blood cells (WBC), lymphocyte, and monocyte counts than A group. The GG affected several plasma metabolite concentrations: triglycerides, creatinine, Cl, Fe, alkaline phosphatase, and tartrate-resistant acid phosphatase activities were higher in D groups, while urea, albumin, Ca, Na, total bilirubin, and albumin as percentage of total protein were lower than A group. On the contrary, the dietary protein level neither affects WBC nor their populations; only a trend was reported for erythrocytes (red blood cell) and platelets. The diet affected only plasma urea and total bilirubin concentrations.

Effects of reducing dietary crude protein levels and replacement with crystalline amino acids on growth performance, carcass composition, and fresh pork quality of finishing pigs fed ractopamine hydrochloride

Progeny of GPK-35 females mated to PIC 380 boars were blocked by initial BW, and within the 9 blocks, pens of pigs (3 gilts and 3 barrows/pen) were randomly assigned to dietary treatments where CP of finisher-I, -II, and -III diets was 1) 16.04, 14.55, and 16.23%, respectively (Ctrl); 2) 14.76, 13.48, and 15.27%, respectively (ILE); 3) 14.26, 12.78, and 14.28%, respectively (VAL); or 4) 12.65, 12.38, and 13.32%, respectively (NoSBM). All finisher-III diets included 10 mg/kg of ractopamine hydrochloride (RAC) and a Lys:ME ratio of 2.79 g/Mcal. At slaughter, HCW and Fat-O-Meat'er data were recorded before carcasses were subjected to a rapid chilling process. A subsample of whole hams (2/pen) and whole loins (2/pen) were transported under refrigeration to the University of Arkansas. Hams were dissected with a knife into lean, fat, and bone, and 2.5-cm-thick chops from the semimembranosus (SM) and the LM were used to measure fresh pork quality characteristics. Both ADG and G:F decreased (linear, = 0.05) as CP decreased in finisher-I diets, whereas ADFI was reduced (linear, = 0.01) in response to decreasing CP in finisher-II diets. When RAC was included in the finisher-III diets, ADFI and BW decreased (linear, ≤ 0.03) with decreasing CP, and pigs fed the ILE diet had greater (cubic, < 0.01) G:F than pigs fed the Ctrl and VAL diets. Across the entire finishing period, ADG and ADFI decreased (linear, = 0.01) in response to reductions in dietary CP. Conversely, reducing CP in finisher diets did not ( ≥ 0.13) affect carcass yield, fat depth, LM depth, or calculated fat-free lean yield, and dietary CP content did not ( ≥ 0.09) alter the lean, fat, or bone composition of fresh hams. Moreover, there was no effect of dietary CP on the visual and instrumental color or firmness of the LM ( ≥ 0.06) or SM ( ≥ 0.12). However, there were linear increases in LM marbling scores ( = 0.02) and intramuscular fat content ( = 0.03) as CP was reduced in the finisher diets. Although reducing dietary CP decreased overall ADG and ADFI by approximately 6.1 and 4.9%, respectively, carcass composition was not impacted by dietary CP level. More importantly, reducing dietary CP, although meeting the standard ileal digestible requirements for Lys, Thr, Trp, Met, Ile, and Val with crystalline AA, did not impact pork color or water-holding capacity and actually increased the intramuscular fat content of the LM.

Protein-Restricted Diet Regulates Lipid and Energy Metabolism in Skeletal Muscle of Growing Pigs

The aim of this work was to study the lipid metabolism and energy status of skeletal muscle of pigs as affected by dietary protein restriction. Eighteen growing pigs were distributed into three treatments, and each group was fed one of three levels (20, 17, and 14%) of crude protein (CP) diets. Our results showed that pigs fed the 20% CP had greater (P < 0.05) gain:feed and muscle weight than those fed the 14% CP, but no differences between the 20 and 17% CP treatments. Additionally, protein restriction tended to increase (P = 0.07) the content of intramuscular fat (IMF) and up-regulated (P < 0.05) expression of lipogenic-related genes. Energy status was changed and, concomitantly, AMP-activated protein kinase α pathway was inhibited by reducing the dietary protein level. These results indicate protein restriction could be useful to improve IMF content of pigs through regulating lipid metabolism and associated energy utilization in muscle.

A proteomic adaptation of small intestinal mucosa in response to dietary protein limitation

Dietary protein limitation (PL) is not only beneficial to human health but also applied to minimize nitrogen excretion in livestock production. However, the impact of PL on intestinal physiology is largely unknown. In this study, we identified 5275 quantitative proteins using a porcine model in which pigs suffered PL. A total of 202 proteins |log₂ fold-change| > 1 were taken as differentially expressed proteins and subjected to functional and pathway enrichment analysis to reveal proteomic alterations of the jejunal mucosa. Combining with the results of western blotting analysis, we found that protein/carbohydrate digestion, intestinal mucosal tight junction and cell adhesion molecules, and the immune response to foreign antigens were increased in the jejunal mucosa of the pigs upon PL. In contrast, amino acid transport, innate and auto immunity, as well as cell proliferation and apoptosis were reduced. In addition, the expression of functional proteins that involved in DNA replication, transcription and mRNA splicing as well as translation were altered in the jejunal mucosa in response to PL. Furthermore, PL may reduce amino acid transport and cell proliferation through the depression of mTOR pathway. This study provides new insights into the molecular mechanisms underlying the small intestinal response to PL.

Restriction of dietary protein does not promote hepatic lipogenesis in lean or fatty pigs

The influence of genotype (lean v. fatty) and dietary protein level (normal v. reduced) on plasma metabolites, hepatic fatty acid composition and mRNA levels of lipid-sensitive factors is reported for the first time, using the pig as an experimental model. The experiment was conducted on forty entire male pigs (twenty lean pigs of Large White×Landrace×Pietrain cross-breed and twenty fatty pigs of Alentejana purebreed) from 60 to 93 kg of live weight. Each pig genotype was divided into two subgroups, which were fed the following diets: a normal protein diet (NPD) equilibrated for lysine (17·5 % crude protein and 0·7 % lysine) and a reduced protein diet (RPD) not equilibrated for lysine (13·1 % crude protein and 0·4 % lysine). The majority of plasma metabolites were affected by genotype, with lean pigs having higher contents of lipids, whereas fatty pigs presented higher insulin, leptin and urea levels. RPD increased plasma TAG, free fatty acids and VLDL-cholesterol compared with NPD. Hepatic total lipids were higher in fatty pigs than in the lean genotype. RPD affected hepatic fatty acid composition but had a slight influence on gene expression levels in the liver. Sterol regulatory element-binding factor 1 was down-regulated by RPD, and fatty acid desaturase 1 (FADS1) and fatty acid binding protein 4 (FABP4) were affected by the interaction between genotype and diet. In pigs fed RPD, FADS1 was up-regulated in the lean genotype, whereas FABP4 increased in the fatty genotype. Although there is a genotype-specific effect of dietary protein restriction on hepatic lipid metabolism, lipogenesis is not promoted in the liver of lean or fatty pigs.

Effects of Dietary Crude Protein Levels and Cysteamine Supplementation on Protein Synthetic and Degradative Signaling in Skeletal Muscle of Finishing Pigs

Dietary protein levels and cysteamine (CS) supplementation can affect growth performance and protein metabolism of pigs. However, the influence of dietary protein intake on the growth response of CS-treated pigs is unclear, and the mechanisms involved in protein metabolism remain unknown. Hence, we investigated the interactions between dietary protein levels and CS supplementation and the effects of dietary crude protein levels and CS supplementation on protein synthetic and degradative signaling in skeletal muscle of finishing pigs. One hundred twenty barrows (65.84 ± 0.61 kg) were allocated to a 2 × 2 factorial arrangement with five replicates of six pigs each. The primary variations were dietary crude protein (CP) levels (14% or 10%) and CS supplemental levels (0 or 700 mg/kg). The low-protein (LP) diets (10% CP) were supplemented with enough essential amino acids (EAA) to meet the NRC AA requirements of pigs and maintain the balanced supply of eight EAA including lysine, methionine, threonine, tryptophan, valine, phenylalanine, isoleucine, and leucine. After 41 days, 10 pigs per treatment were slaughtered. We found that LP diets supplemented with EAA resulted in decreased concentrations of plasma somatostatin (SS) (P<0.01) and plasma urea nitrogen (PUN) (P<0.001), while dietary protein levels did not affect other traits. However, CS supplementation increased the average daily gain (P<0.001) and lean percentage (P<0.05), and decreased the feed conversion ratio (P<0.05) and back fat (P<0.05). CS supplementation also increased the concentrations of plasma insulin-like growth factor 1 (IGF-1) (P<0.001), and reduced the concentrations of leptin, SS, and PUN (P<0.001). Increased mRNA abundance of Akt1 and IGF-1 signaling (P<0.001) and decreased mRNA abundance of Forkhead Box O (FOXO) 4 (P<0.01) and muscle atrophy F-box (P<0.001) were observed in pigs receiving CS. Additionally, CS supplementation increased the protein levels for the phosphorylated mammalian target of rapamycin (mTOR), eIF-4E binding protein 1, and ribosomal protein S6 kinase 1 (P<0.001). There were no interactions between dietary protein levels and CS supplementation for all traits. In conclusion, dietary protein levels and CS supplementation influenced growth and protein metabolism through independent mechanisms in pigs. In addition, LP diets supplemented with EAA did not affect growth performance and other traits except the concentrations of SS and PUN probably through maintenance of protein synthesis and degradation signaling. Moreover, CS supplementation improved growth performance by increasing plasma IGF-1 concentrations possibly through alterations of mTOR and Akt/FOXO signaling pathways in skeletal muscle of finishing pigs.

Amino acids modulates the intestinal proteome associated with immune and stress response in weaning pig

The objective of this study was to investigate the effects of free amino acids supplementation to protein restricted diet on the intestinal morphology and proteome composition in weaning pigs. Weanling piglets were randomly fed one of the three diets including a corn-soybean based control diet and two lower protein diets with or without free amino acids supplementation for 2 weeks. The jejunum samples of piglets were collected for morphology and proteome analysis. Compared with the control diet, the protein restricted diet had a significant lower average daily gain and higher feed conversion rate. Free amino acids supplementation to the protein restricted diet significantly improved average daily gain and higher feed conversion rate, compared with the protein restricted diet. The villous height in pigs fed the protein restricted diet was lower than that of the control and free amino acids diet. Using two-dimensional gel electrophoresis and mass spectrometry, we identified 16 differentially expressed protein spots in the jejunum of the weaning piglet. These proteins were related to stress and immune response, the metabolism of carbohydrates and lipids, and tissue structure. Based on the proteome and ELISA analysis, free amino acids diet significantly down-regulated the jejunal expression of stress protein heat shock 60 kDa protein. Our results indicated that amino acids supplementation to the protein restricted diet could enhance weight gain and feed efficiency in weanling pigs through improving intestinal nutrient absorption and transportation, gut health, and mucosal immunity.

Utilization of crystalline or protein-bound lysine for growth and carcass traits of barrows and gilts fed individually or in groups

An experiment consisting of two 4-wk trials was conducted to determine Lys use for growth and carcass traits in barrows and gilts fed individually or in groups. One hundred twelve growing pigs (56 barrows and 56 gilts; average initial BW of 18.6 kg) were used in each trial. Pigs were fed individually or in groups of 3. There were 28 pigs individually penned, and 84 pigs in 28 pens (3 pigs/pen). There were 2 replications per treatment in each trial for a total of 4 replications. Dietary treatments consisted of a corn-soybean meal (SBM) basal diet (0.48% Lys) and diets containing 0.56%, 0.65%, and 0.74% standardized ileal digestible (SID) Lys that were achieved by adding Lys to the basal diet from either SBM or crystalline source as L-Lys HCL (CLys). At the end of each trial, all pigs were scanned using real-time ultrasound to determine 10th-rib back fat depth and LM area, and fat-free lean gain (FFLG) was calculated. Blood samples were taken from all pigs weekly to determine plasma urea N (PUN). Pigs fed CLys and Lys from SBM were not different in final BW, ADG, ADFI, or G:F. The ADG and G:F increased linearly (P < 0.01) as dietary Lys concentration increased. The SID Lys intake increased linearly (P < 0.01) as dietary Lys concentration increased and was not different when comparing pigs fed diets with CLys or SBM. The amount of SID Lys required per unit of growth or BW gain increased linearly (about 13 to 15.50 g/kg) in pigs fed either CLys or SBM Lys. Pigs fed individually had a greater (P < 0.05) ADG (0.59 vs. 0.57 kg) and ADFI (1.36 vs. 1.29 kg) than pigs fed in groups. The SID Lys intake was greater (P < 0.05) in pigs fed individually in comparison with pigs fed in a group (8.51 vs. 8.06 g/d). Fat-free lean gain and LM area increased (P < 0.01) as dietary Lys concentration increased regardless of Lys source. Pigs fed CLys diets had a greater (P < 0.05) LM area than pigs fed SBM at 0.74% SID Lys. Gilts had a greater (P < 0.01) LM area (14.28 vs. 13.58 cm(2)) and FFLG (264 vs. 245 g/d) than barrows. Pigs fed individually with CLys had less (P < 0.01) PUN than pigs fed Lys from SBM. Barrows fed individually had less (sex × feeding method, P < 0.01) PUN than gilts (26.75 vs. 29.32 g/100 mL). The results indicate that Lys from SBM-bound and CLys source were utilized similarly for growth and carcass traits regardless of sex or feeding method.

Effects of low protein diets on growth performance, carcass traits and ammonia emission of barrows and gilts

The aim of the present research was to determine the effect of low protein diets on growth performance, carcass traits and ammonia emission from barrows and gilts during the growing and finishing periods. For each period, three diets were formulated. A control diet (C) with 160 and 155 g crude protein (CP)/kg for the growing and finishing, respectively, a medium level diet (M) and a low level diet (L) with 10 and 20 g CP/kg less than the C, respectively. All the diets were supplemented with crystalline amino acids on an ideal protein basis. Barrows (90) and gilts (90) were sorted by bodyweight and sex and housed in three identical manually ventilated chambers. No significant effects of diet on pig performance were observed. In the finishing period, barrows were heavier (P < 0.001) and had higher average daily gain (P < 0.01) and average daily feed intake (P < 0.01) than gilts. Pigs fed the L diet had higher backfat thickness than those fed the other diets in the growing period (P < 0.05). Backfat thickness was higher (P < 0.01) in barrows than in gilts. Muscle depth decreased in pigs fed the L diet in the finishing period. Muscle depth was not affected (P > 0.05) by sex. Average ammonia emissions during the last 6 days were 117.7, 94.2 and 85.5 mg ammonia/kg pig.day for pigs fed the C, M and L diets, respectively. The results show that a reduction in dietary CP of 10 g/kg, accompanied by supplementation with crystalline amino acid reduced ammonia emission by 19.9% with no detrimental effects on growth performance and carcass characteristics, and a reduction of 20 g/kg reduced ammonia emission by 27.3% with no detrimental effects on growth performance but reduced muscle depth at slaughter.

Impact of dietary protein on lipid metabolism-related gene expression in porcine adipose tissue

BACKGROUND

High dietary protein can reduce fat deposition in animal subcutaneous adipose tissue, but little is known about the mechanism.

METHODS

Sixty Wujin pigs of about 15 kg weight were fed either high protein (HP: 18%) or low protein (LP: 14%) diets, and slaughtered at body weights of 30, 60 or 100 kg. Bloods were collected to measure serum parameters. Subcutaneous adipose tissues were sampled for determination of adipocyte size, protein content, lipid metabolism-related gene expression, and enzyme activities.

RESULTS

HP significantly reduced adipocyte size, fat meat percentage and backfat thickness, but significantly increased daily gain, lean meat percentage and loin eye area at 60 and 100 kg. Serum free fatty acid and triglyceride concentrations in the HP group were significantly higher than in the LP group. Serum glucose and insulin concentrations were not significantly affected by dietary protein at any body weight. HP significantly reduced gene expression of acetyl CoA carboxylase (ACC), fatty acid synthase (FAS) and sterol regulatory element binding protein 1c (SREBP-1c) at 60 kg and 100 kg; however, the mRNA level and enzyme activity of FAS were increased at 30 kg. HP promoted gene and protein expression and enzyme activities of lipoprotein lipase (LPL), carmitine palmtoyltransferase-1B (CPT-1B), peroxisome proliferator-activated receptor gamma (PPARgamma) and adipocyte-fatty acid binding proteins (A-FABP) at 60 kg, but reduced their expression at 100 kg.Gene expression and enzyme activity of hormone sensitive lipase (HSL) was reduced markedly at 60 kg but increased at 100 kg by the high dietary protein. Levels of mRNA, enzyme activities and protein expression of ACC, FAS, SREBP-1c and PPARgamma in both LP and HP groups increased with increasing body weight. However, gene and protein expression levels/enzyme activities of LPL, CPT-1B, A-FABP and HSL in both groups were higher at 60 kg than at 30 and 100 kg.

CONCLUSION

Fat deposition in Wujin pigs fed high dietary protein for 25 weeks was reduced mainly by depression of lipogenic gene expression. The mechanism of lipid transport, lipolysis and oxidation in adipose tissue regulated by dietary protein appeared to be different at 60 kg and 100 kg body weights.

Muscle growth and plasma concentrations of amino acids, insulin-like growth factor-I, and insulin in growing pigs fed reduced-protein diets

Twenty barrows were used to determine if partial replacement of protein-bound AA with crystalline AA (CAA) reduces AA use for muscle tissue and whole-body growth. Barrows (44.2 +/- 1.3 kg of BW) were assigned to 4 diets in a randomized complete block design. Diets consisted of 16.1% CP with no CAA, and 12.8, 10.1, and 7.8% CP containing CAA. As the CP concentration decreased, CAA were gradually increased to meet requirements on a true ileal digestibility basis. Barrows were weighed on d 0 and 13. Blood samples were collected before the morning feeding on d 0, 6, and 12 (prefeeding), and 2 h after the morning feeding on d 13 (postfeeding). Pigs were euthanized on d 13, and liver and right LM were removed and weighed. The reduction in the dietary CP concentration linearly decreased (P < 0.01) ADG, G:F, LM weight, and the CP content of LM. Reducing the CP concentration decreased pre- and postfeeding plasma concentrations of IGF-I (linear, P < 0.01) and insulin (linear, P < 0.10). The reduction in the dietary CP concentration increased prefeeding plasma concentrations of Ala, Gln, Gly, and total AA but decreased Arg, Asn, His, Ile, Phe, Trp, and Tyr (linear, P < 0.05). Plasma concentration of total indispensable AA decreased initially and increased thereafter as the dietary CP concentration decreased from 16.1 to 7.8% (quadratic, P < 0.01). The reduction in the dietary CP concentration increased postfeeding plasma concentrations of Ala, Lys, Met (linear, P < 0.01), and Gly (linear, P = 0.073) and decreased Asn, Ser, Tyr, Arg, His, and Leu (linear, P < 0.05). Plasma concentrations of Ile, Phe, Thr, Trp, and Val decreased initially and increased thereafter as the dietary CP concentration decreased from 16.1 to 7.8% (quadratic, P < 0.05). In muscle tissue, concentrations of free Ala, Asp, Glu, Gln, Gly, and Lys increased (linear, P < 0.05) as the dietary CP concentration decreased. Concentrations of free His, Ile, Phe, Thr, Trp, and Val in muscle tissue decreased initially and increased thereafter as the dietary CP concentration decreased from 16.1 to 7.8% (quadratic, P < 0.05). In summary, the reduction in the dietary protein-bound AA decreased whole-body and LM growth, altered the free AA pool profile in muscle tissue, and decreased plasma insulin and IGF-I. As the replacement of protein-bound AA with CAA increased, 1) free Ala and Gln in muscle tissue increased, indicating an increase of muscle tissue protein breakdown; and 2) utilization of indispensable AA in muscle tissue decreased.

Nitrogen excretion and ammonia emissions from pigs fed modified diets

Two swine feeding trials were conducted (initial body weight = 47 +/- 2 and 41 +/- 3 kg for Trials 1 and 2, respectively) to evaluate reduced crude protein (CP) and yucca (Yucca schidigera Roezl ex Ortgies) extract-supplemented diets on NH3 emissions. In Trial 1, nine pigs were offered a corn-soybean meal diet (C, 174 g kg(-1) CP), a Lys-supplemented diet (L, 170 g kg(-1) CP), or a 145 g kg(-1) CP diet supplemented with Lys, Met, Thr, and Trp (LMTT). In Trial 2, nine pigs were fed diet L supplemented with 0, 62.5, or 125 mg of yucca extract per kg diet. Each feeding period consisted of a 4-d dietary adjustment followed by 72 h of continuous NH3 measurement. Urine and fecal samples were collected each period. Feeding the LMTT diet reduced (P < 0.05) average daily gain (ADG) and feed efficiency (G:F) compared to diet L. Fecal N concentration decreased with a reduction in dietary CP, but urinary ammonium increased from pigs fed diet LMTT (2.0 g kg(-1), wet basis) compared to those fed diet C (1.1 g kg(-1)) or L (1.0 g kg(-1)). When pigs were fed reduced CP diets NH3 emission rates decreased (2.46, 2.16, and 1.05 mg min(-1) for diets C, L, and LMTT). Yucca had no effect on feed intake, ADG, or G:F. Ammonium and N concentrations of manure and NH3 emission rates did not differ with yucca content. Caution must be executed to maintain animal performance when strategies are implemented to reduce NH3 emissions.

Biochemical and morphological developments are partially impaired in intestinal mucosa from growing pigs fed reduced-protein diets supplemented with crystalline amino acids1

The objective of this study was to determine if a reduction in dietary CP, with partial replacement of the intact protein with crystalline AA (CAA), would alter growth, morphology, and free or peptide-bound AA concentrations of intestinal mucosa in growing pigs. Twenty-four barrows (37.0 +/- 1.5 kg of BW) were fed 1 of 4 diets for 24 d: 16.1% CP with no CAA, or 12.8, 10.1, or 7.8% CP (analyzed values, as-fed) containing CAA. As CP decreased, CAA were gradually increased to meet requirements on a true ileal digestible basis. Pigs were euthanized 2 h postmeal on d 24, and mucosal samples from duodenum, jejunum, and ileum were collected. Reducing dietary CP decreased ADG, G:F, and final weight (linear, P < 0.05). With reduced dietary CP, mucosal protein concentration decreased in the jejunum (quadratic, P < 0.05) and tended to decrease in the ileum (linear, P = 0.062). Reduction of the dietary CP concentration from 16.1 to 7.8% tended to decrease the crypt depth (linear, P < 0.10) and decreased villus width (linear, P < 0.05) in duodenum and jejunum mucosa but did not reduce villus height or villus surface area in any regions of the small intestine. In the duodenum, a reduction in dietary CP increased free Lys, Met, and Thr (linear, P < 0.05) and peptide-bound Lys and Thr (quadratic, P < 0.10). In the jejunum, reducing CP decreased free Cys (linear P < 0.05) and tended to decrease free Asn and His (linear, P < 0.10) and peptide-bound His (quadratic, P = 0.061) and Ile, Leu, and Val (linear, P < 0.10). In the ileum, reducing CP decreased free Asn, Ser, Tyr, Arg, His, Phe (linear, P < 0.05), and Leu (linear, P = 0.054) and peptide-bound Gly and Ser (linear, P < 0.05) and tended to decrease peptide-bound Ile, Leu, Phe, Val (linear, P < 0.10), and Lys (linear P < 0.05). In conclusion, reduced-CP diets supplemented with CAA lead to a reduction in growth performance, associated with biochemical and morphological modifications of the intestinal mucosa.

Nitrogen metabolism and growth performance of gilts fed standard corn-soybean meal diets or low-crude protein, amino acid-supplemented diets

Two experiments were conducted to determine the CP concentration below which N retention and growth performance are reduced when low-protein, amino acid-supplemented, corn-soybean meal diets are fed. In a N balance trial (Exp. 1), 12 gilts (initial weight 41 kg) were fitted with urinary catheters and fed six different diets during three 7-d periods in an incomplete block design. The diets were: 1) 18% CP; 2) 14% CP + AA, 3) 16% CP; 4) 12% CP + AA; 5) 14% CP; and 6) 10% CP + AA. Amino acids (lysine, threonine, tryptophan, and methionine) were supplemented such that the concentrations in the low-protein diets were equal to those in their standard (4% CP higher) counterparts. Nitrogen retention (g/d) decreased (P < 0.01) as CP decreased, in both standard (27.10, 24.53, and 20.99) and low-protein (21.51, 19.18, and 15.83) diets, but was lower (P < 0.01) in low-protein diets. There were no differences among treatments (P > 0.05) in biological value (68.2% standard vs 71.0% low-protein). In a growth performance trial (Exp. 2), 36 gilts (initial weight 19.5 kg) were penned individually and fed one of six diets for 35 d in a randomized complete block design. Dietary treatments were a 16% CP standard diet and low-protein diets formulated to contain 15, 14, 13, 12, and 11% CP supplemented with crystalline lysine, tryptophan, threonine, and methionine to equal the total concentrations in the standard diet. Protein concentration affected (P < or = 0.05) ADG, ADFI, feed efficiency, fat-free lean gain, longissimus muscle area, plasma urea, and plasma concentrations of most essential AA. For most of these traits, the major difference was poor performance of pigs fed the 11% CP diet. Thus, in Exp. 1, at AA concentrations from deficient to excess, low-protein, amino acid-supplemented diets failed to produce the same N retention as the equivalent corn-soybean meal diets. However in Exp. 2, the same performance was obtained with 16, 15, 14, 13, and 12% CP. Based on these data, we suggest that N balance is more sensitive than growth to amino acid adequacy andthat other AA (e.g., isoleucine and valine) may limit growth performance when the protein concentration is reduced by more than four percentage units.