C. L. Levesque

Immune system stimulation reduces the efficiency of tryptophan utilization for body protein deposition in growing pigs

The effect of immune system stimulation (ISS) on N retention and Trp utilization in pigs fed Trp-limiting diets was evaluated using 36 growing pigs (20.0 ± 1.1 kg BW; 3 blocks of 12 barrows). Pigs were randomly assigned to 1 of 5 diets (Diet 1, 2, 4, and 5, n = 7; Diet 3, n = 8) and fed restrictively at 800 g/d. Diets 1 to 4 were generated by blending Diet 1 with a protein-free supplement and were calculated to contain varying amounts of standardized ileal digestible (SID) Trp (1.31, 1.05, 0.80, and 0.55 g/kg). To confirm that Trp was the first-limiting AA in Diets 1 to 4, an additional diet was used (Diet 5), which was equivalent to Diet 4 and contained 0.34 g/kg of added Trp. After a 5-d adaptation period, pigs were injected every 2 d with increasing amounts of E. coli lipopolysaccharide to induce ISS (initial dose 20 μg/kg BW, increasing 15% each subsequent injection). Whole body N balance was measured in 3 periods: before immune stimulation (pre-ISS) and during ISS in 2 subsequent periods (ISS-1, 3 d; ISS-2, 4 d). Regression analysis was used to estimate the marginal efficiency of Trp utilization for whole body protein deposition (PD; N retention × 6.25). Plasma concentrations of acute-phase proteins and white blood cell counts increased (P < 0.001) and plasma albumin decreased (P < 0.001) during ISS. Nitrogen retention increased (P < 0.001) as Trp intake increased. Nitrogen retention was numerically greater but not statistically different between Diet 5 (added Trp diet) and Diet 4. Whole body N retention was less (P < 0.05) during ISS due primarily to an increase (P < 0.05) in urinary N excretion. There was a linear response (P < 0.05) in N retention, urinary N, and total excreted N to increasing Trp intake. Protein deposition increased by 88.2 ± 5.2, 82.5 ± 5.1, and 92.5 ± 3.4 g/d for each additional g/d of SID Trp intake during pre-ISS, ISS-1, and ISS-2, respectively, but the intercept was not different (-32.3 g/d). The slope of the response of PD to increasing Trp intake (based on the common intercept) was less during ISS-1 compared with pre-ISS (P = 0.01) or ISS-2 (P = 0.002) but not different between pre-ISS and ISS-2. Immune system stimulation reduced N retention in pigs fed limiting dietary Trp. The efficiency of Trp utilization for protein deposition was also reduced during ISS, indicating that the Trp requirement for PD is increased ∼7% during an inflammatory state.

The threonine requirement of sows increases in late gestation

Current AA recommendations for sows are to provide a fixed amount of AA intake throughout gestation based on the assumption that there is a constant demand for AA; however, the demand for nutrients changes from maternal lean tissue in early gestation to fetal and mammary growth in late gestation. The objective of this study was to determine the Thr requirement in early (d 35 to 53 and 25 to 55 for Exp. 1 and 2, respectively) and late (d 92 to 110 and 81 to 111 for Exp. 1 and 2, respectively) gestation using the indicator AA oxidation (IAAO) method with l-[1-(13)C]Phe as the tracer AA. A total of 14 multiparous sows were used: 6 in Exp. 1 and 8 in Exp. 2. Each sow received each of 6 diets in random order in both early and late gestation. A basal diet was formulated to contain Thr at 60% of the 1998 NRC recommendation in Exp. 1 and 20 and 60% of the 1998 NRC in Exp. 2 for early and late gestation, respectively. Crystalline l-Thr was added to create additional diets with approximately 10% incremental increases in Thr. Sows were placed in respiration chambers, and expired air and blood were collected every 30 min for 5.5 h. Tracer Phe [mg/(kg of BW·h)] was given orally over the last 4 h divided into eight 0.5-h meals. Expired air and plasma were measured for (13)CO(2) enrichment and free Thr concentration, respectively. Background (13)CO(2) was subtracted from plateau (13)CO(2) enrichment. Data were analyzed using a 2-phase nonlinear Mixed model. The overall litter size and litter weight were 13.5 ± 3.1 and 20.5 ± 3.9 kg, respectively. Based on IAAO, the Thr requirement in early gestation was 6.1 g/d (R(2) = 0.59, Exp. 1) and 5.0 g/d (R(2) = 0.71, Exp. 2). In late gestation, the Thr requirement based on IAAO was 13.6 g/d (R(2) = 0.60, Exp. 1) and 12.3 g/d (R(2) = 0.58, Exp. 2). Based on plasma Thr, the Thr requirement in early gestation was 7.0 g/d (R(2) = 0.90, Exp. 1) and 3.9 g/d (R(2) = 0.90, Exp. 2). In late gestation, the Thr requirement based on plasma Thr was 10.5 g/d (R(2) = 0.67, Exp. 2). There was a linear response to increasing Thr intake in late gestation in Exp. 1. Feeding a single amount of AA throughout gestation results in overfeeding AA in early gestation and underfeeding AA in late gestation. The 2-fold increase in Thr requirement in the last third of gestation suggests that phase feeding sows in gestation will more closely meet the demands for nutrients and that the requirement for essential AA in gestating sows should be re-evaluated in early and late gestation separately.

Available versus digestible amino acids – new stable isotope methods

The nutritive value of food protein sources is dependent on the amino acid composition and the bioavailability of the nutritionally indispensable amino acids. Traditionally the methods developed to determine amino acid bioavailability have focused on intestinal absorption or digestibility, which is calculated as the percent of amino acid intake that does not appear in digesta or faeces. Traditional digestibility based methods do not always account for gut endogenous amino acid losses or absorbed amino acids which are unavailable due to the effect of heat processing and the presence of anti-nutritional factors, though methods have been developed to address these issues. Furthermore, digestibility based methods require the use of animal models, thus there is a need to develop in vivo methods that can be applied directly in human subjects to identify the proportion of dietary amino acids which is bioavailable, or metabolically available to the body for protein synthesis following digestion and absorption. The indicator amino acid oxidation (IAAO) method developed in our laboratory for humans has been systematically applied to determine almost all indispensable amino acid requirements in adult humans. Oxidation of the indicator amino acid is inversely proportional to whole body protein synthesis and responds rapidly to changes in the bioavailability of amino acids for metabolic processes. Using the IAAO concept, we developed a new in vivo method in growing pigs, pregnant sows and adult humans to identify the metabolic availability of amino acids in foods. The stable isotope based metabolic availability method is suitable for rapid and routine analysis in humans, and can be used to integrate amino acid requirement data with dietary amino acid availability of foods.

Impact of nursery feeding program on subsequent growth performance, carcass quality, meat quality, and physical and chemical body composition of growing-finishing pigs

An experiment was conducted to examine the effect of the nursery feeding program on subsequent growth performance, carcass quality, meat quality, and physical and chemical body composition of growing-finishing pigs. Four dietary treatments were used in a 2 × 2 factorial arrangement of treatments based on diet complexity (Complex vs. Simple) and in-feed antibiotics (2,730 [+AB] vs. 0 [-AB] mg of chlortetracycline /kg].A total of 552 pigs, in 5 blocks, were weaned at 21 ± 2 d of age with an initial BW of 7.03 ± 0.07 kg. Each experimental block had 3 pens per treatment, with 8 pigs per pen in blocks 1 and 2, and 10 pigs per pen in the remaining 3 blocks. Nursery diets were fed in a 3-phase feeding program (Phase I, II, and III diets fed for 1, 2, and 3 wk, respectively). All pigs were fed common grower-finisher diets thereafter. Six pigs per treatment were slaughtered for chemical body composition analysis at wk 2, 8, 12, and 17 postweaning. An additional 11 pigs per treatment were slaughtered at wk 17 postweaning (approximately 115 kg BW or market weight) for analysis of carcass characteristics, chemical and physical body composition, and meat quality. During the nursery phase, ADG was lower (P < 0.05) for pigs fed the Simple diet than those fed the Complex diet (491 vs. 528 g/d). Antibiotic usage improved (P < 0.05) ADG in Phases II (408 vs. 438 g/d) and III (689 vs. 720 g/d). In Phase I and II, G:F was lower (P < 0.05) for pigs fed the Simple diet than those fed the Complex diet (0.46 vs. 0.58 and 0.75 vs. 0.78 in Phases I and II, respectively). During the grower phase, pigs previously fed -AB diets grew faster than pigs fed +AB diets (P < 0.05; 1,009 vs. 971 g/d). There were no treatment effects on overall ADG or G:F from weaning to finishing. Nursery feeding program did not affect carcass quality characteristics. However, pigs previously fed +AB diets tended (P = 0.07) to have increased LM depth. Nursery feeding program had no effect on objective or subjective meat quality measures, chemical body composition, or the weight of primal and retail carcass cuts at wk 17 postweaning, with the exception of primal belly weight. These results indicate that feeding simple nursery diets, or nursery diets without antibiotics, compromises growth performance during the nursery period but does not affect overall growth performance between weaning and market BW, carcass characteristics, and meat quality. Thus, feed costs for nursery pigs can be reduced by feeding simple diets without compromising market BW and carcass and meat quality.

Alterations in Ileal Mucosa Bacteria Related to Diet Complexity and Growth Performance in Young Pigs

Background Evaluation of the prolonged impact of weaning diet on ileal mucosa bacteria and during periods of reduced and improved growth was conducted using 454 pyrosequencing. Methodology/Principal Findings Weaned pigs were fed HIGH or LOW complexity diets, with or without antibiotics, for 6 weeks, followed by a common grower diet. Pigs were killed at 2 (n = 4 or 5) and 8 (n = 6) weeks post-weaning (periods of reduced and improved growth, respectively). Mucosal bacteria were removed; DNA was extracted and amplified using the V1–V3 region of the 16S rRNA gene. Mucosal bacteria clustered more closely by week post-weaning than diet but 44% of bacterial species did not change from week 2 to 8. There was no effect of diet complexity or antibiotic inclusion on indices of bacterial diversity. Firmicutes made up 91 and 96% of total reads at week 2 and 8, respectively. The proportion of Clostridium paraputrificum increased (P = 0.003) from week 2 to 8 in pigs fed LOW but didn’t change in pigs fed HIGH; whereas Clostridium leptum decreased (P = 0.02) from week 2 to 8 in pigs fed LOW but didn’t change in pigs fed HIGH. The proportion of Sarcina genus was 3-fold higher in pigs fed A+ compared to A− at week 2 and 5-fold higher at week 8 despite the lack of in-feed antibiotics at that time. Conclusions/Significance Shifts in mucosal bacteria populations may be related to dietary induced changes in growth performance during reduced and improved growth but further studies are required to confirm causative relationship. Weaning diet results in species specific prolonged alterations in mucosal bacteria, particularly where high levels of in-feed antibiotics are used. A considerable portion of ileal mucosal bacteria colonize early and remain stable over time despite changes in diet.

Ileal mucosa-associated--but not ileal digesta--bacterial profiles in grower pigs are influenced by nutrition and use of antibiotics for weaner pigs.

A longitudinal study was conducted in pigs to evaluate the effect of nutrition and use of antibiotics for weaner pigs on ileal bacterial microbiota. Forty-eight pigs were weaned at 21 ± 2 d of age and fed a high complexity diet (High) or low complexity diet (Low) with chlortetracycline (A+) or without chlortetracycline (A-) for 6 wk. All pigs received the same grower diet thereafter. Pigs were killed at week 2, 4, and 8 and ileal digesta as well as a 40-cm section of the distal ileum were taken for extraction of digesta and mucosa-associated bacteria, respectively. Total DNA was extracted using a commercially available kit and PCR amplicons were generated using HDA1-GC and HDA2 primers against the V3 region of the 16S rRNA gene. Denaturing gradient gel electrophoresis (DGGE) of PCR amplicons was used for separation of distinct bacteria communities. Similarities of PCR-DGGE profiles were analyzed with Bionumerics software and the degree of similarity represented by a similarity coefficient. The DNA bands were compared using a positional tolerance of 0.5%. In the digesta, HighA-, LowA+, and LowA- were 47.6, 63.6, and 58.8% similar, respectively, at week 2 and 64.0, 69.2, and 66.7% similar, respectively, at week 4. Digesta bacteria were 90.9 (HighA-) and 85.7% (LowA-) similar to HighA+ at week 8 but due to a smiling edge of the DGGE gel, the profile for LowA+ was deemed inappropriate for similarity analysis. In the mucosa, HighA-, LowA+, and LowA- were 58.8, 80.0 and 44.4% similar, respectively, compared to HighA+ at week 2; 81.5, 75.0, and 88.9% similar, respectively, at week 4; and 81.8, 76.2, and 78.3% similar, respectively, at week 8. The bacterial profile was more similar between weeks 2 and 4 in the digesta than in the mucosa but more similar between weeks 4 and 8 in the mucosa than in the digesta. Postweaning nutrition may have a long-term effect on ileal mucosa-associated--but not ileal digesta--microbiota profiles.

In a Neonatal Piglet Model of Intestinal Failure, Administration of Antibiotics and Lack of Enteral Nutrition Have a Greater Impact on Intestinal Microflora Than Surgical Resection Alone.

Background: Data are limited on how short bowel syndrome (SBS) affects the healthy developing intestinal microbiome, with even less assessing different SBS anatomical surgical models. This study was conducted to describe the “ileal” and “colonic” microflora in 2 surgical models of SBS. Materials and Methods: Neonatal piglets (2–5 days old) underwent intestinal resection, leaving the ileum (JI anatomy, n = 6) or removing the ileum and ileocecal valve (JC anatomy, n = 5), or sham surgery (sham; n = 4). JI, JC, and sham piglets commenced parenteral nutrition on day 0 and received ampicillin and trimethoprim-sulfadoxine on days 0–4 for prevention of line sepsis. At day 7, ileal and colonic digesta were collected, and they were also collected from age-matched sow-fed piglets (n = 6). DNA extraction, sequencing, and annotation followed standard procedures. Results: Colonic and ileal bacterial genus diversity and relative bacterial abundance were greater (P < .05) in sow-fed compared with JI, JC, and sham piglets; however, minor differences were observed in either location between sham, JI, and JC piglets and within the surgical model. In the colon, sow-fed piglets had higher (P < .05) abundance of Lactobacillus (26%) and tended to have lower (P = .06) abundance of Enterococcus (<.1%) than JI, JC, or sham piglets, in which Lactobacillus and Enterococcus abundance averaged <.1% and 9%, respectively. Conclusions: Intestinal resection reduces bacterial diversity in the large bowel, and the difference is associated with the presence/absence of the ileum and ileocecal valve. The lack of enteral nutrition and antibiotic administration (ie, sow-fed vs surgery) had a greater influence on the observed shift in diversity and relative abundance than intestinal resection.

Protein intake but not feed intake affects dietary energy for finishing pigs

The effects of dietary protein and feeding levels on dietary metabolizable (ME) and net energy (NE) content were determined in 24 pigs, each offered two diets at 2.0 times the energetic maintenance requirement or for ad libitum intake between 55 and 95 kg body weight. Within feeding levels, pigs received, in random order, low-protein (LP; 11.2% CP, 0.61% lysine) or high-protein (HP; 20.2% CP, 0.61% lysine) diets of similar digestible energy content. Dietary NE was calculated from heat production based on 24-h indirect calorimetry following a 7-day N-balance period. Feed intake was greater for LP than HP when fed for ad libitum intake (p = 0.001). Protein level did not affect daily gain (p > 0.1) but HP improved gain: feed (p = 0.003). Dietary ME and NE were not significantly affected by feeding level but were decreased by high protein intake (p < 0.07). Reducing dietary protein reduced urinary energy losses and increased energy retention but did not affect heat production. The effect of dietary protein restriction was already evident on the ME level and carried over to a similar degree to the NE level because the utilization of ME was not affected by protein level. Dietary ME and NE decreased by 0.012 MJ/kg (p = 0.014) and 0.018 MJ/kg (p = 0.062), respectively, for each gram per day N intake. The results suggest that although there was an effect of protein level on NE, the greatest effect occurred at the level of ME. However, the prediction of both ME and NE may be improved by adopting energy values for dietary protein that changes with dietary protein content.

The Metabolic Availability of Threonine in Common Feedstuffs Fed to Adult Sows Is Higher Than Published Ileal Digestibility Estimates

Amino acid (AA) requirements for sows during pregnancy are currently under review. However, requirement recommendations must be accompanied by an estimate of the bioavailability of AA from feeds to ensure adequate supply of AA and to minimize excess nitrogen excretion. Current ileal AA digestibility estimates are based on growing pig data; however, availability of AA in adult pigs may be different from that in growing pigs. The metabolic availability (MA) of threonine (Thr) in corn and barley was determined in 6 pregnant sows using the indicator AA oxidation method and L-[1-(13)C]phenylalanine as the tracer AA. Sows were fed reference diets formulated from 30 to 75% of the breakpoint derived in Expt. 1; all other nutrients were set at 120% of requirement. Test ingredients diets were formulated to supply Thr at 75% of the determined requirement. Tracer phenylalanine was given orally in 8 one-half-hourly meals and expired (13)CO(2) was quantified. The determined MA of Thr from corn and barley fed to pregnant sows was 88.0 and 89.3%, respectively. The determined MA was 7 and 9% greater than the published standard ileal digestibility estimates of Thr in corn (82%) and barley (81%), respectively. Mature animals have a greater capacity to digest and absorb nutrients from feed ingredients than previously assumed based on ileal digestibility studies. Sow diets formulated based on published ileal digestibility estimates are overformulated with respect to available protein and AA and thus increase excess nitrogen excretion and potential environmental concerns.

Amino acid nutrition and feed efficiency

In growing pigs, whole body protein deposition (PD) is the main determinant of dietary amino acid requirements and is closely associated with lean tissue growth, feed efficiency, and carcass quality. In North America, the typical mean PD for barrows and gilts between 25 and 125 kg body weight is approximately 135 g/d, but PD is known to be highly variable between and within groups of pigs. The use of dietary amino acids for PD involves digestion, absorption, and post-absorptive metabolism; biological processes which are all influenced by factors associated with the animal (pig genotype, physiological state, and health status) and the environment (diet composition, thermal and physical environment) and should be considered when establishing optimum dietary amino acid levels for groups of pigs. Mathematical models, such as the NRC (2012), are now available in which the biology of dietary amino acid utilization for PD is represented which can be used to estimate amino acid requirements of groups of pigs maintained in a relatively stress and disease-free environment. For predicting amino acid requirements of groups of pigs, between-animal variation in growth performance and nutrient utilization should also be taken into account. In addition, nutritional history and compensatory growth should be considered when establishing optimum dietary amino acid levels for maximum profit. Some examples are provided in this chapter to illustrate the effect of gender and feeding high-fiber co-products on amino acid requirements of growing-finishing pigs.