Performance of pigs kept under different sanitary conditions affected by protein intake and amino acid supplementation

Effects of sanitary conditions with lipopolysaccharide injection and dietary valine supplementation on growth performance, immune response, bacterial profile, and microbial metabolites in weaned pigs

This study investigated the effects of dietary L-valine (Val) supplementation and sanitary conditions with lipopolysaccharide injection on growth performance, immune response, and intestinal bacterial profiles and metabolites in weaned pigs. Thirty-two weaned pigs (6.98 ± 0.47 kg) were randomly assigned to treatments in a 2 × 2 factorial arrangement based on dietary Val levels and sanitary conditions (low or high). The pigs were fed either a basal diet containing the standard levels of Val suggested by (NRC), (2012) or a basal diet supplemented with 0.1% L-Val. A room designated as a high sanitary room was washed weekly, whereas the designated low sanitary room was not washed throughout the experiment and 5 kg of manure from the nursery pig barn was spread on the pen floors on day 1. All data were analysed using a mixed procedure of SAS, with the individual pen as the experimental unit. The pigs raised in low sanitary conditions exhibited a lower (p < 0.05) average daily gain, average daily feed intake, and gain-to-feed ratio and a higher (p < 0.05) incidence of diarrhoea than those raised in high sanitary conditions during the 14-d experimental period. The pigs in the low sanitary group also had a lower (p < 0.05) concentration of butyrate in the jejunum and a higher (p < 0.05) concentration of NH3-N in the colon than those in the high sanitary group. Dietary Val supplementation was reduced (p < 0.05) plasma interleukin (IL)-1β and IL-1 receptor antagonist concentrations as well as isovalerate and NH3-N concentrations in the colon, regardless of sanitary conditions. Interactions between dietary Val supplementation and sanitary conditions were observed in the abundances of mRNA-encoding β-defensins 113, 125 and 129 (p < 0.05). In conclusion, dietary Val supplementation beneficially modulates inflammatory responses and microbial metabolites regardless of sanitary conditions while transcriptional levels of β-defensins are regulated by dietary Val supplementation in a manner dependent on housing hygiene conditions.

Increased Dietary Trp, Thr, and Met Supplementation Improves Performance, Health, and Protein Metabolism of Weaned Piglets under Mixed Management and Poor Housing Conditions

A sanitary challenge was carried out to induce suboptimal herd health while investigating the effect of amino acids supplementation on piglet responses. Weaned piglets of high sanitary status (6.33 ± 0.91 kg of BW) were distributed in a 2 × 2 factorial arrangement into two similar facilities with contrasting sanitary conditions and two different diets. Our results suggest that increased Trp, Thr, and Met dietary supplementation could support the immune systems of piglets under a sanitary challenge. In this manner, AA+ supplementation improved the performance and metabolism of piglets under mixed management and poor sanitary conditions. No major temporal microbiome changes were associated with differences in performance regardless of sanitary conditions or diets. Since piglets often become mixed in multiple-site production systems and facility hygiene is also often neglected, this study suggests that increased Trp, Thr, and Met (AA+) dietary supplementation could contribute to mitigating the side effects of these harmful risk factors in modern pig farms.

Classification of light Yorkshire pigs at different production stages using ordinary least squares and machine learning methods

Pig homogeneity and growth are major concerns for the pig industry today. Variability in pigs' size has a strong impact on profitability as uniformity plays a key role in the overall economic value of pigs produced. This research focused on statistical methods to identify pigs at risk of growth retardation at different stages of production. Data from 125 083 Yorkshire pigs at weaning (18-28 d), 59 533 pigs at the end of the nursery period (70-82 d) and 48 862 pigs at slaughter (155-170 d) were analyzed under three different cut-points (lowest 10, 20 and 30%) to characterize light animals. Records were randomly split into 2:1 training:testing sets, and each training data set was analyzed through an ordinary least squares approach and four machine learning algorithms (decision tree, random forest, and two alternative boosting approaches). A wide range of weighting functions were applied to give increased relevance to lighter pigs. Each resulting classification norm was used to classify light pigs in the testing data set. Both sensitivity and specificity were retained to construct the receiver operating characteristic curve, and the statistical performance of each analytical approach was evaluated by the area under the curve (AUC). In all production stages and cut-points, the random forest machine learning algorithm provided the highest AUC, closely followed by boosting procedures. For weaning BW (WW), factors related to birth BW and litter size accounted for more than 75% of the important prediction factors for light pigs. BW at the end of the nursery period and slaughter BW analyses revealed a similar pattern where WW and BW at the end of the nursery period accounted for more than 40 and 50% of statistical importance among the prediction factors, respectively. Machine learning algorithms are useful tools to easily evaluate the risk factors affecting the efficiency and homogeneity in swine. Since the BW at birth and weaning are key factors, sow nutrition and feeding management during gestation and lactation, along with piglet management during lactation, are identified as important influences on pig weight variability.

Amino acid supplementation counteracts negative effects of low protein diets on tail biting in pigs more than extra environmental enrichment

Low protein (LP) diets may increase the occurrence of damaging behaviours, like tail biting, in pigs. We investigated the effect of supplementing a LP diet with indispensable amino acids (IAA) or environmental enrichment on tail biting. Undocked pigs (n = 48 groups of 12) received either a normal protein diet (NP), a LP, LP with supplemented IAA (LP+), or LP diet with extra environmental enrichment (LP-E+) during the starter, grower, and finisher phase. Performance, activity, behaviour, and body damage were recorded. LP and LP-E+ had a lower feed intake, growth, and gain-to-feed ratio, and were more active than NP and LP+ pigs. LP-E+ pigs interacted most often with enrichment materials, followed by LP, LP+, and NP pigs. LP pigs showed more tail biting than all other groups during the starter phase and the finisher phase (tendency) compared to NP and LP+ pigs. Thus, LP-E+ only reduced tail biting in the starter phase, whereas LP+ tended to do so throughout. Tail damage was more severe in LP pigs than in NP and LP+, with LP-E+ in between. In conclusion, IAA supplementation was more effective than extra environmental enrichment in countering the negative effects of a low protein diet on tail biting in pigs.

Predicting Chemical Composition and Apparent Total Tract Digestibility on Freeze-Dried Not Ground Faeces Using Near-Infrared Spectroscopy in Pigs

The present study aimed to compare NIRS results using freeze-dried ground or not ground (FDG or FDNG) faeces to predict faecal chemical composition and apparent total tract digestibility (ATTD) coefficients. Two different batches of pigs were used (n = 20 mixed sex pens/batch; 11 pigs/pen; Duroc × (Large White × Landrace)). The first batch of pigs (B1; 50.1 ± 3.44 kg body weight (BW)) was used at 13 wks of age and the second batch (B2; 87.0 ± 4.10 kg BW) was used at 18 wks of age. For both B1 and B2, pens were assigned to five diets formulated to obtain a control [10.03 MJ of net energy (NE), 160.0 g of crude protein (CP), and 9.5 g of standardized ileal digestive (SID) lysine (Lys) per kg of feed], low protein (132.0 g CP and 7.5 g SID Lys), high protein (188.0 g CP and 11.5 g SID Lys), low energy (9.61 MJ NE/kg), and high energy (10.45 MJ NE/kg) diets. After a 10-day adaptation period, one faecal sample was collected daily from each pen floor during 6 days in both B1 and B2 (n = 120/batch). Faecal samples were freeze-dried and analysed via NIRS as FDNG and FDG faeces. Dry matter (DM), organic matter (OM), CP, gross energy (GE), fat, and ATTD coefficients were analysed/calculated. The NIRS calibrations were evaluated by cross-validation, splitting the data in four random groups, or using the leave-one-out method. For both FDNG and FDG faeces, coefficients of determination for calibration (R²_cv) and residual predictive deviation (RPD) values were: close to 0.9 and 3 for DM and CP, 0.7-0.8 and ≥2 for OM and GE, 0.6 and <2 for fat, and 0.54-0.75 and ≤2 for ATTD coefficients, respectively. CP was better predicted using FDG faeces (p < 0.05), while DM and OM ATTD were better predicted using FDNG faeces (p < 0.05). In conclusion, NIRS successfully predicts faeces' chemical components and ATTD coefficients of nutrients using FDNG or FDG faeces.

Effects of dietary protein content and crystalline amino acid supplementation patterns in low protein diets on intestinal bacteria and their metabolites in weaned pigs raised under Different sanitary conditions

The objective of this experiment was to investigate the effects of dietary crude protein (CP) content and crystalline amino acids (CAA) supplementation patterns in low CP (LCP) diets on intestinal bacteria and their metabolites in weaned pigs raised under clean (CSC) or unclean sanitary conditions (USC). One hundred forty-four piglets (6.35 ± 0.63 kg) were assigned to one of six treatments in a 3 × 2 factorial arrangement based on CP content and sanitary conditions in a randomized complete block design to give eight replicates with three pigs per pen over a 21-d period. Diets consisted of a high CP (HCP; 21%) and two LCP (18%) diets supplemented with 9 CAA (Lys, Met, Thr, Trp, Val, Ile, Leu, His, and Phe) or only six CAA (Lys, Met, Thr, Trp, Val, and Ile) to meet the requirements. The CSC room was washed weekly, whereas the USC room had sow manure spread in the pens from the beginning of the study and was not washed throughout the experiment. Jejunum and colon digesta were sampled on day 21. Both jejunum and colon digesta were analyzed for ammonia nitrogen, short-chain fatty acids, and biogenic amines but only colon digesta was analyzed for microbiome composition (16s rRNA sequencing on MiSeq). Data were analyzed using R software for 16S rRNA and the MIXED procedure of SAS for microbial metabolites. Sanitation, CP content, and CAA supplementation patterns did not affect the diversity of colonic bacterial composition in weaned pigs. Pigs raised under USC had greater (P < 0.05) jejunal ammonia nitrogen concentration than those raised under CSC. Pigs fed LCP diets had reduced (P < 0.05) jejunal ammonia nitrogen concentration compared to those fed the HCP diet. Interactions between sanitation and dietary CP content were observed (P < 0.05) for: (1) jejunal acetate and (2) colonic spermidine and spermine, whereby (1) acetate concentrations decreased from NCP to LCP in pigs raised under the CSC but those concentrations increased under the USC, and (2) spermidine and spermine concentrations increased in LCP diets compared to HCP diet under USC, unlike CSC which did not show any difference between HCP and LCP. In conclusion, reducing dietary CP lowered ammonia nitrogen content regardless of sanitation and increased microbial metabolites in weaned pigs raised under USC. However, LCP diets with different CAA supplementation patterns did not affect bacterial diversity in weaned pigs, regardless of the hygienic conditions where the animals were housed.

Increased dietary Trp, Thr, and Met supplementation improves growth performance and protein deposition of salmonella-challenged growing pigs under poor housing conditions

Highly intensified rearing conditions and precarious sanitary management predispose pigs to immune system activation, altered amino acid (AA) metabolism, and decreased growth performance. Thus, the main objective of this study was to evaluate the effects of increased dietary tryptophan (Trp), threonine (Thr), and methionine + cysteine (Met + Cys) supplementation on performance, body composition, metabolism, and immune responses of group-housed growing pigs under challenging sanitary conditions. A hundred and twenty pigs (25.4 ± 3.7 kg) were randomly assigned to a 2 × 2 factorial arrangement, consisting of two sanitary conditions (SC, good [GOOD] or salmonella-challenge and poor housing condition [Salmonella Typhimurium (ST) + POOR]) and two diets, control (CN) or supplemented with AA (Trp, Thr, and Met + Cys:Lys ratios 20% higher than those of the CN diet [AA>+]). Pigs were followed during the growing phase (25-50 kg) and the trial lasted 28 d. The ST + POOR SC pigs were challenged with Salmonella Typhimurium and raised in a poor housing condition. The ST + POOR SC increased rectal temperature, fecal score, serum haptoglobin, and urea concentration (P < 0.05) and decreased serum albumin concentration (P < 0.05) compared with GOOD SC. Body weight, average daily feed intake, average daily gain (ADG), feed efficiency (G:F), and protein deposition (PD) were greater in GOOD SC than in ST + POOR SC (P < 0.01). However, pigs housed in ST + POOR SC fed with AA+ diet had lower body temperature (P < 0.05), increased ADG (P < 0.05) and nitrogen efficiency (P < 0.05), and a tendency for improved PD and G:F (P < 0.10) compared with CN diet fed pigs. Regardless of the SC, pigs fed AA+ diet had lower serum albumin (P < 0.05) and tended to decrease serum urea levels (P < 0.10) compared with CN diet. The results of this study suggest that the ratio of Trp, Thr, and Met + Cys to Lys for pigs are modified by sanitary conditions. Furthermore, supplementation of diets with a blend of Trp, Thr, and Met + Cys improves performance, especially under salmonella-challenge and poor housing conditions. Dietary tryptophan, threonine, and methionine supplementation can modulate immune status and influence resilience to sanitary challenges.

Pathogen exposure influences immune parameters around weaning in pigs reared in commercial farms

BACKGROUND

Multiple antigenic stimulations are crucial to immune system training during early post-natal life. These stimulations can be either due to commensals, which accounts for the acquisition and maintenance of tolerance, or to pathogens, which triggers immunity. In pig, only few works previously explored the influence of natural exposition to pathogens upon immune competence. We propose herein the results of a multicentric, field study, conducted on 265 piglets exposed to contrasted pathogen levels in their living environment. Piglets were housed in 15 different commercial farms, sorted in two groups, low (HS^LOW)- and high (HS^HIGH)-health status farms, depending on their recurrent exposition to five common swine pathogens.

RESULTS

Using animal-based measures, we compared the immune competence and growth performances of HS^LOW and HS^HIGH pigs around weaning. As expected, we observed a rise in the number of circulating leucocytes with age, which affected different cell populations. Monocyte, antigen-experienced and cytotoxic lymphocyte subpopulation counts were higher in piglets reared in HS^LOW farms as compared to their HS^HIGH homologs. Also, the age-dependent evolution in γδ T cell and neutrophil counts was significantly affected by the health status. With age, circulating IFNα level decreased and IgM level increased while being greater in HS^LOW piglets at any time. After weaning, LPS-stimulated blood cells derived from HS^LOW piglets were more prone to secrete IL-8 than those derived from HS^HIGH pigs did. Monocytes and granulocytes issued from HS^LOW pigs also exhibited comparable phagocytosis capacity. Altogether our data emphasize the more robust immunophenotype of HS^LOW piglets. Finally, piglets raised under higher pathogen pressure grew less than HS^HIGH piglets did and exhibited a different metabolic profile. The higher cost of the immune responses associated with the low farm health status may account for lower HS^LOW piglet performances.

CONCLUSIONS

Altogether, our data, obtained in field conditions, provide evidence that early exposure to pathogens shapes the immune competence of piglets. They also document the negative impact of an overstimulation of the immune system on piglets' growth.

Formulating Diets for Improved Health Status of Pigs: Current Knowledge and Perspectives

Our understanding of nutrition has been evolving to support both performance and immune status of pigs, particularly in disease-challenged animals which experience repartitioning of nutrients from growth towards the immune response. In this sense, it is critical to understand how stress may impact nutrient metabolism and the effects of nutritional interventions able to modulate organ (e.g., gastrointestinal tract) functionality and health. This will be pivotal in the development of effective diet formulation strategies in the context of improved animal performance and health. Therefore, this review will address qualitative and quantitative effects of immune system stimulation on voluntary feed intake and growth performance measurements in pigs. Due to the known repartitioning of nutrients, the effects of stimulating the immune system on nutrient requirements, stratified according to different challenge models, will be explored. Finally, different nutritional strategies (i.e., low protein, amino acid-supplemented diets; functional amino acid supplementation; dietary fiber level and source; diet complexity; organic acids; plant secondary metabolites) will be presented and discussed in the context of their possible role in enhancing the immune response and animal performance.

Effects of dietary protein content and crystalline amino acid supplementation patterns on growth performance, intestinal histomorphology, and immune response in weaned pigs raised under different sanitary conditions

The aim of this experiment was to investigate the effects of dietary crude protein (CP) contents and crystalline amino acids (CAA) supplementation patterns on growth performance, intestinal histomorphology, and immune response in weaned pigs under clean (CSC) or unclean sanitary conditions (USC). A total of 144 weaned pigs (6.35 ± 0.63 kg body weight) were assigned to 6 treatments in a 3 × 2 factorial arrangement based on CP content and sanitary conditions using a randomized complete block design, giving 8 replicates per treatment with 3 pigs per pen. Pigs were fed one of three diets for 21 d: one high CP (HCP; 22%) and two low CP (LCP; 19%) diets supplemented with 9 indispensable AA or only 6 AA (Lys, Met, Thr, Trp, Val, and Ile) as CAA. The CSC room was washed weekly, whereas the USC room had sow manure spread in the pens and was not washed throughout the experiment. Body weight and feed disappearance were recorded weekly. Blood was sampled from 1 pig per pen weekly, and the same pig was euthanized for jejunal tissues sampling on day 21. Pigs raised under USC had reduced (P < 0.05) average daily gain (ADG) and gain to feed ratio (G:F) in week 2, but contrary results that greater (P < 0.05) ADG and G:F were found in pigs under USC in week 3. Overall, there was an interaction where G:F did not differ between HCP and LCP under CSC, however, LCP decreased (P < 0.05) G:F compared to HCP under USC. Pigs fed the HCP diet had higher (P < 0.05) fecal scores than those fed the LCP diets throughout the experiment. Pigs fed the LCP had higher (P < 0.05) villus height to crypt depth ratio than those fed the HCP. An interaction was observed where goblet cell density in the jejunum was higher (P < 0.05) in pigs fed LCP than HCP under CSC, but no difference was found between HCP and LCP under USC. Different CAA supplementation patterns did not influence both growth performance and histomorphology. Pigs raised under USC had greater (P < 0.05) plasma interleukin (IL)-10 and IL-6 concentrations and reduced (P < 0.05) plasma tumor necrosis factor-alpha concentration. Also, the LCP diets resulted in a greater (P < 0.05) plasma IL-10 concentration. In conclusion, overall growth performance did not differ between HCP and LCP under CSC, but LCP diets reduced G:F under USC. Feeding LCP diets to weaned pigs improved gut morphology under USC and ameliorated systemic inflammation induced by USC, whereas CAA supplementation patterns did not affect growth performance and gut morphology.

Blood and faecal biomarkers to assess dietary energy, protein and amino acid efficiency of utilization by growing and finishing pigs

Background

Diet evaluation and optimization is a slow and expensive process and it is not possible to do it at a farm level. This study aimed to use the blood serum metabolite (BSM) and faecal volatile fatty acid (VFA) profiles as potential biomarkers to identify changes in protein, amino acid and energy dietary content in growing and finishing pig diets at farm level.

Results

Two studies were conducted. The first study (S1) included 20 pens of 11 pigs (87.0 ± 4.10 kg; 18 weeks old) assigned to 5 diets: control (C1), high or low crude protein (HP1 and LP1, respectively), and high or low net energy (HE1 and LE1, respectively). The second study (S2) included 28 pens of 11 pigs (41.3 ± 2.60 kg; 12 weeks old) assigned to 7 diets: control (C2), high or low crude protein (HP2 and LP2, respectively), high or low amino acid (HA2 and LA2, respectively), and high or low net energy (HE2 and LE2, respectively). Pigs were followed for 10 (S1) and 20 (S2) days, and blood and faecal samples were collected at 20 (S1) and 14 (S2) weeks of age. Data were analysed using general linear models and receiver operating characteristic curve analysis. Urea nitrogen showed the best results as a biomarker. Urea nitrogen was higher in pigs fed high protein diets, HP1 (13.6 ± 0.95 mg/dL) and HP2 (11.6 ± 0.61), compared to those fed low protein diets, LP1 (6.0 ± 0.95) and LP2 (5.2 ± 0.61; P < 0.001), showing good discrimination ability (Area under the curve (AUC) = 98.4 and 100%, respectively). These differences were not observed between diets LA2 (6.5 ± 0.61) and HA2 (8.7 ± 0.61; P > 0.05; AUC = 71.9%), which were formulated based on the ideal protein profile but with no excess of protein. Creatinine, triglycerides, branched-chain fatty acids, albumin, propionic acid, and cholesterol showed differences between at least 2 diets but only in one of the studies.

Conclusions

Urea nitrogen showed high accuracy to detect excess of crude protein in growing and finishing pig diets. Other biomarkers like BCFA showed promising results and need to be further studied.

Effect of Varying Levels of Dietary Tryptophan on Aggression and Abnormal Behavior in Growing Pigs

Body lesions, resulting from tail-biting and ear-biting, can result in decreased health and welfare in pigs. Tryptophan, an indispensable amino acid, is needed to support protein deposition, and the synthesis of the neurotransmitter serotonin, which is important to mood, sleep-wake and eating patterns and might play a role in aggression and abnormal behavior. Two randomized block design studies were conducted to assess the influence of varying dietary tryptophan levels on aggression and abnormal behavior in 8-week-old pigs. Six diets were formulated which met or exceeded all nutrient requirements yet differed according to the dietary tryptophan content. The first study included control (100% standardized ileal digestible tryptophan), supplemented (175% standardized ileal digestible tryptophan), and supplement-plus (250% standardized ileal digestible tryptophan) experimental diets, while the second study included deficient (80% standardized ileal digestible tryptophan), adequate control (105% standardized ileal digestible tryptophan), and extra-tryptophan (130% standardized ileal digestible tryptophan) experimental diets. Concentrations of plasma tryptophan and large neutral amino acids (tyrosine, isoleucine, leucine, valine, and phenylalanine) were analyzed using ultra-performance liquid chromatography and the tryptophan to large neutral amino acid ratio was calculated. Analysis for time active, lying, and engaging in aggressive interactions was carried out using 10-min scan samples to determine behavioral time budgets of the pigs on different experimental diets. Pigs fed diets with supplemented tryptophan had higher concentrations of both plasma tryptophan and tryptophan to large neutral amino acid ratio compared to the pigs fed the control diet (P < 0.05) in the first study, while no significant differences were detected for plasma tryptophan or the tryptophan to large neutral amino acid ratio in the second study. Diet did not have an effect (P > 0.05) on weight, feed intake or behavior throughout the studies. The results suggest that an increase in dietary tryptophan relative to large neutral amino acids, fed for 29 days, impacts circulating plasma tryptophan and therefore, serotonin concentrations in the pig. Despite an increase in circulating plasma tryptophan in response to an increase in dietary tryptophan in the first study, we failed to see an impact of the dietary treatment on body, tail and ear-biting behavior under the conditions studied.

Poor hygiene of housing conditions influences energy metabolism in a muscle type-dependent manner in growing pigs differing in feed efficiency

The ability of pigs to cope with inflammatory challenges may by modified by selection for residual feed intake (RFI), a measure of feed efficiency. In the current study, we evaluated skeletal muscle metabolic responses to degraded hygiene conditions in pigs divergently selected for RFI. At 82 d of age, low RFI and high RFI pigs were housed in either poor or good hygiene conditions. After a 6-week challenge, the poor hygiene conditions induced a decrease in growth performance (P < 0.001) and in plasma IGF-I concentrations (P < 0.003) in both lines. In the slow-twitch oxidative semispinalis muscle, poor hygiene conditions induced a shift towards a more oxidative metabolism and an activation of the AMPK pathway in pigs of both RFI lines. In the fast-twitch glycolytic longississimus muscle, poor hygiene conditions were associated to a less glycolytic metabolism in the HRFI line only. Poor hygiene conditions also increased the protein level of lipidation of microtubule-associated protein 1 light-chain 3β (LC3-II) in both RFI lines, suggesting an activation of the autophagy pathway. Altogether, the data revealed muscle-type specific metabolic adaptations to poor hygiene conditions, which may be related to different strategies to fuel the activated immune system.

Use of low dosage amino acid blends to prevent stress-related piglet diarrhea

Weaning is a challenging period for piglets associated with reduced feed intake, impairment of gut integrity, and diarrhea. Previous studies demonstrate that supplementation with single functional amino acids (AA) promote piglets' performance due to the improvement of intestinal health. Thus, we hypothesized that a combination of functional AA provided beyond the postulated requirement for growth could facilitate the weaning transition. Ninety piglets, initially stressed after weaning by 100 min overland transport, received a control diet or the same diet supplemented with a low-dosed (0.3%) mixture of AA (AAB-1: L-arginine, L-leucine, L-valine, L-isoleucine, L-cystine; AAB-2: L-arginine, L-leucine, L-valine, L-isoleucine, L-cystine, and L-tryptophan) for 28 days. Fecal consistency was ranked daily, growth performance was assessed weekly. On days 1 and 14 of the trial, blood samples were collected from a subset of 10 piglets per group to assess concentrations of insulin-like growth factor 1. After 28 days of feeding, tissues were obtained from the same piglets to analyze gut morphology and relative mRNA expression of genes related to gut function. Even if the stress response as indicated by rectal temperature was not different between the groups, pigs supplemented with AAB-2 showed firmer feces after weaning and less days with diarrhea compared to control. Furthermore, the jejunal expression of the MUC-2 gene was reduced (P < 0.05) in group AAB-2. Both AA mixtures increased crypt depth in the duodenum. Collectively, the given results indicate that 0.3% extra AA supplementation might alleviate postweaning diarrhea but did not alter growth performance of weanling piglets.

High levels of standardized ileal digestible amino acids improve feed efficiency in slow-growing pigs at late grower-finisher stage

Slow-growing pigs negatively affect production efficiency in conventional pig farms by increasing the occupation time of the facilities and being a limiting factor for the All-In/All-Out swine production systems. This subset of pigs is usually managed with the rest of the pigs, and their nutrient requirements may not be fulfilled. The purpose of the present study was to compare the productive performance of slow- and fast-growing pigs to different standardized ileal digestible (SID) amino acids (AA) dietary levels at late grower-finisher stage. A total of 84 pigs were weighed, tagged, and classified as slow-growing (SG; n = 48; 24.1 ± 1.38 kg) or fast-growing pigs (FG; n = 36; 42.7 ± 1.63 kg) at 11 weeks of age. Pigs were housed in mixed sex pens (n = 8 SG+6 FG/pen) equipped with feeding stations to record daily feed intake per individual pig. Pigs were assigned to three dietary treatments resulting in a 2 × 3 factorial arrangement at 15 weeks of age. Isoenergetic diets were formulated by increasing the ideal protein profile based on the following SID lysine (Lys) levels: 0.92%, 1.18% and 1.45%. Pigs were weighed bi-weekly until 21 weeks of age. Fast-growing pigs were 33.7 kg heavier, gained 255 g/day and consumed 625.5 g/day more than SG pigs (p < 0.001). No interaction or diet effects were observed for final body weight, average daily gain and average daily feed intake (p > 0.05). However, feed conversion ratio was 0.3 lower for SG pigs fed 1.45% SID Lys/AA compared to SG pigs fed 0.92% SID Lys/AA (p = 0.002). Feed conversion ratio was not different within the FG pigs' dietary treatments (p > 0.05). The efficiency of SG pigs may be improved when dietary SID AA levels are increased from 0.92 up to 1.45% SID Lys/AA. Thus, nutrient requirements may vary depending on growth rate at the same age, and SG pigs may require higher dietary SID AA levels than FG pigs to achieve similar productive performance.

Factors affecting performance response of pigs exposed to different challenge models: a multivariate approach

Factors associated with the severity with which different challenge models (CMs) compromise growth performance in pigs were investigated using hierarchical clustering on principal components (HCPC) analysis. One hundred seventy-eight studies reporting growth performance variables (average daily gain [ADG], average daily feed intake [ADFI], gain:feed [GF], and final body weight [FBW]) of a Control (Ct) vs. a Challenged (Ch) group of pigs using different CMs (enteric [ENT], environmental [ENV], lipopolysaccharide [LPS], respiratory [RES], or sanitary condition [SAN] challenges) were included. Studies were grouped by similarity in performance in three clusters (C1, C2, and C3) by HCPC. The effects of CM, cluster, and sex (males [M], females [F], mixed [Mi]) were investigated. Linear (LRP) and quadratic (QRP) response plateau models were fitted to assess the interrelationships between the change in ADG (∆ADG) and ADFI (∆ADFI) and the duration of challenge. All variables increased from C1 through C3, except for GF, which decreased (P < 0.05). LPS was more detrimental to ADG than ENV, RES, and SAN models (P < 0.05). Furthermore, LPS also lowered GF more than all the other CMs (P < 0.05). The ∆ADG independent of ∆ADFI was significant in LPS and SAN (P < 0.05), showed a trend toward the significance in ENT and RES (P < 0.10), and was not significant in ENV (P > 0.10), while the ∆ADG dependent on ∆ADFI was significant in ENT, ENV, and LPS only (P < 0.05). The critical value of ∆ADFI influencing the ∆ADG was significant in pigs belonging to C1 (P < 0.05) but not C2 or C3 (P > 0.10). The ∆ADG independent of duration post-Ch (irreparable portion of growth) was significant in C1 and C2 pigs, whereas the ∆ADFI independent of duration post-Ch (irreparable portion of feed intake) was significant in C1 pigs only (P < 0.05). Moreover, the time for recovery of ADG and ADFI after Ch was significant in pigs belonging to C1 and C2 (P < 0.05). Control F showed reduced ADG compared with Ct-M, and Ch-F showed reduced ADFI compared with Ch-M (P < 0.05). Moreover, the irreparable portion of ΔADG was 4.8 higher in F (-187.7; P < 0.05) compared with M (-39.1; P < 0.05). There are significant differences in growth performance response to CM based on cluster and sex. Furthermore, bacterial lipopolysaccharide appears to be an appropriate noninfectious model for immune stimulation and growth impairment in pigs.

Functional amino acid supplementation, regardless of dietary protein content, improves growth performance and immune status of weaned pigs challenged with Salmonella Typhimurium

High dietary protein may increase susceptibility of weaned pigs to enteric pathogens. Dietary supplementation with functional amino acids (FAA) may improve growth performance of pigs during disease challenge. The objective of this study was to evaluate the interactive effects of dietary protein content and FAA supplementation above requirements for growth on performance and immune response of weaned pigs challenged with Salmonella. Sixty-four mixed-sex weanling pigs (13.9 ± 0.82 kg) were randomly assigned to dietary treatments in a 2 × 2 factorial arrangement with low (LP) or high protein (HP) content and basal (AA-) or FAA profile (AA+; Thr, Met, and Trp at 120% of requirements) as factors. After a 7-d adaptation period, pigs were inoculated with either a sterile saline solution (CT) or saline solution containing Salmonella Typhimurium (ST; 3.3 × 109 CFU/mL). Growth performance, body temperature, fecal score, acute-phase proteins, oxidant/antioxidant balance, ST shedding score in feces and intestinal colonization, fecal and digesta myeloperoxidase (MPO), and plasma urea nitrogen (PUN) were measured pre- and postinoculation. There were no dietary effects on any measures pre-inoculation or post-CT inoculation (P > 0.05). Inoculation with ST increased body temperature and fecal score (P < 0.05), serum haptoglobin, plasma superoxide dismutase (SOD), malondialdehyde (MDA), PUN, and fecal MPO, and decreased serum albumin and plasma reduced glutathione (GSH):oxidized glutathione (GSSG) compared with CT pigs (P < 0.05). ST-inoculation reduced average daily gain (ADG) and feed intake (ADFI) vs. CT pigs (P < 0.05) but was increased by AA+ vs. AA- in ST pigs (P < 0.05). Serum albumin and GSH:GSSG were increased while haptoglobin and SOD were decreased in ST-inoculated pigs fed AA+ vs. AA- (P < 0.05). PUN was higher in HP vs. LP-fed pigs postinoculation (P < 0.05). Fecal ST score was increased in ST-inoculated pigs on days 1 and 2 postinoculation and declined by day 6 (P < 0.05) in all pigs while the overall score was reduced in AA+ vs. AA- pigs (P < 0.05). Cecal digesta ST score was higher in HP vs. LP-fed pigs and were lower in AA+ compared with AA- fed pigs in the colon (P < 0.05). Fecal and digesta MPO were reduced in ST pigs fed AA+ vs. AA- (P < 0.05). These results demonstrate a positive effect of FAA supplementation, with minimal effects of dietary protein, on performance and immune status in weaned pigs challenged with Salmonella.

Soiling of Pig Pens: A Review of Eliminative Behaviour

Simple Summary

The soiling of pig pens has important negative consequences in terms of animal welfare, health, workload, and environmental emissions of pig farming. The aim of this review is to present the state-of-the-art regarding pigs’ normal eliminatory behaviour (i.e., defaecation and urination) and pen soiling, aimed here at solving pen-soiling problems in existing systems, and in a following publication aimed at the design of a more sustainable pig-farming system. To this end, we summarize a large body of literature on pen soiling and pigs’ eliminative behaviour in different farming systems. We propose a “disease framework” interpretation of pen soiling, to help identify its causes, underlying mechanisms, and solutions.

Abstract

This is a comprehensive review on the pigs’ normal eliminatory behaviour (i.e., defaecation and urination) and pen soiling. This review is aimed primarily at solving issues with pen soiling in current systems, and ultimately at the future design of a well-functioning pig toilet, which we intend to elaborate on in a subsequent publication. In this paper, first, normal elimination is described in relation to what is known about its phylogeny, ontogeny, causation, and function, i.e., according to Tinbergen’s four why questions concerning animal behaviour. Then, pen soiling is described as if it were a medical disorder, highlighting its importance, aetiology, symptoms, diagnosis, pathogenesis, treatment, and prevention. Due to its negative consequences in terms of animal welfare, health, workload, and environmental emissions, possible methods to address pen soiling in current systems are described. Probably, pigs do not choose a specific place to eliminate but rather choose the most comfortable place for resting, and avoid eliminating there. We identified four main strategies to reduce pen soiling: (1) reducing the suitability of the designated elimination area to be used for other functions, especially resting or thermoregulation; (2) improving the suitability of other functional areas in the pen to be used for their specific function, such as resting and activity; (3) reducing the suitability of other functional areas to be used for elimination; and (4) improving the suitability of the elimination area for elimination. These prevention strategies and the encompassing disease framework provide a structured approach to deal with pen soiling in existing systems and to support the future design, development, and implementation of a well-functioning pig toilet that can help to achieve some of the main goals of modern pig production, namely reducing environmental emissions as well as substantially improving pig welfare.

Sanitary Conditions Affect the Colonic Microbiome and the Colonic and Systemic Metabolome of Female Pigs

Differences in sanitary conditions, as model to induce differences in subclinical immune stimulation, affect the growth performance and nutrient metabolism in pigs. The objective of the present study was to evaluate the colonic microbiota and the colonic and systemic metabolome of female pigs differing in health status induced by sanitary conditions. We analyzed blood and colon digesta metabolite profiles using Nuclear Magnetic Resonance (1H NMR) and Triple quadrupole mass spectrometry, as well as colonic microbiota profiles. 1H NMR is a quantitative metabolomics technique applicable to biological samples. Weaned piglets of 4 weeks of age were kept under high or low sanitary conditions for the first 9 weeks of life. The microbiota diversity in colon digesta was higher in pigs subjected to low sanitary conditions (n = 18 per treatment group). The abundance of 34 bacterial genera was higher in colon digesta of low sanitary condition pigs, while colon digesta of high sanitary status pigs showed a higher abundance for four bacterial groups including the Megasphaera genus (p < 0.003) involved in lactate fermentation. Metabolite profiles (n = 18 per treatment group) in blood were different between both groups of pigs. These different profiles suggested changes in general nutrient metabolism, and more specifically in amino acid metabolism. Moreover, differences in compounds related to the immune system and responses to stress were observed. Microbiome-specific metabolites in blood were also affected by sanitary status of the pigs. We conclude that the microbiome composition in colon and the systemic metabolite profiles are affected by sanitary conditions and related to suboptimal health. These data are useful for exploring further relationships between health, metabolic status and performance and for the identification of biomarkers related to health (indices) and performance.

A Proposed Role for Pro-Inflammatory Cytokines in Damaging Behavior in Pigs

Sickness can change our mood for the worse, leaving us sad, lethargic, grumpy and less socially inclined. This mood change is part of a set of behavioral symptoms called sickness behavior and has features in common with core symptoms of depression. Therefore, the physiological changes induced by immune activation, for example following infection, are in the spotlight for explaining mechanisms behind mental health challenges such as depression. While humans may take a day off and isolate themselves until they feel better, farm animals housed in groups have only limited possibilities for social withdrawal. We suggest that immune activation could be a major factor influencing social interactions in pigs, with outbreaks of damaging behavior such as tail biting as a possible result. The hypothesis presented here is that the effects of several known risk factors for tail biting are mediated by pro-inflammatory cytokines, proteins produced by the immune system, and their effect on neurotransmitter systems. We describe the background for and implications of this hypothesis.

Effects of Early Nutrition and Sanitary Conditions on Oral Tolerance and Antibody Responses in Broiler Chickens

Greater antigenic exposure might accelerate activation and maturation of the humoral immune system. After hatch, commercial broiler chickens can have early (EN) or delayed (DN) access to nutrition, up to 72 h after hatch. The immune system of EN versus DN broilers is likely more exposed to antigens after hatch. This might contribute to activation and maturation of the immune system, but might also influence the development of oral tolerance, thereby altering later life antibody responses. We studied antibody (IgM, IgY, IgA) responses between 21 and 42 d of age in fast-growing EN and DN broilers, kept under low (LSC) or high sanitary conditions (HSC). In a first experiment (n = 51 broilers), we tested whether early oral exposure to bovine serum albumin (BSA) affected later life antibody responses towards BSA and a novel antigen-rabbit γ-globulin (RGG), under HSC. In a second experiment, a total of 480 EN and DN broilers were housed under either LSC or HSC, and we studied antibody responses against both BSA and RGG (n = 48 broilers per treatment) and growth performance. Broilers kept under LSC versus HSC, had higher antibody levels and their growth performance was severely depressed. Interactions between feeding strategy (EN versus DN) and sanitary conditions, or main effects of feeding strategy, on natural and specific antibody levels, and growth performance were not observed. Levels of IgA were elevated in EN versus DN broilers, in experiment I and in batch 2 of experiment II, but not in the other batches of experiment II. We concluded that EN versus DN contributes minimally to the regulation of antibody responses, irrespective of antigenic pressure in the rearing environment.

Low sanitary conditions increase energy expenditure for maintenance and decrease incremental protein efficiency in growing pigs

Requirements for energy and particular amino acids (AAs) are known to be influenced by the extent of immune system stimulation. Most studies on this topic use models for immune system stimulation mimicking clinical conditions. Extrapolation to conditions of chronic, low-grade immune system stimulation is difficult. We aimed to quantify differences in maintenance energy requirements and efficiency of energy and protein used for growth (incremental energy and protein efficiency) of pigs kept under low (LSC) or high sanitary conditions (HSC) that were fed either a basal diet or a diet with supplemented AA. Twenty-four groups of six 10-week-old female pigs were kept under either LSC or HSC conditions for 2 weeks and fed a diet supplemented or not with 20% extra methionine, threonine and tryptophan. In week 1, feed was available ad libitum. In week 2, feed supply was restricted to 70% of the realized feed intake (kJ/(kg BW)0.6 per day) in week 1. After week 2, fasting heat production (FHP) was measured. Energy balances and incremental energy and protein efficiencies were measured and analyzed using a GLM. Low sanitary condition increased FHP of pigs by 55 kJ/(kg BW)0.6 per day, regardless of diet. Low sanitary condition did not alter the response of faecal energy output to incremental gross energy (GE) intake, but it reduced the incremental response of metabolizable energy intake (12% units), heat production (6% units) and energy retained as protein (6% units) to GE intake, leaving energy retained as fat unaltered. Incremental protein efficiency was reduced in LSC pigs by 20% units. Incremental efficiencies for energy and protein were not affected by dietary AA supplementation. Chronic, low-grade immune stimulation by LSC treatment increases FHP in pigs. Under such conditions, the incremental efficiency of nitrogen utilization for body protein deposition is reduced, but the incremental efficiency of absorbed energy for energy or fat deposition is unaffected.

Effects of interactions between feeding practices, animal health and farm infrastructure on technical, economic and environmental performances of a pig-fattening unit

European pig production faces economic and environmental challenges. Modelling can help farmers simulate and understand how changes in their management practices affect the efficiency of their production system. We developed an individual-based model of a pig-fattening unit that considers individual variability in performance among pigs, farmers' feeding practices and animal management and estimates environmental impacts (using life cycle assessment) and economic results of the unit. We previously demonstrated that this model provides reliable estimates of farm performance for different combinations of management practices, pig types and building characteristics. The objectives of this study were to quantify how interactions between feeding practices and animal management influence fattening unit results in healthy or impaired health conditions using the model. A virtual experiment was designed to evaluate effects of interactions between feeding practices, health status of the pig herd and infrastructure constraints on the technical performance, economic results and environmental impacts of the unit. The virtual experiment consisted of 96 scenarios, which combined chosen values of 6 input parameters of the model: batch interval (35 days and 7 days), use or non-use of a buffer room to manage the lightest pigs, feed rationing (ad libitum and restricted) and sequence plans (two-phase (2P), daily-phase (DP)), scale at which the feeding plan is applied (i.e. room, pen and individual) and health status of the pig herd (i.e. healthy v. impaired). Variance analysis was used to test effects of the factors in these 96 scenarios, and multivariate data analyses were used to classify the scenarios. Healthy populations obtained on average higher economic results (e.g. gross margin of 11.20 v. 1.50 €/pig) and lower environmental impacts (e.g. 2.24 v. 2.38 kg CO2-eq/kg pig live weight gain) than the population with impaired health. With 35 days batch interval and DP feeding, populations with impaired health reached gross margin similar to healthy populations with 2P ad libitum feeding and 7 days batch interval. Restricted, DP and individual feeding plans improved the economic and environmental performances of the unit for both health statuses. This study highlighted that health status of the pig herd is the main factor that affects technical, economic and environmental performances of a pig-fattening unit, and that adequate feeding strategies and animal management can compensate, to some extent, the effects of impaired health on environmental impacts but not on gross margin.

Transfer of natural auto-antibodies via egg yolk in chickens divergently selected for natural antibodies binding keyhole limpet hemocyanin

Barcodes of natural auto-antibody (NAAb) profiles based on staining intensity of isotypes binding numbers of self-(tissue) antigen fragments were suggested as parameters for immune diversity, and related to genetic background and health status in man, rodents and poultry. Here, hens, eggs and hatchlings from chicken lines divergently selected and bred for high (H line) or low (L line) total natural antibodies (NAb) levels in plasma binding keyhole limpet hemocyanin (KLH) at 16 weeks of age were tested for their NAAb repertoire binding chicken liver homogenate (CLH) fragments using quantitative Western immunoblotting. The aims of this study were 1. to detect line differences between the H and L line adult hens, eggs and hatchlings for the IgM and IgG isotypes binding CLH fragments, 2. study the presence of NAAb of both isotypes in yolk and albumen, as well as in hatchlings to detect a maternal NAAb transfer route via the egg to the hatchling, and 3. study whether new self-antigen binding isotypes and idiotypes are present in the hatchling. NAAb binding CLH fragments were found in plasma of adult hens (both IgM and IgG), in yolk (IgG only), and hatchlings (mostly IgG, but low levels of IgM). Auto-profiles of IgM showed homogeneity, while IgG profiles were heterogenic between individual hens and individual hatchlings. Significant higher levels as indicated by staining intensity and number of stained CLH fragments were found in plasma of hens genetically selected for high levels of NAb binding KLH. Lines could be clustered based on their auto-profiles indicating that profiles of self-binding IgM and IgG antibodies are genetically based. Visual comparison, clustering and correlation of hens and their hatchlings showed similarities for the IgG, but not the IgM isotype, indicating maternal transfer of IgG NAAb via the yolk. The IgM profile in the hatchlings on the other hand might represent neonatal self-binding antibody formation. As a consequence, hatchlings initially depend for self-binding antibodies on maternal IgG provision during early life.

Effects of dietary calcium pyruvate on gastrointestinal tract development, intestinal health and growth performance of newly weaned piglets fed low-protein diets

AIM

This study was carried out to investigate the effects of dietary calcium pyruvate supplementation on growth performance and intestinal health of weaned piglets fed low-protein diets.

METHODS AND RESULTS

After a 7-day adaptation period, 60 individually housed piglets (Duroc × Yorkshire-Landrace) weaned at 28 days of age were randomly assigned to receive one of three treatments (20 pigs/treatment) for 28 days: control diet (20·0% crude protein [CP]), low-protein diet (15·5% CP), and experimental (15·5% CP + 1·8% calcium pyruvate). At the end of the experiment, six piglets from each diet group were slaughtered and blood and tissue samples were collected. Compared with the control group, feeding piglets with 15·5% CP decreased the daily body weight gain; lengths of the duodenum, jejunum and ileum; and weights of the stomach, duodenum, jejunum and ileum (P < 0·05), while 15·5% CP + 1·8% calcium pyruvate supplementation removed those differences (P > 0·05). Compared with the control group, the diarrhoea incidence and relative richness of Firmicutes in the colon contents of piglets in both the 15·5% CP and 15·5% CP + 1·8% calcium pyruvate groups was decreased. The relative richness of Bacteriodetes in the colon contents of piglets was higher in the 15·5% CP + 1·8% calcium pyruvate group than in the control and 15·5% CP groups (P < 0·05).

CONCLUSION

Calcium pyruvate supplementation for four weeks removed the negative effects of a low-protein diet on the gastrointestinal tract development and daily body weight gain of weaned piglets.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study showed that supplementing a low-protein diet with calcium pyruvate, an effective alternative metabolic fuel to amino acids, was beneficial in improving the intestinal health and maximizing the growth of newly weaned piglets.

Effect of supplemental threonine above requirement on growth performance of Salmonella typhimurium challenged pigs fed high-fiber diets1

It was shown previously that high dietary fiber (DF) and immune system stimulation (ISS) with systemic Escherichia coli lipopolysaccharide independently increased the threonine (Thr) requirement to maximize growth performance and protein deposition (PD). However, no additive effects on the Thr requirement were observed when both DF and ISS were present. The objective of the present study was to investigate whether supplementing Thr to meet previously estimated requirements for high DF and systemic immune challenge would maintain performance of pigs exposed to an enteric immune challenge when fed high DF. A total of 128 pigs (22.6 ± SD = 1.6 kg initial BW) were assigned to 1 of 4 dietary treatments in a 2 × 2 factorial arrangement in a randomized complete block design (n = 8 pens/treatment and 4 pigs/pen) for 28 d. Treatments were a low-fiber (LF; 13% total DF) or high-fiber (HF; 20% total DF) diet with either a standard (STD; 0.65% SID) or supplemental (SUP; 0.78% SID) Thr level. After a 7-d adaptation, pigs were orally inoculated with 2 mL (2.3 × 109 CFU/mL) of Salmonella typhimurium (ST). Blood samples and rectal swabs were obtained and rectal temperature recorded to determine clinical responses and ST shedding. On day 7 postinoculation, 1 pig/pen was euthanized and mesenteric lymph nodes, spleen, and digesta (ileum, cecum, and colon) were sampled to assess ST colonization and translocation. Body weight and feed intake were recorded on day 0, 7, and 21 postinoculation to calculate ADG, ADFI, and G:F. Rectal temperature increased (P < 0.05) 24 h postinoculation and remained elevated at day 6. Serum albumin concentration decreased (P < 0.05), whereas haptoglobin concentration increased (P < 0.05) postinoculation. There was no fiber or Thr effect (P > 0.05) on ST counts in the ileum and cecum, but a fiber × Thr interaction (P < 0.05) was observed in the colon. Supplemental Thr improved (P < 0.05) growth performance in LF- and HF-fed challenged pigs. However, performance of supplemented HF challenged pigs was less than (P < 0.05) supplemented LF challenged pigs. These results suggest that Thr supplemented to meet requirements for high DF and systemic immune challenge was not sufficient to maintain growth performance of pigs fed HF diets and challenged with an enteric pathogen.

Increased lysine: metabolizable energy ratio improves grower pig performance during a porcine reproductive and respiratory syndrome virus challenge

Porcine reproductive and respiratory syndrome virus (PRRSV) reduces grower pig performance. The amino acid (AA) requirements and lysine:metabolizable energy ratio (Lys:ME) of health-challenged pigs for optimum performance are poorly understood. Two experiments were conducted to evaluate the effect of increasing standardized ileal digestible (SID) Lys:ME (g SID Lys per Mcal ME) on growth performance during a PRRSV challenge. In Exp. 1, a total of 379 barrows (51.3 ± 0.3 kg body weight [BW]) were allotted to one of six diets (1.87 to 3.41 Lys:ME) for a 35-d growth study. In Exp. 2, a total of 389 barrows (29.2 ± 0.23 kg BW) were allotted to one of six diets (2.39 to 3.91 Lys:ME) for a 49-d growth study. These isocaloric diets represented 80% to 130% of National Research Council (NRC) SID Lys requirement. For each experiment, pigs were randomly allotted across two barns of 24 pens each with seven to nine pigs per pen (four pens per diet per health status). On day 0, one barn was inoculated with live PRRSV, one barn sham inoculated (control), and all pigs were started on experimental diets. Pen growth performance and feed intake were recorded weekly and gain-to-feed ratio (G:F) was calculated. Breakpoint analysis was used to determine the Lys:ME that maximized average daily gain (ADG) and G:F over the 35 or 49-d test periods for Exp. 1 and 2, respectively. In Exp. 1, increasing Lys:ME increased ADG (quadratic P = 0.01) and G:F (linear and quadratic P = 0.04) in control pigs over 35 d. In PRRSV-infected pigs, ADG and G:F increased linearly with increasing Lys:ME (P < 0.01). The Lys:ME for optimum ADG and G:F during PRRSV challenge was 2.83 and 3.17, respectively, compared to 2.24 and 2.83, respectively, in control pigs using a one-slope broken-line model. In Exp. 2, pigs in the control barn became naturally infected after 21 days post inoculation. Before infection, ADG and G:F increased with increasing Lys:ME in control and PRRSV-infected pigs (linear and quadratic P < 0.05), and optimum ADG and G:F were achieved at 3.02 and 2.92 Lys:ME, respectively, in PRRSV-infected pigs compared to 2.82 and 3.22 Lys:ME, respectively, in control pigs. Over the 49-d period, increasing Lys:ME improved ADG (P < 0.01, linear and quadratic) and G:F (linear P < 0.01) in naturally infected pigs. The response was similar in experimental infection for ADG (P < 0.01, linear and quadratic) and G:F (linear P = 0.01). The optimum ratio for ADG (2.86 vs. 3.12 Lys:ME) and G:F (3.18 vs. 3.08 Lys:ME) were similar between natural and experimental infection. In summary, increasing Lys:ME by 10% to 20% above NRC requirements improved performance and feed efficiency during an experimental and natural PRRSV challenge.

Advances in low-protein diets for swine

Recent years have witnessed the great advantages of reducing dietary crude protein (CP) with free amino acids (AA) supplementation for sustainable swine industry, including saving protein ingredients, reducing nitrogen excretion, feed costs and the risk of gut disorders without impairing growth performance compared to traditional diets. However, a tendency toward increased fatness is a matter of concern when pigs are fed low-protein (LP) diets. In response, the use of the net energy system and balanced AA for formulation of LP diets has been proposed as a solution. Moreover, the extent to which dietary CP can be reduced is complicated. Meanwhile, the requirements for the first five limiting AA (lysine, threonine, sulfur-containing AA, tryptophan, and valine) that growing-finishing pigs fed LP diets were higher than pigs fed traditional diets, because the need for nitrogen for endogenous synthesis of non-essential AA to support protein synthesis may be increased when dietary CP is lowered. Overall, to address these concerns and give a better understanding of this nutritional strategy, this paper reviews recent advances in the study of LP diets for swine and provides some insights into future research directions.

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.

Antibiotic inclusion in the diet did not alter the standardized ileal digestible tryptophan to lysine ratio for growing pigs

Two 21-d experiments were conducted to determine the optimum standardized ileal digestible (SID) Trp:Lys ratio for growing pigs; 1 experiment fed diets supplemented with or without an antibiotic. The primary response variables in both experiments were ADG, ADFI, G:F, and plasma urea N (PUN) concentrations with the optimum SID Trp:Lys ratio detected using broken-line analysis. Experiment 1 evaluated the optimum SID Trp:Lys ratio in growing pigs fed diets supplemented with an antibiotic. This experiment used 120 crossbred pigs that were blocked by sex and initial BW (24.13 ± 2.72 kg) and allotted to 6 SID Trp:Lys ratios in 4 replicates. Dietary treatments were formulated by the addition of crystalline Trp to create 6 SID Trp:Lys ratios (13.08%, 14.06%, 15.04%, 17.00%, 18.95%, and 20.91%) with a constant SID Lys level of 0.655%. As SID Trp:Lys ratios increased, ADG, ADFI, and G:F increased, and PUN concentrations decreased linearly ( < 0.05) and quadratically ( < 0.05). Linear broken-line analysis yielded optimum SID Trp:Lys ratios of 17.93% ( < 0.001) and 16.17% ( = 0.009) for ADG and PUN, respectively, resulting in a mean optimum SID Trp:Lys ratio of 17.05%. Experiment 2 evaluated the optimum SID Trp:Lys ratio in growing pigs fed diets supplemented with or without an antibiotic. It used a total of 324 crossbred pigs (initial BW: 30.81 ± 3.56 kg) that were allotted to 6 SID Trp:Lys ratios in 6 replicates. Dietary treatments were formulated by the addition of crystalline Trp to create 6 SID Trp:Lys ratios (12.52%, 14.86%, 17.20%, 19.54%, 21.88%, and 24.22%) with a constant SID Lys level of 0.67%. As SID Trp:Lys ratios increased, ADG, ADFI, and G:F increased, and PUN concentrations decreased linearly ( < 0.001) and quadratically ( < 0.001) regardless of antibiotic inclusion. There were no differences by the antibiotic treatment in ADG, ADFI, G:F, or PUN concentrations ( > 0.49) and no interactions between antibiotics and Trp:Lys ratios ( > 0.29). When the data for all pigs were pooled for the various Trp:Lys ratios, the optimum SID Trp:Lys ratios for ADG and PUN based on linear broken-line analysis were 14.58% ( < 0.001) and 14.54% ( < 0.001), respectively, resulting in an optimum SID Trp:Lys ratio of 14.56% as the mean of the determined optima for ADG and PUN responses. These results demonstrate that the optimum SID Trp:Lys ratio for 30- to 50-kg growing pigs is not impacted by the dietary inclusion of an antibiotic as long as the diets are formulated on an SID AA basis.

A link between damaging behaviour in pigs, sanitary conditions, and dietary protein and amino acid supply

The tendency to reduce crude protein (CP) levels in pig diets to increase protein efficiency may increase the occurrence of damaging behaviours such as ear and tail biting, particularly for pigs kept under suboptimal health conditions. We studied, in a 2×2×2 factorial design, 576 tail-docked growing-finishing entire male pigs in 64 pens, subjected to low (LSC) vs. high sanitary conditions (HSC), and fed a normal CP (NP) vs. a low CP diet (LP, 80% of NP) ad libitum, with a basal amino acid (AA) profile or supplemented AA profile with extra threonine, tryptophan and methionine. The HSC pigs were vaccinated in the first nine weeks of life and received antibiotics at arrival at experimental farm at ten weeks, after which they were kept in a disinfected part of the farm with a strict hygiene protocol. The LSC pigs were kept on the same farm in non-disinfected pens to which manure from another pig farm was introduced fortnightly. At 15, 18, and 24 weeks of age, prevalence of tail and ear damage and of tail and ear wounds was scored. At 20 and 23 weeks of age, frequencies of biting behaviour and aggression were scored for 10×10 min per pen per week. The prevalence of ear damage during the finisher phase (47 vs. 32% of pigs, P < 0.0001) and the frequency of ear biting (1.3 vs. 1.2 times per hour, P = 0.03) were increased in LSC compared with HSC pigs. This effect on ear biting was diet dependent, however, the supplemented AA profile reduced ear biting only in LSC pigs by 18% (SC × AA profile, P < 0.01). The prevalence of tail wounds was lower for pigs in LSC (13 ± 0.02) than for pigs in HSC (0.22 ± 0.03) in the grower phase (P < 0.007). Regardless of AA profile or sanitary status, LP pigs showed more ear biting (+20%, P < 0.05), tail biting (+25%, P < 0.10), belly nosing (+152%, P < 0.01), other oral manipulation directed at pen mates (+13%, P < 0.05), and aggression (+30%, P < 0.01) than NP pigs, with no effect on ear or tail damage. In conclusion, both low sanitary conditions and a reduction of dietary protein increase the occurrence of damaging behaviours in pigs and therefore may negatively impact pig welfare. Attention should be paid to the impact of dietary nutrient composition on pig behaviour and welfare, particularly when pigs are kept under suboptimal (sanitary) conditions.