Review. Divergent selection for residual feed intake in the growing pig

To view supplementary material for this article, please visit https:/doi.org/10.1017/S175173111600286XThis review summarizes the results from the INRA (Institut National de la Recherche Agronomique) divergent selection experiment on residual feed intake (RFI) in growing Large White pigs during nine generations of selection. It discusses the remaining challenges and perspectives for the improvement of feed efficiency in growing pigs. The impacts on growing pigs raised under standard conditions and in alternative situations such as heat stress, inflammatory challenges or lactation have been studied. After nine generations of selection, the divergent selection for RFI led to highly significant ( P<0.001) line differences for RFI (−165 g/day in the low RFI (LRFI) line compared with high RFI line) and daily feed intake (−270 g/day). Low responses wereobserved on growth rate (−12.8 g/day, P <0.05) and body composition (+0.9mm backfat thickness, P = 0.57; −2.64% lean meat content, P<0.001) with a marked response on feed conversion ratio (−0.32 kg feed/kg gain, P<0.001). Reduced ultimate pH and increased lightness of the meat ( P<0.001) were observed in LRFI pigs with minor impact on the sensory quality of the meat. These changes in meat quality were associated with changes of the muscular energy metabolism. Reduced maintenance energy requirements (−10% after five generations of selection) and activity (−21% of time standing after six generations of selection) of LRFI pigs greatly contributed to the gain in energy efficiency. However, the impact of selection for RFI on the protein metabolism of the pig remains unclear. Digestibility of energy and nutrients was not affected by selection, neither for pigs fed conventional diets nor for pigs fed high-fibre diets. A significant improvement of digestive efficiency could likely be achieved by selecting pigs on fibre diets. No convincing genetic or blood biomarker has been identified for explaining the differences in RFI, suggesting that pigs have various ways to achieve an efficient use of feed. No deleterious impact of the selection on the sow reproduction performance was observed. The resource allocation theory states that low RFI may reduce the ability to cope with stressors,via the reduction of a buffer compartment dedicated to responses to stress. None of the experiments focussed on the response of pigs to stress or challenges could confirm this theory. Understanding the relationships between RFI and responses to stress and energy demanding processes, as such immunity and lactation, remains a major challenge for a better understanding of the underlying biological mechanisms of the trait and to reconcile the experimental results with the resource allocation theory

Management of clinical or subclinical immune activation

Management of clinical or subclinical immune activation. ASAS/ADSA Midwest meetin

Effects of weaning conditions on the evolution of piglet plasma concentration of vitamin E

Weaning causes oxidative stress in piglets. Endogenous and exogenous vitamin E (vit E) participates to theneutralization of pro-oxidant molecules in the organism. This study aimed to analyze the effect of weaning conditions on the evolution of plasma vitamin E concentration on piglets. In trial A, piglets born from 12 litters were weaned at either 21 (W21) or 28 (W28) days of age in optimal (OC) or deteriorated (DC) conditions (n=16 per group). Piglets from OC group originating from 2 litters were housed by 4 (0.39 m2/pig) in cleaned and disinfected pens. Those from DC group originating from 4 litters were housed by 8 (0.20 m2/pig) in dirty pens after a waiting time of 4 h at 20 °C. From 12 to 61 days of age, blood was collected and pigs were weighed weekly and then at 88, 119 and 147 days of age. In trial B, piglets (n=288 from 144 sows) from 16 commercial farms were weaned at 28 days of age. Blood samples were collected when piglets were 26- (on sows and piglets) and 33-days old (on piglets only). In both trials, weaning led to a dramatic drop of the plasma concentration of vit E (P0.05). After weaning, vit E concentration remained stable until 147 days of age. In trial B, piglet plasma concentration of vit E at 26 days of age was not associated with lactating sow vit E concentrations (P>0.05) and was different between farms (P<0.001). The higher plasma concentration of vit E before weaning could be explained by the high vit E content in colostrum and milk leading to the saturation of body fat reserves of the piglet. At weaning, the high requirements of vit E for antioxidant purposes as well as low feed intake, lower fat content of the feed compared to milk and lower activity of enzymes involved in vit E absorption could explain the dramatic drop of plasma vit E. The relatively low concentrations of vit E until slaughter age could reflect an incomplete reconstitution of body reserves. To conclude, weaning led to a drop of plasma concentration of vit E whatever the weaning conditions indicating dramatic changes in vit E statusand metabolism at weaning

The impact of the sanitary environment on health, pubertal development and sex odour of male pigs

Previous studies have shown that the sanitary environment can affect the health and growth of pigs. Theobjective of the present study was to evaluate the effect of a chronic inflammation induced by a degradedsanitary environment on the pubertal development of boars and on boar taint. Boars from a commercialcross line were allocated at 139 (±0.1) days of age (D0) and 81.3 (±0.6) kg of live weight either to good(n=61) or poor sanitary conditions (n=54) for 4 weeks. The poor environment was previously soiled by noncontemporary pigs, poorly ventilated, not cleaned during treatment; the good environment benefited fromreinforced hygiene measures. Inflammatory status and pubertal development were evaluated on D0 and D27by measures on blood samples (blood formula, inflammatory proteins; testosterone, estradiol). Every week,boars were weighed, sampled for saliva (estrone, inflammatory protein CRP) and their rectal temperaturewas measured. Fat was collected on D27 by biopsy and at slaughter (116.7±0.4 kg live weight) to measureboar taint compounds (androstenone, skatole, indole). Pigs in the poor environment were dirtier (P<0.001).The treatment had a slight effect on rectal temperature (D7: 38.4±0.04 vs 38.6±0.06 °C, P<0.001; and D14:38.3±0.04 vs 38.6±0.04 °C, P<0.001) and a marked effect on fat skatole (0.037 vs 0.082 μg/g of pure fat)and indole (0.039 vs 0.14 μg/g) with higher values for boars in the poor environment (P<0.0001). Overall,treatment had no clear impact on the inflammatory status, the pubertal development and androstenone of theboars. However, the soiled increased markedly the dirtiness and fat skatole

Adipose-immune cross-talks in two pig lines divergently selected for feed efficiency - Part 2

Chronic immune stimulation deteriorates adipose tissue accretion through the release of pro- and anti-inflammatory cytokines. In turn, adipokines modulate immune cell activity. It has been shown that pig genetic selection for residual feed intake (RFI), a measure of feed efficiency, influences their energy and protein metabolism, both in healthy and inflammatory states. This study aimed to determine if this selection also interfered with immuneadipose cross-talks. Male and female growing pigs of low (RFI-, n=28) or high (RFI+, n=25) RFI were reared in clean or dirty housing conditions for 6 weeks (n=26 and 27), to obtain healthy and chronically inflamed animals, respectively. Gene expression levels were determined in adipocytes and in cells of the stromal vascular fraction (SVF) of subcutaneous adipose tissue, and in whole blood cells (WB) cultured for 20 h in the absence or presence of lipopolysaccharide (LPS). Levels of adiponectin were greater (P<0.05) in adipocytes of RFI+ than RFI- pigs but did not differ with the line in SVF cells. In WB, there was a greater expression in RFI+ compared with RFI- pigs of adiponectin receptor 1 (AdipoR1, P<0.05) and Transforming Growth Factor-beta (TGF-β, P=0.05 and 0.09) in the 2 culture conditions, and of interleukin (IL)-1 (P<0.05), IL-10 (P=0.06) and Tumor Necrosis Factor-alpha (TNF-α, P<0.01) in LPS-stimulated cultures only (P<0.05). The line effect in WB was mainly due to 5 of the 12 RFI+ females who expressed dramatically greater levels of nearly all tested genes. When excluding them, the AdipoR1 gene was still more expressed in RFI+ pigs (P<0.05) whereas the expressions of AdipoR2, leptin receptor and IL-6 were not affected by the line. Unstimulated WB from dirty pigs expressed more AdipoR1 and TGF-β (P<0.05), and tended to express more Toll-like receptors 2 and 4 (P<0.1). To conclude, RFI- pigs might have a lower sensitivity of immune cells to adiponectin, which exerts regulatory immune functions, and a decreased expression of cytokines suppressing adipogenesis such as IL-1, TNF-α and TGF-β. Research has received funding from the EU FP7 program (PROHEALTH, grant agreement no. 613574)

Impact of poor hygiene on health and performance of pigs divergently selected for feed efficiency

Production diseases impair production efficiency and animal welfare. Pigs with improvedproductive traits are suspected to be more at risk to develop diseases because of a lowercapacity to allocate their nutritional resources for health. The aim of this study was to assesshealth and performance of two pig lines divergently selected for feed efficiency and housed ingood or poor hygiene environment. Poor hygiene is known to induce inflammatory disordersand reduce growth performance. Large-White male and female pigs (n=160) from 80 to 160days of age were included in a 2×2 factorial design comparing 2 lines divergently selected forResidual Feed Intake (low RFI=more efficient and high RFI=less efficient) and housed in 2hygienic conditions (clean (C) vs dirty (D), n=40/group). The experiment was divided in twosuccessive periods: during the challenging period, from Week 0 (W0) to W6, pigs were eitherhoused in C or D conditions; blood was collected at W0, W3 and W6. During the recoveryperiod, from W6 to W12, all pigs were housed in clean conditions. Half of the pigs in eachgroup were euthanized at W6 and the remaining pigs were euthanized at W12 to collect tissueand evaluate body composition. Throughout the experiment, pigs were individually pennedand had free access to a standard growing diet. Body weight and signs of clinical diseases(cough, diarrhea, lameness) were weekly recorded. Blood was collected to assess indicatorsof inflammation (haptoglobin, blood formula) and metabolite concentrations. Prevalenceof pleurisy and pneumonia at slaughter was greater for D than C pigs. Average daily gain(ADG) from W0 to W6 was lower in D than C pigs, and this reduction was greater for thehigh RFI line (-247 g/d) than for low RFI line (-107 g/d). At W3, D pigs exhibited greaterblood haptoglobin and neutrophil contents than C pigs, showing that poor hygiene conditioninduced an inflammatory response. Disparities were observed between the two lines withhigher haptoglobin in high RFI pigs and higher amount of neutrophils in low RFI pigs. FromW6 to W12, ADG and health blood biomarkers did not differ between D and C pigs, suggestingthat pigs had recovered. In conclusion, low RFI pigs were less affected by the environmentalchallenge, which disagrees with our initial hypothesis. Data to be obtained on metaboliteconcentrations and expression levels of genes related to immunity will allow determining ifthe line differences in the ability to cope with this sanitary challenge were related to differencesin resource allocation, immune capacities or growth precocity

Impact of feed restriction and of the hygiene of housing on rabbit performances and health

Introduction: Limiting the post-weaning intake of the young rabbit is now known to improve its resistance to digestive troubles (Gidenne et al. 2012), while the feed conversion is improved. In contrast a poor hygiene of housing is supposed to have a negative impact on performances and health, as demonstrated in the piglet (Le Floc'h et al., 2010). However, these two factors may interact in determining performances and health as recently showed in pig (Pastorelli et al., 2012). We thus aimed to determine the effect of a moderate post-weaning feed restriction in the rabbit to cope with a poor housing hygiene, in terms of growth and health. Methods: Restriction and housing hygiene were studied according to a 2 X 2 factorial design: free intake "F" or restricted "R" at 70% of F, and high vs low hygiene of housing (H and L), and thus corresponded to four groups of 105 rabbits: HF, HR, LF, LR. Rabbits (INRA hybrid line) were fed the same pelleted experimental diet (crude protein 17.4%, ADF=18.4% as fed) and housed in collective cages (5 rab./cage), in two independent breeding rooms (high or low hygiene), from weaning (28d) to slaughter (63d). The intake of the R groups was adjusted three times per week to reach 70% of the intake of F groups within each room. The poor hygiene of housing was obtained by avoiding cleaning one breeding room before and during the experiment. Mortality was checked daily, while morbidity (rabbits having clinical signs of diarrhoea or a very low growth) was checked weekly as for the intake and live weight control Results: No significant interactions were found between the restriction and hygiene, for performances or health status. From 28 to 63d old the mortality rate was relatively low (meanly 11%) suggesting a good health status. Although the number of rabbits was insufficient to reach substantial conclusions about the health impact, we observed that mortality from digestive troubles started one week after weaning (figure 1) and levelled after 7 weeks of age. We detected a significant positive impact of the feed restriction on the mortality rate during the post-weaning period (28-40d old): 1.9 vs 6.2% (P=0.046). For the whole growth period, restriction or low hygiene did not affect significantly the mortality rate, although we recorded the highest mortality for the rabbits fed freely in poor hygiene housing (15/105). In parallel, the morbidity rate was not affected by the restriction strategy, but was surprisingly lower in low hygiene of housing (table 1) during the post weaning period. With a 30% reduced intake the weight gain was meanly reduced by 16% (49.9 vs 41.7 g/d from 28 to 63d old, P<0.001, table 2). Accordingly, the feed conversion was sharply improved for restricted rabbit groups by 16% (2.47 vs 2.11 from 28 to 63d old, P<0.001), as found previously (Gidenne et al., 2012). The level of housing hygiene did not greatly affect the growth, although the post weaning daily gain tended to be lower during the two weeks after weaning (42.6 vs 41.3 g/d, P=0.09). The feed conversion was surprisingly better for rabbit housed in poor hygiene conditions (2.30 vs 2.25 from 28 to 63d old, P=0.03), sourcing from a slightly lower intake (107.0 vs 103.2 g/d, P=0.02). In conclusion, our strategy of feed restriction improved sharply the feed conversion, from 2 weeks after weaning, and was beneficial for the health of the rabbit during the post-weaning period. Our model of hygiene degradation seemed insufficiently stressful to affect the health of the rabbit, and should be further investigated

Impact of hygiene of housing conditions on performance and health of two pig genetic lines divergent for residual feed intake

Pigs selected for high performance may be more at risk of developing diseases. This study aimed to assess the health and performance of two pig lines divergently selected for residual feed intake (RFI) (low RFI (LRFI) v. high RFI (HRFI)) and housed in two contrasted hygiene conditions (poor v. good) using a 2×2 factorial design (n=40/group). The challenge period (Period 1), started on week zero (W0) when 12-week-old pigs were transferred to good or poor housing conditions. At week 6 (W6), half of the pigs in each group were slaughtered. During a recovery period (Period 2) from W6 to W13 to W14, the remaining pigs (n=20/group) were transferred in good hygiene conditions before being slaughtered. Blood was collected every three (Period 1) or 2 weeks (Period 2) to assess blood indicators of immune and inflammatory responses. Pulmonary lesions at slaughter and performance traits were evaluated. At W6, pneumonia prevalence was greater for pigs housed in poor than in good conditions (51% v. 8%, respectively, P<0.001). Irrespective of hygiene conditions, lung lesion scores were lower for LRFI pigs than for HRFI pigs (P=0.03). At W3, LRFI in poor conditions had the highest number of blood granulocytes (hygiene×line, P=0.03) and at W6, HRFI pigs in poor conditions had the greatest plasma haptoglobin concentrations (hygiene×line, P=0.02). During Period 1, growth rate and growth-to-feed ratio were less affected by poor hygiene in LRFI pigs than in HRFI pigs (hygiene×line, P=0.001 and P=0.02, respectively). Low residual feed intake pigs in poor conditions ate more than the other groups (hygiene×line, P=0.002). Irrespective of the line, fasting plasma glucose concentrations were higher in poor conditions, whereas fasting free fatty acids concentrations were lower than in good conditions. At the end of Period 2, pneumonia prevalence was similar for both housing conditions (39% v. 38%, respectively). During Period 2, plasma protein concentrations were greater for pigs previously housed in poor than in good conditions during Period 1. Immune traits, gain-to-feed ratio, BW gain and feed consumption did not differ during Period 2. Nevertheless, at W12, BW of HRFI previously housed in poor conditions was 13.4 kg lower than BW of HRFI pigs (P<0.001) previously housed in good conditions. In conclusion, health of the most feed efficient LRFI pigs was less impaired by poor hygiene conditions. This line was able to preserve its health, growth performance and its feed ingestion to a greater extent than the less efficient HRFI line

Lysine, threonine and tryptophan postprandial metabolism in LPS challenged growing pigs

Sanitary challenges and/or immune system activation are associated with decreased voluntary feed intake,increased metabolic rate and energy expenditure, and alterations on nutrient utilization in growing pigs.As a consequence, animals weight gain and feed efficiency are negatively impacted in such conditions.The aim of this study was then to evaluate the effects of an inflammatory challenge caused by repeatedinjections of Escherichia coli lipopolysaccharide (LPS) on lysine, threonine and tryptophan postprandialmetabolism. Fourteen growing pigs fitted with a jugular catheter were housed in a temperature-controlledroom in which ambient temperature was maintained constant at 24°C. The experimental period lasted 17 daysthat was subdivided in a seven days period before and a 10 days period during the inflammatory challengethat consisted in five repeated injections of LPS at two days intervals. The initial dose of 30 μg/kg of bodyweight was increased by 12% at each subsequent injection to circumvent adaptive endotoxin resistance tothe repeated inflammatory stimuli. Before the LPS- challenge (baseline), and 24h after the second (T1) andthe fourth (T2) LPS injections, 300 g of feed was given to pigs previously fasted overnight and serial bloodsamples were taken over four-hours to measure plasma amino acids concentrations. Amino acids postprandialconcentrations were analyzed using the linear MIXED procedure of SAS including the fixed effects of timepoints (baseline, T1 or T2). Relative to baseline, postprandial concentrations of lysine were lower at T1and greater at T2. In addition, the LPS-challenge induced a long-lasting (at T1 and T2) reduction in plasmapostprandial concentrations of threonine and tryptophan. Firstly, these results suggest a short-term increasedutilization of lysine to be used as energy source during the LPS-challenge. Then, lysine demand decreasesin association with a lower protein synthesis for growth. Secondly, they evidence an increased threonineand tryptophan metabolic demand to support the requirements of the immune response. For instance, theimmune system activation induces the synthesis of acute phase proteins that, in turn, have greater amounts ofthreonine and tryptophan in their compositions. Finally, our evidences that an inflammatory challenge causedby LPS leads to significant changes on amino acids metabolism and partitioning. induces significant changesin the postprandial metabolism of growing pigs. These findings may contribute to redefine pigs nutritionalrequirements during inflammatory and/or immune challenges

Identification of genes which are associated with production diseases in pigs and chickens

Production disease in pigs and chickens is caused by a variety of different pathogens, mainly enteric and respiratory, which may result in significant economic losses. Other factors such as stress, poor husbandry and nutrition can also contribute to an animal’s susceptibility to disease. Molecular biomarkers of production disease could be of value by improving diagnosis and risk analysis to determine best practice with an impact on increased economic output and animal welfare. Over 480 chicken tissue samples from countries including Belgium, Spain and the UK, and over 115 pig samples from Belgium, Spain, France and Ireland were available. Samples included lung, intestine, mesenteric and tracheobronchic lymph node, bone, cartilage and sciatic nerve. Two types of software were used to analyse the microarray data; Genespring was used for statistical analysis and visualisation of transcriptomic data and Cytoscape was used to visualise molecular interaction networks between genes. Results indicated that panels of genes may identify a broad spectrum of infectious disease in chickens, whereas combinations of upregulated genes may be used as biomarkers of specific pathogens such as Escherichia coli or Eimeria. Pigs from two lines (RFI high and low) were kept in dirty environments which had the same bedding and clean environments which had fresh bedding. A greater difference was observed in the number of genes differentially expressed in the RFI high pigs than RFI low pigs. Pathway analysis from both chicken and pig experiments indicated that many networks were affected including those involved in regulating the immune-system. Whilst a large number of studies have been carried out in human medicine, further work is needed to identify molecular biomarkers in veterinary medicine and in particular those associated with production disease in the pig and poultry livestock industry