Review: Future consequences of climate change for European Union pig production.

Climate change is already a reality for livestock production. In contrast to the ruminant species, little is known about the impacts and the vulnerability of pig European Union (EU) sector to climate warming. This review deals with the potential and the already measurable effects of climate change in pig production. Based on evidences published in the literature, climate change may reduce EU pig productivity by indirectly reducing the availability of crops usually used in pig feeding, spreading the vector or pathogen to new locations and increasing the risk of exposure to cereals contaminated with mycotoxins; and directly mainly by inducing heat stress and increasing the animal's susceptibility to various diseases. Provision of realistic projections of possible impacts of future climate changes on EU pig sector is a prerequisite to evaluate its vulnerability and propose effective adaptation strategies. Simulation modelling approach is the most commonly used approach for exploring the effects of medium or long-term climate change/variability in pig production. One of the main challenges for this modelling approach is to account for both direct and indirect possible effects but also to uncertainties in parameter values that substantially increase the uncertainty estimates for model projections. The last part of the paper focus on the main issues that still need to be overcome for developing a decision support tools for simulating the direct and indirect effect of climate change in pig farms.

Effects of the level of sugarcane molasses on growth and carcass performance of Caribbean growing pigs reared under a ground sugarcane stalks feeding system.

The influence of the level of sugarcane (SC) molasses on growth performance, carcass traits, and meat quality in Creole (CR) growing pigs fed with ground sugarcane stalks (GCS)-based diet was studied in a mixed farming system context. The aim of the study was to optimize the growth performance of CR pigs with SC-molasses as an energy source in this unconventional feeding. A total of 32 CR pigs were used from 30 to 60 kg of body weight (BW). The experimental dietary treatments consisted of four levels of inclusion of SC-molasses (200, 400, 600, and 800 g DM/d/pig) into a GCS diet, for diets 1, 2, 3 and 4 respectively. The GCS allowance was based on live BW (170 g/kg BW/d) and the diets were supplemented with a soya-bean meal supplement (350 g/d of a 49.2% CP and 16.6 MJ DE/kg). All the pigs were slaughtered at 60 kg BW. Increasing the level of molasses did not affect (p > 0.05) average BW gain (254 g/d), CP intake (154 g/d) and sugar extraction rate from the total ration (85%). A gradual inclusion of molasses in a GCS-based diet did not affect the carcass and meat quality of CR pigs. In conclusion, molasses supplementation does not allow the increase of growth performance in GCS fed pigs.

Transient effect of single or repeated acute deoxynivalenol and zearalenone dietary challenge on fecal microbiota composition in female finishing pigs.

Mycotoxins are a major contaminant of pig feed and have negative effects on health and performance. The present study investigated the impact of single or repeated acute challenges with a diet naturally contaminated with deoxynivalenol (DON) and zearalenone (ZEN) on growth performances of finishing pigs and their fecal microbiota composition. A total of 160 pigs (castrated males and females) in two successive batches were randomly divided into four experimental groups of 40 pigs each. The control group received a control finisher diet from 99 to 154 days of age. Challenged groups were subjected to a 7-day acute challenge by being fed a DON- and ZEN-contaminated diet (3.02 mg DON/kg feed and 0.76 mg ZEN/kg feed) at 113 days (group DC), 134 days (group CD) or both 113 and 134 days (group DD). Microbiota composition was analyzed via 16S rRNA sequencing from fecal samples collected from the 80 females at 99, 119, 140 and 154 days. Challenged pigs (i.e. groups DC, CD and DD) reduced their average daily feed intake by 25% and 27% (P < 0.001) and feed efficiency by 34% and 28% (P < 0.05) during the first and second mycotoxin exposure, respectively. Microbiota composition was affected by mycotoxin exposure (P = 0.07 during the first exposure and P = 0.01 during the second exposure). At the family level, mycotoxin exposure significantly (P < 0.05) decreased the relative abundances of Ruminococcaceae, Streptococcaceae and Veillonellaceae and increased that of Erysipelotrichaceae at both 119 and 140 days of age. After the 7-day DON/ZEN challenge, the relative abundance of 6 to 148 operational taxonomic units (OTUs) differed among the treatment groups. However, none of these OTUs changed in all treatment groups. Using 27 functional pathways, pigs exposed to DON/ZEN challenges could be distinguished from control pigs using sparse partial least squares discriminant analysis, with a 15% misclassification rate. Regarding the functionality of these predictors, two pathways were involved in detoxifying mycotoxins: drug metabolism and xenobiotic metabolism by cytochrome P450. In challenged pigs, microbiota composition returned to the initial state within 3 weeks after the end of a single or repeated DON/ZEN challenge, highlighting the resilience of the gut microbiome. The feeding and growth performances of the pigs during challenge periods were significantly correlated with biological pathways related to health problems and modifications in host metabolism. To conclude, short-term DON/ZEN challenges resulted in transient modifications in the composition and functions of fecal microbiota.

Effect of sugarcane diets and a high fibre commercial diet on fresh meat and dry-cured ham quality in local Caribbean pigs.

The effects sugar cane (SC) diets and a milling by product diet on meat quality characteristics of fresh meat and dry-cured ham were studied on a total of 48 Creole (CR) pigs. Pigs were fed with a control soya-bean meal corn diet (C1), a soya-bean meal wheat diet (C2), a SC fresh juice diet (SC-J), or a ground cane diet (SC-G). Average BW gain was 657, 530, 546, and 200g/d for diets C1, C2, SC-J and SC-G, respectively. Lean cuts (i.e., ham and loin) were significantly higher in SC-G than in C1 pigs (472 vs. 424g/kg; P<0.01); intermediate values were found for C2 and SC-J pigs (427 and 412g/kg, respectively). The ultimate pH in LD muscle was lower in SC-J than the other groups (5.44 vs. 5.65; P<0.01). The intra muscular fat (IMF) content in LD was significantly higher in SC-J diet and lower in SC-G diet (1.9% and 1.0%, respectively); intermediates values were found for C1 and C2 diets (1.4% on average). Ham weight losses during 6 months drying period were lower for SC-G fed pigs (9.7% vs. 12.4%; P<0.05) whereas weight losses during the 12 months drying period were not affected by diet. The TBA value in dry-cured ham was not affected by diet (P>0.05) whereas the fatty acids profiles of subcutaneous fat in SC-J and SC-G pigs contained more mono-unsaturated and less polyunsaturated fatty acids than in C1 and C2 groups. Significant effects of dietary treatment were found for dry-cured ham sensory quality parameters.

A comparison of carcass and meat quality characteristics of Creole and Large White pigs slaughtered at 90kg BW.

The effect of breed in combination with sex (gilts or barrows) on carcass composition and meat quality characteristics were studied in two replicates involving a total of 40 Creole (CR) and 40 Large White (LW). This trial was conducted in the experimental facilities of INRA in Guadeloupe (French West Indies, 16° Lat. N. and 61° Long. W). All the pigs were slaughtered at about 90kg BW. No interaction between breeds and sex was found for all criteria studied. Carcass dressing weight was higher in CR than in LW (832 vs. 810g/kg, P<0.001) in connection with their lower internal organs weight (34.0 vs. 41g/kg; P<0.001). Fat cuts weight (i.e., back and leaf fat) was higher in CR than in LW (192 vs. 90g/kg; P<0.001). Creole pigs showed higher intramuscular fat percentage (IMF), higher percentage of monounsaturated fatty acids (MUFA) and lower percentage of polyunsaturated fatty acids (PUFA) in Longissimus dorsi (LD) muscle than LW pigs (4.72% vs. 2.29%, 50.2% vs. 45.0% and 7.9% vs. 13.8%, respectively). Whatever the muscle considered the ultimate pH was higher (P<0.05) in CR than in LW pigs. The drip and cooking losses of LD muscle were lower in CR than in LW (8.2% vs. 9.7% and 28.9% vs. 30.1%, respectively; P<0.05). Whatever the breed, the females were leaner than barrows (P<0.01) but the effect of sex was significant only on a few parameters.

Genetic parameters for thermoregulation and production traits in lactating sows reared in tropical climate.

The objective of this study was to estimate the genetic parameters for thermoregulation traits and the relationships with performance of Large White lactating sows reared in a tropical humid climate. The thermoregulation traits were rectal temperature (RT), cutaneous temperature (CT) and respiratory rate (RR) during lactation measured in the afternoon (1200 h) and in the morning (0700 h). The production traits were sow's average daily feed intake (ADFI), litter BW gain (LBWg) and sow's proportion of BW change between farrowing and weaning (BWc). Complete data included 931 lactating performance on 329 Large White sows from the INRA experimental unit in Guadeloupe (French West Indies). Random regression models using linear spline functions were used for longitudinal data (RT, CT, RR and daily feed intake). Results showed that when ignoring values at the beginning and the end of lactation, the traits studied can be treated as the same trait throughout days of lactation, with fairly constant heritability and variance. However, largest heritabilities and genetic variances were estimated in mid-lactation. Heritability estimates on average performance during lactation were low to moderate for thermoregulation traits (0.35±0.09 for RT, 0.34±0.12 for CT and 0.39±0.13 for RR). Heritability estimates for production traits were 0.26±0.08 for ADFI, 0.20±0.07 for BWc and 0.31±0.09 for LBWg. Significant genetic correlations between thermoregulation traits and production traits were only obtained for ADFI and RR (0.35±0.12). From this study it can be concluded that thermoregulation traits are heritable, indicating that there are genetic differences in heat stress tolerance in lactating Large White sows.

Interactions between sire family and production environment (temperate vs. tropical) on performance and thermoregulation responses in growing pigs.

The aim of this study was to evaluate the effect of 2 climatic environments (temperate [TEMP] vs. tropical humid [TROP]) on production and thermoregulation traits in growing pigs. A backcross design involving Large White (LW; heat sensitive) and Creole (CR; heat tolerant) pigs was studied. The same 10 F LW × CR boars were mated with related LW sows in each environment. A total of 1,298 backcross pigs ( = 634 pigs from 11 batches for the TEMP environment and = 664 pigs from 12 batches for the TROP environment) were phenotyped on BW (every 15 d from wk 11 to 23 of age), voluntary feed intake (ADFI, from wk 11 to 23), backfat thickness (BFT; at wk 19 and 23), skin temperature (ST; at wk 19 and 23), and rectal temperature (RT; at wk 19, 21, and 23). The feed conversion ratio was computed for the whole test period (11 to 23 wk). The calculation of the temperature-humidity index showed an average difference of 2.4°C between the TEMP and TROP environments. The ADG and ADFI were higher in the TEMP environment than in the TROP environment (834 vs. 754 g/d and 2.20 vs. 1.80 kg/d, respectively; < 0.001). Body temperatures were higher in the TROP environment than in the TEMP environment (35.9 vs. 34.8°C for ST and 39.5 vs. 39.3°C for RT, respectively; < 0.001). Most of the studied traits (i.e., BW, BFT, ADG, ADFI, and RT) were affected by sire family × environment interactions ( < 0.05), resulting in "robust" and "sensitive" families. Our results show a family dependency in the relationships between heat resistance and robustness, suggesting the possibility of finding genotypes with high production and low heat sensitivity. Further research is needed to confirm the genetic × environment interaction and to detect QTL related to heat tolerance.

Review: divergent selection for residual feed intake in the growing pig.

This 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 were observed on growth rate (-12.8 g/day, P<0.05) and body composition (+0.9 mm 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.

Effects of exposure to high ambient temperature and dietary protein level on sow milk production and performance of piglets.

The effects of high ambient temperature and level of dietary heat increment on sow milk production and piglet performance over a 28-d lactation were determined in 59 multiparous crossbred Large White x Landrace pigs kept at a thermoneutral (20 degrees C) or in a hot (29 degrees C) constant ambient temperature. Experimental diets fed during lactation were a control diet (NP; 17.6% CP) and two low-protein diets obtained by reduction of CP level (LP; 14.2% CP) or both reduction of CP and addition of fat (LPF; 15.2% CP); the NE:ME ratio was 74.3, 75.6, and 75.8% for NP, LP, and LPF diets, respectively. All diets provided 0.82 g of digestible lysine/MJ of NE, and ratios between essential AA and lysine were above recommendations. Creep feed was provided after d 21 of lactation. Reduction of CP level did not influence (P > 0.10) milk production, milk composition, or piglet performance. Despite higher nursing frequency (39 vs 34 sucklings per day), milk production decreased (P < 0.01) from 10.43 to 7.35 kg/d when temperature increased from 20 to 29 degrees C. At d 14, DM (18.6 vs 18.1%) and energy (4.96 vs 4.75 MJ/kg) contents in milk tended (P = 0.09) to be higher in sows kept at 29 degrees C. Over the 28-d lactation, piglet BW gain and BW at weaning decreased (P < 0.01) from 272 to 203 g/d and 9.51 to 7.52 kg, respectively, when temperature increased from 20 to 29 degrees C. Daily creep feed intake over the 4th wk of lactation was higher (P < 0.01) at 29 degrees C than at 20 degrees C (388 vs 232 g/litter, respectively), which was reflected in a greater increase in BW gain between wk 1 to 3 and wk 4 at the higher temperature (147 vs 130%); BW gain between weaning and d 14 postweaning was higher (P < 0.05) for piglets originating from sows kept at 29 degrees C (280 vs 218 g/d). In connection with their lower growth rate, DM (31.2 vs 33.0%), protein (15.5 vs 16.0%), lipid (12.3 vs 13.9%), and energy (8.39 vs 9.09 kJ/g) contents in weaned, slaughtered piglets were lower (P < 0.01) at 29 than at 20 degrees C. In conclusion, modification in the CP:NE ratio in order to decrease dietary heat increment did not affect milk production and piglet performance in thermoneutral or hot climatic conditions. Our results confirm the negative effect of high ambient temperatures on milk yield and emphasize the importance of creep feed supply to improve pre- and postweaning growth of piglets in these conditions, especially when weaning occurs after 3 wk of age.

Effects of exposure to high ambient temperature and dietary protein level on performance of multiparous lactating sows.

Fifty-nine multiparous Large White x Landrace sows were used to determine the effects of high ambient temperature and level of dietary heat increment on lactation and reproductive performance. During a 28-d lactation and the 14-d postweaning period, ambient temperature was maintained constant at 20 or 29 degrees C. Experimental diets fed during lactation were a control diet (NP; 17.6% crude protein) and two low-protein diets obtained by reduction of CP level (LP; 14.2% CP) and both reduction of CP and addition of 4% fat (LPF; 15.2% CP); the NE:ME ratio was 74.3, 75.6, and 75.8% for NP, LP, and LPF diets, respectively. All diets provided 0.82 g of digestible lysine/MJ of NE, and ratios between essential amino acids and lysine were above recommendations. During the ad libitum period (i.e., between d 7 and 27 of lactation), ADFI and NE intake decreased, respectively, from 7.63 to 4.22 kg and 82.0 to 43.3 MJ of NE when the temperature increased from 20 to 29 degrees C. Exposure to 29 degrees C reduced litter BW gain (2,152 vs 2,914 g/d) and increased lactation BW loss (34 vs 16 kg) but increased postweaning BW gain (2 vs - 4 kg). Expressed per kilogram of feed intake, water intake increased from 4.0 to 7.5 L between 20 and 29 degrees C. Compared with the NP diet, low-CP diets (LP or LPF) maintained performance and reduced total N excretion (-22.5%) in lactating sows at thermoneutrality and attenuated the negative effects of high temperature on NE intake and BW loss (40.9 vs 47.9 MJ of NE/d and 41 vs 30 kg for NP and LP + LPF diets, respectively). Temperature and diet composition did not affect the reproductive performances, and the mean weaning-to-estrus interval was 4.9 d. The respiratory rate and skin, udder, and rectal temperatures increased markedly at 29 degrees C (105 vs 33 breaths per min and 37.8 vs 36.1 degrees C, 38.9 vs 38.2 degrees C, and 39.5 vs 38.8 degrees C, respectively) without any effect of diet. In conclusion, low heat increment diets (i.e., with reduced CP/NE ratio) did not affect lactation performance of sows at thermoneutrality and attenuated the effects of high ambient temperature on energy intake and BW loss. At any ambient temperature, N excretion can be markedly reduced.

Effects of dietary fiber on performance of multiparous lactating sows in a tropical climate.

Sixty-two multiparous Large White sows were used to determine the effect of dietary fiber level on lactation performance according to season under conditions of a humid tropical climate. This experiment was conducted in Guadeloupe (West French Indies, lat 16 degrees N, long 61 degrees W) between October 1999 and January 2001. Two seasons were distinguished a posteriori from climatic measurements parameters continuously recorded in the farrowing room. During the warm season, ambient temperature and relative humidity averaged 25 degrees C and 86.8%, respectively. The corresponding values for the hot season were 27.5 degrees C and 83.5%. Experimental diets fed during lactation were a control diet (C; 14% neutral detergent fiber) and a high-fiber diet (HF; 20% neutral detergent fiber) obtained by substitution of wheat middlings by wheat bran. The two diets were formulated to provide the same ratios between essential amino acids and lysine and between lysine and net energy. No interaction between season and diet composition was found for all criteria studied. Over the 28-d lactation, average daily feed intake (ADFI) was lower and body weight loss was higher (P < 0.001) during the hot season compared to the warm season (3,447 vs 4,907 g/d and 33 vs 17 kg, respectively). The number of stillborn piglets was higher (P < 0.05) during the hot season than during the warm season (2.0 vs 1.1 piglets, respectively). Litter growth rate and mean BW of piglets at weaning were reduced (P < 0.01) during the hot season vs the warm season (2.1 vs 2.3 kg/d and 7.7 vs 8.3 kg, respectively). The ADFI was similar for both diets and digestible energy (DE) intake tended to be lower (P = 0.06) with the HF diet (54.9 vs 59.3 MJ of DE/d for C sows) in relation with its lower DE concentration. The body weight loss was greater (P < 0.01) for HF sows than for C sows (30 vs 21 kg). Compared with the C diet, the HF diet increased (P < 0.05) litter growth rate and piglet body weight at weaning (2.3 vs 2.1 kg/d and 8.3 vs 7.7 kg/d for HF vs C, respectively). Season and diet composition did not affect the weaning-to-estrus interval. In conclusion, the hot season in humid tropical climates, which combines high levels of temperature and humidity, has a major negative effect on the performance of lactating sows.

Effect of ambient temperature on mammary gland metabolism in lactating sows.

Two groups of three multiparous Large White x Landrace sows were used to investigate the direct effect of ambient temperature on mammary gland metabolism. Sows from the first group were exposed to temperatures of 28 degrees C between d 8 and 14 of lactation, and 20 degrees C between d 15 and 21; treatments were reversed in the second group. Four to six d after farrowing, an ultrasonic blood flow probe was implanted around the right external pudic artery and catheters were fitted in the right anterior mammary vein and in the carotid artery. After surgery all sows were fed 3.8 kg/d of a lactation diet. The arteriovenous (AV, mg/L) plasma samples were obtained every 30 min between 0915 and 1545 on d 5 of exposure to ambient temperature; the same day, milk samples were collected at 1630. Additional arterial samples were obtained between 1000 and 1100 on d 1, 4, and 6 of exposure. Milk yield was estimated from the body weight gain of the litter. Elevated temperature tended to reduce BW loss (2.44 vs 1.82 kg/d, P < 0.10), but did not affect milk yield (11.0 kg/d). Glucagon and leptin arterial concentrations increased (12 and 8%, respectively; P < 0.10), but thyroxin and triiodothyronine concentrations decreased (26 and 16%, respectively; P < 0.01) between 20 and 28 degrees C. Expressed as a percentage of total nutrients, AV difference, glucose, amino acids, triglycerides (TG), free fatty acids, and lactate A-V differences represented 60, 20, 11, 8, and 1%, respectively. Exposure to 28 degrees C increased the extraction rate of glucose, TG, and a-amino acid N (13, 8, and 2.5%, respectively; P < 0.10). The extraction rates of essential and nonessential amino acids were not affected by temperature. The right pudic artery mammary blood flow increased (872 vs 945 mL/min, P < 0.05) between 20 and 28 degrees C, whereas milk yield was unaffected by temperature. It is suggested that this apparent inefficiency of the sow mammary gland in hot conditions could be related to an increase of proportion of blood flow irrigating skin capillaries in order to dissipate body heat.

Measurement of blood flow through the mammary gland in lactating sows: methodological aspects.

Two replicates of three multiparous crossbred Large White x Landrace lactating sows were used to develop a technique for the continuous direct measurement of the blood flow through the mammary gland using transit time ultrasound. Four to six days after farrowing, an ultrasonic transit time flow probe was implanted around the right external pudic artery in order to measure the short-term variations of mammary blood flow through this vessel in response to postural change (standing vs lying), meal distribution, hand-milking, and weaning. After surgery, all sows were fed 3.8 kg/d of a lactation diet and housed either at 20 or 28 degrees C. The implantation of the ultrasonic blood flow probe was successful in all six operated sows. Postmortem examination did not indicate the presence of infection, any collateral bypassing the flow probe, or a reduction of artery diameter. The right pudic artery mammary blood flow (PMBF) was measured for 8.5 h over two periods of three days (d 11 to d 13 and d 18 to d 20 of lactation). The PMBF averaged 910 +/- 238 mL/min but was variable within 1 d. Compared with the lying position, PMBF was decreased (- 6%, P < 0.05) when sows were standing. Between 0 to 15 and 16 to 30 min after oxytocin injection (t = 0) and hand-milking, PMBF remained constant (P = 0.05; 801 vs 767 mL/ min) and increased (P = 0.02), respectively, in comparison with the mean calculated over the preceding 30-min period (982 vs 784 mL/min). The PMBF increased (P < 0.05) after meal distribution and reached a peak 65 min later (i.e., 980 mL/min). The PMBF decreased regularly after separation of piglets at weaning; at 8 and 16 h after weaning, PMBF was 60 and 40% of the value recorded before weaning, respectively. Assuming that PMBF drains one-quarter of the whole mammary gland, it can be calculated that blood flow through the entire mammary gland averages 3.6 L/min and that about 470 L of blood are required to produce 1 kg of milk. The proposed methodology constitutes a new technique to measure direct mammary blood flow and its short-term factors of variation.

Effects of ambient temperature on energy and nitrogen utilization in lipopolysaccharide-challenged growing pigs.

High ambient temperature impacts feed intake, growth, and nutrient utilization in pigs. However, little is known on its effects on immune function and, therefore, on how or if it could modulate the utilization of nutrients in pigs exposed to an inflammatory challenge. The aim of this study was to evaluate the effects of high ambient temperature on energy and nitrogen utilization in pigs submitted to repeated injections of Escherichia coli lipopolysaccharide (LPS). Twenty-eight catheterized and pair-housed female pigs (55 kg BW) were assigned to 1 of the 2 thermal conditions: thermoneutrality (TN, 24°C) or high ambient temperature (HT, 30°C). Within each condition, pigs had a 2-wk adaptation period in climatic-controlled rooms and then were transferred to open-circuit respiration chambers. Pigs remained in respiration chambers for a period of 18 d, which was divided into a 7-d period without LPS (baseline) and a subsequent 11-d period with LPS administration (LPSperiod). The interaction between ambient temperature and period was not significant for most of the traits studied. At baseline, pigs kept at HT had lower ADFI (1,500 vs. 2,003 g/d; P < 0.01) and ADG (449 vs. 684 g/d; P = 0.01) and similar nutrient digestibility compared with those kept at TN. Pigs kept at HT also consumed less ME (1,651 vs. 2,170 kJ · kg BW(-0.60) · d(-1); P = 0.01) and produced less heat (1,146 vs. 1,365 kJ · kg BW(-0.60) · d(-1); P < 0.01) than those kept at TN. Furthermore, HT pigs retained less protein and fat than TN pigs (-61 and -57 g/d, respectively; P < 0.01 and P = 0.01). The LPS challenge reduced (P < 0.01) nitrogen (-13.7 and -7.4 g/d) and ME intake (-594 and -335 kJ · kg BW(-0.60) · d(-1)) in TN and HT conditions, respectively; fecal digestibility of nutrients was not affected by LPS. During the LPSperiod, total heat production (HP) was decreased (P < 0.01) in both TN and HT groups (-190 and -104 kJ · kg BW(-0.60) · d(-1), respectively), in connection with the lower short-term thermic effect of feeding (P = 0.01) and resting HP (P < 0.01). In addition, the LPS induced a reduction in protein (P < 0.01) and fat deposition (P = 0.01) in pigs kept at TN (-79 and -73 g/d, respectively) and at HT (-41 and -44 g/d, respectively). In conclusion, our study confirms that high temperature reduces feed intake, growth performance, and HP. Moreover, our results evidence that irrespective of thermal condition, an inflammatory LPS challenge affects energy utilization through changes in ME intake and maintenance requirements.

Selection for residual feed intake in growing pigs: effects on sow performance in a tropical climate.

The aim of the study was to evaluate the consequences of a divergent selection for residual feed intake (RFI) during growth in a temperate environment (TEMP) on sow performance in a tropical environment (TROP). Sows came from a selection experiment conducted at INRA in which 2 lines were selected for larger (RFI(+)) or smaller (RFI(─)) feed intake than predicted from performance. In the first analysis, a subsample of data obtained in TROP conditions (49 lactations) was compared to those obtained in TEMP on their sibs mated with the same boars (54 lactations). In the second analysis, data obtained in the TROP environment (82 lactations) were analyzed for testing the effect of season (warm vs. hot) and line on sow performance. Except for the lactation length, the interaction between line and climatic environment was not significant for the others traits (P > 0.05). The ADFI expressed per kilogram of litter BW gain tended to be higher in the RFI(+) line bred in the TROP environment (P = 0.080), together with piglet BW at weaning, which tended to be lower (P = 0.080). The ADFI was lower in TROP than in TEMP (4.56 vs. 5.86 kg/d; P = 0.003), with negative consequence on litter BW gain and maternal BW loss. The RFI(-) sows tended to eat less feed than RFI(+) sows during lactation (4.55 vs. 5.86 kg/d; P = 0.099). Litter BW at weaning was higher in the RFI(─) line. The RFI(─) sows ate significantly less feed to produce 1 kg of litter than the RFI(+) sows and tended to lose a larger amount of BW during lactation than the RFI(+) sows (2.40 vs. 3.02 kg/kg and -0.66 vs. -0.39 kg/d, respectively, P < 0.10). Whatever the line, ADFI was reduced by about 21% in the hot season (P < 0.05). Litter BW gain was depressed (P < 0.05) in the hot season (1.72 vs. 2.08 kg/d in the warm season; P = 0.023). Lactation maternal BW loss tended to increase in the hot season (1.10 vs. 0.71 kg/d in the warm season; P = 0.016), but back fat loss remained constant (P = 0.295). In the TROP environment, the amount of feed required to produce 1 kg of litter was not influenced by the line in the warm season (2.53 kg/kg on average; P = 0.99), but it tended to be lower in the RFI(─) line when compared to the RFI(+) line in the hot season (2.06 vs. 3.45 kg/kg; P = 0.050). This higher apparent efficiency in RFI(─) sows was mainly related to greater maternal body reserve mobilization (i.e., BW and back fat losses). In conclusion, selection for low RFI during growth in a TEMP environment did not impair sow and litter performance in tropical conditions.

Banana meal for feeding pigs: digestive utilization, growth performance and feeding behavior.

The main objective of the present work was to determine the nutritional value and the strategies of using green banana meal (BM) in growing pigs. Two trials involving a total of 96 growing pigs were designed to study the effect of the harvest stage on the nutritional and energy values of BM (trial 1) and to evaluate the consequence of feeding gradual levels of BM on growth performance and feeding behavior in growing pigs (trial 2). In trial 1, the digestive utilization of three diets including 40% BM were compared with a control (C) soybean meal-corn diet in two batches of 12 pigs. BM was obtained from fruits harvested at 750 degrees-days (DD; early harvesting stage), 900 DD (normal harvesting stage) and 1150 DD (late harvesting stage). In trial 2, 72 Large White pigs were grouped in pens of nine animals and were given ad libitum access to one of the four dietary treatments (two pens/diet) differing from the rate of inclusion of 900 DD BM (0%, 20%, 40%, 60%). The estimated energy apparent digestibility coefficients of BM increased with the harvest stage (75.5%, 80.7% and 83.2% for BM at 750, 900 and 1150 DD, respectively). Digestible energy and metabolizable energy values were higher for BM at 1150 DD (13.56 and 13.05 MJ/kg DM, respectively) than at 900 DD (13.11 and 12.75 MJ/kg DM, respectively) or at 750 DD (12.00 and 11.75 MJ/kg DM, respectively). In trial 2, average daily gain and feed conversion ratio were not affected (P>0.05) by the rate of BM inclusion (822 g/day and 2.75 kg/kg on average, respectively). Feed intake and feeding behavior parameters were not significantly influenced by the dietary treatments except for the rate of feed ingestion with a lower value for the diet with 40% of BM (27.4 v. 32.2 g/min on average; P<0.01) when compared with the other diets. Results of this study indicate that the energy value of BM increases with the harvest stage and that BM can be incorporated up to 60% in growing finishing pig diets.

Effect of thermal heat stress on energy utilization in two lines of pigs divergently selected for residual feed intake.

Castrated males from 2 lines of purebred French Large White obtained from a divergent selection experiment for their residual feed intake (RFI) over 7 generations were measured for their energy utilization during thermal acclimation to increased ambient temperature. The RFI(+) line consumed more feed than predicted from its performance, whereas the RFI- line consumed less feed. Each pig was exposed to 24°C for 7 d (P0) and thereafter to a constant temperature of 32°C for 3 consecutive periods of 7 d (P1, P2, P3). Feed intake, feeding behavior parameters, digestibility, components of heat production (HP; measured by indirect calorimetry in respiration chambers), and energy, nitrogen, fat, and water balance were measured in pigs offered feed and water ad libitum and individually housed in respiratory chambers. Two identical respiratory chambers were simultaneously used, and 5 pigs of each line were measured successively. Whatever the trait, the interaction between line and period was not significant (P > 0.10). On average, ADFI was greater in the RFI+ than in the RFI- line (1,945 vs. 1,639 g/d; P = 0.051) in relation to an increase of the mean size of each feeding bout (128 vs. 82 g/visit; P < 0.001). There was no line effect on nutrient and energy digestibility. Total HP tended to be greater in RFI+ than in RFI- lines (1,279 vs. 1,137 kJ·kg BW-0.60·d-1; P = 0.065), which tended to retain more energy (968 vs. 798 kJ·kg BW-0.60·d-1; P = 0.050). The sensible heat loss was greater in RFI+ compared with the RFI- line (644 vs. 560 kJ·kg BW-0.60·d-1; P = 0.020). The RFI+ pigs consumed more water (+981 vs. 657 g·kg BW-0.60·d-1; P = 0.085) and produced more urine (589 vs. 292 g·kg BW-0.60·d-1; P < 0.001) than RFI- pigs, whereas water evaporation was similar for both lines. On average, ME intake and HP declined by about 38% and 20%, respectively, from P0 to P1 (P < 0.001). In contrast to ME intake, HP gradually decreased (P < 0.05) from P1 to P3 in connection with a reduction of the activity related HP. The evaporative heat loss represented 30% on the total heat loss on P0, and this proportion significantly increased on P1 (61%; P < 0.001) and remained constant thereafter. In conclusion, our results suggest that thermal heat acclimation in pigs is mainly related to a biphasic reduction of HP rather than a change in the ability of losing heat, and it did not significantly differ between RFI+ and RFI- lines despite a decreased HP in the latter ones.

Ileal digestibility of amino acids of cassava, sweet potato, cocoyam and erythrina foliages fed to growing pigs.

Ileal digestibility in growing pigs fed starch-based diets with inclusion of four tropical leaves in a meal form was studied in a 5 × 5 Latin square design. Five diets were formulated with only casein as protein source in the basal diet (CAS), and casein plus dry cassava (CA) leaves, casein plus dry sweet potato (SP) leaves, casein plus dry cocoyam (CO) leaves and casein plus erythrina (ER) leaves in the other four diets. All diets contained the same amount of CP (14%), either provided by only CAS or a combination of casein and 250 g of leaf meal per kg of diet in the other diets. Leaves were separated manually from stems, and only the leaf part was used. A protein-free diet was fed during a sixth period in order to estimate the endogenous protein losses and calculate the CP- and amino-acid (AA)-standardized ileal digestibility (SID) values. The values for the foliages were calculated according to the difference method, assuming no interaction between the foliage and the casein. The ileal tract apparent digestibility of CP, organic matter and energy was higher in diet CAS than in the other diets (P < 0.05). The SID of CP and AA was close to 0.950 for casein, whereas the SID of AA was markedly lower in the foliages; the SID of indispensable and dispensable AA was highest in CO (0.500 and 0.352) and lowest in ER (0.170 and 0.195); intermediate values were obtained for SPs (0.367 and 0.349) and CA (0.232 and 0.242) leaves. Accordingly, the SID of lysine was highest (0.538) for CO leaves and lowest (0.126) in ER leaves; intermediate values were measured for CA and SP leaves. These low SID values in foliage meals must be related to the high levels of dietary fibre and the presence of secondary metabolites (tannins). These results suggest that it is only possible to replace a fraction of the conventional protein sources such as soyabean meal by tropical foliages in growing pig diets with a preference for CO leaves.

Adaptation to hot climate and strategies to alleviate heat stress in livestock production.

Despite many challenges faced by animal producers, including environmental problems, diseases, economic pressure, and feed availability, it is still predicted that animal production in developing countries will continue to sustain the future growth of the world's meat production. In these areas, livestock performance is generally lower than those obtained in Western Europe and North America. Although many factors can be involved, climatic factors are among the first and crucial limiting factors of the development of animal production in warm regions. In addition, global warming will further accentuate heat stress-related problems. The objective of this paper was to review the effective strategies to alleviate heat stress in the context of tropical livestock production systems. These strategies can be classified into three groups: those increasing feed intake or decreasing metabolic heat production, those enhancing heat-loss capacities, and those involving genetic selection for heat tolerance. Under heat stress, improved production should be possible through modifications of diet composition that either promotes a higher intake or compensates the low feed consumption. In addition, altering feeding management such as a change in feeding time and/or frequency, are efficient tools to avoid excessive heat load and improve survival rate, especially in poultry. Methods to enhance heat exchange between the environment and the animal and those changing the environment to prevent or limit heat stress can be used to improve performance under hot climatic conditions. Although differences in thermal tolerance exist between livestock species (ruminants > monogastrics), there are also large differences between breeds of a species and within each breed. Consequently, the opportunity may exist to improve thermal tolerance of the animals using genetic tools. However, further research is required to quantify the genetic antagonism between adaptation and production traits to evaluate the potential selection response. With the development of molecular biotechnologies, new opportunities are available to characterize gene expression and identify key cellular responses to heat stress. These new tools will enable scientists to improve the accuracy and the efficiency of selection for heat tolerance. Epigenetic regulation of gene expression and thermal imprinting of the genome could also be an efficient method to improve thermal tolerance. Such techniques (e.g. perinatal heat acclimation) are currently being experimented in chicken.

A meta-analysis of the effects of high ambient temperature on growth performance of growing-finishing pigs.

High ambient temperature (T) is one of the most important climatic factors influencing pig performance. Increased T occurs sporadically during summer heat waves in temperate climates and year round in tropical climates. Results of published experiments assessing the effects of high T on pig performance are surprisingly variable. Thus, a meta-analysis was performed to aggregate our knowledge and attempt to explain differences in the results across studies on the effect of increased T on ADFI and ADG in growing-finishing pigs. Data for ADFI and ADG were extracted from 86 and 80 trials, respectively, from articles published in scientific journals indexed in PubMed, Science Direct, and from proceedings of scientific meetings through November 2009. Data on ADFI and ADG were analyzed using a linear mixed model that included the linear and the quadratic effects of T and BW, and their interactions as continuous, fixed effects variables, and the trial as a random effect factor (i.e., block). In addition, the effects of housing type (2 levels: individual and group housing) and the year of publication (3 levels: 1970 to 1989, 1990 to 1999, and 2000 to 2009) on the intercept and the linear regression term for T (i.e., the slope) were also tested. Results showed that high T had a curvilinear effect on ADFI and ADG and that this effect was more pronounced in heavier pigs. Across T, ADFI was less when pigs were group-housed. The intercept and the regression coefficient (slope) for T were significantly affected by the year of publication. The effect of increased T was greater in more contemporary works, suggesting that modern genotypes could be more sensitive to heat stress than older genotypes of lesser growth potential. In conclusion, pig performance decreases at an accelerating rate as T is increased. The large between-study variability on the effects of high T on pig performance is partially explained by differences in pig BW and to a lesser extent by the year the study was published.