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 0.05). 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

Evaluation of the immunity against the prrs virus in piglets from vacunated sows

PòsterJun

Environmental Risk Factors Influence the Frequency of Coughing and Sneezing Episodes in Finisher Pigs on a Farm Free of Respiratory Disease

Inappropriate environmental conditions in pig buildings are detrimental for both pig and farm-staff health and welfare. With ongoing technological developments, a variety of sensor technology is available and can be used to measure environmental conditions such as air temperature, relative humidity, and ammonia and dust concentrations in real time. Moreover, a tool was recently developed to give farmers an objective assessment of pigs' respiratory health by continuously measuring coughing in finisher pigs. This study assessed baseline levels of coughing on a farm free of respiratory disease, and aimed to identify relationships between environmental conditions and coughing frequency in pigs. Six replicates were conducted. Coughing levels in healthy pigs were overall low, and coughing frequency can be predicted by environmental conditions such as high ammonia concentrations and high ventilation rates. Results of this study can be used as guidelines to determine normal coughing levels in healthy pigs, and to calibrate the alarm systems of tools that measure coughing frequency, such as the cough monitor used in this study. The collection and amalgamation of data from a variety of sources related to health, welfare, and performance are important in order to improve the efficiency and sustainability of the pig industry. This study aimed to assess baseline levels of coughing on a farm free of respiratory disease, and to identify relationships between environmental conditions and coughing frequency in finisher pigs. Six replicates were conducted (690 pigs in total). A cross-correlation analysis was performed and lags of the predictor variables were carried forward for multivariable regression analysis when significant and showing r > 0.25. Results show that coughing frequency was overall low. In the first replicate, coughing was best predicted by exposure to higher ammonia concentrations that occurred with a lag of 1, 7, and 15 days (p = 0.003, p = 0.001, and p −0.70). In conclusion, guidelines on coughing levels in healthy pigs and calibration of the alarm systems of tools that measure coughing frequency can be extrapolated from this study. Environmental risk factors are associated with the respiratory health of finisher pigs

Predicting Productive Performance in Grow-Finisher Pigs Using Birth and Weaning Body Weight

peer-reviewedThis study aimed to (1) investigate the effect of birth and weaning body weight (BW) on performance indicators of grow-finisher pigs and (2) estimate birth and weaning BW cut-off values in order to identify slow growing pigs (SGP). Pigs (n = 144) were classified as SMALL (0.9 ± 0.13 kg) or BIG (1.4 ± 0.20 kg) at birth and re-classified as SMALL (5.4 ± 1.6 kg) or BIG (6.3 ± 1.91 kg) at weaning. Individual BW was recorded bi-weekly, and feed intake was recorded on a daily basis. Average daily gain (ADG) and feed intake, feed conversion ratio (FCR) and days to target slaughter weight (TSW) were calculated. SMALL–SMALL pigs had lower ADG (p 0.05). Pigs weaned at <3.7 kg BW would likely be SGP. Pigs born at ≥1.1 kg BW or weaned at ≥6.4 kg BW are more likely to reach TSW at 22 weeks of age. The results suggest that birth BW might not be the best predictor for subsequent performance, as some small-born pigs were able to catch up with their bigger counterparts. The cut-off values identified could be used to design specific management and nutritional strategies for SGP

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

Publication history: Accepted - 4 July 2021; Published online - 6 March 2022.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 0.05). 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.Teagasc Walsh Scholarship. Grant Number: 0415, Open access funding provided by IReL WOA Institution: Irish Agriculture and Food Development Authority Blended DEAL: IRe

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

Publication history: Accepted - 19 June 2023; Published - 24 June 2023.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 (R2cv) 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.Jordi Camp Montoro was supported by the TeagascWalsh Scholarship Scheme grant-in-aid project Introducing new feeding programs and facilities for Irish finishing pigs ref 0415. David Solà-Oriol is supported by the UAB-Banco de Santander Talent Programme. Ramon Muns is supported by the Department of Agriculture, Environment, and Rural Affairs of Northern Ireland, under the Evidence and Innovation project Towards precision feeding: a precise and cost-effective feeding system (ref.: 18 1 08)

Effect of space allowance and mixing on growth performance and body lesions of grower-finisher pigs in pens with a single wet-dry feeder

Publicationhistory: Accepted - 17 December 2020; Published online - 6 January 2021.Background: Low space allowance (SA) and mixing may result in reduced growth performance (GP) and animal welfare issues because of adverse social behaviours directed to pen mates. This could be exacerbated in pens with single space feeders owing to social facilitation of feeding behaviour. The present study aimed to investigate the effect of SA and mixing on GP and body lesions (BL) in pens with one single space wet-dry feeder. Results: Two experiments were conducted on grower-finisher pigs from 10 to 21 weeks of age. In Exp1, pigs (N = 216) were assigned to three SA; 0.96m2/pig (n = 6 pens; 10 pigs/pen; SA96), 0.84m2/pig (n = 6; 12 pigs/pen; SA84) and 0.72m2/pig (n = 6; 14 pigs/pen; SA72), in a randomized design. In Exp2, pigs (N = 230) were used in a 2 × 2 factorial randomized design considering SA and mixing as treatments. Pigs were assigned to two SA; 0.96m2/pig (n = 10 pens; 10 pigs/pen; SA96) and 0.78 m2/pig (n = 10; 13 pigs/pen; SA78) and were either mixed or not at the entry to the finishing facility. GP was not affected by SA (P > 0.05) in either experiment. In Exp2, non-mixed pigs were 5.4 kg heavier (P < 0.001), gained 74 g more per day (P = 0.004), consumed 101.8 g more of feed per day (P = 0.007) and tended to have higher feed efficiency (P = 0.079) than mixed pigs from 11 to 21 weeks of age. Number of BL was affected by SA in both experiments. In Exp1, SA72 pigs had 74.4 and 97.4% more BL than SA96 and SA84 pigs at 20 weeks of age respectively (P < 0.01). In Exp2, SA78 pigs had 48.6, 43.6 and 101.3% more BL than SA96 pigs at 12, 16 and 21 weeks of age respectively (P < 0.05). Mixing did not affect the number of BL from 12 to 21 weeks of age in Exp2 (P > 0.05). Conclusion: Mixing had a considerable effect on growth performance thus, strategies to avoid or mitigate mixing should be considered. Although space allowance had no effect on growth performance, high number of body lesions in the lower space allowance indicates that space allowances equal or below 0.78 m2/pig are detrimental to the welfare of pigs despite following the EU legislation.Jordi Camp Montoro was supported by the Teagasc Walsh Scholarship Scheme grant-in-aid project Introducing new feeding programs and facilities for Irish finishing pigs ref. 0415. The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript

Effect of Phase Feeding, Space Allowance and Mixing on Productive Performance of Grower-Finisher Pigs

Publication history: Accepted - 2 February 2022; Published online - 7 February 2022This study investigates the effects of space allowance (SA), mixing and phase feeding (PF) on performance of grower-finisher pigs. Three trials (T) were conducted. In T1 and T2, 345 pigs/trial were moved to finisher stage at 11 weeks of age and assigned to two SAs: 0.96 (n = 15 pens; 10 pigs/pen) and 0.78 (n = 15; 13 pigs/pen) m2/pig. Mixing was applied to 5 pens of each SA leading to a 2 × 2 factorial arrangement (SA × Mixing). For PF, 2 diets with 0.95 and 0.82 g SID Lys/MJ NE were applied to 5 pens of each SA (not mixed) leading to another 2 × 2 factorial arrangement (SA × PF). In T3, 230 pigs were moved to the grower-finisher stage at 11 weeks of age, mixed, and assigned to 4 treatments (SA × PF; n = 5 pens). Data were analyzed using general linear mixed models. SA did not affect performance (p > 0.05). Non-mixed pigs were 5.40 (T1) and 5.25 (T2) kg heavier than mixed pigs at 21 weeks of age (p < 0.001). PF reduced performance of pigs by 3.45 (T1) and 4.05 (T2) kg at 21 weeks of age (p < 0.001). In conclusion, mixing and reducing SID Lys:NE ratio from 0.95 to 0.82 g/MJ at 15–16 weeks of age, have a more marked impact on performance than reducing SA from 0.96 to 0.78 m2/pig.Jordi Camp Montoro and Joana Pessoa were supported by the Teagasc Walsh Scholarship Scheme grant-in-aid projects Introducing new feeding programs and facilities for Irish finishing pigs ref 0415 and Optimizing feedback of computerized meat inspection findings and Precision Livestock Farming monitors on farm to improve pig health, welfare and carcass quality ref 0165, respectively

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

Publication history: Accepted - 20 June 2022; Published online - 4 July 2022Background: 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) profles as potential biomarkers to identify changes in protein, amino acid and energy dietary content in growing and fnishing pig diets at farm level. Results: Two studies were conducted. The frst 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 gen‑ eral 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 diferences 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 profle but with no excess of protein. Creatinine, triglycerides, branched-chain fatty acids, albumin, propionic acid, and cholesterol showed diferences 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 fnishing pig diets. Other biomarkers like BCFA showed promising results and need to be further studied.Jordi Camp Montoro was supported by the Teagasc Walsh Scholarship Scheme grant-in-aid project Introducing new feeding programs and facilities for Irish finishing pigs ref 0415. The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript

Investigating New and Existing Management and Nutritional Strategies to Improve Productive Performance and Feed Efficiency in Grower-Finisher Pigs

El rendiment productiu i l'eficiència alimentària són crucials per la sostenibilitat de la producció porcina. El període de creixement-finalització representa més del 65% del cost total de producció, sent el període més costós en la producció porcina. Per tant, petites millores en aquesta etapa resulten en un augment dels guanys pels productors de porcs. En aquesta tesi doctoral, s'han realitzat diversos estudis sobre diferents estratègies nutricionals i de maneig per millorar el rendiment productiu i l'eficiència alimentària en porcs de creixement-finalització. El Capítol 3 va investigar l'efecte del pes viu al naixement i al deslletament en el rendiment productiu dels porcs, i identificar valors de tall per al pes viu al naixement i al deslletament, per tal de reconèixer els porcs de creixement lent en etapes inicials del cicle productiu. Els porcs que van néixer i van ser deslletats petits van tenir un baix rendiment productiu, però la mateixa eficiència alimentària que els altres porcs més pesats. El Capítol 4 va comparar el rendiment dels porcs de creixement lent i ràpid, en base a augmentar els nivells de lisina digestible (SID Lys) / aminoàcids (AA) en dietes isoenergètiques. L'eficiència alimentària dels porcs de creixement lent, va millorar quan es van augmentar els nivells de SID Lys/AA de 0,92 a 1,45%, però no va millora la dels porcs de creixement ràpid. Els requeriments dels nutrients poden variar segons la velocitat de creixement a la mateixa edat, i els porcs de creixement lent poden requerir de nivells més alts de SID AA en la dieta per poder aconseguir una millora en el rendiment productiu. El Capítol 5 va investigar l'efecte de la densitat per corral (DC) i la barreja sobre el rendiment productiu i les lesions corporals, en corrals de 10 a 14 porcs amb una menjadora amb un sistema d'alimentació humit-sec i un sol espai. Barrejar els porcs va tenir un efecte en el rendiment productiu, mentre que la DC no el va afectar. L'alt número de lesions corporals en les DC inferiors va indicar que una DC igual o inferior a 0,78 m2/porc és perjudicial per al benestar dels porcs, malgrat seguir la legislació de la UE. El Capítol 6 va estudiar l'efecte de la DC, la barreja i l'alimentació per fases (AF) en el rendiment productiu de porcs allotjats en el mateix tipus de corral que en el Capítol 5. Barrejar i reduir la relació SID Lys/Energia Neta de 0,95 a 0,82 g/MJ a les 15-16 setmanes d'edat, té un impacte més marcat en el rendiment productiu que una reducció de la DC de 0,96 a 0,78 m2/porc. El Capítol 7 va investigar els perfils metabòlits sanguinis, i els dels àcids grassos volàtils (AGV) fecals, per avaluar ineficiències alimentàries segons el contingut de proteïna, AA i energia de la dieta en porcs de creixement i finalització. Els canvis en la dieta i l'edat dels porcs va afectar els perfils d'AGV fecals i dels metabòlits sanguinis. El nitrogen ureic sèric és el millor indicador relacionat amb l'eficiència proteica, el qual augmenta quan els porcs en creixement i finalització són alimentats amb dietes altes en proteïna no balancejades per AA. També, els àcids grassos de cadena ramificada van augmentar en els porcs en creixement alimentats amb dietes altes en proteïna, però no va demostrar la mateixa consistència que el nitrogen ureic sèric. El Capítol 8 va avaluar l'ús de l'espectroscòpia d'infraroig proper (NIRS) per predir els components químics de les femtes i els coeficients de digestibilitat total aparent dels nutrients, en la granja. Els resultats obtinguts van ser similars utilitzant femtes liofilitzades, però sense moldre, fet que facilita l'ús del NIRS.El rendimiento productivo y la eficiencia alimenticia son cruciales para la sostenibilidad de la producción porcina. El período de crecimiento-finalización representa más del 65% del coste total de producción, siendo el período más costoso en la producción porcina. Por lo tanto, pequeñas mejoras en esta etapa resultan en un aumento de las ganancias de los productores de cerdos. En la presente tesis doctoral, se han realizado varios estudios sobre diferentes estrategias nutricionales y de manejo para mejorar el rendimiento productivo y la eficiencia alimenticia en cerdos de crecimiento y finalización. El Capítulo 3 investigó el efecto del peso vivo al nacimiento y al destete en el rendimiento productivo de los cerdos, e identificó valores de corte para el peso vivo al nacer y al destete con tal de reconocer los cerdos de crecimiento lento en etapas tempranas del ciclo productivo. Los cerdos que nacieron y fueron destetados pequeños mostraron un bajo rendimiento productivo, pero tuvieron la misma eficiencia alimenticia que los otros cerdos más pesados. El Capítulo 4 comparó el rendimiento de los cerdos de crecimiento lento y rápido, en base a aumentar los niveles de lisina digestible (SID Lys) / aminoácidos (AA) en dietas isoenergéticas. La eficiencia alimenticia de los cerdos de crecimiento lento mejoró aumentado los niveles de SID Lys/AA de 0,92 a 1,45%, pero no mejoró en los cerdos de crecimiento rápido. Los requerimientos de nutrientes pueden variar dependiendo de la velocidad de crecimiento a la misma edad, y los cerdos de crecimiento lento pueden requerir niveles más altos de SID AA en la dieta para mejorar su desempeño productivo. El Capítulo 5 investigó el efecto de la densidad por corral (DC) y la mezcla sobre el rendimiento productivo y las lesiones corporales, en corrales de 10-14 cerdos con un comedero húmedo-seco de un solo espacio. La mezcla de cerdos tuvo un efecto considerable en el rendimiento productivo, mientras que la DC no lo afectó. Sin embargo, el alto número de lesiones corporales en DC inferiores indicó que una DC igual o inferior a 0,78 m2/cerdo es perjudicial para el bienestar de los cerdos, a pesar de seguir la legislación de la UE. El Capítulo 6 estudió el efecto de la DC, la mezcla y la alimentación por fases (AF) sobre el rendimiento productivo en corrales de 10-14 cerdos con un solo espacio de comedero húmedo-seco. Mezclar y reducir la relación SID Lys/Energía Neta de 0,95 a 0,82 g/MJ a las 15-16 semanas de edad, tiene un impacto más marcado en el rendimiento productivo que una reducción de la DC de 0,96 a 0,78 m2/cerdo. El Capítulo 7 investigó los perfiles de los metabolitos sanguíneos y de los ácidos grasos volátiles (AGV) fecales, para evaluar ineficiencias alimenticias en base a cambios en el contenido de energía, proteína y AA de la dieta en cerdos. Los cambios en la dieta y la edad de los cerdos afectaron los perfiles de AGV fecales y de metabolitos sanguíneos. El nitrógeno ureico sérico es el mejor indicador relacionado con la eficiencia proteica que aumenta en cerdos en crecimiento y finalización cuando son alimentados mediante dietas con niveles altos en proteína y no balanceadas en AA. Los ácidos grasos de cadena ramificada aumentaron en los cerdos en crecimiento alimentados con dietas altas en proteína, pero sin demostraron la misma consistencia. El Capítulo 8 evaluó el uso de la espectroscopia de infrarrojo cercano (NIRS) para predecir los componentes químicos de las heces y los coeficientes de digestibilidad total aparente de los nutrientes en granja. Los resultados obtenidos fueron similares utilizando heces liofilizadas, pero sin moler, facilitando el uso del NIRS.Productive performance and feed efficiency are crucial for sustainability in pig production. The grower-finisher period accounts for over 65% of the total cost of production and it is the most expensive period in pig production. Thus, minor improvements in this stage result in important increases in profit for farmers. In the current thesis, several studies were conducted to improve our knowledge on different management and nutritional strategies to improve the productive performance and feed efficiency in grower-finisher pigs. Slow growing pigs within a batch may be one of the most important factors affecting pig production and they cause increases in body weight (BW) variability within the batch of pigs. In Chapter 3, we investigated the effect of birth and weaning BW on key performance indicators of grower-finisher pigs, and determined the cut-off values for birth and weaning BW to identify slow growing pigs early in life. Pigs born and weaned small showed a poor productive performance up to slaughter, but were as feed efficient as their heavier counterparts. Chapter 4 compared the response in performance of slow and fast growing pigs to an increase of dietary standardized ileal digestible (SID) lysine (Lys) / amino acid (AA) levels in isoenergetic diets. Slow growing pigs' feed efficiency was improved when dietary SID AA levels were increased from 0.92 up to 1.45% SID Lys/AA. The latter was not observed in fast growing pigs. Nutrient requirements may vary depending on growth rate at the same age, and slow growing pigs may require higher dietary SID AA levels than fast growing pigs to present a better productive performance. Chapters 5 and 6 focused on common management strategies, such as space allowance (SA), mixing and phase feeding (PF), to understand and optimize the productive performance and feed efficiency of the whole batch. Chapter 5 investigated the effect of SA and mixing on productive performance and body lesions in grower-finisher pigs, housed in pens of 10-14 pigs with a single space wet-dry feeder. Mixing appeared to have considerable effect on growth performance, while SA did not affect performance. Nevertheless, high number of body lesions in the lower SA indicated that SA equal or below 0.78 m2/pig are detrimental to the welfare of pigs despite following the EU legislation. Chapter 6 studied the effect of SA, mixing and PF on productive performance in grower-finisher pigs, housed in pens of 10-14 pigs with a single space wet-dry feeder. Mixing and reducing SID Lys:Net Energy ratio from 0.95 to 0.82 g/MJ at 15-16 weeks of age, have a more marked impact on productive performance than a reduction in SA from 0.96 to 0.78 m2/pig. Chapter 7 and 8 studied fast analysis methods to assess feed efficiency at farm level to optimise diet formulation and productive performance of grower-finisher pigs. Chapter 7 studied blood serum metabolite and faecal volatile fatty acid (VFA) profiles to assess feed inefficiencies in protein, AA and energy dietary content. Dietary changes and the pigs' age affected both blood metabolite and faecal VFA profiles. The main findings from this chapter were that serum urea nitrogen is the best indicator related to protein efficiency, increasing in growing and finishing pigs fed high protein diets with unbalances in AA profiles. Branched-chain fatty acids also increased in growing pigs fed high protein diets, but did not show the same consistency as urea. Chapter 8 evaluated the potential use of near infrared reflectance spectroscopy (NIRS) to predict faeces chemical components and apparent total tract digestibility (ATTD) coefficients of nutrients at farm level. The results obtained were similar using freeze-dried faeces but without grounding them, which facilitates NIRS applicability