Lean Growth Rate Research Articles

43 Approaches for improving nitrogen utilization efficiency and environmental sustainability of pork production systems

Abstract Nitrogen (N) is an essential element for life, but due to its inefficient utilization, N waste and emissions generated have exceeded the planetary boundaries and ability of the Earth to effectively overcome these environmentally detrimental effects. Global food animal production contributes 29 to 34% of total global N emissions, with pork supply chains contributing about 16% of these emissions. Life cycle N use efficiency (NUE) of U.S. pork production is only about 56%, which is similar to broiler (55%) and egg (50%) production, but greater than beef (10%) and milk (31%) production. However, only about 10 to 44% of dietary N is converted into edible pork products. While genetic improvement has increased NUE associated with improved lean growth rate, improvement in litter size has led to an increased proportion of low-birth-weight pigs that have reduced NUE. Although metabolic modifiers including porcine somatotropin, ractopamine, and immunocastration improve NUE, they are not feasible or acceptable to consumers in many countries. Separate sex feeding and reducing market weight can also improve NUE. Ultimately feeding program design and implementation have the greatest potential to improve NUE because feed is associated with 70% of N emissions in pork production systems. Multi-objective feed formulation using Life Cycle Assessment environmental impact data of feed ingredients, precision feed formulation and feeding practices to overcome variability in digestible nutrient content of feed ingredients and nutritional requirements of pigs fed in groups, feed processing to enhance energy and nutrient digestibility, and minimizing feed wastage offer the greatest opportunity to improve NUE and environmental sustainability. There are substantial differences in greenhouse gas emissions and embedded water and land use associated with growing-finishing feeding programs depending on the dietary proportions of corn, soybean meal, distillers dried grains with solubles (DDGS), and crystalline amino acids among U.S. geographic regions. Furthermore, addition of thermally processed supermarket food waste to corn-soybean meal (CSBM) diets can significantly reduce environmental impacts and diet cost without compromising growth performance and carcass composition compared with current commercial feeding programs. Although growing-finishing feeding programs using CSBM diets with minimal crystalline amino acids result in greater N intake, N retained, and urinary N excretion compared with feeding low protein, crystalline amino acid supplemented (LP) diets, and diets containing 30% DDGS, growth performance and carcass composition are optimized and impacts on climate change, marine and freshwater eutrophication, and fossil resource are reduced by feeding CSBM diets compared with feeding LP or DDGS diets. Sourcing and using feed ingredients with reduced environmental impact metrics along with precision diet formulation and feeding practices to ensure “getting the right amount of energy and nutrients in the right feed fed to the right pigs at the right time” can improve NUE and environmental sustainability of pork production systems.

126 A nutritional solution based on calcidiol (25-OH-D3, HyD) and triterpenoid affects muscle protein synthesis pathways in grower-finisher pigs

Abstract To boost profitability in pig production, it is important to achieve increased lean growth rates and maximize efficiency, especially in grower-finisher pigs where feed intakes are high. Molecular research, especially the study of gene expression, is a proven tool for understanding the precise mechanisms behind muscle tissue growth, including a recent focus on pathways such as the mammalian target of rapamycin (mTOR). In the current work, gene expression analyses were used to study the mode of action of the combination of calcidiol (25-OH-D3, HyD) and triterpenoid, which has shown significant growth and efficiency improvements in grower-finisher pigs (McCormack et al., 2024). Three experimental diets were evaluated for 7 wk; Positive control: 0.7% total Ca, 0.36% total P, vit D3 at 1500IU/kg feed (PC), negative control: PC diet + 30% reduced Ca and 10% reduced P (NC), and NC diet with 1,500IU D3 in calcidiol form (25-OH-D3, HyD) and triterpenoid (NC+). At 19 wk of age, 16 animals per treatment were sacrificed and tissue samples were taken from the longissimus muscle and preserved in RNA later solution. The RNA was extracted, quality control checked, and mRNA sequenced using the Illumina platform with 150 base pair paired-end sequencing and 30M read depth. The sequenced data were aligned to the Sus scrofa reference genome (Sscrofa11.1) using Kallisto. Data were normalized and analyzed for differentially expressed genes (DEGs) between treatments using DeSeq2. Genes were assigned to biological pathways using Biofractal’s customisation of the Reactome pathway database. For statistical analysis, RNA integrity number and treatment were included in the model. In the PC compared with the NC, there were 71 DEGs using a false discovery rate (FDR) of < 0.10. Altered pathways included the inhibition of cellular stress pathways and increased cell turnover in the muscle of PC compared with NC pigs. In the NC+ compared with the NC, there were 155 DEGs (FDR < 0.10). The most significantly upregulated gene in the NC+ treatment was adenylate cyclase (FDR < 0.001), an upstream regulator of several pathways related to energy metabolism and muscle protein synthesis. This mechanism was confirmed in the pathway analysis, which found that the NC+ treatment activated PKA-mediated phosphorylation of CREB, a pathway that inhibits muscle atrophy. Furthermore, the NC+ treatment activated several pathways related to muscle growth, including the mammalian target of rapamycin complex 1 (mTORC1). In this study the addition of calcidiol (25-OH-D3, HyD) and triterpenoid to the diet was found to specifically affect molecular pathways in the muscle of grower-finisher pigs involved in both the inhibition of muscle breakdown as well as activating muscle growth.

PSIII-13 Effects of Weather, Body Weight, and Feed Intake on Total and Liquid Water Intake in Beef Bulls

Abstract Research conducted in the 1950s to determine water requirements used cattle that vary greatly from the animals being raised today. Changes in lean composition and growth rate in young cattle and milk production and mature size in cows have likely altered water requirements. Furthermore, most of the research has been conducted on animals being fed for slaughter, rather than bulls or reproductive females. The objective of this study was to analyze the effect of weather variables, dry matter intake (DMI), and body weight (BW) on total daily water intake (TDWI) in growing beef bulls. Angus (n = 15) and Simmental x Angus bulls (n = 29) with an average initial BW of 362.5 ± 27.0 kg were housed in an open front, monoslope building at the SDSU Cow-Calf Education and Research Facility (CCERF) from November 9, 2021, to March 1, 2022. Bulls were provided with ad libitum access to feed (1.15 Mcal NEg/kg dry matter, 14% crude protein, 52.2% dry matter) and water using the Insentec Roughage Intake Control system (Hokofarm, Marknesse, Netherlands). Feed and water disappearance were assumed to be caused by intake. Water intake was measured in kg; however, the data were converted to L based on a correction factor determined by weighing a known amount of water. Body weights were taken every 28 d to determine ADG and predict daily BW during the duration of the study. Daily weather variables were collected from the South Dakota Mesonet station located 3.86 km from the CCERF. Weather variables analyzed included: average windchill (°C), solar radiation (W/m2), and wind speed (km/h); and minimum, maximum, and average relative humidity (%) and average temperature (°C). R-studio (R-4.1.2.pkg) was used to develop a linear mixed effects model with random intercept and slope used to account for the within subject correlations. Total daily water intake increased with increasing DMI (1.921 L TDWI per kg DMI; P < 0.0001), BW (0.025 L TDWI per kg BW; P = 0.0055), and maximum daily temperature (0.171 L TDWI per 1°C; P = 0.0023). For every 1% increase in the minimum relative humidity, TDWI tended to increase by 0.041 L (P = 0.0616). Warmer wind chill also tended to increase TDWI (0.463 L per 1°C; P = 0.0707). The effects of DMI, BW, maximum daily temperature, minimum relative humidity, and wind chill were predictive of TDWI in growing beef bulls fed during the winter months in South Dakota. This model will be useful for predicting TDWI in growing beef bulls that are raised in areas that experience similar winter weather conditions.

Challenges and opportunities for improving nitrogen utilization efficiency for more sustainable pork production

Pork is one of the most consumed animal-derived protein sources around the world, but less than 45% of dietary nitrogen (N) is converted into edible lean meat. This inefficiency contributes to the 80% of human-induced N emissions that have resulted in exceeding the planetary boundaries for N. Reducing this inefficiency requires using a multifaceted approach. Swine genetic selection programs have improved the rate of lean growth in recent decades, but further improvements may be difficult because of lack of genetic variation within the global pig population. Breeding programs to increase litter size have led to intrauterine growth restriction and an increased proportion of low-birth-weight piglets which do not utilize dietary protein as efficiently as normal birth weight pigs. Intact males have greater lean growth rate and N efficiency than castrates and gilts, and the use of immunocastration technology has been implemented in some countries to capture this benefit while minimizing boar taint in pig meat. Use of other metabolic modifiers including porcine somatotropin and ractopamine, alone or in combination with immunocastration, can further enhance lean growth and dietary N efficiency, but a general lack of consumer acceptance and potential food safety concerns have led to regulatory restrictions in many countries. Because feed production contributes about 70% of N emissions in pig production systems, use of precision feed formulation and feeding practices, selected dietary feed additives, feed processing, and minimizing feed wastage appear to offer the greatest opportunity to reduce N waste and environmental footprint to improve the sustainability of pork production.

Effects of restricting energy during the gilt development period on growth and reproduction of lines differing in lean growth rate: responses in reproductive performance and longevity.

Longevity and reproductive performance are economically important traits in the swine industry that are largely influenced by nutrition and other environmental factors. Reproductive performance and longevity through 4 parities was assessed in gilts of 2 genetic lines developed on ad libitum access to feed or restricted to 75% of ad libitum intake. A total of 661 gilts were used in a 2 × 2 factorial with half of the gilts allocated to an ad libitum diet (AL; n = 330), while the other half were energy restricted by 25% (R; n = 331) from 123 to 235 d of age. All gilts were sired by an industry maternal line. Dams of the gilts were from either a Large White (W) by Landrace (L) industry maternal line or Nebraska Selection Line 45X, producing gilts designated as W × L (n = 355) and L45X (n = 306), respectively. Daily estrus detection began at 140 d of age to obtain age at puberty (AP). Gilts (n = 510) were mated on their second or later estrus, beginning at 240 d of age. Sow weight and backfat were recorded at 110 d of gestation and weaning of each parity. Number of live-born, stillborn, and mummified pigs per litter and piglet birth and weaning weights were recorded through 4 parities. More L45X than W × L and more AL than R gilts reached puberty by 230 d of age (P < 0.01). Dietary treatment did not affect probability to produce parities 1 to 4 or any litter trait analyzed. The L45X females tended to be more likely to produce parities 1 (P < 0.08) and 3 (P < 0.06), while W × L had heavier litters at birth (P < 0.01) and weaning (P = 0.01). Treatment by parity interactions (P < 0.01) existed for weight and backfat prior to farrowing and backfat at weaning, and weight at weaning exhibited a line by treatment by parity interaction (P = 0.04) as R sows had lower weights and backfats in earlier parities, but caught up to AL sows in later parities. A treatment by parity interaction (P < 0.01) was also present for backfat loss from farrowing to weaning as R gilts lost less backfat than AL in parities 1 and 2, but more in parities 3 and 4. No significant differences were detected between lines or treatments for lifetime production traits. The populations of pigs and data presented here provide a framework for a diverse array of further studies. Alternative approaches to restrict energy have been assessed in addition to methods of marker-assisted and genomic selection for improvement of litter size and sow longevity.

356 Meal feeding compared with continuous feeding enhances insulin and amino acid signaling to translation initiation in skeletal muscle of pigs

Abstract Objectives: Meal feeding enhances skeletal muscle protein synthesis and lean growth more than continuous feeding in piglets. This enhanced muscle protein synthesis with meal feeding is associated with increased activation of mTORC1-dependent translation initiation. The mechanism underlying this response is unknown. We aimed to identify insulin and amino acid signaling components involved in the enhanced lean growth that results from meal feeding vs. continuous feeding in term-born pigs. Methods: Newborn piglets were fed for 21 d an equal amount of sow milk replacer (12.8 g protein and 155 kcal/(kg BW.d)) by gastrostomy tube either as intermittent bolus meals every 4 h (MEAL) or by continuous infusion (CON). After 21 d, gastrocnemius muscle was collected from CON, and before (MEAL-0) or 60 min after a meal (MEAL-60). Components of the insulin and amino acid signaling pathways up- and downstream of mTORC1 that regulate protein translation were measured. Results: Phosphorylation of AKT and TCS2 was greater in MEAL-60 than in MEAL-0 and CON (P &amp;lt; 0.05). The association of Sestrin2 with GATOR2 was similar in CON and MEAL-0 but was lower in MEAL-60 (P &amp;lt; 0.05). The abundances of RagA-mTOR, RagC-mTOR, and Rheb-mTOR, but not CASTOR1-GATOR2, complexes were higher in MEAL-60 than in CON and MEAL-0 (P &amp;lt; 0.05). The phosphorylation of S6K1 and 4EBP1 was higher in MEAL-60 than CON and MEAL-0 (P &amp;lt; 0.05). The abundances of Sestrin2, GATOR2, CASTOR1, RagA, RagC, and Rheb and the phosphorylation of eIF2alpha, eEF2, ERK1/2 and AMPK were unaffected by treatments. Conclusions: Our results demonstrate that the enhanced rate of skeletal muscle protein synthesis and lean growth with meal feeding compared with continuous feeding are due to the enhanced activation of both insulin and amino acid signaling pathways that result in the greater stimulation of translation initiation. Support: NIH HD085573, USDA CRIS 6250-51000-055, NIH HD072891, USDA NIFA 2013-67015-20438.

The fungal community and its interaction with the concentration of short-chain fatty acids in the faeces of Chenghua, Yorkshire and Tibetan pigs.

SummaryDespite their important roles in host nutrition and metabolism, and potential to cause disease, our knowledge of the fungal community in the mammalian gut is quite limited. To date, diversity and composition of fungi in swine gut still remains unknown. Therefore, the first internal transcribed spacer of fungi in faecal samples from three breeds of pigs (10 pigs for each breed) was sequenced based on an Illumina HiSeq 2500 platform, and the relationship between the fungal community and the concentrations of main short‐chain fatty acids (SCFAs) was also analysed. Results indicated that Chenghua (local, higher body fat rate), Yorkshire (foreign, higher lean meat and growth rate) and Tibetan (plateau, stronger disease resistance) pigs harboured distinct fungal community. The Basidiomycota and Ascomycota presented as the two predominant phyla, with Loreleia, Russula and Candida as the top three genera in all samples. Network analysis revealed a total of 35 correlations among different fungal genera, with 27 (77.14%) positive and 8 (22.86%) negative pairwise interactions. Canonical correspondence analysis suggested that fungi in the faeces of pigs were more correlated to the concentration of acetate and butyrate rather than propionate. Spearman’s correlation further showed that Tomentella was positively correlated to both acetate and butyrate, and Loreleia was positively correlated to propionate (P < 0.05), while Nephroma and Taiwanofungus were negatively correlated to acetate and propionate (P < 0.05). These findings expanded our knowledge on the intestinal fungi in pigs with different genotypes and phenotypes, indicating that fungi may play an indispensable role during the metabolism of host and the maintenance of intestinal health. The cross‐feeding between fungi and other microorganisms may be crucial during the digestion of dietary carbohydrates and the associated physiological processes, which is worthy to be further studied.

Intermittent Bolus Compared with Continuous Feeding Enhances Insulin and Amino Acid Signaling to Translation Initiation in Skeletal Muscle of Pigs Born at Term (P08-071-19)

ObjectivesOur recent study in a piglet model of the human neonate born at full term showed that intermittent bolus feeding promotes greater rates of protein synthesis in skeletal muscle than continuous feeding, leading to an increase in lean growth. This enhanced rate of muscle protein synthesis with intermittent bolus feeding is associated with an increased activation of mTORC1-dependent translation initiation. However, the mechanism underlying this response is unknown. In this study, we aimed to identify the insulin and/or amino acid signaling components involved in the enhanced stimulation of lean growth by intermittent bolus compared to continuous feeding in term-born pigs. MethodsTerm piglets (2–3 d old) were fed for 21 d an equal amount (240 ml/kg body weight [BW]/d) of sow milk replacer containing 12.8 g protein and 175 kcal/kg BW/d. Feedings were administered by gastrostomy tube either as intermittent bolus meals every 4 h (INT) or by continuous infusion (CON). After 21 d, gastrocnemius muscle was collected from CON, INT-0 (before a meal) and INT-60 (60 min after a meal) groups. Upstream and downstream insulin and amino acid signaling components of relevance to mTORC1 activation and protein translation were measured. ResultsPhosphorylation of AKT and TCS2 was greater in INT-60 than in INT-0 and CON groups (P < 0.05). There was no significant difference between CON and INT groups in the phosphorylation of ERK 1/2 and AMPK. The association of Sestrin2, a leucine sensor, with GATOR2 was similar in CON and INT-0 but was lower in INT-60 (P < 0.05). The abundances of RagA-mTOR, RagC-mTOR, and Rheb-mTOR complexes were higher in INT-60 than in CON and INT-0 (P < 0.05). The phosphorylation of S6K1 and 4EBP1 was higher in INT-60 than CON and INT-0 groups (P < 0.05). Phosphorylation of eIF2alpha and eEF2 were not affected by treatments. ConclusionsOur results demonstrate that, following a full-term birth, the enhanced rate of skeletal muscle protein synthesis and lean growth with intermittent bolus compared to continuous feeding is at least in part due to the enhanced activation of both insulin and amino acid signaling pathways leading to greater stimulation of translation initiation. Funding SourcesNIH HD085573, USDA CRIS 6250-51000-055, NIH HD072891, USDA NIFA 2013-67015-20438.

Continuous Feeding Does Not Blunt Skeletal Muscle Protein Synthesis and Lean Growth Compared to Intermittent Bolus Feeding in the Preterm Piglet (OR26-06-19)

ObjectivesRefining early feeding strategies for premature infants is essential for mitigating adverse outcomes of prematurity. In neonatal term piglets, continuous feeding blunts growth compared to intermittent bolus feeding. Our objective was to determine the impact of feeding modality on lean growth in preterm pigs. We hypothesized that intermittent bolus feeding can mitigate low lean growth rates in preterm neonates compared to continuous feeding. MethodsPigs obtained by C-section (105 d gestation; 952 ± 205 g body weight) were fitted with an umbilical artery catheter (later replaced with jugular vein catheter) and an orogastric tube for parenteral and enteral nutrition, respectively. Pigs were assigned to continuous (CONT; 7.5 mL/[kg·h]) or intermittent bolus (INT; 30 mL/kg every 4 h over 15 min) feeding for 21 d. Pigs initially received parenteral nutrition and were advanced to full oral feeds over 6 d (220 kcal/kg and 16 g/kg protein per day). Body composition (by DXA), plasma insulin, and skeletal muscle anabolic signaling and fractional protein synthesis rates (PS; L-[ring-2H5]phenylalanine) were determined in INT pigs in the postabsorptive (before a meal, INT-PA; n = 13) and postprandial (after a meal, INT-PP; n = 16) states and in CONT pigs (n = 14). ResultsBody weight gain, lean mass, and fat mass did not differ between INT and CONT pigs. Insulin was lower before feeding for INT pigs than CONT pigs (P < 0.05). Insulin increased with feeding for INT pigs and exceeded that of CONT pigs at 30 and 60 min (P < 0.01) before returning to baseline levels at 240 min. In the longissimus dorsi (LD), gastrocnemius, and soleus muscles, the abundance of the eIF4E·eIF4G complex, which is required for translation initiation, was greater in INT-PP and CONT pigs than INT-PA pigs (P < 0.01), but did not differ between INT-PP and CONT pigs. PS in the LD muscle was greater in INT-PP pigs than INT-PA pigs (P < 0.01), but did not differ between INT-PP and CONT pigs. ConclusionsContinuous feeding does not blunt translation initiation and protein synthesis in skeletal muscle compared to intermittent bolus feeding in preterm piglets. The resulting absence of enhanced lean growth with intermittent bolus compared to continuous feeding contrasts with term piglets and may be a consequence of prematurity. Funding SourcesUSDA CRIS 6250-51000-055, NIH HD072891, and USDA NIFA 2013-67015-20438.

A genome-wide association study of growth and fatness traits in two pig populations with different genetic backgrounds.

Improvement in growth and fatness traits are the main objectives in pig all breeding programs. Tenth rib backfat thickness (10RIBBFT) and days to 100 kg (D100), which are good predictors of carcass lean content and growth rate, respectively, are economically important traits and also main breeding target traits in pigs. To investigate the genetic mechanisms of 10RIBBFT and D100 of pigs, we sampled 1,137 and 888 pigs from 2 Yorkshire populations of American and British origin, respectively, and conducted genome-wide association study (GWAS) through combined analysis and meta-analysis, to identify SNPs associated with 10RIBBFT and D100. A total of 11 and 7 significant SNPs were identified by combined analysis for 10RIBBFT and D100, respectively. And in meta-analysis, 8 and 7 significant SNPs were identified for 10RIBBFT and D100, respectively. Among them, 6 and 5 common significant SNPs in two analysis results were, respectively, identified associated with 10RIBBFT and D100, and correspondingly explained 2.09% and 0.52% of the additive genetic variance of 10RIBBFT and D100. Further bioinformatics analysis revealed 10 genes harboring or close to these common significant SNPs, 5 for 10RIBBFT and 5 for D100. In particular, Gene Ontology analysis highlighted 6 genes, PCK1, ANGPTL3, EEF1A2, TNFAIP8L3, PITX2, and PLA2G12, as promising candidate genes relevant with backfat thickness and growth. PCK1, ANGPTL3, EEF1A2, and TNFAIP8L3 could influence backfat thickness through phospholipid transport, regulation of lipid metabolic process through the glycerophospholipid biosynthesis and metabolism pathway, the metabolism of lipids and lipoproteins pathway. PITX2 has a crucial role in skeletal muscle tissue development and animal organ morphogenesis, and PLA2G12A plays a role in the lipid catabolic and phospholipid catabolic processes, which both are involved in the body weight pathway. All these candidate genes could directly or indirectly influence fat production and growth in Yorkshire pigs. Our findings provide novel insights into the genetic basis of growth and fatness traits in pigs. The candidate genes for D100 and 10RIBBFT are worthy of further investigation.

Effects of dietary protein and energy intake on growth, body composition and nutrient utilisation in lambs reared artificially with milk replacers and pellet feeds

A growth simulation model demonstrated that the ratio between crude protein (CP) and metabolisable energy (ME) intake (CP:ME) of lambs reared artificially with milk replacers and pellets feed did not adequately match their requirements and this mismatch would limit their growth in early life. The aim of this study was to test the effect of a modelled ratio between CP and ME intake on growth, body composition and nutrient utilization. A total of 28 Romney twin-born male lambs were allocated to a randomized 2 × 2 factorial design with seven lambs per treatment. Treatments consisted of two protein levels in iso-energetic milk replacer (normal CP:ME milk [NM] and high CP:ME milk [HM]) fed as a proportion of the lamb’s live weight (LW) and two protein levels in iso-energetic pellets (low-CP:ME pellets [LP] and high CP:ME pellets [HP]) fed ad libitum; resulting in four experimental groups (NMLP, NMHP, HMLP, HMHP). This design resulted in lambs having different CP intake to ME intake ratio during the experiment. Lambs were kept indoors in individual pens. Five lambs from each treatment were placed in metabolic cages at 9 kg and 16 kg live weight (LW) for 4 d to allow for total fecal and urine collection. All lambs were slaughtered at 18 kg LW. The weights and chemical composition of the carcass, organs, head and skin were determined. Lambs fed HM had greater (P < 0.01) CP intake, daily gain, gain to feed ratio and greater liver and kidney weights than lambs fed NM. Pellet treatment had no effect (P > 0.05) on any of the intake or growth measurements. Pellet intake was low and contributed only to 20% of the CP intake and 18% of the ME intake. Deposition of protein and water in the carcass, organs, and empty bodies were greater (P < 0.01) in HM than in NM lambs. Fat deposition and energy retention in carcass, organs, and empty bodies were greater (P < 0.05) in NM than in HM lambs. Pellet treatment had no effect (P > 0.05) on protein, fat and water deposition rates. A maximum protein deposition rate of 43 g per day was measured for lambs having a CP:ME intake ratio in excess of 14.2. In conclusion, increasing the CP:ME ratio of milk replacer is a way of improving lean growth rates in pre-weaned lambs.

P3007 Time course of the response to ACTH in pig: biological and transcriptomic study

Background: HPA axis plays a major role in physiological homeostasis. It is also involved in stress and adaptive response to the environment. In farm animals in general and specifically in pigs, breeding strategies have highly favored production traits such as lean growth rate, feed efficiency and prolificacy at the cost of robustness. On the hypothesis that the HPA axis could contribute to the trade-off between robustness and production traits, we have designed this experiment to explore individual variation in the biological response to the main stress hormone, cortisol, in pigs. We used ACTH injections to trigger production of cortisol in 120 juvenile Large White (LW) pigs from 28 litters and the kinetics of the response was measured with biological variables and whole blood gene expression at 4 time points. A multilevel statistical analysis was used to take into account the longitudinal aspect of the data. Results: Cortisol level reached its peak 1 h after ACTH injection. White blood cell composition was modified with a decrease of lymphocytes and monocytes and an increase of granulocytes (FDR < 0.05). Basal level of cortisol was correlated with birth and weaning weights. Microarray analysis identified 65 unique genes of which expression responded to the injection of ACTH (adjusted P < 0.05). These genes were classified into 4 clusters with distinctive kinetics in response to ACTH injection. The first cluster identified genes strongly correlated to cortisol and previously reported as being regulated by glucocorticoids. In particular, DDIT4, DUSP1, FKBP5, IL7R, NFKBIA, PER1, RGS2 and RHOB were shown to be connected to each other by the glucocorticoid receptor NR3C1. Most of the differentially expressed genes that encode transcription factors have not been described yet as being important in transcription networks involved in stress response. Their co-expression may mean co-regulation and they could thus provide new patterns of biomarkers of the individual sensitivity to cortisol. Conclusions: We identified 65 genes as biological markers of HPA axis activation at the gene expression level. These genes might be candidates for a better understanding of the molecular mechanisms of the stress response.

Editorial: Improving Animal Welfare through Genetic Selection.

Editorial: Improving Animal Welfare through Genetic Selection.

Long-term effects of straw blocks in pens with finishing pigs and the interaction with boar type

This study verified the effect of straw blocks on the behavior and growth of finishing pigs and possible interactions with the genetic background (boar type). A total of 359 finishing pigs, which were offspring from different boar types, were housed in gender-mixed pens with slatted floors. Half of these pigs descended from sires selected for better carcass traits and lower growth rates (type C) and the other half from sires selected for better growth and poorer carcass traits (type G). The offspring of these two boar types were spread equally over control (only a chain) and treatment groups (chain and straw blocks in a dispenser). Direct individual behavioral observations were carried out once a week and the presence of lesions on the body was verified every two weeks. Individual weights were recorded at different weighing moments. Lesions on organs and carcass traits were obtained after slaughter.A lower frequency of pen mate manipulation was observed in pens with access to straw blocks in type G pigs. For type C pigs however, no significant difference was present in pen mate manipulation between groups with or without straw. It has been shown that pigs selected for high lean tissue growth rate show higher frequencies of tail biting behavior and in this study, providing straw blocks does not seem to be sufficient to decrease this behavior. These pigs also showed more pen manipulation, which might reflect an increased foraging motivation or motivation to explore. Mounting and fighting were recorded more frequently at the start of the finishing phase and in this period significantly more in pens with straw blocks, which might be related to both competition for straw and introduction in a new environment. Growth was not significantly affected by the presence of straw blocks. Type G pigs however reached higher slaughter weights compared to type C pigs, but no interaction with the presence of straw was seen.It can be concluded that in general, straw blocks decreased the manipulation of pen mates in finishing pigs, but this effect was only seen in pigs selected for better growth. Pigs predisposed to a higher lean meat percentage showed in general higher frequencies of this behavior and in these pigs, straw blocks did not reduce pen mate manipulation compared to more barren environments. In general, the presence of the straw blocks seemed to be associated with more competition related behavior in the beginning of the fattening period. The presence of straw did not affect growth or carcass traits.

Time course of the response to ACTH in pig: biological and transcriptomic study.

BackgroundHPA axis plays a major role in physiological homeostasis. It is also involved in stress and adaptive response to the environment. In farm animals in general and specifically in pigs, breeding strategies have highly favored production traits such as lean growth rate, feed efficiency and prolificacy at the cost of robustness. On the hypothesis that the HPA axis could contribute to the trade-off between robustness and production traits, we have designed this experiment to explore individual variation in the biological response to the main stress hormone, cortisol, in pigs. We used ACTH injections to trigger production of cortisol in 120 juvenile Large White (LW) pigs from 28 litters and the kinetics of the response was measured with biological variables and whole blood gene expression at 4 time points. A multilevel statistical analysis was used to take into account the longitudinal aspect of the data.ResultsCortisol level reached its peak 1 h after ACTH injection. White blood cell composition was modified with a decrease of lymphocytes and monocytes and an increase of granulocytes (FDR<0.05). Basal level of cortisol was correlated with birth and weaning weights. Microarray analysis identified 65 unique genes of which expression responded to the injection of ACTH (adjusted P<0.05). These genes were classified into 4 clusters with distinctive kinetics in response to ACTH injection. The first cluster identified genes strongly correlated to cortisol and previously reported as being regulated by glucocorticoids. In particular, DDIT4, DUSP1, FKBP5, IL7R, NFKBIA, PER1, RGS2 and RHOB were shown to be connected to each other by the glucocorticoid receptor NR3C1. Most of the differentially expressed genes that encode transcription factors have not been described yet as being important in transcription networks involved in stress response. Their co-expression may mean co-regulation and they could thus provide new patterns of biomarkers of the individual sensitivity to cortisol.ConclusionsWe identified 65 genes as biological markers of HPA axis activation at the gene expression level. These genes might be candidates for a better understanding of the molecular mechanisms of the stress response.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-2118-8) contains supplementary material, which is available to authorized users.

Genetic variation in efficiency to deposit fat and lean meat in Norwegian Landrace and Duroc pigs.

Feed costs amount to approximately 70% of the total costs in pork production, and feed efficiency is, therefore, an important trait for improving pork production efficiency. Production efficiency is generally improved by selection for high lean growth rate, reduced backfat, and low feed intake. These traits have given an effective slaughter pig but may cause problems in piglet production due to sows with limited body reserves. The aim of the present study was to develop a measure for feed efficiency that expressed the feed requirements per 1 kg deposited lean meat and fat, which is not improved by depositing less fat. Norwegian Landrace ( = 8,161) and Duroc ( = 7,202) boars from Topigs Norsvin's testing station were computed tomography scanned to determine their deposition of lean meat and fat. The trait was analyzed in a univariate animal model, where total feed intake in the test period was the dependent variable and fat and lean meat were included as random regression cofactors. These cofactors were measures for fat and lean meat efficiencies of individual boars. Estimation of fraction of total genetic variance due to lean meat or fat efficiency was calculated by the ratio between the genetic variance of the random regression cofactor and the total genetic variance in total feed intake during the test period. Genetic variance components suggested there was significant genetic variance among Norwegian Landrace and Duroc boars in efficiency for deposition of lean meat (0.23 ± 0.04 and 0.38 ± 0.06) and fat (0.26 ± 0.03 and 0.17 ± 0.03) during the test period. The fraction of the total genetic variance in feed intake explained by lean meat deposition was 12% for Norwegian Landrace and 15% for Duroc. Genetic fractions explained by fat deposition were 20% for Norwegian Landrace and 10% for Duroc. The results suggested a significant part of the total genetic variance in feed intake in the test period was explained by fat and lean meat efficiency. These new efficiency measures may give the breeders opportunities to select for animals with a genetic potential to deposit lean meat efficiently and at low feed costs in slaughter pigs rather than selecting for reduced the feed intake and backfat.

Phenotypic and genetic relationships between growth and feed intake curves and feed efficiency and amino acid requirements in the growing pig

Improvement of feed efficiency in pigs has been achieved essentially by increasing lean growth rate, which resulted in lower feed intake (FI). The objective was to evaluate the impact of strategies for improving feed efficiency on the dynamics of FI and growth in growing pigs to revisit nutrient recommendations and strategies for feed efficiency improvement. In 2010, three BWs, at 35±2, 63±9 and 107±7 kg, and daily FI during this period were recorded in three French test stations on 379 Large White and 327 French Landrace from maternal pig populations and 215 Large White from a sire population. Individual growth and FI model parameters were obtained with the InraPorcR software and individual nutrient requirements were computed. The model parameters were explored according to feed efficiency as measured by residual feed intake (RFI) or feed conversion ratio (FCR). Animals were separated in groups of better feed efficiency (RFI− or FCR−), medium feed efficiency and poor feed efficiency. Second, genetic relationships between feed efficiency and model parameters were estimated. Despite similar average daily gains (ADG) during the test for all RFI groups, RFI− pigs had a lower initial growth rate and a higher final growth rate compared with other pigs. The same initial growth rate was found for all FCR groups, but FCR− pigs had significantly higher final growth rates than other pigs, resulting in significantly different ADG. Dynamic of FI also differed between RFI or FCR groups. The calculated digestible lysine requirements, expressed in g/MJ net energy (NE), showed the same trends for RFI or FCR groups: the average requirements for the 25% most efficient animals were 13% higher than that of the 25% least efficient animals during the whole test, reaching 0.90 to 0.95 g/MJ NE at the beginning of the test, which is slightly greater than usual feed recommendations for growing pigs. Model parameters were moderately heritable (0.30±0.13 to 0.56±0.13), except for the precocity of growth (0.06±0.08). The parameter representing the quantity of feed at 50 kg BW showed a relatively high genetic correlation with RFI (0.49±0.14), and average protein deposition between 35 and 110 kg had the highest correlation with FCR (−0.76±0.08). Thus, growth and FI dynamics may be envisaged as breeding tools to improve feed efficiency. Furthermore, improvement of feed efficiency should be envisaged jointly with new feeding strategies.

Genetic parameters for litter size, piglet growth and sow's early growth and body composition in the Chinese-European line Tai Zumu.

Genetics of piglet growth in association with sow's early growth and body composition were estimated in the Tai Zumu line. Piglet and sow's litter growth traits were calculated from individual weights collected at birth and at 3 weeks of age. Sow's litter traits included the number of piglets born alive (NBA), the mean piglet weight (MW) and the standard deviation of weights within the litter (SDW). Sow's early growth was measured by the age at 100 kg (A100), and body composition included backfat thickness (BF100). A main objective of this study was to estimate separately the direct genetic effect (d) and the maternal genetic effect (m) on piglet weight and daily weight gain during lactation. Variance components were estimated using the restricted maximum likelihood methodology based on animal models. The heritability estimates were 0.19 for NBA, 0.15 and 0.26 for SDW and MW at 3 weeks and 0.42 and 0.70 for A100 and BF100. The NBA was almost independent from SDW. Conversely, the A100 and BF100 were correlated unfavourably with SDW (rg <-0.24, SE<0.12). A stronger selection for litter size should have little effect on litter homogeneity in weights. Selection for lean growth rate tends to favour heterogeneity in weights. The direct effect on piglet weight at birth and daily weight gain accounted for 12% (h(²) (d) = 0.02) and 50% (h(²) (d) = 0.11) of the genetic variance, respectively. The association between d and m for piglet weight was not different from zero at birth (rg = 0.19, SE = 0.27), but a strong antagonism between d and m for daily weight gain from birth to 3 weeks was found (rg = -0.41, SE = 0.17). Substantial direct and maternal genetic effects influenced piglet growth until weaning in opposite way.

Evaluation of the rates of mineral accretion per kilogram of body weight gain and net energy intake for two genetic lines of barrows and gilts from 20 to 125 kilograms body weight

<h2>ABSTRACT</h2> Two genetic lines of barrows and gilts with different lean growth rates were used to determine BW and mineral growth from 23 to 125 kg BW. The experiment was a 2 × 2 × 5 factorial arrangement of treatments conducted in 2 replicates. Six pigs from each sex and genetic line were killed at approximately 25-kg intervals from 23 kg BW to 125 kg BW. At slaughter, tissues were collected and weighed. All components were ground and frozen until analysis for mineral, lipid, and protein content. The allometric function, mineral mass=a BW^b, provided the best fit to the data. The linear form of the allometric equations was evaluated for the interactions of the regression coefficients with genetic lines and sex. Daily NE intakes were estimated based on the daily protein and lipid accretion rates. Allometric growth coefficients for the mineral mass were different for each sex and genetic line for Ca (P < 0.05). Interactions of BW and genetic line were found for Se, Zn, S, and K. The high-lean gain pigs had greater rates of mineral accretion per predicted unit of energy intake. In several cases, the predicted ratio of mineral accretion to NE intake were from 10 to 20% greater for the high-lean than the low-lean gain pigs at 25 kg BW and increased to 20 to 50% from 100 to 125 kg BW. These results support the need for genetic population-specific mineral nutrient recommendations.

Effects of restricting energy during the gilt developmental period on growth and reproduction of lines differing in lean growth rate: Responses in feed intake, growth, and age at puberty1

The overall objective was to compare reproductive performance through 4 parities of gilts developed with ad libitum access to feed or with restriction of energy to 75% of ad libitum intake. Effects on growth and pubertal development are reported. The experiment was a 2 × 2 factorial with 661 gilts. One-half of the gilts (n = 330) were allowed ad libitum access to feed from weaning to breeding at 235 d of age (AL), and 331 littermates were developed with ad libitum access to feed to 123 d of age and then restricted to 75% of ad libitum intake to 235 d of age (Res). Diets for gilts on regimen AL were formulated to meet requirements for growth. All nutrients except energy and selenium were increased in the diet fed to gilts on regimen Res so that nutrient intake per unit of BW was expected to be similar to that of gilts on regimen AL. Sires of all gilts were from an industry maternal line. Dams were either an industry Large White-Landrace cross, or Nebraska selection Line 45, producing gilts denoted as LW/LR and L45X, respectively. Traits were recorded every 2 wk. Recording of feed intake and BW began at 53 d of age, and recording of backfat (BF) and LM area (LMA) began at 123 d of age. Estrus detection began at 140 d of age to determine age at puberty (AP). The G:F ratio from 123 to 235 d of age for gilts on the AL regimen was greater (0.269 vs. 0.257, P < 0.01) than for gilts on the Res regimen; the greatest difference occurred in the first 2-wk period following feed restriction. The LW/LR gilts were heavier, had less BF, and had greater LMA than L45X gilts, but interactions with feeding regimen and period of development existed. Feed restriction reduced BW, BF, LMA, and ratio of BF to BW, but had little effect on ratio of LMA to BW. More L45X gilts than LW/LR gilts (98 vs. 93%, P < 0.01) and more gilts developed on regimen AL than regimen Res (98 vs. 91%, P < 0.01) expressed estrus. Mean age at puberty was 178.6 d for LW/LR and 173.0 d for L45X gilts (P < 0.01) and 174.1 d for regimen AL and 177.5 d for regimen Res (P < 0.05). The Res regimen delayed pubertal development. Subsequently, it will be important to determine effects on reproduction through 4 parities.