Low crude protein formulation with supplemental amino acids for its impacts on intestinal health and growth performance of growing-finishing pigs

BACKGROUND

Low crude protein (CP) formulations with supplemental amino acids (AA) are used to enhance intestinal health, reduce costs, minimize environmental impact, and maintain growth performance of pigs. However, extensive reduction of dietary CP can compromise growth performance due to limited synthesis of non-essential AA and limited availability of bioactive compounds from protein supplements even when AA requirements are met. Moreover, implementing a low CP formulation can increase the net energy (NE) content in feeds causing excessive fat deposition. Additional supplementation of functional AA, coupled with low CP formulation could further enhance intestinal health and glucose metabolism, improving nitrogen utilization, and growth performance. Three experiments were conducted to evaluate the effects of low CP formulations with supplemental AA on the intestinal health and growth performance of growing-finishing pigs.

METHODS

In Exp. 1, 90 pigs (19.7 ± 1.1 kg, 45 barrows and 45 gilts) were assigned to 3 treatments: CON (18.0% CP, supplementing Lys, Met, and Thr), LCP (16.0% CP, supplementing Lys, Met, Thr, Trp, and Val), and LCPT (16.1% CP, LCP + 0.05% SID Trp). In Exp. 2, 72 pigs (34.2 ± 4.2 kg BW) were assigned to 3 treatments: CON (17.7% CP, meeting the requirements of Lys, Met, Thr, and Trp); LCP (15.0% CP, meeting Lys, Thr, Trp, Met, Val, Ile, and Phe); and VLCP (12.8% CP, meeting Lys, Thr, Trp, Met, Val, Ile, Phe, His, and Leu). In Exp. 3, 72 pigs (54.1 ± 5.9 kg BW) were assigned to 3 treatments and fed experimental diets for 3 phases (grower 2, finishing 1, and finishing 2). Treatments were CON (18.0%, 13.8%, 12.7% CP for 3 phases; meeting Lys, Met, Thr, and Trp); LCP (13.5%, 11.4%, 10.4% CP for 3 phases; meeting Lys, Thr, Trp, Met, Val, Ile, and Phe); and LCPG (14.1%, 12.8%, 11.1% CP for 3 phases; LCP + Glu to match SID Glu with CON). All diets had 2.6 Mcal/kg NE.

RESULTS

In Exp. 1, overall, the growth performance did not differ among treatments. The LCPT increased (P < 0.05) Claudin-1 expression in the duodenum and jejunum. The LCP and LCPT increased (P < 0.05) CAT-1, 4F2hc, and B0AT expressions in the jejunum. In Exp. 2, overall, the VLCP reduced (P < 0.05) G:F and BUN. The LCP and VLCP increased (P < 0.05) the backfat thickness (BFT). In Exp. 3, overall, growth performance and BFT did not differ among treatments. The LCPG reduced (P < 0.05) BUN, whereas increased the insulin in plasma. The LCP and LCPG reduced (P < 0.05) the abundance of Streptococcaceae, whereas the LCP reduced (P < 0.05) Erysipelotrichaceae, and the alpha diversity.

CONCLUSIONS

When implementing low CP formulation, CP can be reduced by supplementation of Lys, Thr, Met, Trp, Val, and Ile without affecting the growth performance of growing-finishing pigs when NE is adjusted to avoid increased fat deposition. Supplementation of Trp above the requirement or supplementation of Glu in low CP formulation seems to benefit intestinal health as well as improved nitrogen utilization and glucose metabolism.

Protein turnover in pigs: A review of interacting factors

Protein turnover defines the balance between two continuous and complex processes of protein metabolism, synthesis and degradation, which determine their deposition in tissues. Although the liver and intestine have been studied extensively for their important roles in protein digestion, absorption and metabolism, the study of protein metabolism has focused mainly on skeletal muscle tissue to understand the basis for its growth. Due to the high adaptability of skeletal muscle, its protein turnover is greatly affected by different internal and external factors, contributing to carcass lean-yield and animal growth. Amino acid (AA) labelling and tracking using isotope tracer methodology, together with the study of myofiber type profiling, signal transduction pathways and gene expression, has allowed the analysis of these mechanisms from different perspectives. Positive stimuli such as increased nutrient availability in the diet (e.g., AA), physical activity, the presence of certain hormones (e.g., testosterone) or a more oxidative myofiber profile in certain muscles or pig genotypes promote increased upregulation of translation and transcription-related genes, activation of mTORC1 signalling mechanisms and increased abundance of satellite cells, allowing for more efficient protein synthesis. However, fasting, animal aging, inactivity and stress, inflammation or sepsis produce the opposite effect. Deepening the understanding of modifying factors and their possible interaction may contribute to the design of optimal strategies to better control tissue growth and nutrient use (i.e., protein and AA), and thus advance the precision feeding strategy.

Evaluation of brown rice to replace corn in weanling pig diet

This study was conducted to evaluate the effects of brown rice (Japonica) on growth performance, nutrient digestibility, and blood parameters of weanling pigs. A total of 60 weanling pigs (28-day-old, 30 barrows and 30 gilts, 6.73 ± 0.77 kg body weight [BW]) were randomly allotted to 2 dietary treatments (6 pigs per pen; 5 replicates per treatment) in a randomized complete block design with the initial BW and sex as blocks. The dietary treatments were a typical nursery diet based on corn and soybean meal (CON) and the CON replaced 50% of corn with brown rice (BR). Pigs were fed respective dietary treatments for 5 weeks. For the last week of experiment period, pigs were fed respective dietary treatments containing 0.2% chromic oxide as an indigestible marker. Fecal samples were collected from randomly selected 1 pig in each pen daily for the last 3 d after the 4-d adjustment period. Blood was collected from randomly selected 1 pig in each pen on d 0, 3, 7, and 14 after weaning. Compared with pig fed CON diet, pigs fed the BR diet were found to have higher (p < 0.05) final BW, overall average daily gain, and apparent ileal digestibility (AID) and apparent total tract digestibility (ATTD) of dry matter and energy. However, there were no significant differences between the groups with respect to average daily feed intake, gain to feed ratio, frequency of diarrhea, and the AID and ATTD of crude protein during overall experimental period. Similarly, there were no significant differences on blood parameters between the groups. Thus, the findings of this study indicate that brown rice (Japonica) can be used to replace 50% of corn in the diet of pigs during the nursery period without negatively affecting growth performance, nutrient digestibility, or blood parameters.

Evolution of viscera and muscle fractional protein synthesis rate in lean meat selected hybrids and castrated Duroc pigs fed under moderate crude protein restriction

Differences in producing performance and organoleptic meat characteristics among pig genotypes and/or producing types are widely known. These parameters are also subjected to the animal's development, feeding and management. Detailed knowledge of the effects of production phase (PP), pig producing type (PT), dietary protein availability and their interactions on nutrient digestibility, nitrogen balance and protein metabolism is essential information to improve precision feeding techniques. The experiment was a 2 (PP) × 2 (PT) × 2 (diet) factorial design conducted with 32 male pigs, 16 entire F2 pigs progeny of Pietrain sires and Duroc × Landrace dams, and 16 castrated purebred Durocs belonging to two production phases (growing: 29.5 ± 3.19 v. fattening: 88.6 ± 6.26 kg BW), and assigned to one of two dietary CP levels, either standard (SP: 17% in growing and 15% in fattening) or low (LP: 15% in growing and 13% in fattening). Viscera and muscle fractional protein synthesis rates (FSRs; %/day) were conducted through a single infusion of 15% L-[ring-²H₅]-phenylalanine, with subsequent blood sampling from 12 to 40 min, and sample collection of liver, duodenum, biceps femoris and longissimus dorsi skeletal muscles after sacrifice. Fattening animals acquired a greater feed ingestion capacity, average daily gain (P < 0.01) and apparent ileal digestibility, whereas growing pigs showed higher FSRs in both viscera (duodenum and liver) and in longissimus dorsi. F2 pigs showed higher average daily gain, nitrogen retention rates and FSR in liver and longissimus dorsi (P < 0.01). Nevertheless, apparent ileal digestibility in all essential amino acids was lower in F2 compared with Duroc pigs (P < 0.05). Protein metabolism was barely influenced by dietary CP content, although animals fed LP registered the lowest apparent ileal digestibility for CP and also for most of the essential amino acids compared with SP-fed pigs. This information may reveal differences in amino acid requirements between both PTs, with Duroc pigs receiving excess of dietary amino acids.

Dietary protein level affects nutrient digestibility and ileal microbiota structure in growing pigs

This study aimed to determine whether dietary protein content influences pig health as indicated by ileal microbiota structure and coefficients of total tract apparent digestibility (CTTAD) of nutrients. Seventy-two gilts, with an initial body weight of 29.9 ± 1.5 kg, were used in this 42-day feeding study. Pigs were randomly allotted to one of three dietary treatments of corn-soybean meal contained 14, 16 or 18% crude protein (CP). As dietary CP content decreased, the CTTAD of most essential amino acids (AAs), except for arginine and histidine, increased linearly, while those of most nonessential AAs decreased linearly. The concentration of total short-chain fatty acids (SCFA) was higher in pigs fed the diet with 14% CP content than others. Ileal microbiota structure was changed by dietary treatments. In particular, at the phylum level, the relative abundance of Tenericutes in ileal digesta decreased as the dietary protein content reduced, while that of cyanobacteria increased. At the genus level, the relative abundance of Weeksella, Phaseolus acutifolius, Slackia, Sulfurimonas and Aerococcus showed significant differences among the three dietary treatments. In conclusion, ileal microbiota structure was changed by dietary protein content. Moderate reduction of protein intake can benefit gut health by enhancing the gut microbial fermentation and SCFA formation.

Effects of Long-Term Protein Restriction on Meat Quality, Muscle Amino Acids, and Amino Acid Transporters in Pigs

This study aimed to investigate the long-term effects of protein restriction from piglets to finishing pigs for 16 weeks on meat quality, muscle amino acids, and amino acid transporters. Thirty-nine piglets were randomly divided into three groups: a control (20-18-16% crude protein, CP) and two protein restricted groups (17-15-13% CP and 14-12-10% CP). The results showed that severe protein restriction (14-12-10% CP) inhibited feed intake and body weight, while moderate protein restriction (17-15-13% CP) had little effect on growth performance in pigs. Meat quality (i.e., pH, color traits, marbling, water-holding capacity, and shearing force) were tested, and the results exhibited that 14-12-10% CP treatment markedly improved muscle marbling score and increased yellowness (b*). pH value (45 min) was significantly higher in 17-15-13% CP group than that in other groups. In addition, protein restriction reduced muscle histone, arginine, valine, and isoleucine abundances and enhanced glycine and lysine concentrations compared with the control group, while the RT-PCR results showed that protein restriction downregulated amino acids transporters. Mechanistic target of rapamycin (mTOR) signaling pathway was inactivated in the moderate protein restricted group (17-15-13% CP), while severe protein restriction with dietary 14-12-10% CP markedly enhanced mTOR phosphorylation. In conclusion, long-term protein restriction affected meat quality and muscle amino acid metabolism in pigs, which might be associated with mTOR signaling pathway.