Hao Xiao

Background: Citrulline (Cit), an effective precursor of arginine (Arg), escapes hepatic catabolism to be almost completely absorbed into the systemic circulation, thereby being efficiently converted to Arg in the kidneys to enhance its systemic bioavailability. This study investigated the effects of dietary Cit supplementation on lactation performance in sows, as well as the underlying mechanisms related to intestinal health in their suckling piglets, using multi-omics analyses. Results: Dietary Arg and Cit supplementation significantly increased average daily feed intake of lactating sows. Milk fat content and plasma nitric oxide (NO) concentration increased significantly in the Arg group and the 40%Cit group ( P < 0.05), while milk threonine content increased slightly ( P = 0.084). Consequently, the average daily gain of suckling piglets over the 21-day lactation period was also significantly improved. Furthermore, maternal 40%Cit supplementation improved the intestinal health of offspring by enhancing jejunal morphology and upregulating the expression of the tight junction protein occludin ( P < 0.05), indicating a strengthened intestinal barrier. Mechanistically, this was achieved by activating the mTOR/S6 pathway in the piglets' jejunum. Maternal 40%Cit supplementation upregulated the expression of proteins related to mitochondrial fusion and fission (MFN2 and MFF, P < 0.05), and the protein expression of OPA1 showed an increasing trend ( P = 0.097), indicating the structural and functional status of mitochondria was improved. Maternal 40%Cit supplementation also modulated the gut microbiota of piglets, increasing the abundance of beneficial bacteria ( Lachnoclostridium ). Metabolomic analysis of sow milk identified 58 differential metabolites. Among these metabolites, palmitic acid levels were significantly increased and positively correlated with the abundance of Lachnoclostridium in the intestine ( P < 0.05). Conclusions: Dietary Cit supplementation enhanced sow lactation performance and improved intestinal barrier function in their offspring via activation of the jejunal mTOR/S6 pathway and improved mitochondrial structure and function in the piglet jejunum. These benefits were further supported by modulation of the gut microbiota and alterations in the milk fat and metabolome, ultimately promoting piglet growth.

Protein restriction, while beneficial for maternal healthspan, poses risks to offspring development during lactation. This study investigated whether valine (Val) supplementation in maternal low-protein diets (LPDs) alleviates offspring developmental deficits via a gut-mammary axis. Maternal LPD impaired offspring growth, jejunal morphology, and barrier integrity while reducing levels of secretory immunoglobulin A (sIgA) and related immune mediators in both piglet jejunum and sow mammary gland. LPD suppressed CCL28-mediated sIgA homing to the mammary gland, which was restored by optimal Val supplementation (Val/Lys ratio: 0.88%). Val elevated serum valine metabolites and corrected LPD-induced depletion of beneficial genera in milk and the offspring gut, promoting microbial colonization. Thus, Val regulates sIgA immunity and microbial composition via the lactational axis to enhance the intestinal health of offspring under maternal protein restriction.

Low-protein (LP) diets are increasingly recognized as a cost-effective and efficient strategy in the global livestock industry. Although previous studies have demonstrated that increased valine intake during pregnancy can improve reproductive performance and mammary gland development in gilts, the effect of the standardized ileal digestible valine-to-lysine ratio (Val/Lys) in LP diets during lactation is not well understood. A total of 60 lactating sows (Landrace × Large White; 4th parity) were randomized by backfat and weighed into 6 groups (n = 10): a standard protein group (17% crude protein, Val/Lys of 0.87) and 5 LP diet groups (14.3% crude protein, Val/Lys of 0.64, 0.74, 0.84, 0.94 or 1.04). The experiment lasted from day 0 of lactation to day 21 of lactation. The results indicated that LP diets reduced (P < 0.05) weaning weight and average daily gain (ADG) in piglets, as well as sow milk yield; whereas, increasing Val/Lys in LP diets improved (P < 0.05) these parameters. A linear model determined an optimal Val/Lys ratio of 0.94 in LP diets for maximizing piglet ADG. Low-protein diets decreased jejunal trypsin levels in piglets, which increased (P < 0.05) when Val/Lys was increased. Furthermore, LP diets reduced the expression of transporters (solute carrier family 38 member 2, SLC38A2) and metabolic enzymes (branched-chain amino acid transaminase 1 and 2, BCAT1 and BCAT2) in the piglet jejunum; conversely, increasing Val/Lys enhanced these expressions. Levels of L-valine, DL-arginine and L-threonine were found to decrease (P < 0.05) in response to LP diets, as revealed by the results from sow serum metabolites. However, these concentrations rebounded (P < 0.05) when Val/Lys was increased to 0.94. Correlation analysis revealed a positive association between sow serum valine metabolites and jejunal expression of SLC38A2, BCAT1 and BCAT2 in piglets. Low-protein diets also led to a decrease in the protein levels of metabolic enzymes (P < 0.05), which were improved (P < 0.05) by increasing Val/Lys. Finally, correlation analysis revealed a positive correlation between sow serum metabolites, jejunal enzyme expression and piglet growth performance. Collectively, growth performance in piglets may be impaired by LP diets for sows due to valine transport and catabolism being disrupted, whereas growth performance may be enhanced by increasing Val/Lys in LP diets via sow milk metabolites, thereby improving piglet digestion and absorption.

Constipation is a common issue in sows, characterized by dry and hard feces or prolonged absence of defecation, which exerts adverse effects on the overall health and reproductive performance of sows. While dietary neutral detergent fiber (NDF), due to its physicochemical properties, can enhance satiety and promote gastrointestinal health. The present study aims to determine the effect of different dietary NDF intake levels on reducing constipation without impairing the reproductive capacity of gestating sows. A total of 110 primiparous crossbred gilts (Landrace × Yorkshire) were randomly assigned to five groups with different NDF levels of 19.28% (Group A), 21.36% (Group B), 22.08% (Group C), 22.67% (Group D), and 23.43% (Group E), respectively. The daily feed intake was adjusted across groups to ensure a gradual increase in NDF intake from Group A to Group E, while maintaining consistent intake of other nutrients. The results revealed that dietary higher NDF intake (Groups D and E) significantly reduced the rates of constipation and stereotypic behaviors in gilts (p < 0.05). The experiment lasted for two parities, starting from day 30 of the first parity gestation to the end of parturition in the second parity. During the second parity, all groups were fed the same diet, and only the reproductive performance of the sows was observed and recorded. Notably, NDF intake had no significant effect on gilts’ first-parity reproductive performance. This study confirms that an appropriate increase in dietary NDF intake can alleviate constipation in gilts. This finding provides critical, targeted references for optimizing nutritional strategies in primiparous gilt management, filling the void in tailored dietary guidelines for this understudied group and offering a practical solution to balance production efficiency and animal stress in commercial pig farming.

This study aimed to investigate the effects of dietary ISF:SF ratio on reproductive performance, biochemical parameters, colostrum composition, and fecal microbial composition in gestating sows. A total of 30 multiparous sows were randomly allocated to three dietary treatment groups: 8% inulin diet (ISF:SF 1.14, Inulin group), 8% cotton fiber diet (ISF:SF 6.61, Cotton group), and 4% inulin + 4% cotton fiber diet (ISF:SF 2.37, Inulin + Cotton group). The results showed that, compared to the other groups, the Inulin group had a significantly higher number of piglets born alive, as well as increased plasma concentrations of acetic acid, butyric acid, hexanoic acid, and total short-chain fatty acids (SCFAs) (p < 0.05). Sows in the Inulin group had significantly lower fecal scores than those in the other groups from days 81 to 85 and from days 106 to 110 of gestation (p < 0.05). On day 90 of gestation, the serum levels of albumin, urea, uric acid, calcium, and phosphorus in the Inulin group were significantly lower than those in the other groups (p < 0.05). Additionally, the serum levels of triacylglycerol in the Inulin + Cotton Fiber group were significantly higher than those in the other groups (p < 0.05). However, there were no significant differences in serum concentrations of total protein, creatinine, glucose, cholesterol, HDL-cholesterol, or LDL-cholesterol among the treatments (p > 0.05). On day 110 of gestation, the serum content of urea, uric acid, calcium, and phosphorus in the Inulin group was significantly lower than those in the other groups (p < 0.05). Furthermore, the plasma levels of uric acid, triacylglycerol, and HDL-cholesterol in the Inulin + Cotton Fiber group were significantly higher than those in the Cotton Fiber group (p < 0.05), while the creatinine levels in the Inulin group were higher than those in the other groups (p < 0.05). No differences were observed in the composition and immune performance of colostrum (p > 0.05). Microbial sequencing analysis showed that dietary inulin supplementation to increase the proportion of soluble fiber significantly decreased the abundance of Firmicutes, Clostridia, Clostridiales, Lachnospiraceae, Streptococcaceae, and Streptococcus (p < 0.05). The abundance of short-chain fatty acid-producing microorganisms—Bacteroidetes, Bacteroidia, Bacteroidales, and Muribaculaceae—was significantly increased (p < 0.05). The results indicated that inulin supplementation decreased the dietary ISF:SF ratio, significantly alleviated constipation in sows, increased the number of piglets born alive, regulated intestinal microecology, and increased the plasma concentrations of short-chain fatty acids (SCFAs), including acetic, propionic, and butyric acids.

Transport stress prior to slaughter frequently induces a stress response, negatively affecting meat quality. This study investigated the impact of dietary potassium magnesium sulphate (PMS) supplementation during the fattening stage on the stress response and meat quality in finishing pigs subjected to transport stress. The experiment involved two phases. Initially, 48 finishing pigs (68.00 ± 0.40 kg) were randomly allocated into two groups: a control group receiving a basal diet (CON) and a PMS-supplemented group receiving the basal diet with 0.50% PMS. Each group was housed in six pens, with four pigs per pen. After 60 days of feeding, in the second phase, two pigs from each pen were randomly selected for slaughter, with one pig subjected to a 4 h transportation stress prior to slaughter. Pigs were categorized into four treatment groups based on diet and stress: (1) control without transport stress, (2) control with transport stress, (3) PMS-supplemented without transport stress, and (4) PMS-supplemented with transport stress. Serum, jejunum, and longissimus thoracis muscle (LM) samples were collected. The results indicated that dietary PMS supplementation did not significantly affect growth performance during the fattening stage (p > 0.05). However, following transport, the PMS pigs showed a reduction in norepinephrine and cortisol concentrations (p = 0.09, p < 0.05) and a significant increase in serum glutathione peroxidase (GSH-Px) activity (p < 0.05). Furthermore, PMS supplementation significantly increased serum catalase (CAT), total antioxidant capacity (T-AOC), alkaline phosphatase (AKP) activity, and high-density lipoprotein cholesterol (HDL-C) levels (p < 0.05), while significantly reducing cholesterol (CHO) levels (p < 0.05). Transport stress adversely affected the intestinal health of finishing pigs, as evidenced by a decrease in intestinal villus height (0.05 < p < 0.1), a condition ameliorated by PMS supplementation. Additionally, transported pigs exhibited a higher drip loss_24h in LM (p < 0.05), which was also alleviated through PMS supplementation. In conclusion, PMS supplementation mitigates transport stress and improves meat quality in finishing pigs.

This study aimed to determine the optimal dietary net energy concentration for the reproductive performance, immune function, milk composition, and gut microbiota of primiparous sows during lactation. Forty primiparous lactating sows (Landrace × Yorkshire) with similar body backfat thicknesses were randomly allocated into five treatment groups and fed diets with different dietary net energy concentrations of 10.05 MJ/kg, 10.47 MJ/kg, 10.89 MJ/kg, 11.30 MJ/kg, and 11.72 MJ/kg. The results showed that there were no differences in the performance of piglets, while there was a decrease in the daily feed intake of sows (p = 0.079, linear) as dietary net energy concentration increased. With the increasing dietary net energy concentration, the plasma insulin levels of sows increased (p < 0.01, linear), the plasma glucose levels tended to increase (p = 0.074, linear), and the blood urea nitrogen levels tended to decrease (p = 0.063, linear). Moreover, the plasma total superoxide dismutase activity of sows increased (p < 0.05, quadratic) and the plasma malondialdehyde content of sows decreased (p < 0.05, quadratic) by increasing the dietary net energy concentration. Interestingly, with the increase in dietary net energy concentration, the plasma immunoglobulin M content of sows increased, the milk immunoglobulin M, immunoglobulin G, immunoglobulin A and the percentage of milk fat increased (p < 0.05, linear), and the milk secretory immunoglobulin A content also increased (p < 0.05, linear and quadratic). The milk immunoglobulins and milk fat content of sows fed with net energy concentration of 11.72 MJ/kg were highest. Moreover, there were significant differences in the α-diversity, β-diversity, and relative abundance of gut microbiota in sows fed with different dietary net energy concentrations. At the phylum level, Spirochaetota and Bacteroidota in the gut microbiota of sows were mainly affected by increasing the dietary net energy concentration. Furthermore, the correlation analysis showed that milk immunoglobulin content had a significant negative correlation with the relative abundance of Bacteroidota, and plasma malondialdehyde content also had a significant negative correlation with the relative abundance of Spirochaetota. In summary, these results suggest that increasing the dietary net energy concentration to 11.72 MJ/kg can increase immunological substances in milk, improve milk quality, and alter the composition of gut microbiota in primiparous lactating sows.

The aim of this study was to determine the optimal SID Arg: Lys ratio for maximizing the reproductive performance, immunity and biochemical parameters of sows during gestation, the colostrum composition, and the performance of their offspring. A total of 174 multiparous sows were randomly allocated to five treatment groups varying in dietary SID Arg: Lys ratios (0.91, 1.02, 1.14, 1.25 and 1.38) through modification of the levels of Arg or alanine supplementation (the total level of nitrogen was the same in all treatments). The results showed that increasing the dietary SID Arg: Lys ratio increased the number of piglets born alive (p < 0.05, linear and quadratic). The number of stillborn piglets, the birth weight variation of born alive piglets, the birth interval (p < 0.05, linear and quadratic) and the number of mummies (p < 0.05, quadratic) reduced with increasing the dietary SID Arg: Lys ratio. Broken-line regression analysis indicated that the optimal SID Arg: Lys ratio requirement for gestating sows to maximize the number of piglets born alive was 1.25. The content of non-fat solid, total solid, protein, and energy in colostrum increased linearly and quadratically (p < 0.05) with increasing dietary SID Arg: Lys ratio. Additionally, when increasing the dietary SID Arg: Lys ratio, the concentration of IgA (p < 0.05, quadratic) and IgM (p < 0.05, linear and quadratic) of plasma increased at day 90 of gestation; IgG (p < 0.05, linear and quadratic) concentration increased at day 110 of gestation of sows. The dietary SID Arg: Lys ratio had an increasing effect (p < 0.05, linear and quadratic) on plasma insulin levels at day 90 of gestation. Furthermore, there were increases in plasma concentrations of nitric oxide and ornithine at day 110 of gestation, Arg at day 90 and 110 of gestation (p < 0.05, linear and quadratic) and total protein at day 110 of gestation (p < 0.05, linear) with increasing dietary SID Arg: Lys ratio. The results of our study indicated that increases in the dietary SID Arg: Lys ratio during gestation resulted in an increase in the number of piglets born alive, a decrease in birth intervals, and an improvement in immunity and colostrum composition. The optimal SID Arg: Lys ratio for gestating sows to maximize the number of piglets born alive was 1.25.