Effects Of Dietary Methionine Levels And Source On The Growth And Intestinal Development In Sucking And Weanling Piglets

This study was conducted to determine the related mechanisms and responses of lactating sows and weaned piglets to diets with increased inclusion of methionine as DL-methionine (DLM) or its hydroxyl analog, DL-2-hydroxy-4-methylthiobutyrate (HMB). Three diets for sows and weanling piglets, respectively, were formulated. The control (CON) diets were formulated based on NRC (1998) nutrition requirements of lactation-sows and weaned piglets. The DLM and HMB diets were the CON diets plus DLM and HMB, respectively, at25%of the total sulfur amino acids (SAA) of the CON diets. Primiparous sows (LandracexYorkshire) with similar bodyweight and backfat thickness were fed the CON, DLM or HMTBA diet (n=6) from the postpartum day. Piglets from three of the six sows in each group were weaned at day21and28, respectively. At day14postnatal, piglets from the CON-, DLM-and HMB-fed sows began to have free access to the weaning diets CON, DLM and HMB, respectively. At day7,14and21postanal, milk and blood samples were collected from each sow, and blood, duodenum, jejunum, and ileum tissue samples were collected from piglets at day14,21,28and35postpartum. Base on the above samples, milk composition, free amino acid, intestinal morphology, antioxidant defense capacity and nutrient transport and metabolism related genes expression were determined. The main results were as follows:(1) Change in body status of sows and growth of sucking piglets:negative average bodyweight gain was observed in each group of sows during the first week postpartum, with significant (P<0.05) weight loss observed in the DLM group. The feed intake of sows were not different in the three groups (P>0.05). At day14, the bodyweight was higher in the HMTBA group than in the CON (P<0.05) and DLM (P=0.07) groups.(2) Milk composition, free amino acid profiles in blood and milk:at day14postpartum, the HMB-fed sows had higher milk protein levels than DLM-fed sows, and higher milk fat and lactose levels than the DLM-and CON-sows (P<0.05). Cysteine and taurine concentrations in milk was higher in the HMB-fed sows than the CON-fed sows. Compared with the CON-fed sows, DLM-fed sows had increased plasma homocysteine, glutamate, taurine, and urea concentration (P<0.05), but decreased lysine concentration (P<0.05), and HMB-fed sows had higher taurine (P<0.05) and methionine (P<0.10).(3) Intestine growth, antioxidant defense capacity, and gene expressions of sucking piglets:at day14postpartum, the ratio of villous height to crypt depth of each intestine section was higher in the HMB group than in the CON and DLM groups (P<0.05), and piglets in the HMB and DLM groups had more absolute number of goblet cells in jejunum and ileum than those in the CON groups (P<0.05). Piglets from the HMB-fed sows had up-regulated (P<0.05) expression of jejunum FZHUI fatty acid-binding protein than those from the CON-and DLM-fed sows, however, the expression of oxysterol binding protein-related protein10in jejunum was lower in the HMB and DLM groups than in the CON group (P<0.05). At day21, piglets in the HMB group had more absolute number of goblet cells in jejunum and higher ratio of villous height to crypt depth in duodenum and ileum than those in the DLM and CON groups (P<0.05). GSSG:GSH in jejunum of piglets was higher in the HMB group than in the CON and DLM groups (P<0.05) at day14and21postpartum, and the plasma GSH-Px activity in sows at day14and in piglets at day21postpartum was higher in the HMB groups than in the CON and DLM groups (P<0.05).(4) The effects of weaning and diets on performance of piglets:the feed intake of piglets was not different among groups in the first week after weanling (P>0.05), however, the HMB-fed piglets had higher feed intake than the CON-(P<0.05) and DLM-fed (P=0.09) piglets during the second week post-weanling (P<0.05). Moreover, piglets in the HMB group weighed more than those in the DLM (P<0.05) and CON groups (P=0.11).(5)The effec of weaning and diets on intestine growth,antioxidant defense capacity and related gene expression:at d7post-weaning, piglets weaned either at21-d old or at28-d old had decreased ratio of villous height to crypt depth (P<0.05), and increased plasma GSH-Px activity and jejunum GSSG:GSH (P<0.05). At day35, compared with the CON-and DLM-fed piglets, the HMB-fed piglets had increased jejunum and ileum villus height and villus height:crypt depth (P<0.05). Piglets in the DLM and HMB groups had more (P<0.05) absolute number of goblet cells in duodenum and ileum than those from the CON group. At day35postpartum, compared with the CON-and DLM-fed piglets, the HMB-fed piglets weaned at21-d old had enhanced (P<0.05) GSH-Px activity, and up-regulated (P<0.05) expressions of ubiquitin carboxyl-terminal hydrolase FAF-y, FZHUI fatty acid-binding protein intestinal and somatostatin precursor.Base on the above results, it could be concluded that:(1) Increased inclusion of methionine as HMB may promote growth of the sucking and weanling piglets, and increase feed intake of weanling piglets.(2) Increased inclusion of methionine as HMB could increase S AA in plasma of sows, and protein and fat content in milk. In contrast, DLM supplementation resulted in decreased lysine but increased homocysteine concentrations in sow plasma and lower protein and non-fat solid content in milk.(3) Increased inclusion of methionine as HMB could improve antioxidant defense capacities, alleviate intestinal dysfunction associated with weaning stresses, and enchanced growth and development of young intestine.