The molecular mechanisms underlying rumen epithelial adaption to high grain diets are unknown. To gain insight into the molecular mechanisms governing epithelial adaptation, mature non-lactating dairy cattle (n = 4) were transitioned from a high forage diet (HF; 0% grain) to a high grain diet (HG; 65% grain). After the cattle were fed the HG diet for three weeks, they returned to the original HF diet which they were fed for an additional three weeks. Continuous ruminal pH, ruminal volatile fatty acids and plasma beta-hydroxybutyrate were measured on a weekly basis and rumen papillae were biopsied from the ventral sac to assess alterations in mRNA expression profiles. The subacute form of ruminal acidosis was diagnosed during the first week of the HG period (4.6 ± 1.6 hours per day below pH 5.6), but not during weeks 2 and 3, thereby indicating ruminal adaption to the HG diet. Total mRNA expression of rumen papillae collected during the grain challenge was examined using Bovine Affymetrix microarrays. Pathway analysis of microarray results revealed that enzymes involved in cholesterol synthesis and ketogenesis were co-ordinately down-regulated from the first to third week of the HG period. The expression signature of six genes representing the key branch points of ketogenesis and cholesterol biosynthesis were confirmed using quantitative real-time PCR. A network analysis of expression results indicated that the coordinated expression of ketogenic and cholesterolgenic genes may be under the transcriptional control of sterol regulatory element binding proteins. To our knowledge, this is the first paper utilizing transcriptomic data to reveal potential metabolic mechanisms involved in rumen epithelial adaptation during ruminal acidosis.

The increased use of synthetic amino acids (AAs) in swine diets makes it important to better define requirements. A starter pig performance study was conducted to identify the optimal ratio of dietary standardized ileal digestibility (SID) isoleucine to SID lysine (Ile:Lys) between 10 and 25kg body weight. Nine experimental diets varied in SID Ile and Lys levels: diets 1-4 and 9 had SID Ile of 0.40, 0.46, 0.52, 0.58 and 0.64% respectively with SID Lys of 1.18% and diets 5-9 had SID Lys of 0.70, 0.82, 0.94, 1.06, and 1.18% respectively with SID Ile of 0.64%. Pigs were housed 4 per pen (2 barrows and 2 gilts, unrelated) and experimental diets were fed ad libitum for 21 days. Blood samples were collected for plasma urea nitrogen (PUN) analysis on days 7 and 21 from 2 pigs per pen. Least squares analysis was completed on the pooled data using linear and quadratic models to fit breakpoints for SID Ile and Lys that achieved optimal performance. Average daily gain (ADG) was optimized at SID Ile 0.49% (P<0.0001) and average daily feed intake (ADFI) at 0.48% (P<0.0001). Breakpoints were not found for Lys for any growth measurements including PUN. SID Ile at day 7 was optimized at 0.50% (P<0.0001) for PUN. Lys was limiting in all diets which affected optimal SID Ile levels. However, the optimal SID Ile:Lys ratio is estimated at 0.42 for 10 to 25kg pigs on barley and wheat based starter diets despite Lys being limiting.

This study was conducted to evaluate effects of mannan oligosaccharide (MOS) on immune function and disease resistance in pigs. In the in vitro experiment, a MOS, glucan fraction (GluF), and a mannan rich fraction (MRF) were investigated and alveolar macrophages (AMf) from donor pigs or MOS-fed pigs were used. TNF-a production activated by MOS (458 pg/mL) or GluF (376 pg/mL) was highest at the level of 0.5 mg/mL, while TNF-a response to MRF (164 pg/mL) peaked at 2.5 mg/mL. Polymyxin B, an anti-inflammatory substance inhibited TNF-a production induced by LPS or GluF, but not by MOS. MOS alone activated AMf to produce TNF-a, but suppressed lipopolysaccharide (LPS)-induced TNF-a and enhanced LPS-induced IL-10. AMf-produced TNF-a induced with LPS or polyinosinic:polycytidilic acid was inhibited by MRF. LPS-stimulated AMf from MOS-fed pigs produced less TNF-a and more IL-10. In the in vivo experiment, nursery pigs were assigned to one of four treatments in a 2 x 2 factorial arrangement [diet: 0% and 0.2% MOS; PRRSV: with and without]. PRRSV decreased pig performance and leukocyte counts and increased inflammatory mediators and rectal temperature (RT). In contrast, MOS was associated with rapidly increased numbers of leukocyte populations at 3 and 7 d post-inoculation (DPI). MOS reduced the RT at 7 DPI and TNF-a at 14 DPI in infected pigs. These results suggested that MOS had immuno-stimulating and -modulating effects and caused the pigs to quickly respond to a viral challenge at the early stage of infection and alleviated PRRSV-induced effects on G:F and fever.

This trial aimed to evaluate the effects of replacing a true protein source (pelleted sunflower meal) with a non-protein nitrogen source (Optigen 61650) in feedlot fed "bolita" calves. The study was carried out on the Don Tomás Farm, located in San Alberto, San Andrés de Giles County, 100 km west of Buenos Aires, Argentina. Forty Aberdeen Angus calves, with an average initial weight of 210 ± 9.6 kg and approximately 10 months of age, were used in the trial. A completely randomized experimental design was used, with 2 treatments and 2 replicates (10 animals/replicate). Treatments were: T1 – Pelleted sunflower meal as a protein source (DM basis: 70.5% corn grain, 26% pelleted sunflower meal, 2% wheat meal and 1.5% vitamin-mineral mixture with monensin); and T2 ¬ Optigen as a protein source (70.5% corn grain, 26.65% pelleted wheat bran, 1.35% Optigen and 1.5% vitamin-mineral mixture with monensin). The experimental period lasted for 95 days, with the first 7 days used for adaptation. The animals were individually weighed at the beginning and at the end of the trial, before the morning feeding. The data were submitted to ANOVA using the GLM procedure (SAS, 2000) and the means were compared by Tukey test (P<0.05). There were no differences between treatments in terms of final live weight (308.5 vs. 309.3 kg for T1 and T2, respectively, SEM= 2.01; P= 0.78), live weight gain (1.16 vs. 1.17 kg/d; SEM= 0.023; P= 0.81), feed conversion (7.64 vs. 7.59 for T1 and T2, respectively), and carcass yield (56.6 vs. 56.4%; SEM= 0.39; P= 0.76). In addition, the feces from the animals fed Optigen showed numerically lower starch concentrations (5.71 vs. 3.81%; SEM= 1.46; P= 0.24), and similar protein and dry matter concentrations (17.9 vs. 18.9%; SEM= 0.93; P= 0.34 and 14.2 vs. 15.0%; SEM= 0.65; P= 0.41 for T1 and T2, and DM and protein, respectively), compared to the animals fed pelleted sunflower meal. It was concluded that under the conditions of this study, Optigen successfully replaced a true protein source in feedlot fed "bolita" calves, typical of an Argentinean feedlot system.