LAUSR

Corn and wheat grains are two starch sources with considerably different ruminal digestion rates, which may lead to differing lipopolysaccharide (LPS) release in both rumen and hindgut affecting animal production. The objectives of this study were to (1) investigate the effects of different ruminal and faecal LPS concentrations induced by starch source (corn vs wheat) and starch concentrations (low vs high) on DMI, ruminal pH, ruminal fermentation patterns, milk production, and inflammatory responses; and (2) evaluate the possible translocation site of LPS in dairy goats. Eight lactating dairy goats with ruminal cannulas were used in a replicated 4 × 4 Latin square design with 2 × 2 factorial arrangement of treatments. Each experimental period consisted of 24 days long including 21 days for adaption and 3 days for data and sample collection. The four treatment diets were: corn and wheat grain combined with low (LS) and high grain starch (HS). Goats were fed equal amounts of a total mixed ration twice daily at 0700 hours and 1900 hours. Replacing corn with wheat in goat diet led to longer (P < 0.02) duration of ruminal pH <5.6, higher ruminal LPS (P < 0.05), but lower faecal LPS concentration. However, no differences between two grains in ruminal pH (mean, minimum and maximum), volatile fatty acids (VFA) and lactic acid concentration were observed. Goats fed HS diets had lower (P < 0.01) ruminal pH and higher (P < 0.01) ruminal concentrations of VFA and lactic acid, as well as higher (P < 0.01) ruminal and faecal LPS concentrations. Starch source did not affect DMI, milk yield and milk components whereas feeding HS versus LS diet had higher milk yield, lactose yield and improved milk efficiency (P < 0.05). Feeding wheat- versus corn-based diet showed only greater (P < 0.05) concentration of toll-like receptor-4, whereas feeding the HS versus LS diet consistently increased blood concentrations of amyloid A, haptoglobin, LPS binding protein, and LPS (P < 0.05). Analysis of Pearson correlation coefficients illustrated that the ruminal LPS concentration is more important than faecal LPS in inflammatory responses. In conclusion, replacing corn with wheat in lactating goat diet had negative impact on ruminal pH but little effects on fermentation characteristics and milk production. Increasing the dietary concentration of starch decreased ruminal pH status and thus increased risk of acidosis, whereas, feeding HS versus LS diets resulted in an improvement in milk yield, milk efficiency, and immunity response. Moreover, rumen acidosis induced by wheat based diet was accompanied with more severe inflammatory responses.