Effects of Grain Source and Starch Concentration in Dairy Goat Diet on Ruminal Fermentation, Milk Production and Inflammation.

The objective of this study was to evaluate the effects of grain (corn vs. wheat) and starch concentrations (low- vs. high-starch) on ruminal pH, milk production, and inflammatory response in dairy goats. Eight ruminally cannulated lactating goats (34 ± 3.1 kg of BW, 180 ± 8.2 day in milk) were used in a cross-over design with a 2 × 2 factorial arrangement. Each period lasted for 27 d. During the first 10 d, goats were fed low-starch (LS) diets (d 8 to 10 for data collection), from d 11 to 17 for transitioning to high-starch (HS) diet, from d 18 to 25 for feeding the HS diet, and d 25 to 27 for data collection. Goats were fed a total mixed diet ad libitum twice daily. Diets were formulated as isonitrogenous (13.6%) and isoenergetic with forage to concentrate ratio at 60:40 and 35:65, respectively, for LS (24%) and HS (39% starch, DM basis) diets. Data were analized using PROC MIXED procedure of SAS with model including diets as fixed effects and random effect of period and animal. Intake of DM (averaged 1.06 kg/d) was affected neither by grain source nor by starch concentration. However, goats fed HS vs. LS diet produced greater (P<0.05) milk (0.82 vs. 0.67 kg/d) and lactose (35.0 vs. 27.3 g/d). Ruminal pH (averaged 6.15) did not differ but duration of pH < 5.6 was longer (P<0.05) with wheat (232 min/d) than corn (140 min/d) diet. Ruminal pH was greater (6.16 vs. 5.87; P<0.05) and duration of pH < 5.6 was shorter (33 vs. 339 min) for HS than LS diets. Concentration of ruminal lipopolysaccharide (LPS) was greater (P<0.05) with wheat than corn diet (35.5 vs. 22.1 ×10³ EU/mL). Goats fed HS versus LS diet also had greater (P<0.05) LPS concentration in ruminal fluid (40.3 vs. 17.3 × 10³ EU/mL). Blood concentration of serum amyloid A (SAA, 75.7 vs. 62.7 μg/mL), haptoglobin (Hp, 96.3 vs. 91.6 μg/mL) and LPS binding protein (LBP, 2.3 vs. 1.6 μg/mL) were not affected by grain source, but goats fed HS vs. LS diet had more (P<0.05) SAA (89.3 vs. 49.1), Hp (116.7 vs. 71.2), and LBP (2.4 vs. 1.5 μg/mL). These results indicated that replacing corn with wheat in lactating goat diet had little impact on ruminal pH and milk production. However, increasing starch concentration in goat diets is beneficial to improve milk production and immune activity by stimulating inflammatory response.