Effects of an abrupt increase of starch-rich concentrates in the diet of dairy cows on concentrations of volatile fatty acids in the rumen and large intestine and on myoelectric activity of the spiral colon

OBJECTIVES: To describe the effects of an abrupt increase of concentrates in the diet of dairy cows on myoelectric activity of the spiral colon and on fermentation patterns in the rumen and large intestine. ANIMALS: 6 healthy lactating Simmental x Red-Holstein cows. PROCEDURES: The diet of 6 cows implanted with bipolar electrodes in the spiral colon was changed from hay only to a ration of 50% hay:50% starch-rich concentrates during a period of 60 hours. Myoelectric activity of the spiral colon, concentrations of absolute and undissociated volatile fatty acids (VFA), and pH of ruminal and large intestinal contents were monitored before, during, and after the dietary change. RESULTS: Significant changes in patterns of myoelectric activity of the spiral colon were restricted to phases III and IV of the bovine migrating myoelectric complex and to propagation velocity. Significant alterations were not observed in pH or VFA concentrations in ruminal fluid, but pH decreased and VFA concentrations increased significantly in fecal specimens after the change of diet. CONCLUSIONS AND CLINICAL RELEVANCE: Although rumen fluid is of limited value for measurement of certain indicators of fermentation, fecal samples can be used for measurement of pH and VFA concentrations, which serve as indicators of fermentation patterns in the large intestine. Increased concentrations of VFA and low pH in large intestinal digesta have a minimal influence on myoelectric activity of the spiral colon. Increased luminal VFA concentrations are unlikely to play an important role in the etiopathogenesis of motility disorders of the large intestine in cattle.     

Effects of microalgae‐added diets on growth performance and meat composition of tilapia (Oreochromis mossambicus)

Two floating diets and one sinking diet were prepared for tilapia with local ingredients by extrusion or steam‐pelleting methods. Indoor and outdoor feeding trials were conducted to evaluate their effects on growth performance and quality of tilapia products. Local ingredients included defatted Haematococcus and Spirulina by‐products from Hawaii. The three diets, plus a commercial feed, were each assigned to three replicate tanks, and each tank (120 L) was stocked with 12 juvenile tilapia in an 8‐week indoor trial. The results showed that (1) the floating diet had significantly (P < 0.05) higher weight growth than the sinking diet; (2) increased inclusion of local microalgae by‐product (defatted Haematococcus) in floating diet from 12% to 24% significantly (P < 0.05) decreased tilapia weight growth; and (3) the three microalgae‐added diets obtained higher (P < 0.05) weight growth than the commercial feed, although they contained lower protein (36.9% to 37.7%) and lipid (7.1% to 8.1%) than the commercial feed (42.3%; 8.6%). The floating diet (containing 12% microalgae) and the commercial feed were also tested in outdoor green water tanks, simulating the commercial production conditions of local tilapia farms. Each diet had three replicate tanks (1200 L) stocked with 100 juvenile tilapia. The 12‐week trial showed that the local diet had significantly (P < 0.05) lower growth (12.0 g week^?1) than the commercial feed (14.8 g week^?1). All tilapia meat products were measured with low n‐3 fatty acid contents. These results provide important information for feed formulation and production using local ingredients for tilapia.