Can water source and quality affect nutrient digestion?

This study was conducted to evaluate the water source quality and a water treatment system to improve water quality for dairy cattle on the rate of ruminal fermentation and nutrient digestibility. One gram of dried ground TMR fed to lactating dairy cows was placed in a 50 μm Dacron bag, heat sealed, and then placed in a 500-mL Ankom gas fermentation bottle (GFB) containing ruminal fluid and treatment buffer to measure the rate and extent of ruminal nutrient digestion. Treatments were as follows: control, laboratory distilled water (DW); untreated ground water (UGW) from a local South Dakota dairy; treated ground water (TGW) using an H₂O₂ system; and municipal water (MW) supplied to the South Dakota State University Dairy Research and Teaching Farm (Brookings, SD). The experimental design was a randomized complete block design replicated using individual GFB as experimental units and replicated with 4 blocks. Ruminal fluid was collected from 2 ruminally cannulated cows fed the same TMR and strained through 4 layers of cheesecloth. Fifty milliliters of ruminal fluid mixed with 200 mL of Mould's buffer prepared from each water source were added to the GFB and incubated in a circulating water bath at 39°C. Gas measurements were collected every 5 min for 30 h. After 30 h, fermentation was arrested and the Dacron bags were removed, rinsed, and dried. The gas production rate was greater for DW compared to the other treatments (14.2%, 9.23%, 9.52%, and 9.66%/h for DW, UGW, TGW, and MW, respectively). Total VFA (mM) and acetate production were lower in DW compared with MW. The DM digestibility (82.0%, 81.6%, 80.8%, and 81.6%, for DW, UGW, TGW, and MW, respectively) tended to be lower for TGW water compared with DW water, with all other treatments being intermediate and similar. The NDF digestibility was similar for all treatments. Thus, water source and quality can affect the rate of ruminal microbial fermentation and nutrient digestion, which in turn can affect digestion estimates. However, the use of a water treatment system may still be a postruminal benefit to the animal beyond ruminal digestion.