Effects of moisture content on temperature stability and microbial population growth over time in a dry cow total...

Controlling energy with high-fiber diets throughout the entire dry period is a nutritional strategy aimed at preventing overconsumption of nutrients, but this may result in lower moisture content. Conversely, TMR with high moisture content are more prone to spoilage, especially under elevated environmental temperatures. High temperatures signal spoilage caused by microorganisms present in the TMR, which generate heat and diminish the ration's nutrient value. Therefore, the objective of this study was to evaluate the effects of the addition of water to a dry cow TMR containing wheat straw (37% of total dietary DM) on TMR temperature and microbial populations. Three separate runs were conducted, each with six 3.78-L buckets randomly allocated to 2 treatment groups (n = 3 per treatment): NW (with no water added; 49% DM) and WW (with 7.3 kg of water added to the mixture; 43% DM). Temperature recording began immediately after filling the buckets with their corresponding treatments using data loggers (n = 3 per bucket; Thermochron iButtons, iButtonLink, Whitewater, WI), placed at the bottom, middle, and top of each bucket. The average temperature for all locations was used. Data loggers were set to record at 5-min intervals and summarized as hourly averages for 24 h. In addition, data loggers (n = 3) were placed outside of the buckets to register ambient temperature. Samples of TMR were collected at 0, 6, 12, 18, and 24 h after the mixture was prepared and placed into buckets. Three samples per treatment were composited at each time point and the composites were plated for yeast, total bacteria, and clostridial counts. Data were analyzed using the MIXED procedure in SAS (SAS Institute Inc.). There was no treatment effect for TMR temperature (NW = 29.1°C ± 0.76°C and WW = 30.6°C ± 0.76°C). A main effect of time point (h) was observed for TMR temperature, total bacteria, and yeast. The TMR temperature tended to be higher for WW (34°C ± 1.56°C, 35°C ± 1.59°C, 35°C ± 1.57°C, 35°C ± 1.49°C) than NW (29°C ± 1.56°C, 29°C ± 1.59°C, 30°C ± 1.57°C, 30°C ± 1.49°C) at 16, 17, 18, and 19 h, respectively. In contrast, NW had increased yeast counts compared with WW. Overall, water addition to a dry cow TMR appeared to affect feed temperature after 16 h of its preparation and reduced yeast growth over time but did not affect total bacterial or clostridial counts.