Practical feeding applications and their effects on milk production, milk components, and rumen parameters in lactating dairy cow diets

With feed costs accounting for the greatest expense on a dairy farm, producers are constantly on the lookout for alternate feeds and additives that can be utilized in the diets of lactating cows at economically beneficial levels. To more closely evaluate practical feeding applications and their resulting effects on production and efficiency, two studies were conducted. The objective of Study 1 was to determine the effect of sudden additions of condensed distillers solubles (CDS) on milk production, milk components, and rumen measures of lactating dairy cows. Study 1 utilized 8 ruminally cannulated Holstein cows (166 ± 12 DIM) that were randomly assigned to treatments in a replicated 4 x 4 Latin square design with 21−d periods. Cows were fed control (CON) diets for a 14−d adaptation period and 1 of 4 treatment diets for a 7−d period with the last 3 d used for data collection. The treatment diets were CON, a diet containing 20% DDGS (DDGS), a diet with 2.5% CDS (CDS2.5), and a diet with 5.0% CDS (CDS5) on a DM basis. Milk samples were collected daily to determine milk components. Rumen samples were collected via rumen cannulas for determination of pH, volatile fatty acids (VFA) and NH3. Milk yield and fat percentage were similar between treatments, while cows fed the CON diet had greater, and DDGS tended to have, greater milk protein concentrations when compared with the CDS diets. Dry matter intake was greater for CON than CDS2.5 or CDS5 but was similar to DDGS. Rumen pH was lesser for CON than CDS5 and lesser for DDGS than either of the CDS diets. Rumen NH3 was greater for CON and DDGS and tended to be greater for CDS2.5 than for CDS5. Sudden additions of up to 5% added CDS in dairy cow diets decreased milk protein concentration and DMI without affecting milk yield or milk fat. Study 2 further evaluated practical feeding applications available to producers. The objective of Study 2 was to evaluate the effect of potassium carbonate supplementation on water intake, rumen measures and production of lactating dairy cows. In this study, 0% (Control), 0.75% (LowK), or 1.5% (HighK) potassium carbonate, on a DM basis, was added to the diets of 9 ruminally cannulated, late lactation Holstein cows (207 ± 12 DIM) that were randomly assigned to treatments in a replicated 3 x 3 Latin square design with 18−d periods with the last 4 d used for data collection. Milk yield was determined and milk samples were collected twice daily and analyzed for milk composition. Total rumen evacuations were conducted to determine total rumen digesta weight and DM, with rumen samples collected to determine VFA and NH3 concentrations as well as rumen pH. Milk, milk fat and protein yields showed quadratic responses with greatest yields for LowK. Dry matter intake had a quadratic response with cows on the LowK diet eating, on average, 1 kg/d more than either the CON or HighK diets. Water intake increased linearly as amount of K increased in the diet. Total and wet weight of rumen contents declined linearly and dry weight tended to decline linearly as K increased. Increasing dietary K in the diets of lactating dairy cows increased water consumption and rumen NH3 concentrations, while decreasing total water weight in the rumen. Understanding the effect of specific feed ingredients on lactating dairy cow performance is essential for producers to effectively meet the nutritional needs of their animals. Both studies indicate potential applications for producers when utilizing various options for feeding dairy cattle