Abstract
Twenty-four lactating Holstein cows offered diets containing (1) no buffer (control), (2) 1.8% potassium bicarbonate, (3) 1.2% potassium carbonate, or (4) 1.5% sodium bicarbonate in the concentrate, consumed more diet 3 forage blend and complete ration in comparison one and comparison two, respectively. Concentrate intake was not affected. Rumen pH did not differ, while urine pH was greater with buffered diets. Diet 3 increased milk fat percentage over diet 4 during comparison one and over controls during comparison two, and increased fat-corrected and solids-corrected milk yield over diet 4 in both comparisons. In three continuous culture in vitro trials, diet 3 maintained pH comparably to diet 4, with no difference in volatile fatty acids. Twenty-four lactating Holstein cows offered .93, 1.29, or 1.53% dietary potassium during hot weather consumed more dry matter when fed 1.53% potassium vs. .93% potassium. Milk production and composition were not different. Potassium intake and fractional excretion increased, and fecal output as a percentage of intake declined with 1.53 and 1.29% potassium diets. Magnesium fractional excretion increased and fecal output declined with 1.29% potassium. Fecal sodium output as a percentage of intake decreased with 1.53% potassium. A comparison of 0, .5, and 1.0% potassium carbonate indicated no effect on dry matter intake or milk yield, but buffered diets increased milk fat percentage and depressed protein percentage. Rumen pH, volatile fatty acids or diet digestibility were not altered. In comparisons of (1) no buffer (control), (2) 1.5% sodium bicarbonate, (3) 1.25% potassium carbonate, or (4) 1.85% potassium carbonate in the total diet, twelve lactating Holstein cows consumed more of diets 2 and 4 than controls. Diet 4 resulted in a greater milk fat percentage than controls. There was no effect on milk yield. Buffered diets increased dry matter and fiber digestibilities over control. Diet 4 caused higher rumen pH's postfeeding than controls. Rumen volume or turnover was not altered. Diet 4 increased molar percentage of rumen acetate for 4 h postfeeding, reduced molar percentage of rumen propionate, and increased rumen acetate: propionate ratio. Treatments had no effect on blood acid-base balance or plasma magnesium.
West, Joe Williamson (1986). Potassium containing buffers as a source of potassium for ruminants during hot weather : effects on tolerance to heat stress and rumen fermentation. Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -24936.