Effects of whole cottonseed, niacin, and niacinamide on in vitro rumen fermentation and on lactating Holstein cows.

In Experiment 1, effects of whole cottonseed (0, 5, 15, or 30% of the total ration DM) on in vitro ruminal fermentation showed increased ruminal pH and ammonia concentration but lowered microbial protein. Acetic acid concentration was greatest with diets of 15 and 30% whole cottonseed, but propionate and total VFA concentrations were reduced by increasing whole cottonseed from 0 to 30%. In Experiment 2, neither niacin nor niacinamide (0, 100, 200, or 400 ppm) altered substantially fermenter pH or ammonia concentration. Both niacin and niacinamide increased synthesis of microbial protein. Acetate and propionate concentrations were not altered by treatment. Total VFA concentration tended to be lower as concentration of niacin and niacinamide increased. In Experiment 3, 28 Holstein cows were used to determine the effects of supplemental niacin on feed intake, milk yield, and composition. Cows were fed individually complete mixed diets ad libitum containing either: 1) 0; 2) .015; 3) .03; or 4) .06% niacin. There was a trend for lower milk fat test with niacin supplementation. Milk protein percentage was higher without niacin than with niacin at .015 or .03% in the diet, but daily milk and protein yields were higher with .06% versus .015% of niacin. Supplemental niacin did not affect casein nitrogen, lactose or minerals percentage, or concentrations of plasma glucose and insulin.

Chilled drinking water effects on lactating Holstein cows in summer.

In Experiment 1, 12 multiparous lactating cows (six per group) were offered drinking water ad libitum at temperatures of 10 or 30 degrees C in a switchback design. The treatment group received 10 degrees C water from 1235 to 2000 h and was then changed to 30 degrees C water for the remaining 16.5 h/d. The control group received 30 degrees C water 24 h/d. Respiratory rates, rectal temperatures, and rumen motilities were measured at 1100, 1440, and 1810 h, 3 d/wk. Water consumed was recorded for 1235 to 2000 h and 2001 to 1234 h of the next day. Water consumption for the treatment group was 3.90 L/h per cow compared to 5.40 L/h per cow for the control group from 1235 to 2000 h. However, the 10 degrees C water absorbed 65.6 kcal/h more heat than the 30 degrees C water. No differences were found in respiratory rates, rectal temperatures, rumen motilities, or milk yield. Cows that drank 10 degrees C water consumed 3.67 kg of feed DM/100 kg of body weight compared with 3.36 kg of feed for the controls. In Experiment 2, the same two groups of cows were offered 9.5 degrees C water ad libitum for 24 h/d or 27.5 degrees C water for a 48 h comparison. The treatment group tended to consume more water than the control group and to have lower respiratory rates and body temperatures.

Potassium carbonate as a potassium source and dietary buffer for lactating Holstein cows during hot weather.

Twenty-four lactating Holstein cows were offered diets containing .93, 1.29, and 1.53% potassium during hot weather. Cows fed 1.53% potassium consumed more dry matter than cows fed either .93 or 1.29% potassium. Milk production and composition were not different. Potassium intake and fractional excretion increased, and fecal output as a percentage of intake declined with diets containing 1.29 and 1.53% potassium. Magnesium fractional excretion was least and fecal output greatest in cows fed 1.29% potassium. Fecal sodium output and fecal output as a percentage of intake was reduced by 1.53% dietary potassium. During comparison period 2, potassium carbonate at 0, .5, or 1.0% had no effect on feed consumption or milk yield, but buffered diets increased milk fat percentage and depressed milk protein percentage. No effects of buffers on ruminal pH, volatile fatty acids, or digestibility of dry matter or fiber were noted. Cows responded favorably during hot weather to potassium supplementation at 1.53% of the diet, but with high dietary potassium, effects on other minerals must be considered. Chloride, although present above requirements in all diets, was greater in the highest potassium diet.

Effects of potassium carbonate and sodium bicarbonate on rumen function in lactating Holstein cows.

Twelve multiparous lactating Holstein cows were used to compare effects of 1) no buffer, 2) 1.5% sodium bicarbonate, 3) 1.25% potassium carbonate, or 4) 1.85% potassium carbonate in total diet on rumen environment and liquid turnover, dry matter intake and digestibility, milk yield and composition, and blood acid-base balance. Cows fed buffered diets had greater dry matter intake and greater digestibility of dry matter, acid detergent fiber, and neutral detergent fiber than controls. Rumen pH was higher in cows fed buffers than in controls 2 to 4 h postfeeding, but buffered diets were not different. Rumen volume, osmolality, and liquid turnover were unaffected by dietary treatment. Molar percentage of rumen acetate was greater, propionate was less, and acetate:propionate ratio was greater in cows fed 1.85% potassium carbonate compared with other treatments. There were no treatment effects on milk yield, although milk fat percentage tended to be greater in buffered diets. Blood acid-base balance was not altered. Cows fed diets containing potassium carbonate performed similarly to those fed sodium bicarbonate. No adverse effects of potassium carbonate on rumen function or environment were observed. Potassium carbonate is an acceptable buffer and serves as a potassium supplement.

Influence of niacin and whole cottonseed on intake, milk yield and composition, and systemic responses of dairy cows.

Twenty-four Holstein cows (early postpartum) were used in a randomized complete block design with a 2 X 2 factorial arrangement of treatments to compare effects of nicotinic acid (niacin) and whole cottonseed. Cows were fed individually isonitrogenous complete mixed rations ad libitum, containing corn-soy concentrate, corn silage, chopped coastal bermudagrass hay, and either 1) 0% niacin and 0% whole cottonseed, 2) 0% niacin and 15% whole cottonseed, 3) .03% niacin and 0% whole cottonseed, or 4) .03% niacin and 15% whole cottonseed. Dry matter and energy consumption, actual milk yield, total milk solids, and milk fat yield were not affected by treatment. Either niacin or whole cottonseed increased milk fat percentage and 4% fat-corrected milk. Milk protein percentage and yield were higher with niacin supplementation but tended to be lower with cottonseed feeding. The milk protein depression with whole cottonseed was alleviated by niacin due to stimulation of mammary casein synthesis. Supplemental niacin tended to elevate glucose and insulin in blood plasma, but whole cottonseed tended to reduce these plasma components. Plasma urea nitrogen was higher in cows fed whole cottonseed. Plasma-free tryptophan tended to be slightly higher in cows receiving supplemental niacin.

Effects of drinking water temperature on physiological responses of lactating Holstein cows in summer.

Nine lactating Holstein cows were offered drinking water of 7.2, 15.6, and 23.9 degrees C in a 3 X 3 Latin square design in Experiment 1. Water was offered for 10 min at 1300 h to simulate time in a milking parlor. Water consumption declined as drinking water temperature decreased. Respiration rates decreased as the drinking water temperature decreased. In Experiment 2, 8 lactating Holstein cows were offered water of 12.8 and 26.7 degrees C in a 2 X 2 changeover design. Results were consistent with Experiment 1. In experiment 3, 16 lactating Holstein cows were offered drinking water of 10, 16, 22, and 28 degrees C in a 4 X 4 Latin square design. Water was offered for 10 min at 1400 h. Respiration rates and deep rectal temperatures were taken before and after watering. Water consumption declined as drinking water temperature decreased, but the cooling effect of the low temperature water was greater. Lower drinking water temperature decreased respiration rates postwatering. Deep rectal temperatures were not affected as drinking water temperature decreased. Both respiration rates and deep rectal temperatures began to increase within 40 min after watering, indicating a transient cooling effect of the chilled water.

Effects of drinking water temperature on production responses in lactating Holstein cows in summer.

During late summer, 24 lactating Holstein cows were offered 10 or 28 degrees C (control) drinking water ad libitum at 1400 h for 10 min to investigate the effects on respiration rates, body temperatures, dry matter intake, and milk production. Experimental design was a 2 X 3 factorial arrangement of the two drinking water temperatures with .8, 1.1, and 1.4% dietary potassium associated with another experiment. Following 1 wk adjustment and 1 wk standardization, cows were blocked by dry matter intake as a percentage of body weight within parity and randomly assigned to treatments within blocks. Cows were denied access to water from 0900 until 1400 h. Respiration rates and rectal temperatures were recorded before and after watering. Tympanic membrane temperatures (8/h) were recorded during the comparison period using 4 cows per water treatment. No interaction occurred between water and potassium. Water at 10 degrees C had a greater cooling effect than 28 degrees C water. No differences were found between treatments in respiration rates and rectal temperatures after drinking water was temperatures after drinking water was offered. Chilled drinking water decreased tympanic membrane temperatures, which remained lower longer. Cows that drank 10 degrees C drinking water increased dry matter intake and milk yield.

Effects of potassium buffers on feed intake in lactating dairy cows and on rumen fermentation in vivo and in vitro.

Twenty-four Holstein cows were used to compare acceptance of concentrates and complete rations containing 1) no buffer, 2) 1.8% potassium bicarbonate, 3) 1.2% potassium carbonate, or 4) 1.5% sodium bicarbonate in the concentrate. When concentrate and a forage blend were offered separately (comparison period 1), concentrate intake did not differ among treatments, but forage blend consumption and complete ration intake was greater with the potassium carbonate ration (comparison period 2). Rumen pH did not differ, but urine pH was higher in cows fed complete rations containing buffers. Cows fed potassium carbonate had higher milk fat percentages than cows fed sodium bicarbonate during the first comparison period and higher than controls during the second comparison period and produced more 3.5% fat-corrected milk and solids-corrected milk than cows fed sodium bicarbonate in both comparison periods. Milk protein percentage was lower in cows fed potassium carbonate diets as compared with those fed sodium bicarbonate diets, but total protein production was similar. In three continuous culture in vitro trials, potassium carbonate maintained fermenter pH comparably to sodium bicarbonate, and total volatile fatty acid and acetate production were similar.

Effects of amount of whole cottonseed on intake, digestibility, and physiological responses of dairy cows.

In Experiment 1, 27 lactating cows were fed complete rations ad libitum of 0, 15, and 30% whole cottonseed to examine the effects on intake, digestibility, blood gases, and blood metabolites. Dry matter intake declined linearly with increased cottonseed, but because of greater energy density, calculated net energy for lactation intake was not depressed significantly. Ether extract, crude protein, and calcium digestibility increased with cottonseed in the diet. Respiration rates declined with dry matter intake and increased cottonseed feeding; some blood gases were influenced by cottonseed feeding but not in a detrimental way. No data among 13 blood metabolites indicated effects of gossypol toxicity with 30% whole cottonseed in the diet. In Experiment 2, 24 dry, nonpregnant Holstein cows were offered complete rations ad libitum of 15, 35, and 55% whole cottonseed to measure responses in intake, respiration rates, and blood metabolites. The highest cottonseed diet significantly depressed intake of both dry matter and calculated net energy for lactation. Maximum dry matter from cottonseed eaten by an individual was 8.4 kg/d (average for 1 wk). Respiration rates declined parallel to intake. No evidence for gossypol toxicity was seen among data of 11 metabolites in blood.

Effect of lint on whole cottonseed passage and digestibility and diet choice on intake of whole cottonseed by Holstein cows.

Effects of rolling whole linted cottonseed and whole acid-delinted cottonseed on whole seed passage and digestibility were determined using 24 lactating Holstein cows. Whole seed passage averaged .74% in all cows fed whole linted seed during the standardization period and .45% in 6 cows fed whole linted seed during a comparison period, contrasted to 11.3% in 6 cows fed acid-delinted seed. Digestibility of ether extract was less in the 6 cows fed whole acid-delinted cottonseed. No advantage was for rolling whole linted cottonseed before feeding, but rolling was beneficial for whole acid-delinted cottonseed. Individual consumption of whole linted cottonseed by 18 nonpregnant, dry Holstein cows varied from .04 to 5.05 kg/day when two-choice options were given for cottonseed versus chopped coastal bermudagrass hay or corn silage, or a complete ration of 75% corn silage and 25% concentrate. No indication of gossypol toxicity was seen, but the large variation in each choice situation suggests it is desirable to blend cottonseed with other ingredients to ensure more uniform consumption.