Effects of Rumen-Undegradable Protein and Feed Intake on Nitrogen Balance and Milk Protein Production in Dairy Cows

Abstract

An experiment was designed to determine the response of milk protein production and N utilization in dairy cows to supplementation of a predominantly rumen-undegradable protein (RUP) mixture with a fixed amino acid (AA) pattern and the response to the amount of feed intake. The experiment was designed as a 6 x 6 Latin square with a 3 x 2 factorial arrangement of treatments. The factors were three concentrations of RUP supplement (4.5, 14.9, and 29.1% of dry matter intake) and two levels of feed intake restriction (10 and 20%) of the basal diet. The supplement was designed to approximate a postruminal AA pattern that was similar to bovine caseins for Met, Lys, Phe, His, and Thr. Measurements were made during the last 5 d of each 21-d period. Milk protein production responded linearly as the concentration of RUP supplement in the treatment diet increased within the given range. The difference in feed intake restriction did not affect milk protein production. Efficiency of N utilization for milk production exceeded 30% for cows fed the lowest RUP supplement. Results indicated that there is an opportunity to increase milk protein production by using RUP formulations that are balanced for AA while minimizing waste N excretion.

Long-term effects of feeding diets without mineral phosphorus supplementation on the performance and phosphorus excretion in high-yielding dairy cows

“…1 kg) taken and stored at -20°C for later P analysis. Urine was collected using indwelling bladder catheters (26 Fr., 75 mL; CR Bard Inc. Covington, GA) using a modification of the method described by Crutchfield (1968), i.e., leaving the catheter in place, unconnected to the collection tubing for 24 h prior to collection as described by Wright et al (1998). Distilled water was used to inflate the catheter balloon.…”

The effect of jugular or abomasal infusion of amino acids on milk yield in lactating cows fed a protein deficient diet

“…III). It is known that cows underfed in protein excrete less urinary N [17,49] given both reduced absorption of ammonia and decreased hepatic catabolism of amino acids [29]. In the present study, the protein deficiency occurring with ingested protein plus infusions of amino acids was planed to ensure that any difference between infusion sites would not be masked by an excess of protein, creating a maximal response situation.…”

Apparent transfer efficiency of docosahexaenoic acid from diet to milk in dairy cows

“…A 3 × 2 factorial arrangement of treatments was used: three levels of a supplement (containing fish meal), and two levels of feed restriction of the basal diet. Restriction of the basal portion of the diet was intended for other purposes (Wright et al 1998) and was not anticipated to affect apparent transfer efficiency of DHA; however, its effect is reported statistically for completeness. The basal diet used across all treatments consisted of (percent as-fed basis): 4% straw, 60.6% corn silage, 33.6% high-moisture corn, 0.19% NaCl, 0.83% mineral and vitamin premix, 0.67% limestone, and 0.09% KCl.…”

“…Six Holstein cows were used in this experiment, following the guidelines of the Canadian Council on Animal Care. Full details of the experimental design and diets were reported by Wright et al (1998). A 3 × 2 factorial arrangement of treatments was used: three levels of a supplement (containing fish meal), and two levels of feed restriction of the basal diet.…”