Chilling of whole rumen contents prior to preparation of strained rumen fluid enriched with particle-associated microorganisms resulted in rumen inoculum with the highest microbial dry weight, total bacterial counts, and degradation rates for casein and soybean meal. Strained rumen fluid, whole rumen contents blended with strained rumen fluid, chilled strained rumen fluid, and strained rumen fl...

Two 4 x 4 Latin square trials (4-wk periods; 16 wk total) were conducted to see whether supplementing rumen-protected Met (RPM; fed as Mepron) would allow feeding less crude protein (CP), thereby reducing urinary N excretion, but without losing production. In trial 1, 24 Holsteins were fed 4 diets as total mixed rations containing [dry matter (DM) basis]: 18.6% CP and 0 g of RPM/d; 17.3% CP and...

A series of trials was conducted to determine the effects of supplemental rumen-protected methionine (RPMet) and lysine (RPLys) on nutrient metabolism and performance. In situ RPMet N disappearance was less than 4% following 48 h of incubation and was not affected (P greater than .05) by diet or resultant ruminal pH differences, indicating that RPMet was well protected from ruminal microbial de...

Ruminant milk fat is of unique composition among terrestrial mammals, due to its great diversity of component fatty acids. The diversity arises from the eVects of ruminal biohydrogenation on dietary unsaturated fatty acids and the range of fatty acids synthesized de novo in the mammary gland. Forty to sixty per cent of milk fatty acids are long-chain (predominantly C18) fatty acids derived from...

An incomplete 8 x 8 Latin square trial (4-wk periods; 12 wk total) using 32 multiparous and 16 primiparous Holstein cows was conducted to assess the production response to crude protein (CP), digestible rumen-undegraded protein (RUP), and rumen-protected Met (RPM; fed as Mepron; Degussa Corp., Kennesaw, GA). Diets contained [dry matter (DM) basis] 21% alfalfa silage, 34% corn silage, 22 to 26% ...

Problem statement: Free Met as one of the most limiting AA in dairy cows would be mostly degraded in the rumen. This study was to determine the effect of different levels of RumenProtected Met (RPMet) on dairy performance and serum amino acid metabolism. Approach: Thirtysix Holstein cows in similar condition were randomly assigned to six experimental treatments with six replicates each. Levels ...

The objective of the present study was to determine the effects of rumen-protected choline (RPC) supplementation on body condition, milk production and milk choline content during the periparturient period. Thirty-two Holstein cows were allocated into two groups (RPC group - with RPC supplementation, and control group - without RPC supplementation) 28 days before the expected calving. Cows were...

The objective of this experiment was to compare metabolic and milk production parameters in dairy cows supplemented and nonsupplemented with rumen-protected choline (RPC) during the transition period. Twenty-three nonlactating, multiparous, pregnant Holstein cows were ranked by BW and BCS 21 d before expected date of calving and immediately were assigned to receive (n = 12) or not receive (cont...

A single injection of 15 g NaCl into the rumen, which increased the osmotic pressure of rumen fluid from 369 to 474 mOsmol/kg, resulted in a decrease in the transfer of blood urea into rumen fluid from 2.3 to 1.6 g N/day in sheep fed 50 g of chaffed oaten hay every hour. It is concluded that the reduced urea transfer was the result of a reduced urea input via saliva. The rumen wall remained vir...

A 3 x 3 Latin Square experiment was designed to compare 2 ways of bypassing the effects of the rumen with olive oil fatty acids in 'Manchega' dairy ewes. Treatments were a control diet, CaOFA (control diet plus 45 g of olive fatty acids as calcium soap), and OO (control plus 45 g/d of olive fatty acids as olive oil emulsified in skim milk) and bottle-fed to animals trained to maintain the retic...