Five Holstein cows in early lactation were used in a 5 x 5 Latin square design to study substitution of soybean hulls for portions of forage or concentrate in diets. The control diet consisted of (DM basis) 10% alfalfa hay, 40% corn silage, 25% high moisture corn, 23% protein supplement, and 2.3% vitamins and minerals. Soybean hulls were used to replace approximately 25 and 50% of the forage or concentrate DM in the control ration. The DMI decreased linearly as soybean hulls replaced forage. The DM and OM flow to the duodenum and apparent and true digestion of OM in the stomach were similar among treatments. Ruminal pH was similar among treatments, but concentrations of NH3 N decreased linearly when soybean hulls replaced forage. Total VFA concentrations were similar when soybean hulls replaced forage but showed a positive quadratic response when soybean hulls replaced concentrate. Microbial N averaged 59% of NAN flow and showed a negative quadratic response when soybean hulls replaced concentrate. Flows of total AA and total essential AA to the duodenum were not altered when soybean hulls were fed. Yields of milk and milk components were similar among treatments; hulls can be used effectively to replace forage or concentrate in lactation diets.
The purpose of this research was to examine the effects of various amounts of CP and RUP on AA flow to the small intestine and milk yield of lactating dairy cows. The first trial was a 5 x 5 Latin square design using five ruminally and duodenally cannulated multiparous cows. Diets contained chopped alfalfa hay, corn silage, high moisture corn, solvent-extracted soybean meal, and specially processed soybean meal (60.2% RUP). Soybean meal replaced high moisture corn to increase dietary CP from 14.5 to 16.5 or 18.5%, and specially processed soybean meal replaced solvent-extracted soybean meal in diets containing 16.5 or 18.5% CP to provide 6.2, 7.3, 6.7, and 8.3% RUP. Increasing dietary CP increased the flows of all AA to the duodenum. Increasing dietary RUP increased flows of Arg, His, Lys, Phe, Asp, and Glu to the duodenum. In a second trial, 36 cows were fed diets similar to those used in trial 1. Increased amounts of RUP in diets tended to increase milk yield because of improved protein status, improved intake of metabolizable energy, or both.
Combinations of physical and chemical methods were evaluated for their ability to remove particle-associated microorganisms (PAM) from saline-washed ruminal digesta solids (SWRDS). Physical methods included chilling and storage, homogenization, multiple extraction, and agitation with marbles. Chemical methods included use of low pH, Tween 80, formaldehyde, methanol, tertiary butanol, and methylcellulose. Microbial removal from SWRDS was determined directly by using epifluorescence microscopy and indirectly by measuring removal of diaminopimelic acid and total purines. Different combinations of methods resulted in removals of 46 to 82% for particle-associated bacteria (PAB), 52 to 98% for particle-associated protozoa (PAP), and 60 to 83% for PAB plus PAP. Two methods were considered most effective, based on microscopy; both removed similar amounts of PAB (79 to 82%) and PAB plus PAP (80 to 83%). In one method, SWRDS were stored for 24 h at 4 degrees C in a solution of pH 2 saline, .1% Tween 80, 1.0% methanol, and 1.0% tertiary butanol. In the other method, SWRDS were incubated for 30 min in .1% methylcellulose before storage for 24 h at 4 degrees C in pH 2 saline, .1% Tween 80, and 1.0% methanol. Common to both treatments was subsequent homogenization of the suspensions for 15 s followed by washing the digesta solids seven times with the treatment solutions. Both methods resulted in values that exceeded those reported previously for removal of PAM from ruminal digesta solids.
Four Holstein cows, fitted with ruminal and duodenal cannulas, were used to determine the effects of supplemental feather meal and blood meal on ruminal fermentation and flows of N and AA to the duodenum. The basal diet contained (DM basis) 9.9% chopped alfalfa hay, 39.7% corn silage, 34.7% cracked corn, 8.2% corn starch, 2.1% vitamins and minerals, 4.4% casein, and 1% urea. A combination of feather meal and blood meal (3:1 on an N basis) was used to replace 0, 33, 67, and 100% of the casein and urea in the basal diet in a Latin square design. Intakes of DM, OM, and N were similar for all diets. Flows of total N, NAN, individual AA, total AA, and total essential AA were unaltered as supplemental feather meal plus blood meal increased. Flows of microbial N tended to decrease, but flow of non-ammonia, nonmicrobial N increased as supplemental feather meal plus blood meal increased. Increased proportions of dietary feather plus blood meal decreased the proportions of Ile, Lys, Met, and Thr in duodenal digesta. Molar percentages of ruminal pH and VFA were unchanged, but concentrations of ruminal NH3 N decreased linearly as supplemental feather meal plus blood meal increased. For the diets fed in this study, inclusion of one-third of the supplemental protein from feather plus blood meal resulted in maximum flows of NAN and microbial N to the small intestine.
This study investigated the effects of amounts of RDP and branched-chain VFA on milk production and DMI by 32 early lactation Holstein cows fed diets based on corn silage and corn. All supplemental dietary protein was supplied by animal protein by-products and urea. Hydrolyzed feather meal and ring-dried blood meal served as sources of supplemental protein and were fed in a 3:1 ratio on a N basis. The experimental design was a completely randomized design with a 2 x 2 factorial arrangement of treatments. Main factors were percentage of RDP (8.0 vs. 9.5% of dietary DM) and amount of branched-chain VFA in the diet (0 vs. 90 g/d per cow). Urea was used to adjust the amount of degradable CP. Individual DMI, milk production, and milk composition were monitored during wk 5 to 19 of lactation. Ruminal fluid and blood were collected to examine the treatment effects on ruminal VFA patterns and plasma urea N concentrations. The DMI, total milk production, and milk component yield were unaffected by treatments. The molar percentages of isobutryate, isovalerate, and n-valerate increased when branched-chain VFA were fed, and concentrations of urea N in plasma increased with higher percentages of RDP. A combination of feather meal and blood meal can be used as supplemental protein to support high milk production (> 37 kg/d) in early lactation. No production benefits were observed by increased dietary RDP or branched-chain VFA.
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