Hepatic response to increased exogenous supply of plasma amino acids by infusion into the mesenteric vein of Holstein-Friesian cows in late gestation

The hepatic responses of late gestation, dry dairy cows to acute (6 h) infusions of an amino acid (AA) mixture (Synthamin; 0.0, 1.1, 2.2, 4.4, 8.8 and 17.6 mumol/min) into the mesenteric vein were determined. Neither blood flow nor O2 consumption across the portal-drained viscera (PDV) and liver was significantly altered by infusion. Similarly, there were no effects on net absorption, or hepatic removal, of acetate, propionate, butyrate or NH3. Glucose PDV appearance was unchanged but hepatic glucose production increased (P = 0.032) by 0.2 mumol/min per mumol/min of AA infused. Additional extraction of alanine, glycine (both infused) and glutamine (not infused) by the liver was sufficient to account for most of the extra C required for glucose synthesis. The N that would be liberated from these glucogenic AA would also account for a large proportion of the increase in urea-N produced in response to the AA infusion. This supports the concept of a correlation between gluconeogenesis and ureagenesis. Furthermore, the amide-N liberated from the extracted glutamine would contribute up to 0.17 of hepatic NH3 flux and assist in balancing N inputs into the carbamoyl phosphate and arginosuccinate entry points of the ornithine cycle. Rates of fractional extraction of the various AA by the liver were best fitted by linear equations, indicating that even at the highest rates of administration (approximately twice maximal physiological absorption) the transport systems were not saturated. Hepatic fractional extractions of infused essential AA were highest for methionine (0.83) and phenylalanine (0.87) with the lowest proportion removed observed for valine (0.25), leucine (0.30), lysine (0.31) and isoleucine (0.49). For the non-essential AA, the highest apparent fractional extractions were for glycine (0.73), arginine (0.79) and tyrosine (0.63) followed by alanine (0.54), proline (0.47) and serine (0.37). Hepatic removal of AA-N exceeded the increase in urea-N formation such that, at the highest rate of infusion, approximately 10 mmol/min of the extracted AA was apparently available for hepatic anabolism, more than is required to account for assumed increases in liver mass and export protein synthesis. Similarly, the amount of AA available for peripheral tissue protein gain, when assessed against phenylalanine supply as the limitation, would be the equivalent of a maximum of 0.5 g protein retained/min (6 mmol AA-N/min). This would provide sufficient AA for replenishment of peripheral (muscle) protein stores plus support of the placenta and fetus.     

Effects of maternal exercise on fetal activity in late gestation

Sixty malignant non-Hodgkin's lymphomas originating in the upper aerodigestive tract have been analyzed for their cytologic type, immunophenotype and association with the Epstein-Barr virus (EBV). The majority of these tumors were B-cell lymphomas of blastic cytology (78%) with the exception of lymphomas in the parotid gland. Large B-cell lymphomas were the most frequent encountered in the sinonasal region and Waldeyer's ring. Twelve lymphomas were of T- or T/NK (natural killer)-cell lineage. They were in the nasal cavity and the paranasal sinuses (4), the tonsil (5), and the oral cavity (3). Epstein-Barr sequences were detected in five angiocentric T/NK-lymphomas, one peripheral T-cell lymphoma, one lymphoma of lymphomatoid granulomatosis type, one large B-cell lymphoma, and in a lymphoroliferative disorder in an HIV-positive patient. These results suggest that EBV is not involved in lymphomagenesis of B-cell tumors, but is associated with angiocentric T/NK-cell lymphoma in the upper aerodigestive tract.     

Prediction of excretion of manure and nitrogen by Holstein dairy cattle

A compilation of N balance data (n = 1801) was partitioned into four groups to define the mean excretion of manure and N and to develop empirical equations to estimate these excretions from Holstein herds. Mean excretion of manure for cows that averaged 29 kg/d of milk production was 3 kg/d per 1000 kg of body weight (BW) more than the value for dairy cows reported by the American Society of Agricultural Engineers; N excretion was 0.09 kg/d per 1000 kg of BW higher than the value reported by the American Society of Agricultural Engineers. Mean excretion of manure and N for cows that averaged 14 kg/d of milk production and that for nonlactating cows were substantially lower than the values reported by the American Society of Agricultural Engineers. Growing and replacement cattle excreted 10 kg/d per 1000 kg of BW more manure and 0.11 kg/d per 1000 kg of BW more N than was reported by the American Society for Agricultural Engineers for beef cattle. Estimation of manure and N excretion was more accurate than mean values when using regression equations that included variables for milk production, concentration of crude protein and neutral detergent fiber in the diet, BW, days in milk, and days of pregnancy. Equations that contained intake variables did not significantly affect predictions of manure and N excretion, and the use of such equations is discouraged unless dry matter intake is measured and not estimated. Accurate estimates of excreta output could improve the planning of storage and handling systems for manure and the calculation of nutrient balances on dairy farms.     

Evaluation of serum apolipoprotein C-III concentration by enzyme-linked immunosorbent assay and its higher concentration in cows during midlactation than during the nonlactating stage

OBJECTIVE: To determine serum apolipoprotein C-III (apoC-III) concentration in cows in various stages of lactation by use of an ELISA. SAMPLE POPULATION: Sera obtained from 29 Holstein cows during early lactation, 65 cows during midlactation, 42 cows during late lactation, and 23 cows during the nonlactating stage. PROCEDURE: A 7.3-kd bovine apoC-III antiserum raised in rabbits was purified by affinity chromatography, and an ELISA was developed. RESULTS: In the immunoblot analysis, the antiserum reacted with the 7.3-kd apoC-III and moreover with another 8.2-kd apoC-III isoform. The 2 isoforms of apoC-III were also indistinguishable in the developed ELISA, the 2 proteins being measured as total apoC-III. In the ELISA for serum apoC-III concentration, addition of 2-mercaptoethanol to the coating buffer (50 mM sodium carbonate buffer, pH 9.6) was required. Mean+/-SEM bovine serum apoC-III concentration (microg/ml of serum) was 71.6+/-12.1 for the early lactating stage, 115+/-14.0 for the midlactating stage, 104+/-18.8 for the late lactating stage, and 55.3+/-8.4 for the nonlactating stage. Concentration of apoC-III was significantly (P < 0.05) higher in cows during midlactation than in cows during the nonlactating stage and was correlated negatively with serum triglyceride concentration (r = -0.479; P < 0.01) and positively with total cholesterol (r = 0.421; P< 0.05) and phospholipids (r= 0.415; P< 0.05) concentrations. CONCLUSIONS: Changes of apoC-III concentration in various stages of lactation suggest that this apolipoprotein is involved in a function related to lactation.     

Metabolism of oxytocin in rat uterus and placenta in late gestation

Concentrations of oxytocin (OT) peptide increase in rat uterine tissues at the time of parturition. We have measured the rate of OT metabolism in these tissues in late gestation to determine whether a decrease in OT catabolism is responsible for the increase in OT concentrations. Uterine and placental tissues were obtained from groups of rats at Days 16, 19, 21, 21.5, 22, and after delivery of the first pup. Delivery usually occurs in the early afternoon of Day 22. Some animals were treated with the estrogen receptor blocker tamoxifen, which will delay parturition by approximately 24 h. Cytosolic and microsomal preparations obtained using ultracentrifugation were incubated with radiolabeled OT. Metabolites were separated using HPLC, and enzyme kinetic parameters were calculated. OT was actively metabolized in both uterine and placental tissues. Total oxytocinase activity was similar in the two tissues. In uterine tissues, activity was greater in the cytosolic fractions. In placenta, activity was evenly distributed between the cytosolic and microsomal fractions. The cytosolic fractions of each tissue contained predominantly post-proline endopeptidase activity, whereas the microsomes contained predominantly aminopeptidase activity. There was a slight trend to decreasing oxytocinase activity with advancing gestation in both subcellular fractions, but this was statistically significant only in the microsomal fraction. The maximal decline in activity was only 25-50%. Tamoxifen treatment had no effect on oxytocinase activity. We conclude that rat uterine and placental tissues contain post-proline endopeptidase and aminopeptidase activities that metabolize OT. It is doubtful that changes in these activities are major factors in regulating the increase in OT concentrations measured in rat intrauterine tissues at the time of parturition.     

Protein requirements of sheep in late pregnancy: partitioning of nitrogen between gravid uterus and maternal tissues

The objective of this study was to quantify effects of maternal protein nutrition on N accretion or loss in conceptus and maternal tissues of ewes during late pregnancy. Ewes, pregnant with twins, were fed low (LP, 79 g CP/kg DM), medium (MP, 116 g CP/kg DM), or high (HP, 157 g CP/kg DM) protein diets, each with an estimated ME concentration of 2.7 Mcal/kg DM, between d 111 and 140 of pregnancy; all ewes had been fed the same diet (2.7 Mcal ME, 120 g CP/kg DM) for the previous 30 d (d 80 to 110). Dry matter intakes were varied (LP = 1.0, MP = 1.2, and HP = 1.4 kg/d) according to predicted energy costs of protein deposition for each diet. Nitrogen accretion was estimated by comparative slaughter (d 140 minus d 110) and by collection of excreta between d 120 and 130. Fresh weights of maternal and gravid uterine tissues were measured at slaughter, before proximate analysis of these components. Whole-body N retention was directly and linearly related to N intake, but efficiency of deposition of apparently absorbed N decreased linearly with increasing N intake (LP, .79; MP, .70; HP, .62). Nitrogen accretion in the gravid uterus, maternal viscera, and mammary gland was significantly less in LP than in MP or HP ewes. Nitrogen balance in maternal carcass tissues was linearly related to N intake, ranging from a negative value in LP ewes to a positive value in HP ewes (LP, -63 g; MP -39 g; HP, 55 g). These data provide the basis for estimating N requirements for protein accretion in the conceptus and in maternal tissues during late pregnancy. They also highlight the capacity of maternal carcass tissues to mobilize or deposit amino acids in response to variations in dietary protein supply.     

Effect of diseases on the culling of Holstein dairy cows in New York State

The effect of seven diseases on culling was measured in 7523 Holstein cows in New York State. The cows were from 14 herds and had calved between January 1, 1994 and December 31, 1994; all cows were followed until September 30, 1995. Survival analysis was performed using the Cox proportional hazards model to incorporate time-dependent covariates for diseases. Different intervals representing stages of lactation were considered for effects of the diseases. Five models were fitted to test how milk yield and conception status modified the effect of diseases on culling. Covariates in the models included parity, calving season, and time-dependent covariates measuring diseases, milk yield of the current lactation, and conception status. Data were stratified by herd. The seven diseases and lactational risks under consideration were milk fever (0.9%), retained placenta (9.5%), displaced abomasum (5.3%), ketosis (5.0%), metritis (4.2%), ovarian cysts (10.6%), and mastitis (14.5%). Older cows were at a much higher risk of being culled. Calving season had no effect on culling. Higher milk yield was protective against culling. Once a cow had conceived again, her risk of culling dropped sharply. In all models, mastitis was an important risk factor throughout lactation. Milk fever, retained placenta, displaced abomasum, ketosis, and ovarian cysts also significantly affected culling at different stages of lactation. Metritis had no effect on culling. The magnitude of the effects of the diseases decreased, but remained important, when milk yield and conception status were included as covariates. These results indicated that diseases have an important impact on the actual decision to cull and the timing of culling. Parity, milk yield, and conception status are also important factors in culling decisions.     

Effects of antipyrine on umbilical and regional metabolism in late gestation in the fetal lamb

OBJECTIVE: Antipyrine has been used extensively in fetal metabolic studies and is now known to inhibit prostaglandin synthesis; therefore we wished to determine the effects of antipyrine on fetal umbilical and regional metabolism. STUDY DESIGN: Chronically catheterized fetal lambs were randomly assigned to antipyrine (n = 6) or control (n = 5) groups. Animals in the antipyrine group were infused with antipyrine (mean +/- SD 9.6 +/- 0.9 mg/min for 165 +/- 38 minutes), and control group animals were not infused. Measurements were made of fetal blood gases, oxygen content, glucose, lactate, lower-body blood flow, upper-body flow distribution, and substrate uptakes across the umbilical and hind limb circulations. The unpaired t test, correlation coefficient, and regression analysis were used for comparisons. RESULTS: There were no differences in antipyrine and control group animals with respect to blood gases, metabolite levels, umbilical blood flow, or umbilical uptakes. Hind limb blood flow (p < 0.10) and oxygen uptake (p < 0.05) were lower and lactate production was higher (p < 0.01) in antipyrine animals than in control group animals. Duration of antipyrine exposure correlated directly with hind limb lactate production (r = 0.85, p < 0.001) and inversely with hind limb oxygen uptake (r = -0.65, p < 0.05). The distribution of blood flow within the fetal upper body also differed between groups, with higher cardiac distribution in the antipyrine group (p < 0.025). CONCLUSIONS: Antipyrine does not affect umbilical metabolism but does affect carcass metabolism and fetal blood flow distribution.     

Effect of zinc deficiency and varying zinc supplements on resorption and retention in dairy cows

5 lactating cows were used in a trial to investigate the process of Zn absorption and Zn retention under conditions of Zn deficiency and variations in Zn supplementation. The apparent Zn absorption was found to be markedly increased if the animals were fed a Zn deficient semisynthetic diet containing 6 mg Zn per kg of dry matter during the depletion period. Apparent Zn absorption continued to rise with continuing Zn depletion. Over a period of 6 weeks of Zn depletion the mean rate of Zn absorption was 58% with increases from 51% to 64% between the 1st and 6th week of experiment. After 19 weeks of Zn depletion 75% of the supplemented zinc were absorbed. With a Zn supply of 22 ppm and 54 ppm the rate of apparent Zn absorption decreased to 51% and 44% while still higher Zn supplements, up to 436 ppm, produced only a slight further decline down to 40%. The absolute Zn balances were shown to be directly associated with the level of Zn supply, all the more so because a linear relationship was found to exist between the levels of alimentary zinc supplementation and absolute Zn retention. Under conditions of Zn deficiency the cows exhibited a negative Zn balance, where animals with the highest milk yields showed the most negative Zn balances and remained for the longest period in the negative phase. With increasing periods of Zn depletion a homeostatic mechanism of Zn regulation in the organism of the animals became more and more pronounced so that at advanced stages of Zn depletion Zn retention of some extent occurred.     

Can oral contraceptive steroids influence the elimination of nifedipine and its primary pryidine metabolite in humans?

OBJECTIVE: To investigate the influence of oral contraceptives on cytochrome P450 3A4 (P450NF) activity. METHODS: In 23 healthy women, the pharmacokinetics of nifedipine and its main metabolite dehydronifedipine in plasma were assessed after a single oral dose, prior to and after intake of one of two oral contraceptive formulations, one containing 2 mg dienogest and 0.03 mg ethinylestradiol (group A) and the other containing 0.125 mg levonorgestrel and 0.03 mg ethinylestradiol (group B). RESULTS: While the intake of two oral contraceptives for 21 days did not influence the plasma concentration-time curve of unchanged nifedipine, mean AUC0-23.5 h and the mean Cmax values of dehydronifedipine were significantly lower in both groups tested/(24% in group A and 25% in group B). This observation may indicate a reduced formation rate of metabolites and reflects an inhibition of cytochrome P450 3A4 activity. The activation of the same or other metabolic degradation mechanism(s) could explain this result. CONCLUSION: The investigation presented demonstrates the importance of metabolite measurement when in vivo studies are undertaken to investigate different influences on drug metabolizing ability.     

Efficiency of energy and nitrogen loss and gain in mature cows

Our objective was to quantify the energy and nitrogen balances of mature cows fed a fixed amount of forage. Six cows were assigned to each of two treatments. At time 0, control cows received 83.55+/-.52 g of chopped brome hay x (BWkg)(-.75) x d(-1). Feed intake remained fixed (9,103+/-277 g/d) over the entire 224 d of the study. At time 0 treated cows received 82.10+/-1.26 g of chopped brome hay x (BWkg)(-.75) x d(-1) (9,083+/-113 g/d). After time 0, treated cows were offered 65% of the time-0 feed intake for the first 112 d (Phase 1) and 135% of the time-0 feed intake for the last 112 d (Phase 2). Treatments were designed so that the total amount of feed received during the 224 d was the same for each treatment. Additional balance measurements were made on d 28, 56, 84, 112, 140, 168, 189, and 224. Although treatment groups differed within phases for cumulative heat production, control cows did not differ from treated cows in total heat produced during the 224-d study (P = .60). Net retained energy over the entire 224-d period did not differ between treatments (P = .43). Treated animals retained more nitrogen than did control animals (P = .008). The increased efficiency of nutrient utilization during refeeding in cows allowed to fluctuate in weight offers the potential to develop feeding strategies that improve grazed forage utilization and reduce supplemental feed.     

Interactions of tallow and hay particle size on yield and composition of milk from lactating Holstein cows

An 18-wk lactation study was conducted to determine whether the effects of tallow on the lactation performance of dairy cows were influenced by particle size of hay in the ration. A total mixed ration containing 50% concentrate, 25% corn silage, and 25% alfalfa hay (dry matter basis) was fed to Holstein cows. Four total mixed rations were developed based on differences in the percentage of tallow in the concentrate and particle size of alfalfa hay: 1) 0% tallow, long-cut hay; 2) 0% tallow, short-cut hay; 3) 5% tallow, long-cut hay; and 4) 5% tallow, short-cut hay. Ration had no effect on dry matter intake, body weight gain or change in body condition score. Tallow increased milk and milk protein yields but reduced milk protein concentration. However, the effects of tallow on milk and milk protein yields were the same, regardless of hay length in the ration. A tendency for an interaction of tallow and hay particle size was detected for fat-corrected milk (FCM) because tallow increased FCM more when hay was short. Ration had no effect on volatile fatty acids in ruminal samples collected via a stomach tube. In this study, the effects of tallow on milk yield and composition from Holstein cows were the same, regardless of hay particle size in the ration. The tendency for tallow to increase FCM more when hay was short suggests at least a limited role of forage particle size in the determination of how fat supplements in dairy rations affect lactation performance.     

Quantification of dextropropoxyphene and its metabolite by HPLC in hair of overdose cases

Hair samples taken from 11 persons suspected to have died from an overdose of legal or illicit drugs were analysed. These hair samples were selected, because classical post-mortem toxicological investigations in blood revealed the presence of dextropropoxyphene (PPX) and its major metabolite norpropoxyphene (NPPX). For the hair analysis, hair strands were cut into segments of about 3 cm, washed with water and acetone, dried and pulverised. An aliquot of about 40 mg of those segments was incubated with acetate buffer pH 4.0 and beta-glucuronidase/arylsulfatase. After liquid-liquid extraction with hexane-3-methylbutanol (99:1), drugs were identified and measured by HPLC using piritramide as an internal standard. Preliminary assays showed that the limit of detection for PPX is below 1.0 ng/mg hair, the limit of detection for the metabolite NPPX being significantly higher (1.5 ng/mg). GC/MS, usually the method of choice for this kind of determination, was not chosen, because of the thermolability of PPX and its unspecific mass spectrum. From the hair of 11 persons, 24 segments were prepared and processed. Our results show that ten persons were found positive for PPX; moreover, when regarding the 24 segments, only three were found negative. PPX and NPPX concentrations were detected at maximal concentrations of 26.4 and 71.0 ng/mg hair respectively. Considering the ratio of PPX to NPPX for each person, we found more PPX than NPPX for three persons, whereas for seven persons we found more of the metabolite than its parent drug.     

Relationships between the number of small follicles prior to superovulatory treatment and superovulatory response in Holstein cows

In order to determine relationships between the number of small follicles prior to superovulatory treatment and superovulatory response, a total of 55 superovulations were induced in Holstein cows. The ovaries were examined ultrasonographically once 0-1.5 days before the initiation of superovulatory treatment. The number of small follicles 3-6 mm in diameter on both ovaries before superovulatory treatment was found to be significantly correlated with the numbers of corpora lutea after superovulation (r = 0.440, P < 0.001), total ova recovered (r = 0.503, P < 0.001) and transferable embryos recovered (r = 0.482, P < 0.001). These results indicate that a single ultrasonographic examination of follicles 3-6 mm in diameter prior to superovulatory treatment can be utilized to predict superovulatory response.     

The impact of pH on nitrogen retention in laboratory analysis of broiler litter

Land application of broiler litter must fully regard agronomic and environmental issues, which requires increased precision in all aspects of land application of poultry litter. Previous researchers note that litter experiences significant nitrogen loss due to ammonia volatilization during the drying process. Others note that pH of poultry houses and litter significantly affects nitrogen loss due to ammonia volatilization. Recent work shows that acidifying agents effectively reduce ammonia generation in poultry production facilities. This concept is used in this study to adjust the pH of broiler litter samples prior to drying to reduce nitrogen loss during the drying process. Samples from four sources were used. Untreated litter was compared to litter treated with Al2(SO4)3, (10:1 wet weight basis) either in small (10 g) or large (100 g batches). Both Al2(SO4)3 treatment methods significantly lowered litter sample pH. No significant differences were observed in litter moisture analysis values. Regardless of source, litter treated in small batches had significantly higher nitrogen values than untreated litter. Large batches of treated litter did not consistently have higher nitrogen values than untreated litter. Treatment of litter samples with Al2(SO4)3 prior to drying resulted in more accurate quantification of nitrogen in litter, which can ultimately result in more accurate utilization of litter in agronomic applications.     

Stereoselective disposition of hydroxychloroquine and its metabolite in rats

Racemic hydroxychloroquine-sulfate (HCQ-sulfate) was administered to rats orally. Groups of 9 male and 9 female rats received doses of 0, 8, 16, or 24 mg/kg/day for 6 weeks, followed by a reduction of the higher doses to 8 mg/kg/day for the duration of the study. Whole blood samples were collected at 0, 3, 6, 8, and 10 weeks, and eleven tissues were harvested after the tenth week. The concentrations and enantiomer ratios of the parent drug and three metabolites, desethylhydroxychloroquine (DHCQ), desethylchloroquine (DCQ), and bisdesethylchloroquine (BDCQ), were determined. The highest concentration of HCQ was found in the intestinal smooth muscle, and the lowest in the brain and adipose tissue. The highest concentrations of the metabolites were found in the liver, adrenals, and lung tissue. The metabolism of HCQ in the rats was found to be stereoselective with R/S > 1 for the drug and < 1 for the metabolites. Gender-specific differences in the proportions of the drug and its metabolites and their enantiomers in blood and tissue were found. Varying dosages appeared to have only a temporary influence on blood concentrations and not to effect the enantiomer ratios in blood. Only a limited number of tissues exhibited significant differences between dose groups. There were no observed differences in enantiomer ratios among the blood collection times.     

Effects of rumen-undegradable protein and feed intake on nitrogen balance and milk protein production in dairy cows

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.     

Effect of degradability of dietary protein and fat on ruminal, blood, and milk components of Jersey and Holstein cows

Twelve Holstein cows and 12 Jersey cows were used in six 4 x 4 Latin squares to investigate the effects of the degradability of dietary protein and supplemental dietary fat on milk components. Dietary dry matter contained 16% crude protein with two concentrations of ruminally undegradable protein (RUP) obtained by substituting blood meal for a portion of the soybean meal. Treatments were 1) 29% RUP, 0% added fat; 2) 29% RUP, 2.7% added fat (Ca soaps of fatty acids); 3) 41% RUP, 0% added fat; and 4) 41% RUP, 2.7% added fat. The dry matter of the total mixed ration fed at 1000 and 1400 h consisted of 30% corn silage, 29% alfalfa haylage, and 41% concentrate. Supplemental dietary fat depressed dry matter intake by 6.2%. Plasma urea N was greater at 0700 and 1600 h for Jerseys fed diets containing added fat and greater at 0700 h for Holsteins fed diets containing 41% RUP than for Holsteins fed 0% added fat and 29% RUP. When averaged across both breeds, milk production increased 7.1%, and production of 4% fat-corrected milk by Jerseys increased 8.4%, in response to added dietary fat. Milk protein was reduced when Holstein diets contained 41% RUP. Milk protein content was reduced 7.1 and 3.9%, and milk urea N was increased 4.9 and 8.5%, by added fat and 41% RUP in both breeds, respectively. Added fat reduced the concentration, but not the yield, of milk components. Substitution of blood meal decreased the concentration and yield of milk protein and casein N.