Acute effects of an anionic diet on bone mineral homeostasis in the bovine.

Fifteen Friesian oxen between 12 and 18 months of age with a mean body mass of 240.7 kg were randomly assigned to diets containing 0.25% phosphorus (P) or less to evaluate the acute effects of an acidiogenic diet of -11.1 meq/100 g of diet dry matter, compared with a basiogenic diet of +25.6 meq/100 g or a control diet of +16.5 meq/100 g of diet dry matter calculated as (Na + K)-(Cl + S), on blood, bone and faecal P, calcium (Ca) and magnesium (Mg) for a period of 9 weeks. Blood, bone and faecal responses to an anionic diet are described. An inverse relationship existed between bone and blood Ca, in which there was resorption from bone with increased blood Ca in response to the anionic diet. The anionic treatment group demonstrated simultaneous increases in bone, blood and faecal P concentrations at various stages of the experiment compared to the cationic and control treatment groups. Results indicate independent absorption and resorption of Ca and P into and out of bone. There was wide variation in the bone Ca:P ratio between 2.02 and 1.51 among animals fed the anionic diet, with the Ca:P ratio following Ca values and not bone P values. Bone and blood P had a linear relationship with dietary cation:anion balance (DCAB), increasing as the diet became more anionic in nature, but faecal P was curvilinear with highest concentrations at -11.1 and +25.6 meq/100 g compared to +16.5 meq/100 g. Concurrent blood, bone and faecal P increases at some stages of the experiment indicate a P-sparing effect of the anionic diet and warrants further research into the long-term effects of anions in the diet, leading to their use as a possible addition to improved licks in P-deficient areas.

Copper metabolism of holstein and jersey cows and heifers fed diets high in cupric sulfate or copper proteinate.

Eight Holstein and 8 Jersey primiparous cows (3 d postcalving) and 8 Holstein and 8 Jersey growing heifers were randomly assigned to 1 of 8 treatments in a 2 x 2 x 2 factorial arrangement to compare Cu metabolism between Holsteins and Jerseys and the bioavailabilities of Cu in Cu proteinate and CuSO4. The variables were Holstein or Jersey, Cu supplementation at 5 or 80 mg/kg of DM, and supplements of CuSO4 or Cu proteinate. Jerseys had higher hepatic Cu concentrations than did Holsteins on d 60 (346 vs. 303 micrograms/g of DM). At the high Cu supplementation, hepatic Cu increased more rapidly, and content was higher in Jerseys than in Holsteins by d 60 (520 vs. 439 micrograms/g of DM). On d 0, plasma Cu concentrations were 0.99 and 0.80 microgram/ml, and, on d 60, concentrations were 0.96 and 0.88 microgram/ml for Jerseys and Holsteins, respectively. Overall, serum ceruloplasmin oxidase activity was greater for Jerseys than for Holsteins. Jersey cows and heifers also had greater hepatic Fe (208 vs. 173 micrograms/g of DM) and lower hepatic Zn (82 vs. 91 micrograms/g of DM) than did Holstein cows and heifers at d 60. The bioavailability of Cu in Cu proteinate and CuSO4 was the same. Plasma Cu concentration and ceruloplasmin have limited value as indicators of Cu status and availability to dairy cows and heifers.

Effects of a supplemental liquid yeast product on feed intake, ruminal profiles, and yield, composition, and organoleptic characteristics of milk from lactating Holstein cows.

A liquid yeast product (about 11% DM), produced as a by-product of riboflavin synthesis, was incorporated into a TMR at three concentrations to determine the maximal inclusion rate and acceptability as a feed supplement in diets of lactating cows. Twelve Holstein cows in midlactation were randomly assigned to TMR treatments containing (as-fed basis) 1) no yeast product (control), 2) 20% dietary yeast product, or 3) 40% dietary yeast product in a 3 x 3 Latin square design with 3-wk periods. Dietary DM contents were 90, 74.2, and 58.4% for the 0, 20, and 40% yeast product TMR, respectively. The control TMR was based on a 45:55 ratio (DM basis) of mixed concentrate and chopped alfalfa hay. The DMI decreased linearly with increasing percentages of dietary yeast product. Milk yield and milk protein percentage were not altered by inclusion of the dietary yeast product. Milk fat tended to respond quadratically to increases in the percentage of dietary yeast product in the TMR. The supplemental dietary yeast product had no effect on ruminal pH; however, the ratio of acetate to propionate decreased, and propionate percentage tended to increase, as supplementation of the yeast product increased. Addition of yeast product to the TMR had no adverse effect on milk flavor. Milk from cows fed yeast product had better flavor than milk from control cows. Results indicate that inclusion of this yeast product at 40% depressed feed intake.

Utilization of copper in copper proteinate, copper lysine, and cupric sulfate using the rat as an experimental model.

One hundred twenty male Sprague-Dawley rats, averaging 108.6 g initial body weight, were used in two feeding experiments to evaluate the utilization of Cu in Cu proteinate, Cu lysine, and cupric sulfate. In Exp. 1, 60 rats were randomly assigned to 12 treatments in a 2 x 2 x 3 factorial arrangement of treatments, with Zn supplementation at 0 or 1000 mg/kg diet, Cu supplementation at 5 or 15 mg/kg diet, and Cu form of CuSO4.5H2O, Cu proteinate, or Cu lysine. The purified basal diet contained .81 mg Cu, 20 mg Zn, and 60 mg Fe/kg diet. Experiment 2 was similar to Exp. 1 except Zn was replaced by Fe. In Exp. 1, feed intake of Cu proteinate (15.74 g/d) and Cu lysine (15.74 g/d) treatments was higher (P < .05) than that of CuSO4 (15.33 g/d). Body weight gain and feed intake were increased by high dietary Cu at either requirement or high levels of dietary Zn (P < .05). There were no differences in feed intake or body weight gain among the treatment groups in Exp. 2 (P > .05). The Cu utilization of Cu proteinate and Cu lysine were higher (P < .05) based on the liver Cu content. The rats fed Cu complexes had a higher liver Fe or Zn content (P < .05) than the rats fed CuSO4, suggesting that Cu complexes are absorbed via another mechanism that differs from that of inorganic Cu and does not interfere with Zn and Fe. Spleen Cu content may be a sensitive indicator of Cu status. High dietary Zn decreased Cu utilization, but this effect was overcome by high dietary Cu.

Responses of dairy cows supplemented with somatotropin during weeks 5 through 43 of lactation.

Beginning at wk 5 of lactation, 136 cows (34 per treatment) were supplemented daily for 38 wk with 0, 10.3, 20.6, or 41.2 mg of recombinantly derived bST monomer. Cows were obtained from University of Kentucky, University of Minnesota, University of Pennsylvania, and The Ohio State University. Nine cows (4 at 0 mg/d, 1 at 10.3 mg/d, 1 at 20.6 mg/d, and 3 at 41.2 mg/d) did not complete the experiment because of health problems. Data from these cows were included in the reproduction and health databases but not in the production database. Cows supplemented with bST produced more milk, consumed more feed, had lower rates of BW gain, and had improved efficiencies of milk production (conversion of feed and NEL to milk). Additional increases in productivity were modest at 20.6 and 41.2 mg/d versus productivity at 10.3 mg/d of bST. Concentrations of fat, protein, and TS in milk were unaffected. At 10.3 mg/d, bST did not adversely affect reproduction or health.

Short-term effects of dietary cation:anion balance on bone mineral homeostasis in the bovine.

Fifteen Friesian oxen between 12 and 18 months of age with a mean body mass of 240.7 kg, were randomly assigned to diets containing 0.25% phosphorus (P) or less, to evaluate the acute effects of a dietary cation:anion balance (DCAB) of either -11.1, +16.5 or +25.6 mmol 100 g-1 diet dry matter calculated as (Na+K) - (Cl+S), on blood, bone and faecal P, calcium (Ca) and magnesium (Mg) for a period of 9 weeks. Bone and faecal P concentrations were significantly (P < 0.05) higher in the anionic treatment group compared with the cationic and control treatment groups. The same was true for blood P, but significant (P < 0.05) only when compared with the cationic treatment group. Bone Ca was lower (NS) and blood Ca was significantly (P < 0.05) higher in the cationic compared to the anionic and control treatment groups, but faecal Ca was significantly (P < 0.05) higher in the anionic compared to the cationic, and control treatments groups. There was little difference in blood and bone Mg content among treatment groups, but faecal Mg was significantly (P < 0.05) higher in the anionic treatment group compared to the other 2 treatment groups. Whether this was due to the anionic nature of the diet or dietary concentration of Mg is unclear. Results from this research indicate a P sparing effect in which a low DCAB may improve the availability of P in animals where dietary P is limiting. In critical evaluations, weekly sampling of rib bone should be used to give a more accurate assessment of acute changes in bone mineral.

Calcium and cation-anion balance effects on feed intake, body weight gain, and humoral response of dairy calves.

Our objective was to examine whether feeding low cation-anion diets altered the Ca status of the growing calf. Holstein calves (n = 32; 16 males) were blocked at 56 to 70 d after birth according to sex and birth date and assigned randomly to dietary treatments containing Ca content and cation-anion balances as milliequivalents of (Na+K)-(Cl+S)/100 g of dietary DM of .42% and -18, .52% and -18, .42% and 13, and .52% and 13. Feed intake did not differ among treatments. Calves fed the diet with cation-anion balance of 13 had higher gain (.85 vs. .71 kg/d) than those fed the diet with balance of -18. Venous blood pH (7.374 vs. 7.323), partial pressure of CO2 (47.9 vs. 45.6 mm Hg), and bicarbonate (28.3 vs. 23.3 mmol/L) were higher for calves fed the 13 versus -18 balances. Plasma Ca and P were unaffected by Ca or cation-anion balance. Urinary pH was higher for calves fed the high than the low balance (7.442 vs. 6.047). Urinary Cl and Ca excretion was higher for calves fed the low than the high balance. Breaking strengths for 7th and 9th ribs were higher for calves fed the high balance and higher for the 7th rib only for calves fed the high Ca diet. Cation-anion balance altered Ca metabolism, but it is unclear whether Ca requirements were also altered.

Determination of calcium, phosphorus, and magnesium values in rib bones from clinically normal cattle.

Mean phosphorus (P) content in bovine rib bone was 102.9, 108.3, and 182.7 mg/g of bone on fresh, dry, and ash weight bases, respectively. Values for calcium (Ca) were 194.3, 203.7, and 344.6 mg/g, respectively, and for magnesium (Mg) were 5.3, 5.5, and 9.4 mg/g, respectively. Mean percentage of ash in rib bone was 59.12%. Expected concentrations of Ca, P, and Mg were determined on fresh, dry, and ash weight bases and for 3 age groups, 3 breeds, and bulls, females, and steers. On an ash weight basis, cattle 6 to 18 months old had 185.74 mg of P/g, 372.52 mg of Ca/g, and 12.37 mg of Mg/g. Those 19 to 36 months old had 182.02 mg of P/g, 322.35 mg of P/g, and 8.09 mg of Mg/g. Those > 36 months old had 174.80 mg of P/g, 340.36 mg of Ca/g, and 6.62 mg of Mg/g. Steers had 183.93 mg of P/g, 352.73 mg of Ca/g, and 10.15 mg of Mg/g. Females had 178.47 mg of P/g, 320.28 mg of Ca/g, and 6.5 mg of Mg/g. Males had 176.15 mg of P/g, all on an ash weight basis. Dairy breeds were found to have 186.08 mg of P/g, 351.25 mg of Ca/g, and 10.47 mg of Mg/g. Cattle of mixed breeding had 177.42 mg of P/g, 341.28 mg of Ca/g, and 6.54 mg of Mg/g. The Africander breed of beef cattle had 167.07 mg of P/g, all on an ash weight basis.

Copper status and requirement during the dry period and early lactation in multiparous Holstein cows.

Eighteen multiparous Holstein cows were assigned randomly to three treatments at the beginning of the dry period (8 wk before expected parturition). Treatments were: 1) the basal diet containing 5.5 ppm of Cu (control), 2) the basal diet supplemented with 10 ppm of Cu, and 3) the basal diet supplemented with 20 ppm of Cu. The objectives were to measure the changes of Cu and other trace mineral element concentrations in blood and liver from the onset of the dry period (approximately 8 wk prepartum) to 8 wk postpartum and to assess the requirement of Cu during this time. Liver Cu concentration in the control group declined continuously during the 8-wk dry period, and the nadir occurred at parturition. This decline was prevented by dietary Cu supplementation of 10 or 20 ppm. Liver Cu concentration in the control group started to increase slowly after the dramatic decline. Liver Zn concentration changed cubically as a function of week during the treatment period. Plasma Cu and Zn exhibited a quadratic pattern as a function of week. The plasma Cu concentration was lowest 5 wk prior to parturition.

Use of bovine rib bone in serial sampling for mineral analysis.

A total of 2160 samples of rib bone were used in a split-plot design analysis of variance to show that, on an ash weight basis, P content is not different among the right and left 9th, 10th, 11th, and 12th ribs of cattle above 6 mo of age. Results were similar for Ca on a fresh or dry weight basis. Some differences existed in Mg content among some of the ribs. Location on the rib from which samples were taken was responsible for significant differences in mineral concentrations. Based on results reported herein, ribs 9, 10, 11, and 12 of the right and left side may be used in the serial sampling of bone tissue in the bovine for the purpose of comparing the content of P, Ca, and--to some extent--Mg. Serial sampling makes possible comparison of bovine mineral status based on bone tissue over an extended experimental period that includes eight sampling dates.

Effect of copper status on luteinizing hormone secretion in dairy steers.

Two experiments were conducted to examine the effects of Cu status on neuroendocrine regulation of LH secretion in dairy steers. In Experiment 1, 18 Holstein steers were assigned randomly to treatment groups in a completely randomized design. Treatments consisted of basal diet alone (control) or supplemented with 5 ppm of Mo or with 20 ppm of Cu. At 8 and 16 wk, Cu concentrations in liver were higher in the group receiving Cu and lower in the group receiving Mo than in the control. Pulse frequencies of LH were not affected by any treatment. Serum LH concentration at 16 wk tended to be lower in the group receiving Mo than in either the control or the group receiving Cu. The ability of the pituitary gland to release LH in response to GnRH was not affected at 17 wk. Concentrations of LH in the pituitary glands were lower in the group receiving Mo than in that receiving Cu or in the controls. No differences in Cu or Mo concentrations were observed in pituitary, median eminence, or hypothalamic tissues. In Experiment 2, 12 Holstein steers were assigned to treatment groups receiving the basal diet supplemented with either 20 ppm or Cu or with 10 ppm of Mo. Spontaneous and GnRH-induced secretion of LH were not influenced by treatments after 8 mo of experiment. Reduction in Cu status has little effect on the endogenous secretion of LH in dairy steers.

Effects of high iron and sulfate ion concentrations on dry matter digestion and volatile fatty acid production by ruminal microorganisms.

The inhibitory effects of iron- and sulfate-containing compounds on the in vitro digestion of a balanced forage diet by mixed populations of ruminal microorganisms were examined in batch cultures. Compounds containing ferrous and ferric cations consistently inhibited DM digestion by up to 36% when added Fe concentrations in cultures were between 100 and 1,000 mg/L. Increased sulfate concentrations of up to 200 mg/L or chloride concentrations of up to 635 mg/L were not associated with decreased DM digestion. Ammonium sulfate additions that provided 200 mg/L of added sulfur increased (P less than .05) digestibility by 10%. Sulfate-containing iron salts tended to be less inhibitory than chloride salts and were associated with increased gas production during digestion. Ferric chloride inhibited (P less than .05) microbial activities at lower concentrations than ferrous chloride. Data suggest that excessive iron supplementation or contamination of feeds with iron-containing pollutants may decrease microbial activities in the rumen.

Effects of copper status on neutrophil function, superoxide dismutase, and copper distribution in steers.

Twelve Holstein steers in a completely randomized block design were fed either a basal diet (concentrate:silage or hay at a DM ratio of 35:65) plus Cu sulfate at 20 ppm of Cu (Cu-supplemented diet) or a basal diet plus ammonium molybdate to obtain 10 ppm of Mo (Cu-depleting diet) on a DM basis in the whole diet for 8 mo. Supplemental Mo was utilized in the Cu-depleting diet to develop a Cu-deficient group. Molybdenum slowly accumulated in the liver in the group fed the Cu-depleting diet. Copper concentrations in the liver and polymorphonuclear neutrophils decreased in the Cu-deficient group compared with the Cu-sufficient group. Plasma Cu concentration did not change during the trial for the Cu-sufficient group. In the Cu-deficient group, plasma Cu concentrations increased during the first 3 mo of the trial, then declined, and remained unchanged for the last 5 mo. Superoxide dismutase activities in red blood cells, polymorphonuclear neutrophils, and whole blood decreased in the Cu-deficient group. Phagocytic capacity was not affected by Cu status, but killing capacity was decreased by low Cu status in the Cu-deficient group by the end of the trial. Glutathione peroxidase activity was unaffected by Cu status. Clinical symptoms of Cu-deficiency were not observed in this trial; there was no evidence of blood hemoglobin or BW gain difference between the two groups. In this study, Cu status affected its distribution in the tissues and related enzyme activities as well as bactericidal function of neutrophils.

Effects of copper sources and dietary cation-anion balance on copper availability and acid-base status in dairy calves.

Twenty-four Holstein and Jersey calves (14 Holstein), 4 to 11 d of age, were assigned randomly to six treatments in a 2 x 3 factorial arrangement to examine the effects of Cu sources and dietary cation-anion balance on Cu availability and acid-base balance. Treatments were cationic basal diet (20 meq of dietary cation-anion balance on a DM basis), cationic basal diet supplemented with CuO, cationic basal diet supplemented with CuSO4, anionic basal diet (-10 meq), anionic basal diet supplemented with CuO, and anionic basal diet supplemented with CuSO4. Copper sources did not show any effect on growth of calves. The cationic diet increased calf growth compared with the anionic diet at wk 12 of the experiment. Blood pH was increased by the cationic diet in comparison with the anionic diet at wk 8 and 12. Blood pH also was increased by CuSO4 compared with CuO treatment in the early period of the treatment. Blood bicarbonate concentration was decreased by CuO and the anionic diet. Interactions between Cu sources and cation-anion balance were found for blood pH and bicarbonate concentration. Liver Cu concentration was increased by CuSO4 but not by CuO supplementation compared with control. Therefore, CuSO4 was found to be highly available, whereas CuO was a very poorly available source of Cu for young calves.

Role of magnesium in the dietary cation-anion balance equation for ruminants.

Eight midlactation Holstein cows (four primiparous) were assigned to replicated 4 x 4 Latin squares with a 2 x 2 factorial arrangement of treatments. The basal diet was formulated to contain 0 milliequivalents (Na + K) - Cl/100 g of diet DM. Treatment diets of high and low dietary cation-anion balance were achieved by adding appropriate amounts of supplemental Na + K (added on an equivalent basis) or Mg to the basal diet. Milk and protein yield were increased as well as DMI and FCM for Na + K diets The high concentration of cation increased milk fat percentage. The cation-anion balance (using Mg as a cation) had no effect on any of the production parameters observed. The higher cation-anion balances increased blood bicarbonate levels and plasma Na. Urinary Ca excretion was increased for the Mg diets. Urinary pH increased with both the source of cation (Na + K) and the concentration of cation (high) in the diet. other minerals were unaffected in milk, plasma, or urine. Responses measured in this trial reflect treatments calculated using the equation milliequivalents (Na + K) - Cl/100 g diet DM or (Na + K) - (Cl + S)/100 g diet DM, suggesting that Mg plays a minor role in dietary cation-anion balance.

Role of sulfur and chloride in the dietary cation-anion balance equation for lactating dairy cattle.

Ten Holstein cows averaging 120 d in lactation were arranged in replicated 5 x 5 Latin squares with 3-wk periods to evaluate the role of sulfur (S) in the dietary cation-anion balance equation. Diets were based on corn silage in Exp. 1 and sorghum silage in Exp. 2. Supplemental S and chloride (Cl) from the double sulfate of potassium and magnesium and CaCl2 were used to manipulate dietary cation-anion balance from 0 to +30 meq when expressed as meq [(Na + K)-(Cl + S)]/100 g diet DM and from +19 to +49 meq when expressed as meq [(Na + K)-Cl]/100 g diet DM. Blood pH was not affected by cation-anion balance, although both S and Cl supplementation tended to lower pH. Blood HCO3- and urine pH decreased and plasma calcium (Ca) and urinary Ca excretion increased as anion was added to the diet. Milk fat production tended to be increased by the low S supplementation. Dietary Cl and S had similar effects on acid-base status. Therefore, we suggest that S be included with Cl in the dietary cation-anion balance equation for lactating dairy cows as follows: meq [(Na + K)-(Cl + S)]/100 g diet DM. Although response of acid-base status to S and Cl was similar, as more data comparing the acidogenicity of S vs Cl become available, it may be necessary to include a modifying coefficient for S in the equation to adjust for differences between S and Cl in acid-generating potential. This coefficient may be further dependent on the dietary source of S.

Interactions of dietary cation-anion balance and phosphorus: effects on blood, bone and faecal phosphorus concentration in dairy calves.

Dietary levels of cations and anions are shown to have an effect on concentrations of phosphorus (P) in blood, bone and faeces of dairy calves between 9 and 19 weeks of age. Calves fed diets high in anions, demonstrated higher concentrations of P in blood and faeces than calves whose diets were high in cations, and at the same time demonstrated lower concentrations of P in bone. Compared to diets with high cation levels, diets high in anions produced significantly (p less than 0.05) higher concentrations of total P in the faeces at different stages in the experiment, higher serum inorganic phosphorus (SiP) concentrations and lower P concentrations in the bone, which were significant at the end of the trial (P less than 0.06). When the diet was low in P (0.22%), the cation-anion balance of the diet seemed to have the greatest effect, so that the interaction of dietary P and dietary cation-anion balance (DCAB) was responsible for changes in blood, bone and faeces.

Physiological responses in rats fed extracts of endophyte-free and endophyte-infected tall fescue seed relative to some known ergot alkaloids.

Ethanol and ethanol-water extracts of endophyte-infected tall fescue seed were effective for extracting toxin(s) responsible for feed intake and average daily weight gain (ADG) depression in Sprague Dawley rats. Although the ethanol extract of endophyte-infected seed depressed serum prolactin (Prl) concentrations, the data were less reflective of overall toxicity than feed intake and weight gain. Inclusion of commercially available ergonovine maleate, ergocryptine and ergotamine tartrate had no effect on rat feed intake, ADG or serum Prl at the levels tested. Dietary addition of a recombination of hexane, ethanol and ethanol-water extracts caused a toxicity response (depressed feed intake, ADG, and serum Prl) equivalent to that of the whole seed. The toxic factor(s) were extracted primarily in more polar solvents such as ethanol and ethanol-water. Rat assays can be used successfully in lieu of cattle assays as a routine evaluation of toxic components in endophyte-infected tall fescue. However, species differences dictate that eventually all suspected toxins be evaluated in the bovine.

Interactions of dietary cation-anion balance and phosphorus: effects on growth and serum inorganic phosphorus in dairy calves.

Thirty-six male and female Holstein and Jersey calves were assigned at weaning to a randomized complete block design in a 2 x 3 factorial arrangement to evaluate the influence of two dietary cation-anion balances (-14 and +39 meq(Na + K)-(Cl + S) per 100 g diet DM) and three amounts of dietary P (.22, .29, and .37%) on performance and P metabolism from 9 to 19 wk of age. Feed intake, average daily gain, and serum inorganic P were higher on the anionic diets and increased with increasing dietary P. Body weights were higher on the .37% P diets by wk 3 and on the anionic diets by wk 6. The interaction of dietary P and cation-anion balance was responsible for significant differences in calf performance; the anionic diet exhibited marked improvement over the cationic diet at the lowest P concentration. Results indicate that the availability of P for young dairy calves may be higher with anionic than cationic diets.

Reproductive responses in male rats fed extracts of fescue seed infected by the endophytic fungus Acremonium coenophialum.

This study was undertaken to determine whether a methanol extract of endophyte-infected tall fescue seed contained the factor(s) that were responsible for the decrease in male reproductive potential when rats were fed toxic tall fescue seed. Twenty-four Sprague-Dawley male rats (ca. 225 g.) were randomly allocated to one of three dietary treatments containing 50% (w/w) rodent chow and 50%: (1) noninfected tall fescue seed; (2) noninfected tall fescue seed treated with concentrated methanol effluent from serial methanol extraction of infected seed; and (3) the extracted seed residue of seed that was greater than 95% infected by Acremonium coenophialum. Parameters assessed were testicular weight, epidydimal weight, parenchymal weight, progressive sperm motility, sperm motility, sperm count and daily sperm production potential. Significant reduction (P less than 0.05) for feed intake, average daily gain, testicular weight, epidydimal weight and daily sperm production potential were observed for treatment 2. These data suggest that the serial methanol extract contains the factor(s) responsible for the lowered reproductive potential in male rats. The extract contained 15,578 micrograms/ml of pyrrolizidine alkaloids and only trace amounts of ergopeptides. These results suggest that N-formyl and N-acetyl loline may play an important role in the fescue toxicity noted in the exposed rats.