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A study was designed to evaluate estrus response and fertility after treatment with melengestrol acetate (MGA) and prostaglandin F2α (PGF2α) in yearling beef heifers. Three hundred four heifers at three locations were allotted to one of two treatments: Treatment 1 served as a nonsynchronized control (CON); and heifers in Treatment 2 received .5 mg of MGA animal-1•d-1 for 14 d and 25 mg of prostaglandin F2α(PGF2α) 17 d after MGA (MGA-PGF). Heifers in CON and MGA-PGF groups were artificially inseminated 12 h after observed estrus for 21 and 6 d after PGF2α, respectively. Blood samples were collected from each heifer 10 d before and on the day MGA feeding began and 10 d before and on the day PGF2αwas administered. Heifers with concentrations of serum progesterone > 1 ng/mL on either date before administration of MGA or PGF2αwere considered pubertal. More (P= .02) prepubertal heifers that received MGA attained puberty by initiation of breeding than did CON heifers (72 vs 45%, respectively). The proportion of heifers that displayed estrus within 6 d after PGF2αwas greater (P < .001) for MGA-PGF than for CON heifers (77 vs 25%, respectively) but was also influenced by location (P= .03). Conception rate at first service for MGA-PGF heifers that attained puberty during MGA feeding and before PGF2α was not different (P= .50) from that of CON that attained puberty during the same period.(ABSTRACT TRUNCATED AT 250 WORDS)

Eight Hereford-cross steers (470 kg), each with T cannulae in the duodenum and ileum, were used in four trials to measure effects of monensin and chlortetracycline on thiamin, niacin, riboflavin and biotin production and absorption. Steers were fed at 2-h intervals and Cr-EDTA and acid-insoluble ash were used as markers. Diets were fed in pelleted form. Effects of monensin were tested (trial 1) using a diet that contained 90% corn + 22 mg monensin/kg feed. Feed, duodenal and ileal quantities of thiamin in steers fed the basal diet were 12.6, 7.4 and .8 mg/d, respectively. Steers fed the monensin diet had thiamin quantities of 14.0, 9.3 and 1.7 mg/d for the three sites. Dietary niacin quantities did not differ among diets; however, duodenal, ileal and fecal quantities of niacin were lower in monensin-fed animals. Riboflavin and biotin quantities were not affected by monensin supplementation. Apparent ruminal organic matter digestibility was lower for steers fed monensin. In trial 2, chlortetracycline (7.8 mg/kg diet) did not affect quantities of duodenal or ileal thiamin. Chlortetracycline tended to reduce flow of niacin to the duodenum. Duodenal or ileal riboflavin was not affected by feeding chlortetracycline. In trial 3, chlortetracycline (70 mg·head−1·d−1) did not affect duodenal quantities of thiamin, but increased ileal (P<.01) and fecal (P<.10) quantities of thiamin. Chlortetracycline did not affect quantities of duodenal or ileal niacin or riboflavin. Quantities of riboflavin were greater in feces of control steers than in steers fed chlortetracycline. In trial 4, effects of feeding chlortetracycline (1 g/d) for 3 d were investigated during the post-antibiotic feeding period. Samples were collected on d 1 and 2, 5 and 6, and 9 and 10 following withdrawal of chlortetracycline feeding (samples from adjacent days were pooled). Chlortetracycline resulted in increased quantities (P<.005) of duodenal thiamin during d 1 and 2 (13.7 vs 6.7 mg/d). This effect decreased with time. Chlortetracycline tended (P<.25) to decrease duodenal, ileal and fecal riboflavin throughout the collection period. Niacin and biotin quantities at the various sites were not greatly affected by feeding chlortetracycline in this manner.

Hereford-cross steers, each fitted with T-type cannulae in the duodenum and ileum, were used in two trials to determine effects of grain type and concentrate-to-forage ratio on apparent thiamin, niacin, riboflavin and biotin production and absorption. Steers were fed at 2-h intervals and Cr-EDTA and acid insoluble ash were used as markers. Diets were fed as complete pelleted mixtures. Seven steers were used in trial 1 to compare diets containing 15% alfalfa and 85% of either corn, wheat, oat, barley or sorghum. All diets, except the sorghum diet, resulted in a net loss of thiamin in the rumen of steers. Apparent ruminal N and organic matter digestibilities of the sorghum diet were less (P<.05) than those of other diets. Apparent intestinal absorption of thiamin averaged 62.5%. Apparent niacin production in the rumen was substantial (37 to 359% greater than amounts fed) in all steers, as was absorption from the small intestine, which averaged 66.7%. More riboflavin flowed from the rumen than was consumed, indicating ruminal synthesis. Apparent intestinal absorption averaged 22.9% and did not differ significantly among diets. The major site of biotin synthesis appeared to be in the small intestine. In trial 2, the low-concentrate (LC) diet contained 29.5% corn, while the high-concentrate (HC) diet was comprised of 88.9% corn. The LC diet contained more niacin, riboflavin, biotin and crude protein, while the HC diet contained a greater quantity of thiamin. Duodenal concentrations of thiamin, niacin and riboflavin did not differ significantly between diets. The HC diet resulted in increased niacin (P<.01) and riboflavin (P<.05) quantities in feces.

Performance data on nearly 16,000 head of cattle that were used in trials to document effects of monensin on feedlot cattle were summarized. Cattle fed monensin-containing diets gained 1.6% faster, consumed 6.4% less feed and required 7.5% less feed/100 kg gain than cattle fed control diets. Monensin resulted in the greatest improvement in feed/ gain at 2.9 Meal metabolizable energy (ME)/kg diet dry matter (DM). Within the range of monensin concentrations used in the trials that were summarized (31.8 ± 7.5 mg/kg DM), high monensin concentrations did not improve feed/gain over that obtained with lower concentrations. Carcass characteristics were not significantly influenced by monensin. Responses of cattle to monensin and implants were additive. Energy metabolism data suggested that monensin improved digestibility of DM, reduced fasting heat production and increased dietary net energy maintenance (NEm) values more than it increased net energy gain (NEg) values. Data showing the response of cattle to monensin when fed various dietary protein concentrations or sources of supplemental N suggested that monensin had a protein sparing effect. Monensin has also been shown to reduce lactic acid production, aid in the control of coccidia and bloat and to be toxic to face and horn fly larva in feces of monensin-fed cattle. In pasture trials, monensin improved daily gains. When fed to beef cows, monensin reduced amounts of feed required to maintain cow weight.

Body compositions of 40 Angus, 20 Angus-Hereford and 20 Angus-Holstein spring-calving cows were determined by deuterium dilution at the initiation and at the end of the winter feeding period. For the winter feeding period, cows were allotted within breed to metabolizable energy (ME) levels of 12.9 or 18.0 Mcal/ head daily. Weight (W), length, height, heart girth and condition score were measured on each cow before body composition determinations. Regressions were conducted within breed-body composition determination time groups to evaluate linear measurements and condition score as predictors of percentage empty body fat (PEBF) of beef cows. Regressions for Angus and Angus-Hereford cows were similar, but regressions for Angus-Holstein cows differed from those for Angus or Angus-Hereford cows. The best simple regression for the Angus-Holstein cows accounted for only 3% of the variation in PEBF. For the Angus and Angus-Hereford cows, condition score was the best estimator of PEBF (r = .66,P<.01). Weight: height ratio was correlated .58 (P<.01) with PEBF; however, weight alone was correlated .54 with PEBF. Regressions with W2.0, W•75and W did not improve R2values over those obtained with W1.0. Log and square root transformations of linear measurements did not improve ability to estimate PEBF. Multiple regressions did not significantly improve R2 values over that of the simple regression of PEBF on condition score. Results of this study suggest that linear measurements are not superior to visual appraisal as estimators of body composition of beef cows.

The function of end products of silage fermentation, added initially at levels commonly present in fermented forage, in directing or limiting fermentative activity was evaluated using Plexiglas laboratory silos. Additions, on a dry matter basis, included .7% ethanol, .9% acetic acid and 4.7% lactic acid to chopped corn plant material, singly and in all combinations in a 23factorial arrangement of treatments using 24 laboratory silos with three silos/treatment. Lactic acid added singly stimulated nonlactic acid fermentation. It increased gas production, wet matter loss, energy loss and ethanol levels to values that were 1.6-, 1.3-, and 2.2-fold those found in untreated silage. Lactic acid caused a 41% reduction in acetic acid production. Final lactic acid levels were elevated slightly and pH was reduced. Acetic acid alone inhibited fermentation, since it decreased production of lactic acid and ethanol by 18 and 30% and reduced wet matter and energy losses by 18 and 67%. Ethanol added independently increased lactic acid production 25%, reduced energy loss 52%, but did not alter acetic acid or ethanol production since the resulting silage ethanol levels were elevated to the extent of the initial addition. Responses to combinations did not parallel independent additions. The combination of acetic and lactic acids essentially eliminated their production, since final levels were about equal to the amounts added and reduced gas production to 35% of that from control silos. In this treatment acetic acid negated in part the stimulatory effect of lactic acid on ethanol production, reduced wet matter loss as occurred with acetic alone and resulted in an energy loss that was similar to that for control silos. Other combinations appeared to result in unfavorable responses. Lactic acid added with ethanol reduced production of lactic and acetic acids, increased energy losses and elevated both gas and ethanol productions. While acetic acid or ethanol added independently reduced energy losses, when used in combination energy loss was similar to controls. The combination of lactic and acetic acids with ethanol reduced production of gas, but energy losses were about twice those for control silos. Regulation of fermentation via acetic acid, ethanol and lactic acid was only indirectly related to pH suggesting selective microbial action of these end products on fermentation processes.

Four growth trials were conducted to determine whether lambs have the ability to recognize a dietary Ca deficiency and to correct that deficiency by consuming minerals offered free choice. In trial 1, lambs were fed a control or Ca-deficient diet with 0, 1, 5 or 10 mineral choices, only one of which provided Ca. Daily gains and feed efficiencies of lambs fed control diets tended to be superior to those of lambs fed Ca-deficient diets. Consumption of free choice calcium carbonate was greater (P<.05) for lambs fed Ca-deficient diets than for those fed control diets. However, total Ca intake was greatest (P<.05) for lambs fed control diets. In trial 2, lambs were fed diets containing .35, .20 or .06% Ca with zero or four mineral choices in either a constant or varied location. Daily gains were highest (P<.05) for lambs fed the control diet. Performance of lambs fed diets deficient in Ca was not improved by providing free choice minerals. Although free choice Ca intakes were higher (P<.05) for lambs fed Ca-deficient diets, total intake of Ca decreased with severity of dietary Ca deficiency. In trial 3, lambs were fed a (1) Ca-adequate diet, (2) Ca-deficient diet, (3) Ca-deficient diet with four mineral choices (one of which contained Ca) or (4) Ca-deficient diet with seven times the daily Ca requirement offered once weekly. Lambs fed control diets gained faster (P<.05) than those fed deficient diets with free choice minerals. Ca intakes were greater (P<.05) for control lambs than for those fed Ca-deficient diets with Ca available free choice. In trial 4, lambs were fed either a control or a Ca-deficient diet for 42 d. All lambs were then offered both control and Ca-deficient diets in separate compartments of the feed bunks. Although performance, bone and serum data followed trends similar to those observed in trials 1, 2 and 3, differences between treatment groups were not significant. Data from these trials support die recommendation that, when possible, required minerals should be provided in the diet rather than on a free choice basis.

Mineral content of hair is affected by season, breed, hair color within and between breeds, sire, age and body location. Seasonal effects may be due to stage of growth of hair and to changes caused by perspiration, surface contamination and diet. Breed and sire effects on mineral content of hair complicate prediction of nutritional status based on hair analyses because, in many commercial cattle, neither breed nor sire is known. Hair from young animals may be lower in Zn, Mn and Fe, but is higher in Na, Ca, Cu and K than that from older animals. Pigmented hair apparently is higher in Ca, Mg, K and Na than white hair, but trace mineral concentrations are similar in hair of different colors. The effect of body location on mineral content of hair may be due to differences in surface contamination, differences in hair growth cycles and differences in texture of the hair. Concentrations of Ca, P and Cu in hair are not affected by dietary intake of these minerals. Zn and Se contents of hair may reflect dietary intake. Information on other required minerals is lacking. Pb, As and, possibly, Cd levels in hair may be related to dietary or environmental exposure. Because of the many factors that cause variation in mineral content of hair, hair analyses are not likely to be precise indicators of the mineral status of animals. Hair analyses may help to detect severe deficiencies of some required minerals or exposure to some heavy metals. However, if hair analyses are to be conducted, care must be taken to compare values from test animals with those from animals of similar breed, sex, season, sire and color. In addition, new hair growth should be analyzed, environmental contamination should be minimized and the hair samples should be cleaned before analyses.

Four trials were conducted to examine the effects of Captan (N-trichloromethylthiotetra-hydrophthalimide) on digestibility of forage. In the first trial, alfalfa-brome hay was digested in vitrowith Captan added to the hay at levels ranging from 0 to 150 ppm. Digestibilities of alfalfa-brome dry matter, cell walls, acid detergent fiber, cellulose and hemicellulose exhibited a curvilinear response to Captan level. Maximum responses occurred at 75 to 100 ppm of added Captan. In the second trial, addition of 75 ppm of Captan to alfalfa-brome hay resulted in a significant increase in in vitrodry matter digestibility when fresh rumen fluid was used as the inoculum, but had no effect when distilled water or autoclaved rumen fluid was used as the inoculum. The influence of Captan on rate of in vitrodigestion was also examined. Addition of 75 ppm of Captan to alfalfa-brome hay resulted in an apparent increase (19.5%) in rate of cell wall digestion. Five Angus steers were used in an experiment with a 5 X 5 Latin-square design conducted to examine the effects of Captan on in vivodigestibility. Captan was added at 0, 75, 150, 300 and 600 ppm of air dry diet. Steers fed Captan gained faster (P<.05) and had higher (P<.05) gains per unit of feed. Digestibilities of dry matter, cell walls, acid detergent fiber, cellulose, hemicellulose and protein were higher (P<.01) for steers fed Captan than for those fed the control diet. There were no significant responses in gain or digestibilities as Captan level increased from 75 to 600 ppm.

The fermentation of microbially-treated corn silage was evaluated in laboratory silos that were designed to simulate the internal conditions of field-scale silos. Duplicate silos of control and two levels (4.5 × 107and 22.5 × 107live organisms per kilogram wet silage) of Lactobacillus bulgaricus, Lactobacillus acidophilus, Lactobacillus brevis, Streptococcus lactisand Streptococcus cremoriswere included. Aspergillus oryzaewas added at two levels, although numbers of organisms were not counted. Dry matter (DM) and crude protein contents of the silage averaged 32.0% and 3.0% (9.4% on DM basis), respectively. Recoveries of DM and crude protein were not affected by inoculation. Nonprotein nitrogen levels tended to be increased by the higher levels of added organisms. However, values for treated silages did not differ significantly from those for controls. All microbial treatments tended to increase NH3-N levels, with L. bulgaricus, S. lactisand S. cremorisresulting in higher (P<.05) NH3-N levels (7.4 to 7.6% of total N) than controls (5.9% of total N). Lactic acid, acetic acid and ethanol concentrations were not affected by microbial treatment. It appeared that time required to complete 95% of total gas production was decreased by A. oryzae, L. acidophilusand S. lactis. Cell wall constituents, acid detergent fiber and pH were not significantly affected by level or type of organism. A commercial live bacterial silage additive that contained Bacillus subtilis, Lactobacillus acidophilus, Aspergillus oryzaeand mixed lactic ferment enzymes did not improve the feedlot performance of steers or digestibility in lambs fed corn silage. Results from these trials show that the added organisms increased protein degradation and did not result in higher quality corn silage.

Mineral-adequate (control), calcium-deficient and sulfur-deficient diets were fed to lambs to determine if they would consume appropriate minerals in adequate amounts when several free choice minerals were offered. Half of the lambs fed each diet received 10 minerals in individual containers. The minerals were CaCO3, K2CO3, Na2CO3, ZnCO3, 4MgCO3-Mg(OH)2-4H20, CuCO3MnCO3, NaH2P04, Na2SO4and NaCl. Daily gains, feed intakes and feed efficiencies were not improved by feeding free choice minerals. Plasma mineral levels, bone measurements and mineral contents and wool growth indicated mineral deficiencies, and in no instance did the feeding of free choice minerals improve lamb performance significantly over lambs not offered free choice minerals.Mineral consumption data indicated that calcium-deficient lambs selected CaCO3, though not in significantly greater quantities than lambs fed the control or sulfur-deficient diets. However, this calcium consumption did not improve growth parameters or physiological measurements. Sulfur-deficient lambs showed little ability to choose sulfur as Na2SO4. Throughout the trial, control lambs consumed more mineral (562.6 g) than calcium-deficient or sulfur-deficient lambs (419.6 and 465.8 g, respectively). The minerals that were consumed were primarily those containing sodium, especially NaCl.Mineral consumption and growth data showed that lambs which were deficient in calcium or sulfur did not consume adequate amounts of free choice minerals to meet their requirements. The lambs apparently consumed acceptable minerals, rather than needed minerals. Because the lambs did not consume sufficient amounts of needed minerals to meet their requirements, and because they tended to over consume acceptable minerals, it is economically and nutritonally advisable to feed a complete ration or when it is not possible to feed a complete ration to offer on a free choice basis a palatable, complete mineral mixture.

Alfalfa was ensiled without chemical treatment (control) and with 1.25, 1.75 or 2.25% formic acid; .50, .75 or 1.00% formaldehyde and 1.00 or 1.50% propionic acid to measure the influence of these chemicals on silage fermentation and the digestibility of the resulting haylages by sheep. Treatment percentages are amounts of pure chemical expressed as a percent of forage dry matter. Treatment with formaldehyde reduced nonprotein nitrogen, ammoniacal nitrogen and soluble nitrogen levels in the haylage. When 1.00% formaldehyde was added these nitrogen values are similar to those in an unensiled control sample. Formaldehyde protected hemicellulose from degradation, reduced lactic and acetic acid contents and crude protein digestibility, tended to improve nitrogen retention and reduced ruminal butyrate. Formic acid reduced nonprotein nitrogen, ammoniacal nitrogen and soluble nitrogen levels, but less effectively than formaldehyde. Lactic acid contents were reduced by formic acid, but it improved the digestibility of energy and crude fiber and nitrogen retention. Ruminal butyrate was lowered in lambs fed haylage treated with 2.25% formic acid. Propionic acid reduced ammoniacal nitrogen, nonprotein nitrogen and soluble nitrogen levels in the haylage. It appeared to reduce cellulose and lactic acid contents. Lambs fed 1.50% propionic acid haylage appeared to retain more nitrogen than controls. Propionic acid treatment increased ruminal propionate and reduced ruminal butyrate levels.

Lambs fed semipurified diets supplemented with DL-methionine, hydroxy analog of methionine, calcium sulfate, sodium sulfate or elemental sulfur gained faster, consumed more dry matter, and digested and retained greater weights of nitrogen and sulfur (P<.01) than lambs fed a sulfur deficient diet. Lambs fed a sulfur deficient diet had severe weight losses in 40 days and were removed from the experiment. Lambs fed hydroxy analog of methionine had more (P<.05) wool growth than lambs fed elemental sulfur (33.2 vs27.1 mm). Apparent dry matter digestibilities ranged from 76.1 to 80.9% for the various treatments. When expressed as a percent of intake, apparent nitrogen digestibilities were not affected by sulfur treatments, however lambs fed sulfur from each of the supplemental sulfur sources retained higher percentages (P<.01) of the nitrogen consumed than control lambs. Sulfur supplementation also improved the utilization of digested nitrogen. With the exception of lambs fed elemental sulfur, those fed sulfur from each of the sulfur sources digested greater percentages (P<.01) of their dietary sulfur than lambs fed a diet with no added sulfur. However, the lambs fed elemental sulfur retained a higher (P<.01) percent of digested sulfur than those fed the other sulfur sources. Sulfur retentions of lambs supplemented with sulfur varied from 48.5 to 61.8% during the initial 20 days of feeding, but varied from 31.5 to 39.4% during the third 20-day period. The reduced variation among lambs fed the various sulfur sources and the decline in percentages of sulfur that were retained suggests that body saturation with sulfur may have occurred after the initial 20 days.

Two in vitrostudies were conducted to determine the availability of several sources of sulfur. A sulfur concentration of 21.5 µg/ml of inoculum was not adequate to meet the needs of rumen microbes in the in vitrosystem used, while concentrations of 86.7 and 130.0 µg/ml were apparently inhibitory. A sulfur concentration of 43.3 µg/ml in the incubation medium resulted in the greatest protein synthesis. Sulfur from L-methionine resulted in the greatest microbial protein synthesis, whereas sulfur from the common sources of supplemental sulfur, sodium sulfate and elemental sulfur, was only 55.4 and 35.8% as effective, respectively. Calcium sulfate and ammonium sulfate were the most effective inorganic sulfur sources. Sulfur from hydroxy analog of methionine was poorly utilized for microbial protein synthesis. Relative availabilities of sulfur from the various sulfur sources for in vitroprotein synthesis were: L-methionine, 100.0%; calcium sulfate, 94.1%; ammonium sulfate, 93.0%; DL-methionine, 63.0%; sodium sulfate, 55.4%; sodium sulfide, 42.6%; elemental sulfur, 35.8% and hydroxy analog of methionine, 28.8%.

Corn grain was ensiled in whole kernel or rolled forms, at harvest or after drying and reconsitution to moisture levels of 21.5, 27.5 and 33.1%. As moisture contents increased, energy losses increased and pH values decreased. Molar percentages of acetic, propionic and butyric acids in the ensiled corn grain averaged 5.2, .8 and 1.6%. Rolled corn and corn ensiled immediately following harvest at 33.1% moisture had the highest butyric acid concentrations. Lactic acid and ethanol concentrations were highest for corn ensiled at 27.5 or 33.1% moisture. Molar percentages of lactic acid were higher and molar percentages of ethanol were lower for corn ensiled at 27.5 or 33.1% moisture than for corn ensiled at 21.5% moisture. In this study energy losses were minimized by ensiling rolled corn grain at moisture contents of 21.5 or 27.5%.

Studies were conducted with two species of dried aquatic plants (Myriophyllum exalbescensand Potamogeton pectinatus) and an ensiled mixture of aquatic plants (approximately 50% Myriophyllum,30% Ceratophyllum,10% Potamogeton,5% Vallisneriaand 5% unknown) to determine the digestibility of aquatic plants by lambs. Dried Myriophyllum exalbescensand Potamogeton pectinatuswere unpalatable (less than 600 g dry matter consumed daily) to lambs. Mixing an equal proportion of dehydrated alfalfa to either of these two species resulted in dry matter and crude protein digestibilities, as determined by difference, of 43.8 and 46.0% for Myriophyllumand 43.4 and 44.1% for Potamogeton.Energy digestibility was higher for Myriophyllum(53.7%) than Potamogeton(47.4%).Lambs fed diets of ensiled aquatic plants, aquatic plants plus corn or aquatic plants plus alfalfa silage had dry matter digestibilities of 41.4, 32.0 and 38.5%, respectively. However, lambs fed ensiled diets of alfalfa or alfalfa plus corn had dry matter digestibilities of 61.9 and 66.2%, respectively.

Chemical analyses of 21 species of dried aquatic plants indicated that they contain sufficient quantities of nutrients to be considered as livestock feedstuffs. Although considerable variation existed among the 21 species, 14 species contained more than 10% protein and all species contained less than 30% crude fiber. Calcium and phosphorus contents averaged 1.62% and .27%, respectively. Neutral detergent and acid detergent fiber contents of the 21 species averaged 42.3% and 32.6%, respectively.Mixed aquatic plant species (approximately 50% Myriophyllus,30% Ceratophyllum,10% Potamogeton,5% Vallisneriaand 5% unknown) were ensiled with organic acids (acetic, formic, propionic), corn or alfalfa. After 47 days of fermentation the silages had pH values above 4.5 and lactic acid values below .4% of the dry matter. Alfalfa silage ensiled with the same treatments had pH values below 4.1 and lactic acid values above .6% of the dry matter. Ensiling mixtures of aquatic plants and alfalfa resulted in silages with similar characteristics as the aquatic plant silages. Addition of alfalfa to sterilized aquatic plants at ensiling resulted in a silage of similar composition as the alfalfa silages.

Objectives of this study were to determine the influence of trenbolone acetate (TBA) and estradiol (E2) in a combined implant on feedlot performance, carcass characteristics, and carcass composition in finishing steers. Sixty-four large-framed (394.1 kg) crossbred steers were randomly assigned to one of four pens. Subsequently, pens were randomly assigned to one of two treatments, implanted (120 mg of TBA and 24 mg of E2) and nonimplanted. Eight steers/treatment were slaughtered for initial carcass composition. Remaining steers were assigned to one of three serial slaughter dates (d 40, 115, or 143). Implantation increased circulating trenbolone (TBOH) and E2concentrations throughout the trial. Implantation increased ADG 18% (P< .001) during d 0 to 40, 21% (P< .001) from d 0 to 115, and 16% for the entire 143 d. Implant status had no effect (P> .05) on dry matter intake. Feed efficiency was improved 13% during d 0 to 40 (P< .01) and from d 41 to 115 (P= .07). Longissimus muscle area was larger (P< .05) in implanted steers than in nonimplanted steers on d 115. Carcasses from implanted steers had a smaller (P< .05) percentage of kidney, pelvic, and heart (KPH) fat on d 143 than those from nonimplanted steers. Carcasses from implanted steers possessed more carcass protein (P< .05) on d 40. Implanted steers had an 82% increase (P< .05) in daily carcass protein accretion during the first 40 d. Implantation increased (P< .01) carcass water but did not affect carcass fat accumulation throughout the feeding period. The combined TBA+E2implant improved feedlot performance and stimulated carcass protein accretion in feedlot steers.

Objectives of this study were to analyze alterations in circulating IGF-I and insulin-like growth factor binding protein (IGFBP) concentrations due to administration of a combined trenbolone acetate (TBA) and estradiol (E2) implant. This study was part of a larger serial slaughter study in which 64 large-framed (394.1 kg) crossbred steers were randomly assigned to one of four pens. Pens were assigned to one of two treatments: implanted (120 mg of TBA and 24 mg of E2) and nonimplanted. After d 2, 24 steers/treatment remained on the study. These steers were assigned to one of three serial slaughter dates (d 40, 115, and 143). Blood samples were obtained on d 0, 2, 21, 40, 115, and 143 from remaining steers. Serum was harvested and analyzed for IGF-I, IGFBP, and mitogenic activity. Glycyl-glycine (GG) extraction of serum was performed to reduce IGFBP interference in the IGF-I RIA. Implantation with TBA+E2 interference in the IGF-I RIA. Implantation with TBA+E2 increased (P< .001) circulating IGF-I concentrations during the period from d 0 to d 40. On d 21 and 40, steers implanted with TBA+E2had 16 and 22%, respectively, greater (P< .001) circulating IGF-I concentrations than nonimplanted steers. For steers in the study for at least 115 d, TBA+E2increased (P< .05) IGF-I concentrations 9, 13, and 19% on d 21, 40, and 115, respectively, compared with nonimplanted steers. Implantation with TBA+E2 resulted in greater (P< .05) serum concentration of a 49/39-kDa IGFBP (IGFBP-3) on d 21 and 40 after implantation. Sera from steers implanted with TBA+E2stimulated proliferation of cultured muscle satellite cells to a greater extent (P< .05) than did sera from nonimplanted steers on d 21, 40, 115, and 143 after implantation. In summary, TBA+E2increased serum concentrations of both IGF-I and IGFBP-3. Additionally, implantation increased mitogenic activity of sera from implanted as compared to nonimplanted steers. These alterations may be partially responsible for the positive effects of TBA+E2implants on feedlot performance and rate of protein accretion in steers.

Although originally used for prediction of whole body composition (WBC), use of 40K emission detection was later suggested for determination of empty body composition (EBC). Therefore, the present study was conducted to validate existing equations developed to predict WBC and to develop more useful equations to predict EBC or carcass composition (CC) of beef steers. Fourteen crossbred steers were detected for 40K emissions and slaughtered and their chemical composition determined from chemical analyses and total body K determined from 40K emissions. The existing equation for percentage whole body lipid had a slope of .93 and an intercept of −1.62%, indicating a close approximation to percentage of whole body lipid. Percentage of whole body protein was poorly estimated by existing equations. Equations developed for prediction of EBC relied on both BW and predicted K. Coefficients of variation for prediction of empty body water or protein were within 5% and those for prediction of empty body lipid were approximately 15%. These results demonstrate that use of predicted K from 40K emission detection enhances the determination of EBC and CC.

Seven Holstein steers (340 kg) fitted with ruminal, duodenal and ileal cannulae were used to measure the influence of supplemental N source on digestion of dietary crude protein (CP) and on ruminal rates of protein degradation. Diets used were corn-based (isonitrogenous, 12% CP on a dry matter basis, and isocaloric, 80% total digestible nutrients) with urea, soybean meal (SBM), linseed meal (LSM) or corn gluten meal (CGM) as supplemental N. Ruminal ammonia N concentrations were higher (P<.05) in steers fed LSM than in those fed CGM, but did not differ from those in steers fed urea or SBM (11.7, 6.7, 9.1 and 9.2 mg/100 ml, respectively). Due to the high degradability of urea, ruminal digestion of dietary CP was greater (P<.05) in steers fed urea than in those fed CGM, but intermediate in steers fed SBM and LSM (58.4, 48.8, 53.1 and 53.9%, respectively). Flow of bacterial nonammonia N to the duodenum was highest (P<.05) in steers fed SBM or LSM, intermediate (P<.05) for urea and lowest (P<.05) for CGM (86.8, 86.1, 76.3 and 65.9 g/d, respectively). Efficiency of bacterial protein synthesis was lowest in steers fed CGM and differed (P<.05) from SBM (15.6 vs 21.8 g N/kg organic matter truly digested, respectively). Rate of ruminal digestion for SBM-CP differed (P<.05) from that of CGM-CP but not from that of LSM-CP (17.70, 5.20 and 10.13%/h, respectively). The slow rate of ruminal degradability of CGM resulted in increased amounts of dietary protein reaching the intestinal tract but lower amounts of bacterial protein, thus intestinal protein supply was not appreciably altered.

While many laboratory procedures have been proposed for estimating feeding quality of perennial grass and legume forages, none have been adequately tested for their potential in predicting quality of corn and sorghum silages. The objective of this phase of a comprehensive study was to assess the value of six biological procedures proposed for predicting forage digestibility of silages of corn (Zea maysL.) and sorghum (Sorghum bicolor(L.) Moench, S. sudanense(Piper) Stapf, and their hybrid). In vivodigestible dry matter (DDM) of 51 corn and sorghum silages (17 in each of 3 years) was determined using sheep in conventional feeding trials. A modified Tilley and Terry (1963) in vitroprocedure (T‐T DDM), gave the highest correlations with in vivoDDM (r = 0.83 for corn silages and 0.91 for sorghum silages). A “direct acidification” in vitrorumen fermentation procedure resulted in in vitroDDM which was also highly correlated with in vivoDDM (r = 0.50 and 0.91 for corn and sorghum silages, respectively). Within the corn silages, the correlation between direct avidification DDM and in vivoDDM of 18 entries with high grain percentages was only 0.19, while that for seven entries with low grain percentages was 0.93. Apparently, the combination of large amounts of available carbohydrates in the high grain entries and the phosphate buffer led to erratic growth and digestive action by the rumen bacteria. A 6‐hour rumen fluid fermentation procedure gave DDM values which were 36 to 38% of the T‐T DDM values and were poorly correlated with in vivoDDM. A cellulase‐acid pepsin procedure gave DDM values for both corn and sorghum silages that were 56% of the T‐T DDM values; however, cellulase‐acid pepsin DDM was positively correlated with in vivoDDM of sorghum silages (r = 0.72) and negatively correlated with in vivoDDM of corn silages (r = −0.42). Two procedures that involved the neutral detergent extraction (Goering and Van Soest, 1970) and a 48‐hour rumen fluid fermentation gave in vitroDDM values which were highly correlated with in vivoDDM (r = 0.73 to 0.90). A multiple correlation analysis revealed that little improvement of the simple correlation between specific laboratory procedures and in vivoDDM was attained by combining procedures. We developed simple regression equations to predict in vivoDDM from T‐T DDM and direct acidification DDM for corn and sorghum silages.

Numerous chemical procedures have been suggested for predicting feeding quality of perennial forages but none have been adequately tested for their ability to predict quality of silages of corn (Zea maysL.) and sorghum [Sorghum bicolor(L.) Moench, S. sudanense(Piper) Stapf, and their hybrid]. The objective of this phase of a comprehensive study was to determine the value of 20 of these chemical procedures for predicting in vivodigestibility of corn and sorghum silages. We determined in vivodigestible dry matter (DDM) of 51 silages (17 in each of 3 years) in conventional sheep feeding trials. Acid detergent fiber (ADF) was the best chemical predictor of in vivoDDM for both corn and sorghum silages. ADF concentration accounted for 80% of the variation in digestibility of sorghum silages and 61% of the variation in digestibility of corn silages. More than half of the variation in digestibility of these silages was also accounted for by calculated cellulose and by crude fiber (CF) concentration. Permanganate lignin accounted for 74% of the variation in digestibility of sorghum silages but only 23% of the variation in corn silage digestibility. Inclusion of crude protein concentration did not improve the digestibility prediction potential of ADF, CF, or the other chemical methods. The Van Soest summative equation, acid detergent lignin (ADL), ADL/ADF, dry matter solubility in 1 NH2SO4, and solubility in acid pepsin all failed to provide satisfactory estimates of corn or sorghum silage digestibility. None of the chemical methods equaled our modified Tilley and Terry in vitroDDM as a predictor of in vivoDDM of corn or sorghum silages. However, ADF accounted for only 4% less of the variation in digestibility of sorghum silages and 9% less of the variation in digestibility of corn silages than did in vitroDDM. The relatively low cost of ADF analysis makes it a useful procedure for testing silages that are intended as feeds for ruminants. We present simple regression equations for prediction of in vivoDDM of corn and sorghum silages from their concentrations of several chemical entities.

Twenty Angus-Hereford and 20 Angus-Holstein cows were individually fed 12.9 or 18.0 Mcal metabolizable energy (ME)/head daily from November 28, 1979 through February 21, 1980. Energy retentions for the winter feeding period were calculated by determining body composition at the initiation and at the termination of the feeding period. After the experimental period, all cows were managed the same through weaning. Maintenance energy requirements (Kcal/d) estimated from linear regressions of energy retentions on ME intakes per unit body weight (BW).75were 127.6 and 140.3 kcal/BW.75for Angus-Hereford and Angus-Holstein cows, respectively. Estimates of maintenance energy requirements for thin and fat cows within each breed type indicated that fatter cows of Angus-Hereford breeding had 6.1% lower energy requirements than thinner cows. Opposite trends occurred with Angus-Holstein cows, where fat cows had 2.7% higher maintenance requirements. Estimated maintenance energy requirements were higher (P<.01) for protein than fat tissue. Maintenance energy requirements of fat was −1.55 kcal ME/kg for Angus-Hereford cows, indicating that for cows of the same lean body mass, cows with more fat have a lower daily energy requirement during winter. Angus-Holstein cows had an estimated maintenance energy requirement of fat of 51.11 kcal ME/kg. Because cattle of Holstein breeding have less subcutaneous fat than cattle of the beef breeds, and less subcutaneous fat would provide less insulation, the estimated maintenance requirements of fat in Angus-Holstein cows may be an estimate of the true maintenance requirement of fat. Estimates of the partial efficiency of ME use for tissue gain and the ME sparing effect of body tissue loss were 78.8% and .70, respectively, for Angus-Hereford cows and 53.8% and .46, respectively, for Angus-Holstein cows. Regression of retained energy on cow BW.75, body fat and body protein calculated for Angus-Hereford and Angus-Holstein cows from within energy level indicated that BW.75accounted for less variation in retained energy than weight of empty body fat or protein. Multiple regressions that contained all three variables accounted for 75% and 32% of the variation for Angus-Hereford and Angus-Holstein cows, respectively. Subsequent performance of the cow and calf was not affected by winter energy levels fed, body composition of cows before calving or body energy changes of cows during the winter.

Three experiments were conducted to determine whether concentrations of minerals in hair and other tissues of rats and goats are affected by level of dietary Zn or Cd. In the first experiment, rats were fed diets that contained 10.3, 20.5, 33.7, 41.3 or 52.9 µg Zn/g for 57 d. Rats fed the diet that contained 10.3 µg Zn/g suffered from mild Zn deficiency, as indicated by depressed feed intakes and slower growth rates than rats fed diets containing higher amounts of Zn. Zinc concentrations in hair (P<.01), liver (P<.01) and kidney (P<.01) increased as dietary Zn increased. Confidence intervals for dietary Zn concentration predicted from Zn analysis of hair were large. In the second experiment, rats were fed diets that contained .1, 4.0, 7.6, 10.1 or 15.9 µg Cd/g for 57 d. Total growth, feed intake, feed efficiency and liver, kidney and testes weights were not affected (P>.05) by dietary Cd concentration. Cadmium increased linearly in liver (P<.01) and kidney (P<.01) and quadraticly in testes (P<.01) as Cd intake increased, but Cd in hair was not affected by dietary level of Cd. High correlations between Cd concentrations in liver (R2= .88) and kidney (R2= .90) and dietary Cd concentration indicate that Cd intakes of rats may be accurately predicted from Cd analyses of these tissues. In the third experiment, goats were fed diets containing 0, 10.4, 18.0 or 28.5 µg Cd/g for 125 d. Growth, feed intake, feed efficiency and liver and kidney weights were not affected by dietary Cd intake. Cadmium in hair samples was not affected by level of dietary Cd; however, cadmium in liver (P<.01), kidney (P<.01) and proximal duodenum (P<.01) increased as dietary Cd increased. Cadmium in liver, kidney, lungs and proximal duodenum was highly correlated (R2= .67, .89, .57, .49, respectively) with dietary Cd concentration.

The use of W.75as an estimator of fasting heat production (HP) for male and female rats, chickens, rabbits, dogs, humans, cattle and for ewes was studied using data obtained from the literature. Regression coefficients for models which related HP to body weight (W) were calculated from data for each population of animals. Highly significant (P<.001) equations were obtained for animals in each species-sex subclass, thus nullifying the common assumption that the narrow W ranges within species prevent the determination of meaningful relationships between HP and weight.Data from various sources within species-sex subclasses did not differ with respect to b1for the model: log HP = b0+ b1(log W). However, source of data did affect b0for dogs, ewes, women and steers. Weight exponents (b1values) were significantly different for the sexes within the chicken, dog, and human species.Tests for equality of weight exponents showed that exponents derived for species-sex-source, sex-source within species, and species-source within sex subclasses were not equal (P<.001). Thus, a universal equation which relates HP to W should not be declared the best fitting equation for species-sex subclasses. It is concluded that W.75, which was developed from data of species varying widely in W, ignores effects other than weight which are peculiar to specific populations. Therefore many researchers have inappropriately adjusted biological data for variation in weight by dividing response criteria by W.75. A more appropriate adjustment would be to include Wbor log W as a covariable in the statistical model.

Fourteen mature, nonpregnant, nonlactating Angus cows (498 kg) were individually fed through two consecutive phases (maintenance [M], 80 d and ad libitum [A], 70 to 79 d) to estimate within-herd variation in individual cow ME requirements for maintenance (MEm) and to identify factors contributing to this variation. Body composition was determined at initiation of phase M, at termination of phase M (also initiation of phase A) and at the end of phase A by a two-pool D2O dilution technique. Daily MEm averaged 156.7 kcal/kg BW.75 (SD = 18.4 kcal/kg BW.75) and efficiency of ME use for tissue gain or loss averaged 76% (SD = 30%). Estimates of ME intake to maintain 1 kg of protein or 1 kg of fat were 192.9 (SE = 24.8) or 20.7 (SE = 21.5) kcal. These data indicate that among cows of similar fat masses, those with larger protein masses had higher energy requirements for maintenance. Daily MEmwas positively correlated (P< .16) with liver weight (r = .40) and relative proportions of liver (r = .44; P< .16) and heart (r = .48; P < .10) in the empty body. Also, daily MEmwas correlated negatively (P< .05) with weight (r = −.71) and relative proportion of omental and mesenteric fat (r = −.78). Estimates of ME required for deposition of 1 kcal of protein or fat were 5.56 (SE = 1.01) or 1.26 (SE = .09) kcal. Weight of liver and the sum of liver, spleen, kidney and heart weights increased 1.58 (R2= .47) and 1.95 kg (R2= .52) per kilogram of daily weight gain during phase A. These results indicate that increased performance caused increased organ mass (liver).

Dry matter intake and BW data from 14 mature, nonpregnant, nonlactating Angus cows that were individually fed through two consecutive 70- to 80-d periods (maintenance and ad libitum) were used to predict ADG (ADG = -.512 + .213 DMI − .0017 BW, R = .95). This equation then was used to identify feed efficiency types among these cows. Cows were identified as average type (A) if ADG was within one SE of predicted ADG, and as efficient (E) or inefficient types (I) if ADG exceeded one SE above or below, respectively, its predicted ADG. Four, four, and six cows were identified and grouped as I, A, and E types, respectively. During the maintenance period, DM and ME intake and ADG were similar (P> .10) across all three efficiency types. But during the ad libitum period, voluntary DM and ME intakes of I cows were greater (P< .05) than those of A or E cows. Average daily gains of I cows during ad libitum feeding were greater (P< .10) than those of A cows. Daily ME required for maintenance of I cows was highest, that of A cows was intermediate, and that of E cows was lowest (180.2, 154.6, and 135.1 kcal/kg BW.75, respectively). Inefficient cows tended (P> .10) to have less fat and deposited more protein (P< .05) than A and E cows (137.9 vs 77.2 and 46.2 protein g/d, respectively). Concurrent with higher protein accretion rates, liver weights of I cows were heavier (P< .05) than those of A and E cows (8.58 vs 7.79 and 7.68 kg, respectively). Inefficient cows were characterized by higher energy requirements for maintenance. Their high protein accretion may partially explain their higher maintenance requirements.

If agronomic characteristics could be used as criteria for judging quality of corn and sorghum cultivars for silage, the selection of genotypes best suited for silage would be facilitated. The objective of this study was to determine if agronomic characteristics of corn (Zea maysL.) and sorghum [Sorghum bicolor(L.) Moench, S. sudanense(Piper) Stapf, and their hybrid] cultivars are related to their silage quality. Over a period of 3 years, 49 silages, involving 11 corn cultivars and 14 sorghum cultivars, were produced and fed to sheep in conventional feeding trials. Eleven of the 14 sorghum cultivars were the sweet‐stem silage type. We measured fodder yield, height, %dry matter, and % plant parts [stems, ears or heads (EH), and leaves]. The quality measurements were acid detergent fiber (ADF); in vivo measurements, with sheep, of digestible dry matter (DDM); average daily gain (ADG); and dry matter intake/animal/day (DMI). The highest correlations were obtained between % stems or % EH and quality for both corn and sorghum silages. Percent leaves and plant height were in some cases highly correlated with quality measurements, but these relationships could be explained by high correlations of % leaves and plant height to % EH and stems. ADF concentration was lower in corn silage (29.0%) than in sorghum silage (34.9%). The low ADG of sheep fed sorghum silage (18.1 g compared to 64.5 g for corn silage) was primarily due to low DMI (649 g) and low DDM (55.6%) of the sorghum silage compared to the high DMI (777 g) and high DDM (63.8%) of corn silage. A regression analysis showed that nearly equal amounts of DDM intake above maintenance were needed for a unit of ADG from corn silage and from sorghum silage.

The effects of different chemicals, their concentrations and reaction times (1 day or 150 days) on composition and digestibility of poplar bark in vitro were studied. The chemical treatments used were NaOH, NaOH+S, Na2S, Na2SO3, Na2SO3+Na2CO3, CaO, CaO+NaOH, NaC10 and NaC102. Chemical concentrations ranged from 0 to 30 g/100 g bark on a dry matter basis. Treatment for 1 day with the higher concentrations of NaOH, CaO and CaO+NaOH decreased lignin (from 21.1% to 16.9, 19.7 and 20.7%, respectively) and hemicellulose (from 12.1% to 4.4, 6.6 and 7.0%, respectively). Na10 and NaC102decreased lignin from 21.1% to 12.4 and 12.4%, respectively. Na2S increased NDF content from 66.8 to 74.1% and ADF content from 54.7 to 60.1%. Na2SO3and Na2SO3+Na2CO3had little or no effect on chemical components. Treatment for 150 days with the higher concentrations of NaOH,CaO or CaO+NaOH decreased cellulose (from about 33.7% to 30.3, 28.7 and 30.7%, respectively), hemicellulose (from 11.5% to 5.9, 6.2 and 2.2%, respectively) and lignin (from 22.9% to 17.5, 17.3 and 16.4%, respectively). Na2SO3+Na2CO3increased cellulose from 33.5 to 36.4% and decreased hemicellulose from 11.5 to 8.3%; Na10 decreased cellulose from 33.5 to 28.7% and lignin from 22.9 to 14.6% and NaC102decreased the lignin content of the bark from 22.9 to 11.9%.In general, Na2S, Na2SO3and Na2SO3+Na2CO3had little or no effect on the in vitro digestibility of poplar bark. In vitrodigestibility of poplar bark was increased to the greatest extent (24 to 33%) by NaOH, CaO, CaO+NaOH, Na10 or NaC102treatments. However, longer reaction times were required to achieve maximum in vitrodigestibilities with CaO or CaO+NaOH treatments than with NaOH.

Two experiments were conducted to test physical and chemical processes which may increase the feeding value of poplar bark. In the first experiment, the effect of particle size on digestibility of poplar bark was studied using 18 growing lambs. The bark was ground through a hammer mill equipped with .32, .95 or 1.59 cm screens and ensiled for 10 weeks. The lambs were fed rations that consisted of 20% ground corn, 20% soybean meal and 60% bark, plus 25 g of a mineral and vitamin supplement. Dry matter digestibility was determined by the lignin ratio method. Dry matter digestibility of the bark, as determined by difference, was not enhanced when the bark was ground through the finer screens (27.4, 25.7 and 30.3% for screen sizes of .32, .95 and 1.59 cm, respectively).In the second experiment, the effects of reaction time, temperature and concentration of NaOH on the composition and in vitrotrue digestibility (IVTD) of poplar bark were studied. Two reaction times (1 and 20 days), three temperatures (25, 50 and 75 C) and five concentrations of NaOH (0, 3, 6, 9 and 12 g NaOH/100 g of bark dry matter) were used. Hemicellulose and lignin contents of the poplar bark were reduced by treatment with 9 or 12 g of NaOH per 100 g of bark. This effect of NaOH was obtained in 1 day and was not greatly influenced by temperature. Treatment of the bark with 9 or 12 g of NaOH resulted in significant (P < .05) increases in IVTD.

Studies were conducted with alfalfa-brome forage (alfalfa-brome, aerial part, early bloom, cut 2) harvested as hay (86.6% dry matter), haylage (50.8% dry matter) and silage (41.8% dry matter) to determine harvest and storage losses, performance of calves fed these feeds as their only energy source, net energy values and the efficiency of energy utilization for the three forage systems. Dry matter losses during harvesting were 25.4, 14.6 and 12.4% for hay, haylage and silage. Dry matter losses totaled 29.4, 22.1 and 21.3% and crude protein losses totaled 25.8, 27.6 and 21.2% during harvesting and storage for the respective feeds.Steer calves fed alfalfa-brome hay or haylage as their only source of dietary energy gained faster and consumed more dry matter than steers fed silage. Amounts of dry matter per 100 kg of gain were 1,099, 1,216 and 1,261 kg for steers fed hay, haylage and silage, respectively. Gain per hectare was not greatly influenced by method of harvesting and storage.

The effects of added nitrogen sources (urea, biuret or soybean meal) and a chemical antibacterial agent (sodium metabisulfite) on nitrogenous fractions of corn silage or corn stalklage during fermentation were studied using laboratory silos. Additions of crude protein increased final silage crude protein contents. Losses of crude protein during fermentation were small, at the levels of additions used. The nitrogen fraction which was increased to the greatest degree by urea additions was ammonia. Only small amounts of urea remained following fermentation. Much of the ammonia was lost upon drying of silage samples. This suggests that accurate analyses for crude protein are obtained only with non-dried silage. Final silage nitrate content was greater when sodium bisulfite was added but appeared to be lowered by the extended fermentation which resulted when urea was added.

The influence of added sodium metabisulfite and nitrogen sources (urea, biuret or soybean meal) on corn silage or corn stalklage fermentation was studied using laboratory silos. As measured by total and sequential gas productions, and final fermentation acid concentrations, the crude protein additions, particularly urea, caused increased and extended fermentations. Nitrogen additions were associated with increased wet and dry weight losses. However, energy losses among treatments as measured by calorimetry of wet silage were not related to the wet and dry weight losses of the silages. Biuret did not influence fermentation appreciably. Sodium metabisulfite delayed fermentation, but increased gas production and wet and dry weight losses. Lactic acid concentration was lower in fermented material which had bisulfite added, but concentrations of other acids were increased. Stalklage underwent fermentation similar to that of whole plant corn silage of similar moisture content.

Changes in proximate components of corn cobs harvested at early milk, early dough, mid-dent and mature stages of kernel development were decreases in crude protein, ether extract and ash, and an increase in crude fiber with advancing maturity. Cell wall constituents and acid detergent fiber contents also increased with advancing maturity.A digestion study showed that the apparent digestibility of total carbohydrates, crude protein, cell wall constituents, hemicellulose, gross energy and organic matter decreased, while ether extract increased in apparent digestibility as the cobs matured. Corn cobs from ear corn of early milk maturity had TDN and DE values approximately 115% those of mature cobs. Cobs from corn in early dough and mid-dent stages of kernel maturity had approximately 110 to 112% of the TDN and DE values of mature cobs. Calculated TDN values for ear corn at early milk, early dough and mid-dent stages of maturity were 88.0, 90.4 and 98.4% of values for mature ear corn.

In two digestion studies, the apparent digestibilities of nutrients (ether extract, total carbohydrates, gross energy and organic matter) in corn grain increased as test weight (or maturity) increased. In both studies, the crude protein of the heaviest (most mature) corn was the most digestible. TDN and DE contents of corn increased as test weight increased. Regression analyses of the combined TDN values from both trials gave the equation: % TDN=78.0+0.0246X (X=test weight in gm./1.). Comparison of TDN and price indices indicated that the commonly applied test weight discount unduly discriminates against corn grain having a test weight less than 696 gm./liter.

Since corn producers strive for maximum yields by planting varieties which will utilize the full growing season and because environmental conditions and the length of the growing season vary each year, it is not uncommon to encounter a killing frost before the entire crop is mature. Corn grain from a crop which has had its growth interrupted is generally soft; consequently, kernel moisture levels have often been equated with corn maturity. However, it has been established (Dessureaux, Neal and Brink, 1948; Shaw and Thorn, 1951) that physiological maturity of corn grain (maximum dry kernel weight) occurs at kernel moisture levels ranging from 30 to 44 percent. Thus, corn can be soft and at the same time mature. Conversely, physiologically immature corn grain would be both dry and immature after drying. Therefore, kernel moisture levels do not always indicate degree of maturity.Several authors (Kennedy et al., 1904; Thatcher, 1929; Robison, 1944; Shaw and Thorn, 1951; Heidenreich and Wilson, 1952; Olson and Gastler, 1953) have observed that a reduction in corn grain test weight often accompanies hail, frost or drought damage.

Composition studies showed that poplar bark obtained from a commercial peeling operation contained, on a dry matter basis, 2.2% crude protein, 53.7% crude fiber, 73% cell wall constituents, 59.1% acid detergent fiber and 13.9% permanganate lignin. Phosphorus, potassium and sodium contents of poplar bark were low, but calcium and zinc levels were high in relation to ruminant requirements.Laboratory silo fermentation studies showed that addition of barley, an Aspergillus oryzaefermentation product or a combination of barley and Aspergillus oryzaefermentation product was not necessary for proper fermentation to take place. Also, moisture contents of 25 to 50% were adequate for proper fermentation.In the sheep digestion trial, the digestion coefficients for organic matter, crude protein, total carbohydrate, cell contents and energy were greater for rations containing 13% barley and 87% ground poplar bark than for rations containing only poplar bark. TDN and digestible energy contents were also significantly increased when the ration contained 13% barley. These improvements in digestibility and digestible energy contents were due to contributions from barley and not to an influence of barley on the poplar bark. The addition of an Aspergillus oryzaefermentation product did not significantly influence the digestibility of nutrients. The TDN of poplar bark was found to be 36.7% on a dry matter basis.In the growth trial, sheep fed poplar bark ad libitumand 0.23 kg. of soybean meal daily lost weight. When 0.34 kg. oats and 0.13 kg. soybean meal were fed in addition to ensiled poplar bark, the sheep had an average daily gain of 0.034 kg. during the last 34 days of this 48-day trial.These data show that poplar bark contains small amounts of available energy in comparison to common feedstuffs. Other by-product feeds, poor quality hay or straw may be better sources of energy during emergency periods than poplar bark.

Water contents of 15 artificial silages and 18 natural silages were determined by a new chemical procedure which allows direct estimation of the water content and simultaneous correction for endogenous acids and bases. The chemical procedure and two oven drying techniques were evaluated by comparing the water contents determined by each method with the true water contents of 15 artificial silages. The chemical determination of water was an excellent procedure for estimating the true water contents of artificial silages containing up to 20% non-aqueous volatiles. The chemically determined water contents of 18 natural silages were approximately 2.4 and 2.7 percentage units lower than those determined by drying in a vacuum oven at 70 C or a forced-air oven at 105 C, respectively.The chemical procedure involves reacting both an ethanolic silage extract and a blank with a water-sensitive reagent, incubation for 15 min. at 50 C, and titration with standard ethanolic HCl. This procedure is rapid, specific for water, simple to conduct and suitable for routine laboratory analyses.

Improvement of the interpretation of feedlot data is discussed. Five items discussed were: (1) bias of nutritional data in favor of highly fermented feeds because of errors in determining moisture content, (2) correction of live weights to equal dressing percentages, (3) covariance correction of final data to equal initial values, (4) within treatment comparisons of factors influencing gains and (5) regression correction of carcass data to equal carcass weights.

In a feeding trial involving fifty 75-lb. lambs, a 7.13 percent crude protein basal ration was fed. Adding either urea, biuret or crude biuret, or replacing part of the corn with soybean oil meal, significantly increased the average daily gain and feed efficiency of the lambs. No significant differences were noted among the lots fed the various supplemental nitrogen sources.It is concluded that, under the conditions of this experiment, urea, biuret and crude biuret are satisfactory sources of supplemental nitrogen for growing-fattening lambs. In addition, biuret appears to be less toxic than urea when fed in large amounts.

Digestion and balance trials were conducted with steers and wethers fed normal and high-salt rations. High salt intake did not significantly affect the digestibility of components of rations fed to steers. It decreased the digestibility of organic matter and nitrogen-free extract by wethers. There was a slight but non-significant decrease in nitrogen retention in both species. Feeding the high level of salt resulted in a small but significant increase in the retention of sodium and chloride in both steers and wethers. Nearly all (87 percent for the steers and 94 percent for the wethers) of the ingested sodium and 98 percent of the chlorides were excreted in the urine.

Two experiments with 125 beef cattle were conducted to study the effects of feeding:A limited amount of either baled or pelleted hay;ground or pelleted ear corn;a tranquilizer.The interactions of pelleted hay with ground ear corn and baled hay with pelleted ear corn were significant (P<.05) with respect to weight gains. Cattle fed pelleted hay had significantly higher carcass grades (P<.01) and marbling scores (P<.05) than cattle fed baled hay. Cattle fed ground ear corn had significantly higher (P<.05) carcass grades than cattle fed pelleted ear corn. Feeding a tranquilizer had no effect upon feed lot performance or carcass characteristics.

Results of four trials are reported in which diethylstilbestrol and oxytetracycline (alone or in combination), linseed oil meal, soybean oil meal and various levels of corn silage were fed to fattening cattle.Average daily gains were increased significantly and less feed per unit gain was required when diethylstilbestrol and a combination of diethylstilbestrol and oxytetracycline were fed in two trials. Oxytetracycline increased daily weight gains significantly in one trial and slightly in three other trials. It improved efficiency of feed use. Cattle fed linseed oil meal gained 5% more rapidly than cattle fed soybean oil meal. Cattle “full-fed” silage during the high-forage phase of feeding had significantly lower carcass grades than cattle fed lesser amounts of silage.

Samples of rumen fluid were collected at intervals from a fistulated steer fed (1) a high-roughage ration regularly, (2) no ration, starvation for 3 days, (3) refed (following starvation) a high-roughage ration. The abilities of rumen fluid to digest cellulose in vitroand to reduce the viscosity of a stable suspension of carboxymethylcellulose (CMC) were determined. A fraction (S-1) of rumen fluid freed of protozoa and most plant material and a second fraction (S-2) freed of bacteria, protozoa and plant material were also tested for activity on CMC.The pH of rumen fluid rose continuously during the starvation period to a high between 7.65 and 7.94. The ability of rumen fluid to digest cellulose in vitrodecreased greatly when the steer was starved for 3 days. All fractions of rumen fluid also decreased in their activity on CMC.Fractions of rumen fluid obtained shortly after feeding had been resumed following starvation showed unusually high, but approximately equal, activity on CMC. The extremely high activities of the S-2 fractions indicated that the enzymes were largely extracellular at that time. The ability to digest cellulose in vitrowas normal in 3 to 4 days after feeding was resumed following starvation. Activities of the various fractions on CMC were normal when the steer had been refed 2 to 4 days after starvation with one exception. This exception might have been the result of a change in the normal proportion and metabolism of microbial life in the rumen.No differences in the activities of rumen microorganisms could be attributed to the type of hay the steer received before or after the starvation period. The steer readily consumed all of its ration at each feeding.

MOST natural rations fed to ruminants contain adequate sulfur to meet the animals' requirements. However, the use of non-protein nitrogen in ruminant rations increases the possibility of a sulfur deficiency, since the protein-rich feeds that have been replaced by urea are usually excellent sources of this element. Methionine, elemental sulfur or sulfate-sulfur supplementation of rations containing inadequate sulfur has produced beneficial results (Loosli and Harris, 1945; Lofgreen, Loosli and Maynard, 1947; Garrigus et al., 1950; Thomas et al., 1951; Goodrich, Johnson and Meiske, 1967). However, the availability of sulfur from each of these compounds must be clearly defined before recommendations can be made relative to the amounts of each form that must be fed.This study was undertaken to determine the true digestibility and retention of the sulfur from elemental sulfur, sodium sulfate and L-methionine and to determine the percentage of sulfur from each that was available for incorporation into wool, muscle tissue and several other tissues and organs.

Single doses of radioactive sulfur (35S) of three different chemical forms (elemental sulfur, sodium sulfate and methionine) were given orally via gelatin capsule to lambs. The lambs were also fed these same forms of supplemental sulfur prior to and following the administration of 35S. Radioactivity from sodium sulfate appeared in the plasma more rapidly than did radioactivity from methionine or elemental sulfur. Large amounts of 35S from sodium sulfate appeared in the plasma 1.0 hr. after dosing, while that from methionine and elemental sulfur appeared in largest amounts 42 to 54 hr. after the administration of the isotope. Lambs orally dosed with 35S-methionine had higher plasma isotope contents for the period from 36 to 192 hr. than plasma from lambs that received 35S-sodium sulfate or 35S-elemental sulfur. The similar time and pattern of appearance in plasma of 35S from elemental sulfur and methionine suggests that the sulfur from elemental sulfur which appeared in the plasma may have been incorporated into forms similar to those for methionine prior to absorption. These observations may also suggest similar sites of absorption.The major pathway of excretion of 35S from elemental sulfur and methionine was via the feces. Losses of 35S from sodium sulfate were about equally divided between feces and urine. During the 8 days following administration of the isotopes 8.52, 20.12 and 6.09% of the sulfur from elemental sulfur, sodium sulfate and methionine was lost in the urine. Fecal losses of 35S from the respective sources were 63.37, 21.77 and 20.39% of the administered doses.

Four crops of corn grown on highly fertilized land were ensiled with and without the addition of 0.4% (w/w) sodium bisulfite to determine the effect of sodium bisulfite on toxic gas production in field silos. The silages were fed to gestating beef cows and dairy cows to assess the nutritional and toxicological properties of bisulfite-treated silages.Sodium bisulfite effectively inhibited NO2gas evolution. Bisulfite-treated silages tended to contain more residual nitrate and carotene and significantly less organic acids. Residual bisulfite of the treated silages was approximately one-fourth of the amount added initially.Beef cows fed bisulfite-treated silages containing up to 0.9% nitrate (NO3) on a dry matter basis gained less in 1 of the 2 years, but calving performance was not affected in either year.Methemoglobin formation was negligible in all cattle. Dairy cattle fed bisulfite-treated silages had significantly higher plasma carotene and liver carotene. This effect was not observed with respect to plasma carotene and plasma vitamin A values in beef cattle. Plasma tocopherols were significantly higher in cows fed bisulfite-treated silages.

The intake of forage plants by ruminant animals is a crucial determinant of forage quality. Laboratory assays have sometimes provided reasonable estimates of the intake potential of grasses and legumes. Laboratory procedures have not been adequately tested for their ability to predict intake of silages of corn (Zea maysL.) and sorghum (Sorghum bicolor[L.)] Moench, S. sudanense[Piper] Stapf., or their hybrids). Our objectives were to determine whether various biological and chemical tests proposed for measuring forage quality are applicable to prediction of intake of corn and sorghum silages, and to determine whether digestibility and intake of these silages are associated. In vivo digestibility of 49 silages was measured by using lambs in conventional 30 to 35‐day stall trials. We measured voluntary intake by using other lambs in feeding trials that extended 41 days or more. Dry matter intake (g/Wkg0.75) by lambs was correlated (r = 0.66) with in vivo digestible dry matter of sorghum silages. The correlation between intake and digestibility was much lower (r = 0.40) for corn silages. The biological laboratory assays were not as well correlated with intake of sorghum silages as were several chemical assays. However, a biological assay (in vitro true digestible dry matter) was best associated with intake of corn silages (r = 0.64) of all assays. Of the chemical assays, Fonnesbeck and Harris cell walls, acid detergent fiber, crude fiber, and calculated cellulose accounted for 24% or more of the variation in intake of corn silages and 60% or more of the variation in intake of sorghum silages. Crude protein was highly correlated (r = 0.81) with intake of sorghum silages, but it was not correlated with intake of corn silages. We present simple regression equations for prediction of intake of sorghum silages from the five laboratory assays that accounted for 60% or more of the intake variation.