Total tract digestion coefficients for dry matter (DM) and neutral detergent fiber (NDF), passage rates for grain and roughage components of diets and liquid turnover were measured for 65 and 90% concentrate diets in separate 4 x 4 Latin square experiments using intact growing steers. Kinetics of in situ digestion for DM and NDF in diet ingredients, rumen pH, volume and DM distribution were determined in mature, rumen cannulated steers. Rates of passage and digestion were combined to calculate apparent extent of ruminal digestion (AERD) for diet ingredients. Diets were based on steam flaked milo. The control roughage was chopped alfalfa hay (AH). In 65% concentrate diets, chopped wheat straw (WS), bermudagrass straw (BS) or cottonseed hulls (CSH) replaced 50% of the AH. In 90% concentrate diets, all of the AH was replaced by WS, BS or CSH. Total tract starch digestion was not influenced by source of roughage at either concentrate level. In 65% concentrate diets, total tract digestion of DM and NDF was not adversely affected by substitution of WS for 50% of the AH. Digestion of these fractions was lower (P<.05) for BS and CSH diets, but the severity of depression was greatest (P<.05) for the CSH diet. Reduced digestibility of the CSH diet was attributed to lower digestibility of CSH in comparison with AH. Although WS and BS were also less digestible than AH, their inclusion in the diet improved (P<.05) AERD of DM and NDF from milo and AH. Improved AERD for NDF appeared to be related to the raft-forming properties of WS and BS, and their ability to maintain rumen pH in a more desirable range for NDF digestion. In 90% concentrate diets, effects of roughage source on utilization of milo were minimal. Total tract digestion of DM and NDF was lower (P<.05) for WS, BS and CSH diets than for the AH diet, because of dilution of the more digestible AH by these roughages. Wheat straw had a tendency to moderate ruminal pH and consequently might be more useful in high concentrate diets than roughages such as CSH and BS.

Cattle grazing patterns on Lehmann lovegrass rangelands often create heavily-grazed (HG) areas surrounded by lightly-grazed (LG) or ungrazed patches. The purpose of this study was to characterize the forage resource and ingestive behavior of cattle grazing Lehmann lovegrass plants in both LG and HG patches on the Santa Rita Experimental Range. The general hypothesis was that residual bunchgrass vegetation resulted in sward characteristics which physically inhibited the efficiency of cattle grazing by increasing the manipulative activity per harvested bite. The overall heights of residual stems and green tillers averaged 70 and 49 cm for LG, 8 and 9 cm for HG patches. Biomass of total standing crop (SC), residual vegetation (RV) and green herbage (GH) averaged 4159, 3395 and 764 kg/ha for LG, 345, 185 and 160 kg/ha for HG patches, respectively. Bulk density of SC, RV and GH of LG and HG patches averaged 58, 48, and 19 [(gm/cm³) X 10⁻⁵] for LG, 38, 23 and 20 [(gm/cm³) X 10⁻⁵] for HG patches, respectively. The ratio of green herbage to residual vegetation averaged 0.22 for LG and 0.86 for HG patches. The different sward structure of LG and HG patches affected the ingestive behavior of the grazing cows. Overall handling time for each grazing bite averaged 1.5 and 1.2 sec/bite in LG and HG patches, respectively. Cows employed different foraging tactics in response to the dynamic changes of the sward conditions. Cows employed top biting extensively to harvest the seed-head and other green herbage at the top of the sward surface. As the height of residual stems increased and dominated the upper strata of the sward, side and low biting were mainly used by the cows as grazing methods to bite the plants to reduce the manipulative activity. Avoidance of LG patches or preference for HG patches was related to the sward structure and largely shaped by the build-up of residual vegetation. Removal of residual vegetation through fire, mowing or heavy utilization for short periods late in the growing season to allow for more accessible green herbage could improve both animal and pasture utilization of the range resource.

The abundance of Lehmann lovegrass (Eragrostis lehmanniana, Nees.) on Arizona ranges prompted this research to evaluate the animal production and winter palatability of this species. Sulfurcoated urea (SCU) was applied to desert grassland range to minimize the risks of fertilization that are brought about by drought and unseasonable rainfall. Tebuthiuron (TEB) was also applied to pasture to document any beneficial effects on forage production and palatability. During the 2 years of this project, two experiments were conducted. A preference study examined forage and animal responses to one-time applications of fertilizer or herbicide treatments and combinations. The second experiment compared the potentials for improved animal production from SCU and SCU + TEB with untreated range. Results indicated that the fertilizer and combination treatments produced more forage than the untreated plots. Tebuthiuron improved forage production by 200 percent in the first year but reduced yields in the second year. The high rate of TEB was detrimental in both years. Forage utilization was improved by all treatments. Nitrogen increased the crude protein content of the grasses proportional to the rate applied. Tebuthiuron also enhanced the protein content of the forage. Total available carbohydrates were lowest in TEB treated forages, but digestibility was increased. Only the 31 lb SCU appeared to be economically profitable. However, excellent carry-over by the 60 SCU treatment suggested profitability after 3 years. Results from the grazing study indicated that production was significantly improved by both treatments. Although forage production was similar for the treatments, the SCU-only pasture provided superior animal gains and greater carrying capacity than the SCU + TEB pasture, even though forage digestibility and apparent disappearance were greater on the combination pasture. The difference in animal performance was attributed to low levels of carbohydrates available from the combination pasture. Treatment of Lehmann lovegrass/blue grama range with 40 SCU/acre appeared profitable for raising growing beef animals, but not for maintenance of a breeding cow herd.

Two lactation studies with accompanying digestion trials were conducted to compare the feeding value of Pima cottonseed, with differing degrees of processing, to short staple cottonseed for lactating dairy cows. Additional tests were conducted to examine physical and chemical characteristics of both Pima and short staple cottonseed and the effect of processing on storage characteristics of cottonseeds. Pima cottonseed is higher in CP and ether extract and lower in NDF and ADF than short staple seed. Pima seed has a greater bulk density, a greater proportion of the (-)-gossypol isomer and a lower proportion of the (+)-gossypol compared to short staple cottonseed. In the first lactation study, milk yield was similar across all treatments. Milk fat was higher (P < .05) for finely cracked Pima (x 3.0 mm) and whole Pima diets. Feed efficiency was greatest (P < .05) for the cracked Pima diet. Percentage whole seed passing into the feces of that consumed, was 11% for the whole Pima and 5.2% for the short staple. Total tract digestibility of ADF decreased and that of ether extract increased in cows fed cracked Pima compared to whole Pima or short staple. In the second lactation study, milk yield was higher (P < .05) for cows fed ground Pima (x 2.5 mm), than either whole Pima or coarsely cracked Pima (x 3.5 mm), with short staple intermediate. Feed efficiency (SCM/DMI) was greater for cows fed ground Pima and short staple diets (1.14) than for those fed cracked Pima or whole Pima. Stearic acid was lower, and linoleic and linolenic acids were higher in milk of cows fed ground Pima compared to short staple. Passage of whole seed was two-times greater for cows fed whole Pima compared to whole short staple (12.3% vs. 6.2%), and processing of Pima seed eliminated whole seeds passing in the feces. Ether extract digestibility was lower for the whole Pima compared to the other treatments. Storage of whole, cracked or ground seeds at 32°C and 30% relative humidity for up to 30 d did not cause rancidity or aflatoxin contamination. Storage of processed seeds in covered containers for nine months caused only slight increases in free fatty acid content, and no change in the whole seeds.

Studies were conducted to determine the suitability of diaminopimelic acid (DAP), lysine and lysine-leucine as bacterial markers, and to compare ruminal, postruminal and total tract protein utilization and bacterial protein synthesis of sorghum grain, corn and barley based diets by beef steers. Six abomasally fistulated steers were fed 81% grain diets with 10.7% crude protein (CP) in a replicated 3 x 3 Latin square design. Diaminopimelic acid, lysine and leucine were determined in bacteria isolated from abomasal digesta (two sampling times) and rumen contents, and the ratios were used to estimate percent abomasal bacterial protein. Diaminopimelic acid concentrations in ruminal and abomasal bacteria were positively correlated (r = .40), but correlations between sample sites for lysine and leucine were essentially zero. Correlations between abomasal sampling times for the three amino acid concentrations were positive (mean r = .44). Rankings of percent bacterial protein in abomasal digesta for dietary treatments were similar based on amino acid ratio methods (DAP vs lysine vs lysine-leucine) using bacteria of rumen contents. Digestibility and bacterial synthesis data were based on lysine-leucine ratios from bacteria of rumen contents and chromium oxide ratios (digesta flow marker). Ruminal digestibilities of organic matter (OM), corrected for bacterial OM synthesis in the rumen, tended to be lower (P < .07) for sorghum grain and corn diets than for the barley diet (43, 48 vs 62%, respectively). Mean ruminal and postruminal CP digestibilities were similar (P > .05) for the three diets (-38 and 72%, respectively). Apparent total tract CP digestibility was lower (P < .05) for the sorghum grain diet than for corn or barley diets (61 vs 66 and 68%, respectively). Ruminal digestibility of feed nitrogen was lower for the sorghum grain and corn diets than for the barley diet (27 and 40 vs 69%, respectively). Percent bacterial nitrogen in the abomasum was much higher (P < .05) for the barley diet compared to the sorghum grain and corn diets (72 vs 47 and 53%, respectively). Postruminal digestibility of bacterial nitrogen was lower (P < .05) for the sorghum grain and corn diets compared to the barley diet. It is postulated that the lower apparent digestibility of sorghum grain protein in the total tract is related to a lower extent of feed protein and OM digested in the rumen.

Six lactating Holstein cows received ammonia-treated or untreated aflatoxin-contaminated whole cottonseed (AFWC) or pure AFB₁ with their regular ration. Treatments were: AFWC (5,010 ppb AFB₁), 4 kg/day; the same AFWC treated with 1.5% anhydrous ammonia and 10% water; pure AFB₁ (2.2 mg twice daily) given in capsules; same amount AFB₁ treated with 50% NH₄OH for 26 days at 29°C; same amount ammoniated AFB₁ acidified to final pH of 5.0; same treatment as first except concentration of AFB₁ was 5,511 ppb. Levels of aflatoxin M₁ (AFM₁) in milk were monitored before, during, and after each treatment, and conversion and feed-through ratios were calculated. Feed consumption and milk production were also measured. Mutagenicity of acetone extracts of spray-dried milk was determined using Salmonella/microsomal assay. Ammoniation of AFWC did not reduce concentration of AFB₁ to below FDA action level; however, when the seed was fed, the concentration of AFM₁ in milk was less than FDA action level (0.5 μg/L). Ammoniation of AFB₁ was very effective in reducing levels of AFM₁ in milk of treated cows to less than the FDA action level. The average AFB₁/AFM₁ conversion ratios for the steady-state period of AFM₁ excretion in milk while giving AFWC and AFB₁ was 1.06% and 1.18%, respectively. Ammoniation of AFWC reduced the average AFB₁/AFM₁ ratio to 0.20% during the constant-state period of AFM(,1) excretion in milk. The ration containing AFWC (5,010 or 5,511 ppb AFB₁) caused a highly significant decrease in total milk production and feed consumption; ammoniated AFB₁ decreased total milk production significantly. Complete disappearance of AFM₁ from milk after discontinuing Treatments 1-6 was 120, 48, 95, 72, 96, and 120 h, respectively. Under these laboratory conditions, significance of the results of the Ames test was questionable.

An experiment was conducted to study the effect of prolonged nutritional stress on the reproductive performance of twelve Holstein dairy heifers. Energy intake was reduced to 60% NE(m). The animals lost 20% of their body weight during energy restriction (97 days) and gained 29% during the high energy feeding (44 days). Estrous cycles were irregular, delayed, or ceased completely. The conception rate was only 25% during energy reduction. Cycles were reestablished and conception rate improved (67%) during the high energy feeding. Heifers were designated as fertile or infertile according to their success or failure to conceive during the energy reduction period. Serum thyroxine (T₄) levels were slightly decreased (P > .05) while triiodothyronine (T₃) levels were significantly depressed (P < .01) during energy restriction in both fertile and infertile heifers. Serum thyroxine levels were slightly increased (P > .05) in the fertile heifers, but significantly increased (P < .01) in the infertile heifers during high energy feeding. Serum triiodothyronine levels were significantly increased during high energy feeding in both fertile (P < .05) and infertile (P < .01) heifers. Concentrations of blood cortisol were relatively higher in the fertile than in the infertile heifers during the ad libitum and energy restriction periods. This suggests that the fertile heifers possessed elevated adrenal activity that the infertile heifers did not have. Concentrations of blood progesterone of the infertile heifers were severely depressed (P < .01) during the submaintenance feeding while those of the fertile group were not affected (P > .05). Blood glucose levels were significantly reduced during energy reduction and significantly increased during high energy feeding in both groups of heifers (P < .01 for infertile heifers). Blood glucose levels of the infertile heifers at time of insemination (period of energy restriction) were as low as their average levels of the period. Glucose levels of the fertile heifers at time of breeding (period of energy restriction) were greater than their mean concentration during that period and were similar to the mean levels of glucose during the ad libitum period. Low progesterone levels are indicative of ovarian inactivity under such stressful conditions. Adrenal inactivity, (as reflected by low cortisol secretion) and low blood glucose levels at time of insemination of the infertile heifers are probably associated with infertility during submaintenance feeding in dairy heifers.

Automated total collection (ATC) of digesta from four steers fitted with duodenal re-entrant cannulas was compared with flow estimations based on Cr₂O₃and acid detergent lignin concentrations of ATC samples. In two successive periods, each steer was fed about 4 kg daily of an all-roughage or an 80% sorghum grain diet. Digesta samples were automatically taken and pooled every 2 hr, during 3- to 6-day collections. Sample aliquots, representing 4% of the digesta measured in each 2 hr were pooled to represent 24-hr digesta flow. Data of 2-hr samples were used to study diurnal flow patterns. Duodenal digesta and dry matter flow rates estimated by Cr₂O₃and lignin were greater by (TURN) 15% than flow rates measured by ATC. Mean recoveries of Cr₂O₃and lignin at the duodenum were 93 and 89%, respectively. Animals fed the roughage diet had about 55% greater digesta flow rates than when fed the concentrate diet (42 versus 65 l daily average by ATC). There appeared to be an interaction between diets and markers. Apparent ruminal dry matter digestibility calculated from direct measurements by ATC was 44% for the concentrate diet and 37% for the roughage diet. Rumen digestbility values based on Cr₂O₃and lignin were about 25% lower than the ATC values. Average coefficients of diurnal variation for digesta flow were 29% in the concentrate diet and 34% in the roughage diet. Estimations from Cr₂O₃and lignin based on 2-hr samples could either under- or overestimate digesta flow by 31 to 350% of the 24-hr flow based on ATC. Thus, special emphasis should be given to the problem of sampling procedures when using indicators and spot-sampling technique to estimate digesta flow. There was evidence of a 24-hr cycle for the whole digesta flow in the grain diet, with a period of low flow before the onset of the light hours. No consistent flow pattern could be identified in the roughage diet. Lignin concentration patterns in digesta were somewhat similar for both diets; however, Cr₂O₃patterns were different between diets. Digesta dry matter concentration followed a similar pattern to that of Cr₂O₃in the grain diet and to that of lignin in the roughage diet, suggesting that the flow patterns of solid phase components of digesta may also be differentially affected by the dietary concentrate: roughage ratio.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

No description available.