109 research outputs found
Canonical decompositions of hyperbolic 3-orbifolds
No full textThis thesis describes the theory behind Sym, software created by the author for computations
with finite-volume cusped hyperbolic 3-orbifolds. The main purpose of Sym, in
its current form, is to compute canonical (Epstein-Penner) decompositions of these orbifolds.
This was originally motivated by a joint project between the author, his advisor, and
his advisor’s other graduate students to create a census of orbifolds commensurable to the
figure-eight knot complement.
Underlying Sym is a non-standard notion of an orbifold triangulation, in which tetrahedra
may be labeled with groups of symmetries acting on them. This allows us to consider
fully ideal hyperbolic triangulations of orbifolds, which we attempt to treat in the same
way that SnapPy treats ideal triangulations of manifolds. SnapPy is powerful existing software
for hyperbolic 3-manifolds and some orbifolds, originally developed by Weeks and now
maintained by Culler, Dunfield, and Goerner.
The way SnapPy finds canonical decompositions of hyperbolic manifolds is complicated
both theoretically and computationally, and relies on influential work by Epstein, Penner,
Weeks, and others. The main goal of this thesis is to extend that work to orbifolds. A key
idea we develop is an orbifold version of Pachner moves, which are moves which change an
orbifold triangulation locally
The Politics of Foreign Direct Investment in Authoritarian Regimes
No full textExisting scholarship does not account for why foreign direct investment (FDI) inflows have been increasing to many authoritarian countries in recent decades, with some authoritarian developing countries attracting levels of FDI similar to those in democratic developing countries. This dissertation argues that while authoritarian countries are in general more risky than democratic countries, this risk can be minimized when authoritarian regimes are constrained from both “above” and “below.” Authoritarian regimes that sign international investment treaties signal FDI-friendly policies and are constrained from backtracking on those policies. At the same time, authoritarian regimes that allow some degree of citizen participation in policymaking are constrained from deviating from FDI-friendly policies, which are generally preferred by citizens. In sum, it is hypothesized that authoritarian regimes that sign international investment treaties and maintain relatively high levels of citizen participation will attract the most FDI inflows. This hypothesis is tested using micro and macro level empirical evidence. Specifically, multilevel ordered probits of survey data on citizen preferences for FDI and statistical regressions of panel data on global FDI inflows are conducted. Estimation results confirm both the theoretical foundations and formal hypothesis of this dissertation: citizens in authoritarian countries view FDI inflows as welfare-enhancing and authoritarian countries with bilateral investment treaties and high levels of citizen participation attract the most FDI inflows. Additionally, results from an original survey of U.S. foreign investors reveal that multinational companies are aware of and value international investment treaties and freedom of association in host nations, thereby providing key primary evidence in support of the hypothesis. Finally, a comparative case study of Jordan and Syria further illustrate the micro-foundations of the argument. While both Jordan and Syria have signaled a dedication to liberal economic policies, Jordan has been the successor in attracting FDI inflows because of its participatory decision-making processes. This dissertation contributes to international political economy, international organization, and authoritarian political institution research by illuminating the domestic factors that provide credibility of compliance to international treaties signed by authoritarian countries. Previous literature has failed to address the variation of foreign investment inflows to authoritarian regimes and the role of compliance to international investment treaties in attracting these investment inflows to authoritarian countries
INFLUENCE OF FORAGE LEVEL AND CORN GRAIN PROCESSING ON WHOLE-BODY UREA KINETICS, AND SEROSAL-TO-MUCOSAL UREA FLUX AND EXPRESSION OF UREA TRANSPORTERS AND AQUAPORINS IN THE OVINE RUMEN, DUODENUM, AND CECUM
No full textThe process of urea recycling to the gastro-intestinal tract (GIT) is an evolutionary adaptation that allows ruminants to maintain a positive nitrogen (N) balance, particularly when faced with a dietary protein deficit. Recycled urea-N can enter all GIT compartments; however, the rumen is where most of the anabolic usage occurs as it provides a N source for microbial protein synthesis, thus providing amino acids to the host animal when microbial protein is digested at the small intestine. The objective of this thesis research was to determine the effects of forage level and corn grain processing on N utilization, primarily focusing on dietary effects on whole-body urea kinetics and apparent N balance, and ex vivo serosal-to-mucosal urea flux (Jsm-urea) across ruminal, duodenal, and cecal epithelia. Additionally, to better understand the mechanisms associated with whole-body N utilization across the aforementioned GIT regions, dietary effects on regional fermentation characteristics and messenger ribonucleic acid (mRNA) expression of urea transporters (UT) and aquaporins (AQP) were also assessed. Sheep were used as an experimental model for ruminants. Thirty-two wether lambs (37.2 ± 1.7 kg initial body weight [BW]) were blocked by BW into groups of 4 and assigned to 1 of 4 diets (n = 8) in a 2 x 2 factorial design. Dietary factors were forage level (30% [LF] vs. 70% [HF]; DM basis) and corn grain processing (whole-shelled [WS] vs. steam-flaked [SF]). Provision of WS or SF corn was expected to alter the location of starch digestion in the ruminant GIT, with SF corn expected to shift starch digestion to the rumen, and WS corn expected to shift starch digestion to the intestine and hindgut. Four blocks of lambs (n = 4) were used for the in vivo metabolism trial to determine N balance and whole-body urea kinetics. Whole-body urea kinetics were determined using 4-d double-labelled urea ([15N15N]-urea) isotopic infusions, with concurrent total collections of urine and feces to determine isotopic enrichments and N balance. After 23 d of dietary adaptation, all lambs were killed (one per day for logistical reasons) on the morning of d 24 and ruminal, duodenal, and cecal epithelia were collected to determine Jsm-urea (using the Ussing chamber model) and mRNA expression for UT and AQP. Lambs fed LF had greater DM (1.20 vs. 0.86 kg/d; P < 0.01) and N (20.1 vs 15.0 g/d; P < 0.01) intakes than those fed HF. Lambs fed SF corn had greater DM (1.20 vs. 0.86 kg/d; P < 0.01) and N (20.6 vs. 14.5 g/d; P < 0.01) intakes than those fed WS. When expressed as a percent of N intake, total N excretion was greater in lambs fed HF diets compared to those fed LF diets (103 vs. 63.0%; P < 0.01). Also, total N excretion (as a percent of N intake) was greater in lambs fed WS corn compared to those fed SF corn (93.6 vs. 72.1%; P = 0.02). Apparent N balance, expressed as a percent of N intake, was greater in lambs fed LF diets compared to those fed HF diets (37.0 vs. -2.55%; P < 0.01). Similarly, lambs fed SF corn also exhibited a greater apparent N balance (28.0 vs. 6.50; P = 0.02) compared to lambs fed WS corn, when expressed as a percent of N intake. Endogenous urea production (UER) tended to be greater in lambs fed HF diets (17.6 vs. 14.3 g/d; P < 0.10) compared to those fed LF diets. Moreover, lambs fed HF diets also had greater urinary urea-N loss (as a proportion of UER) (0.38 vs. 0.22; P < 0.01), reduced amounts of urea-N returning to the GIT (as a proportion of UER) (0.62 vs. 0.78; P < 0.01), and overall, a reduced amount of urea-N allocated towards anabolism (as a proportion of urea-N GIT entry; GER) (0.12 vs. 0.26; P < 0.01) compared to those fed LF diets. Ruminal pH was similar in lambs fed SF and WS with HF diets, but it was lower in lambs fed SF compared to WS with LF diets (interaction, P = 0.01). Lambs fed LF had a lower cecal pH compared to those fed HF (P < 0.01). Ruminal Jsm-urea was unaffected by diet. Duodenal Jsm-urea was greater in lambs fed HF compared to LF (77.5 vs. 57.2 nmol/(cm2 × h); P < 0.01). There were positive correlations between Jsm-urea and serosal-to-mucosal mannitol flux (Jsm-mannitol) in duodenal (r = 0.88; P < 0.01) and cecal (r = 0.93; P < 0.01) epithelia. Lambs fed LF diets had increased mRNA expression of AQP-3 (1.21 vs. 0.90; P = 0.03) in ruminal epithelia and tended to have greater mRNA expression of AQP-3 (1.27 vs. 0.99; P < 0.10) in duodenal epithelia compared to lambs fed HF diets. Expression of UT-B mRNA in ruminal, duodenal, and cecal epithelia was largely unaffected by dietary treatment, except that cecal UT-B expression tended to be greater in lambs fed HF diets (0.95 vs. 0.71; P < 0.10) compared to lambs fed LF diets. The results presented in this thesis suggest that the provision of highly digestible diets improves N retention for anabolic usage and shifts urea-N excretion from the urine to the feces by enhancing urea recycling to the GIT. This shift in urea excretion can result in more stable forms of N losses, yielding an environmental benefit. Provision of LF diets also increased expression of AQP-3 in the ruminal and duodenal epithelia, providing insight into the molecular mechanisms associated with Jsm-urea in both ruminal and post-ruminal regions
Evaluation of corn and barley varieties in extensive winter grazing systems for beef calves
No full textTwo experiments were conducted to determine the suitability of whole plant corn as an alternative forage to whole plant barley for winter grazing and the subsequent effect of extensive winter grazing systems on performance and carcass characteristics of beef steers during feedlot finishing. Experiment 1 evaluated the in vitro digestibility of dry matter (IVDMD) and neutral detergent fibre (IVNDFD) of whole plant corn (COR), whole plant barley (BAR) and processed barley hay (CON) collected on October and February sampling dates over 2 yrs. COR forage had similar (P>0.05) IVDMD and IVNDF to both CON or BAR forage. The IVDMD and IVNDFD also remained similar (P>0.05) between the October and February sampling date for COR and BAR forages and processed barley hay. Experiment 2 evaluated the effects of grazing either swathed whole plant barley, standing whole plant corn, or drylot fed barley hay on forage quality, estimated intake, calf performance and backgrounding production costs over 2 years. In each year, 120 spring born Angus calves (263.3 ± 5 kg; 169 d of age) were fall weaned, stratified by body weight and randomly allocated to 1 of 3 replicated (n = 2) backgrounding systems: 1) field grazing standing whole plant corn (COR); 2) field grazing swathed whole plant barley (BAR); or 3) dry lot (CON) bunk fed processed barley hay. Calves fed COR and BAR were limit grazed in 4-ha paddocks for a 3-d grazing period using electric fencing for an average of 97 d over 2 yr, with all calves receiving a pelleted supplement (78% TDN, 16% CP) daily at 0.8% BW. A randomized complete block design (RCBD) was used to analyze crop yield, crop quality, dry matter intake (DMI), body weight (BW), average daily gain (ADG), total system cost and cost of gain (COG) over the 2 yr trial. Forage samples were collected every 21 d to determine forage quality. Protein content was greater (P<0.01) for CON (11.1%) compared to BAR and COR forage (10.1 and 7.9%, respectively). Neutral detergent fibre was greater (P=0.03) for BAR (63.3%) compared to CON (60.3%), while COR forage (62.9%) was not different (P>0.05) from either CON or BAR forage. Acid detergent fibre was not different (P>0.05) between the 3 forage types. Total digestible nutrients and net energy for gain were greater (P<0.01) for the COR forage (62.3% and 0.36 Mcal/d, respectively) compared to CON (57.8% and 0.30 Mcal/d, respectively) and BAR (59.0% and 0.32 Mcal/d, respectively). Calcium was greater (P<0.01) for CON and BAR (0.39 and 0.37%) compared to COR (0.20%) forage. Phosphorus content was greater (P<0.01) for CON (0.27%) then BAR (0.23%) and COR (0.20%) forage. There was no difference (P>0.05) in DMI, BW, ADG or COG between the 3 backgrounding systems. Total cost of production was greatest (P<0.05) for CON calves (/calf/day). Net return was greatest for COR and BAR calves (65.03 and 61.60 -28.85/hd). After backgrounding, replicates of calves were divided into 2 groups and placed in a feedlot each year of the trial. Calves were fed a barley silage based diet with either barley or corn grain for 203 d to a weight of 667.8 ± 5 kg, at which point they were slaughtered and carcass data was collected. A RCBD split plot was used to analyze DMI, BW, ADG, dressing %, hot carcass weight (HCW), ribeye area, and marbling score while quality and yield grade data were analyzed using the GLIMMIX macro with a binomial error structure and logit data transformation. Dressing % was greatest for both COR and CON steers fed the corn grain diet (58.9%) and HCW was greatest (P<0.05) for COR steers fed a corn grain diet (397.5 kg). There was no difference (P>0.05) in BW, DMI, ADG, yield grade or carcass characteristics among systems, suggesting that backgrounding calves by field grazing either standing whole plant corn or swathed barley is a viable option to decrease winter feeding costs without having an effect on finishing performance
Effects of the Amount of Concentrate Offered in an Automated Milking System on dry matter intake, Milk Yield, Milk Composition, Ruminal fermentation, and Behaviour of Primiparous Holstein Cows Fed Iso-Caloric Diets
No full textThe objective of this study was to determine if the quantity of concentrate provided in an automated milking system (AMS) affects dry matter intake (DMI), attendance to the AMS, milk and milk component yield, feeding behaviour, cow activity and ruminal fermentation of lactating dairy cows fed iso-caloric diets. Eight ruminally-cannulated primiparous Holstein cows were used in a replicated 4 × 4 Latin square design with 28-d periods. Cows were housed in a free-stall facility with a guided-traffic (feed-first) flow barn-design. Cows were offered 0.5, 2.0, 3.5, or 5.0 kg/d DM of pellet in the AMS, with an equivalent reduction of the same pellet in the partial mixed ration (PMR). Day 21 to 24 of each treatment period were used for DMI, milking performance, behaviour, and ruminal pH determination, while d 25 to 28 were used for ruminal short-chain fatty acid (SCFA) and ammonia concentrations, as well as total tract digestibility. As imposed, consumption of AMS pellet linearly increased (P < 0.01), equating to 0.50, 2.00, 3.49, and 4.93 kg/d. Correspondingly, the standard deviation in AMS pellet intake among days linearly increased from 0.06 to 0.85 kg/d as the quantity of concentrate in the AMS increased from 0.5 to 5.0 kg (P < 0.01). The PMR DMI decreased linearly with increasing AMS concentrate allocation (P < 0.01), but total DMI (PMR + AMS concentrate) was not affected (25.3 kg/d, P = 0.40). As AMS concentrate allocation increased, the selection against particles retained on an 18-mm sieve linearly increased (P = 0.02) and selection against particles retained on the bottom pan decreased (P < 0.01). Milking frequency (3.22 milkings/d, P = 0.82), milk yield (37.5 kg/d, P = 0.59), milk fat yield (1.43 kg/d, P = 0.46), and milk protein yield (1.22 kg/d, P = 0.42) were not affected; however, milk urea nitrogen concentration decreased linearly with increasing AMS concentrate (P = 0.02). Ruminal pH averaged 6.18 and was not affected by AMS concentrate (P = 0.62). Total ruminal SCFA concentration was greatest when 3.5 kg of concentrate was allocated in the AMS and ruminal ammonia decreased linearly with increasing AMS concentrate (P = 0.01). Time spent lying, the number of lying bouts, and average bout duration were not affected by treatment (P ≥ 0.11). These data indicate that increasing the quantity of concentrate in the AMS increases daily variability in AMS concentrate intake while decreasing PMR intake, and increasing AMS pellet provision, under isocaloric dietary settings, is not likely to affect voluntary visits to the AMS, milk and milk component yield, or ruminal fermentation
Kinetic and spectroscopic characterization of the native and inhibitor bound forms of the Lactobacillus plantarum manganese catalase and related proteins.
No full textManganese catalase is a dinuclear Mn enzyme which cycles between the Mn(II)/Mn(II) and Mn(III)/Mn(III) redox states while performing hydrogen peroxide disproportionation. X-ray absorption (XAS) data for the Mn(II)/Mn(II) catalase were compared to data for inorganic Mn models and for the proteins arginase, Mn substituted ribonucleotide reductase and hemerythrin, in order to characterize the role of metal-ligand structure in catalase activity. All four proteins have similar oxygen and nitrogen based Mn-nearest neighbor ligand environments, although the distribution of ligands is such that there are two resolvable shells (Mn-O and Mn-N) in the catalase and hemerythrin. Outer shell carbon XAS scattering places lower limits on the number of bound imidazoles at ca. 4 for hemerythrin, 2 for catalase and 1 for arginase and ribonucleotide reductase, in good agreement with crystallographic data reported by others. Manganese-manganese distances of 3.53 A and 3.39 A were determined for the fluoride inhibited and ornithine + peroxide forms of catalase and arginase, respectively. Fluoride inhibition is pH dependent and can be successfully modeled using a non competitive slow-binding inhibition model (K\sb{i} = 0.4 mM at pH = 7.0). Inhibition is independent of Mn oxidation state. Regardless of starting conditions, the final inhibited Mn(II)/Mn(II)-F enzyme has a structure that is nearly identical to that of the uninhibited Mn(II)/Mn(II) enzyme, except that MnMn scattering intensity increases for the halide bound sample, suggesting an increase in the rigidity of the enzyme's Mn\sb2 core. Azide and cyanide bind to the Mn(III)/Mn(IV) catalase in a pH dependent fashion (azide K\sb{d} = 15 mM at pH = 7.0). XAS and magnetic circular dichroism analyses suggest that the Mn\rm\sb2O\sb2 core goes from a puckered to a more planar structure upon ion binding. Electron spin echo envelope modulation spectra collected on isotopically labeled forms of azide and cyanide show these ions bind at an outer sphere position and induce this conformational change. Based on the combined spectroscopic and kinetic studies, a mechanism has been proposed for the ornithine and peroxide inhibition of arginase and a revised mechanism has been suggested for the Mn catalase. The revised mechanism for the Mn catalase suggests that the enzyme, in it's active states, alternate between Mn\sb2 core structures which are bis-(-CO\sb2\sp-),(-OH\sb2) and bis-(-CO\sb2\sp-),(-OH) bridged in the Mn(II)/Mn(II) and Mn(III)/Mn(III) oxidation states, respectively. In addition, a distal amino acid base assists in catalase by acting as a proton donator and acceptor, as well as stabilizing solvent binding.PhDPhysical chemistryPure SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/129899/2/9635619.pd
WHOLE-BODY UREA KINETICS AND FUNCTIONAL ROLES OF UREA TRANSPORTERS AND AQUAPORINS IN UREA SECRETION INTO THE RUMEN IN SHEEP FED DIETS VARYING IN CRUDE PROTEIN CONTENT AND CORN GRAIN PROCESSING METHOD
No full textThe objectives were to determine the effects of dietary crude protein (CP) content and corn grain processing on serosal-to-mucosal urea flux (Jsm-urea) in ruminal epithelia. Thirty-two Rideau-Arcott lambs were blocked by BW into groups of 4 (i.e., a total of eight blocks) and then randomly allocated within block to 1 of 4 dietary treatments (n = 8) in a 2 × 2 factorial design. Dietary factors were CP content (11% [LP] vs. 16% [HP]) and method of corn grain processing (whole-shelled [WSC] vs. steam-flaked [SFC] corn). Four blocks of animals (n = 4) were used in 4-day continuous infusions of [15N-15N]-urea with concurrent collections of urine and feces to determine whole-body urea kinetics and nitrogen (N) balance. After 23 days of dietary exposure, lambs were killed to collect ruminal epithelia which were mounted in Ussing chambers to determine Jsm-urea. Lambs fed HP had greater N intakes (29.4 vs. 19.1 g/d; P < 0.01) and total N excretion (20.3 vs. 14.5 g/d; P < 0.01) than those fed LP. Endogenous urea-N production (UER) was greater in lambs fed HP compared to those fed LP (29.9 vs. 20.6 g/d; P = 0.02), whereas urea-N secreted into the gut (GER; g/d) and urea-N used for anabolic purposes (UUA; g/d) were similar. Lambs fed LP tended to have greater GER:UER (0.78 vs. 0.66; P = 0.05) and UUA:GER (0.23 vs. 0.13; P = 0.05) ratios, and Jsm-urea (144.7 vs. 116.1 nmol/[cm2 × h]; P = 0.07) compared to those fed HP. Lambs fed SFC had a lower phloretin-insensitive Jsm-urea (87.1 vs. 143.1 nmol/[cm2 × h]; P = 0.02) and tended to have a lower NiCl2-insensitive Jsm-urea (117.4 vs. 178.4 nmol/[cm2 × h]; P = 0.09) compared to those fed WSC, whereas total Jsm-urea and total-insensitive Jsm-urea were similar. Lambs fed SFC tended to have a lower mRNA expression of UT-B (0.89 vs. 1.07; P = 0.08) and AQP-3 (0.90 vs. 1.05; P = 0.07) compared to those fed WSC. These results suggest that urea transport through UT- and AQP-mediated pathways can be upregulated in ruminants by feeding more ruminally-fermentable carbohydrates (manipulated via grain processing)
WHOLE-BODY UREA KINETICS AND FUNCTIONAL ROLES OF UREA TRANSPORTERS AND AQUAPORINS IN UREA SECRETION INTO THE RUMEN IN SHEEP FED DIETS VARYING IN CRUDE PROTEIN CONTENT AND CORN GRAIN PROCESSING METHOD
No full textThe objectives were to determine the effects of dietary crude protein (CP) content and corn grain processing on serosal-to-mucosal urea flux (Jsm-urea) in ruminal epithelia. Thirty-two Rideau-Arcott lambs were blocked by BW into groups of 4 (i.e., a total of eight blocks) and then randomly allocated within block to 1 of 4 dietary treatments (n = 8) in a 2 × 2 factorial design. Dietary factors were CP content (11% [LP] vs. 16% [HP]) and method of corn grain processing (whole-shelled [WSC] vs. steam-flaked [SFC] corn). Four blocks of animals (n = 4) were used in 4-day continuous infusions of [15N-15N]-urea with concurrent collections of urine and feces to determine whole-body urea kinetics and nitrogen (N) balance. After 23 days of dietary exposure, lambs were killed to collect ruminal epithelia which were mounted in Ussing chambers to determine Jsm-urea. Lambs fed HP had greater N intakes (29.4 vs. 19.1 g/d; P < 0.01) and total N excretion (20.3 vs. 14.5 g/d; P < 0.01) than those fed LP. Endogenous urea-N production (UER) was greater in lambs fed HP compared to those fed LP (29.9 vs. 20.6 g/d; P = 0.02), whereas urea-N secreted into the gut (GER; g/d) and urea-N used for anabolic purposes (UUA; g/d) were similar. Lambs fed LP tended to have greater GER:UER (0.78 vs. 0.66; P = 0.05) and UUA:GER (0.23 vs. 0.13; P = 0.05) ratios, and Jsm-urea (144.7 vs. 116.1 nmol/[cm2 × h]; P = 0.07) compared to those fed HP. Lambs fed SFC had a lower phloretin-insensitive Jsm-urea (87.1 vs. 143.1 nmol/[cm2 × h]; P = 0.02) and tended to have a lower NiCl2-insensitive Jsm-urea (117.4 vs. 178.4 nmol/[cm2 × h]; P = 0.09) compared to those fed WSC, whereas total Jsm-urea and total-insensitive Jsm-urea were similar. Lambs fed SFC tended to have a lower mRNA expression of UT-B (0.89 vs. 1.07; P = 0.08) and AQP-3 (0.90 vs. 1.05; P = 0.07) compared to those fed WSC. These results suggest that urea transport through UT- and AQP-mediated pathways can be upregulated in ruminants by feeding more ruminally-fermentable carbohydrates (manipulated via grain processing)
The effects of extruding wheat dried distillers grains with solubles with peas or canola meal on ruminal fermentation, microbial protein synthesis, nutrient digestion and milk production in Holstein dairy cows
No full textThe objective of this study was to examine the effects of feeding extruded and non-extruded mixtures of wheat dried distillers grains with solubles with peas (WP) or canola meal (WC) on ruminal fermentation, total tract nutrient digestion and milk production in dairy cows. Eight dairy cows (712 ± 54 kg body weight; 90 ± 31 days-in-milk at the beginning of the experiment) were used in a replicated 4 × 4 Latin square design (28-d periods) with a 2 × 2 factorial arrangement of dietary treatments. Four cows in one Latin square were fitted with rumen cannulas for the measurement of ruminal fermentation characteristics. Treatment diets contained either WP or WC combinations fed in an extruded or non-extruded form (16% of DMI). Diets were isonitrogenous (17.1% crude protein; CP) and contained approximately 53% concentrate and 47% forage (DM basis). Dietary treatment had no significant effect on DMI (P > 0.10). Starch intake was higher for cows fed extruded diets compared to those fed non-extruded diets (P = 0.028) and was also higher for cows fed WP compared to those fed WC (P = 0.042). Cows fed extruded diets had higher apparent ruminal digestion of DM (P = 0.02) and a tendency (P = 0.05) for a higher OM apparently digested in the rumen compared to those fed non-extruded diets. Total tract digestibilities of organic matter (P < 0.01), CP (P < 0.01), ether extract (P < 0.01) and starch (P = 0.047) were higher for cows fed extruded diets compared to those fed non-extruded diets. Total tract digestibility of ether extract was lower (P = 0.011) but digestibility of starch was higher (P < 0.01) and CP digestibility tended to be higher (P = 0.08) for cows fed WP compared to those fed WC. Fecal N excretion was lower in cows fed extruded diets compared to those fed non-extruded diets (P < 0.01), but there was no difference in N retention, productive N, RDP or RUP between diets (P > 0.10). Ruminal pH was higher for cows fed non-extruded WC compared to those fed extruded WC, but there was no difference between WP diets (interaction; P = 0.047). Ruminal acetate displayed the opposite interaction where concentration was highest for cows fed extruded WC and lowest for those fed non-extruded WC but there was no difference between WP diets (interaction; P = 0.019). Ruminal ammonia-N concentration tended to be higher for cows fed WC compared to those fed WP (P = 0.06). Ruminal propionate concentration was higher for cows fed extruded diets compare to those fed non-extruded diets (P = 0.026). Ruminal isobutyrate concentration was higher for cows fed WC compared to those fed WP (P < 0.01). Ruminal butyrate (P < 0.01) and isovalerate (P < 0.01) concentrations were higher for cows fed extruded WC compared to those fed non-extruded WC, but concentrations decreased for cows fed extruded WP compared to those fed non-extruded WP. Plasma glucose concentration was higher for cows fed WC compared to those fed WP but concentration was highest for cows fed extruded WC but lowest for cows fed extruded WP (interaction; P < 0.01). Milk protein yield (P = 0.047) was higher and milk yield tended to be higher (P = 0.06) for cows fed WP compared to those fed WC diets. Milk protein content was not affected by diet; however, milk fat content (P = 0.04) and MUN (P = 0.011) were lower, whereas milk yield (P = 0.030), 3.5% fat corrected milk yield (P = 0.027), milk fat yield (P = 0.027), lactose content (P = 0.011) and lactose yield (P < 0.01) were higher in cows fed the extruded diets compared to those fed non-extruded diets. In summary, these results indicate that extrusion had positive effects on overall milk production and total tract nutrient digestion
THE EFFECTS OF PARTIAL REPLACEMENT OF BARLEY STARCH WITH SUGARS ON RUMINAL FUNCTION, OMASAL NUTRIENT FLOW, UREA-N RECYCLING, AND PRODUCTION PERFORMANCE IN DAIRY COWS.
No full textA considerable number of studies have shown that the partial substitution of corn starch with sugars is beneficial in terms of improving dry matter (DM) intake, milk yield and efficiency of nitrogen utilization in dairy cows without putting them at risk of developing ruminal acidosis; however, research with dairy cows fed barley-based diets is limited. The objective of this study was to determine the effects of partial replacement of barley starch with dried whey permeate (DWP; contained 83% lactose) on ruminal acidosis, transport of short-chain fatty acids (SCFA) across the ruminal wall, urea-N recycling to the digestive tract, ruminal microbial protein production, omasal nutrient flow, and production performance in dairy cows. Eight Holstein cows (97 ± 10 days-in-milk; 733 ± 63 kg body weight) were used in a replicated 4 × 4 Latin square design with 28-d periods (18 d of adaptation and 10 d of measurements). Four cows in one Latin square were ruminally-cannulated to facilitate ruminal fluid and omasal digesta sampling. Cows were fed a barley-based diet (3.5% total sugar [TS]; control), or diets that contained 6.5, 9.5 or 12.5% TS (DM basis). Diets were isonitrogenous (17.3% crude protein) and contained 24.3, 22.2, 21.2, and 19.1% starch for the control, 6.5, 9.5 or 12.5% TS diets, respectively. Dietary inclusion of DWP did not affect DM intake (mean = 26.6 kg/d) and milk yield (mean = 34.9 kg/d); however, milk lactose content quadratically changed (4.40, 4.42, 4.46, and 4.40% for the control, 6.5, 9.5, and 12.5% TS diets, respectively) across diets. Ruminal concentration of acetate, propionate, and total SCFA were not affected by dietary treatment; however, ruminal concentration of butyrate was cubically increased (12.8, 13.0, 14.1, and 14.9 mM for the control, 6.5, 9.5, and 12.5% TS diets, respectively) as dietary content of DWP increased. When expressed as absolute (mmol/h) or fractional (%/h) rates of absorption, the rates of acetate, propionate, and total SCFA absorption across the ruminal wall were cubically decreased by the 9.5% TS diet compared to control and 6.5% TS diets, then increased by the 12.5% TS diet compared to the 9.5% TS diet. The rate of butyrate absorption across the ruminal epithelium tended to change cubically as level of dietary DWP increased. For individual and total SCFA, Cl--insensitive and Cl--competitive rates of absorption across the ruminal wall were largely unaffected by dietary treatment, except that the Cl--competitive absorption of propionate tended to be cubically altered as dietary content of DWP increased. Mean ruminal pH tended to change quadratically (6.32, 6.31, 6.34, and 6.22 for the control, 6.5, 9.5, and 12.5% TS diets, respectively) as dietary content of DWP increased. Dietary addition of DWP cubically changed the ruminal concentration of ammonia-N (NH3-N; 12.1, 12.3, 10.9, and 9.40 mg/dL for the control, 6.5, 9.5, and 12.5% TS diets, respectively). The omasal flow of bacterial N quadratically changed (513, 517, 539, and 468 g/d for the control, 6.5, 9.5, and 12.5% TS diets, respectively) as dietary content of DWP increased. The ruminal digestibility of DM linearly increased as dietary content of DWP increased, but total-tract DM digestibility was unchanged. The ruminal and total-tract digestibilities of water-soluble carbohydrates (WSC) cubically increased as dietary content of DWP increased. There were no dietary effects on ruminal and total-tract digestibility of neutral detergent fiber and acid detergent fiber. Total urinary N excretion quadratically changed (223, 255, 238, and 223 g/d for the control, 6.5, 9.5, and 12.5% TS diets, respectively), and fecal N excretion linearly increased as dietary content of DWP increased; however, productive N was unaffected by dietary TS content. Quadratic changes were observed in absolute amounts of endogenous production of urea-N (i.e., UER; 467, 531, 522, and 472 g/d for the control, 6.5, 9.5, and 12.5% TS diets, respectively). Although the absolute amount of urea-N transferred to the gastrointestinal tract (i.e., GER; 307, 354, 340, and 309 g/d for the control, 6.5, 9.5, and 12.5% TS diets, respectively) tended to change quadratically, there was no difference across diets when GER was expressed as a proportion of UER. Increasing dietary TS by adding DWP tended to change microbial utilization of recycled N in a cubic manner (15.8, 13.7, 15.8, and 15.9 % for the control, 6.5, 9.5, and 12.5% TS diets, respectively); however, recycled N that was utilized for anabolism (UUA) was unaffected by diets. These results suggest that the partial replacement of barley starch with DWP does not affect the production performance of dairy cows; however, dietary TS concentration of 9.5% potentially improve ruminal N efficiency by decreasing NH3-N concentration and increasing omasal microbial N flow
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