Histopathological studies of the heart in three lines of broiler chickens.

The aim of this study was to analyse the morphological lesion pattern of the heart of broiler chickens (Cobb 500, Hubbard F15 and Ross 308) during fattening with no clinical signs of disease and to determine the most susceptible period for the occurrence of morphological lesions. The most frequently diagnosed lesions in each genetic line were degeneration of the fibres with vacuolation, congestion of cardiac muscle, oedema and vacuolisation of the Purkinje cells. The highest numbers of morphological lesions were observed on d 38, 31 and 10 of life. The lesions were most numerous in the septum, followed by the left and right ventricles. Ischaemic cardiomyocytes were also most numerous on d 38 of life and in the left ventricle. Overload of cardiac muscle, prolonged hypoxia and increasing body weight on d 38 are the likely reasons for the largest number of lesions and ischaemic fibres, which may lead to heart failure.

Aging implications on fresh muscle traits of Certified Angus Beef steaks.

Vacuum-packaged Certified Angus Beef (CAB) subprimals ( = 72) that included the longissimus thoracis (LT), longissimus lumborum (LL), gluteus medius (GM), and infraspinatus (IF) muscles were purchased from a major beef packing facility. Subprimals were allocated to 1 of 3 aging periods (14, 28, or 42 d) and aged at 2°C. After aging, 5 steaks were cut from each subprimal and assigned to pH, water-holding capacity, Warner-Bratzler shear force (WBSF), cooked color, cooking yield, cooking loss, and sensory panel analysis. Infraspinatus steaks were more tender ( < 0.05) than all other steaks, and subprimals aged 14 d had greater ( < 0.05) WBSF values than the other 2 aging periods, regardless of muscle. Water-holding capacity and cook yield were greater ( < 0.05) for LL and LT than IF and GM steaks, whereas purge loss was greater ( < 0.05) for IF and GM than LL and LT steaks. Throughout the aging periods, pH declined for all muscle groups, with IF steaks having the greatest ( < 0.05) pH values among all muscles. Among IF steaks, sensory evaluations of all attributes did not ( ≥ 0.26) differ across aging periods; yet among LT steaks, consumers rated those aged 14 d greater ( < 0.05) in overall impression than LT steaks aged 28 and 42 d. Among LT steaks, those aged 14 d received greater ( < 0.05) flavor ratings than LT steaks subjected to longer aging periods, and LT steaks aged 14 d received the greatest ( < 0.05) overall impression, with consumers giving greater ( < 0.05) overall impression scores to LT steaks aged 42 d over those aged 28 d. Aging period had no effect ( ≥ 0.017) on consumer ratings for flavor, tenderness, juiciness, or overall impression of LL steaks. Among GM steaks, consumers rated steaks aged 14 and 28 d more ( < 0.05) flavorful than those aged 42 d, and consumer ratings for overall impression were greater ( < 0.05) for GM steaks aged 28 d than for GM steaks aged 42 d; however, consumers failed ( = 0.035) to note differences in tenderness scores of GM steaks in response to aging period. Furthermore, consumers indicated a greater ( < 0.05) likelihood to purchase LT steaks aged 14 d over LT steaks aged 28 d, LL steaks aged 42 d over LL steaks aged 14 d, and GM steaks aged 14 and 28 d over GM steaks aged 42 d. These results indicate that consumers struggled to identify steak flavor attributes and suggest that the benefit of aging for premium beef products does not offer a tremendous sensory advantage to the consumer.

Effects of Juniperus species and stage of maturity on nutritional, in vitro digestibility, and plant secondary compound characteristics.

Rising feed costs and recurring feed shortages necessitate the investigation into alternative and underutilized feed resources. Nutritional characteristics of species are either unknown or limited to leaves and ground material from small stems. Therefore, the objective was to quantify nutritional characteristics, 48-h true IVDMD (tIVDMD), microbial gas production, and secondary compound characteristics of entire woody plant material of 4 species-, , , and -at immature and mature stages of growth. Immature plants had greater CP concentrations and lower NDF concentrations ( < 0.001) than mature plants regardless of species. Mature plants also had greater ( < 0.001) concentrations of ADF compared with immature plants with the exception of . In general, immature , , and had greater ( < 0.02) tIVDMD and total 48-h and asymptotic gas production than mature plants. Immature and plants were more digested (tIVDMD; < 0.001) than immature and , but tIVDMD did not differ in mature plant material across species. Condensed tannins (CT) were greater ( < 0.001) in immature and than mature plants; differences in CT concentrations among immature species were also detected ( < 0.04). Volatile oil yields were similar across maturity and species with 1 exception: immature yielded more ( < 0.02) volatile oil than mature material. Volatile oil composition across species varied and contained a range of 65 to 70 terpene compounds. The dominant terpenes across species were generally greater ( < 0.05) in immature vs. mature plant material with the exception of . Labdane acids were negligible in , , and and greater in ( < 0.001). Ground material from mature juniper species, although inferior in nutritional quality compared with immature plants, is comparable to traditional low-quality roughage ingredients. Given that has been successfully fed in lamb feedlot diets, the similarities of , and suggest that all three species have potential to be effective roughage ingredients.

Effect of replacing alfalfa with panicled-tick clover or sericea lespedeza in corn-alfalfa-based substrates on in vitro ruminal methane production.

Methane emissions from ruminant livestock contribute to total anthropogenic greenhouse gas emissions and reduce metabolizable energy intake by the animal. Condensed tannins (CT) are polyphenolic plant secondary compounds commonly produced by some perennial forage legumes that characteristically bind to protein, carbohydrates, and minerals. The degree to which CT may affect ruminant nutrition depends upon the concentration, structural composition, and biological activity of the CT. The objective of our experiment was to determine the effect of replacing alfalfa in a corn-alfalfa-based substrate with a legume containing CT on in vitro CH4 production and the dynamics of fermentation using an in vitro gas production technique. All fermented substrates contained 50% ground corn as the energy concentrate portion, whereas the forage portion (50%) of each diet was comprised of alfalfa (control) or some combination of alfalfa and sericea lespedeza (SL) or panicled-tick clover (PTC). Our treatments consisted of PTC or SL 15, 30, and 45, which corresponded with 15, 30, or 45% replacement of the diet (alfalfa component) with either PTC or SL. Substrates containing 45% PTC or SL reduced in vitro CH4 production. Treatments did not affect total gas production as compared with that of the control. Replacement of alfalfa with SL or PTC increased fermentable organic matter (FOM). The PTC treatment increased FOM by as much as 1.8% at the 45% replacement level, whereas FOM of SL 45 was increased by less than 1%. The replacement of alfalfa with PTC increased substrate nutritive value greater than replacement with SL. There were no correlations between any physicochemical constituent of the substrates and CH4 production. A combination of factors associated with the inclusion of PTC and SL contributed to the in vitro CH4 production, and CT in these forages was likely a major contributing factor. Further confirmation of these results on in situ or in vivo animal systems is required. If proven effective in an in vivo production scenario, replacement of commonly fed non-CT-containing legumes, such as alfalfa, with legumes containing CT might be a viable method to decrease the effect of animal agriculture on greenhouse gas production.

Effects of wet corn distillers grains with solubles on visceral organ mass, trace mineral status, and polioencephalomalacia biomarkers of individually-fed cattle.

Twenty-four steers (initial BW = 385 ± 1.1 kg) were blocked by BW and randomly assigned to 3 dietary treatments (0, 30, or 60% wet distillers grains with solubles [WDGS]; DM basis) and were fed individually to determine the effect of WDGS on live growth and carcass performance, visceral organ mass, trace mineral status, and polioencephalomalacia biomarkers. Steers were slaughtered at 125, 150, 164, and 192 d (2 blocks/slaughter date) when external fat depth was approximately 1.3 cm based on visual appraisal. Steers fed 30% WDGS had greater DMI than those fed 0 or 60% WDGS (P < 0.05), and steers fed 60% WDGS had the lowest carcass-adjusted ADG (P < 0.09) of the 3 treatments. Nonetheless, WDGS concentration did not alter feed efficiency (P > 0.41) on either live or carcass-adjusted basis. Steers fed 30% WDGS had greater liver S and Mn concentrations (DM basis) and lower liver Fe concentrations than control steers (P < 0.10; initial values used as a covariate), and feeding 60% WDGS decreased liver Cu and increased liver Fe (P < 0.10) compared with feeding 30% WDGS. Cytochrome c oxidase (COX) activity in brain tissue tended to be decreased with 60 vs. 30% WDGS (P = 0.12), and COX activity decreased linearly (P = 0.06) in lung tissue as dietary WDGS concentration increased. Likewise, gut fill linearly increased (P = 0.01) with increasing WDGS concentration. Feeding 30% WDGS increased fractional mass (g/kg of empty BW) of the small intestine (P < 0.10) compared with controls, whereas 60% WDGS increased fractional kidney mass (P < 0.10) compared with 30% WDGS. Overall, results suggest that gut fill, Cu status, and COX activity seem to be compromised by WDGS when fed at 60% of diet DM in diets based on steam-flaked corn, which suggests a greater susceptibility to polioencephalomalacia.

Effect of molecular weight and concentration of legume condensed tannins on in vitro larval migration inhibition of Haemonchus contortus.

The effect of molecular weight of condensed tannins (CT) from a variety of warm-season perennial legumes commonly consumed by sheep and goats on anthelmintic activity has not been previously explored. The objectives of this study were to determine if molecular weight of CT from warm-season perennial legumes could predict the biological activity of CT relative to anthelmintic activity against ivermectin resistant L3 stage Haemonchus contortus (HC) using a larval migration inhibition (LMI) assay. A second objective was to determine if CT from warm-season perennial legumes possess anthelmintic properties against L3 stage (HC). Lespedeza stuevei had the greatest concentration of total condensed tannin (TCT; 11.7%), whereas, with the exception of Arachis glabrata, a CT-free negative control, Leucaena retusa had the least TCT (3.3%). Weight-average molecular weight of CT ranged from 552 Da for L. stuevei to 1483 Da for Lespedeza cuneata. The treatments demonstrating the greatest percent LMI were L. retusa, L. stuevei and Acacia angustissima var. hirta (65.4%, 63.1% and 42.2%, respectively). The ivermectin treatment had the smallest percent LMI (12.5%) against ivermectin resistant L3 HC. There was a weak correlation (R(2)=0.34; P=0.05) between CT MW and percent LMI, suggesting that molecular weight of CT is a weak contributing factor to CT biological activity as it relates to LMI of L3 stage HC. L. stuevei, L. retusa and A. angustissima var. hirta STP5 warrant further evaluation of anthelmintic properties in vivo.

Off-host collection methods of the Otobius megnini (Acari: Argasidae).

Otobius megnini (Dugès), often referred to as the spinose ear tick, is a one-host tick infesting the ear canal of a variety of ungulate species. The objective of this study was to develop sampling methods for collecting free-living stages of O. megnini and to collect preliminary data on habitat distribution. Sampling occurred during 2010 and 2011 at Fossil Rim Wildlife Center (FRWC) near Glen Rose, TX, where tick presence has been observed in the ears of a variety of ungulates. To sample for nonfeeding adult stage presence, a debris-filtering method was developed using screens of varying gauges. To sample host-seeking larval-stage tick presence, a carbon dioxide (CO2) trap was developed using compressed CO2 released through tubing along with cotton fabric used for tick attachment. Both methods proved successful with adults and larvae collected from animal shelters, with larvae also collected from oak leaf litter away from any structure. Locating both life stages off the host is the first crucial step toward the management of this tick species at facilities such as FRWC.

Effect of using redberry juniper (Juniperus pinchotii) to reduce Haemonchus contortus in vitro motility and increase ivermectin efficacy.

A modified larval migration inhibition assay was used to determine if redberry juniper (Juniperus pinchotii Sudw.) can reduce Haemonchus contortus in vitro motility and increase ivermectin (IVM) efficacy. Ruminal fluid was mixed with buffer solution and either no material (CNTL) or Tifton 85 Bermudagrass hay (T85), dried juniper (DRY), fresh juniper (FRE), or distilled juniper terpenoid oil (OIL) to make treatment solutions and anaerobically incubated for 16 h. For Trial 1, larvae were incubated in CNTL, T85, DRY, or IVM. During Trial 2, larvae were incubated in CNTL, DRY, FRE, or OIL for 4h. Trials 3 (CNTL or OIL) and 4 (CNTL, DRY or FRE) evaluated larvae after incubation in treatment solution for 2h, then incubated an additional 2h in various IVM doses (0, 0.1, 1, 3, and 6 µg/mL IVM) and placed onto a screen. Larvae that passed through the 20-µm screen within a 96-well plate were considered motile. Larvae incubated in CNTL or T85 had similar (P=0.12) motility, but larvae incubated in DRY were less (P<0.02) motile than larvae incubated in CNTL or T85 (Trial 1). During Trial 2, adding DRY, FRE, or OIL reduced (P<0.001) larval motility as compared to CNTL. A treatment×IVM dose interaction (P=0.02) was observed during Trial 3, due to OIL unexpectedly decreasing IMV efficacy at IVM concentrations of 1 (P=0.07), 3, and 6 (P<0.002)µg/mL. No treatment×IVM dose interaction (P=0.57) was observed during Trial 4, but larvae incubated in DRY had less (P<0.004) total motility than larvae incubated in CNTL or FRE. Juniper forage material reduced in vitro H. contortus larval motility, but IVM efficacy was increased only by initially incubating larvae in DRY.

Effect of supplemental sericea lespedeza leaf meal pellets on gastrointestinal nematode infection in grazing goats.

Feeding sun-dried sericea lespedeza [SL; Lespedeza cuneata (Dum-Cours.) G. Don.] reduces gastrointestinal nematode (GIN) infection in goats fed in confinement, but effects of this forage when fed as a supplement to goats on pasture are unclear. A study was completed in which supplemental feeds (75 and 95% SL leaf meal pellets and a commercial pellet, all fed at 0.91 kg/head/day) were offered to thirty growing male Spanish goats (9 months old, 20.6 ± 2.8 kg, 10/treatment) grazing perennial warm-season grass pastures in Fort Valley, GA, from September to November, 2010. Fecal and blood samples were taken from individual animals weekly to determine fecal egg count (FEC) and packed cell volume (PCV), respectively, and animal weights were recorded at the start and end of the trial. After 11 weeks grazing, animals were slaughtered for recovery, counting, and speciation of adult GIN from the abomasum and small intestines. There was no difference in FEC between goats fed the 75 and 95% SL leaf meal pellets, but both groups had lower (P<0.05) FEC than the goats fed the commercial pellets from days 35 to 77. The PCV values were not affected by the dietary treatments. Animal gain per day averaged 102.0, 77.2, and 53.3g for goats fed 95% SL, commercial, and 75% SL pellets, respectively (P<0.05). The 95% SL leaf meal pellet goats had 93.0 and 47.3% fewer (P<0.05) total (male+female) adult Haemonchus contortus and Teladorsagia circumcincta, respectively, than control animals, while only male H. contortus were lower (47.6%; P<0.05) in 75% SL-fed goats compared with commercial pellet-fed animals. Feeding supplemental SL leaf meal pellets improved animal performance (95% SL pellets) and reduced worm burdens (75 and 95% SL pellets) in young grazing goats and is a useful tool for natural GIN control in small ruminants.

Phosphate transporter expression in Holstein cows.

Phosphorus nutrition in cattle is increasingly becoming an important topic because excess dietary P is excreted in manure and can be washed into surface water, causing increased algal growth and eutrophication. However, little is known about the mechanism or regulation of P absorption in dairy cattle. Phosphorus transporters have been characterized in other species and homologous genes have been found to be expressed in bovine cell cultures. However, no other information is available regarding the active transport of phosphate in the digestive tract of cattle. The objective of this study was to determine the patterns of expression of a known phosphate transporter, NaPi-IIb, in 4 sections of the small intestine of Holstein cows. Ribonucleic acid was isolated from the duodenal, proximal jejunal, distal jejunal, and ileal mucosa of 20 Holstein cows. Relative amounts of NaPi-IIb mRNA expression were determined using real-time reverse-transcription PCR. Expression of NaPi-IIb was highest in the 2 distal sections and almost absent in the proximal sections. Expression did not differ between the 2 proximal sections or the 2 distal sections. These data suggest that a Na+-dependent secondary active P transport system is not responsible for P absorption in the proximal portion of the bovine small intestine, whereas it does contribute to the P absorbed in the distal sections of the bovine small intestine.

Maturity of coastal bermudagrass and alfalfa affects ruminal in situ and total tract dry matter and phosphorus disappearance in cannulated steers.

Variability of phosphorus (P) availability among forage species and plant maturity is largely ignored when formulating ruminant diets. To determine if variability in P availability changes with forage species and/or maturity, ruminal in situ and total (ruminal+post-ruminal) dry matter (DM) and phosphorus disappearance (PD) from alfalfa (ALF; Medicago sativa) and coastal bermudagrass (CB; Cynodon dactylon) harvested at four stages of maturity was measured in cattle. Forages were hand clipped at 14, 21, 28 and 35 days after first cutting. Ruminal in situ DM disappearance (DMD) and PD were measured after 24 h ruminal incubation in Dacron bags. Total tract DMD and PD were measured using the mobile nylon bag technique. Disappearance of DM and P were greater (p≤0.05) in the rumen than post-rumen for both species regardless of maturity; however, 80 g PD/kg DM in 35-day ALF (9% of total PD) and 224 g PD/kg of 35-day CB (38% of total PD) occurred post ruminally. Alfalfa DM disappeared to a greater (p ≤ 0.05) extent than CB and showed 5% greater total tract PD at 14 days and 13% more at 35 days compared to the grass. Alfalfa total tract PD decreased (p ≤ 0.05) 5.4% from 14- to 35-day maturity while the decrease was far greater for CB, 12.4%. Results from this study indicate that ruminant nutritionists should take into account forage species and maturity when calculating PD in diets; these details can be used to aid in formulating more precise rations that reduce fecal-phosphorus excretion into the environment.

Ruminal and total tract phosphorus release from feedstuffs in cattle measured using the mobile nylon bag technique.

Phosphorus (P) excretion in manure is a concern for dairy and beef producers. Excess P released into surface water runoff can lead to eutrophication and algal blooms in streams and lakes. One approach to reducing P excretion is to reduce dietary P. Data regarding P release from feedstuffs is limited and more precise formulations based on specific feed P release in the digestive tract may be one way to lower excreted P. In this experiment, the mobile nylon bag technique was used to determine the disappearance of P in corn silage, alfalfa hay, Coastal bermudagrass hay, and Tifton-85 bermudagrass hay in steers after ruminal (24 h), ruminal + pepsin/HCl (rumen + PHCl), and ruminal + pepsin/HCl + intestinal (rumen + PHCl + I) incubation. Ruminal disappearance of P differed (p < 0.05) between feedstuffs and by site of incubation. Total tract (rumen + PHCl + I) P disappearance for corn silage, alfalfa hay, Coastal bermudagrass hay, and Tifton-85 bermudagrass hay were 90.6%, 93.7%, 83.8% and 84.0% respectively. The range in P release (approximately 7%) indicates that considering P availability when balancing rations could have a measurable impact on subsequent P excretion from ruminants. More data concerning P availability as affected by other feed ingredients or plant species, maturity, and/or quality are needed to more accurately define P release from ruminant feeds.

Technical note: assessing the functional capacity of mitochondria isolated from lactating mammary tissue: choose your chelating agent wisely.

Previous work has indicated that respiratory activity of mitochondrial preparations prepared from lactating mammary tissue is often much lower than that of mitochondria isolated from other organs such as the liver. Initial studies in our own laboratory also found that mammary mitochondria prepared from lactating mice had much lower ATP synthesis activity than those isolated from liver tissue obtained from the same animals. In this paper, we describe an improved procedure for obtaining coupled mitochondria from the mammary tissue of lactating mice. Using a high-throughput assay for mitochondrial ATP synthesis, we demonstrated that mammary mitochondria, unlike liver mitochondria, are sensitive to the concentration of bovine serum albumin and to the choice of chelating agent used in the preparation and assay buffers. Mammary mitochondria prepared and assayed in buffers containing 1 mM ethylene glycol-bis-(beta-aminoethyl ether)-N,N' tetraacetic acid (EGTA) and 0.4% bovine serum albumin have a similar ATP synthesis activity as liver mitochondria. In addition, we show that the chelating agent EDTA ablates the ATP synthesis capacity of mammary mitochondria through a mechanism that does not involve the release of cytochrome c. We also demonstrate that these improved isolation and assay procedures are both scalable and applicable to bovine mammary tissue, and we describe optimal conditions for cryopreservation and recovery of functionally active mitochondria. This work will facilitate future studies aimed at determining the importance of mammary mitochondria to milk production.

Chemical form of dietary L-carnitine affects plasma but not tissue carnitine concentrations in male Sprague-Dawley rats.

In Experiment 1, rats (n = 54) were randomly assigned to control or one of the four sources of l-Carnitine supplemented at either 100 or 200 micromol/kg/day and were allowed to acclimate for 14 days. Following a 12-h fast, plasma samples were obtained at 0, 5, 10, 15, 30, 60, 120, 240, 480 and 720 min after l-Carnitine feeding and assayed for free l-Carnitine concentration. Plasma-free l-Carnitine levels were affected by time after treatment intake (p < 0.0001) and l-Carnitine source (p < 0.0001). The time x source interaction was not statistically significant (p = 0.99). In Experiment 2, rats (n = 54) were randomly assigned to control or one of the four sources of l-Carnitine at either 100 or 200 micromol/kg/day and were acclimated as in experiment 1. Rats were sacrificed 120 min after feeding. Samples of liver and skeletal muscle were obtained and assayed for free l-Carnitine concentration. Neither skeletal muscle (p = 0.44) or liver (p = 0.59) tissue concentrations of l-Carnitine were affected by any l-Carnitine source as compared with the control. We conclude that some differences exist in plasma concentrations of free l-Carnitine following ingestion of different chemical forms of l-Carnitine. It is unclear if these differences in the circulating concentration of free l-Carnitine translate into any physiological differences for the animal. In this study, chemical form of l-Carnitine had no effect on skeletal muscle or liver tissue concentrations of l-Carnitine in young male Wistar rats.

Effects of protein and energy supplementation on growth, forage intake, forage digestion and nitrogen balance in meat goat kids.

The objective of this study was to further the understanding of the effects of dietary protein and energy supplements on growth, performance, feed intake and grass forage digestibility in growing meat goat wethers. In Experiment 1, an 18% CP complete goat pellet was offered alone (control diet, C) or added (+), or not, as supplement to three grass hays (coastal bermudagrass, CB; Tifton 85 bermudagrass, T; and sorghum-Sudan grass hay, SS), to Boer-cross wethers (n = 72). The resulting seven diets were offered ad libitum. In Experiment 2, four wether goats in metabolism crates were used in a 4 × 4 Latin square design and fed a SS basal diet ad libitum with treatments consisting of no supplement, supplemental urea (200 mg/kg BW daily), supplemental dextrose (0.2% BW daily), or urea + dextrose (200 mg/kg BW daily and 0.2% BW daily, respectively). In Experiment 1, average daily gain (ADG) were -3.8, -5.0 and -6.6 g/day for goats consuming CB, T and SS, respectively, and 69.2, 61.6 and 58.1 g/day for supplemented CB (CB+), T (T+) and SS (SS+), respectively, as compared to 245.8 g/day for ad libitum access to C. Supplementation in Experiment 1 increased (P < 0.01) ADG for all hays when compared to hay-only diets. In Experiment 2, protein and energy supplementation increased (P < 0.01) nitrogen retention but did not impact diet digestibility. The beneficial effects of supplements in Experiment 1 and the increase in nitrogen retention in Experiment 2 cannot be explained by improvements in ruminal fiber utilization, but could be due to post-ruminal nutrient supply and/or increased ruminal microbial protein synthesis.

Effects of dietary ruminally protected L-carnitine on plasma metabolites in sheep following a sub-lethal ammonia challenge.

In Experiment 1, lambs were randomly assigned to 0.25, 1.00, 2.50, 5.00 and 10.00 g/day of dietary ruminally protected L-carnitine (RPLC) and were allowed to adapt for 20 days. Plasma samples were obtained at 0, 120 and 240 min after RPLC feeding. Plasma L-carnitine (LC) concentrations increased (p<0.01) for all levels of RPLC treatment, however, no differences were observed due to level of RPLC or time. Plasma LC concentrations were 27.05 and 57.83 micromol/l for baseline and pooled RPLC treated sheep, respectively. In Experiment 2, lambs were randomly assigned to 0, 0.125, 1.06 and 2.0 g/day of RPLC and were adapted as in Experiment 1. Plasma was collected at 0, 15, 30, 60, 90, 180, 240 and 360 min after oral ammonia challenge (300 mg/kg BW urea). Plasma LC concentrations increased with treatment relative to control (p<0.01). Plasma LC concentrations were 35.7, 44.2, 60.5 and 65.7 micromol/l for the 0, 0.125, 1.06 and 2.0 g/day treatments, respectively. RPLC tended to decrease plasma ammonia at some time points (time x treatment; p=0.10). We conclude that RPLC increased plasma LC concentrations, but had only modest effects on plasma ammonia concentrations and had no effect on plasma urea or glucose concentrations.

Effect of glycine and vitamin supplementation on sulphur amino acid utilization by growing cattle.

Effects of glycine (Gly) and B-vitamins on sulphur amino acid (AA) utilization were studied in growing steers maintained under conditions where methionine (Met) was first limiting. Conditions were generated by limit feeding a diet low in ruminally non-degraded protein and abomasally infusing an AA mixture limiting in Met. Retained N tended (p = 0.07) to improve when steers received 10 mg folate, 10 mg vitamin B6, and 0.10 mg vitamin B12 daily. Hepatic vitamin B12 (p = 0.08) and folate (p = 0.05) concentrations increased with vitamin supplementation. In another trial, factorial treatments were 2 or 5 g/day L-Met and 0 or 50 g/day Gly infused abomasally. Retained N increased (p < 0.05) in response to Met, and responses were numerically larger in the presence of supplemental Gly. In a different trial, factorial treatments were 0 or 2.4 g/day L-cysteine (Cys) and 0 or 40 g/day Gly. Retained N was not affected by Cys in the absence of Gly, but was increased by Cys when Gly was supplemented (interaction, p = 0.01). B-vitamin status may affect sparing of Met by Cys. Supplemental Gly improved responses to supplemental Met and Cys.

Supplemental betaine and peroxide-treated feather meal for finishing cattle.

These studies evaluated the effects of betaine, provided either as feed-grade betaine or as concentrated separator by-product (CSB; desugared beet molasses), on performance and carcass characteristics of finishing cattle. In Exp. 1, 175 steers (410 kg initial BW) were fed a finishing diet based on steam-flaked and dry-rolled corn, and treatments included 10.5 and 21 g/d feed-grade betaine and 250 and 500 g/d CSB (supplying 15.5 and 31 g/d of betaine, respectively). Steers fed feed-grade betaine had greater (linear and quadratic effects, P < 0.1) DMI than control steers, but ADG and gain efficiencies were not affected by treatment. Dressing percent and backfat thickness was greater (P < 0.1) for steers that received feed-grade betaine than for controls. Longissimus muscle area was lower (P < 0.1) for steers supplemented with either feed-grade betaine or CSB than for control steers. Yield grades were higher for cattle receiving feed-grade betaine (quadratic effect, P < 0.1) than for control steers. Marbling scores were not affected by supplemental betaine, but the percentage of carcasses grading USDA Select was lower (linear and quadratic effects, P < 0.1) for steers fed feed-grade betaine than for control steers, predominantly due to a greater percentage grading USDA Choice. In Exp. 2, 312 heifers (343 kg initial BW) were used in a finishing study to evaluate the effects of graded levels of feed-grade betaine and peroxide-treated feather meal on performance and carcass characteristics. Treatments included two finishing diets (containing peroxide-treated or untreated feather meal) and four levels (0, 4, 8, and 12 g/d) of feed-grade betaine arranged in a 2 x 4 factorial. No significant interactions occurred between treatment of feather meal and betaine. Treatment of feather meal with hydrogen peroxide (5% wt/wt) increased in situ protein degradability but did not alter DMI, ADG, gain efficiencies, or carcass characteristics of heifers when it replaced untreated feather meal in the diet. Top-dressing feed-grade betaine to the diets had no effect on DMI, ADG, and gain efficiencies. Marbling scores were greater (cubic effect, P < 0.05) for heifers fed diets top-dressed with 4 and 12 g/d of feed-grade betaine, but other carcass characteristics were not altered significantly. Overall, feed-grade betaine and CSB did not alter growth performance, but did have minor effects on carcass characteristics.

Branched-chain amino acids for growing cattle limit-fed soybean hull-based diets.

Five ruminally cannulated Holstein steers (176 kg) were used in a 5 x 5 Latin square to evaluate the effects of branched-chain AA supplementation on N retention and plasma AA concentrations of steers. Steers were limit-fed (3.0 kg/d of DM) twice daily diets low in ruminally undegradable protein (72% soybean hulls, 19% alfalfa, 5% molasses, and 4% vitamins and minerals). Acetate (400 g/d) was continuously infused into the rumen. Treatments were continuous abomasal infusions of 1) 115 g/d of a mixture of 10 essential AA designed to exceed the steers' requirements (10AA), 2) 10AA with Leu removed, 3) 10AA with Ile removed, 4) 10AA with Val removed, and 5) 10AA with all three branched-chain AA removed. Experimental periods were 7 d, with 3 d for adaptation to treatments and 4 d for total fecal and urinary collections for N balance. Blood samples were collected 5 h after feeding on d 7. Retained N decreased in response to removal of Leu (P < 0.06), Val (P < 0.05), or all three branched-chain AA (P < 0.05). Plasma Leu concentrations decreased (P < 0.05) in response to removal of Leu and all three branched-chain AA. Plasma Ile concentrations decreased (P < 0.05) in response to removal of Ile and all three branched-chain AA but increased (P < 0.05) in response to removal of Leu. Plasma Val concentrations decreased (P < 0.05) in response to removal of Val and all three branched-chain AA but increased (P < 0.05) in response to removal of Leu. Responses in N balance and plasma AA concentrations of growing cattle limit-fed soybean hull-based diets demonstrate limitations in the basal supply of Leu and Val but not Ile provided that supplies of all other essential AA are met.

Effects of supplemental alfalfa hay on the digestion of soybean hull-based diets by cattle.

We evaluated the optimal level of alfalfa inclusion in soybean hull-based diets. In Exp. 1, 20 Holstein steers (319 kg of BW) were used in a complete block design. Treatments included a soybean hull mix (95.7% soybean hulls, 3% molasses, 0.5% urea, 0.8% mineral mix; DM basis) fed alone (100:0) or with 10.4, 20.7, or 30.9% (DM basis) coarsely chopped alfalfa hay (90:10, 80:20, and 70:30, respectively) or alfalfa alone (0:100). Diets were fed once daily at 1.75% (DM basis) of BW. In some cases, orts were present, which caused DM, OM, and NDF intakes to decrease (linear, P < 0.05) as alfalfa was added to the diets. Digestibilities of DM, OM, and NDF decreased linearly (P < 0.05) as alfalfa was added to the diets, but quadratic responses (P < 0.05) indicated that positive associative effects occurred between soybean hulls and alfalfa. Liquid dilution rates increased (linear, P < 0.05) with alfalfa additions to the diets and also demonstrated positive associative effects between soybean hulls and alfalfa (quadratic, P < 0.05). Solid passage rates were similar for 100:0 and 0:100 but were increased (quadratically and cubically, P < 0.05) when combinations of soybean hulls and alfalfa were fed. In Exp. 2, in vitro NDF digestibilities were measured for soybean hulls, alfalfa, and a blend of 85% soybean hulls and 15% alfalfa, each with no N source or supplemented with casein or urea to ascertain the effects of protein from alfalfa on digestibility. Disappearances were increased (P < 0.05) by addition of urea or casein, but no interactions between substrate and N supplement were observed. Addition of 30% alfalfa to diets consisting primarily of soybean hulls led to positive associative effects on diet digestibility, but alfalfa additions led to increased liquid and solid passage rates, suggesting that the benefit was not a result of slower passage of soybean hulls from the rumen.