Stockpiled Tifton 85 bermudagrass for backgrounding stocker cattle.

A 2-yr grazing trial was conducted to evaluate the use of conserved forage type, stockpiled Tifton 85 bermudagrass ( L.; T85) or T85 hay, and supplement type for stocker cattle during the fall forage deficit in the southeastern United States. The study site consisted of six 0.75-ha paddocks of stockpiled T85 for grazing and six 0.20-ha drylot paddocks for feeding T85 hay. Steers ( = 5 per paddock; mean initial BW for both yr, 263 ± 30 kg) were randomly assigned to paddocks on November 11, 2014 and October 28, 2015 in yr 1 and yr 2, respectively. Treatments included T85 hay or stockpile (control), T85 hay or stockpile plus 0.2 kg cottonseed meal and 0.7 kg soybean hulls∙steer∙d (SUPPL1), or 0.45 kg cottonseed meal and 0.45 kg soybean hulls∙steer∙d (SUPPL2). Polytape fencing was used for frontal grazing stockpiled T85 paddocks to allocate a 3- to 4-d allotment of forage DM for the animals based on available forage mass and steer DMI requirements. There were no differences among treatments ( > 0.10) in mean pregrazing forage mass across sampling dates (5,099 kg DM/ha and 7,998 kg DM/ha in yr 1 and yr 2, respectively), forage allowance (1.9 kg DM/kg steer BW and 3.0 kg DM/kg steer BW in yr 1 and yr 2, respectively) and forage utilization (84% and 88% in yr 1 and yr 2, respectively). No differences ( > 0.10) were detected for nutritive value parameters CP, ADF, NDF, and TDN among stockpiled T85 treatments in both yr. However, there were differences across sampling dates ( < 0.0001) for stockpiled T85 such that forage quality generally declined as the grazing season progressed in both yr. Steers fed T85 hay had greater final BW and ADG ( = 0.018) than those grazing stockpiled T85. Mean final BW and ADG of steers grazing T85 stockpile or fed hay with no supplementation was less ( = 0.020) than those receiving supplementation. Steers grazing stockpiled T85 had decreased ADG in the second half of the grazing season in both yr of the study, which is a result of declining forage nutritive value as the stockpiling season progressed. Results indicate that stockpiled T85 supplemented with CP and energy can support stocker cattle at a maintenance level, but to achieve a target gain of 0.9 kg/day would require a greater level of supplementation to overcome decreasing forage nutritive value dynamics.

Fiber digestion kinetics and protein degradability characteristics of stockpiled Tifton 85 bermudagrass.

A 2-yr study was conducted to determine effects of N fertilization level on fiber digestion kinetics and protein degradability characteristics of stockpiled Tifton 85 bermudagrass (T85). Six 0.76-ha pastures of stockpiled T85 were cut to a 10-cm stubble height on August 1 of each yr and fertilized with 56 (56N), 112 (112N), or 168 (168N) kg N/ha (2 pastures/treatment). Fiber digestion kinetics included the 72-hr potential extent of NDF digestion (PED), rate of NDF digestion, and lag time. In yr 1 and 2, PED decreased over the stockpile season. Rates of NDF digestion did not differ ( > 0.05) among N fertilization treatments in either yr. In yr 1, rate of NDF digestion was greatest ( < 0.05) in October/November, and decreased beginning in December. In yr 2, rate of NDF digestion decreased ( < 0.05) in January compared with November, but digestion rates were similar for November and January 21 sampling dates. Lag time was greater ( < 0.05) for the 112N than 56N and 168N treatments, and increased ( < 0.05) across sampling dates in yr 1. In yr 2, lag time increased ( < 0.05) from 9.0 to 17.7 h across the season. In yr 1 and 2, a negative correlation ( < 0.05) between forage lignin concentration and both PED ( = -0.91 and -0.87 in yr 1 and 2, respectively) and rate of NDF digestion ( = -0.60 and -0.25 in yr 1 and 2, respectively) was observed. There was a trend ( = 0.06) for lignin concentration to be positively correlated with lag time ( = 0.39) in yr 1, and a strong relationship was observed in yr 2 ( = 0.91; < 0.05). The RDP fraction as a % of CP was ≥ 90% throughout both years. Concentration of RDP (% of total DM) decreased across the stockpiling season through January in yr 1 and 2. Results suggest that kinetic parameters of NDF digestion in stockpiled T85 were influenced more by temporal changes over the stockpile season than by N fertilization level. Supplement formulations based on kinetic parameters of fiber digestion may require periodic adjustment to insure that energy-yielding components of NDF are sufficient to meet animal requirements throughout the stockpile season. The CP fraction in stockpiled T85 contains sufficient RDP to support fibrolytic activity and growth of ruminal microorganisms throughout the stockpile season. Toward the latter end of the season, supplementation with sources of digestible fiber and RDP could be expected to increase MP supply to the host animal.

Changes in southern Piedmont grassland community structure and nutritive quality with future climate scenarios of elevated tropospheric ozone and altered rainfall patterns.

Forage species common to the southern USA Piedmont region, Lolium arundinacea, Paspalum dilatatum, Cynodon dactylon and Trifolium repens, were established in a model pasture system to test the future climate change scenario of increasing ozone exposure in combination with varying rainfall amounts on community structure and nutritive quality. Forages were exposed to two levels of ozone [ambient (non-filtered; NF) and twice ambient (2×) concentrations] with three levels of precipitation (average or ±20% of average) in modified open-top chambers (OTCs) from June to September 2009. Dry matter (DM) yield did not differ over the growing season between forage types, except in primary growth grasses where DM yield was higher in 2× than NF treatment. Primary growth clover decreased in nutritive quality in 2× ozone because of increased concentrations of neutral detergent fibre (NDF), acid detergent fibre (ADF) and acid detergent lignin (ADL). Re-growth clover exhibited the largest decrease in nutritive quality, whereas grasses were not adversely affected in 2× ozone. Re-growth grasses responded positively to 2× ozone exposure, as indicated in increased relative food value (RFV) and percentage crude protein (CP) than NF-exposed re-growth grasses. Effects of precipitation were not significant over the growing season for primary or re-growth forage, except in primary growth grasses where DM yield was higher in chambers with above average (+20%) precipitation. Total canopy cover was significantly higher over the growing season in chambers receiving above average precipitation, but no significant effects were observed with ozone. Results indicate shifts in plant community structure and functioning related to mammalian herbivore herbivory in future climate change scenarios.

Productivity, utilization, and nutritive quality of dallisgrass (Paspalum dilatatum) as influenced by stocking density and rest period under continuous or rotational stocking.

Dallisgrass (Paspalum dilatatum) is well adapted to the Black Belt physiographic region of the southeastern United States, and information on its productivity and nutritive quality as influenced by grazing management is needed. In a 2-yr grazing experiment, replicate 0.40-ha paddocks in established dallisgrass pasture were continuously stocked, or replicate 0.40-ha paddocks were subdivided into two 0.20-ha (RS2), three 0.13-ha (RS3), or four 0.10-ha (RS4) cells and rotationally stocked with yearling beef steers. Individual cells within the RS2, RS3, and RS4 treatments were stocked for 7 d followed by 7, 14, or 21 d of rest, respectively. In 2007, 3 Angus × Simmental crossbred steers (initial BW, 354 ± 6 kg) were assigned randomly to each paddock on July 16; in 2008, 3 Angus × Simmental crossbred steers (initial BW, 310 ± 6 kg) were assigned randomly to each paddock on July 14. In 2007, there was no effect (P = 0.25) of stocking treatment on ADG. Steers grazing RS4, RS2, and continuously stocked paddocks had 106 (P = 0.01), 86 (P = 0.03), and 83 (P = 0.03) kg greater total BW gain per ha, respectively, than steers grazing RS3 paddocks. In 2008, there were no differences among treatments in ADG (P = 0.43) or total BW gain per ha (P = 0.90). Correlation and regression analyses revealed positive associations between steer performance and forage concentration of CP, areal mass (kg/ha) of forage DM, and areal mass of forage CP. Results indicate that productivity and quality of dallisgrass for stocker cattle production were comparable between continuous and rotational-stocking methods.

Alfalfa nutritive quality for ruminant livestock as influenced by ambient air quality in west-central Alberta.

Alfalfa (Medicago sativa) nutritive quality response to ambient ozone (O(3)), sulfur dioxide (SO(2)) and oxides of nitrogen (NO(x)) were assessed at three locations in west-central Alberta, Canada (1998-2002). Yield data were segregated into high and low relative to overall median yield. Ozone concentrations (hourly median and 95th-percentile) and precipitation (P) contributed 69 and 29%, respectively, to the variability in crude protein (CP) concentration in low-yielding alfalfa, whereas mean temperature (T) and relative humidity (RH) collectively influenced 98% of the variation in CP in high-yielding alfalfa. Three-fourths of the accounted variation in relative feed value (RFV) of low-yielding alfalfa was attributable to P, T and RH, whereas median and 95th-percentile hourly O(3) concentrations and SO(2) and NO(x) exposure integrals contributed 25%. In contrast, air quality, (mainly O(3)) influenced 86% of the accounted variation in RFV of high-yielding alfalfa, and T and P collectively contributed 14%.

Growth and nutritive quality of Poa pratensis as influenced by ozone and competition.

Interspecific plant competition has been hypothesized to alter effects of early-season ozone (O3) stress. A phytometer-based approach was utilized to investigate O3 effects on growth and nutritive quality of Poa pratensis grown in monoculture and in mixed cultures with four competitor-plant species (Anthoxanthum odoratum, Achillea millefolium, Rumex acetosa and Veronica chamaedrys). Mesocosms were exposed during April/May 2000-2002 to charcoal-filtered air+25 ppb O3 (control) or non-filtered air+50 ppb O3 (elevated O3). Biomass production was not affected by O3, but foliar injury symptoms were observed in May 2002. Early-season O3 exposure decreased relative food value of P. pratensis by an average of 8%, which is sufficient to have nutritional implications for its utilization by herbivores. However, forage quality response to O3 was not changed by interspecific competition. Lack of injury and nutritive quality response in P. pratensis harvested in September may reflect recovery from early-season O3 exposure.

Yield and nutritive quality of sericea lespedeza (Lespedeza cuneata) and little bluestem (Schizachyrium scoparium) exposed to ground-level ozone.

Sericea lespedeza (Lespedeza cuneata cv. Interstate 76) and little bluestem (Schizachyrium scoparium cv. Aldous) were raised from seed in a glasshouse, transplanted into 5.7-l pots and placed into open-top chambers (OTC) on 6 June 1999. Following a 7-day adjustment period, each of six OTCs (duplicate OTCs per treatment) was ventilated with either air that had been carbon-filtered (CF) to remove ambient ozone (O3); non-filtered (NF), representative of ambient air; or enriched to twice-ambient O3 concentration (2X). Primary-growth forage was harvested on days 7, 32, 46, 59 and 72 following the start of fumigation, and regrowth forage from the first primary-growth harvest was harvested on days 36, 54 and 72 following the start of fumigation. Dry matter (DM) yield of either forage species did not differ among treatments except in the final regrowth period when yield of sericea lespedeza was greater for the NF than 2X O3 treatment. In vitro DM digestibility (IVDMD) and concentrations of crude protein (CP), soluble phenolics (SP) and condensed tannins (CT) in primary-growth sericea lespedeza did not differ between treatments, but NF primary-growth forage had higher concentration of protein-precipitating tannins (PPT) than did 2X primary-growth forage. Concentrations of neutral detergent fiber (NDF), acid detergent fiber (ADF) and acid detergent lignin (ADL) were higher in NF and 2X than in CF primary-growth sericea lespedeza. Similarly, concentrations of NDF and ADL were higher, and IVDMD was lower for NF and 2X than for CF regrowth sericea lespedeza. Concentrations of ADF and ADL were lower, whereas IVDMD, in vitro NDF digestibility (IVNDFD) and concentrations of CP and SP were greater, in CF than in NF and 2X primary-growth little bluestem. Percentages IVDMD and IVNDFD and concentrations of CP and SP in NF primary-growth little bluestem were greater than those in forage exposed to 2X O3 treatment. No significant differences were observed among treatments in percentages IVDMD and IVNDFD, or concentrations of cell wall constituents or SP in little bluestem regrowth. Nutritive quality of little bluestem was decreased by < 2%, and that of sericea lespedeza by approximately 7% as a result of increased concentrations of cell wall constituents and decreased in vitro digestibility of NF and 2X compared with CF forages. Results indicate that existing and projected O3 levels can drive alterations in forage quality of select warm-season forages sufficient to have nutritional and economic implications for their utilization by ruminant herbivores.

Growth and subsequent feedlot performance of estradiol-implanted vs nonimplanted steers grazing fall-accumulated endophyte-infested or low-endophyte tall fescue.

A growing-finishing study using Angus steer calves was conducted in three phases: 1) grazing stockpiled 'Kentucky-31' tall fescue (Festuca arundinacea Schreb.) with high (65%; HE KY-31) and low (0%; LE KY-31) infestation rates of Acremonium coenophialum Morgan-Jones and Gams and 'Kenhy' and 'Johnstone' tall fescue with low (< 1%) infestation rate of Acremonium coenophialum from October 24 to December 19; 2) drylot feeding of Johnstone and HE KY-31 haylage (December 19 to April 10); and 3) feedlot finishing on a common high-concentrate diet (April 11 to August 1). In Phase 1, ADG was greatest (P < .05) for Kenhy, intermediate for Johnstone and LE KY-31, and lowest (P < .05) for HE KY-31. Implantation with estradiol 17-beta increased ADG (P < .01) by 23, 27, 7, and 2% for steers grazing Johnstone, HE KY-31, LE KY-31, and Kenhy, respectively. Dry matter digestibility and DMI of stockpiled Johnstone and HE KY-31 were not different (P > .10). During Phase 2, steers consuming Johnstone haylage had greater (P < .01) DMI, ADG, and gain:feed ratio (G:F) than steers consuming HE KY-31 haylage. During Phase 3, steers previously consuming Johnstone had greater DMI (P < .10); however, steers previously fed HE KY-31 had greater ADG (P < .05) and G:F (P < .01). By the end of the study, steer body weights were not different (P > .10) between treatments. These data indicate that growth-decreasing effects of endophyte-infested fescue were evident at hypothermal-ambient temperatures.(ABSTRACT TRUNCATED AT 250 WORDS)

Feed aversion learning in cattle with delayed negative consequences.

Two experiments were conducted to study the ingestive behavior of cattle when given a delayed dose of the aversive agent lithium chloride (LiCl) after eating a novel feed. In the first experiment, 20 calves were randomly divided into four groups (n = 5). The control group (G1) received 80 mg/kg BW of sodium chloride (NaCl) 4 h after eating a novel feed. Groups 2 (G2), 3 (G3), and 4 (G4) received 80 mg/kg of LiCl at 4, 8, and 12 h, respectively, after eating the novel feed. When calves were offered the novel feed on subsequent days, G2 and G3 ate less (P < .05) than G1. There was no difference (P > .05) in intakes between G1 and G4. In the second experiment, 15 calves were randomly divided into three groups (n = 5). The control group (G1) received 80 mg/kg BW of NaCl 12 h after eating a novel feed, whereas G2 and G3 received 80 and 160 mg/kg BW, respectively, of LiCl 12 h after eating the novel feed. When calves were offered the novel feed on subsequent days, G1 and G2 ate similar (P > .05) amounts, whereas G3 ate much less (P < .05) of it than the other groups. Cattle learned to avoid novel feeds even when they experienced negative postingestive consequences up to 12 h after they ate the feeds. The capacity for long-delay learning seems to be related to the severity of negative consequences experienced.

Voluntary intake and ingestive behavior of steers grazing Johnstone or endophyte-infected Kentucky-31 tall fescue.

Effects of grazing low-endophyte (Acremonium coenophialum Morgan-Jones and Gams, less than 1% infection) Johnstone (J) or high-endophyte (60% infection) Kentucky-31 (K) tall fescue (Festuca arundinacea Schreb.) on grazing behavior and voluntary intake were studied. Six Angus steers (average initial BW = 326 kg) grazed 1.21-ha plots of each forage cultivar (three steers per cultivar) in four 28-d periods beginning May 27. Daytime observations (0630 until 2130) revealed that J steers spent more (P less than .10) time grazing and lying down and took more (P less than .05) prehensile bites than K steers did; conversely, steers grazing K spent more (P less than .10) time standing and idling than J steers did. Idling time showed a forage x period interaction (P less than .10). Mean OM bite size (grams per bite) was not affected (P greater than .10) by forage but differed (P less than .10) among periods. Limited nighttime observations (2130 until 0630) revealed no effects (P greater than .10) of forage on grazing time or number of prehensile bites taken. Voluntary intakes of OM and NDF did not differ (P greater than .10) between steers grazing J and K; however, a forage x period interaction (P less than .10) existed such that, during Period 1, steers grazing J had greater (P less than .01) OM and NDF intakes than did steers grazing K. These data suggest that cattle grazing endophyte-infected tall fescue display altered daytime grazing behavior and that reduction of voluntary intake attributable to endophyte infection may be less severe under free-grazing than has been reported for controlled environmental conditions.

Forage composition and intake by steers grazing vegetative regrowth in low endophyte tall fescue pasture.

A grazing trial was conducted with six half-sib yearling Angus steers (average initial weight 281 kg) to quantitate nutrient composition and voluntary intake of vegetative regrowth forage in low-endophyte (Acremonium coenophialum Morgan-Jones and Gams) Kentucky-31 tall fescue (Festuca arundinacea Schreb.) pasture. A new .6-ha section in each of two 3.0-ha pastures (three steers/pasture) was clipped to a 5-cm height on five consecutive days to establish a series of plots that could be grazed continuously during 5-d test periods at uniform stages of vegetative regrowth; each period represented a specific regrowth stage (7, 14, 21, 28 and 35 d). Steers were conditioned by training them to graze to satiety while tethered with an adjustable-length rope to a 1-m galvanized steel post. Grazing time was limited to two sessions daily beginning at 0800 and 1400, and satiety was achieved after no more than 2.5 h of continuous grazing in each session. Forage DM availability was controlled by adjusting tether length and was set each day at 4% of steer BW. Fecal DM output was measured by chromic oxide dilution. A quadratic (P less than .05) effect of regrowth stage was observed for forage contents of NDF and ADF due to abrupt increases in both fractions at wk 5; values for ADL were unaffected by stage of forage regrowth. Forage contents of CP and ash showed a cubic (P less than .05) response to advancing stage of regrowth, with highest (23.6 and 11.0%, respectively) and lowest (14.7 and 9.1%, respectively) values for both fractions occurring at wk 1 and 5, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolism of decoquinate in chickens and Japanese quail.

Thirty mature chicken hens and 40 mature Japanese quail hens were used in an experiment to compare pathways of decoquinate (DQ) excretion. Labelled DQ was injected into chickens (.5 microCi via wing vein puncture) and quail (.25 microCi via cardiac puncture) on Day 0. Blood was sampled at 0, 1.5, 3, 6, 9, 12, 24, and 48 h postinjection. Eggs and excreta of chickens and quail were collected for 28 and 14 days, respectively, and analyzed for 14C. Six chickens and eight quail were sacrificed prior to 14C-DQ injection and also on Days 1, 7, 14, and 34 or 32 postinjection. Samples of liver, heart, kidney, bile, skin, fat, and muscle were analyzed for 14C. Blood rapidly cleared 14C in both species, and the half-time of 14C excretion via excreta was more rapid in quail (.37 day) than in chickens (.92 day). Little 14C was found in the eggs of quail (.32% of dose) and chickens (.17% of dose). Quail appeared to excrete peak amounts of detectable 14C 1 day earlier (Day 4) than chickens (Day 5). Liver contained the greatest concentration of 14C on Day 1 in both species. By the end of the experiment, less than 1% of the dose remained in liver or other organs. Results indicate that chickens and quail metabolize 14C-DQ at comparable rates and by similar pathways.

Comparative drug depletion in domestic animals and birds.

Decoquinate (Rhone-Poulenc Inc) and Narasin (Eli Lilly and Co) were selected as model drugs for a comparison of metabolism between major (cattle and chickens) and minor (sheep and quail) species. Decoquinate has been studied in all four species. Narasin studies are in progress in chickens and quail. More than 96% of injected 14C-decoquinate (DQ) was eliminated from blood of all species within 1 hr. Disappearance of the remaining 1 to 4% from blood was rapid for all species. Half-times for DQ appearance in excreta were all less than one day. Cumulative excretion of DQ in eggs of chickens and quail was about 1% for both species. Disappearance of DQ from tissues was essentially complete in 14 days. More than 80% of injected 14C-narasin was eliminated from blood within 1/2 hr. Disappearance of the remainder was rapid for both chickens and quail.

Growth and metabolism of growing beef calves fed tall fescue haylage supplemented with protein and(or) energy.

Endophyte (Acremonium coenophialum)-infected Kentucky 31 tall fescue was fertilized in mid-August, stockpiled, harvested November 4 to 6 and stored in a concrete stave silo. Ninety-six growing calves (189 kg) were assigned to the following treatments (24 calves/treatment): 1) corn silage (CS) plus .4 kg/d of soybean meal (SBM; 2) fescue haylage plus .4 kg/d of SBM; 3) fescue haylage plus 1.6 kg/d of corn and 4) fescue haylage plus 1.6 kg/d of corn and .4 kg/d of SBM. Daily gains and dry matter (DM) intakes during the 91-d trial were .52, 4.58; .51, 5.22; .59, 6.06; and .63, 6.18 kg for treatments 1 through 4, respectively. Daily gains of calves fed corn silage plus SBM and fescue haylage plus SBM were not different (P greater than .05). However, a difference (P less than .05) existed between treatments 1 and 2 vs 3 and 4. Feed conversion was improved (P less than .05) in calves fed corn silage. Calves in a metabolism trial were fed either 1) 6.2 kg November-ensiled fescue haylage or 2) 6.2 kg November-ensiled fescue haylage plus 1.6 kg/d of corn. Digestibility of DM, N-free extract (NFE) and TDN did not differ (P greater than .05) between treatments. Ether extract digestibility was greater (P less than .05) for the added corn diet, while that of CP was greater (P less than .05) for the fescue haylage diet. Nitrogen retained was higher (P less than .05) for calves fed added corn. A follow-up trial with 96 growing calves (190 kg) compared September- and November-harvested fescue haylages supplemented with either 1.3 or 2.6 kg corn/d.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of feeding frequency on forage fiber and nitrogen utilization in sheep.

Four crossbred wether lambs (38 kg) with permanent ruminal and abomasal cannulae were used in a 4 X 4 Latin square arrangement of treatments to determine the effect of feeding frequency (FF) on forage fiber and N utilization. Lambs were offered 900 g of good quality (vegetative) Kentucky-31 tall fescue hay in equal portions either 2, 4, 8 or 16 times daily. Water consumption increased (P less than .05; linear) with increased FF. Apparent total tract digestibilities of dry matter, organic matter and cell wall constituents were not affected (P greater than .05) by FF, but apparent total tract digestibility of crude protein decreased (P less than .05; linear) with increased FF. Ruminal and post-ruminal digestion of acid detergent fiber (percent of total tract digestion) differed (P less than .05; cubic) among FF treatments. Although N retention was not affected (P greater than .05) by FF, increased FF decreased (P less than .05; linear) mean ruminal ammonia-N concentrations. Both the quantity of total N reaching the abomasum and the efficiency of microbial crude protein synthesis tended to increase (P greater than .05) with increased FF. In addition, the daily quantity of microbial N reaching the abomasum was affected (P less than .05; cubic) by FF. Ruminal pH was not affected (P greater than .05) by FF, whereas total volatile fatty acid concentrations (VFA) decreased (P less than .05; linear) with increased FF. Responses in molar proportions of individual VFA to FF were variable, and suggest that increasing FF elicits significant changes in the distribution of fermentation end-products.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of dietary protein level on nitrogen metabolism in lambs: studies using 15N-nitrogen.

Six wether lambs (31 kg) were randomly assigned to two treatments (three lambs/treatment): a high protein intake (HP; 21 g N/d) or a low protein intake (LP; 12 g N/d). Each lamb received 860 g/d dry matter (DM) of a pelleted diet (75% corn-soybean meal, 25% cottonseed hulls) offered hourly in 24 equal portions. Single injections of 15N-labelled compounds were made into the ruminal NH3-N and blood urea-N pools to measure the rate of flux through, and transfer of N between, these and the bacterial N pool. Total tract digestibilities of DM and N were lower (P less than .05) for the LP than the HP treatment. Abomasal flows of total, feed or bacterial N tended to be greater (P greater than .05) in lambs fed HP than LP. Lambs fed HP excreted more (P less than .01) urinary N, yet retained a greater (P less than .01) amount of N than lambs fed LP (6.2 vs 1.8 and 9.7 vs 4.1 g N/d, respectively). Pool size and production rate for both ruminal NH3-N and blood urea-N were greater (P less than .05) for the HP than LP treatment. Lambs consuming HP degraded more (P less than .05) blood urea-N in the gastro-intestinal tract (13.4 vs 6.9 g N/d); however, lambs fed LP degraded a greater (P less than .05) percentage of synthesized body urea-N (88.7 vs 71.8%). Ruminal NH3-N absorption was greater (P less than .01) for the HP than LP treatment (3.1 vs .5 g N/d). Although the percentage of bacterial N derived from ruminal NH3-N was similar (P greater than .05) between diets (51.1 vs 63.9), a greater (P less than .05) percentage of bacterial N was derived from blood urea-N in lambs fed LP than HP (77.1 vs 30.2%). Lambs fed LP incorporated a greater (P less than .10) amount of blood urea-N into bacterial N than lambs fed HP (5.5 vs 2.6 g N/d). These data are interpreted to suggest that blood urea-N may provide a substantial quantity of N for bacterial protein synthesis and, thus, may be an important source of protein in the deficient animal. In addition, urea recycling may play an important role in the recovery of ruminal NH3-N lost through absorption in animals fed a high level of protein.

Comparative metabolism of 14C-decoquinate in chickens, quail and sheep.

Removal of pulse doses of 14C-decoquinate from blood was studied in chicken hens, quail hens, and ewe lambs. Estimated clearance before the first post-injection sample at 1 1/2 hr was 96% for sheep, 99% for chickens and over 99% for quail. Half-times for removal of the remaining radioactivity from the blood were 26.8 hr for sheep, 144.7 hr for chickens and 27.2 hr for quail. Treating the chicken data as biphasic yielded a 3.4 hr half-time for an initial fast phase and 210 hr for a later slow phase. Radioactivity disappeared from sheep blood between 2 and 7 d, from chicken blood between 7 and 14 d, and from quail blood between 1 and 2 d. Urine accounted for 35% of the radioactivity administered to sheep. It did not contain detectable activity after the third day.

Effects of diet concentrate level and sodium bicarbonate on site and extent of forage fiber digestion in the gastrointestinal tract of wethers.

Four adult wethers (45 kg) with permanent ruminal and abomasal cannulae were used in a repeated measures Latin-square arrangement of treatments to quantitate the effects of diet concentrate level and sodium bicarbonate (NaHCO3) on site and extent of forage fiber digestion in the gastrointestinal tract. Experimental diets consisted of Kentucky-31 tall fescue hay, soybean meal and a semi-purified concentrate mixture in ratios of 95:5:0, 76:4:20, 57:3:40 and 38:2:60; NaHCO3 represented 0 or 7.5% of the concentrate mixture. Ruminal digestion (% of intake) of neutral detergent fiber (NDF) and hemicellulose decreased linearly (P less than .05), whereas acid detergent fiber (ADF) digestion responded in a cubic (P less than .05) fashion to increasing concentrate level; NaHCO3 improved ruminal digestion of NDF (P less than .10) and ADF (P less than .05), but not hemicellulose. Post-ruminal digestion (% of rumen non-degraded) of NDF and ADF tended to increase, whereas hemicellulose digestion responded in a cubic (P less than .05) fashion to increasing concentrate level; NaHCO3 decreased (P less than .05) post-ruminal digestion of all fiber fractions. Total tract digestion of NDF and ADF showed a cubic (P less than .05) response, whereas hemicellulose digestion responded in a quadratic (P less than .05) fashion to increasing concentrate level; NaHCO3 had no effect on total tract digestion of any fiber fraction. Correlations of ruminal hemicellulose digestion with mean pH (r = .33; P = .07) and minimum pH (r = .30; P = .09) were attained in a 24-h feeding cycle.(ABSTRACT TRUNCATED AT 250 WORDS)

Pancreatic amylase, plasma glucose, and insulin responses to propionate or monensin in sheep.

Yearling wethers fitted with reentrant bile-pancreatic duct cannulae were in a two-part study of effects of duodenal propionate infusions or increased ruminal propionate caused by dietary monensin on pancreatic alpha-amylase secretion and glucose and insulin in blood plasma. Continuous duodenal infusion of propionate increased concentrations of glucose and insulin in blood plasma of wethers fed alfalfa. Results supported a direct response of insulin secretion to propionate. Amylase secretion was not affected. Addition of monensin (22 ppm) to an 80% corn diet reduced the ratio of acetate:propionate in rumen, but bile-pancreatic flow and amylase activity were unaffected. Monensin supplementation had little influence on glucose and insulin in blood plasma. Pancreatic alpha-amylase secretion of ruminants seems to be a complex phenomenon that is not regulated strictly by fluctuations of glucose or insulin.