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.     

Effect of ruminal escape protein and fat on nitrogen utilization in lambs exposed to elevated ambient temperatures.

Eight wether lambs (mean BW = 28.8 kg) with ruminal and abomasal cannulas were assigned to either thermally neutral or high ambient temperature treatments. Within each temperature, lambs were randomly allotted to dietary treatments consisting of a basal diet (60% corn and 24% cottonseed hulls) either with (high; 11.4% CP) or without (control; 10.1% CP) added ruminal escape CP as fish meal and with (high) or without (control) 5% added ruminally inert fat in a 2 x 2 factorial treatment arrangement using a Latin square design. Lambs were fed 606 g of DM/d in each period, which consisted of a 10-d adjustment followed by 6 d of sample collection. High temperature increased (P less than .05) respiration rate, evaporative water loss, and rectal temperature. When compared with controls, lambs fed high escape CP retained more N when exposed to high temperatures (2.8 vs 3.6 g of N/d) and less N at neutral temperatures (3.3 vs 3.1 g of N/d; temperature x escape CP; P less than .05). Retention of N was greater (P less than .05) in lambs fed high than in those fed control fat (3.8 vs 2.7 g/d). Lambs fed high vs control escape CP had greater abomasal feed N flow (percentage of intake) when fed high-fat diets (77.3 vs 56.1%) but similar dietary N flow when fed control fat diets (55.8 vs 54.3%; fat x escape CP; P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of dietary sewage solids on feedlot performance, carcass characteristics, serum constituents and tissue elements of growing lambs

Twenty fine-wool wether lambs were allotted randomly at weaning to be fed a conventional diet (CD) formulated for growing lambs, or the same basal mixture plus dried gamma-irradiated solids from primary sewage sludge (SS) incorporated as 7% of the dry matter. Feedlot performance and chemical elements in whole blood were monitored during 90 d, after which lambs were slaughtered and carcass data were collected. Concentrations of Ag, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, Pb and Zn were measured in livers, kidneys, bones, spleens and muscles. Sewage solids in the diet did not affect performance appreciably, although dressing percentages from lambs fed SS were 4% lower than CD-fed animals (P less than .05). Rib eye areas, fat thicknesses, quality and yield grades were similar (P greater than .05). Element concentrations in whole blood at weaning, after 56 d of the feeding trial and at slaughter did not differ (P greater than .05) between dietary groups. Serum chemistry determinations showed no biologically meaningful patterns related to diets. Lambs fed SS had higher (P less than .05) concentrations of Cu in livers (51.1 vs 34.3 +/- 3.8 micrograms/g, mean +/- SE) and Pb in kidneys (4.0 vs 2.2 +/- .3 micrograms/g) and lower (P less than .05) Mg in kidneys (.69 vs .72 +/- .01 mg/g). None of the elements in spleen and muscle tissue differed (P greater than .05) between diet groups. Lambs fed SS had elevated (P less than .05) bone Co, Cu, Fe, K and Na compared with those of CD.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of animal-to-animal exchange of ruminal contents on the feed intake and ruminal characteristics of fed and fasted lambs

Four Suffolk x Hampshire wether lambs averaging 55 kg with permanent ruminal cannulas were used in a 4 x 4 Latin square design to determine the effects of exchange of ruminal contents between fed and fasted lambs on subsequent DMI and ruminal characteristics. Lambs were fed a pelleted 70% roughage diet at 2% of BW for 17 d. During each period of the Latin square two lambs were deprived of feed and water for 3 d. At the end of the fasting period ruminal contents from one fed and one fasted lamb were exchanged. Lambs were then given ad libitum access to feed for 8 d, during which DMI, feeding pattern, and ruminal characteristics were monitored. Measurements of ruminal volume determined by total collection and indigestible marker (lithium sulfate) suggested that only about 50% of total ruminal contents were actually exchanged. Fasted lambs had lower (P less than .05) DMI, ruminal fermentative capacity, ruminal DM weight, and ruminal DM percentage than fed lambs during the first 4 d of realimentation. Exchange of ruminal contents did not (P greater than .10) affect DMI, feeding pattern, ruminal fluid pH, ruminal fermentative capacity, ruminal contents DM percentage, ruminal nucleic acid concentration, or VFA. Dosing fasted lambs with ruminal contents from nonfasted lambs reduced (P less than .05) ruminal liquid volume, dry weight of ruminal contents, and propionate concentration. Results of this trial are interpreted to indicate that although decreased ruminal function is a factor in the low feed intakes of fasted ruminants, the possibility of increasing postfast feed intake via improved ruminal function is limited because other metabolic factors may play a more important role.     

Effects of diet forage:concentrate ratio and metabolizable energy intake on visceral organ growth and in vitro oxidative capacity of gut tissues in sheep

We used 28 crossbred wether lambs to determine the effects of dietary forage:concentrate ratio and metabolizable energy intake on visceral organ growth and oxidative capacity of gut tissues in lambs. Lambs were assigned randomly to a factorial arrangement of dietary treatments consisting of pelleted diets containing either 75% orchardgrass or 75% concentrate fed once daily at either .099 or .181 Mcal ME x (kg BW(.75))(-1) x d(-1). After a 52-d feeding period, lambs were slaughtered to obtain measurements of visceral organ mass and composition and oxidative capacity of isolated epithelial cells. Lamb performance, as measured by DMI, ADG, and efficiency of gain, was greater (P = .0001) for both diets at high ME intake. Likewise, lambs fed 75% concentrate gained faster and more (P < or = .01) efficiently than lambs fed 75% forage. Total digestive tract (TDT; includes rumen, reticulum, omasum, abomasum, and intestines) weight increased (P = .0001) with ME intake and was greater (P = .03) in lambs fed 75% forage than in those fed 75% concentrate. As a percentage of empty body weight (EBW), TDT weight increased with ME intake in lambs fed 75% forage, but it was unaffected by ME intake in lambs fed 75% concentrate (diet x intake, P = .03). Liver weight increased (P = .0001) with ME intake and was greater (P = .005) in lambs fed 75% concentrate vs 75% forage; however, liver weight as a percentage of EBW was increased (P = .0002) with ME intake but was unaffected by diet. Greater ME intake increased (P < or = .02) small intestinal (SI) epithelial and muscle mass of 15-cm sections, whereas jejunal epithelial mass was greater (P = .01) for lambs fed 75% forage vs 75% concentrate. Rumen epithelial concentrations of DNA and RNA increased (P < or = .02) with greater ME intake, whereas SI concentrations of DNA and RNA were largely unaffected by diet or ME intake. The activity of Na(+)-K(+)-ATPase increased in ileal epithelium (P < or = .02) with ME intake and concentrate in the diet, but activity in ruminal epithelium increased (P = .05) with concentrate. Total oxygen consumption by isolated ruminal and intestinal epithelial cells was unaffected by treatment. These data suggest that ME intake and level of dietary forage affect ruminal and intestinal growth via changes in cellular hyperplasia. Additionally, this study supports the concept that ME intake and diet composition alter gut energy expenditure, at least in part, through changes in mass rather than mass specific metabolism.     

Supplemental butyrate does not enhance the absorptive or barrier functions of the isolated ovine ruminal epithelia

Our objective was to determine if increasing the ruminal butyrate concentration would improve the selective permeability of ruminal epithelia. Suffolk wether lambs (n = 18) with an initial BW of 47.4 ±1.4 kg were housed in individual pens (1.5 × 1.5 m) with rubber mats on the floor. Lambs were blocked by initial BW into 6 blocks and, within block, were randomly assigned to either the control (CON) or 1 of 2 butyrate supplementation amounts (i.e., 1.25% or 2.50% butyrate as a proportion of DMI). With the exception of butyrate supplementation, all lambs were fed a common diet (90% concentrate and 10% barley silage). After a 14-d feeding period, lambs were killed, and ruminal epithelia from the ventral sac were mounted in Ussing chambers. To facilitate the Ussing chamber measurements, only 1 lamb was killed on an individual day. Thus, the starting date was staggered so that all lambs were exposed to the same experimental protocol. In Ussing chambers, epithelia were incubated using separate mucosal (pH 6.2) and serosal (pH 7.4) bathing solutions. Then 1-14C-butyrate (74 kBq/10 mL) was added to the mucosal side and was used to measure the mucosal-to-serosal flux (J(ms-butyrate)) in 2 consecutive 60-min flux periods with simultaneous measurement of transepithelial conductance (G(t)). During the first (challenge) flux period, the mucosal buffer solution was either acidified to pH 5.2 (ACID) or used as a control (pH 6.2; SHAM). Buffer solutions bathing the epithelia were replaced before the second flux period (recovery). Total ruminal short-chain fatty acid and butyrate concentrations were greater (P = 0.001) in lambs fed 2.50% compared with those fed 0% or 1.25% butyrate. The J(ms-butyrate) was less for lambs fed 1.25% and 2.50% butyrate [3.00 and 3.12 μmol/(cm2·h), respectively] than for CON [3.91 μmol/(cm2· h)]. However, no difference (P = 0.13)was observed for G(t). An ex vivo treatment × flux period interaction was detected (P = 0.003) for J(ms-butyrate), where no differences were present between ACID and SHAM during the challenge period, but the Jms-butyrate was less for ACID than for SHAM during recovery. These results indicate that large increases in the ruminal butyrate concentration decrease the selective permeability of the isolated ruminal epithelia.     

Vitamin A deficiency: serum cortisol and humoral immunity in lambs

Serum cortisol and antigen-specific and polyclonal immunoglobulin G (IgG) concentrations were measured to investigate the relationship between vitamin A status and immune function in lambs. Twenty-four 3-mo-old crossbred ewe lambs weighing approximately 10 kg were each fed 900 g/d of a carotene-deficient diet. The 12 control lambs also received a 100,000 IU oral dose of vitamin A palmitate every 2 wk. All lambs were given primary and secondary antigenic challenges. Lambs were slaughtered at the end of the secondary challenge period. Liver vitamin A concentrations were greater (P less than .001) in the control animals (69.5 vs 1.3 micrograms/g wet tissue). Both groups of lambs exhibited a similar growth response until d 105, after which daily gain of the control lambs exceeded (P less than .03) that of the A-deficient lambs. Polyclonal serum IgG concentrations were greater (P less than .05) in the A-deficient lambs on d 49 to 124 and on d 151 (P less than .10). Ovalbumin-specific serum IgG concentrations tended to be greater in the control lambs throughout the primary and secondary challenge periods. Control lambs had greater titers on d 164 (P less than .07) and d 190 (P less than .03). Vitamin A status appeared to have no consistent effects on serum cortisol concentrations. Spleen weights were greater (P less than .002) in the A-deficient lambs. Lungs from 11 of 12 A-deficient lambs contained abscesses, as opposed to 1 of 12 for the control lambs. Both polyclonal and antigen-specific IgG concentrations were affected by vitamin A status. Serum cortisol concentrations did not appear to mediate this effect.     

Energy source and ionophore supplementation effects on lamb growth, carcass characteristics, visceral organ mass, diet digestibility, and nitrogen metabolism.

In Exp. 1, 72 Targhee lambs (initial BW 22.1+/-.3 kg) were used to determine the effects of energy source (alfalfa pasture vs limit-fed, all-concentrate) and ionophore addition on performance, visceral organ mass, and carcass characteristics. There were no differences (P > . 10) in ADG or gain/ feed due to ionophore supplementation. Lambs that grazed alfalfa had greater (P < .05) liver, omasum, abomasum, small intestine, cecum, and large intestine weights than did lambs fed the concentrate diet. Lambs fed the concentrate diet had greater (P < .01) hot carcass weights, larger (P < .01) loin eye areas, and greater (P < .001) dressing percentages than lambs that grazed alfalfa. In Exp. 2, lambs offered the concentrate diet had greater (P < .001) DM and OM digestibilities than lambs offered alfalfa (89.5 and 91.1 vs 72.4 and 74.2%, respectively). Apparent and true N digestibilities were greater (P < .001) for the concentrate diet than for alfalfa (90.9 and 101.7 vs 77.7 and 91.9%, respectively). Likewise, grams of N retained per day were twice as great (P < .001) with the concentrate diet than with alfalfa (14.9 vs 6.0 g/ d). The greater visceral organ mass and resulting increases in energy and protein requirements in lambs that grazed alfalfa were probably responsible for the lesser hot carcass weight and dressing percentage compared with lambs fed 100% concentrate.     

Effect of diet composition and feed intake level on diet digestibility and ruminal metabolism in growing lambs.

Lambs (29 +/- 2.5 kg) were fed three diets at various intakes to determine whether diet composition or level of intake was reflected in changes in diet digestibility or ruminal fluid characteristics. In Exp. 1, a 90% concentrated, pelleted diet or a whole shelled corn diet with a pelleted protein supplement was fed at three levels of intake: ad libitum and 92.5 and 85% of ad libitum (n = 15). Exp. 2 compared the 90% concentrate diet with diets in which the energy density was diluted to 55 or 72.5% concentrate by including alfalfa hay as a possible method of restricting energy intake (n = 6). Lambs were adapted to diets for 13 d; feces were collected for 6 d and ruminal fluid was collected 0, 3, and 6 h after feeding on the day following fecal collection. Restricting intake in Exp. 1 did not affect DM digestibility or digestibility of CP or starch. Digestibility of ADF was increased (P less than .10) by restricting intake. Ruminal fluid pH, ammonia concentration and VFA concentrations were affected little by either restricted intake level. Digestibility of DM was 4% higher (P less than .001) and starch 5% higher (P less than .001) for the whole shelled corn diet than for the pelleted, high-concentrate diet. Ruminal pH of lambs fed the whole shelled corn diet was higher and fluctuated less than the ruminal pH of lambs fed the high-concentrate, pelleted diet. In Exp. 2, diet digestibility was reduced (P less than .01) and ruminal pH was increased (P less than .002) by addition of hay. Restricted feeding of lambs did not seem to increase diet digestibility or alter ruminal conditions.     

Low-quality roughages in high-concentrate pelleted diets for sheep: digestion and metabolism of nitrogen and energy as affected by dietary fiber concentration

Two trials were conducted to evaluate effects of, and interactions between, level and source of fiber in the diet on ruminal environment, microbial protein synthesis, nutrient digestion and flow of digesta through the gastrointestinal tract of multiple-fistulated sheep (trial 1; 4 X 4 Latin square design) and on ruminal, digestive and metabolic characteristics of early-weaned lambs (trial 2; randomized complete block design; 3 periods). All diets tested were pelleted and were formulated to contain either 39% or 25% neutral detergent fiber (NDF), with corncobs or cottonseed hulls (CSH) as the major NDF (roughage) sources. In trial 1, dry-matter (DM) and organic-matter (OM) digestibilities were not different (P greater than .05) among treatments. Digestibility of NDF was higher (P less than .05) with high-fiber. Bacterial N synthesis (g N/kg OM truly digested) was not different (P greater than .05) among treatments. Molar proportion acetate was higher (P less than .05) and molar proportion propionate lower (P less than .05) when sheep were fed high-fiber diets. In trial 2, apparent DM digestibility was higher (P less than .05) for lambs fed diets containing corncobs. Energy digestibility was higher (P less than .05) at the low-fiber level and for lambs fed diets containing corncobs. Apparent NDF digestibility by lambs was higher (P less than .05) at the high-fiber level and for lambs fed diets containing corncobs. Nitrogen retained (percentage of N intake) was higher (P less than .05) for lambs fed diets containing CSH. Ruminal pH and molar proportion acetate were higher (P less than .05) and molar proportion propionate lower (P less than .05) for lambs fed high-fiber diets. Although responses to corncob vs CSH inclusion in high-energy pelleted diets differ, both roughages are effective as fiber sources in sheep diets.     

Effect of water restriction and dietary potassium on nutrient metabolism in lambs

Twenty-four Hampshire X Suffolk wether lambs (40 kg) were used in a 2 X 2 factorial arrangement of treatments to study the influence of water restriction and high levels of dietary K on nutrient utilization. Lambs were offered either a normal K diet (1.86% K) or a high K diet (3.66% K). Additionally, the lambs were offered either a normal quantity of water (previously determined voluntary intake of lambs fed normal K levels) or were restricted to a water intake 80% of normal. Each lamb received 800 g/d of a fescue hay-corn diet (77.5% fescue hay) with an additional 20 g of KCl offered to lambs on high K treatments. The experiment consisted of 14 d of adjustment and 7 d of total collection with blood and ruminal parameters measured on the last day of collection. Both acid detergent fiber digestibility and N balance were reduced (P less than .05) by high K intake. Urinary Mg excretion tended (P greater than .05) to be decreased by water restriction. Plasma Mg concentrations at 2 h post-feeding (PF) tended (P greater than .05) to be reduced by a high K intake at a normal level of water consumption but increased at high K intake when water intake was restricted. A similar pattern was observed for plasma K concentrations. Although high K intake resulted in elevated (P less than .05) ruminal K concentrations both at 2 and 6 h PF, ruminal concentrations of ammonia-N and volatile fatty acids were not affected (P greater than .05) by treatment. These data suggest that nutrient utilization in both the digestive tract and tissues is altered by level of K and modest water restriction.     

Site and extent of apparent magnesium absorption by lambs fed different sources of magnesium

Ten abomasally cannulated crossbred wether lambs (avg wt, 33 kg) were used in a replicated 5 x 5 latin square design to determine the site and extent of apparent absorption of Mg when fed different sources of Mg. Lambs were fed twice daily 220 g of chopped mixed grass hay and 180 g of a corn-based supplement (control; .13% mg, DM basis), or the control diet supplemented with Mg (.26% Mg, DM basis) from MgO, magnesium citrate (MgC), smectite-vermiculite (Mg-Mica) or MgOH. Lambs were maintained in metabolism stalls during each of the five experimental periods. Each period consisted of a 7-d dietary adjustment followed by a 3-d collection of abomasal samples, feces and urine. Abomasal contents were sampled four times daily during the 3-d collection period. The diet contained .5% chromium oxide as a digestion marker. Apparent absorption of Mg was .17, .55, .85, .78 and .82 g/d for lambs fed the control, MgO, MgC, Mg-Mica and MgOH diets, respectively. Apparent absorption of Mg (g/d) was similar (P greater than .05) in the lambs fed the supplemented diets and greater (P less than .05) than in those fed the control diet. Preintestinal absorption of Mg was .21, .57, 1.08, .14 and .92 g/d when the control, MgO, MgC, Mg-Mica and MgOH diets were fed. Lambs fed the control and Mg-Mica diets absorbed similar (P greater than .05) quantities of Mg in the preintestinal region and less (P less than .05) than lambs fed the MgO, MgC and MgOH diets.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of dietary phosphorus, soil ingestion and dietary intake level on performance, phosphorus utilization and serum and alimentary tract mineral concentrations in lambs

Two experiments were conducted with lambs fed concentrate-based diets to study the effects of dietary P and soil ingestion on performance, P utilization and mineral composition of serum and alimentary tract contents. In Exp. 1, 20 wether lambs were fed diets for 21 d in a 2 X 2 factorial arrangement of treatments with .2 or .3% total dietary P and O or 9% added Florida Ultisol (highly weathered soil with high P-fixation capacity) containing 4,600 and 6,400 mg/kg total Al and Fe, respectively. True P absorption increased (P less than .05) from 30 to 42% and from 37 to 54% when soil was added to the basal and high P diets, respectively. In Exp. 2, 24 wether lambs were assigned randomly to a 2 X 2 X 2 factorial arrangement of treatments. Lambs were fed during a 70-d period using diets described previously on either a restricted or an ad libitum basis. Soil increased Fe concentration in ruminal fluid (P less than .05) and ash percentage (P less than .001) in ruminal solids and feces. Aluminum concentration in ruminal solids and feces and Fe in ruminal solids were increased (P less than .001) by soil addition, whereas concentrations of Ca, Mg, P, Zn, Cu and Mn in ruminal solids and feces were decreased (P less than .01) by soil addition. There were time X P interactions on serum inorganic P (P less than .01) and Mg (P less than .05) concentrations. Although high in P-fixing capacity, soil fed to lambs in these experiments improved P utilization. Lambs appeared to be able to adapt to changes in intake of dietary minerals in soil, possibly through adaptation of ruminal microflora or a redistribution of body mineral pools.     

Effects of supplemental protein source and level of urea on intestinal amino acid supply and feedlot performance of lambs fed diets based on alkaline hydrogen peroxide-treated wheat straw.

Two experiments were conducted to determine the effects of supplemental CP source and level of urea on intestinal amino acid (AA) supply and feedlot performance of lambs fed diets based on alkaline hydrogen peroxide-treated wheat straw (AHPWS). In Exp. 1, five cannulated (ruminal, duodenal, and ileal) crossbred wethers (61 kg) were used in a 5 x 5 Latin square design. Treatments consisted of different sources of CP and included soybean meal (SBM), a combination of urea, distillers dried grains (DDG), and fish meal, each provided an equal portion of supplemental CP (UDF), and three levels of urea (17, 33, and 50% of supplemental CP) fed in combination with DDG (U17, U33, and U50). Organic matter and N digestibilities decreased (P less than .05) when lambs were fed U17 compared with those fed SBM. There were no differences (P greater than .05) in bacterial N or AA flows to the duodenum due to CP source despite large differences in ruminal NH3 N concentrations and lower ruminal OM digestion when lambs were fed U17. Duodenal nonbacterial N and AA flows were highest (P less than .05) in lambs fed U17 and UDF and lowest when lambs were fed U50 and SBM. Lysine concentration in duodenal digesta decreased with incremental increases in DDG. In Exp. 2, 30 individually penned ram lambs (33 kg) were allotted to five CP treatments in a randomized complete block design. Treatments were similar to those of Exp. 1, with the exception that U17 was replaced by a 14% CP diet with SBM as the supplemental CP source; all other diets were formulated to contain 12% CP. Lambs fed U50 had decreased (P less than .08) ADG and gain/feed compared with all other treatments, and lambs fed UDF had greater (P less than .05) ADG and gain/feed than lambs fed U33. It was concluded that 17% of the supplemental CP from urea seems adequate to maximize bacterial protein synthesis and that no more than 33% of the supplemental CP should be provided by urea in diets based on AHPWS. Feeding a combination of ruminally resistant protein sources with complementary AA profiles of lysine and methionine (UDF) may enhance quality of protein entering the duodenum and feedlot performance.     

Influence of dietary palm oil supplementation on serum lipid metabolites, carcass characteristics, and lipid composition of carcass tissues of growing ram and ewe lambs.

The objective of this research was to determine the influence of dietary palm oil supplementation on carcass characteristics and lipid composition of tissues from growing lambs. Twenty-eight Suffolk x Hampshire lambs were weaned at 60 d of age (average 36 kg BW) and assigned to a 2 x 2 factorial arrangement consisting of diet (control [NPO] or 10.6% added dietary palm oil [PO]) and sex (ram vs ewe). The NPO diet (77% forage and 23% concentrate) contained 11.2% CP and 2.66 Mcal of ME/kg. Palm oil replaced molasses in the PO diet. Lambs were individually given ad libitum access to feed for 60 d to a final BW average of 50.1 kg. Lipid composition of the longissimus muscle and corresponding subcutaneous (s.c.) adipose tissue was determined by gas-liquid chromatography (GLC). Lambs fed PO were fatter (P less than .01) than lambs fed NPO (.77 vs .56 cm, s.c. fat). Diet had no effect on cholesterol content of lean tissue; however, feeding PO increased the saturated fatty acids of lean tissue. The s.c. fat from lambs fed PO had less (P less than .01) cholesterol (64.79 vs 89.67 mg/100 g) and more saturated fatty acids than that from lambs fed NPO. Ewes were fatter (P less than .01) than rams, yet they had less cholesterol content in the s.c. adipose tissue (68.71 vs 85.74 mg/100 g). High amounts of dietary palm oil fed to growing lambs caused changes in fatty acid deposition and cholesterol metabolism and may be a useful investigative tool to study lipid metabolism in growing ruminants.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of water restriction and dietary sodium on nutrient metabolism in lambs

Twenty-four Hampshire X Suffolk wether lambs (40 kg) were used in 2 X 2 factorial arrangement of treatments to study the influence of water restriction and high levels of dietary Na on nutrient utilization. Lambs were offered either a normal Na diet (.20% Na) or a high Na diet (1.77% Na). Additionally, the lambs were offered either a normal quantity of water (previously determined voluntary intake of lambs fed normal Na levels) or were restricted to a water intake 80% of normal. Each lamb received 800 g/d of a hay-corn diet (77.5% fescue hay) with an additional 38 g of NaCl offered to lambs on high Na treatments. The complete experiment consisted of 14 d of adjustment and 7 d of total collection with blood and ruminal characteristics measured on the last day of the collection period. A high Na intake decreased (P less than .05) the apparent digestibility of neutral detergent fiber, but tended to increase the apparent absorption of Mg. Plasma urea N concentrations were not affected (P greater than .05) by level of Na or water intake. Plasma Na and K concentrations were not affected (P greater than .05) by treatment regimen. A high Na intake increased (P less than .05) plasma Mg concentrations at 6 h post-feeding with a normal level of water intake, but decreased (P less than .05) Mg concentrations at 6 h with restricted water intake. Ruminal ammonia N and K concentrations at 2 h post-feeding were decreased (P less than .05) by a high level of dietary Na. Ruminal Na concentration was not affected (P greater than .05) by treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of monensin on monovalent ion metabolism and tissue concentrations in lambs

A study consisting of two trials was conducted to determine the effects of monensin on the apparent absorption and retention of sodium (Na) and potassium (K) and to examine changes in tissue and ruminal fluid concentrations of these minerals in lambs. Eight lambs (39 kg) were used in trial 1 and 10 lambs (37 kg) were used in trial 2. Animals were used in randomized block designs, blocked by weight, and fed a high concentrate diet with or without 20 mg/kg monensin. Trials began with a dietary adjustment period lasting 18 d in trial 1 and 21 d in trial 2. Animals were then placed in metabolism stalls for a 10-d stall adjustment period followed by a 12-d collection period. Collections for mineral balance were made during the first 10 d of the collection period. Blood and ruminal fluid samples were obtained on d 11 of the collection period. Lambs were slaughtered on d 12 of the collection period and tissue samples were collected. Sodium retention decreased (P less than .05) 86.2% when monensin was fed. Apparent K absorption increased (P less than .05) 16.7%, while K retention increased (P less than .10) 52.6% when monensin was fed. In lambs fed monensin, ileal Na decreased (P less than .10) 13.8%. These results indicate that dietary monensin alters the metabolism of Na and K in lambs.     

Nutrient utilization in lambs fed diets high in sodium or potassium

Twenty-four wether lambs averaging 47 kg were used to study the effects of dietary K and Na additions on metabolism of lambs. Lambs were randomly allotted to four treatments and fed 900 g/d of the following: control diet consisting of 50% ground tall fescue hay and 50% concentrate; K diet calculated to contain 4% K with K added as KCl; Na diet calculated to contain 4% Na with Na added as NaCl, and K-Na diet containing 2% K and 2% Na with K and Na added from the same sources as in the K and Na diets. Water intake and urine excretion were highest for lambs fed the Na diet. Dry matter (DM) and crude protein (CP) digestibilities were similar among treatments. The K-Na diet resulted in decreased (P less than .05) acid detergent fiber (ADF) digestibility compared with lambs fed the Na diet. Nitrogen (N) retention was highest (P less than .05) in lambs fed the K diet and lowest in those fed the Na diet. Rumen NH3-N was lower (P less than .05) in lambs fed the Na diet compared with controls. Rumen K at 2 and 6 h postfeeding was highest (P less than .05) and rumen Na at 6 h lowest (P less than .05) for lambs fed the K diet. Plasma K values at both sampling times were highest (P less than .05) in lambs fed the K diet. At 6 h postfeeding, plasma Mg was higher in control lambs compared with those fed the K-Na diet.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of postfast dietary crude protein and phosphorus content on nitrogen, phosphorus, calcium, and magnesium repletion in sheep.

An experiment was conducted to determine the influence of postfast dietary CP and P concentration on the repletion of N, P, Ca, and Mg lost during a 3-d fast in sheep. Four Suffolk wether lambs averaging 35 kg were used in a 4 x 4 Latin square design. Lambs were fed a control diet (700 g/d; as-fed basis) for 14 d and were then deprived of feed and water for 3 d. Lambs were then fed one of four isoenergetic realimentation diets: 1) low CP/low P, 2) low CP/high P, 3) high CP/high P, and 4) high CP/very high P. Realimentation N and Mg intakes were 9.8 and 1.1 g/d for lambs fed the low-CP diet and 18.1 and 1.7 g/d for lambs fed the high-CP diets, respectively. Realimentation P intakes were 1.40, 2.36, 2.66, and 3.82 g/d for lambs fed Diets 1, 2, 3, and 4, respectively. Nitrogen, P, Ca, and Mg apparent digestibility and balance and serum urea N, free fatty acids, P, Ca, Mg, and alkaline phosphatase were determined during the prefast, fast, and realimentation periods. Lambs fed the high-CP diets had higher (P less than .05) N and P digestibility and balance than lambs fed the low-CP diet. Increasing the dietary P content did not affect (P greater than .15) P balance or digestibility. In general, the realimentation diet fed did not affect (P greater than .15) serum concentrations of free fatty acids, alkaline phosphatase, inorganic P, Ca, or Mg.     

Effects of supplemental ruminally degradable protein versus increasing amounts of supplemental ruminally undegradable protein on site and extent of digestion and ruminal characteristics in lambs fed low-quality forage

Four ruminally and duodenally cannulated Suffolk wether lambs (34.5 +/- 2 kg initial BW) were used in a 4 x 4 Latin square designed experiment to compare effects of supplemental ruminally degradable protein (RDP) vs. increasing amounts of supplemental ruminally undegradable protein (RUP) on ruminal characteristics and site and extent of digestion in lambs. Lambs were fed a basal diet of crested wheatgrass hay (4.2% CP) for ad libitum consumption, plus 1 of 4 protein supplements: isolated soy protein (RDP source) fed to meet estimated RDP requirements assuming a microbial efficiency of 11% of TDN (CON) or corn gluten meal (RUP source) fed at 50, 100, or 150% of the supplemental N provided by CON (C50, C100, and C150, respectively). Neither NDF nor ADF intake was affected (P >/= 0.18) by protein degradability, but they increased or tended to increase (P /= 0.26) for CON and C100, but increased (P /= 0.33) by protein degradability. However, true ruminal N digestibility was greater (P = 0.03) for CON compared with C100. Ruminal ammonia concentrations were greater (P = 0.002) for CON compared with C100 lambs, and increased (P = 0.001) with increasing RUP. Microbial N flows were not affected (P >/= 0.12) by protein degradability or increasing RUP. Likewise, neither ruminal urease activity (P >/= 0.11) nor microbial efficiency (P >/= 0.50) were affected by protein degradability or level of RUP. Total tract OM, NDF, and ADF digestibility was greater (P 相似文献