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Mature Angus-cross beef cows (n = 144) were used to determine effects of late gestation dietary energy source on pre- and postpartum cow performance in a complete randomized block design experiment. Cows were adapted to diets starting at 167 [+ or -] 9 d of gestation and fed until 1 wk before expected calving date. Cows were fed 1 of 3 dietary energy sources: grass hay (HY), corn (CN), or dried distillers grains (DDGS). Cows allotted to HY were allowed ad libitum access to round-bale grass hay, and average hay disappearance was 12.4 kg/d. Limit-fed corn and DDGS diets contained 5.3 kg of whole-shelled corn or 4.1 kg of DDGS, respectively, plus 2.1 kg of hay, and 1.0 kg of supplement to meet cow nutritional needs during late gestation and to allow for an energy intake similar to HY. Every 21 d, BW, BCS, and ultrasound measurement of backfat between the 12th and 13th ribs were collected. At 210 d in gestation, jugular blood samples were collected from cows at 0, 3, 6, and 9 h postfeeding and were analyzed for glucose, insulin, NEFA, and blood urea N (BUN) concentrations. After parturition, cows were fed a common diet and managed similarly. Milk production was determined by weigh-suckle-weigh procedure on d 31, 100, and 176 postpartum. Cows fed DDGS during late gestation gained more (P = 0.04) BW than cows fed HY or CN; however, no difference in BCS change was detected (P = 0.28) among treatments. Plasma glucose concentrations were similar among treatments (P = 0.64), whereas insulin concentrations at 3 h postfeeding were greater (P = 0.002) for cows fed DDGS than those fed HY or CN. Plasma BUN concentrations were greater (P [less than or equal to] 0.02) for cows fed DDGS vs. CN or HY up to 6 h postfeeding. Birth weight was greater (P < 0.001) for calves from cows fed CN and DDGS than for those fed HY, but this did not result in any differences in frequency of dystocia (P = 0.21). Prepartum energy source did not affect conception rates (P = 0.79), milk production (P [greater than or equal to] 0.51), or milk composition (P [greater than or equal to] 0.39). Maternal dietary energy source in late gestation did not affect pre- or postpartum cow performance, but did change plasma hormones and metabolites during gestation. Heavier birth weights in calves from cows fed CN or DDGS indicate the changes in maternal metabolism affected energy partitioning of nutrients to the fetus and subsequent fetal growth. Key words: beef cattle, maternal nutrition, prepartum energy source, reproduction doi: 10.2527/jas.2009-2744

The objectives of the present study were 1) to evaluate the effects of supplemental fat and ME intake on plasma concentrations of glucagon-like peptide-1 (GLP-1), cholecystokinin (CCK), glucose-dependent insulinotropic polypeptide, ghrelin, and oxyntomodulin; and 2) to determine the association of these peptides with DMI and the hypothalamic concentration of mRNA for the following neuropeptides: neuropeptide Y (NPY), agouti-related peptide (AgRP), and proopiomelanocortin (POMC). In a completely randomized block design with a 2 x 2 factorial arrangement of treatments, 32 pens with 2 wethers each were restricted-fed (2.45 Mcal/lamb per day) or offered diets ad libitum (n = 16) with or without 6% supplemental fat (n = 16) for a period of 30 d. Dry matter intake was measured daily. On d 8, 15, 22, and 29, BW was measured before feeding, and 6 h after feeding, blood samples were collected for plasma measurement of insulin, GLP-1, CCK, ghrelin, glucose-dependent insulinotropic polypeptide, oxyntomodulin, glucose, and NEFA concentrations. On d 29, blood was collected 30 rain before feeding for the same hormone and metabolite analyses. At the end of the experiment, wethers were slaughtered and the hypothalami were collected to measure concentrations of NPY, AgRP, and POMC mRNA. Offering feed ad libitum (resulting in greater ME intake) increased plasma insulin and NEFA concentrations (P = 0.02 and 0.02, respectively) and decreased hypothalamic mRNA expression of NPY and AgRP (P = 0.07 and 0.02, respectively) compared with the restricted-fed wethers. There was a trend for the addition of dietary fat to decrease DMI (P = 0.12). Addition of dietary fat decreased insulin and glucose concentrations (P < 0.05 and 0.01, respectively) and tended to increase hypothalamic mRNA concentrations for NPY and AgRP (P = 0.07 and 0.11, respectively). Plasma GLP-1 and CCK concentrations increased in wethers offered feed ad libitum compared with restricted-fed wethers, but the response was greater when wethers were offered feed ad libitum and had supplemental fat in the diet (fat x intake interaction, P = 0.04). The prefeeding plasma ghrelin concentration was greater in restricted-fed wethers compared with those offered feed ad libitum, but the concentrations were similar 6 h after feeding (intake x time interaction, P < 0.01). Supplemental dietary fat did not affect (P = 0.22) plasma ghrelin concentration. We conclude that insulin, ghrelin, CCK, and GLP-1 may regulate DMI in sheep by regulating the hypothalamic gene expression of NPY, AgRP, and POMC. Key words: agouti-related peptide, gut peptide, insulin, intake, neuropeptide Y, sheep doi: 10.2527/jas.2009-2316

Lambs (n = 48) were used in a 2 x 2 factorial arrangement of treatments to evaluate effects of inclusion of oil containing PUFA in high-concentrate diets (with or without) and duration of oil supplementation (pre- vs. postweaning) on CLA concentration of muscle and adipose tissue. Lambs were fed preweaning creep diets (with or without oil) corresponding to the dietary lactation treatment diet (with or without oil) of the dam. Dams blocked by lambing date and rearing type were randomly assigned to 1 of 2 lactation dietary treatments with or without oil supplementation. Creep diets contained approximately 70% concentrate and 30% roughage and were provided to lambs for ad libitum intake. At weaning (58.7 [+ or -] 2.5 d of age), lambs (n = 48) were randomly assigned within preweaning treatment groups to 1 of 2 postweaning dietary treatments (with or without oil) and 16 pens in a randomized block design, blocked by sex and BW. Postweaning diets were formulated to contain approximately 80% concentrate and 20% roughage and were fed once daily for ad libitum intake. Soybean and linseed oil (2:1, respectively) replaced ground corn and provided 3% additional fat in pre- and postweaning diets. Lambs were slaughtered at 60.3 [+ or -] 4.2 kg of BW. A subcutaneous fat (SQ) sample was obtained within 1 h postmortem and a LM sample at the 12th rib was obtained 24 h postmortem, and both were analyzed for fatty acid profile. Feedlot performance and carcass measurements were not affected (P [greater than or equal to] 0.26) by oil supplementation. Total CLA content of LM and SQ was not affected (P [greater than or equal to] 0.08) by oil supplementation pre- or postweaning, but trans-10, cis-12 CLA was greater (P = 0.02) in SQ from lambs supplemented with oil postweaning. Total PUFA content in LM was greater (P = 0.02) in lambs supplemented with oil pre- or postweaning as a result of increased concentrations of 18:2cis-9, cis-12 and longer chain PUFA. Conversely, pre- and postweaning oil supplementation resulted in less (P = 0.04) MUFA content in LM. Only postweaning oil supplementation increased (P = 0.001) SQ PUFA content. Feeding oils containing PUFA to lambs pre- and postweaning did not increase CLA content of muscle, whereas postweaning oil supplementation minimally increased CLA concentration of SQ fat. Inclusion of soybean and linseed oil in preand postweaning diets increased total PUFA content of SQ fat and muscle tissue without adversely affecting growth performance or carcass characteristics. Key words: conjugated linoleic acid, fatty acid, lamb, polyunsaturated fatty acid doi: 10.2527/jas.2009-2059

Wagyu-sired (n = 20) and Angus-sired (n = 19) steers and heifers were used to compare the effects of sire breed on feedlot performance, carcass characteristics, and meat tenderness. Calves were weaned at 138 [+ or -] 5 d of age and individually fed a finishing diet consisting of 65% whole corn, 20% protein/vitamin/mineral supplement, and 15% corn silage on a DM basis. Heifers and steers were slaughtered at 535 and 560 kg of BW, respectively. Carcasses were ribbed between the 12th and 13th (USDA grading system) and the 6th and 7th ribs (Japanese grading system) to measure fat thickness, LM area (LMA), and intramuscular fat (IMF). Two steaks were removed from the 12th rib location and aged for 72 h and 14 d to determine Warner-Bratzler shear force and cooking loss. Sire breed x sex interactions were not significant (P > 0.05). Angus-sired calves had greater (P < 0.05) ADG and DMI than Wagyu. Wagyu-sired calves had improved (P < 0.05) feed efficiency than Angus. Sire breed did not affect (P > 0.20) HCW, 12th-rib fat, or USDA yield grade. Carcasses of Wagyu had greater (P = 0.0001) marbling scores at the 12th rib than those of Angus (770.9 vs. 597.3 [+ or -] 41.01, respectively). Carcasses of Wagyu also had greater (P < 0.02) 12th-rib IMF and 6th-rib IMF than Angus, resulting in a greater proportion of carcasses grading Prime (65.0 vs. 21.1%; P = 0.006). Carcasses from Wagyu tended (P = 0.08) to have greater LMA at the 12th rib, whereas Angus carcasses had greater (P < 0.05) LMA at the 6th rib. Steaks from Angus and Wagyu had similar (P > 0.50) tenderness at aging times of 72 h and 14 d. Cooking loss was greater (P < 0.01) for Angus than Wagyu steaks at 72 h and 14 d. Using Wagyu sires vs. Angus sires on British-based commercial cows combined with early weaning management strategies has the potential to produce a product with greater marbling, but is unlikely to significantly enhance tenderness. Key words: Angus, meat quality, Wagyu

Sixty-eight Angus-based steers (224 [+ or -] 7.6 kg of BW) were used to evaluate the effects of a prolonged dietary vitamin A restriction on marbling and immunocompetency. Steers were allotted randomly to 1 of 2 treatments: LOW (no supplemental vitamin A) and HIGH (diet supplemented with 2,200 IU of vitamin A/kg of DM). Diets contained 60% high-moisture corn, 20% roasted soybeans, 10% corn silage, and 10% of a protein supplement. Steers were penned and fed individually. For the first 141 d, steers were program-fed to achieve a gain of 1.1 kg/d. The last 75 d of the experiment, steers were offered feed for ad libitum intake. At slaughter, serum and liver samples were taken to determine their retinol content. To evaluate immuno-competency, 10 steers per treatment were selected randomly on d 141 and received an ovalbumen vaccine, and 21 d later, the steers were revaccinated. On d 182, blood samples were taken from the vaccinated steers to determine serum antibody titers by ELISA. Steers were slaughtered after 216 d on feed. Carcass characteristics were determined, and LM samples were taken for composition analysis. Subcutaneous fat samples were taken for fatty acid composition analysis. Performance (ADG, DMI, and G:F) was not affected by vitamin A restriction (all P > 0.10). Hot carcass weight, 12th-rib fat, and yield grade did not differ between LOW and HIGH steers (all P > 0.10). Marbling score (LOW = 574 vs. HIGH = 568, P = 0.79) and i.m. fat (LOW = 5.0 vs. HIGH = 4.7% ether-extractable fat, P = 0.57) were not increased by vitamin A restriction. Serum (LOW = 18.7 vs. HIGH = 35.7 [micro]g/dL, P < 0.01) and liver (LOW = 6.3 vs. HIGH = 38.1 [micro]g/g, P < 0.01) retinol levels were lower in LOW steers compared with HIGH steers at slaughter. Response to ovalbumin vaccination was not affected by vitamin A restriction (LOW = 13.1 vs. HIGH = 12.8 [log.sub.2] titers, P = 0.60). Slight changes in the fatty acid profile of s.c. fat of the steers were detected. A greater proportion of MUFA (LOW = 41.7 vs. HIGH = 39.9%, P = 0.03) and fewer SFA (LOW = 47.1 vs. 48.7, P = 0.03) were observed in vitamin A-restricted steers. This suggests that vitamin A restriction may affect the activity of desaturase enzyme (desaturase activity index, LOW = 46.9 vs. HIGH = 44.9, P = 0.01). Feeding a low vitamin A diet for 216 d to Angus-based steers did not affect performance, marbling score, or animal health and immunocompetency. Slight changes in the fatty acid profile of s.c. fat were observed, suggesting that vitamin A restriction may have affected desaturase enzyme activity. Key words: beef, immunity, marbling, vitamin A

Angus-cross steers (n = 165; 295 [+ or -] 16 kg of BW) were used evaluate the effect of low vitamin A diets with high-moisture corn (HMC) of dry corn (DC) on marbling and fatty acid composition. Steers were allotted to 24 pens (7 steers/pen), such that each pen had the same average initial BW. Treatments were randomly allotted to the pens. The experiment had a completely randomized design, with a 2 x 2 factorial arrangement of treatments: low vitamin A (Lo, no supplemental vitamin A) and HMC (LoHMC); LoDC; high vitamin A (Hi, supplemented with 2,200 IU of vitamin A/kg of DM) and HMC (HiHMC); and HiDC. Diets contained 76% corn, 10% corn silage, 11% protein supplement, and 3% soybean oil (DM basis). Samples of feed ingredients were collected for carotenoid analysis. Blood samples were collected for serum retinol determination. Steers were slaughtered after 145 d on feed. Carcass characteristics and LM composition were determined. Samples from the s.c. fat depot were analyzed for fatty acid composition. High-moisture corn had a greater vitamin A content, based on its carotenoid content, than DC (614 vs. 366 IU/kg of DM, P < 0.01). No vitamin A x corn type interactions were detected for feedlot performance, carcass characteristics, or serum, s.c. fat, or liver retinol concentration. Average daily gain, DMI, and G:F were not affected by vitamin A (P > 0.05). Marbling score and USDA quality grade were greater (P < 0.05) in Lo vs. Hi steers. Hot carcass weight, backfat, and yield grade were not affected by the treatments (P > 0.05). Vitamin A and corn type did not affect LM composition (DM, ash, CP, of ether-extractable fat, P > 0.05). Vitamin A supplementation increased (P < 0.06) serum retinol on d 112 and 145 and increased (P < 0.01) liver retinol at slaughter (Lo = 38.7 vs. Hi = 102.9 [micro]g/g). The s.c. fat retinol concentrations were less (P < 0.01) for Lo (0.8 [micro]g/g) than for Hi (1.4 [micro]g/g) at slaughter. Cell diameter of adipocytes in the i.m. depot was not affected by dietary vitamin A (P > 0.05). A vitamin A x corn type interaction was observed (P < 0.05) for the s.c. fat cellularity. Feeding HMC increased the number of cells per square millimeter when Lo diets were fed (LoHMC = 128 vs. LoDC = 100 cells/[mm.sup.2], P < 0.05), but not when Hi diets were fed (HiHMC = 109 vs. HiDC = 111 cells/[mm.sup.2], P > 0.05). The CLA content of adipose tissue was not affected by the treatments. Regardless of the corn type used, feeding low vitamin A diets for 145 d to Angus-cross steers increased marbling and quality grade without affecting yield grade, animal health, or performance. Key words: beef, corn, marbling, vitamin A

To determine the effect of duration of dietary vitamin A restriction on site of fat deposition in growing cattle, 60 Holstein steers (BW = 218.4 [+ or -] 6.55 kg) were fed a diet based on high-moisture corn, with 2,200 IU of supplemental vitamin A/kg of DM (control) or no supplemental vitamin A for a long (243 d; LR) or short (131 d; SR) restriction before slaughter at 243 d. The SR steers were fed the control diet for the first 112 d. Steers were penned individually and fed for ad libitum intake. Jugular vein blood samples for serum retinol analysis were collected on d 1, 112, and 243. Carcass samples were collected for composition analysis. Subcutaneous fat samples were collected for fatty acid composition. Fat samples from the i.m. and s.c. depots were collected to measure adipocyte size and density. Feedlot performance (ADG, DMI, and G:F) was not affected (P > 0.05) by vitamin A restriction. On d 243, the i.m. fat content of the LM was 33% greater (P < 0.05) for LR than for SR and control steers (5.6 vs. 3.9 and 4.2% ether extract, respectively). Depth of backfat and KPH percentage were not affected (P = 0.44 and 0.80, respectively) by vitamin A restriction. Carcass weight, composition of edible carcass, and yield grade were similar among treatments (P > 0.10). Liver retinol (LR = 6.1, SR = 6.5, and control = 44.7 [micro]g/g; P < 0.01) was reduced in LR and SR vs. control steers. On d 243, LR and SR steers had similar serum retinol concentrations, and these were lower (P < 0.01) than those of control steers (LR = 21.2, SR = 25.2, and control = 36.9 [micro]g/dL). Intramuscular adipose cellularity (adipocytes/ [mm.sup.2] and mean adipocyte diameter) on d 112 and 243 was not affected (P > 0.10) by vitamin A restriction. Restricting vitamin A intake for 243 d increased i.m. fat percentage without affecting s.c. or visceral fat deposition, feedlot performance, or carcass weight. Restricting vitamin A intake for 131 d at the end of the finishing period appears to be insufficient to affect the site of fat deposition in Holstein steers. Key words: Holstein, vitamin A, marbling

A feedlot trial was conducted to determine the effect of dietary vitamin A concentration and roasted soybean (SB) inclusion on carcass characteristics, adipose tissue cellularity, and muscle fatty acid composition. Angus-crossbred steers (n = 168; 295 [+ or -] 1.8 kg) were allotted to 24 pens (7 steers each). Four treatments, in a 2 x 2 factorial arrangement, were investigated: no supplemental vitamin A, no roasted soybeans (NANS); no vitamin A, roasted SB (20% of the diet on a DM basis; NASB); with supplemental (2,700 IU/kg) vitamin A, no roasted SB (WANS); and with supplemental vitamin A, roasted SB (WASB). Diets included high moisture corn, 5% corn silage, 10 to 20% supplement, and 20% roasted SB in the SB treatments on a DM basis. The calculated vitamin A concentration in the basal diet was 0.10) for cattle performance, carcass composition, or muscle fatty acid composition. Low vitamin A diets (NA) did not affect (P > 0.05) ADG, DMI, or G:F. Quality grade tended (P = 0.07) to be greater in NA steers. Marbling scores and the percentage of carcasses grading [greater than or equal to] [Choice.sup.-] were 10% greater for NA steers, although these trends were not significant (P = 0.11 and 0.13, respectively). Backfat thickness and yield grade were not affected (P > 0.26) by vitamin A supplementation. Composition of the LM was not affected (P > 0.15) by vitamin A or SB supplementation. Serum retinol at slaughter was 44% lower (P < 0.01) for steers fed NA than for steers supplemented with vitamin A (23.0 vs. 41.1 [micro]g/dL). A vitamin A x SB interaction occurred (P < 0.05) for adipose cellularity in the i.m. depot; when no SB was fed, vitamin A supplementation decreased cell density and increased cell size. However, when SB was fed, vitamin A supplementation did not affect adipose cellularity. Adipose cellularity at the s.c. depot was not affected (P > 0.18) by vitamin A or SB treatments. Fatty acid profile of the LM was not affected by vitamin A (P > 0.05), but SB increased (P < 0.05) PUFA (7.88 vs. 4.30 g/100 g). It was concluded that feeding NA tended to increase marbling without affecting backfat and yield grade. It appeared that NA induced hyperplasia in the i.m. but not in the s.c. fat depot. Key words: beef, marbling, roasted soybean, vitamin A

Targhee x Hampshire lambs (average BW 24 [+ or -] 1 kg) were used to determine the effect of finishing on concentrate or by grazing ryegrass forage on slaughter weights of 52 kg (N) or 77 kg (H) on tissue accretion and lamb wholesale cutout. When fed to similar slaughter weights, the wholesale cuts of concentrate-fed lambs were heavier (P < 0.05) than the same cuts from forage-fed lambs; however, when expressed as a percentage of side weight, carcasses of forage-fed lambs had a higher (P < 0.001) percentage of leg than concentrate-fed lambs. Increasing slaughter weight from 52 to 77 kg resulted in a l-kg increase in loin weight for lambs finished on concentrate and a 0.60-kg increase for lambs finished on forage (diet x slaughter weight, P < 0.03); however, the increased loin weight for lambs finished on concentrate was due largely to increased fat deposition. For lambs slaughtered at 77 kg, those finished on forage had more lean mass in the leg, loin, rack, and shoulder than those finished on concentrate, but lean mass in these cuts did not differ between diets for lambs slaughtered at 52 kg (diet x slaughter weight, P < 0.01). At the normal slaughter weight (52 kg), concentrate-fed lambs had 50% more dissectible fat than forage-fed lambs, whereas at the heavy slaughter weight, a 79% greater amount of dissectible fat was observed for concentrate- vs. forage-fed lambs (diet x slaughter weight, P < 0.001). Lean and fat accretion rates were higher (P < 0.001) for concentrate-fed lambs than for forage-fed lambs. The lean-to-fat ratio of forage-fed lambs was higher (P < 0.001) than that of concentrate-fed lambs; however, forage finishing decreased accretion rates of all tissues compared with concentrate feeding, and these differences between forage and concentrate feeding were magnified at heavier slaughter weights. Key Words: Carcass, Concentrate, Fat, Forage, Lambs, Lean

Three experiments were conducted to determine the effects of cattle age and dietary forage level on the utilization of corn fed whole or ground to feedlot cattle. In Exp. 1, 16 steers were used to investigate the effects of cattle age and corn processing on diet digestibility. Two cattle age categories were evaluated (weanling [254 [+ or -] 20 kg BW] and yearling [477 [+ or -] 29 kg BW]; eight steers per group), and corn was fed either ground or whole to each cattle age category. Cattle age and corn processing did not affect (P > 0.10) diet digestibility of DM, OM, starch, CP, NDF or ADF, and no interactions (P > 0.10) between these two factors were detected. In Exp. 2, the effects of forage level and corn processing on feedlot performance and carcass characteristics were evaluated. One hundred eighty steers (310 [+ or -] 40 kg BW) were allotted to 24 pens, and were fed one of the following diets: high-forage (18.2% corn silage) cracked corn (HFCC); high-forage shifting corn (whole corn for the first half of the trial, then cracked corn until harvest; HFSC); high-forage whole corn (HFWC); low-forage (5.2% corn silage) cracked corn (LFCC); low-forage shifting corn (LFSC); and low-forage whole corn (LFWC). For the high-fbrage diets, steers fed cracked corn had 7% greater DMI than those fed whole corn, whereas for the low-forage diets, grain processing did not affect DMI (interaction; P = 0.02). No interactions (P > 0.10) between forage level and corn processing were found for ADG and G:F. Total trial ADG and G:F, and percentage of carcasses grading USDA Choice, and carcass yield grade were not affected (P > 0.10) by corn processing. Cattle with fewer days on feed grew faster and more efficiently when cracked corn was fed, whereas cattle with longer days on feed had greater ADG and G:F when corn was fed whole (interaction; P < 0.10). In Exp. 3, the effects of forage level and corn processing on diet digestibility were evaluated. The high-forage cracked corn, high-forage whole corn, low-forage cracked corn, and low-forage whole corn diets used in Exp. 2 were fed to 16 steers (350 [+ or -] 27 kg BW) in a digestion trial. No interactions (P > 0.10) between forage level and corn processing were detected for starch digestibility. Forage level and corn processing (grinding) did not affect (P > 0.10) diet DM, OM, starch, CP, and NDF digestibility. Processing corn did not provide additional benefits to feedlot cattle performance under these experimental conditions. Key Words: Age, Beef Cattle, Corn Processing, Feedlot, Forage

The objectives of this study were to determine the effects of finishing lambs on concentrate (C) or by grazing ryegrass forage (F) to slaughter end weights of 52 (N) or 77 kg (H) on carcass characteristics and organoleptic properties. This experiment included 64 Targhee x Hampshire lambs (average BW = 24 [+ or -] 1 kg) in a 2 x 2 x 2 factorial arrangement of treatments to compare wethers vs. ewes, C vs. F, and N vs. H slaughter weights. No interactions (P > 0.10) were observed between gender and other main effects. Hot carcass weight and dressing percent were greater (P < 0.001) for C- than for F-fed lambs. Backfat thickness also was greater (P < 0.001) for lambs fed C than for those fed F. Moreover, USDA lean quality score and USDA yield grades were higher (P < 0.001) for C- than for F-fed lambs, as well as for lambs slaughtered at H vs. N market weights. There was a higher (P < 0.005) incidence of off odors and off flavors in cooked muscle from F- vs. C-fed lambs, and also from H vs. N slaughter-weight lambs. The heavy C-fed lambs had juicier (P < 0.001) meat than other treatment combinations. Cooked meat from C-fed lambs received higher (P < 0.001) overall acceptability scores. Concentrate-finished lambs produced fatter carcasses and more palatable meat than forage-finished lambs; however, forage finishing allowed for slaughter at heavier weights without excessive fat deposition. Key Words: Carcass, Concentrate-Finished, Fat, Forage-Finished, Lamb, Palatability

One hundred eighty-four Angus x Siremental steers (initial BW 161.7 [+ or -] 3.4 kg) were used to determine whether different sources and amounts of energy in the growing phase could extend the growth curve and maintain high amounts of intramuscular fat deposition in early-weaned steers. Steers were allotted by source, age, and BW to one of four growing-phase (119 to 259 d of age) regimens. For three regimens, steers were weaned at 119 d of age and either 1) fed (DM basis) a 50% grain diet ad libitum (ALC); 2) limit-fed a 70% grain diet to achieve a gain of 0.8 kg/d from 119 to 192 d of age, and 1.2 kg/d from 193 to 259 d of age (LFC); or 3) fed a 60% haylage diet ad libitum from 119 to 192 d of age, and a 25% haylage diet ad libitum from 193 to 259 d of age (ALF). For the fourth regimen, steers were normal-weaned at 204 d of age and fed a silage diet from 205 to 259 d of age (NW). From 260 d of age to slaughter, all steers consumed a 70% grain (DM basis) diet. Limit-fed and ALF steers spent the most, and NW the least amount of time (P < 0.01) in the feedlot to achieve a target fat depth of 1.27 cm. Ad libitum-fed steers were the youngest (331 d), and NW the oldest (383 d) at slaughter (P < 0.01). Overall ADG was greatest for ALC and least for NW steers (P < 0.01). Overall, ALF steers consumed the most DM (P < 0.01). While in the feedlot, LFC and ALC steers were more efficient in converting feed to BW gain (P < 0.01) than ALF and NW steers. Normal-weaned had the least and ALC the greatest (P < 0.01) fat depth at 260 d of age. Consequently, NW steers produced the heaviest, and ALC the lightest (P < 0.01) carcasses at slaughter. Normal-weaned steers had the largest, and ALC and LFC steers had the smallest longissimus muscle area (P < 0.06). Growing phase dietary treatments did not affect (P > 0.20) yield grade. Marbling score did not differ (P > 0.35), but laboratory analysis revealed that ALC steers had the lowest percentage of fat (P < 0.02) in the longissimus muscle. Shear force was greatest (P < 0.08) for steaks from ALC and LFC steers, and least for steaks from ALF and NW steers. Feeding steers the ALC diet from 119 to 260 d of age hastened physiological maturity, decreased marbling scores, and decreased muscle tenderness compared with forage feeding (ALF, NW). Limit-feeding a high-grain diet also hastened physiological maturity and decreased muscle tenderness but did not decrease marbling scores. Source and amount of energy affected partitioning of fat deposition. Key Words: Beef Cattle, Early Weaning, Limit-Feeding, Marbling

Seventy-three Holstein steers (initial BW 138.5 [+ or -] 4.3 kg; approximately 3 mo of age) were allotted by BW to one of three growing-phase treatments to determine the effect of source and amount of energy on feedlot performance, and characteristics of subcutaneous (s.c.) and intramuscular (i.m.) adipose tissue. Treatment diets were 1) high concentrate fed ad libitum (ALC); 2) high forage fed ad libitum for 55 d, then a mid-level forage diet fed ad libitum for 98 d (ALF); or 3) limit-fed high concentrate to achieve a gain of 0.8 kg/d for 55 d, then to achieve a gain of 1.2 kg/d for 98 d (LFC). All steers were fed the ALC diet from d 154 to slaughter. Eight steers per treatment were selected after an average of 145 and 334 d on feed for determination of adipocyte cellularity and lipogenic enzyme activity at the end of the growing and finishing phases, respectively. Remaining steers were slaughtered after an average of 334 d on feed. At initial slaughter, ALC steers had a two- to threefold greater (P < 0.05) s.c. fat depth, and 1.9-fold greater (P < 0.01) longissimus muscle ether extract than steers in other groups. At final slaughter, LFC steers had a greater fat depth than ALF steers (P < 0.10) and had the greatest (P < 0.10) longissimus muscle ether extract. Increased fat depth for ALC steers at initial slaughter was a result of a greater (P < 0.05) mean adipocyte diameter in the s.c. depot. Mean i.m. adipocyte diameter followed the same trend (P < 0.16). The number of adipocytes per gram of s.c. fat was ]east for ALC and greatest for ALF (P < 0.10) at initial slaughter. Mean diameter and number of adipocytes per gram of i.m, and s.c. fat did not differ among treatments at final slaughter (after 180 d on a common finishing diet). High energy (ALC) increased activities of ATP-citrate lyase, fatty acid synthase, 6-phosphogluconate dehydrogenase, glucose-6-phosphate dehydrogenase, and malate dehydrogenase (P < 0.05), in the s.c. depot, and increased activities of ATP-citrate lyase and glucose-6-phosphate dehydrogenase (P < 0.10) in the i.m. depot at initial slaughter. Lipogenic enzyme activity in the s.c. depot at final slaughter did not differ among treatments. Glucose-6-phosphate dehydrogenase activity in the i.m. depot at final slaughter was lowest (P < 0.10) in ALF. Hypertrophy made a greater contribution to fat tissue growth than hyperplasia. Hypertrophy was affected by amount of energy, whereas hyperplasia was affected by source of energy. Differences diminished when cattle were fed the common finishing diet. Key Words: Adipocyte Diameter, Limit-Feeding, Lipogenic Enzymes

A multistate cooperative study was conducted to study the current issue of tail length in docked lambs and its relationship to incidence of rectal prolapse. A total of 1,227 lambs at six locations were randomly allocated to two or three tail dock treatments: 1) short--tail was removed as close to the body as possible, 2) medium--tail was removed at a location midway between the attachment of the tail to the body and the attachment of the caudal folds to the tail, and 3) long--tail was removed at the attachment of the caudal folds to the tail. Short-docked lambs had a greater (P < 0.05) incidence of rectal prolapse (7.8%) than lambs with a medium (4.0%) or a long (1.8%) dock. Female lambs had a higher (P < 0.05) incidence of rectal prolapse than male lambs. At two stations, lambs were finished either in a feedlot on a high-concentrate diet or on pasture with no grain supplementation. At one station, with a very low incidence of rectal prolapse, there was no difference in incidence between lambs finished in the feedlot or on pasture; however, at the station with a relatively high incidence of rectal prolapse, lambs in the feedlot had a higher (P < 0.05) incidence than lambs on pasture. The half-sib estimate of heritability for the incidence of rectal prolapse was low (0.14). The results of this study strongly implicate short dock length as a cause of rectal prolapse in lambs finished on high-concentrate diets. Furthermore, the results of this study and the only other study known conducted on this issue strongly suggest that docking lambs at the site of the attachment of the caudal folds to the tail will result in a negligible incidence of rectal prolapse. Key Words: Docking, Heritability, Lambs, Rectal Prolapse, Sheep, Tail

In Exp. 1, 31, 24, and 17 mature, pregnant Simmental x Angus cows (initial BW = 662.0 [+ or -] 10.4 kg) in each of 3 yr were used to determine the efficacy of stockpiled orchardgrass, limit-fed corn, or ad libitum hay for maintaining cows in mid- to late gestation, respectively. In Exp. 2, 24 mature, pregnant crossbred cows (initial BW = 677.7 [+ or -] 9.4 kg) per treatment in each of 3 yr were used to determine the efficacy of stockpiled orchardgrass, limit-fed corn, or ad libitum hay for maintaining cows in late gestation and early lactation, respectively. Each year, cows were assigned to treatment by BW. From November to February or from January to April, respectively, nutritional needs for mid- to late gestation (Exp. 1) or late gestation and early lactation (Exp. 2) were met either by 1) rotating cows on approximately 15.2 or 21.7 ha of predominantly orchardgrass pasture, set aside and fertilized in late August, 2) limit-feeding approximately 5.8 kg of whole shelled corn, 1.1 kg of a pelleted supplement, and 1.2 kg of hay daily, or 3) ad libitum feeding of round-baled hay. During extreme weather conditions, cows grazing stockpiled orchardgrass were limit-fed a grain-based diet. Postcalving weight (P < 0.10) was greatest for limit-fed cows in Exp. 1 and lowest for cows grazed on stockpiled orchardgrass; cows given ad libitum access to hay were intermediate in weight and did not differ from cows limit-fed or cows grazed on stockpiled orchardgrass (641.8, 657.4, and 634.0 kg, respectively). Calving date, calf birth and weaning weight, and conception rate did not differ among treatments (P > 0.15) in Exp. 1. In Exp. 2, weight at weaning did not differ among treatments (P > 0.17); however, postcalving weight (P < 0.01) was greatest for cows given ad libitum access to hay, intermediate for limit-fed cows, and lowest for cows grazed on stockpiled orchardgrass (674.8, 652.4, and 624.5 kg). Body condition score at any time point did not differ among treatments (P > 0.38), nor did calving date, calf birth and weaning weights, and conception rate (P > 0.12). Because of the few differences in cow performance, selection of energy sources for beef cows can be made based on economics. The cost to feed a cow hay in early to mid-gestation was nearly double that of limit-feeding the corn-based diet or grazing stockpiled orchardgrass. Because of lower quality pastures, the cost to graze cows on stockpiled orchardgrass during late gestation and early lactation was not as cost effective as limit feeding a corn-based diet. Key Words: Beef Cows, Corn, Forage, Restricted Feeding, Stockpiling

Seventy-three crossbred steers (initial BW = 170.5 [+ or -] 5.5 kg) from The Ohio State University (Exp. 1) and 216 crossbred steers (initial BW 135.4 [+ or -] 4.4 kg) from the University of Illinois (Exp. 2) were used to determine the effect of source of energy and rate of growth on performance, carcass characteristics, and glucose and insulin profiles on early-weaned steers. Effects of the diets used in Exp. 1 and 2 on ruminal pH and VFA concentrations were quantified using ruminally fistulated steers (Exp. 3). Cattle were weaned at an average age of 119 d in all experiments and were allotted by age, BW, and breed to one of four diets: high-concentrate, fed ad libitum (ALCONC), high-concentrate fed to achieve a gain of either 1.2 kg/d (1.2CONC) or 0.8 kg/d (0.8CONC), or high-fiber, fed ad libitum (ALFIBER). At 218 d of age, all steers were placed on the ALCONC diet until slaughter. Steers were implanted with Compudose at the initiation of all experiments and with Revalor-S when they were estimated to be 100 d from slaughter. When steers in Exp. 1 averaged 181 and 279 d of age, serum samples were collected to determine glucose and insulin concentrations. Steers were slaughtered when a fat thickness of 1.27 cm was reached (Exp. 1) or after 273 d on feed (Exp. 2). In Exp. 1, days in the feedlot (P < 0.01) and age at slaughter (P < 0.01) were lowest for ALCONC and ALFIBER steers, and greatest for 0.8CONC steers. Overall, ADG was greatest for ALCONC and lowest for 0.8CONC steers; feed efficiency was lowest (P < 0.01) for ALFIBER steers. Final BW did not differ (P > 0.57) among treatments. At 181 and 218 d of age, serum insulin was increased (P < 0.10) and intramuscular fat percentage was greatest (P < 0.07), respectively, for ALCONC steers. In Exp. 2, overall ADG (P < 0.06) and final BW (P < 0.04) were greatest for ALCONC and lowest for 1.2CONC and 0.8CONC steers. Overall feed efficiency was greatest for 0.8CONC and lowest for ALFIBER (P < 0.01). Growing phase diet did not affect marbling score at 218 d of age or at slaughter (P > 0.81). In Exp. 3, differences in ruminal pH after feeding may have been a consequence of increasing acetate (ALFIBER), propionate (ALCONC), or a combination of VFA (0.8CONC and 1.2CONC), respectively (diet x time after feeding, P < 0.10). Controlling growth by limit-feeding a high-concentrate diet for only 100 d does not extend the growth curve of early-weaned steers or enhance intramuscular fat deposition at slaughter compared to ad libitum intake of a high-concentrate or high-fiber diet. Key Words: Beef Cattle, Carcass Composition, Early Weaning, Feedlots, Insulin

Seventy Angus x Simmental calves (BW = 166.3 [+ or -] 4.2 kg) were used in a 3 x 2 factorial arrangement to determine the effect of age at feedlot entry and castration on growth, performance, and carcass characteristics. At 82 d of age, steers were castrated. Calves were placed in the feedlot at 111 (early-weaned), 202, or 371 (yearling) d of age. Steers were implanted with Synovex-S followed 93 d later with Revalor-S. Calves were harvested on an individual basis when fat thickness was estimated to be 1.27 cm. During the feedlot phase, yearlings gained faster (P < 0.01) than calves placed in the feedlot at 202 or 111 d of age (1.88, 1.68, and 1.62 kg/d, respectively); however, from 111 d of age until harvest, ADG was greatest for early-weaned calves, intermediate for cattle placed in the feedlot at 202 d of age, and lowest for yearlings (1.62, 1.47, and 1.21 kg/d, respectively; P < 0.01). Early-weaned calves spent the most days in the feedlot, followed by calves placed in the feedlot at 202 d of age; yearlings spent the fewest days in the feedlot (221, 190, and 163 d, respectively; P < 0.01). Total DMI when in the feedlot was similar (P = 0.22) among age groups; however, daily DMI was lowest for early-weaned calves, intermediate for calves placed in the feedlot at 202 d of age, and the highest for yearlings (7.1, 8.1, 10.5 kg/ d, respectively; P < 0.01). Early-weaned calves were the most efficient, followed by calves placed in the feedlot at 202 d of age; yearlings were the least efficient (227, 207, 180 g gain/kg feed, respectively; P < 0.01). Weight at harvest (682, 582, 517 kg, respectively; P < 0.01) and hot carcass weight (413, 358, 314 kg, respectively; P < 0.01) were greatest for yearlings, intermediate for cattle placed in the feedlot at 202 d of age, and lowest for early-weaned calves. Early-weaned calves had the smallest longissimus area, followed by calves placed in the feedlot at 202 d of age; yearlings had the largest longissimus area (77, 86, 88 [cm. sup.2], respectively; P < 0.01). Calves placed in the feedlot at 111 and 202 d of age had lower yield grades (3.2, 3.1, 3.5, respectively; P < 0.04), and produced fewer select carcasses than yearlings (25, 13, 48%, respectively; P < 0.01). Bulls and implanted steers both had an ADG of 1.7 kg/d when in the feedlot; however, bulls had a greater (P < 0.09) hot carcass weight (370 vs 354 kg) and a larger (P < 0.01) longissimus area (85.8 vs 81.3 cm2) than steers. Earlier feedlot placement resulted in greater quality grades but lower carcass weights. Key Words: Age Groups, Beef Cattle, Carcass Quality, Feedlots

Sixty-three Angus x Simmental calves were allotted to a bull or a steer group based on sire, birth date, and birth weight to determine effects of castration status on performance, carcass characteristics, and circulating insulin-like growth factor I (IGF-I) concentrations in early-weaned cattle. At 75 d of age, calves in the steer group were castrated. Calves were not creep-fed prior to weaning. All calves were weaned and weighed at an average age of 115 d and transported by truck to the OARDC feedlot in Wooster, OH. Performance and carcass characteristics were measured in three phases. Phase 1 was from 115 to 200 d of age, phase 2 was from 201 to 277 d of age, and phase 3 was from 278 d of age to slaughter. Before implantation, four bulls and four steers were selected for serial slaughter and carcass evaluation. Steers were implanted with Synovex-C at 130 d of age and with Revalor-S at 200 and 277 d of age. Serum samples were collected from all calves on the day of implantation, 28 and 42 d after implantation, and at slaughter and analyzed for circulating IGF-I concentration. Bulls gained 9.7% faster (1.75 vs 1.60 kg/d; P < 0.01), consumed 25 kg more DM (521 vs 496 kg; P = 0.11), and were 3.3% more efficient (282 vs 273 g/kg, P < 0.10) than steers in phase 1. However, steers gained 10.5% faster (1.62 vs 1.46 kg/d; P < 0.02), consumed similar amounts of DM, and were 6.5% more efficient than bulls (214 vs 201 g/kg; P < 0.06) in phase 2. Overall gains and efficiency were similar between bulls and steers; however, bulls consumed 140 kg more DM (P < 0.05), were 27 kg heavier (P < 0.05), and had to stay in the feedlot 18 more days (P < 0.05) than steers to achieve a similar amount of fat thickness. Implanted steers had greater concentrations of circulating IGF-I than bulls (P < 0.01), and the pattern of IGF-I concentration over time was affected by castration status (castration status x time interaction; P < 0.01). Synovex-C had a lower impact on circulating IGF-I concentration (implant effect, P < 0.01) than either Revalor-S implant. Eighty-five percent of both bulls and steers had marbling scores sufficient to grade low Choice or better. Bulls achieved their target fat thickness later, increased muscle growth, and deposited fat more favorably than steers, possibly due to a gradual increase in IGF-I concentration as the testicles grew rather than the large fluctuations in IGF-I concentration observed in steers following implantation. Key Words: Beef Cattle, Castration, Early Weaning, Insulin-like Growth Factor

In Exp. 1, 36 individually penned steers (initial BW = 294 [+ or -] 3.8 kg) were used to determine effects of dietary CP percentage and programming gain on performance and carcass characteristics. Steers were fed to achieve a predicted gain of 1.13 kg/d for the first 84 kg of gain and 1.36 kg/d for the next 124 kg of gain and were offered feed for ad libitum consumption for the final 58 kg of gain before slaughter. In these three phases of growth, steers were fed diets, sequentially, with the following CP percentages: HHH (16, 13.5, and 12.5%), LHH (9, 13.5, and 13%), or LLL (9, 9, and 9%). When predicted gain was 1.13 kg/d, ADG was greater (P < 0.01) for steers in the HHH (1.09 kg/ d) vs LHH and LLL (0.83 kg/d) systems. When predicted gain was 1.36 kg/d, ADG and gain efficiency were greatest (P < 0.01) for steers in the LHH system. Overall ADG and gain efficiency were greater (P < 0.01) for steers in the HHH (1.46 kg/d, 0.194) and LHH systems (1.38 kg/d, 0.190), compared with steers in the LLL (1.21 kg/d and 0.166) system. Carcass fat thickness was lower for steers in the LHH (0.74 cm) system than for steers in the LLL system (1.09 cra). In Exp. 2, 18 individually penned steers (initial BW = 225 [+ or -] 5.8 kg) were either offered a 13% CP diet for ad libitum intake (AL) throughout the 134-d experiment or fed a high- (16% CP; PI-HH) or low- (10% CP; PI-LH) CP diet and fed to achieve a predicted gain of 1.13 kg/d for the first 85 d of the experiment. Steers in the PI-HH and PI-LH feeding regimens were then offered a 13% CP diet for ad libitum consumption from d 86 to 134. Fractional protein accretion rate was greater (P < 0.01) for steers in the PI-HH and PI-LH feeding regimens than for steers in the AL regimen at d 92, 106, and 120. Fractional breakdown and synthesis rates were not affected (P = 0.63) by feeding regimen. Increased ADG and gain efficiency of steers during compensatory growth periods may in part be due to greater fractional accretion rates of skeletal muscle protein. Key Words: Performance, Protein Turnover, Steers

Four trials were conducted to determine the efficacy of using trainer animals to improve the health and performance of newly arrived feedlot calves. For all trials, trainer animals were given 3 wk to adapt to the feedlot before arrival of the feeder calves and initiation of the trials. Trainer animals were present with newly received feedlot calves for 14 d after arrival and then were removed from the pens for the remaining 14 d of the experiments. In Trial 1, trainer animals were six crossbred beef steers and six mature cull beef cows. Newly received calves were allotted to 18 pens with 10 calves/pen. Six pens contained a trainer steer and six pens contained a trainer cow. Similar procedures were used for the subsequent three trials, except 12 trainer cows and 24 pens were used, and in Trial 4 half of the calves were allotted to pasture paddocks for 14 d before placement in their feedlot pens. During wk 1 of Trial 1, calves with trainer cows and steers gained weight more rapidly (P < .10) than those without a trainer animal (1.12 vs .67 kg/d, respectively). During wk 2, this trend was reversed and overall gains did not differ (P > .20) among treatment groups. Morbidity was 16.7 for control calves, 28.3% for calves with trainer steers, and 8.3% for calves with trainer cows. Four of six trainer steers required antibiotic treatment for respiratory disease. On d 1, a greater (P < .05) percentage of calves in the trainer cow group (81.7%) were observed eating during the first 30 min after feeding compared with either the steer trainer group (60%) or the control group containing no trainer animal (48.3%). This trend continued on d 2 but was not evident on d 3 or 7. In Trial 2, overall gains were 10% greater (P < .06) and final BW was higher (P < .01) for calves with trainer cows than for those without trainers. Trainer cows resulted in a substantial reduction (P < .01) in calf morbidity compared with calves housed alone. In Trial 3, trainer cows did not improve performance or health of newly received calves. More (P < .07) calves with trainers than without were eating 5 min after feeding on d 1, 2, 4, and 8. In Trial 4, the presence of trainer cows the first 2 wk did not affect (P > .27) gains. However, calves placed on pasture after arrival had lower (P < .03) gains during wk 1 than those housed in the feedlot. Calves placed in pasture paddocks upon arrival had more than twice (P < .01) the incidence of morbidity of those placed directly in the feedlot. In these trials, trainer cows had a significant effect on eating behavior of newly received calves, but health and performance benefits were variable. Key Words: Feedlots, Calves, Behavior, Performance

Newly arrived feedlot calves undergo numerous stressors that result in 1) transient endocrine responses, 2) altered products of energy and protein metabolism, 3) changes in appetite and growth rate, 4) possible limited compromise of digestive and rumen function, and 5) a challenged immune system. The most consistent endocrine and metabolic responses to marketing, transport, and feedlot adaptation are seen with cortisol and epinephrine. In contrast to earlier work done with indirect in vitro gas production measurements, recent research has shown that the ruminal microbial population is able to effectively digest available substrate immediately following a calf's weaning, trucking, and 24 h of feed and water deprivation. Additionally, a period of feed and water deprivation up to 72 h coupled with 8 h of trucking does not reduce the concentration or total numbers of either the viable cellulolytic or total bacteria present in the rumen of newly weaned or feedlot-adapted calves. However, ruminal volume, DM, total weight of ruminal contents, and total protozoal numbers decrease as duration of feed deprivation increases. To compensate for the reduced DMI that occurs in the first 2 wk after arrival at the feedlot, increased nutrient density is needed to meet an animal's requirements for nutrients. Limited data suggest that newly arrived calves prefer a diet that is similar in moisture and texture to feeds with which they are familiar. Additionally, modification of the stress-associated behavior using trainer animals may improve the feed intake of newly received calves and may reduce calf morbidity. Key Words: Calves, Stress, Feedlots, Rumen, Digestion

Five ruminally fistulated 3-yr-old mature Holstein steers (average BW 691 [+ or -] 23 kg) were used in a 5 x 5 Latin square experiment with a 2 x 2 + 1 factorial arrangement of treatments. Effects of protein concentration and protein source on nutrient digestibility, excretion of DM and fecal N, ruminal fluid volume and dilution rate, ruminal characteristics, and in situ DM disappearance of whole shelled corn, ground corn, and orchardgrass hay were measured in steers limit-fed high-concentrate diets at 1.5% of BW. A negative control basal diet (NC; 9% CP) was supplemented to achieve either 11 or 14% CP; supplemental CP was either from soybean meal (11 and 14% SBM) or a 50:50 ratio of CP from urea and soybean meal (11 and 14% U). Dry matter and OM digestibilities were 5% greater (P < .07) for steers fed the SBM diets than for those fed the U diets. Starch digestibility did not differ (P > .10) among steers fed any of the diets. Nitrogen source did not affect (P > .10) apparent N digestibility or fecal N excretion; however, steers fed the NC diet had the lowest (P < .10) apparent N digestibility compared with those fed all other diets. Ruminal fluid volume was lower (P < .06) when steers were fed the NC diet compared with all other diets; there were no differences (P > .74) among diets for ruminal fluid dilution rate. In general, ruminal ammonia N and VFA molar proportions were not affected by protein source or concentration. Although CP concentration affected (P < .06) in situ DM disappearance of ground corn, CP concentration did not (P > .48) affect total tract digestion of DM or OM. This indicates that CP concentration may have affected site of digestion, but not extent of digestion. When mature ruminants were limit-fed a corn-based diet to meet primarily a maintenance function, protein source and concentration had little effect on measures of nutrient digestion. Key Words: Restricted Feeding, Grain, Protein, Digestibility

Efficiency of limit-feeding a whole shelled corn-based diet as an alternative to a conventional forage-based diet for nonlactating dairy cattle was determined. Twelve nonlactating, multiparous Holstein cows (initial BW 642 [+ or -] 50 kg) were used in a randomized complete block design. Nutrient digestibility, excretion of DM, N, and P, performance of cows, and feed costs were measured. Both diets were formulated to provide equal daily intakes of N[E.sub.1], protein, vitamins, and minerals, according to National Research Council recommendations. Dry matter intake was restricted by 30% for cows fed the high-corn diet compared with the high-forage diet (6.8 vs 9.6 kg/d, respectively); therefore, concentrations of nutrients in the high-corn diet were increased to compensate for decreased DMI. Diets were fed once daily, and cows had unlimited access to fresh water. After a 28-d adaptation period, cows were placed in metabolism stalls for a 6-d total collection of feces and urine. The limit-fed, high-corn diet had a 15% greater DM digestibility than the high-forage diet. A 29% decrease in DMI for the high-corn diet vs the high-forage diet resulted in a 40% decrease in fecal DM excretion. Starch digestibility and digestibility of whole corn kernels were not affected (P [greater than or equal to] .62) by diet. Despite similar N intakes, total N excretion was 22% greater (P < .01) for cows fed the high-forage diet than for those limit-fed the high-grain diet. Cow weight and condition score change did not differ (P > .10) between diets. Feed costs were reduced by $.38/d with the high-corn diet vs the high-forage diet. Limit-feeding a corn-based diet is an economically and nutritionally viable alternative to forage-based diets for nonlactating Holstein cows. Key Words: Holstein-Friesian, Manures, Restricted Feeding, Grain

In Exp. 1, early-weaned Targhee and Polypay crossbred lambs (60 ewes and 66 rams; initial BW 24 [+ or -] 1.0 kg) were used in a 2 x 3 factorial experiment to determine the effects of corn processing (whole shelled corn [WSC] or ground and pelleted corn [GC]) in combination with supplemental fiber (none [control]; soybean hulls, SBH [highly digestible]; or peanut hulls, PH [highly indigestible]) on DMI, ADG, feed efficiency, and visceral organ weight. For the total trial, WSC resulted in a 4% increase (P .10) by diet. Whole corn resulted in improved DM, OM, NDF, and N digestibility compared with GC. Overall, both the SBH and PH diets resulted in greater DMI and ADG than the control diet, which lacked supplemental fiber. Key Words: Maize, Fiber, Digestibility, Growth

In Trial 1, 108 crossbred steer calves (initial BW 295 kg) were allotted to 12 pens and used in a 186-d feedlot trial to determine the effects of increasing or decreasing roughage level on feedlot performance and carcass characteristics. Four dietary treatments were investigated: 1) 85% concentrate diet fed for 186 d, 2) 100% concentrate diet fed for 186 d, 3) 85% concentrate diet fed for 84 d followed by a 100% concentrate diet for the remaining 102 d, and 4) 100% concentrate diet for 84 d followed by an 85% concentrate diet for the remaining 102 d. Corn silage was added as roughage. During the first 84 d, level of dietary concentrate did not affect (P > .10) ADG. Steers switched to the 85% concentrate diet for the last 102 d had higher (P < .05) DMI than those fed the 100% concentrate diet; they did not exhibit an increase in ADG. Finishing phase feed efficiency was highest (P < .05) for steers continually fed 100% concentrate, lowest (P < .05) for steers continually fed 85% concentrate, and intermediate for steers whose concentrate level was switched during the trial. Carcass characteristics were not affected (P > .10) by concentrate level regimen. In Trial 2, 108 crossbred steer calves (initial BW 319 kg) were allotted to 12 pens and used in a 158-d trial to determine whether feedlot performance could be enhanced by manipulating roughage level and grain processing. Factors investigated were staged increases in concentrate level (70 to 85 to 100%) vs staged decreases in concentrate level (100 to 85 to 70%) and whole vs rolled high-moisture corn. Corn silage was added as roughage. Diet concentrate levels were changed on d 56 and 112. During the first 56 d, steers fed 70% concentrate diets grew 11% faster (P < .05) and consumed 19% more feed (P < .05) than those fed 100% concentrate diets. Steers fed rolled corn gained 8% faster (P < .06) and were 7% more efficient (P < .06) than those fed whole corn. During the last period (d 113 to 158), ADG was not affected (P > .10) by concentrate level or corn processing. Although increasing roughage during the feeding period increased feed intake in these trials, steer performance was not enhanced. Processing high-moisture corn did not affect feedlot performance. Key Words: Steers, Roughage, Intake, Performance

Blood serum concentration of IGF-I was analyzed to determine its relationship with individual postweaning feed efficiency (gain/feed) of 36 crossbred steer calves fed at three levels of feed intake (n = 12 at each level). Diets consisted of a corn silage-based growing diet for 84 d followed by a 91% concentrate finishing diet for 56 d. Dietary intake levels were at 80, 90, or 100% of ad libitum. Diets were formulated to ensure equal daily intake of protein, vitamins, and minerals across intake treatment levels. Intake was measured daily; ADG, DMI, and feed efficiency were calculated at 28-d intervals, through d 140. Individual weights and serum samples were collected at the beginning of the study and at 28-d intervals thereafter. The IGF-I concentrations were determined with a RIA. Data were analyzed as a multivariate split-plot in time. Imposed dietary intake restrictions did not affect serum IGF-I concentration (P = .90) or individual feed efficiency (P = .36), even though the least squares means for IGF-I concentration tended to decrease and the feed efficiency means tended to increase under the restricted intake levels. Serum IGF-I concentration, ADG, and feed efficiency were affected (P < .001) by collection date. Residual correlations between IGF-I concentrations at adjacent 28-d sampling times averaged .72. Diet intake level x sampling time interactions existed for ADG (P = .02) and feed efficiency (P < .001). Positive residual correlations of .28 (P < .001) and .16 (P = .07) existed between IGF-I and ADG and between IGF-I and feed efficiency, respectively. Regression analysis indicated that a 1 ng/mL increase in serum IGF-I concentration was associated with a .00135 kg/d increase in ADG (P < .001) and a .0001 kg gain/kg feed increase in feed efficiency (P = .04). These results support the hypothesis that serum IGF-I plays a role in growth and in efficiency of feed utilization in beef cattle. Key Words: Beef Cattle, Insulin-Like Growth Factor, Feeding, Restricted Feeding

We conducted two experiments to determine the effects of various intake restriction strategies on performance and carcass characteristics of feedlot cattle. In Exp. 1, 104 steer calves (273 [+ or -] 12 kg BW) were allotted to 12 pens. During Period 1 (273 to 372 kg BW), steers were limit-fed according to net energy equations to achieve predicted gains of .91, 1.13, or 1.36 kg/d. Control steers were offered ad libitum access to feed during this period. During Period 2 (372 to 535 kg BW), all steers were offered ad libitum access to feed. In Period 1, steers limit-fed for predicted gains of .91, 1.13, and 1.36 kg/d gained 1.03, 1.22, and 1.40 kg/d, respectively. Control steers offered ad libitum access to feed gained 1.66 kg/d. Steers that were limit-fed in Period 1 were able to compensate in Period 2; for the total experiment, there were no differences (P > .10) among the four feeding strategies investigated for rate of gain, feed efficiency, total feed intake, and carcass characteristics. Experiment 2 used 107 steer calves (300 [+ or -] 11 kg BW). Four feeding strategies were compared: step-wise increases in intake to program for increasing rate of gain, stepwise decreases in intake to program for decreasing rate of gain, feeding to hold gain constant at 1.36 kg/d, or offering steers ad libitum access to feed throughout the experiment to allow for maximum gains. When averaged over the total experiment, growth rate and days on feed were not affected (P > .10) by feeding system. Steers fed to achieve a step-wise increase in growth rate throughout the experiment had the lowest (P < .09) daily intakes and the highest (P < .09) feed efficiencies. Steers fed for increasing gains required 109 kg/steer less (P < .09) total feed to reach market weight than those offered ad libitum access to feed throughout the experiment. Feeding strategy had little effect on carcass characteristics. We concluded that as intake is restricted to a greater extent, net energy equations are less accurate in predicting rate of gain. Programming intake during the feeding period can result in significant reductions in feed expenditures. Key Words: Restricted Feeding, Steers, Performance, Carcasses

In Trial 1, 161 Angus x Simmental crossbred steers (initial BW 305 [+ or -] 1.0 kg) were used in a completely randomized design experiment to determine the effects of intake restriction and programmed gain on cattle performance and carcass composition and characteristics. Five feeding systems were tested using step-wise increases in programmed intake level. Initially steers were fed to gain 1.13 kg/d. Intake was then increased to achieve a gain of 1.36 kg/d. At the end of the feeding period, steers had ad libitum access to feed. Duration of intake restriction and the period of unrestricted intake was varied. Feeding steers at restricted intakes and then increasing daily gain by increasing feed intake using four different schedules all reduced (P < .05) daily feed intake and total feed intake compared with providing ad libitum access to feed throughout the trial. Furthermore, daily feed efficiency was increased (P < .05) by two of the feeding systems compared with offering ad libitum access to feed throughout the trial. The feeding system used did not affect (P > .10) quality grade of the carcasses. In Trial 2, 77 individually penned Angus x Simmental crossbred steers (initial BW 273 [+ or -] 1.2 kg) were used to determine the effects of various feed intake restriction systems. For systems i through 4, multiple periods of restriction and realimentation were investigated; the duration and magnitude of restriction were varied. Feed intake was not restricted for steers in system 5. The feed restriction systems used in this experiment did not result in decreased total feed intake or changes in carcass composition as compared with offering ad libitum access to feed. Reducing total energy intake seems to be a prerequisite to altering feed efficiency of steers in limit-feeding systems. Key Words: Beef Cattle, Restricted Feeding, Performance, Dry Lot Feeding, Carcass Composition

Three experiments were conducted to determine the effects of supplemental fat and CP concentration in diets of newly received steers. In Exp. 1, 72 steers (initial BW 201 [+ or -] 17 kg) were used in a 2 x 2 x 2 factorial experiment to determine effects of fat (Megalac, a calcium soap of palm fatty acids [CS]) concentration (0 vs 2%), CP concentration (12 vs 14%), and CP source (spray-dried blood meal [BM] vs soybean meal [SBM]) in receiving diets. Steers fed BM ate 22.8% more during wk 1 and 15.0% more during wk 2 if there was no CS in their diets compared with steers fed BM plus 2% CS (P < .05). In Exp. 2, 160 steers (initial BW 247 [+ or -] 16 kg) were used in a randomized complete block design experiment to determine effects of adding CS (0, 2, or 4%) to 14% CP diets containing BM. No differences (P > .10) in ADG or feed efficiency (FE) occurred due to CS. In Exp. 3, 186 steers (initial BW 243 [+ or -] 20 kg) were used in a randomized complete block design experiment to determine effects of supplemental fat source in receiving diets on steer performance. Diets contained either 0% added fat (control), 4% CS, or 4% animal-vegetable blend (AV). Feeding AV improved (P < .05) ADG and FE during wk 2 and FE for the total trial. Addition of AV to high-protein (15 to 22% CP) receiving diets improved FE, and CS resulted in no improvements in performance. Key Words: Dry Lot Feeding, Calves, Fat Products, Protein Concentrates, Feed Intake

Three experiments were conducted to determine the efficacy of limit-feeding corn-based diets as an alternative to hay for beef cows in gestation and early lactation. Seventy or 71 mature, pregnant Simmental crossbred cows (average weight = 589 [+ or -] 10 kg) were used in each trial. Each of 29 or 30 cows was fed approximately 5 kg of whole shelled corn, 1.2 kg of a pelletted supplement, and 1 kg of hay daily from November to April to meet nutritional needs for gestation. The remaining 41 cows were fed first-cutting round-baled hay free choice. Cows with ad libitum hay intake consumed approximately twice as much feed as cows limit-fed the corn-based diet. Body weight change during the winter was not affected (P > .10) by feeding system in Trials 1 and 2. Limit-feeding the corn-based diet had no detrimental effects on subsequent cow performance or conception rate or on calf weaning weight following summer grazing on pasture. The cost to feed a cow hay was nearly double that of limit-feeding the corn-based diet. Two additional experiments were conducted to determine the effect of supplemental monensin (200 mg/d) on performance of gestating Simmental-Angus first-calf heifers fed corn-based diets. In Trial 4, monensin-supplemented heifers were fed 10% less corn than control heifers. In Trial 5, both groups were fed equal amounts of feed. No adverse effects of feeding the corn-based diets were observed. It was concluded from these trials that corn-based diets can meet the nutrient requirements of pregnant beef cattle without adverse effects on production and at a lower cost than feeding hay. Key Words: Restricted Feeding, Cows, Gestation Period, Performance

Three experiments were conducted with Simmental x Angus crossbred steers to determine the effects of energy source and level on performance of newly arrived feedlot calves. In trial 1, 68 steers (initial BW 215 [+ or -] 9.4 kg) were used in a 2 x 3 factorial experiment to determine the effects of receiving diet and previous creep feed on performance. Diets were composed primarily of either corn silage, corn silage + alfalfa pellets + dry corn, or dry corn + alfalfa pellets. For the 41-d trial, calves fed the corn silage-based diet had greater (P [less than] .05) ADG and feed efficiencies than calves fed the other two diets. In Trial 2, 60 steers (initial BW 212 [+ or -] 4.6 kg) were used in a 28-d completely randomized design experiment to determine the effects of 16% CP receiving diets containing 70, 75, 80, or 85% concentrate on performance. There were no differences (P [greater than] .10) in ADG or feed efficiency due to dietary concentrate level. In Trial 3, 77 steers (initial BW 226.3 [+ or -] 3.0 kg) were used in a 2 x 3 factorial experiment to determine the effects of dietary concentrate and protein levels on performance during a 28-d receiving period. The factors were concentrate level (70 vs 85% concentrate) and protein level (12.5%, 16%, or phase-fed at 23%, 17%, 14%, and 12.5% during wk 1, 2, 3, and 4, respectively). During wk 1, calves fed the 85% concentrate diet had greater (P [less than] .01) DMI, ADG, and feed efficiency compared with 70% concentrate. Calves fed the 16% CP and phase-fed protein diets had greater (P [less than] .01) DMI, ADG, and greater (P [less than] .02) feed efficiency than calves fed the 12.5% CP diets. Receiving diets containing at least 16% CP and [greater than]70% concentrates are beneficial to calves during the first week after feedlot arrival. Key Words: Feedlot, Calves, Cattle, Concentrates, Protein

Two experiments were conducted to determine the effects of length of feed and water deprivation on ruminal microbes and ruminal characteristics. In Exp. 1, treatments were as follows: 1) weaned, but not trucked (0 h), 2) weaned, trucked, and fasted for 48 h (48 h), and 3) weaned, trucked, and fasted for 72 h (72 h). On d 0 (arrival back at the feedlot after treatment), DMI, ruminal volume (P < .05), and weight of ruminal contents (P < .05) decreased as length of feed and water deprivation increased. However, on d 4, there were no longer any differences (P > .10) in DMI or weight of ruminal contents. On d 0, percentage of ruminal DM in the 48- and 72-h treatment groups was lower (P < .01) than in the 0-h treatment group, but there were no differences (P >. 10) by d 4. After the steers used in Exp. 1 had been in the feedlot for 28 d, they were reallotted, and the three treatments (except for weaning) were repeated; the 0-h group remained at the feedlot. On d 0, DMI of the 48-h group was lower (P < .05) than that of the 0-h group; DMI of the 72-h group was intermediate. On d 0, the 0-h treatment group had a greater ruminal DM percentage than the 48- and 72-h treatment groups (P < .05); however, due to large within-treatment variation the total weight of ruminal contents did not differ (P > .10) among treatments. There were no decreases (P > .10) in cellulolytic or total bacterial concentration or in the ruminal numbers of cellulolytic or total bacteria due to length of feed and water deprivation on d 0 in either Exp. 1 or 2. In both trials, 48 and 72 h of feed and water deprivation decreased (P < .05) protozoal numbers on d 0 and 4 compared with the 0-h treatment group. Key Words: Calves, Deprivation, Stress, Rumen, Bacteria

In Trial 1, 240 crossbred steers (initial BW 243 [+ or -] 8 kg) were used in a 2 X 4 factorial experiment to determine the effects of receiving diet CP concentration (12, 14, 16, or 18%) and source (spray-dried blood meal [SDBM] vs soybean meal [SBM]) on steer performance. There were linear (P < .01) increases in ADG and feed efficiency during wk 1. For the entire trial, there was an increase (P < .01) in feed efficiency with increasing CP concentration and diets containing SDBM compared with those containing SBM. In Trial 2, 240 crossbred steers (initial BW 246 [+ or -] 14 kg) were used in a completely randomized design experiment to determine the effects of receiving diet CP concentration (11, 14, 17, 20, 23, or 26%) on steer performance. Average daily gain and feed efficiency increased (P < .01) with increasing CP concentration during wk 1. There were quadratic (P < .01) responses to CP concentration for final weight, ADG, and feed efficiency. In Trial 3, 216 steers (initial BW 238 [+ or -] 1 kg) were used to determine the effects of receiving diet protein sources on steer performance. The control diet used SBM as the supplemental CP source and was formulated to contain 12.5% CP. The other five protein sources were corn gluten meal (CGM), ring-dried blood meal (RDBM), SDBM, fish meal (FM), and SBM. For these five CP sources, diets were formulated to contain 23% CP during wk 1, 17% CP during wk 2, and 12.5% CP during wk 3 and wk 4. During wk 1, control steers had the lowest ADG (P < .07) and feed efficiency (P < .01) whereas steers fed RDBM and SDBM had the highest (P < .01) feed efficiency. Increased CP concentrations are needed early in the receiving period, when DMI is low. Key Words: Feedlots, Calves, Protein, Performance

Eight ruminally fistulated steers, 7 to 8 mo old, were used in a completely randomized, 2 x 2 factorial experiment to determine the effects of energy density and protein source in receiving diets on in situ DM, NDF, and N disappearance, concentrations of ruminal bacteria, protozoa, ammonia, and pH. Two energy densities (1.80 and 1.48 Mcal/kg of [NE.sub.m]) and two protein sources (spray-dried blood meal [SDBM] and soybean meal [SBM]) were compared. Fistulated steers were weaned, transported by truck, and held in a sale barn before their arrival at the feedlot. On d 0 (day of arrival at the feedlot), DMI was 62% of DMI on d 7 after arrival. Overall, feeding a high-energy diet resulted in lower (P [is less than] .01) in situ DM disappearance (DMD) of orchardgrass than feeding a low-energy diet at both 24 and 48 h. In situ 24-h DMD averaged 46.6% on d -3 and 41.6% on d 0, whereas 48-h in situ DMD on d -3 and 0 averaged 58.2 and 58.6%, respectively, indicating the ruminal microbial population was not inhibited in its ability to digest available substrate. Additionally, there were no differences (P [is greater than] .10) in 48-h in situ NDF disappearance between d -3 and 0 (58.8 vs 57.8%), respectively. No differences (P [is greater than] .10) occurred in the concentration of total bacteria, or cellulolytic bacteria, due to feed and water deprivation. Concentration of total protozoa was lower (P [is less than] .05) on d 0 than at any other time. Entodinium averaged 72.5% of genera before weaning, and more than 90% of genera found on all treatments by d 21. Diplodinium and Epidinium percentages tended to decline after weaning. Isotricha concentrations were low and Dasytricha were eliminated after d 7. In conclusion, the concentration of ruminal bacteria and the ability to digest available substrate were not decreased immediately after weaning, trucking, and 24 h of feed and water deprivation.

The effects of intake (ad libitum and 70% of ad libitum) and corn processing (whole or rolled) on digestion, ruminal metabolism, and blood metabolites were determined in a 2 x 2 factorial experiment using eight ruminally fistulated steers. All-concentrate diets were fed with adjustments to dietary concentrations of N, vitamins, and minerals to ensure equal daily intake of these nutrients. Digestion of DM, OM, and starch were affected by an intake x processing interaction (P [is less than] .03). Starch digestion for the low-intake, whole-corn diet was much lower than that for the other three diets. This decrease in starch digestion was the major reason for the interaction. Nitrogen digestion was improved (P [is less than] .03) with limited intake but was not affected by processing. Ruminal volume and ruminal turnover (percentage/hour) were both reduced (P [is less than] .03) on the low-intake diet. Molar proportion of acetate was reduced and propionate was increased (P [is less than] .01) for steers receiving high intake of rolled corn compared with the other three diets. Butyrate concentrations were increased (P [is less than] .01) when corn was rolled before feeding. Ruminal pH was higher immediately before feeding for steers receiving whole corn than for those receiving rolled corn. Decreases in pH were observed for rolled corn 2 to 9 h after feeding, suggesting a faster rate of fermentation of rolled corn than of whole corn. Concentrations of blood glucose and insulin were not affected by intake or processing. It was concluded that processing corn can improve DM and OM digestibility if intake is restricted and that N digestion is improved with restricted feeding. Reductions in intake of up to 30% do not have an effect on ruminal pH, nor do they reduce blood glucose or insulin concentrations.

In Trial 1, 12 wether lambs (34.2 [+ or -] .8 kg BW) were used to determine the effects of restricting intake of diets increasing in percentage of concentrate, to achieve isoenergetic intakes, on digestibility and N metabolism. The trial consisted of two 14-d periods, 9 d for adaptation and 5 d for total collection of urine and feces. Treatments were 22, 39, 61, and 92% concentrate diets fed at ad libitum intake and 90, 80, and 70% of ad libitum intake, respectively. Diets were formulated to provide equal daily intakes of ME. Feeding diets increasing in proportion of concentrate at restricted intakes resulted in linear increases (P [is less than] .001) in DM, OM, ADF, and NDF digestibilities. Starch digestibility was not affected (P [is greater than] .10) by intake. Apparent N digestion was improved (P [is less than] .001) with restricted feeding of diets containing greater proportions of concentrate. Nitrogen retention was increased (P [is less than] .005) for lambs receiving diets containing a greater proportion of concentrate at reduced intakes. In Trial 2, 12 wether lambs (30.6 [+ or -] .6 kg BW) were used to determine the effects of feeding high-concentrate (92%) diets at reduced intakes on digestibility and N metabolism. Diets were fed at ad libitum intake and 90, 80, and 70% of ad libitum intake. The trial consisted of two 14-d periods, similar to Trial 1. Restricting the intake of high-concentrate diets improved (P [is less than] .001) digestibility of DM, OM, ADF, starch, and CP. Digestibility of DM, ADF, CP, and starch increased .142, .423, .497, and .046 percentage units, respectively, for each 1% reduction in DM intake. Nitrogen retention was quadratic with maximal retention (percentage of N digested) occurring at an intake of 89% of ad libitum. It was concluded that diet digestibility and N utilization were enhanced when a restricted feeding program was used that provided equal daily intakes of protein, vitamins, and minerals.

Sixty Angus crossbred steers (initial BW, 237 kg) were used in a 2 x 2 factorial experiment to determine the effects of energy density and protein source in receiving diets on steers performance and total tract nutrient digestion. The factors compared were energy density (1.80 vs 1.48 Mcal/kg of [NE.sub.m], referred to as high-energy and low-energy, respectively) and protein source (ring-dried blood meal [BM] vs soybean meal [SBM]). Diets containing BM resulted in a 10.6% greater (P [is less than] .09) ADG and a 7.6% improvement (P [is less than] .05) in efficiency of feed utilization compared with those containing SBM. High-energy diets resulted in an 8.7% improvement (P [is less than] .05) in feed efficiency vs low-energy diets. Dry matter digestibility (DMD), NDF digestibility (NDFD), and CP digestibility (CPD) were exceptionally high during wk 1, when DMI was approximately 1.5 kg/d. Nutrient digestibility declined during wk 2 and 3, as intake increased, before stabilizing between wk 4 and 6. Additionally, NDFD was not consistently lower (P [is greater than] .10) during this study for high-energy diets than for low-energy diets. The results of the overall performance data indicate that, compared to SBM, feeding BM may improve ADG and feed efficiency during the receiving period when dietary CP is approximately 13%. Additionally, DMD, NDFD, and CPD were higher on d 7 than at any other time, indicating that by d 7 ruminal function was not adversely affected. Therefore, it seems that the reduced feed intake and growth rate normally seen during the first 2 wk in the feedlot is not caused by a reduction in diet digestibility.

A 4 x 4 Latin square metabolism trial with a 2 x 2 factorial arrangement of treatments was conducted to determine N kinetics in steers. Steers were fed either untreated (UNT-WS) or alkaline hydrogen peroxide-treated wheat straw (AHP-WS) based diets supplemented with soybean meal (SBM) or blood meal (BM). Single doses of (15NH4)2SO4 were infused into ruminal pools to determine N kinetics. Ruminal NH3N concentrations (main effects) were 3.81, 1.65, 3.18, and 2.28 mg/dL in steers when fed diets that contained UNT-WS, AHP-WS, SBM, and BM, respectively. Ruminal N pool size was greater (P < .05) for UNT-WS than for AHP-WS diets and also was greater (P < .10) for SBM than for BM diets. Nitrogen flux rate into the rumen was not affected (P > .10) by diet. However, production rate of N from the ruminal pool was greater (P < .05) for UNT-WS than for AHP-WS diets and greater (P < .10) for SBM than for BM diets. Nitrogen recycled into the rumen was 33% greater (P < .05) for AHP-WS than for UNT-WS diets and 26% greater (P < .05) for BM than for SBM diets. Nitrogen recycling (percentage of N intake) was 33, 56, 36, and 49% for UNT-WS, AHP-WS, SBM, and BM diets, respectively. The blood urea N (BUN) concentrations were 10.23, 4.58, 7.15, and 7.65 mg/dL for UNT-WS, AHP-WS, SBM, and BM diets, respectively. The BUN derived from the ruminal NH3N pool was 66% less (P < .05) for AHP-WS diets than for UNT-WS diets but was not affected by protein source. It was concluded that increased ruminal OM digestion and supplementation with slowly degradable protein source increases N recycling to the rumen.

The objective of this study was to determine the effects of soybean meal (SBM) or spray-dried blood meal (BM) supplementation of diets based on untreated (UNT-WS) or alkaline hydrogen peroxide-treated wheat straw (AHP-WS). A 4 x 4 Latin square design with a 2 x 2 factorial arrangement of treatments was used. Variables included nutrient digestion and flow to the duodenum. Four Simmental steers (average weight 477 kg) fitted with ruminal and duodenal cannulas were fed 65% UNT-WS or AHP-WS based diets in 12 equal portions daily. Diets were formulated to contain 10% CP. Chromic oxide was used as the digesta flow marker and purines were used as the microbial marker. There were no straw type x protein source interactions. Total tract and ruminal OM digestibility were approximately 25% greater (P < .04) when AHP-WS was fed than when UNT-WS was fed. Source of protein did not affect (P > .10) OM or fiber digestion in the rumen or total tract. Ruminal digestion of NDF and ADF was increased (P < .01) by 51 and 40%, respectively, when AHP-WS was fed than when UNT-WS was fed. Main effect means (P > .10) for N flow to the duodenum as a percentage of N intake were 128.2, 142.5, 133.4, and 137.6 for UNT-WS, AHP-WS, SBM, and BM treatments, respectively. Despite increased (P < .01) ruminal OM digestion for AHP-WS, microbial N flow to the duodenum was greater (P < .01) when UNT-WS was fed than when AHP-WS was fed. Non-NH3-non-microbial N flow to the duodenum was greater (P < .08) for BM than SBM. It was concluded that ruminal and total tract DM, OM, NDF, and ADF digestibilities were greater for AHP-WS than UNT-WS. Treatment of straw and source of protein did not affect total N flow to the duodenum, likely as a result of extensive N recycling to the rumen.

The effects of protein and energy supplementation of diets based on wheat straw were investigated in sheep. Suffolk wethers were surgically fitted with cannulas in the rumen or in the abomasum. The results showed that low-protein diets were compensated for by increasing nitrogen recycling back to the rumen. Nitrogen recycling also occurred in the abomasum but was insufficient, as indicated by increased nitrogen retention in lambs fed high-energy or high-protein diets. Overall, the results showed that nitrogen cycling did not suffice for the protein requirements of growing lambs.

The different factors influencing microenvironments in the rumen were studied by measuring cellulose disappearance (CD) and dry matter disappearance (DMD) of alfalfa hay enclosed in synthetic fiber bags during rumen fermentation in vitro and in vivo. The kind of fabric and its pore size affected the acidity, CD and DMD in the bags. A pore size of 50 micrometer induced the accumulation of gas and reduced CD and DMD due to reduced pH, which was in turn caused by the lack or absence of fluid exchange with the digesting medium.

Two experiments were conducted to determine the effects of diet on growth of steers weaned at approximately 100 vs 205 d of age. In Exp. 1, a 2 x 2 x 2 factorial experiment was conducted using 78 Angus crossbred cow-calf pairs. The factors examined were age at weaning (early, at 103 [+ or -] 3 d [EW] vs normal, at 203 [+ or -] 3 d [NW]), feeding strategy (ad libitum vs postweaning programmed intake), and dietary CP concentration (100 vs 120% of NRC [1984] recommended levels). Early-weaned calves had a greater (P [is less than] .001) ADG than NW calves from 103 to 203 d and reached market weight at 385 d vs 418 d for NW calves (P [is less than] .001). Likewise, steers offered feed for ad libitum consumption reached market weight at 394 d, compared with 409 d for programmed-intake steers (P [is less than] .05). In Exp. 2, 64 Angus crossbred steers were either weaned at 93 [+ or -] 3 d and fed one of four diets, weaned at 210 [+ or -] 3 d without access to creep feed, or weaned at 210 [+ or -] 3 d with access to creep feed for 60 d prior to weaning. Early-weaned calves were heavier (P [is less than] .01) than NW calves at 210 d if fed either 100 or 90% concentrate diets, and they had greater (P [is less than] .001) backfat thickness at 210 d but no difference (P [is greater than] .10) in longissimus muscle area compared to EW calves fed a 60% concentrate diet. At slaughter, 80 to 100% of steers on all treatments graded low Choice or higher. Feeding high-concentrate diets to EW beef calves accelerated growth rate and fat deposition early in the feeding period and may be a way to provide young cattle for a high-quality beef market. Key Words: Beef Cattle, Meat Quality, Weaning