Evaluation of wheat middlings as a supplement for beef cattle consuming dormant bluestem-range forage

Two experiments were conducted to evaluate wheat middlings as a supplement for cattle consuming dormant bluestem-range forage. Effects of supplement type and amount were evaluated in Exp. 1, which consisted of feeding supplements of soybean meal:grain sorghum (22:78) or two different amounts of wheat middlings. Sixteen ruminally fistulated steers were blocked by weight (BW = 374 +/- 8.3 kg) and assigned randomly to the following treatments: 1) control, no supplement (NS); 2) soybean meal:grain sorghum (SBM/GS) formulated to contain the same CP concentration (21%) and fed to provide a similar energy level (3.5 Mcal of ME/d); 3) a supplement of 100% wheat middlings fed at a low level (LWM); and 4) 100% wheat middlings fed at twice the amount of LWM (7 Mcal of ME/d; HWM). The influence of different supplemental CP concentrations in a wheat middlings-based supplement was evaluated in Exp. 2. Sixteen ruminally fistulated steers were blocked by weight (BW = 422 +/- 8.1 kg) and assigned randomly to the following treatments: 1) control, no supplement (NS); 2) 15% CP; 3) 20% CP; and 4) 25% CP supplements. These supplements consisted of 60% wheat middlings and various ratios of soybean meal and grain sorghum to achieve the desired CP concentration. In Exp. 1, SBM/GS and HWM supplements increased (P less than .10) and LWM tended to increase (P = .16) forage DMI compared with NS. All supplements in Exp. 1 increased (P less than .10) DM digestibility, ruminal DM fill, and ruminal indigestible ADF (IADF) passage rate compared with NS, although the greatest response in fill and passage was observed with HWM. In Exp. 2, forage DMI, DM digestibility, NDF digestibility, ruminal DM and IADF fill, IADF passage rate, and fluid dilution rate were increased (P less than .01) by supplementation. Forage DMI, ruminal IADF passage rate, and fluid dilution rate increased quadratically (P less than .10), and NDF digestibility, ruminal DM and IADF fill increased linearly (P less than .10) with increased supplemental CP concentration. These experiments indicate that wheat middlings performed similarly to a SBM/GS supplement of equal CP concentration, when both were fed to provide a similar amount of energy daily. Additionally, use of poor-quality range forage was enhanced when wheat middlings-based supplements were formulated to contain a CP concentration of 20% or greater.     

The influence of timing and the addition of urea to supplements containing DL-methionine on ruminal fermentation and cow weight change in beef cows.

A study was conducted to determine an optimal time for supplementation of DL-methionine in relation to time of forage intake by mature British breed-type crossbred cows, and two other experiments were conducted to determine whether ruminal ammonia concentration limited changes in disappearance rates in situ and ruminal functions caused by supplements containing DL-methionine. Experiments 1 and 2 used 4 x 4 Latin square designs with four cows in each experiment. Treatments in Exp. 1 were no supplement (CON), DL-methionine at feeding (0800), DL-methionine 4 h after feeding (1200), and DL-methionine 7 h after feeding (1500). Treatments in Exp. 2 were .5 kg of beet pulp (CON), .5 kg of beet pulp plus 16.5 g of DL-methionine (MET), .5 kg of beet pulp plus 16.5 g of DL-methionine and 55 g of urea (METU), and .4 kg of soybean (SOY). Experiment 3 was conducted in a 326-ha pasture with treatments of no supplement (CON), .5 kg of beet pulp plus 12.5 g of DL-methionine and 30 g of urea (METU), and .4 of kg soybean meal (SOY). In Exp. 1, in situ NDF disappearance rates of cows supplemented at 1200 and 1500 were greater (P less than .01) than those of cows supplemented at 0800. In Exp. 2, ruminal ammonia concentration was greatest (P less than .001) for METU (5.2 mg/dl) and least for CON (1.5 mg/dl). Disappearance rates in situ for DM differed (P less than .01) among treatments; METU was similar (P greater than .2) to SOY but faster (P less than .01) than MET. Disappearance rates of NDF were greatest (P less than .001) for METU-supplemented cows. In Exp. 3, DM and NDF disappearance rates were faster (P less than .10) for SOY than for METU. Cow BW change was positive for METU and SOY, and decrease in condition score was least (P less than .10) for METU- and SOY-treated cows. These studies indicate favorable ruminal responses to DL-methionine supplementation; however, the response depended on time of supplementation and ruminal ammonia concentration.     

Evaluation of dairy food processing wash water solids as a protein source: I. Forage intake, animal performance, ruminal fermentation, and site of digestion in heifers fed medium-quality hay.

Twelve ruminally, duodenally, and ileally cannulated (average initial BW 313 +/- 20 kg) and 27 intact Hereford heifers (average initial BW 256 +/- 17 kg) were used in two experiments to evaluate dairy food wash water solids (WWS) as a protein source in medium-quality hay diets. Heifers received a basal diet of orchardgrass hay (7.4% CP) and were assigned to one of three supplement treatments: control (C; .9% CP), WWS (18.8% CP)-, and soybean meal (SBM; 19.1% CP)-based supplements (fed at 1.5 kg of DM/d). Supplements were formulated to have similar ME concentrations. Ruminal ammonia concentrations were greater (P less than .10) for WWS- and SBM-supplemented heifers than for C heifers at most sampling times. Moreover, WWS and SBM increased (P less than .10) total VFA (mM) and acetate (mol/100 mol) and lowered propionate (mol/100 mol) at several sampling times. Ruminal fluid volume (liters) was unchanged (P greater than .10) by treatment; however, fluid dilution and flow rate (liters/h) were less (P less than .10) in C heifers than in heifers fed SBM or WWS supplements. Wash water solids and SBM supplementation increased (P less than .10) OM, NDF, and ADF digestibilities compared with C heifers. Feeding WWS and SBM supplements increased BW at 84 d (P less than .10) compared with C-supplemented heifers. Forage intake at 54 and 84 d by heifers supplemented with SBM or WWS was greater (P less than .10) than by C heifers. Control-supplemented heifers had the least, WWS intermediate, and SBM the greatest ADG at 84 d (P less than .10; .14 vs .35 vs .48 kg/d, respectively). These data indicate that WWS may be used as a protein source without serious adverse effects in heifers consuming medium-quality hay for 84 d.     

Effects of supplement type on animal performance, forage intake, digestion, and ruminal measurements of growing beef cattle

Two experiments were conducted to determine the effects of supplement type on the rate of gain by heifers grazing bermudagrass and on the intake, apparent total-tract OM digestibility, ruminal fermentation, digesta kinetics, in situ DM digestibility, and forage protein degradation by steers fed prairie hay. In Exp. 1, 45 heifers (284+/-24 kg) grazed a bermudagrass pasture for 91 d in the late summer to determine the effects of no supplement (CON), or one of four individually fed monensin-containing (150 mg/[heifer x d]) supplements (MINCS; 0.1 kg of mineral mix with 0.2 kg [DM] of cottonseed hulls as a carrier/[heifer x d]), a pelleted protein supplement (PROT; 1 kg of DM, 242 g of degradable intake protein [DIP]/[heifer x d]), or high-fiber (HF) and high-grain (HG) (2 kg of DM, 243 and 257 g of DIP, respectively/[heifer x d]) pelleted energy supplements. In Exp. 2, four ruminally cannulated steers (311+/-22 kg) with ad libitum access to low-quality (4% DIP, 73% NDF, 40% ADF) prairie hay were individually fed monensin-containing (200 mg/[steer x d]) treatments consisting of 1) mineral mix + corn (MINCR; 0.1 kg of mineral and 0.4 kg of cracked corn [DM] as a carrier, 19 g of DIP/[steer x d]), 2) PROT (1.4 kg of DM, 335 g of DIP/[steer x d]), 3) HF, or 4) HG (2.9 kg of DM, 340 and 360 g of DIP, respectively/[steer x d]) in a 4 x 4 Latin square with 14-d adaptation and 6-d sampling periods. In Exp. 1, the HF-, HG-, and PROT-supplemented heifers had greater (P < 0.01) rates of gain than CON heifers, and the HF- and HG-supplemented heifers tended (P < 0.11) to gain more weight than those fed PROT. In Exp. 2, steers fed PROT consumed more (P < 0.05) hay OM than HF and HG, or MINCR. Total OM intake was greater (P < 0.01) by supplemented steers than MINCR-fed cattle. Hay OM digestibility was not affected (P = 0.19) by treatment, but total diet OM digestibility was greater (P < 0.01) for HF- and HG- than for MINCR- or PROT-fed steers. The rate of in situ DM digestibility was greater (P < 0.01) for HF, HG, and PROT than for MINCR. Results from these studies indicate that feeding milo- vs fiber-based energy supplements formulated to provide adequate DIP did not result in different forage intake, OM digestibility, or in situ DM digestibility, whereas both increased ADG in heifers consuming low-quality forages compared with unsupplemented or mineral- or protein-supplemented cattle. An adequate DIP:TDN balance decreased the negative associative effects often observed when large quantities of high-starch supplements are fed with low-quality hay.     

Substitution of DL-methionine for soybean meal as a winter supplement for gestating cows grazing native range

A winter grazing study was conducted to determine whether DL-methionine could replace soybean meal as a N supplement for gestating beef cows. During two winters (Trial 1, n = 51; Trial 2, n = 60), crossbred beef cows grazed native foothill range. Three treatment groups were supplemented with either none (CON), DL-methionine (7.5 g Trial 1 and 9 g Trial 2) in .5 kg beet pulp carrier (BPM) or .4 kg soybean meal (SBM). Cows were supplemented individually every other day. Small differences were noted in cow BW, condition score and blood metabolites. Unsupplemented cows lost the greatest amount of BW (P less than .01) in both trials and lost more (P less than .05) condition during Trial 1 than cows fed BPM or SBM supplements. Blood samples were obtained on two consecutive days during each trial (45 d and 25 d prepartum) and analyzed for blood urea N, total bilirubin, creatinine, albumin, total protein and cholesterol. A treatment x day preparatum interaction (P less than .05) was noted for blood urea. Blood urea nitrogen declined as gestation length increased for CON and SBM cows, but blood urea of BPM-supplemented cows remained low and unchanged. In situ forage digestion was measured in 12 ruminally cannulated cows (four/treatment). In both trials, in situ rate of NDF disappearance was greater (P less than .05) for SBM than for BPM. In Trial 2, a treatment x sampling hour interaction was detected for purine concentration of whole ruminal contents; SBM maintained greater purine concentrations throughout the 48-h supplementation cycle than BPM did. Principal component analysis suggested that ruminal ammonia limited the microbial growth response to DL-methionine. Therefore, alternate-day supplementation of DL-methionine plus beet pulp did not effectively substitute for soybean meal in these trials.     

Effect of supplementation of dried distillers grains with solubles on forage intake and characteristics of digestion of beef heifers grazing small-grain pasture

Sixteen ruminally cannulated, English-crossbred heifers (378 ± 28.4 kg) grazing small-grain pasture (SGP) were used in a completely randomized design to evaluate effects of supplementing different amounts of corn dried distillers grains with solubles (DDGS; 0, 0.2, 0.4, and 0.6% of BW; as-fed basis) on forage intake, digestibility, and rumen fermentation characteristics. The experiment was conducted from April 6 through April 20, 2007. Heifers grazed in a single SGP with supplements offered individually, once daily at 0700 h. Forage and total OM, CP, and NDF intake were not affected (P ≥ 0.21) by DDGS amount. Digestibility of NDF and ether extract (EE) increased linearly (P < 0.001) when heifers consumed more DDGS. Intake of DM (kg/d and g/kg of BW), ruminal volume (L), fluid dilution rate (%/h), fluid flow rate (L/h) turnover time (h), and particle dilution rate (SGP and DDGS) were not affected (P ≥ 0.32) by increasing DDGS supplementation amount. In situ DDGS CP kinetic parameters were not affected (P ≥ 0.25) by increasing DDGS supplementation amount. Forage masticate in situ soluble CP fraction and CP effective degradability increased quadratically (P = 0.01) with increasing DDGS supplementation amount. However, amount of DDGS did not affect forage masticate CP slowly degradable fraction (%; P = 0.39) or degradation rate (%/h; P = 0.63). Rate of in situ disappearance (%/h) for DDGS DM (P = 0.94), forage masticate DM (P = 0.89), and NDF (P = 0.89) were not affected by DDGS supplementation amount, nor was rumen undegradable intake protein (% of CP) for DDGS (P = 0.28) and forage masticate samples (P = 0.93). Ruminal concentration of VFA and ammonia and ruminal pH were not affected (P ≥ 0.21) by increasing DDGS amount. Results indicated that DDGS can be used in SGP supplements without negatively affecting forage intake, digestibility, or ruminal fermentation.     

Influence of source and level of ruminal-escape lipid in supplements on forage intake, digestibility, digesta flow, and fermentation characteristics in beef cattle.

Six ruminally fistulated steers (550 kg) and 24 heifers (315 kg) were used to determine the effect of source and amount of ruminal-escape lipid in a supplement on forage intake and digestion. Steers were used in a 6 x 6 Latin square digestion study to evaluate six supplementation treatments: 1) negative control (NC), no supplement; 2) positive control (PC), soybean meal:grain sorghum supplement; 3) low-Megalac (calcium salts of fatty acids; LM) supplement; 4) high-Megalac (HM) supplement; 5) low-Alifet (crystallized natural animal fat, LA) supplement; and 6) high-Alifet (HA) supplement. Supplements were fed at .30% of BW on a DM basis and were isoenergetic within fat levels (high vs low). Steers were fed mature brome hay (7.2% CP) at 1.5% of BW on a DM basis. In the forage intake trial, heifers were assigned randomly to the same supplement treatments. Prairie hay (4.4% CP) was offered at 130% of ad libitum intake. Dry matter and NDF digestibility, ruminal DM fill, indigestible ADF passage rate, and fluid dilution and flow rates were not different (P greater than .10) among treatments. Total VFA concentrations were greater (P less than .01) and acetate-to-propionate ratio (Ac:Pr) was less (P less than .01) in supplemented groups; however, neither source nor level of escape lipid influenced either total VFA or Ac:Pr. Forage intake was greater (P less than .01) for supplemented groups than for the NC. At the high level of fat inclusion, heifers supplemented with Alifet ate slightly more (P less than .05) forage than those supplemented with Megalac.(ABSTRACT TRUNCATED AT 250 WORDS)     

Optimizing nitrogen utilization in growing steers fed forage diets supplemented with dried citrus pulp

Our objectives were to compare the effects of sources of supplemental N on ruminal fermentation of dried citrus pulp (DCP) and performance of growing steers fed DCP and bahiagrass (Paspalum notatum) hay. In Exp. 1, fermentation of DCP alone was compared with that of isonitrogenous mixtures of DCP and solvent soybean meal (SBM), expeller soybean meal (SoyPLUS; SP), or urea (UR). Ground (1 mm) substrates were incubated in buffered rumen fluid for 24 h, and IVDMD and fermentation gas production kinetics and products were measured. Nitrogen supplementation increased (P < 0.10) ruminally fermentable fractions, IVDMD, pH, and concentrations of NH3 and total VFA, but reduced the rate of gas production (P < 0.10) and the lag phase (P < 0.01). Supplementation with UR vs. the soy-based supplements increased ruminally fermentable fractions (P < 0.05) and concentrations of total VFA (P < 0.10) and NH3 (P < 0.01), but these measures were similar (P > 0.10) between SBM and SP. In Exp. 2, 4 steers (254 kg) were fed bahiagrass hay plus DCP, or hay plus DCP supplemented with CP predominantly from UR, SBM, or SP in a 4 x 4 Latin square design, with four 21-d periods, each with 7 d for DMI and fecal output measurement. Nitrogen-supplemented diets were formulated to be isonitrogenous (11.9% CP), and all diets were formulated to be isocaloric (66% TDN). Intake and digestibility of DM, N, and ADF were improved (P < 0.05) by N supplementation. Compared with UR, the soy-based supplements led to greater (P < 0.05) DM and N intakes and apparent N and ADF digestibilities. Plasma glucose and urea concentrations increased (P < 0.10) with N supplementation and were greater (P < 0.01) for the soy-based supplements than for UR. Intake, digestibility, and plasma metabolite concentrations were similar (P > 0.1) for SBM and SP. In Exp. 3, 24 steers (261 kg) were individually fed bahiagrass hay plus DCP (control), or hay plus DCP supplemented with CP predominantly from UR or SBM. Over 56 d, DMI and ADG were greatest (P < 0.05) in steers fed SBM. Nitrogen supplementation increased (P < 0.05) DMI, ADG, and G:F. However, SBM supplementation produced greater (P < 0.05) DMI and ADG and similar (P > 0.05) G:F compared with UR supplementation. We conclude that supplemental N is important to optimize ruminal function and performance of growing steers fed forage diets supplemented with DCP. Diets with supplemental N mainly from SBM improved diet digestibility and animal performance beyond that achieved by UR.     

Nonstructural carbohydrate supplementation of yearling heifers and range beef cows

A digestion study with 28 yearling heifers (428 +/- 9.9 kg; Exp. 1) and a 2-yr winter grazing trial with 60 crossbred cows (552 +/- 6.9 kg; Exp. 2) were used to determine the effects of level of nonstructural carbohydrate (NSC) supplementation on intake and digestibility of low-quality forage. Treatments were as follows: 1) control, no supplement; 2) 0.32 kg of NSC (1.8 kg/d of soybean hulls and soybean meal; DM basis); 3) 0.64 kg of NSC (1.7 kg/d of wheat middlings; DM basis); and 4) 0.96 kg of NSC (1.7 kg/d of barley and soybean meal; DM basis). Supplements provided 0.34 kg of CP/d and 5.1 Mcal of ME/d. In Exp. 1, heifers were individually fed hay (5.5% CP, DM basis) and their respective supplements in Calan gates for 28 d. Data were analyzed as a completely randomized design. In Exp. 2, cows were individually fed supplement on alternate days, and grazed a single rangeland pasture stocked at 1.8 ha/ animal unit month. Two ruminally cannulated cows were used per treatment to obtain forage extrusa and to measure in situ DM disappearance (DMD) and carboxymethylcellulase (CMCase) activity of particle-associated ruminal microbes. Data were analyzed as a completely randomized design with the effects of treatment, year, and their interaction. In both experiments, Cr2O3 boluses were used to determine fecal output, individual animal was the experimental unit, and contrasts were used to test linear and quadratic effects of NSC level and control vs. supplemented treatments. In Exp. 1, hay and diet DM, NDF, and CP intakes and digestibilities were increased (P < 0.01) by NSC supplementation compared with the control. In Exp. 2, 72-h in situ DMD and CMCase were decreased linearly (P < 0.08) with increasing NSC supplementation. Intake of forage DM, NDF, and CP was decreased linearly (P < 0.01) with increasing NSC supplementation during both years. Supplementation with NSC decreased (P = 0.01) cow BW loss compared with the control in yr 1, whereas in yr 2, cow BW loss was linearly increased (P = 0.03) by increasing NSC supplementation. Supplements containing NSC improved forage digestion and intake when heifers consumed forage deficient in CP relative to energy (digestible OM:CP > 7), but decreased forage digestion and intake when cows grazed forage with adequate CP relative to energy (digestible OM:CP < 7). Forage and supplement digestible OM:CP seemed to be superior predictors of response to supplementation with NSC compared with forage CP levels alone.     

Growth and Reproductive Performance of Holstein Heifers as Affected by Ruminal Degradation of Supplemental Protein

Reproductive performance of primipa-rous and multiparous dairy cows has been improved by increasing the proportion of undegraded intake protein (UIP) in the diet, especially when fish meal (FM) was supplemented. This positive response has not been documented with dairy heifers, in general, or under grazing conditions, in particular. Therefore, the objective of this study was to determine the effects of increasing the UIP level in the supplement on growth and reproductive performance of Holstein heifers in a 104-d grazing trial. A total of 63 heifers (BW ± SD = 317 ± 14 kg) were allotted at random to nine paddocks (7 heifers each) to allow for three replications (paddocks) per treatment. One heifer was later found as a freemartin and, therefore, was excluded from the study. The pasture [81.8% OM, 11.1% CP, and 61.1% NDF (DM basis)] was composed mainly of tall fescue (Festuca arundinacea) and Kentucky bluegrass (Poa pratensis) with a minor proportion of other forages [e.g., white clover (Trifolium repens)]. The heifers were group-fed one of three supplements (1.9 kg DM/d per heifer) based on corn and dry molasses; the supplements also contained soybean meal, FM, or both protein sources to allow for 0, 50, or 100% of supplemental CP from FM. The heifers had ad libitum access to water and mineral-vitamin-molasses blocks. They were synchronized for estrus [two injections (5 mg each of prostaglandin F₂) on d 45 and 56], artificially inseminated on d 59, allowed to graze without the supplement on d 80, and tested for pregnancy via rectal palpation on d 104. Over the 80 d of feeding the supplements, there were no differences (P>0.05) among treatments for ADG (0.87, 0.82, and 0.94 kg), gain-to-supplement ratio (0.42, 0.39, and 0.46), or conception rate (28.6, 38.1, and 35.0%). The absence of significant gain or reproductive responses in this study might have been due to the poor quality forage, the limited amount of supplement fed, or both. Low quality forage also can negatively affect reproduction by decreasing efficiency of ruminal N utilization caused by limited energy supply.     

Effect of fat supplementation and wheat pasture maturity on forage intake and digestion characteristics of steers grazing wheat pasture

Nine ruminally cannulated mixed-breed steers were used in a split-plot design to evaluate effects of fat supplementation and forage maturity on intake, digestibility, and ruminal fermentation. Treatment was the main plot, and stage of forage maturity was the subplot. Treatments were supplements containing mineral pack (M) offered at 114 g/d; M plus fiber as soybean hulls-wheat middlings (MF) offered at 0.50% BW; and MF plus tallow (MFT) offered at 0.625% BW. Stages of wheat maturity were mid-March (MAR) and early April (APR). Steers grazed in a single wheat pasture with supplements offered individually at 0700 h daily. There were supplement type x forage maturity interactions (P < 0.05) for forage OM, CP, and NDF intakes. During MAR, forage OM, CP, and NDF intakes were not affected (P > 0.05) by supplementation. During APR, forage OM, CP, and NDF intakes differed (MF = M > MFT, P < 0.05). There was also supplement type x forage maturity interaction (P = 0.04) for forage OM digestibility. The OM digestibility differed during MAR (M = MF > MFT, P < 0.05) and during APR (MF > M > MFT, P < 0.05). Crude protein digestibility was affected by supplement type (M > MF > MFT, P < 0.05) and stage of forage maturity (MAR > APR, P < 0.01). Rates of DM and NDF ruminal disappearance were not affected (P > 0.05) by supplement or forage maturity. Supplementation increased (P < 0.05) ruminal propionate concentration (19.7, 21.4, and 25.1 +/- 0.49 mol/100 mol for M, MF, and MFT, respectively). Tallow can be used in supplements for cattle grazing wheat pasture to increase energy intake without negatively affecting forage intake or ruminal fermentation, particularly if used in the early stage of wheat maturity.     

Influence of protein type and level on nitrogen and forage use in cows consuming low-quality forage

Minimal quantities of ruminally degradable protein from supplements may improve supplement use efficiency of ruminants grazing dormant forages. In Exp. 1, N retention, ruminal NH(3), serum urea N, and NDF digestibility were evaluated for 12 ruminally cannulated cows (Bos spp.) in an incomplete Latin Square design with 3 periods of 42 d each. Cows were fed weeping lovegrass [Eragrostis curvula (Schrad.) Nees] hay (4.1% CP, 75% NDF, OM basis) at 1.3 % BW/d and offered 1 of 3 sources of CP [urea, cottonseed (Gossypium spp.) meal (CSM); or 50% blood meal and 50% feather meal combination (BFM)] fed to supply 0, 40, 80, or 160 g/d of CP. Beginning on d 22 of supplementation, ruminal contents and serum samples were collected at -2, 0, 3, 6, 9, 12, 18, 24, 30, 36, and 48 h relative to the morning offering of hay. On Day 24, feces and urine were collected for 72 h. In Exp. 2, 4 ruminally cannulated steers were used in a replicated 4 by 4 Latin Square to evaluate use of supplements differing in quantity and ruminal CP degradability. Steers were fed 6.8 kg/d chopped sudangrass [Sorghum bicolor (L.) Moench nothosubsp. drummondii (Steud.) de Wet ex Davidse] hay (3.7% CP, 74% NDF on OM basis) and supplemented with 56 g/d of a salt mineral mix (CON); CON + 28 g/d blood meal + 28 g/d feather meal (BFM); CON + 98 g/d CSM (LCS); or CON + 392 g/d CSM (HCS). Treatments provided 0, 40, 40, or 160 g/d of CP for CON, BFM, LCS, and HCS respectively. In Exp. 1, N use and total tract NDF digestibility were not affected by protein sources or amounts (P ≥ 0.18). Ruminal NH(3) concentrations exhibited a quadratic response over time for UREA (P < 0.05) and was greater with increasing inclusion of urea (P < 0.05); whereas BFM or CSM did not differ (P > 0.05) by amount or across time. In Exp. 2, supplementation had a tendency (P = 0.09) to increase DM disappearance. Supplementation also increased (P < 0.01) serum glucose concentrations; however, no difference (P ≥ 0.28) was found between supplements. Serum urea N and ruminal NH(3) concentrations were increased (P ≤ 0.01) in steers fed HCS. Feeding low quantities of a high-RUP supplement maintained rumen function without negatively affecting DM or NDF digestibility of a low-quality forage diet.     

Digestibility of prairie hay diets supplemented with different levels of magnesium-mica by beef heifers

Four ruminally fistulated, nonpregnant, nonlactating heifers (515 +/- 7.9 kg) were offered chopped (10-cm screen size) prairie hay for ad libitum consumption with 1.8 kg/d of supplements to provide 0, 45, 113, or 181 g/d of magnesium-mica (MM) in a 4 x 4 Latin square design experiment. Heifers were adapted to diets for 7 d in drylot followed by a 19-d confinement period in individual stalls within a metabolism facility. Total feces and urine were collected for 5 d, daily intake and water consumption were monitored for 16 d, and in situ disappearance of fiber (prairie hay) and CP (soybean meal) were determined during the confinement period. Ruminal samples for fermentation product analyses were collected at feeding and every 2 h thereafter for 12 h on d 18, and rumens were evacuated at 1100 on d 19 to determine rumen fill. Cubic responses (P < .05) to MM level were observed for DM, OM, NDF, and ADF digestion and were characterized by a tendency for improved digestion with 45 g/d compared with the control diet, followed by a suppressive effect on digestion with 113 g/d, then little effect with 181 g/d MM. In situ NDF disappearance at 72 and 96 h tended (P < . 10) to be influenced quadratically by level of MM, but MM level had no apparent effect on ruminal fill and passage rate, ciliated protozoa counts, in situ rate of disappearance of fiber or CP, or nitrogen balance. Therefore, feeding MM at low levels to heifers consuming a prairie hay diet with a 20% CP supplement seemed to be beneficial for feed digestion with no measurable negative impact on intake or ruminal protein or fiber digestion.     

Determination of nitrogen balance in goats fed a meal produced from hydrolyzed spent hen hard tissues

To provide an economically viable and environmentally sound method for disposing of spent laying hens, we manufactured a proteinaceous meal from the hard tissue fraction of mechanically deboned laying hens (primarily feathers, bones, and connective tissue). We hydrolyzed the hard tissue and coextruded it with soybean hulls to create a novel feather and bone meal (FBM) containing 94.2% DM, 23.1% CP, 54.5% NDF, and 7.3% fat (DM basis). We evaluated the FBM in supplements for meat goats in which it provided 0, 20, 40, or 60% of the N added to the supplement compared with a negative control supplement with no added N source. The remainder of the N was contributed by soybean meal (SBM). Supplementation of N resulted in greater DMI than the negative control (P = 0.005), and DMI changed quadratically (P = 0.11) as FBM increased in the supplement. Digestibility of DM was similar in all diets, including the negative control (P > 0.10). Fiber digestibility increased linearly as dietary inclusion of FBM increased (P = 0.04 for NDF, P = 0.05 for ADF), probably as a result of the soybean hulls in the FBM. Nitrogen digestibility declined linearly from 60.5% with 0% FBM to 55.6% with 60% FBM (P = 0.07), but N retention changed by a quadratic function as FBM replaced SBM (P = 0.06). Negative control goats had less N digestibility (P < 0.001) and N retention (P = 0.008) than N-supplemented goats. Feather and bone meal had a greater proportion of ruminally undegradable B(3) protein than SBM (23.1 vs. 0.3% of CP, respectively). Ruminal VFA and pH were unaffected by replacing SBM with FBM, but supplying no source of N in the concentrate resulted in reduced total VFA in ruminal fluid (P = 0.04). Ruminal ammonia concentration increased quadratically (P = 0.07) as FBM increased, reflecting increased intake, and it was much less in unsupplemented goats (P < 0.001). Serum urea had less variation between 0 and 4 h after feeding in goats receiving 40 or 60% of added N as FBM in comparison with those receiving only SBM or 20% FBM. Feather and bone meal promoted a more stable rumen environment, possibly because of reduced rates of protein degradation within the rumen. A palatable by-product meal for ruminants can be made from spent laying hen hard tissue, one that supports N metabolism similar to that of traditional protein sources.     

Effects of energy supplementation frequency and forage quality on performance, reproductive, and physiological responses of replacement beef heifers

The objective of this study was to compare performance, physiological, and reproductive responses of beef heifers consuming forages differing in nutritional quality and offered a low-starch energy supplement at 2 different frequencies. Forty-eight Brahman × British heifers (initial age = 294 ± 3 d) were allocated into 1 of 16 drylot pens (3 heifers/pen) which were randomly assigned to receive, in a 2 × 2 factorial arrangement of treatments: 1) low-quality hay [LQ; stargrass (Cynodon nlemfuensis) with 8% CP and 81% NDF, DM basis] and daily supplementation (S7); 2) LQ and supplementation 3 times weekly (S3); 3) medium-quality hay [MQ; bermudagrass (C. dactylon) with 12% CP and 74% NDF, DM basis] and S7; and 4) MQ and S3. Throughout the study (d 0 to 120), hay was offered in amounts to ensure ad libitum access, and a supplement based on soybean hulls and wheat middlings was offered at weekly rates of 15.8 and 7.9 kg/heifer (DM basis) for LQ and MQ, respectively. Forage and total DMI were evaluated daily, from d 20 to 26, d 34 to 40, and d 48 to 54. Blood samples were collected weekly for determination of plasma progesterone to evaluate puberty attainment. Blood samples were also collected daily, from d 13 to 16, d 27 to 30, d 41 to 44, and d 55 to 58 for determination of plasma urea nitrogen (PUN), glucose, insulin, IGF-I, and NEFA. On d 60, heifers were reallocated by treatment into 4 paddocks and exposed to Angus bulls (1:12 bull:heifer ratio) until d 120. Date of conception was estimated retrospectively by subtracting gestation length (286 d) from the calving date. Heifers receiving S7 had similar (P = 0.52) ADG compared with S3 heifers (0.27 vs. 0.25 kg/d). Heifers provided S7 had less daily variation in hay DMI and plasma concentrations of glucose, NEFA, and IGF-I compared with S3 cohorts (supplementation frequency × day interaction; P < 0.01). Similarly, heifers offered MQ and LQ and receiving S7 had less daily variation in total DMI, energy and protein intake, and plasma concentrations of PUN compared with heifers offered MQ and LQ and receiving S3 (hay quality × supplementation frequency × day interaction; P < 0.01). Attainment of puberty and pregnancy were hastened in S7 heifers compared with S3 heifers (supplementation frequency × week interaction; P < 0.02). Therefore, reproductive development of beef replacement heifers consuming diets based on low- and medium-quality forages are enhanced when low-starch energy supplements are offered daily instead of 3 times weekly.     

Effect of corn- vs molasses-based supplements on trace mineral status in beef heifers

Two studies were conducted to compare the availability of trace minerals offered to Brahman-crossbred heifers in either grain- or molasses-based supplements. Heifers were randomly assigned to bahiagrass pastures of equal size (n = 3 and 2 heifers/ pasture with 6 and 4 pastures/treatment for Experiment 1 and 2, respectively). Two supplements were formulated using corn and cottonseed meal (DRY) or molasses and cottonseed meal (LIQ). In Experiment 2, a third treatment consisted of the DRY supplement with additional S to equal the amount naturally supplied by the LIQ treatment (DRY+S). Supplements were formulated to provide, on average, 1.5 kg of TDN and 0.3 kg of CP/heifer daily and were fed three times weekly. Supplements also were fortified to provide 140, 76, and 63 mg of Cu, Mn, and Zn per heifer daily. Individual heifer weights were collected at the start and conclusion of the study, following a 12-h shrink. Plasma ceruloplasmin and liver Cu, Mn, Mo, Fe, and Zn concentrations were determined on d 0, 29, 56, and 84 in Experiment 1, and d 0, 32, 57, and 90 in Experiment 2. No differences were detected in heifer BW change (-9.3 and -7.3 kg for DRY and LIQ in Experiment 1, and 51.7, 46.3, and 46.7 kg for DRY, DRY+S, and LIQ in Experiment 2, respectively). In both experiments, liver Fe, Mn, and Zn concentrations were not affected by supplement treatment. Molybdenum tended (P = 0.06 and 0.10 for Experiments 1 and 2, respectively) to accumulate in the liver of heifers fed molasses-based supplements. In Experiment 1, Cu accumulation was less (P < 0.001) in heifers fed the liquid supplements (271 vs 224, 286 vs 202, and 330 vs 218 ppm, for DRY and LIQ supplements on d 29, 56, and 84, respectively). In Experiment 2, heifers receiving Cu from DRY supplements had a 155-ppm increase in liver Cu concentration, which was greater (P = 0.03) than DRY+S (87 ppm increase) and LIQ (P < 0.001; 13 ppm increase). Although lower than heifers receiving DRY, heifers receiving DRY+S had greater (P = 0.02) liver Cu concentrations than heifers receiving LIQ by the end of the study. In both experiments, plasma ceruloplasmin concentrations were highest (P < 0.04) in heifers receiving DRY supplement. The results of these studies suggest that components in molasses-based supplements decrease the accumulation of Cu in the liver of beef heifers. The S and Mo components of molasses may be responsible, at least in part, for this antagonism.     

Effects of increasing level of supplemental barley on forage intake, digestibility, and ruminal fermentation in steers fed medium-quality grass hay

Objectives of this research were to evaluate effects of increasing level of barley supplementation on forage intake, digestibility, and ruminal fermentation in beef steers fed medium-quality forage. Four crossbred ruminally cannulated steers (average initial BW = 200 +/- 10 kg) were used in a 4 x 4 Latin square design. Chopped (5 cm) grass hay (10% CP) was offered ad libitum with one of four supplements. Supplements included 0, 0.8, 1.6, or 2.4 kg of barley (DM basis) and were fed in two equal portions at 0700 and 1600. Supplements were fed at levels to provide for equal intake of supplemental protein with the addition of soybean meal. Forage intake (kg and g/kg BW) decreased linearly (P < 0.01), and total intake increased linearly (P < 0.03) with increasing level of barley supplementation. Digestible OM intake (g/kg BW) increased linearly (P < 0.01) with increasing level of barley supplementation; however, the majority of this response was observed with 0.8 kg of barley supplementation. Treatments had only minor effects on ruminal pH, with decreases occurring at 15 h after feeding in steers receiving 2.4 kg of barley supplementation. Total-tract digestibility of DM, OM, NDF, and CP were increased (P < 0.04) with barley supplementation; however, ADF digestibility was decreased by 1.6 and 2.4 kg of barley supplementation compared with controls. Ruminal ammonia concentrations decreased linearly (P < 0.01) at 1 through 15 h after feeding. Total ruminal VFA concentrations were not altered by dietary treatments. Ruminal proportions of acetate and butyrate decreased (P < 0.10) in response to supplementation. Rate, lag, and extent (72 h) of in situ forage degradability were unaffected by treatment. Generally, these data are interpreted to indicate that increasing levels of barley supplementation decrease forage intake, increase DM, OM, and NDF digestibility, and indicate alteration of the ruminal environment and fermentation patterns.     

不同蛋白和中性洗涤纤维水平对瘤胃发酵、消化和微生物蛋白合成的影响

以3头装有瘤胃瘘管的干奶牛作为瘤胃液供体,用体外培养法研究不同日粮蛋白和中性洗涤纤维(NDF)水平对瘤胃发酵、消化和微生物蛋白合成的影响。采用2×3双因子完全随机设计,粗蛋白水平14%、16%和18%,NDF水平为32%和36%。体外发酵后2、4、6、12、24 h取瘤胃液测定pH、NH3-N浓度和微生物蛋白含量,发酵结束后测定饲料中干物质(DM)、NDF和酸性洗涤纤维(ADF)消化率。结果表明:随着蛋白水平升高,瘤胃发酵pH有增加趋势(P=0.079),显著提高NDF和ADF消化率和细菌蛋白合成量(P<0.05),但不影响DM消化率和原虫蛋白的合成量(P>0.05);日粮中NDF水平显著影响瘤胃pH、NH3-N浓度和ADF消化率(P<0.05),但不影响DM和NDF消化率以及微生物蛋白的合成量(P>0.05)。本试验条件下,日粮中16%CP和32%NDF组可在一定程度上促进瘤胃发酵,提高纤维消化率以及微生物蛋白的合成量。     

Influence of supplemental nitrogen source on digestion of nitrogen, dry matter and organic matter and on in vivo rate of ruminal protein degradation

Seven Holstein steers (340 kg) fitted with ruminal, duodenal and ileal cannulae were used to measure the influence of supplemental N source on digestion of dietary crude protein (CP) and on ruminal rates of protein degradation. Diets used were corn-based (isonitrogenous, 12% CP on a dry matter basis, and isocaloric, 80% total digestible nutrients) with urea, soybean meal (SBM), linseed meal (LSM) or corn gluten meal (CGM) as supplemental N. Ruminal ammonia N concentrations were higher (P less than .05) in steers fed LSM than in those fed CGM, but did not differ from those in steers fed urea or SBM (11.7, 6.7, 9.1 and 9.2 mg/100 ml, respectively). Due to the high degradability of urea, ruminal digestion of dietary CP was greater (P less than .05) in steers fed urea than in those fed CGM, but intermediate in steers fed SBM and LSM (58.4, 48.8, 53.1 and 53.9%, respectively). Flow of bacterial nonammonia N to the duodenum was highest (P less than .05) in steers fed SBM or LSM, intermediate (P less than .05) for urea and lowest (P less than .05) for CGM (86.8, 86.1, 76.3 and 65.9 g/d, respectively). Efficiency of bacterial protein synthesis was lowest in steers fed CGM and differed (P less than .05) from SBM (15.6 vs 21.8 g N/kg organic matter truly digested, respectively). Rate of ruminal digestion for SBM-CP differed (P less than .05) from that of CGM-CP but not from that of LSM-CP (17.70, 5.20 and 10.13%/h, respectively). The slow rate of ruminal degradability of CGM resulted in increased amounts of dietary protein reaching the intestinal tract but lower amounts of bacterial protein, thus intestinal protein supply was not appreciably altered.     

Low- and high-quality forage utilization by heifers and mature beef cows.

Eight cows (7 to 9 yr old, 522 kg) and six heifers (10 mo old, 169 kg) were fed either alfalfa hay (18.7% CP) or mature brome hay (5.1% CP) to determine the effect of cattle age on apparent forage utilization. Cattle were fitted with ruminal and duodenal cannulas and were individually fed once daily (ad libitum intake, 1000). The split-plot design consisted of age (whole-plot) and two sampling periods feeding alfalfa or brome hay (subplot). Each period consisted of 28 d: d 1 to 13 for adaptation, d 13 to 20 for feed intake determination, and d 20 to 28 for sampling. Nylon bags containing NDF substrate from alfalfa or brome hay were incubated ruminally for 0, 3, 6, 12, 24, 48, 96, and 192 h to determine the rate and extent of fiber degradation. Ruminal liquid dilution rate and fermentation characteristics were conducted on d 27. Ruminal fill was determined by total evacuation at 0800 on d 28. Cows consumed more feed (BW.75; P<.01) and had greater ruminal OM fill (P = .04) but had similar fluid fill (P = .88) compared with heifers. Ruminal liquid dilution rate was greater in cows than in heifers (P<.01). The rate of in situ NDF degradation was 3 and .5% per hour greater in cows than in heifers when alfalfa and brome hay were fed, respectively (age x hay, P<.01). Ruminal NDF digestibility as a percentage of intake was greater in cows than in heifers (P<.01). Numbers of ruminal cellulolytic bacteria were not affected by treatment (P>.21). These data indicate that mature cows have a smaller ruminal fluid fill that turns over more rapidly, and this may be responsible for a faster rate of ruminal fiber degradation in cows than in young heifers.