Effects of physical preparation of diets and inclusion rate of modified wet distillers grains with solubles on production and rumen measurements of lactating dairy cows.

Our objective was to determine if methods for preparing total mixed ration [TMR; horizontal paddle mixer with knives (PK) vs. vertical auger (VA) mixer] would alter the physical form of the TMR and affect utilization of diets with increasing amounts of modified wet distillers grains with solubles (MWDGS). Holstein cows (n = 24 with 12 ruminally cannulated; 144 d in milk ± 31 d at start) were used in a split-plot design with mixer type as the whole plot and MWDGS concentrations as subplots in a replicated 3 × 3 Latin square arrangement with 35-d periods. Inclusion rates of MWDGS were 10, 20, and 30% of dietary dry matter, primarily replacing corn, soybean meal, soyhulls, and whole cottonseed. Feed dry matter intake (DMI) was less for PK (23.8 kg/d) than for VA (25.7 kg/d), but was unaffected by MWDGS concentration. Milk production did not differ by concentration of MWDGS or by interaction of MWDGS × mixer. Milk fat percentage declined with increasing MWDGS but the interaction between mixer and MWDGS showed that decreases were larger with VA mixing. Cows fed the diet containing 30% MWDGS mixed with PK averaged 3.45% (1.24 kg/d) milk fat, whereas cows fed the same diet mixed with VA averaged 2.81% (1.10 kg/d) fat. Concentrations of trans-10,cis-12 C18:2 in milk fat likely explain the differences observed in milk fat yield; the concentration of trans-10,cis-12 C18:2 increased as MWDGS was increased and the MWDGS × mixer interaction showed that VA had greater concentrations. Greater mean particle size and increased variation in particle size with VA may partially explain differences in milk fat via increased sorting that allowed for an altered rumen environment and favored alternative biohydrogenation pathways. Feed conversion efficiency (FCE; energy-corrected milk/DMI) decreased linearly as MWDGS increased, but FCE tended to be maintained when higher MWDGS diets were mixed using PK rather than VA. Ruminal pH and ammonia concentration decreased linearly as MWDGS increased. The PK mixer resulted in greater FCE when higher amounts of MWDGS were fed, primarily because milk fat content and yield were not as depressed and DMI was lower at similar milk yields.

The effects on digestibility and ruminal measures of chemically treated corn stover as a partial replacement for grain in dairy diets.

Alkaline treatment of gramineous crop residues can convert an abundant, minimally utilized, poorly digestible straw into a moderately digestible feedstuff. Given the volatile nature of grain prices, substitution of treated stover for grain was investigated with dairy cows to provide insights on ruminal and digestibility effects of a feed option that makes use of alternative, available resources. The objective of this study was to evaluate changes in diet digestibility and ruminal effects when increasing levels of calcium oxide-treated corn stover (CaOSt) were substituted for corn grain in diets of lactating cows. Mature corn stover was treated with calcium oxide at a level of 50g∙kg(-1) dry matter (DM), brought up to a moisture content of 50% following bale grinding, and stored anaerobically at ambient temperatures for greater than 60d before the feeding experiment. Eight ruminally cannulated Holstein cows averaging 686kg of body weight and 35kg of milk∙d(-1) were enrolled in a replicated 4×4 Latin square, where CaOSt replaced corn grain on a DM basis in the ration at rates of 0, 40, 80, and 120g∙kg(-1) DM. All reported significant responses were linear. The DM intake declined by approximately 1kg per 4% increase in CaOSt inclusion. With increasing replacement of corn grain, dietary neutral detergent fiber (NDF) concentration increased. However, rumen NDF turnover, NDF digestibility, NDF passage rate, and digestion rate of potentially digestible NDF were unaffected by increasing CaOSt inclusion. Total-tract organic matter digestibility declined by 5 percentage units over the range of treatments, approximately 1.5 units per 4-percentage-unit substitution of CaOSt for grain. With increasing CaOSt, the molar proportions of butyrate and valerate declined, whereas the lowest detected ruminal pH increased from 5.83 to 5.94. Milk, fat, and protein yields declined as CaOSt increased and DM intake declined with the result that net energy in milk declined by approximately 1 Mcal per 4% increase in CaOSt. Time spent ruminating (min∙kg(-1) DM intake) increased with increasing CaOSt, though total minutes per day were unaffected. These insights on the effect of substitution of treated corn stover for corn grain may be used to predict the effect on nutrient supply to the cow over a range of substitution levels. The acceptability of the effect will depend on the economics of milk production and availabilities of feedstuffs.

Effects of grind size when alkaline treating corn residue and impact of ratio of alkaline-treated residue and distillers grains on performance of finishing cattle.

Two studies were conducted to optimize use of alkaline-treated corn stover and wheat straw and distillers grains as partial corn replacements. In Exp. 1, a finishing experiment used 30 pens (12 steers/pen) of calf-fed steers (initial BW = 374 ± 23.9 kg) with a 2 × 2 + 1 factorial arrangement of treatments with 6 replications per treatment. Factors were grind size, where corn stover was processed through a 2.54- or 7.62-cm screen, and chemical treatment (corn stover either fed in native, non-treated form [NT; 93.4% DM] or alkaline treated [AT; 5% CaO hydrated to 50% DM]). No interactions (P ≥ 0.38) were noted between grind size and chemical treatment. Feeding AT compared with NT improved (P ≤ 0.02) final BW, ADG, and G:F. Reducing grind size improved (P ≤ 0.01) ADG and G:F, and no interaction with chemical treatment was observed. Steers fed AT had similar DMI, ADG, G:F, and carcass characteristics compared with a 5% roughage control that contained 15 percentage units (DM basis) more corn. In Exp. 2, 60 individually fed steers (initial BW = 402 ± 61.4 kg) were randomly assigned to 10 diets. Six treatments evaluated 10, 25, or 40% dry-rolled corn (DRC), which was replaced with either a 2:1 or 3:1 ratio (DM basis) of modified distillers grains plus solubles (MDGS) and treated corn stover analyzed as a 2 × 3 factorial. An additional 3 treatments were added where a 3:1 ratio of MDGS:straw were compared with a 3:1 ratio of MDGS:stover. As DRC increased, G:F (P = 0.06) quadratically increased for 3:1 MDGS:stover diets. Increasing DRC increased (P = 0.07) G:F in treated stover diets, regardless of ratio. Increasing DRC increased (P = 0.10) ADG for 3:1 ratios for both straw and stover. Reducing grind size, feeding a maximum of 20% treated crop residue, and maintaining at least 25% corn in the diet are strategies for optimizing cattle performance when replacing dry-rolled and high-moisture corn with treated crop residues and distillers grains.

Effects of feeding processed corn stover and distillers grains on growth performance and metabolism of beef cattle.

Objectives were to evaluate the effects of replacing corn in feedlot finishing diets with processed corn stover (CS), processed by various combinations of chemical and physical methods, and modified wet distillers grain with solubles (MWDGS) on growth performance, carcass characteristics, digestibility, and ruminal metabolism of cattle. Corn stover was physically processed (ground or extruded) and chemically processed with alkaline agents (CaO and NaOH) to reduce the crystallinity of the lignocellulosic structure. In Exp. 1 steers ( = 18, initial BW = 385 ± 32 kg) and heifers ( = 41, initial BW = 381 ± 27 kg) were allotted to 1 of 5 dietary treatments: 1) 55% dry, cracked corn, 35% MWDGS, 5% vitamin-mineral supplement, and 5% untreated ground CS (), 2) CS treated with 5% CaO (DM basis) and stored in an Ag-Bag (BGCS), 3) CS treated with 5% CaO (DM basis) and extruded (5 EXCS), 4) CS treated with 4% CaO and 1% NaOH (DM basis) and extruded (4,1 EXCS), or 5) CS treated with 3% CaO and 2% NaOH (DM basis) and extruded (3,2 EXCS). Extruded CS was hydrated to 34% moisture, then an additional 16% water was added, as a solution carrying CaO or NaOH or both, via a calibrated pump during processing through a dual-shafted encased extruder (Readco Kurimoto Continuous Processor, York, PA) with the desired exiting temperature of 76.7°C ± 2.8°C. All treated CS diets contained 20% CS and 40% MWDGS (DM basis) to replace 20% corn when compared to CON. There were no effects ( ≥ 0.20) of dietary treatment on ADG, G:F, 12th-rib back fat, marbling score, LM area, or yield grade. However, cattle fed CON had increased ( = 0.02) DMI compared to cattle fed the treated CS diets. In Exp. 2, using the same diets as fed in Exp. 1, ruminally cannulated steers ( = 5; initial BW = 417 ± 21 kg) were fed for 90% of ad libitum intake in a 5 × 5 Latin square design. Apparent digestibility of NDF and ADF increased ( < 0.01) when cattle were fed treated CS diets compared with CON, regardless of the treatment applied. Ruminal pH was reduced ( = 0.02) in cattle fed BGCS from 0 to 6 h postfeeding compared with cattle fed all other diets. Cattle fed the treated CS diets had the greatest ( < 0.01) mean acetate concentrations, which increased ( = 0.01) total VFA concentrations. Replacing a portion of the corn with treated CS in feedlot diets containing MWDGS increased fiber digestibility without affecting feedlot cattle gain, efficiency, marbling score, or LM area.

Effects of twenty percent alkaline-treated corn stover without or with yucca extract on performance and nutrient mass balance of finishing steers fed modified distillers grains-based diets.

Two experiments were conducted with 192 steers each (during the winter [November to May] or summer [June to October]) to evaluate 3 diets with or without Yucca schidigera extract in a 3 × 2 factorial on steer growth performance and N mass balance. One factor was diet (DM basis): 1) 5% untreated corn stover, 51% corn, and 40% modified distillers grains plus solubles (MDGS; CON); 2) 20% calcium oxide-treated corn stover (CaO added at 5% of stover DM), 40% MDGS, and 36% corn (TRT); or 3) 20% untreated corn stover, 40% MDGS, and 36% corn (NONTRT). The other factor was dietary extract at 0 (NOYE) or 1.0 g/d per steer (YE). No interaction between diet and YE was detected (P > 0.51) for growth performance and carcass traits in winter and only for DMI in summer. Final BW, ADG, DMI, or G:F were not different (P ≥ 0.28) between cattle fed CON and TRT, whereas cattle fed NONTRT had lesser ADG, HCW, and G:F compared to CON and TRT in the winter experiment. During the summer, final BW and ADG tended to be greater (P ≥ 0.07) for CON compared to TRT. Cattle fed TRT had reduced (P < 0.01) G:F compared to CON. No difference was observed (P ≥ 0.36) between YE and NOYE in the winter experiment for performance or carcass traits. In the summer, cattle fed YE had greater (P < 0.02) HCW, ADG, and DMI compared to NOYE. In the summer experiment, cattle fed YE had greater (P < 0.01) N intake, N excretion, and amount of N lost (kg/steer) compared to NOYE, but no difference (P = 0.33) was observed for percentage of N volatilized (% of excretion). Diet had no effect (P > 0.18) on amount (kg/steer) or percentage of N volatized in the winter or summer. All diets had similar amounts (P > 0.13) of DM and OM removed from the pen surface in both summer and winter. Feeding CaO-treated corn stover as a partial grain replacement had no impact on performance in winter but decreased G:F in summer. Although high-fiber diets increased the amount of OM on pen surfaces, they did not impact N volatilized. Feeding a Y. schidigera extract did not affect N balance or manure characteristics.

Digestibility and performance of steers fed low-quality crop residues treated with calcium oxide to partially replace corn in distillers grains finishing diets.

Two studies were conducted to identify methods for treating crop residues to improve digestibility and value in finishing diets based on corn grain and corn wet distillers grain with solubles (WDGS). In Exp. 1, 336 yearling steers (initial BW 356 ± 11.5 kg) were used in a 2 × 3 + 1 factorial arrangement of treatments with 6 pens per treatment. Factors were 3 crop residues (corn cobs, wheat straw, and corn stover) and 2 treatments where crop residues were either fed (20% diet DM) in their native form (NT) or alkaline treated with 5% CaO (DM basis) and hydrated to 50% DM before anaerobic storage (AT). Intakes were not affected by diet (F test; P = 0.30). An interaction between chemical treatment and residue (P < 0.01) was noted for final BW, ADG, G:F, and HCW. Greater final BW was observed for treated stover (4.6%) and straw (5.6%) compared with NT residues; however, AT and NT cobs were similar. Treated straw (9.7%) and stover (12.5%) resulted in greater ADG (P < 0.01) and improved G:F (10.7% and 5.0%, respectively; P < 0.01) compared with NT forms. In Exp. 2, ruminally fistulated steers (n = 5) were used in an unbalanced 5 × 7 incomplete Latin square design with a 2 × 3 + 1 factorial arrangement of treatments. Factors were crop residue (corn cobs, wheat straw, and corn stover) and chemical treatment (NT or AT) fed at 25% of diet DM. Greater DM (73.7% vs. 66.1%; P < 0.01), OM (77.0% vs. 68.5%; P < 0.01), fat (89.2 vs. 85.2; P = 0.02), and NDF (66.8% vs. 51.5%; P < 0.01) digestibilities were noted for AT than for NT. However, no difference (P > 0.10) was observed between control (46% corn; DM basis) and AT (31% corn; DM basis) for DM digestibility (70.7% vs. 73.7%) or OM digestibility (72.1% vs. 77.0%). Dry matter intakes were not different between treated and untreated diets (P = 0.38), but lower (P < 0.01) NDF intake was observed for treated diets (3.1 vs. 3.5 kg/d), suggesting that CaO treatment was effective in solubilizing some carbohydrate. These data suggest that 15% replacement of corn and 10% untreated residue with treated forage result in a nutrient supply of OM similar to that of the control. The improvements in total tract fiber digestibility that occurred when treated forages were fed may have been related to increased digestibility of recoverable NDF and not to increased ruminal pH. Feeding chemically treated crop residues and WDGS is an effective strategy for replacing a portion of corn grain and roughage in feedlot diets.

Energy concentration and amino acid digestibility in corn and corn coproducts from the wet-milling industry fed to growing pigs.

Two experiments were conducted to determine DE and ME and the apparent ileal digestibility (AID) and the standardized ileal digestibility (SID) of CP and AA in corn and corn coproducts (high-fat corn germ [HFCG], corn bran, liquid corn extractives [LCE], and a mixture of corn germ meal and LCE [CGM-LCE]) fed to growing pigs. In Exp. 1, 40 growing barrows (initial BW: 33.4 ± 5.77 kg) were housed individually in metabolism cages and randomly allotted to 1 of 5 diets. A corn-based diet (97.4% corn) and 4 diets that contained both corn and each of the corn coproducts were formulated. Each diet was fed to 8 pigs. Feces and urine samples were collected using the marker to marker method with 5-d adaptation and 5-d collection periods. The DE and ME were calculated using the difference procedure. The concentrations of DE and ME in HFCG, corn bran, LCE, and CGM-LCE were less (P < 0.05) than in corn. Among corn coproducts, the concentration of DE in HFCG was greater (P < 0.05) than in corn bran, but the DE in corn bran was not different from DE values in LCE and CGM-LCE. No differences were observed in the ME concentrations among corn coproducts. In Exp. 2, 6 growing barrows (initial BW: 96.6 ± 1.16 kg) with a T-cannula in the distal ileum were randomly allotted to a 6 × 6 Latin square design with 6 diets and 6 periods. A N-free diet and 5 diets that contained corn, HFCG, corn bran, LCE, or CGM-LCE as the sole source of CP and AA were formulated. Each period lasted 7 d and ileal digesta were collected on d 6 and 7 of each period. The SID of CP and all indispensable AA was greater (P < 0.05) in corn than in all corn coproducts with the exception that the SID of Lys in corn was not different from the SID of Lys in HFCG, and the SID of Trp in corn was also not different from the SID of Trp in CGM-LCE. Among corn coproducts, the SID of CP, Arg, and Lys were greater (P < 0.05) in HFCG and CGM-LCE than in corn bran, the SID of Lys and Val was greater (P < 0.05) in LCE than in corn bran, and the SID of Arg was greater (P < 0.05) in HFCG and CGM-LCE than in LCE, but for the remaining indispensable AA, no differences among corn coproducts were observed. In conclusion, the corn coproducts used in these experiments contain less ME and have reduced SID of most AA compared with corn, but there are no differences in ME among corn coproducts and only few differences in the SID of indispensable AA among HFCG, corn bran, LCE, and CGM-LCE.

Effect of vitamin E source, natural versus synthetic, and quantity on serum and tissue alpha-tocopherol concentrations in finishing swine.

Relative vitamin E status of pigs fed natural or synthetic vitamin E was evaluated based on serum and tissue alpha-tocopherol concentrations. Individually fed finishing gilts at a BW of 70.5 kg (n = 24) were allotted to dietary treatments based on initial BW. The 5 dietary treatments consisted of a positive control diet using synthetic vitamin E acetate (Syn E Ac) supplemented at 22 mg/kg, and 4 dietary levels of natural vitamin E acetate (Nat E Ac) supplemented at 6.71, 8.33, 11.00, and 16.18 mg/kg of diet. Before initiation of the 32-d experiment, pigs were fed a non-vitamin E-fortified diet for 30 d. Diets were formulated to contain true ileal digestible lysine of 0.9 and 0.8% for the pretest and test diets. Serum samples were collected on d 15 and 32, whereas tissue samples were collected on d 32 for alpha-tocopherol analysis. Serum alpha-tocopherol concentrations on d 15 and 32 were greater (P < 0.05) in pigs fed 8.33, 11.00, or 16.18 mg/kg of Nat E Ac than in pigs fed 22 mg/kg of Syn E Ac. When compared with pigs fed 22 mg/kg of Syn E Ac, alpha-tocopherol concentrations were greater (P < 0.05) in 6 tissues (heart, kidney, spleen, liver, lung, and adipose) in pigs fed 16.18 mg/kg of Nat E Ac; greater (P < 0.05) in heart, kidney, spleen, liver, and adipose tissue in pigs fed 11.00 mg/kg of Nat E Ac; and greater (P < 0.05) in spleen, loin, and adipose tissue in pigs fed 8.33 mg/kg of Nat E Ac. As dietary Nat E Ac increased from 6.71 to 16.18 mg/kg, serum alpha-tocopherol increased linearly (P < 0.01) on d 15 and 32 of the experiment. Increasing dietary Nat E Ac linearly increased (P < 0.05) alpha-tocopherol concentrations for lung, heart, kidney, spleen, and liver. These results indicate that Nat E Ac was an effective vitamin E source and its relative bioavailability was substantially greater than 1.36 for finishing swine when compared with Syn E Ac.

Feeding value of glycerol as a replacement for corn grain in rations fed to lactating dairy cows.

Growth of the corn ethanol industry has created a need for alternatives to corn for lactating dairy cows. Concurrent expansion in soydiesel production is expected to increase availability and promote favorable pricing for glycerol, a primary co-product material. The objective of this study was to determine the feeding value of glycerol as a replacement for corn in diets fed to lactating dairy cattle. Sixty lactating Holstein cows housed in individual tie stalls were fed a base diet consisting of corn silage, legume forages, corn grain, soyhulls, roasted soybeans, and protein supplements. After a 2-wk acclimation period, cows were fed diets containing 0, 5, 10, or 15% refined glycerol for 56 d. Cows were milked twice daily and weekly milk samples were collected. Milk production was 36.3, 37.2, 37.9, and 36.2 +/- 1.6 kg/d and feed intake was 23.8, 24.6, 24.8, and 24.0 +/- 0.7 kg/d for 0, 5, 10, and 15% glycerol treatments, respectively, and did not differ except for a modest reduction in feed intake during the first 7 d of the trial for 15% glycerol (treatment x time effect). Milk composition was not altered by glycerol feeding except that milk urea nitrogen was decreased from 12.5 +/- 0.4 to 10.2 +/- 0.4 mg/dL with glycerol addition. Cows fed diets containing 10 and 15% glycerol gained more weight than those fed rations containing 0 or 5% glycerol but body condition scores did not differ with glycerol feeding. The data indicate that glycerol is a suitable replacement for corn grain in diets for lactating dairy cattle and that it may be included in rations to a level of at least 15% of dry matter without adverse effects on milk production or milk composition.

Nutrient digestion and performance by lambs and steers fed thermochemically treated crop residues.

Five studies were conducted to determine nutrient digestibility and performance of lambs and steers fed thermochemically treated crop residues and distillers dried grains with solubles (DDGS) as a corn replacement pellet (CRP; 75% residue:25% DDGS, DM basis). Fifteen Hampshire, Suffolk, or Dorset wethers (BW 33.3 +/- 5.0 kg) were utilized to evaluate nutrient digestibility of the unprocessed native (NAT) and CRP [Exp. 1: wheat straw (WS); Exp. 2: corn stover (CS); Exp. 3: switchgrass (SWG) and corn fiber:wheat chaff (CFWC)] when limit fed (Exp. 1 and 2: 1.8% of BW daily; Exp. 3: 2.5% of BW daily) compared with a 60% corn diet. In Exp. 4, 56 individually fed Dorset-cross wether lambs (BW 32.0 +/- 1.4 kg) were utilized to compare performance and digestibility of WS, wheat chaff (WC), corn fiber (CF), a 3:1 blend of corn fiber:wheat straw (CFWS), a 3:1 blend of CFWC, and SWG-CRP fed for ad libitum intake compared with a 45% corn diet. In Exp. 5, 32 individually fed Holstein steers (BW 185.2 +/- 0.9 kg) were used to evaluate performance and digestibility of diets containing corn, WS-CRP, CFWC-CRP, or NAT-WS fed for ad libitum intake. Crop residues were processed with 5% calcium oxide (DM basis) and 35% water in a double-shaft enclosed mixer (Readco Kurimoto Continuous Processor, York, PA) and subsequently pelleted with DDGS to form CRP. Feeding lambs WS-CRP (Exp. 1) or CS-CRP (Exp. 2) increased digestion of DM, NDF, and ADF compared with NAT (P < 0.05). In Exp. 3, feeding CFWC-CRP increased total tract NDF digestibility and ADF digestibility (P < 0.05). Experiment 4 final BW were greatest for control lambs and least for lambs fed CFWS-CRP or SWG-CRP. Body weight gains for lambs fed CRP averaged 15.9% less than control (P < 0.05). Lambs fed CRP diets had greater (P < 0.05) NDF and ADF intake and output. In Exp. 5, steers fed the corn or 2 CRP diets gained similarly and faster (P < 0.05) than those fed the NAT-WS diet. Steers fed the control corn diet were more efficient (P < 0.05) than steers fed other treatments. Steers fed the corn diet, CFWC-CRP, and WS-CRP had greater (P < 0.01) DM digestibility than NAT. The results confirm benefits for nutrient digestion and subsequent animal performance when crop residues are thermochemically processed. Processed crop residues may be fed in combination with DDGS to partially replace corn in ruminant diets.

Effect of source and amount of energy and rate of growth in the growing phase on performance and carcass characteristics of early- and normal-weaned steers.

One hundred eighty-four Angus x Simmental steers (initial BW 161.7 +/- 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.

Adaptations in body muscle and fat in transition dairy cattle fed differing amounts of protein and methionine hydroxy analog.

The objectives were to determine effects of prepartum protein intake and dietary amino acid balance on production, adaptations in body fat and protein, amino acid concentrations, and, indirectly, body protein breakdown in early lactation. Multiparous Holstein cows (n = 42) were fed diets containing 11 or 14% crude protein with or without 20 g/d of methionine hydroxy analog for 21 d prepartum and then fed a common diet of 17% crude protein for 120 d postpartum, with or without 50 g/d of methionine hydroxy analog. Dry matter intake postpartum averaged 25.4 kg and milk production 41.6 kg. Cows fed the 14% CP diet ate 0.7 kg more dry matter and gave 1.7 kg more milk than those fed the 11% diet postpartum, but this difference was not significant. Cows fed methionine hydroxy analog prepartum lost less body protein from -14 to 60 d in milk. From d 60 to 120, body fat increased 8.5 and 11.5 kg for low and high protein groups and body protein increased 0.5 and 1.0 kg. Serum concentrations of branched chain amino acids fell 17% in the first few weeks postpartum, lysine fell 15%, histidine fell 16%, methionine increased 20%, and cysteine increased 30%. The ratio of serum 3-methylhistidine to creatinine was determined to indicate muscle protein degradation. An increase in this ratio at 7 d postpartum indicated increased body protein breakdown, there was no effect of prepartum ration. Increased protein intake prepartum may allow more feed intake and milk production postpartum, and supplementing a methionine analog on a ration already balanced in methionine by contemporary models may spare body protein.

Rumen undegradable protein, rumen-protected choline and mRNA expression for enzymes in gluconeogenesis and ureagenesis in periparturient dairy cows.

The objective of this study was to profile mRNA expression of argininosuccinate synthetase (AS) and ornithine transcarbamylase (OTC), two enzymes that participate in the formation of urea in liver and compare these with changes in mRNA for pyruvate carboxylase (PC) and phosphoenolpyruvate carboxykinase (PEPCK) during the periparturient period in dairy cows. Forty-eight multiparous Holstein cows were fed isoenergetic prepartum diets that contained 10% RDP and either 4.0% RUP or 6.2% RUP and either 0, 6, or 12 g/d of rumen-protected choline (RPC) as CapShure (Balchem Corp., Slate Hill, NY). After calving cows received a common diet and continued RPC as per their prepartum assignments. Liver biopsies were obtained on d -28, -14, 1, 28, and 56 relative to calving, and the abundances of AS, OTC, PC, PEPCK, and 18S mRNA were determined by Northern blot analysis of total RNA. The abundance of OTC mRNA was lowest at calving and was decreased by RPC and 6.2% RUP feeding. Feeding 6.2% RUP did not alter AS, PC, or PEPCK mRNA. The expression of AS mRNA increased and PEPCK mRNA tended to increase from calving to 56 DIM. Pyruvate carboxylase mRNA increased more than twofold at calving. The data indicated adaptation to lactation for gluconeogenic enzymes that is not matched in direction and magnitude by changes in mRNA for urea cycle enzymes. Feeding additional protein, as RUP, failed to induce mRNA for key enzymes in gluconeogenesis or ureagenesis.

Changes in mRNA expression for gluconeogenic enzymes in liver of dairy cattle during the transition to lactation.

The objective of this study was to profile phosphoenolpyruvate carboxykinase (PEPCK) and pyruvate carboxylase (PC) mRNA expression in the liver of dairy cattle during the peripartum transition and determine changes in abundance of these mRNA in response to protein fed during the prepartum period. Thirty-eight multiparous Holstein cows were fed diets containing either 12% crude protein (CP) and 26% rumen undegradable protein (RUP), 16% CP and 26% RUP, 16% CP and 33% RUP, or 16% CP and 40% RUP on a dry-matter basis beginning 28 d before expected calving. After calving, all cows were fed a common diet through 56 d in milk (DIM). Northern analysis of RNA from liver biopsy samples obtained on days -28, -14, +1, +28, and +56 relative to calving indicated that PC and PEPCK mRNA expression were responsive to onset of lactation but not to prepartum protein or RUP concentration. Abundance of PEPCK mRNA was similar at -28, -14, and +1 DIM but was elevated by +28 and +56 DIM relative to precalving levels. Liver PC mRNA abundance was elevated on +1 DIM, remained elevated through 28 DIM, and declined to precalving levels by 56 DIM. The activity of PC enzyme was correlated (r2 = 0.89) with PC mRNA abundance. The data demonstrate increased abundance of PC mRNA during the early transition period followed by increased abundance of PEPCK mRNA during the postpartum period and suggest increased potential metabolism of lactate, pyruvate, and amino acids that contribute to the liver pyruvate pool.

Impact of dietary protein amount and rumen undegradability on intake, peripartum liver triglyceride, plasma metabolites, and milk production in transition dairy cattle.

Feeding strategies of transition dairy cows contribute to the risk factors associated with metabolic disorders that limit production in the ensuing lactation. To investigate the effects of prepartum dietary crude protein (CP) concentration and amount of rumen-undegradable protein (RUP) on postpartum health and production, 44 multiparous Holstein cows were blocked by expected calving date and assigned to one of four isoenergetic prepartum rations beginning 28 d prior to expected calving date. Prepartum rations were: 12% CP and 26% RUP, 16% CP and 26% RUP, 16% CP and 33% RUP, or 16% CP and 40% RUP on a dry matter basis. All cows were fed the same postpartum diet (18% CP, 40% RUP) from 1 to 56 d in milk (DIM). Prepartum dry matter intake (DMI) was not different among dietary treatments. Mean postpartum intakes (kg/d) were higher through 56 DIM (P<0.05) for cows fed the 12% CP:26% RUP diet prepartum compared with any of the 16% CP diets (21.8 vs. 19.8, 18.6 and 18.6; 12% CP:26% RUP vs. 16% CP:26% RUP, 16% CP:33% RUP and 16% CP:40% RUP). There was a DIM x prepartum diet interaction (P<0.05) with the greatest effect of the 12% CP:26% RUP diet evident during the first 35 DIM. Cows fed the 12% CP:26% diet during the transition period tended to produce more milk (kg/d) (P = 0.08) than did cows fed any of the 16% CP diets (40.8 versus 37.8, 38.7, and 37.4; 12% CP:26% RUP vs. 16% CP:26% RUP, 16% CP:33% RUP, and 16% CP:40% RUP). Additional protein (12 vs. 16% CP) in the prepartum diet tended to decrease milk protein (P = 0.10) and milk fat yield (P = 0.08) but did not alter percent milk fat, percent milk protein, or MUN. Liver triglyceride (TG) expressed as milligrams of TG per microgram of DNA or percentage of dry matter (DM) on d -28, -14, +1, +28, and +56 relative to calving were not significantly different among treatments. Maximal (P<0.05) infiltration of TG in liver was observed on +1 d when expressed as a percentage of DM and on +28 d when expressed as milligrams of TG per microgram of DNA. Plasma glucose, calcium, urea nitrogen, beta-hydroxybutyrate, and nonesterified fatty acids were not different (P<0.05) among treatments. The data indicate carryover effects of prepartum dietary protein on postpartum intake and milk production, pointing to beneficial effects of maintaining dietary protein for dairy cows in late gestation at 12% CP.

Impact of dietary rumen undegradable protein and rumen-protected choline on intake, peripartum liver triacylglyceride, plasma metabolites and milk production in transition dairy cows.

The objectives of the present study were to determine the effects of rumen undegradable protein (RUP) level of prepartum diets, the supplementation of a rumen-protected choline product, and their interactions on milk production, feed intake, body weight and condition, blood metabolites, and liver triacylglycerides in dairy cows. Rumen-protected choline (RPC) was fed with two levels of RUP to 48 multiparous Holstein cows in a 3 x 2 factorial arrangement of treatments. Beginning 28 d before expected calving, cows were fed 10% rumen degradable protein, either 0, 6, or 12 g/d of RPC as CapShure (Balchem Corp., Slate Hill, NY) and either 4.0 or 6.2% RUP. After calving and through 120 d of lactation, cows received a common diet and continued RPC as per their prepartum assignment. Prepartum dry matter intake (kg/d) was not affected by RPC or RUP. Postpartum intake decreased when 6.2% RUP was fed prepartum. Milk production to 56 d in milk was decreased when cows were fed 6.2% RUP prepartum. Milk protein (kg/d) decreased when additional RUP was fed prepartum. Cows fed RPC lost more weight during the study period and tended to lose more body condition. Plasma urea nitrogen levels in the prepartum period were reduced for cows fed 4.0% RUP prepartum. Mean liver triacylglyceride determined from samples obtained at -28, -14, +1, +28, and +56 d in milk was not affected by RPC, prepartum RUP, or their combinations. Feeding 12 g of RPC/d in conjunction with 4.0% RUP increased milk production, but feeding RPC with 6.2% RUP prepartum and through 56 d in milk decreased production. The data indicate that 6.2% RUP does not benefit close-up dry cows, and the response to RPC depends the RUP content of the prepartum diet.

Effects of dietary supplementation on nutrient digestion and the milk yield of intensively grazed lactating dairy cows.

Fourteen midlactation Holstein cows were used in an 80-d study to examine supplementation strategies during intensive rotational grazing. Factors examined were the concentration of protein in the supplement [12 or 16% crude protein (CP) on a dry matter basis] and the amount of supplement offered (6.4 or 9.6 kg/d per cow). The supplement was offered in equal portions three times daily after milking. Pasture, composed of alfalfa (Medicago sativa) and orchardgrass (Dactylis glomerata), was divided into 27 0.16-ha paddocks that were grazed for 12 to 24 h. Intake of forage tended to increase as CP in the supplement increased but was unaffected by the amount of supplement offered. Intakes of organic matter and dry matter and the digestion of these nutrients in the total tract increased as CP in the supplement increased and as the amount of supplement increased. Ruminal pH and concentrations of volatile fatty acids were unaffected by treatments, but concentrations of NH3 N increased as CP in the supplement increased. An increase in CP resulted in a greater intake and flow of total N to the duodenum. The flow of microbial N to the duodenum and the efficiency of microbial protein synthesis were unaffected by treatment. Flows of total amino acids and essential amino acids to the duodenum tended to increase as CP in the supplement increased. Yield of fat-corrected milk and concentrations of fat and protein in milk were unaffected by treatment. These results suggested that the supply and digestion of nutrients in grazing dairy cows may be improved through an increase in the CP concentration of the supplement or the amount of supplement offered. However, effects on the yield of milk and milk components may be small.

Influence of source and amount of dietary protein on milk yield by cows in early lactation.

The purpose of this research was to examine the effects of various amounts of CP and RUP on AA flow to the small intestine and milk yield of lactating dairy cows. The first trial was a 5 x 5 Latin square design using five ruminally and duodenally cannulated multiparous cows. Diets contained chopped alfalfa hay, corn silage, high moisture corn, solvent-extracted soybean meal, and specially processed soybean meal (60.2% RUP). Soybean meal replaced high moisture corn to increase dietary CP from 14.5 to 16.5 or 18.5%, and specially processed soybean meal replaced solvent-extracted soybean meal in diets containing 16.5 or 18.5% CP to provide 6.2, 7.3, 6.7, and 8.3% RUP. Increasing dietary CP increased the flows of all AA to the duodenum. Increasing dietary RUP increased flows of Arg, His, Lys, Phe, Asp, and Glu to the duodenum. In a second trial, 36 cows were fed diets similar to those used in trial 1. Increased amounts of RUP in diets tended to increase milk yield because of improved protein status, improved intake of metabolizable energy, or both.

The value of soybean hulls as a replacement for corn in beef cattle diets formulated with or without added fat.

One hundred twenty crossbred yearling steers (average weight = 445 +/- 32 kg) were used in an 84-d randomized complete block design experiment to determine the value of soybean hulls (SH) as a replacement for corn in concentrate diets formulated with or without added fat (lard). The steers were blocked by weight and alloted to one of eight treatments in a 4 x 2 factorial arrangement of treatments. The main factors were amount of SH (0, 20, 40, or 60% of diet DM) and amount of added fat (0 or 5% of diet DM). The basal diet without added fat or SH contained cracked corn (80%), a urea-based protein supplement (15%), and ground corn cobs (5%). Replacing corn with SH linearly (P = .03) decreased ADG, increased DMI (linear, P = .003; quadratic, P = .06), and linearly (P < .001) decreased gain efficiency. Fat addition tended (P = .08) to improve efficiency; ADG and DMI were unaffected (P > .05) by fat addition. Similar diets were fed to 16 wethers (average weight = 47 +/- 2.3 kg) in a randomized complete block design experiment to determine digestibility of NDF and dietary concentration of DE. Replacing corn with SH linearly increased DMI (P = .001) and NDF (P < .001) and linearly decreased (P < .001) the digestibility of DM. The digestibility of NDF tended to increase with increased SH. The digestibility of energy linearly (P = .0001) decreased with increased SH. The amount of fat had no effect (P > .05) on DMI or intake of NDF or digestibilities of these nutrients. The addition of fat tended (P = .07) to improve the intake of DE.(ABSTRACT TRUNCATED AT 250 WORDS)

Supplemental protein sources for steers fed corn-based diets: II. Growth and estimated metabolizable amino acid supply.

Seventy Simmental-cross steers (average initial weight 301 +/- 24 kg) were individually fed in a 175-d completely randomized design experiment to evaluate the effects of source and level of protein in the diet on gain and feed efficiency. Steers were allotted to 1 of 10 treatments (seven steers per treatment) in a 3 x 3 factorial arrangement of treatments plus a urea-supplemented control diet. Main factors were source of supplemental protein (soybean meal [SBM], a high ruminal escape soybean meal [SP; SoyPLUS], or a combination of corn gluten meal and blood meal [CB; 50:50 on a nitrogen basis]) and level of each protein source (20, 30, or 40% of total dietary CP). Based on 18-h in situ ruminal incubation, escape N content of the protein sources was 66.0, 82.5, and 90.8% of total N and metabolizable amino acid (MAA) content was 29.1, 33.4, and 67.8 g/100 g of DM for SBM, SP, and CB respectively. The steers were fed 12.5% CP diets based on cracked corn (70%) on d 0 through 70 and were switched to a common 11.5% CP urea-supplemented cracked corn diet (80%) on d 71. The steers were housed in individual confinement stalls and had ad libitum access to feed. Replacing urea with SBM or SP increased (P < .05) 28- and 70-d ADG and DMI and increased (P < .05) 28-d efficiency (kg of gain/100 kg of feed). Replacing urea with CB did not improve (P > .05) 28- or 70-d ADG or DMI but did increase (P < .05) 28-d efficiency. The growth rate of steers at 28 and 70 d was correlated to a greater degree with ME intake (r2 = .83 and .85, respectively) rather than MAA supply, suggesting that the MAA supply was not first-limiting for growth. The source of supplemental protein fed during d 0 through 70 had no effect (P > .05) on 175-d DMI or efficiency; however, feeding SBM increased (P < .05) 175-d ADG compared with feeding urea, SP, or CB. Increasing supplemental true protein tended to linearly increase ADG and DMI at 28 and 70 d, but overall, ADG, DMI, and efficiency were not affected (P > .05) by treatment. Replacing urea with SBM or CB in the first 70 d decreased (P < .05) carcass quality grade, dressing percentage, and longissimus muscle area.(ABSTRACT TRUNCATED AT 400 WORDS)