2007
In vitro examination of rumen biohydrogenation (BH) of four dietary fats
M. Carriquiry1, W.J. Weber1, L.H. Baumgard2, and B.A. Crooker1
Rumen microbial BH of unsaturated fatty acids in dietary fats (Alifet High-Energy® (AHE), Alifet-Repro® (AR), Megalac® (MG), and Energy Booster® (EB)) that differ in fatty acid content, method of protection from rumen BH, or both factors was assessed. Fats (20 mg) were incubated at 37°C with strained rumen fluid diluted 5-fold with 16 mL of medium, 0.8 mL of reducing solution buffer and 200 mg of a purified, synthetic diet. Total contents were collected after 0, 6, 24, and 36 h and change in fatty acid content used to estimate rate of BH. For oleic acid, loss after 36 h (about 60%) and rate of BH (4.0 ± 1.3 vs. 6.1 ± 1.9 %/h) did not differ between EB and AHE. For MG, rate of BH was 4-times greater for linoleic than for oleic (4.0 ± 1.3 vs. 0.9 ± 0.2 %/h) acid. Only 20% of the oleic acid but 65% of the linoleic acid disappeared from MG after 36 h. In contrast, BH of oleic, linoleic and linolenic from AR were similar (2.6 ± 1.1, 2.5 ± 1.1, and 2.4 ± 0.9 %/h, respectively) and 95, 65, and 65% of these fatty acids remained after 36 h. Only AHE and AR contained trans-18:1 but total trans-18:1 increased with time of incubation for all dietary fats. Trans-10 and trans-11 were the predominant trans-isomers in AHE and AR incubations whereas trans-9 and trans-10 were the predominant isomers in EB and MG incubations. None of the fats contained conjugated linoleic acid (CLA) but CLA was in the inoculum. Although not affected by fat source, the amount of CLA decreased with incubation time. Only AR contained eicosapentaenoic (EPA, 20:5) and docosahexaenoic (DHA, 22:6) and loss of EPA and DHA was minimal (10 and 5%, respectively). The expected increase in BH of fatty acids with degree of saturation occurred with MG but neither degree of saturation nor chain length affected BH of fatty acids in AR. Results suggest that fatty acids in AR are protected from rumen metabolism and that AR can deliver significant amounts of EPA and DHA to the ruminant intestine.
1Department of Animal Science, University of Minnesota, St. Paul
2Department of Animal Science, University of Arizona, Tucson
Hepatic gene expression in Holstein cows treated with bovine somatotropin (bST) and fed omega-3 fatty acids in early lactation
M. Carriquiry, W.J. Weber, S.C. Fahrenkrug, and B.A. Crooker
Department Animal Science, University of Minnesota, St. Paul
Multiparous cows were blocked by expected calving date and previous milk yield and assigned randomly to treatments to determine effects of bST and dietary fat on hepatic gene expression. Dietary fat was provided from calving and included whole, high-oil sunflower seeds (SS; 10% of dietary dry matter (DM); omega-6:omega-3 ratio of 4.7) as a source of linoleic acid or a mixture of Alifet-High Energy® and Alifet-Repro® (AF; 3.4 and 1.5% of dietary DM, respectively; omega-6:omega-3 ratio of 2.6) as a source of protected omega-3 fatty acids. Cows received 0 or 500 mg bST (POSILAC®) every 10 d from 12 to 70 d in milk (DIM) and at 14-d intervals thereafter. Treatments from the 2 x 2 factorial combination of diet (SS or AF) with or without bST administration were designated as SSY, SSN, AFY, and AFN, respectively. Biopsies were collected (-12, 10, 24, and 140 DIM) when cows (n = 32, 8 blocks) were in positive and negative energy balance (EB). The amount of mRNA for growth hormone receptor (GHR), insulin-like growth factor-I (IGF-I), IGF-binding protein-3 (IGFBP3), peroxisome proliferator-activated receptors α (PPARα) and hepatic nuclear factor 4α (HNF4α) and an endogenous control (hypoxanthine phosphoribosyltransferase (HPRT)) were measured by quantitative realtime RT-PCR. Relative amounts of mRNA for GHR, IGF-I, and IGFBP3 were reduced after calving and increased thereafter. Abundance of PPARα mRNA increased as lactation progressed. Administration of bST increased hepatic expression of GHR, IGF-I, and IGFBP3 mRNA by 10 d (24 DIM) of treatment and the effect was still present at 140 DIM. There was interaction of bST with diet on PPARα mRNA abundance as the amount of PPARα mRNA increased in AFN cows and decreased in AFY cows. The amount of hepatic HNF4α mRNA was not affected by stage of lactation, bST, or diet. Initiation of bST at 12 DIM increased hepatic mRNA abundance for components of the somatotropic axis even when cows were in negative EB.
Post weaning performance of Holstein dairy heifers fed diets differing in forage quality and supplemented with a low moisture block
H. Chester-Jones1, D. Ziegler1, R. Larson2, B. Ziegler2, J. Linn3, M. Raeth-Knight3, and G. Golombeski3
Ninety-six dairy heifers were used in a 112-d study to evaluate feed intake and performance from 9 to 25 weeks of-age. Heifers (92.3 ± 0.93 kg BW) were randomly assigned to 1 of 4 grower diets (6 heifers/pen, 4 pens/treatment). All treatments were fed a cracked corn and pellet grain mix (16% CP) which was limit fed to 2.72 kg/calf per d (as fed) d 1 to 14 and to 1.82 kg/calf per d from d 15 to 112. Hay was fed free choice (FC) from d 1 to 112.Treatments were: 1) LOW: alfalfa hay (19.3% CP; 100 RFV); 2) LOWB: alfalfa hay (19.3% CP; 100 RFV) and low moisture molasses-based block (30% CP); 3) MED: alfalfa hay (19.6 % CP; 130 RFV); and 4) HIGH: alfalfa hay (18.6 % CP; 154 RFV). Using the low moisture block increased ADG by 4.0% and feed efficiency (FE) by 2.3% for the LOWB as compared to the LOW treatment. Feeding a higher quality hay increased ADG by 9.0% and FE by 3.0% for the MED compared to the LOW and LOWB treatments. Heifers receiving the highest quality hay (HIGH) had increased ADG (1.4%) and FE (5.9%) compared to heifers fed the MED treatment. Final BW for heifers fed LOW (188.9 kg) and LOWB (193.1 kg) were lower (P < 0.05) than heifers fed MED (198.9 kg) and HIGH (202.0 kg), respectively. Over the 112 d study, ADG (kg/d), grain DMI (kg), hay DMI (kg/d) and FE (kg feed/kg gain) were 0.87, 1.70, 2.41, 4.78; 0.91, 1.70, 2.36, 4.62; 0.96, 1.70, 2.68, 4.59; 0.97, 1.70, 2.49 and 4.33 kg for heifers fed LOW, LOWB, MED, and HIGH treatments, respectively. Under the conditions of the study, performance of all heifers was acceptable and an economic comparison should be the criteria to select the hay of choice when limit feeding grain mixes. The study demonstrated that feeding up to 2.72 kg daily of a 16% CP grain mix for the first 14 d followed by 1.82 kg/d from d 15 to 112 with access to FC alfalfa hay provides sufficient energy and protein for acceptable heifer growth.
1Southern Research and Outreach Center, University of Minnesota, Waseca
2Hubbard Feeds, Mankato, MN
3Department of Animal Science, University of Minnesota, St. Paul
Evaluation of an intraruminal pH probe
B.A. Crooker1, W.J. Weber1, S.C. Denham2, and J.L. Vicini2
Studies were conducted to compare rumen pH measurements from an intraruminal pH probe (IRP) to those obtained from a standard pH meter (M). Functional life and ability of IRP to detect changes caused by alterations in diet and feeding management were evaluated. The IRP (Well Cow, LTD, Bedford, UK) were calibrated prior to insertion and the M (Thermo Electron Corp., Beverly, MA) was calibrated before each use. Frequency (1 or 10 min) of measurement and data download from IRP were controlled through software on an external computer. The IRP (n = 2 or 3) were placed in the reticulum (R) or rumen of 3 lactating and 1 non-lactating cows for up to 28 d (Study 1). Measurements by M were obtained from R and ventral (V), caudal-ventral (CV) and caudal-dorsal (CD) sacs on d 0 to 5, 11, 23, and 27. Study 2 had three, 3-wk periods in which cows were fed a basal diet with sodium bicarbonate (B) 1X/d (continuous access to feed) and pH in R was compared with that of cows fed a) B with extra starch 1X/d, b) B as two discrete (3h) meals/d, or c) B without bicarbonate 1X/d. Each period had a 7 d transition (all cows fed B) and 14 d of treatment. The IRP (n = 2) were placed in R of 12 lactating cows blocked (n = 3) by DIM and milk yield. Results from IRP and M were compared using restricted maximum likelihood mixed model analysis. Means differed if P < 0.05. Mean pH by M differed by site (6.37, 6.28, 6.19, and 6.13 ± 0.04 in R, V, CV and CD, respectively) and time with no interaction (Study 1). When IRP functioned correctly, IRP and M values differed by less than 0.1 units but this was significant. Life of IRP was shorter (24.8 ± 1.5 and 28.6 ± 3.6 d for Study 1 and 2, respectively) and overall failure (50% by 28 d) greater than expected. Daily mean pH was not altered by treatment. Mean daily decline in pH after feeding was greater in cows not fed bicarbonate (-0.57 vs. -0.44 ± 0.01). The minimum pH per day was less for cows fed 1X/d than 2X/d (6.29 vs. 6.44 ± 0.07). The IRP have potential to provide accurate, prolonged measurements of pH but their functional life needs to be increased.
1University of Minnesota, St. Paul
2Monsanto Company, St. Louis, MO
Effects of feeding a polyclonal antibody preparation against selected rumen bacteria on rumen pH of lactating dairy cows
N. DiLorenzo1, C.R. Dahlen2, J.E. Larson1, R.K. Gill1, and A. DiCostanzo1
A series of experiments were conducted to evaluate the effects of feeding an avian-derived polyclonal antibody preparation against selected proteolytic, amylolytic and Gram – bacteria (RMT) on rumen pH of lactating dairy cows. Exp 1: 13 rumen cannulated dairy cows in late lactation were used in a cross-over design consisting of a 13-d adaptation period followed by 1 d of sample collection. Cows were fed a basal diet containing 1.72 Mcal NEl/kg DM, 17.5% CP, 0.65% Ca and 0.35% P. Cows received 10 mL RMT or a preparation made with generic eggs (Control) daily top-dressed at 0900. Rumen pH was measured at 0, 2, 6 and 8 h post feeding on d 14. Exp 2: A batch culture incubation was done using rumen fluid from early lactation donor dairy cows supplemented with RMT or Control (10 ml/d) for 13 d. Flasks (250 mL) were incubated at 39°C with 10% glucose added as substrate. Each flask received 0.5 mL of RMT or Control, and pH was measured over time. Exp 3: Four rumen cannulated dairy cows in early lactation were used in a cross-over design with two 3-d pH-monitoring periods. Cows received 250 mL of RMT or Control solution on d 0 through the rumen cannula. During days -1 to 1, rumen pH was recorded every 20 min by means of an indwelling pH electrode. Exp 1: No significant effects (P > 0.05) of RMT were observed in rumen pH of late lactation dairy cows. Exp 2: pH at 4.5 h (6.04 vs. 5.85) and 6 h (5.20 vs. 5.08) of incubation was greater (P < 0.05) in flasks infused with RMT. Exp 3: mean daily rumen pH (6.07 vs. 5.75) and mean daily maximum rumen pH (6.82 vs. 6.36) were greater (P < 0.05) for cows receiving RMT. Mean daily minimum rumen pH tended (P = 0.06) to be greater for cows receiving RMT (5.48 vs. 5.06). Feeding an avian-derived polyclonal antibody preparation against specific rumen microorganisms was effective at maintaining a greater rumen pH in early lactation dairy cows; this finding may have positive implications on health and performance of dairy cows.
1Department of Animal Science, University of Minnesota, St. Paul
2Northwest Research and Outreach Center, University of Minnesota, Crookston
Pre- and post weaning performance and health of dairy heifer calves fed milk replacers with different protein sources
S. Hayes1, B. Ziegler2, R. Larson2, H. Chester-Jones3, D. Ziegler3, J. Linn4, M. Raeth-Knight4, and G. Golombeski4
One-hundred-twenty-four 2 to 4 d-old dairy heifer calves were randomly assigned to 1 of 5 medicated (20% CP:20% fat) milk replacers (MR) with 4 MR partially replacing milk protein with plant-based sources to measure pre- and post weaning performance and health. Calves were housed in 2.29 x 1.17 m individual calf pens, within a frame-steel curtain side-wall, naturally ventilated barn. Initial BW averaged 40.9 kg ± 0.79 kg. Treatments were: 1) MR all-milk protein control (CON); 2) MR with hydrolyzed wheat gluten protein replacing 50% of the milk protein (50WG); 3) MR with soybean protein concentrate replacing 50% of the milk protein (50SPC); 4) MR with WG replacing 30% of the milk protein (30WG); and 5) MR with 25% WG and 25% SPC replacing milk protein (25SPCWG). Milk replacers were fed at 0.284 kg (as-fed) in 1.99 L water 2X daily for the first 35 d, and then 1X daily from d 36 to weaning at 42 d. Calves were offered a 20.2% CP calf starter (CS) and had access to fresh water. Total DMI from MR averaged 21.8 kg/calf. Calves fed CON had 4.09 kg greater (P < 0.05) pre-weaning gain compared to other groups. Overall ADG and feed/gain were 0.78, 1.80; 0.71, 1.85; .70, 1.98; 0.69, 1.88; 0.68 and 1.93 kg for calves fed CON, 50WG, 50SPC, 30WG and 25WGSPC, respectively. Health treatment costs/calf averaged $2.09. Under the conditions of this study, feeding an all-milk protein MR with CS resulted in excellent growth. The use of WG and SPC as a partial replacement for milk protein reduced calf performance due mainly to CS intake differences. Plant-based MR protein sources do have the potential to reduce feed costs to weaning.
1Milk Products, Chilton, WI
2Hubbard Feeds, Mankato, MN
3Southern Research and Outreach Center, University of Minnesota, Waseca
4Department of Animal Science, University of Minnesota, St. Paul
Evaluation of the fermentation dynamics of the soluble protein fraction of three protein sources in continuous culture fermenters
M. Ruiz Moreno1, A. Bach2,3, M. Thrune1, and M.D. Stern1
Six dual-flow continuous culture fermenters were used to assess differences in degradation pattern and ability to promote bacterial growth from the soluble CP fractions of canola meal (CM), soybean meal (SBM) and fish meal (FM) using a completely randomized design with two 9-d experimental periods. All fermenters received the same basal diet (58% ground corn, 40% canary grass hay, 0.4% vitamin-mineral premix, 1% CaCO3, 0.6% salt on a DM basis). During sampling on the last 3-d of each period, 90-mL doses containing soluble proteins were infused into fermenters 30 min after the beginning of the first and last feedings of the day at a rate of 3 mL/min, using a constant-infusion pump. These doses were prepared from samples of FM, SBM and CM that were ground and soaked in distilled water (1:4 wt/vol, 38C, 1h) under continuous stirring. The solutions were centrifuged and the supernatant vacuum-filtered through a N-free filter paper. Equal N concentrations were achieved by diluting filtrates with the higher N content to match the one with the lowest N content using distilled water. Normalized filtrates (1.8% CP as is) were frozen in 90-mL doses and were gently thawed prior to infusions into the fermenters. The total amount of soluble CP supplied by the infusions of FM, CM and SBM was 3.2 g/d, representing 27% of daily dietary CP intake. Each sampling day, at 0, 0.5, 1, 3, and 6 h following the morning infusion of soluble CP fractions, a 10-mL aliquot from each fermenter flask was collected to determine NH3-N concentrations. Infusion of FM resulted in the greatest NH3-N concentrations (4.5±0.08 mg/dL) compared with the other treatments (0.42±0.08 mg/dL). Bacterial N flow (g/d) was also greatest (P < 0.05) with FM (1.47±0.07) compared with the other soluble CP fractions (1.09±0.07). Results indicate that microbial degradation of the soluble CP fraction of FM is much higher than the soluble CP fractions of CM or SBM.
1Department of Animal science, University of Minnesota, St. Paul
2ICREA, Barcelona, Spain
3IRTA-Unitat de Remugants, Barcelona, Spain
2006
Performance of dairy heifer calves fed milk replacers with equal protein and fat levels but utilizing different fat sources
B. Braman1, S. Hayes1, H. Chester-Jones2, D. Ziegler2, J. Linn3, and B. Ziegler4
One-hundred-eleven 2 day old dairy heifer calves were randomly assigned to one of 3 all-milk protein milk replacer (MR) treatments to evaluate the effect of fat source on pre- and post-weaning calf performance. Calves were housed in 2.29 x 1.17 m individual calf pens within a frame-steel curtain side-wall naturally ventilated calf barn. Average BW across treatments at day 2 of-age was 41.8 kg ± 0.54 kg. All MR contained 24% protein: 20% fat and only differed by fat source. Fat treatments were: 1) Animal fat (AF); 2) Vegetable blend of 80% palm oil and 20% coconut oil (VF); and, 3) AF plus a blend of medium chain tri-glycerides containing 1% caproic, 69% caprylic, 1% capric and 29% lauric acids fed at 5 g/calf daily (AFA). Milk replacers were fed at 0.28 kg (as-fed) in 1.99 L water 2X daily for the first 35 days, and then 1X daily from day 36 to weaning at 42 d. Calves were offered an 20.9% CP (DM basis) texturized calf starter throughout the study. Fresh water was available daily at all times. Total DMI from MR for 42 d averaged 20.9 kg/calf. Feed DMI to 42 d tended to be higher for calves fed AF (26.38 kg) vs. those fed AFA (23.95 kg; P<0.08) with the VF calves being similar to other groups (24.19 kg). Daily gains to 42-d were similar (P>0.05) averaging 0.65, 0.62 and 0.62 kg for calves fed AF, VF, and AFA calves, respectively. There were no differences (P>0.05) in post weaning gain and gain/feed from d 42 to 56, which averaged 0.95, 0.45; 0.95, 0.47; 0.96 and 0.47 kg for calves in the AF, VF and AFA groups respectively. Overall 56-d daily gain and gain/feed were not affected by treatments (P>0.05) averaging 0.73, 0.53; 0.70, 0.54; 0.70 and 0.54 kg for calves fed AF, VF, and AFA, respectively. Fecal scores taken daily throughout the study were not affected by treatment (P>0.05). Under the conditions of this study feeding a common milk replacer with varying fat sources did not affect pre- and immediate post weaning calf performance.
1Milk Products, Chilton, WI
2Southern Research and Outreach Center, University of Minnesota, Waseca
3University of Minnesota, St. Paul
4Hubbard Feeds, Mankato, MN
Performance of Holstein dairy heifers fed concentrate diets containing dried distillers grains or urea
R. Larson1, B. Ziegler1, J. Linn2, D. Ziegler3, and H. Chester-Jones3
Ninety Holstein dairy heifers (av. BW 100.9 ± 1.30 kg) were used in an 84-d study to evaluate feed intake and performance from 13 to 24 weeks of-age. Post weaned heifers were randomly assigned to 5 replicate pens (6 heifers/pen) each of 3 grower diets containing an 18% CP (DM basis) concentrate mix limit-fed up to 2.27 kg/heifer daily with free-choice hay. Concentrate mixes were: 1), Cracked-corn and soybean meal-based pellet (C); 2), Cracked corn and dried distillers grain (DG; 1.45 kg DG/heifer; CDG) and 3), Cracked-corn and urea-based pellet (22.7 g urea/heifer; CUP). During the first 28 d of the study, heifers fed CDG tended to have (P<0.10) faster daily gains (0.93 kg) than those fed CUP (0.85 kg) but similar (P>0.10) to those fed C (0.87 kg). Gain/feed for the same period was similar across heifer groups (P>0.2) averaging 0.27 kg. There were no heifer performance differences (P>0.2) from d 29 to 56 or 57 to 84 d. Final BW and body condition score were 181.05 kg, 3.68; 184.65 kg, 3.68; 180.18 kg and 3.72 for heifers fed C, CDG, and CUP diets, respectively. Overall heifer performance for the 84 d study was not affected by concentrate mix fed (P>0.3). Average daily hay intake was 2.42 kg/heifer over 84 d with a range from 1.41 kg/heifer during d 1 to 28 up to 3.46 kg/heifer from 57 to 84 d. Total gain, total DMI and gain/feed for 84 d were, 79.68, 355.45, 0.23; 83.15, 346.85, 0.24; 80.27, 346.39, and 0.23 kg/heifer for those fed C, CDG, and CUP diets, respectively. The study found that limit feeding a concentrate mix to 2.27 kg/ day with free choice hay for post weaned dairy heifers from 13 to 24 weeks of age supported good growth rates. Using DG or urea as alternative protein sources in concentrate mixes were acceptable options.
1Hubbard Feeds, Mankato, MN
2University of Minnesota, St. Paul
3Southern Research & Outreach Center, Waseca
The effects of manganese levels in water on the performance of dairy calves from birth to 70 days of age
K.M. Steffenhagen, M.L. Raeth-Knight, and J.G. Linn
University of Minnesota, St. Paul
Thirty-three Holstein or Holstein-Montebeliarde crossbred calves, born from November 2003 to April 2004, were blocked by sex and randomly assigned to 1 of 3 treatments for 70 days. Treatments were control water (0.003 ppm Mn), 0.25 ppm Mn in water and 0.75 ppm Mn in water. The control water was supplemented with manganese carbonate to achieve 0.25 and 0.75 ppm Mn levels. Colostrum was fed twice daily the first two days following birth, for a minimum of 4 feedings. Milk replacer, containing 20% crude protein and 20% fat, was mixed with treatment water to contain 11% solids and fed twice daily until weaning at 42 days of age. Starter (18% CP) and treatment water were offered ad libitum day 7 to day 70. Feed and water intake were recorded daily. Body weight (BW) and hip height (HH) were recorded at birth, day 28, 42 and 70. Calves were housed individually in calf hutches from day 3 to day 70. Growth and intake data were analyzed as repeated measures using PROC MIXED and birth weight within sex was included in the statistical model as a covariate. There was no significant effect (P>.1) of calf sex on performance therefore, only treatment means are presented. Manganese level of water mixed with milk replacer or offered ad libitum had no significant effect on milk replacer or starter intake or growth of calves. Free water intake averaged 2.65, 2.71, and 2.68 L/day pre-weaning (day 3-42) and 10.80, 11.83 and 11.46 L/day post-weaning (day 43-70) for control, 0.25, and 0.75 treatments, respectively. For all calves, total dry matter intake averaged 1.75 kg/day pre-weaning and 3.55 kg/day post weaning. Calf body weight for control, 0.25 and 0.75 treatments averaged 50.1, 46.8 and 50.0 kg at birth and 104.3, 99.8, and 104.4 kg at the end of trial. Manganese carbonate in water up to 0.75 ppm Mn did not significantly impact calf performance or health.
Effects of various methods used to process soybean meal on protein digestion in the rumen and small intestine
M.D. Stern1, M. Ruiz Moreno1, and C.A. Macgregor2
A three-step procedure was used to evaluate the effects of soybean meal processing on ruminal crude protein (CP) degradation and intestinal CP digestion. Residue from 16 h in situ ruminal incubation simulated ruminal undegradable protein (RUP), and was incubated for 1 h in a 1 N HCl solution with 1g/L of pepsin, simulating abomasal CP digestion. After incubation, pH was neutralized and a pH 7.8 phosphate buffer with 3 g/L of pancreatin added, then incubated for 24 h at 38 °C, simulating intestinal digestion. This procedure was used to evaluate seven soybean meal (SBM) products including solvent-extracted SBM (SE), mechanical-extracted (ME) SBM #1 with fresh soy gums (ME1G), ME SBM #2 (ME2), ME SBM #3 (ME3), ME SBM extruded (MEE), SE heat treated (SEH), SE nonenzymatically browned (SENB). Ruminal undegradable CP (RUP) was 23.2, 49.3, 42.1, 33.4, 38.3, 52.3 and 68.3% for SE, ME1G, ME2, ME3, MEE, SEH and SENB, respectively. Intestinal CP digestion (ID) was 67.5, 83.8, 78.9, 75.7, 76.5, 65.4 and 57.7% for SE, ME1G, ME2, ME3, MEE, SEH and SENB, respectively, indicating that processing can overprotect protein from digestion in the small intestine. Intestinally absorbable dietary protein (IADP), calculated as RUP x ID was 15.7, 41.3, 33.2, 25.2, 29.3, 34.2 and 39.4% for SE, ME1G, ME2, ME3, MEE, SEH and SENB, respectively. The range of IADP was 15.5% for SE to 41.3% for ME1G, however it is interesting to note that SENB was next highest at 39.4% because of a high RUP value that compensated for lower intestinal digestion. These results demonstrate that it is important to account for RUP and intestinal CP digestion when selecting a SBM source to include in the ruminant diet.
1University of Minnesota, St. Paul
2Grain States Soya, Inc., West Point, NE
Evaluating in vitro neutral detergent fiber digestibility of high-fiber byproduct feeds and forages
J. Wakker, H.G. Jung, and J.G. Linn
University of Minnesota, St. Paul
In vitro neutral detergent fiber digestibility (IVNDFD) is being used to evaluate feeds for quality and purchase. The objective of this study was to evaluate the repeatability of IVNDFD analysis over time using 12 forages and 10 high-fiber byproduct feeds. During a 6-wk experimental period, ruminal contents were collected on a bi-weekly basis from a single lactating Holstein cow. Ankom filter bags containing 0.5 g of each feedstuff were incubated, in duplicate, for 48 h at 39°C using the Daisy Oven system. Data were analyzed using PROC GLM of SAS. Week of rumen fluid collection significantly (P<0.05) affected IVNDFD across feeds with collection 2 having lower IVNDFD values than collections 1 and 3. Ranking by IVNDFD of forages, but not byproduct feeds, was affected (P<0.05) by collection. Average IVNDFD for whole cottonseed and wheat middlings were 32 and 54%, respectively, while the other 8 byproduct feeds ranged from 84 to 91% IVNDFD. For a conventional corn silage sample, collections 1 and 3 were higher (P<0.05) in IVNDFD than collection 2 (67 & 66 vs. 45%). A brown midrib (BMR) corn silage’s IVNDFD was higher (P<0.05) for collection 3 compared to collections 1 and 2 (73 vs. 60 & 59%). Comparing the conventional and BMR corn silages, IVNDFD was different for collection 2 (45 vs. 59%), but not different for collections 1 (67 & 60%) and 3 (66 & 73%). Three alfalfa samples (1 haylage and 2 hays) did not differ for their IVNDFD values across collections, but ranking by IVNDFD within rumen collections revealed differences. Haylage was higher (P<0.05) in IVNDFD than hays 1 and 2 for collection 1 (62 vs. 53 & 52%), similar to hays 1 and 2 for collection 2 (54 vs. 51 & 50%) and higher (P<0.05) than hay 2 for collection 3 (58 vs. 50 vs. 47%). Four grass hay samples differed in ranking by IVNDFD within rumen collections. For collection 1, ryegrass and oat hay were no different, but both hays were higher (P<0.05) than mixed-grass hay and barley hay (74 & 69 vs. 57 & 54%). Ryegrass was higher (P<0.05) than oat hay, mixed-grass hay, and barley hay for collections 2 (75 vs. 60, 55, & 50%) and 3 (74 vs. 61, 56, & 49%). Repetitive rumen fluid collections under standardized conditions resulted in different IVNDFD results for individual feeds. Ranking of forages, but not byproduct feeds, varied among rumen fluid collections. |
