Penn State Particle Separator Research Articles

227 Evaluation of mixer performance in cattle finishing diets of varying physical characteristics

Abstract An experiment was conducted to evaluate batch fraction (BF), physical characteristics (DIET), and mixing duration (DUR) on long particle distribution in finishing diets. Diets were mixed in a 2.35 m3 horizontal mixer. The experiment was designed as a 5×3×2 factorial arrangement with nine replications per simple mean. Factors included 1) BF (n = 5), 2) DIET (n = 3) containing no corn-milling by-product (CON), a dry-corn milling by-product [47.45 ± 1.015% DM (as-is basis); DRY], or a wet-corn milling by-product [43.67 ± 1.786% DM (as-is basis); WET], and 3) mixing duration (n = 2) of 20 or 25 revolutions. Diets contained a 1:1 blend of DRC:HMC, the corn-milling by-products replaced the corn blend (20% total diet DM inclusion), grass hay (6% DM inclusion), liquid supplement (5% DM inclusion), and a meal supplement (7% DM inclusion). Data were analyzed as a CRD using the GLIMMIX procedure (SAS Inst., Inc., Cary, NC) using a multinomial approach. Samples of the total mixed ration (TMR) were subjected to separation via the Penn State Particle Separator. The dependent variable of interest was the portion of the TMR retained on the 19 mm sieve. No interactions were detected (P ≥ 0.49). There was an 87.1% (P = 0.01) increase in retention on the 19 mm sieve for last BF compared to the first BF. Diet influenced (P = 0.04) 19 mm sieve retention, there was 10.2% less TMR retained on the 19 mm sieve for DRY versus WET; CON was intermediate. Mixing duration did not influence (P = 0.73) 19 mm sieve retention. These data indicate that as the mixer unloads there can be nearly double the amount of roughage fed; differing physical characteristics of the diet only moderately influence the true roughage content fed. Differing roughage content delivered depending upon the BF could influence daily intake, feed efficiency and alter observed to expected ratios of dietary net energy.

Effects of feeding frequency and oil supplementation on feeding behavior, ruminal fermentation, digestibility, blood metabolites, and milk performance in late-lactation cows fed a high-forage diet

Many dairy producers are keen to feed low-producing late-lactation cows only once per day (1×) to reduce production costs. This study examined effects of feeding frequency (FF: thrice versus once daily) on behavioral patterns, ruminal fermentation, and milk production performance of cows and supplementation of yellow grease oil (YO) rich in 18:2n-6 as a potential strategy to alleviate the possible negative effects of 1× daily feeding. Twenty-four late-lactation Holstein cows (215 ± 53.8 DIM) housed in tiestalls were assigned to 4 treatments according to a 2 × 2 factorial arrangement with 2 FF [3 times daily (3×) at 0800, 1400, and 2000 h; or 1× at 0800 h] and 2 high-forage total mixed rations (TMR), without (CON) or with 25 g/kg of dry matter of YO (YGO), in a randomized complete block design. Treatments were applied for 21 d. Feeding behavior was recorded every 5 min over a 24-h period on d 19. Fresh TMR and orts were sampled (d 15 to 21) and separated using a 3-screen (19, 8, and 1.18 mm) Penn State Particle Separator for sorting activity. Ruminal fluid samples were collected using oral stomach tubing on d 21. Cows on 1×-CON spent more time eating during the first 6 h after feeding at 0800 h than did cows on 3×-CON or 1×-YGO. Decreasing FF increased meal length and tended to increase meal size for CON cows, but supplementing YO increased meal bouts and reduced meal length and size for cows fed 1×. Cows on 1×-CON had the greatest ruminating time between 2000 and 0800 h compared with other treatments. Total and daytime distribution of lying time did not vary by treatments. Sorting activity was higher for cows fed frequently, and the extent of sorting was increased by oil supplementation. In the morning ruminal fluid samples, pH was not different among treatments, but in the evening samples 1× daily feeding reduced ruminal pH compared with 3×. In the morning and evening samples, ratios of acetate to propionate were the lowest for 1×-CON cows compared with other treatments. Dry matter intake and milk yield were similar among the groups. Milk fat content and yield decreased with 1×-CON treatment, but supplementing YO numerically increased milk fat for cows fed 1×. These results suggest that decreasing FF from 3× to 1× daily increases meal length, particularly after feed delivery, in cows fed high-forage diets; but supplementation of plant oil changes feeding patterns and may improve ruminal pH and milk fat in cows fed once a day.

Accuracy and homogeneity of total mixed rations processed through trailer mixer or self-propelled mixer, and effects on the yields of high-yielding dairy cows

Total mixed ration (TMR) quality depends on feed levels and values, and appropriate diet formulation, but also on diet preparation practice. We examined the accuracy and homogeneity of rations, as affected by the machinery used for TMR preparation, and their effects on dairy cow performance. Multiparous Israeli-Holstein cows (n = 216) were stratified into 2 groups, according to milk yields, days in milk, parity, and body weight; they were fed the same formulated TMR, prepared by either a trailer mixer (TM) or an self-propelled loading mixer (SPLM). To examine the accuracy of diet preparation we have recorded and analyzed 10 times the difference between the programmed and the actual loaded content (as fed matter) of each feed ingredient. For evaluation of the accuracy and homogeneity of the ration contents, the TMRs from 6 spots along the feeding trough were sampled at 10 time-points, and the samples were analyzed for DM, protein, ADF, aNDF and ash contents; the results were compared with the programmed values. On another 7 occasions, samples of the TMRs were taken from 3spots along the feeding trough for evaluation of the particle sizes distribution using the Penn State Particle Separator. The mean difference – in percentage units – between the programmed and actual, loaded concentrate feeds was similar (∼5.7 %) for both TMRs (SEM = 1.5; P = 0.98), but for forage feeds it was +17.6 and - 0.6 % (SEM = 3.7; P = 0.001), for TM and SPLM TMR, respectively. The mean differences of contents (in percentage units; DM basis) between the programmed and prepared diets, were: for protein – 1.1 and 0.9 % (SEM = 0.2, P = 0.25), for ADF – 2.7 and 1.3 % (SEM = 0.2, P < 0.001), and for aNDF – 6.9 and 5.7 % (SEM = 0.2; P < 0.002), in TM and SPLM TMRs, respectively. Except for ash content, the chemical-composition homogeneity was greater in the SPLM TMR than in the TM TMR. The fraction of particles>19 mm was 2.9 percentage units greater (P = 0.04), and that of particles ≤8 mm was 3.3 percentage units less (P = 0.04) in the TM than in the SPLM ration. The milk yield was 1.2 kg/d greater (2.7 %) in cows fed the SPLM than in those fed the TM TMR (P < 0.001), and the milk-fat content was 0.8 g/kg greater in cows fed the TM TMR (P = 0.03). In conclusion, the accuracy and homogeneity of the SPLM-prepared TMR were greater than those of the TM-prepared TMR, which influenced the cows’ performance. This study demonstrates the importance of the preparation machinery for TMR quality, indicating that more attention should be dedicated in practice and research to the methods used for TMR preparation.

Evaluation of batch fraction, corn silage inclusion level, and mixing duration on long particle distribution of finishing diets for beef cattle.

Background: Differing fractions of a batch of feed, differing ingredient characteristics, and inadequate mix time can lead to non-uniformity within a mix of feed. Methods: The experiment was designed as a 5 x 2 x 2 factorial arrangement with seven replications per simple treatment mean. Factors included: 1) batch fraction (BF; n = 5); 2) corn silage inclusion level (CSLVL; n = 2) 15% or 30% inclusion (dry matter basis); and 3) mixing duration (DR; n = 2) of 20 or 25 mixer revolutions. Data were analyzed as a completely randomized design using a binomial approach. The Penn State Particle Separator was used to separate fractions of the total mixed ration (TMR). Results: No interactions between BF, CSLVL, and DR were detected ( P ≥ 0.31) for any dependent variables. There was an increase ( P = 0.01) in retention on the 19 mm sieve from the first BF compared to the last BF. CSLVL altered ( P = 0.01) retention on the 19 mm sieve. Increasing DR from 20 to 25 revolutions had no appreciable influence ( P = 0.23) on particles greater than 19 mm. CSLVL ( P = 0.01) and DR ( P = 0.01) altered particle retention on the 8 mm sieve. BF ( P = 0.01), CSLVL ( P = 0.01), and DR ( P = 0.02), influenced particle retention on the 4 mm sieve. CSLVL impacted ( P ≤ 0.01) particles remaining in the bottom pan and particles greater than 4 mm. BF ( P = 0.01) and CSLVL ( P = 0.01) altered particles greater than 8 mm. Conclusions: These data indicate that BF and CSLVL fed alters particle size distribution that in turn could alter dry matter intake, dietary net energy content, and influence daily gain. Mixing DR had no appreciable influence on particle size distribution of the TMR.

Consumption and ingestive behaviour of lambs fed varying levels of babassu mesocarp bran

Voluntary consumption (VolC) and ingestive behaviour (IB) of lambs fed diets containing different percentages (0.0; 7.5; 15.0 and 22.5%) of babassu mesocarp bran (I-BMB) were evaluated. The trial was at the Federal University of Tocantins, Campus de Araguaína-TO. Twenty lambs were evaluated using a completely randomized design, and five replications were performed. VolC data was obtained by measuring total volumes of both food supplied and food remaining after feeding. IB was evaluated throughout two, non-consecutive 24-h periods, with observations were recorded every five minutes that described the following behavioural variables: resting (REST), rumination (RUM), intake (INT) and chewing (CHEW). The particle size was also measured using a Penn State particle separator. All VolC parameters (dry matter intake, DMI; crude protein intake, CPI; neutral detergent fibre intake, NDFI; and acid detergent fibre intake, ADFI) increased linearly with I-BMB intake. I-BMB consumption did not interfere with water intake, nor did it affect I-BMB did not affect the duration of DMI, NDFI and ADFI. However, linear increases of rumination and chewing activities associated with DMI, NDFI and ADFI were observed as I-BMB levels increased. In summary, effects of inclusion I-BMB in diets of lambs included increased voluntary consumption, and reduced rumination and chewing, but not ingestion, efficiency. When economically favorable, these data suggest that inclusion of up to 22.5% I-BMB within balanced diets should be applied.

Feeding diets varying in forage proportion and particle length to lactating dairy cows: I. Effects on ruminal pH and fermentation, microbial protein synthesis, digestibility, and milk production

Physically effective neutral detergent fiber (peNDF) content of dairy cow diets was modified by varying the theoretical chop length of alfalfa silage and forage:concentrate (F:C) ratio, and effects on nutrient intakes, ruminal fermentation, site and extent of digestion, microbial protein synthesis, and milk production were evaluated. Estimates of dietary peNDF contents were compared with recommendations, and predictions of ruminal pH from peNDF and the recently developed physically adjusted neutral detergent fiber (paNDF) system were compared with observed pH. The experiment was designed as a triple 4 × 4 Latin square using 12 mid-lactating dairy cows with 4 intact, 4 ruminally cannulated, and 4 ruminally and duodenally cannulated cows. Site and extent of digestion and microbial protein synthesis were measured in a single 4 × 4 Latin square. Treatments were a 2 × 2 factorial arrangement; 2 forage particle lengths (FPL) of alfalfa silage (short and long) were combined with low (35:65) and high (60:40) F:C ratios [dry matter (DM) basis]. The peNDF contents were determined by multiplying the proportion (DM basis) of total mixed ration retained on 2 (8 and 19 mm; peNDF8.0) or 3 (1.18, 8, and 19 mm; peNDF1.18) sieves of the Penn State Particle Separator by the neutral detergent fiber content of the diet. The dietary peNDF contents ranged from 10.7 to 17.5% for peNDF8.0 or from 23.1 to 28.2% for peNDF1.18. Interactions between F:C ratio and FPL content were few. Increasing peNDF content of diets by increasing F:C ratio decreased DM intake, milk yield, and milk protein yield, whereas apparent total-tract DM digestibility and milk efficiency improved. Increasing F:C ratio improved ruminal pH status but decreased total volatile fatty acid concentration and microbial protein synthesis. Increasing peNDF content of diets via dietary FPL increased mean ruminal pH, but did not affect DM intake, total-tract digestibility, or milk production. The results indicate that feeding dairy cows a low F:C diet helps increase DM intake, milk production, and microbial protein synthesis, but may adversely affect feed digestibility and milk efficiency due to increased risk of subacute ruminal acidosis. Increased FPL improved ruminal pH status, but had minimal effects on feed intake, ruminal fermentation, nutrient digestibility, and milk production. The results indicate a trade-off between reducing the risk of subacute ruminal acidosis and maximizing ruminal fermentation, feed digestibility, and milk production of dairy cows. The paNDF model showed improvement in the predictability of ruminal pH over the peNDF model, but the accuracy of predictions varied depending upon the diet and ruminal fermentation variables considered in the equations.

Effects of feeding hay and calf starter as a mixture or as separate components to Holstein calves on intake, growth, and blood metabolite and hormone concentrations

This study investigated how providing hay mixed with calf starter to dairy calves affected their solid feed intake, feed sorting, growth, and plasma metabolite and hormone concentrations. Forty Holstein heifer calves were fed a texturized calf starter (23.4% crude protein, 32.3% starch on a dry matter basis) and chopped Klein grass hay as separate components (CONT) or the same starter and hay mixed at a 90:10 ratio on an as-fed basis (MIX) ad libitum from the date transported to the research farm (4-7 d of life) to 90 d of life. Calves were provided milk replacer (28% crude protein, 15% fat) at up to 557 g/d before the study, 737 g/d from d 14 to 20, 1,105 g/d from d 21 to 41, 737 g/d from d 42 to 48, and 557 g/d from d 49 to 55 on a dry matter basis. calves were fully weaned on d 56. Feed sorting for the MIX calves was evaluated using the Penn State Particle Separator; the sorting index was calculated as the actual intake as a percentage of predicted intake, with values >100% indicating sorting for and values <100% indicating sorting against. Treatment did not affect solid feed intake, growth performance, or plasma metabolite or hormone concentration during the preweaning or weaning periods. However, calves in the MIX treatment had less neutral detergent fiber intake as a percentage of solid feed intake than CONT calves in the preweaning (23.3 vs. 37.0%) and weaning (23.5 vs. 25.8%) periods, although MIX calves sorted (107.2%) for long particles, which were primarily hay, during weaning. During the postweaning period, MIX calves had greater neutral detergent fiber intake as a percentage of solid feed intake compared with CONT calves (23.4 vs. 22.7%), although they sorted against long particles (84.4%), and decreased solid feed dry matter intake compared with CONT calves (3,292 vs. 3,536 g/d) and average daily gain (1.20 vs. 1.31 kg/d). Weaned calves in the MIX treatment also had lower plasma concentration of glucagon-like peptide 2 compared with CONT (0.46 vs. 0.77 ng/mg) but had higher plasma concentrations of ghrelin (0.05 vs. 0.03 ng/mg). These results suggest that feeding a mixture of texturized calf starter and chopped hay at the 90:10 ratio to postweaned calves may decrease solid feed intake and growth.

Effects of finishing diet sorting and digestibility on performance and feed efficiency in beef steers

The aim of this study was to test the hypotheses that differences in residual feed intake (RFI) of beef steers are related to diet sorting, diet nutrient composition, energy intake and apparent digestibility. To phenotype steers for RFI, 69 weaned Angus × Hereford steers were fed individually for 56 days. A finishing diet was fed twice daily on an ad libitum basis to maintain approximately 0.5 to 1.0 kg refusals. Diet offered and refused was measured daily, and DM intakes (DMI) were calculated by difference. Body weights were recorded at 14-day intervals following an 18-h solid feed withdrawal. The residual feed intake was determined as the residual of the regression of DMI versus mid-test metabolic BW (BW0.75) and average daily gain (ADG). Particle size distributions of diet and refusals were determined using the Penn State Particle Separator to quantify diet sorting. Sampling of diet, refusals and feces were repeated in four sampling periods which occurred during weeks 2, 4, 6 and 8 of the study. Particle size distributions of refusals and diet were analyzed in weeks 2, 4 and 6, and sampling for chemical analysis of refusals and feces occurred in all four periods. Indigestible neutral detergent fiber (288 h in situ) was used as an internal marker of apparent digestibility. We conclude that preference for the intakes of particles > 19 mm and 4 to 8 mm were negatively correlated to RFI and ADG, respectively. Although steers did sort to consume a different diet composition than offered, diet sorting did not impact intake energy, digestible energy or DM digestibility.

314 How physically effective fiber affects ruminal pH in beef cattle fed high-concentrate diets

Abstract To assess the effect of physically effective fiber (peNDF) on ruminal pH, 8 Simmental heifers with 258±5.7kg BW were randomly assigned to 1 of 4 treatments in a replicated 4x4 Latin square design. Diets were formulated with an 83 to 17 concentrate to straw ratio, and offered ad libitum as total mixed ration. Barley straw was chopped with a feeder wagon, and then processed either by: a) sifting with the 3-screen Penn State Particle Separator to obtain straw particle size greater than 4 mm, or b) grinding in a hammer mill through a 2-mm screen to obtain straw particle size lesser than 4 mm. Treatments after mixing the processed straws to obtain different peNDF proportions were: 5%, 7%, 9%, and 11%. Concentrate was ground through a 3-mm screen and manually mixed with the straw. The study was performed in 4 3-wk periods: 2-wk diet adaptation and 1-wk sampling. A ruminal bolus (smaXtec, Graz, Austria) was orally inserted in each heifer to measure ruminal pH every 10 min. Dry matter intake was individually measured. Data were analyzed using the mixed procedure of SAS. No significant effects were found in average and minimum pH (6.66 and 5.87 on average, respectively). Time under pH lesser than 5.8 was significantly longer (P &amp;lt; 0.01) in 5% (134 min/d) than 7%, 9% and 11% (63 min/d on average). Time under pH lesser than 5.6 tended to be longer (P = 0.074) in 5% (65 min/d), and shorter in 9% and 11% (25 min/d on average). Time under pH lesser than 5.5 was unaffected by treatment (23 min/d on average). Intake of DM was greater (P &amp;lt; 0.001) in 5% and 7% than 9% and 11%. These results suggest that the risk of subclinical acidosis decreases from 7 to 11% of peNDF, but DMI also decreases in 9% and 11%.

175 Reduce Reuse ReRumen: Variability in nutritive value of paunch manure

Abstract Ruminant animals develop a diverse and complex microbial ecosystem for digesting fibrous feedstuffs, but this material represents a cost to the industry when bound for rendering at harvest. Our objective was to determine the feed value of paunch manure recovered from an abattoir. Twelve paunch samples were collected from slaughtered cattle at the Tarleton State University Meat Laboratory, Stephenville, TX. Samples were dried under forced air at 55°C to a constant weight and ground to pass through 2-mm screen. A subsample was ground to 1-mm and assayed for DM, CP, and sequential NDF and ADF. Physically effective fiber (peNDF) was calculated with 2 L of unground, dried at 55 ˚C, paunch material using the manually-operated Penn State Particle Separator. Paunch peNDF was determined by multiplying the physical effectiveness factor by the total NDF content of the sample. Samples (2-mm) were subject to batch culture in vitro digestibility assays for determination of digestibility coefficients. Data were analysed as a random effects model using PROC GLIMMIX in SAS. Neutral detergent fiber, ADF, ADL, CP, and peNDF values were 68.1, 39.9, 10.9, 15.0, and 38.7%, respectively. Contribution to variance of the individual animal for NDF, ADF, ADL, CP, and peNDF was 97.2, 97.9, 95.4, 19.1, and 97.5%, respectively. In vitro true digestibility (IVTD) and in vitro neutral detergent fiber digestibility (IVNDFD) was recorded as 46.2% and 21.6%, respectively. Contribution to variance of the animal for IVTD and IVNDFD was 99.05 and 98.49%, respectively. Data collected suggest paunch manure could provide valuable nutrients for livestock production, specifically fiber and protein. For full viability of application in a sustainable system, a centralized receiving and compositing system may be useful for development of a consistent product.

9 Reduce Reuse ReRumen: Variability in nutritive value of paunch manure

Abstract Ruminant animals develop a diverse and complex microbial ecosystem for digesting fibrous feedstuffs, but this material represents a cost to the industry when bound for rendering at harvest. Our objective was to determine the feed value of paunch manure recovered from an abattoir. Twelve paunch samples were collected from slaughtered cattle at the Tarleton State University Meat Laboratory, Stephenville, TX. Samples were dried under forced air at 55°C to a constant weight and ground to pass through 2-mm screen. A subsample was ground to 1-mm and assayed for DM, CP, and sequential NDF and ADF. Physically effective fiber (peNDF) was calculated with 2 L of unground, dried at 55 ˚C, paunch material using the manually-operated Penn State Particle Separator. Paunch peNDF was determined by multiplying the physical effectiveness factor by the total NDF content of the sample. Samples (2-mm) were subject to batch culture in vitro digestibility assays for determination of digestibility coefficients. Data were analysed as a random effects model using PROC GLIMMIX in SAS. Neutral detergent fiber, ADF, ADL, CP, and peNDF values were 68.1, 39.9, 10.9, 15.0, and 38.7%, respectively. Contribution to variance of the individual animal for NDF, ADF, ADL, CP, and peNDF was 97.2, 97.9, 95.4, 19.1, and 97.5%, respectively. In vitro true digestibility (IVTD) and in vitro neutral detergent fiber digestibility (IVNDFD) was recorded as 46.2% and 21.6%, respectively. Contribution to variance of the animal for IVTD and IVNDFD was 99.05 and 98.49%, respectively. Data collected suggest paunch manure could provide valuable nutrients for livestock production, specifically fiber and protein. For full viability of application in a sustainable system, a centralized receiving and compositing system may be useful for development of a consistent product.

Reciprocal combinations of alfalfa hay and corn silage in the starter diets of Holstein dairy calves: Effects on feed sorting, meal pattern, and ingestive behavior

We investigated the effects of replacing alfalfa hay (AH) with corn silage (CS) in the starter diet on feed intake, feeding and chewing behavior, and sorting activity using 30 newborn male Holstein calves which were assigned randomly to 3 groups receiving starter diets containing chopped AH [100.00 g/kg on dry matter (DM) basis; AH), CS (100.00 g/kg; CS), or their equal combination (AHCS). The starter diets had the same nutrient composition but differed in DM content (P = 0.001) and thereby, particle size distribution. Feeding AHCS or CS tended to increase day time meal duration (pre-weaning; P = 0.09) and meal frequency (post-weaning; P = 0.08) and tended (P = 0.08) to decrease inter-meal interval (post-weaning), and thereby, tended to increase (P = 0.09) and increased (P = 0.04) day time eating time during the pre- and post-weaning periods, respectively, without affecting nutrient intake or body weight. Calves fed AHCS or CS had lower eating rate during the pre-weaning period (P = 0.03). Concurrent increase in day time rumination frequency (P = 0.04) and duration (P = 0.04) together with a decrease in rumination bout interval (P = 0.03) in calves fed AHCS or CS increased ruminating time (P = 0.001) during the post-weaning period. Time devoted to standing and lying decreased (P = 0.002) and tended (P = 0.06) to decrease, respectively, as the amount of CS increased in the starter diets during the post-weaning period. Calves fed AH or AHCS sorted for the particles retained on second (P = 0.001) and third (P = 0.001) sieves of the Penn State Particle Separator (PSPS) and against the feed materials retained on the bottom pan (P = 0.001); however, calves fed CS sorted against the particles retained on second sieve of the PSPS and for the particles retained on third sieve of the PSPS and feed materials retained on the bottom pan. Crude protein and neutral detergent fiber intakes of particles retained on the both 8.00- and 1.18-mm sieves increased and tended to increase, respectively, in calves fed AHCS or CS compared with calves fed AH. Blood concentration of albumin was higher in calves fed AHCS compared with calves fed AH or CS during the pre-weaning period (P = 0.001). Overall, replacing AH with CS increased day time eating time by increasing meal frequency and duration or decreasing inter-meal interval but did not influence feed intake due to lower eating rate. Finally, calves exhibited feed sorting at the extent to which they balanced intake of nutrients and met their nutritional needs.

Substituting corn silage with reconstituted forage or nonforage fiber sources in the starter feed diets of Holstein calves: Effects on intake, meal pattern, sorting, and health

We examined the effect of replacing corn silage (CS) with reconstituted alfalfa hay (RAH) or reconstituted beet pulp (RBP) in the starter diets on feeding behavior, sorting, and health criteria using 54 neonatal female Holstein calves that were assigned randomly to 3 groups receiving starter diets containing CS (10% on a dry matter basis), RAH, or RBP. The starter diets had the same nutrient composition and moisture level but differed in particle size distribution. Calves fed CS tended to have a lower intermeal interval compared with calves fed RAH before weaning; however, meal frequency and duration, eating rate, and meal size were not affected by treatment before and after weaning, which resulted in no changes in feed intake and time spent eating. Rumination frequency was higher for calves fed CS than for calves fed RAH or RBP after weaning. Feeding RBP decreased rumination duration compared with CS and RAH after weaning; however, calves fed RBP had a higher rumination bout interval compared with calves fed CS. Calves fed CS spent more time ruminating compared with calves fed RAH or RBP after weaning. Feeding CS tended to decrease and decreased time devoted to standing and lying, respectively, compared with calves fed RBP; however, calves fed RBP tended to spend more time on nonnutritive oral behaviors compared with calves fed RAH. Calves fed CS sorted against particles retained on the 8-mm sieve of the Penn State Particle Separator (PSPS) and for particles retained on the 1.18-mm sieve of the PSPS. Feeding RAH increased sorting for particles retained on the 8- and 1.18-mm sieves of the PSPS. Calves fed RBP sorted only for particles retained on the 1.18-mm sieve of the PSPS. Calves fed RBP tended to be more susceptible to developing pneumonia compared with calves fed CS or RAH; however, frequency and duration of diarrhea and pneumonia or number of days needed to medicate the diseases were unchanged across treatment groups. Initial (d 3) blood total protein concentration was similar (6.51 g/dL) across treatment groups. Overall, replacing CS with RAH or RBP did not affect time devoted to eating and feed intake due to no significant changes in meal size or intermeal interval before and after weaning. Calves showed feed sorting at the extent to which they balanced intake of nutrients and met their nutritional needs. Calves in general were healthy; therefore, CS, RAH, or RBP can be used interchangeably based on availability and competitive feed price.

Particle size distribution of forages and mixed rations, and their relationship with ration variability and performance of UK dairy herds

The particle size of the ration has been proposed as a key factor, along with its fibre and non-forage carbohydrate concentration, to ensure healthy rumen function and optimal performance of dairy cows. The current particle size distribution recommendations for forages and rations are primarily based on lucerne-haylage and maize silage (MS) and may not be suitable for the wetter grass silage (GS) based rations typically fed in Northern Europe. In order to characterize the particle size distribution of forages and rations in the UK, fifty commercial dairy herds feeding a range of GS and MS based rations were sampled during the winter of 2015/2016. The particle size distribution of the fresh forages and mixed rations (MR; total and partial mixed rations) were analysed using a modified Penn State Particle Separator with six screens of hole size 60, 44, 26.9, 19, 8, and 4 mm. The fresh MR was collected at 5-equally-spaced locations along the length of the feed-face for each herd within 5-min of feeding to determine the consistency of ration mixing, and again from the same locations 4 h post-feeding. Grass silage was fed on 50 herds, with 80.3% of the dry matter (DM) being retained above the 19 mm sieve, which is considerably higher than the North-American recommendations for lucerne-haylage. The particle size distribution of MS followed the general recommendations for North American forages, however, the 8–19 mm fraction was higher and the <4 mm lower. The >60 mm fraction of the MR had the lowest (0.1% DM) DM retention, and the 8–19 mm fraction the highest (34.9% DM). The MR had a higher proportion of particles retained on the 26.9 mm sieve when GS was the sole forage. Fifty eight % of herds were considered to have either moderately or poorly mixed rations, whilst 66% had evidence of diet selection (either preferential consumption or selective refusals). Particle size of the MR accounted for 33% of the variance in the milk fat content and 12% of milk yield. In conclusion, the particle size distribution of the GS and MR fed on UK dairy herds is different from the current recommendations, suggesting that the particle size of UK dairy rations is too long or new guidelines using additional sieves with larger pore sizes are required. There is also a high proportion of herds with poor mixing and/or evidence of diet selection.

Short communication: Field study to investigate the associations between herd-level risk factors for milk fat depression and bulk tank milk fat percent in dairy herds feeding monensin

Fat is the most variable milk component, and maintaining milk fat continues to be a challenge on commercial dairy farms. Our objectives were to establish associations between herd-level risk factors for milk fat depression and bulk tank milk fat content in commercial dairy herds feeding monensin. Seventy-nine Holstein commercial dairy herds in the northeast and Upper Midwest United States were enrolled in an observational study. Data were collected on herd characteristics, total mixed ration (TMR) samples, all component silage samples, and bulk tank milk samples. The unconditional univariable association of each explanatory variable and bulk tank milk fat percentage was evaluated using simple linear regression and multivariable regression models. Milk fat content of trans-10 C18:1 had an exponentially negative relationship to herd milk fat percentage. In general, milk fat content of fatty acids synthesized de novo in the mammary gland were positively related to herd milk fat, and the content of several trans-C18:1 fatty acids, which would be products of alternate pathways of ruminal biohydrogenation, were negatively related to herd milk fat. Variables related to TMR composition did not have univariable relationships with herd milk fat percentage. Herds that had >49.8% of the TMR particles on the middle screen of the Penn State particle separator had higher milk fat percentage than those with ≤49.8%, and herds with >54.0% of TMR particles in the bottom pan had lower milk fat percentage than herds with ≤54.0%. Dietary content of monounsaturated fatty acids (C16:1 and C18:1) had negative relationships with herd milk fat percentage; however, no single diet component accounted for more than 11% of the variation in herd-level milk fat percentage. Univariable monensin dose was not associated with herd milk fat percentage. The relative lack of significant univariate relationships with herd-level milk fat suggests many factors contribute to milk fat content, and herds experiencing low milk fat will need to examine many potential risk factors when working to troubleshoot this challenge.

Physically adjusted neutral detergent fiber system for lactating dairy cow rations. I: Deriving equations that identify factors that influence effectiveness of fiber

Physically effective neutral detergent fiber (peNDF) is the fraction of neutral detergent fiber (NDF) that stimulates chewing activity and contributes to the floating mat of large particles in the rumen. Multiplying dietary NDF by particle size has been used as an estimate of peNDF. In re-evaluating the concept of peNDF, we compared the use of peNDF as dietary NDF × particle size with the use of individual NDF and particle size descriptors (physically adjusted NDF; paNDF) when used with other physical and chemical diet descriptors to predict dry matter (DM) intake (DMI), rumination time, and ruminal pH in lactating dairy cows. The purpose is to ultimately use these equations to estimate diet adequacy to maintain ruminal conditions. Each response variable had 8 models in a 2 (peNDF, paNDF) × 2 (diet, diet and ruminal factors) × 2 (DM, as fed basis) factorial arrangement. Particle size descriptors were those determined with the Penn State Particle Separator. Treatment means (n = 241) from 60 publications were used in backward elimination multiple regression to derive models of response variables. When available, peNDF terms entered equations. Models containing peNDF terms had similar or lower unadjusted concordance correlation coefficients (an indicator of similar or lower accuracy and precision) than did models without peNDF terms. The peNDF models for rumen pH did not differ substantially from paNDF models. This suggests that peNDF can account for some variation in ruminal pH; however, overt advantages of peNDF were not apparent. Significant variables that entered the models included estimated mean particle size; as fed or DM proportions retained on 19- and 8-mm sieves of the Penn State Particle Separator; DMI; dietary concentrations of forage; forage NDF; CP; starch; NDF; rumen-degraded starch and rumen-degraded NDF; and the interaction terms of starch × mean particle size, acid detergent fiber/NDF, and rumination time/DMI. Many dietary factors beyond particle size and NDF were identified as influencing the response variables. In conclusion, these results appear to justify the development of a modeling approach to integrate individual physical and chemical factors to predict effects on factors affecting rumen conditions.

Physically adjusted neutral detergent fiber system for lactating dairy cow rations. II: Development of feeding recommendations

The objective of this work was to leverage equations derived in a meta-analysis into an ensemble modeling system for estimating dietary physical and chemical characteristics required to maintain desired rumen conditions in lactating dairy cattle. Given the availability of data, responsiveness of ruminal pH to animal behaviors, and the chemical composition and physical form of the diet, mean ruminal pH was chosen as the primary rumen environment indicator. Physically effective fiber (peNDF) is defined as the fraction of neutral detergent fiber (NDF) that stimulates chewing activity and contributes to the floating mat of large particles in the rumen. The peNDF of feedstuffs is typically estimated by multiplying the NDF content by a particle size measure, resulting in an estimated index of effectiveness. We hypothesized that the utility of peNDF could be expanded and improved by dissociating NDF and particle size and considering other dietary factors, all integrated into a physically adjusted fiber system that can be used to estimate minimum particle sizes of TMR and diet compositions needed to maintain ruminal pH targets. Particle size measures of TMR were limited to those found with the Penn State particle separator (PSPS). Starting with specific diet characteristics, the system employed an ensemble of models that were integrated using a variable mixture of experts approach to generate more robust recommendations for the percentage of dietary DM material that should be retained on the 8-mm sieve of a PSPS. Additional continuous variables also integrated in the physically adjusted fiber system include the proportion of material (dry matter basis) retained on the 19- and 8-mm sieves of the PSPS, estimated mean particle size, the dietary concentrations of forage, forage NDF, starch, and NDF, and ruminally degraded starch and NDF. The system was able to predict that the minimum proportion of material (dry matter basis) retained on the 8-mm sieve should increase with decreasing forage NDF or dietary NDF. Additionally, the minimum proportion of dry matter material on the 8-mm sieve should increase with increasing dietary starch. Results of this study agreed with described interrelationships between the chemical and physical form of diets fed to dairy cows and quantified the links between NDF intake, diet particle size, and ruminal pH. Feeding recommendations can be interpolated from tables and figures included in this work.

Effect of forage source included in total mixed ration on intake, sorting and feeding behavior of growing heifers fed high-concentrate diets.

The objective of this experiment was to compare the effects of using 2 different forage sources on intake and sorting and feeding behavior in growing heifers fed a high-concentrate diet offered as a total mixed ration (TMR). Eight Simmental heifers (initial BW of 148.1 ± 4.83 kg) were used in a crossover design experiment. Treatment diets were a TMR with either barley straw (BS) or alfalfa hay (AH) as forage source. Diets were offered on an ad libitum basis, with a forage to concentrate ratio of 8 to 92. The experiment was performed in two 28-d periods, with 3 wk of diet adaptation and 1 wk of sampling in each period. Heifers were weighed before feeding on 2 consecutive days at the beginning and the end of the experiment, and in the sampling week. Feed and refusal samples were collected daily in the sampling week for DM determination and chemical analysis. Particle size separation was performed using the 3-screen Penn State Particle Separator. Dry matter digestibility was estimated using acid-insoluble ash as internal marker. Feeding behavior was recorded using an automated feeding system. Sorting behavior was measured with the intake of different particle size. Dry matter intake was greater ( < 0.05) in heifers fed BS (6.7 kg/d) than AH (5.8 kg/d) when these animals faced TMR for first time in period 1, but DMI did not differ between diets in period 2 when they were accustomed to the method of feeding. Apparent DM digestibility did not differ between diets (62.7 and 64.3% for BS and AH, respectively). Heifers fed BS sorted in both periods against long particle size ( < 0.01) and against medium particle size in period 2 ( < 0.01), a behavior that did not appear in heifers fed AH. Heifers sorted for short particle size in both diets in period 1, this behavior being maintained in period 2 for heifers fed BS, while it disappeared in heifers fed AH. This sorting behavior preferentially shown in heifers fed BS resulted in a tendency ( = 0.06) for greater length of each meal and a longer feeding time ( = 0.02). In conclusion, at 8% of incorporation, forage source affected intake in only 1 of the 2 experimental periods. Heifers fed BS showed a sorting behavior with preferential consumption for concentrate in the TMR, feeding time being greater in BS than in AH. In contrast, heifers fed AH sorted for short particle size when faced for the first time with a new method of feeding, this sorting behavior disappearing once heifers had got familiar with it.

Effects of roughage inclusion and particle size on digestion and ruminal fermentation characteristics of beef steers.

Roughage is fed in finishing diets to promote ruminal health and decrease digestive upset, but the inclusion rate is limited because of the cost per unit of energy and feed management issues. Rumination behavior of cattle may be a means to standardize roughage in beef cattle finishing diets, and increasing the particle size of roughage could modulate the ruminal environment and aid in maintaining ruminal pH. Therefore, this experiment was conducted to determine the effects of corn stalk (CS) inclusion rate and particle size in finishing diets on digestibility, rumination, and ruminal fermentation characteristics of beef steers. Four ruminally cannulated steers were used in a 4 × 4 Latin square experiment. Treatments were arranged as a 2 × 2 factorial with treatments consisting of 5% inclusion of a short-grind roughage (5SG), 10% inclusion of a short-grind roughage (10SG), 5% inclusion of a long-grind roughage (5LG), and 10% inclusion of a long-grind roughage (10LG). Differences in particle size were obtained by grinding corn stalks once (LG) or twice (SG) using a commercial tub grinder equipped with a 7.6-cm screen and quantified using the Penn State Particle Separator (PSPS) to estimate physically effective NDF (peNDF). Each period included 14 d for adaptation and 4 d for diet, fecal, and ruminal fluid collections. Animals were outfitted with rumination monitoring collars to continuously measure rumination activity. The 10LG treatment had a greater ( < 0.01) percentage of large particles (retained on the top 3 sieves of the PSPS) compared to the other treatments. This resulted in a greater ( < 0.01) percentage of estimated peNDF for the 10LG diet compared to the others. Feeding diets containing 5% roughage tended to increase ( ≤ 0.09) DM, NDF, and starch total tract digestibility compared to diets containing 10% roughage. Cattle consuming LG treatments had greater ( < 0.01) rumination time and greater ( < 0.01) ruminal pH than cattle consuming diets containing SG roughage. Cattle receiving the 5% inclusion rate of roughage tended to have greater ( = 0.09) time (h/d) under a ruminal pH of 5.6 and a larger ( = 0.03) area under the threshold compared to cattle receiving the 10% roughage treatments. Overall, feeding a lower inclusion of roughage with a larger particle size may stimulate rumination and aid in ruminal buffering similar to that of a higher inclusion of roughage with a smaller particle size, without negatively impacting digestibility and fermentation.

Effects of roughage inclusion and particle size on performance and rumination behavior of finishing beef steers.

Roughage is typically mechanically processed to increase digestibility and improve handling and mixing characteristics in beef cattle finishing diets. Roughage is fed to promote ruminal health and decrease digestive upset, but inclusion in finishing diets is limited due to the cost per unit of energy. Rumination behavior may be a means to standardize roughage in beef cattle finishing diets, and increasing particle size of roughage may allow a decrease in roughage inclusion without sacrificing animal performance. Therefore, the objectives of this study were to quantify rumination time for a finishing beef animal and to evaluate the effects of corn stalk (CS) inclusion rate and particle size on rumination behavior, animal performance, and carcass characteristics. Fifty-one individually fed steers (385 ± 3.6 kg initial BW) were used in a randomized complete block design feeding study. Corn stalks were passed through a tub grinder equipped with a 7.62-cm screen once to generate long-grind CS (LG-CS) or twice to generate short-grind CS (SG-CS). Dietary treatments were based on steam-flaked corn and included, on a DM basis, 30% wet corn gluten feed (WCGF) with 5% SG-CS (5SG), 30% WCGF with 5% LG-CS (5LG), and 25% WCGF with 10% SG-CS (10SG). The Penn State Particle Separator was used to separate ingredients and treatment diets and to estimate physically effective NDF (peNDF). On d 70, each steer was fitted with a collar (HR Tag; SCR Dairy, Netanya, Isreal), which continuously measured rumination minutes via a sensory microphone. Long-grind CS contained more ( < 0.01) peNDF than SG-CS, and the 10SG diet contained more ( = 0.03) peNDF than the 5LG and 5SG diets. Dry matter intake was greatest ( = 0.03) for steers consuming 5LG and least for steers consuming 10SG, with cattle consuming 5SG being intermediate. Carcass-adjusted ADG and G:F were greatest ( ≤ 0.03) for steers consuming 5LG and 5SG compared with steers consuming 10SG. Hot carcass weight tended ( = 0.10) to be greatest for steers consuming 5LG and least for steers consuming 10SG, with steers consuming 5SG being intermediate. Dressing percent was greater ( = 0.01) for steers consuming 5LG and 5SG than for steers consuming 10SG. A significant interaction ( < 0.01) occurred for rumination minutes × day. Rumination (min/day) were greatest ( = 0.01) for steers consuming 10SG followed by steers consuming 5LG and was lowest for steers consuming 5SG. Increasing particle size of roughage may be a means to decrease roughage inclusion rate while maintaining rumination and performance.