Effects of the level and source of dietary physically effective fiber on feed intake, nutrient utilization, heat energy, ruminal fermentation, and milk production by Alpine goats.

Thirty-two primiparous and 31 multiparous Alpine goats were used to determine influences of diets varying in level and source of forage on performance in early to mid-lactation for 16 wk. Diets consisted of 40%, 50%, 60%, and 70% forage (designated as 40F, 50F, 60F, and 70F, respectively) with 60F and 70F containing coarsely ground grass hay (primarily orchardgrass) and 40F and 50F containing cottonseed hulls, alfalfa pellets, and coarsely ground wheat hay. Diets contained 15.9% to 16.3% crude protein and 37.8%, 42.1%, 53.5%, and 55.4% neutral detergent fiber (NDF) with 10.0%, 15.8%, 50.1%, and 55.5% particle retention on a 19-mm sieve, and 26.1%, 29.6%, 38.3%, and 40.0% physically effective NDF (peNDF) for 40F, 50F, 60F, and 70F, respectively. Dry matter intake (2.71, 2.75, 1.96, and 1.95 kg/d) and milk yield (2.82, 2.71, 2.23, and 2.10 kg/d for 40F, 50F, 60F, and 70F, respectively) were lower (P < 0.05) for the two diets highest in forage. Digestion of organic matter was similar among diets (P > 0.05), but digestibility of NDF was greater (P < 0.05) for 60F and 70F (57.5%, 58.4%, 68.9%, and 72.2% for 40F, 50F, 60F, and 70F, respectively). Diet affected (P < 0.05) milk fat (3.16%, 3.37%, 2.93%, and 2.97%) and protein concentrations (2.62%, 2.69%, 2.58%, and 2.52% for 40F, 50F, 60F, and 70F, respectively). Milk energy yield was greater (P < 0.05) for the two diets lowest in forage (7.51, 7.45, 5.68, and 5.34 MJ/d), although yield relative to dry matter intake was not affected (P > 0.05) by diet and was lower (P < 0.05) for primiparous vs. multiparous goats (2.71 and 3.09 MJ/kg). Ruminal pH and acetate proportion were greater for 60F and 70F than for the other diets and the proportion of butyrate was lower for the two diets highest in fiber. The mean lengths of time spent ruminating, eating, standing, and lying were not affected (P > 0.05) by diet or parity, but many interactions involving diet, period, hour, and parity were significant (P < 0.05). In conclusion, lactational performance of Alpine goats in early to mid-lactation will be constrained with diets high in forage of moderate quality, peNDF content, and large particle size, which appeared related to limited feed intake.

In Vitro Digestibility and Models of Cumulative Gas Production of Forage-Free Diet.

Our objectives were to evaluate the use of cottonseed cake in replacing corn silage in a diet without forage and to identify the model with higher precision and accuracy of adjustment of parameters of ruminal degradation kinetics. A diet containing corn silage and another with cottonseed cake as a fiber source were formulated. Gompertz, Dual-pool Logistic, Brody, and Ørskov models were evaluated for goodness of fit to gas production. There were significant differences in dry matter (DM), organic matter (OM), and neutral detergent fiber (NDF) in the in vitro digestibility for diets and fiber sources. The estimated values of the Gompertz (6.77), Brody (6.72), and Ørskov (6.73) models were similar to the observed mean of gas production in the corn silage diet (6.73 mL/100 mg DM). Similarly, the estimated values of the Brody (5.87) and Ørskov (5.89) models were similar to the observed mean of gas production in the cottonseed cake diet (5.87 mL/100 mg DM). The roughage-free diet containing cottonseed cake as a fiber source stimulated higher gas production. Brody and Ørskov models presented higher precision and accuracy in the fitting of kinetics of degradation independent of the fiber source in the diet.

Cactus cladodes for dairy goats: what is the best fiber source?

This study evaluated the effect of different fiber sources supplied with cactus cladodes in diets on the intake and digestibility of nutrients, ingestive behavior, milk yield, and composition of dairy goats. The fiber sources were corn silage, sorghum silage, Digitaria pentzii Stent. hay, and sugarcane bagasse. Twelve Saanen goats with an average weight of 48.9 ± 7.3 kg and average production of 2.8 ± 0.7 kg of milk/day were assigned in three simultaneous 4 × 4 Latin squares (four animals, four treatments, and four experimental periods). There was no difference between the fiber sources for intake (P > 0.05) of dry matter (2.58 kg/day), organic matter (2.30 kg/day), crude protein (0.385 kg/day), neutral detergent fiber (0.895 kg/day), non-fibrous carbohydrates (0.858 kg/day), and metabolizable energy (5.66 Mcal/day). Also, the fiber sources did not influence dry matter and nutrient digestibility (P > 0.05). The association of cactus cladodes with silages, hay, and sugarcane bagasse did not change milk production, milk production corrected for 3.5% of fat and corrected for energy (2.78; 2.53 and 2,55 kg/day, respectively), in addition to milk composition (P > 0.05). No differences were observed in ingestive behavior (P > 0.05). Any fiber sources evaluated are recommended.

Whole-plant flint corn silage inclusion in total mixed rations for pre- and postweaning dairy calves.

Assuming that acetic acid plays a minor role in the development of ruminal epithelium of preweaning dairy calves, the fiber supply for growing calves has been neglected. More research has been done on including starch and nonfibrous carbohydrates in solid feed for preweaning calves. Accordingly, the fiber requirement of these calves is not well known, as diet recommendations vary greatly. Hence, elucidating the effects of including fiber from long particle sizes in the diet may be essential for helping calves overcome the transition challenge during weaning. Forty-five Holstein calves were used in a randomized block design, considering sex, birth date, and weight at 28 d of age, when the supply of the total mixed ration (TMR) with the inclusion of corn silage started. Three TMR with increasing whole-plant flint corn silage content (0, 10, or 20% on a dry matter basis) were compared: 0CS, 10CS, or 20CS, respectively. During the first 28 d of life, the calves were managed homogeneously and were fed 6 L/d of whole milk, a commercial calf starter pelleted, and water ad libitum. Next, the solid diet was changed to the respective solid feed treatment. Calves were gradually weaned from 52 to 56 d of age but were evaluated for an additional 14 d postweaning. Feed intake was measured daily, while body weight and metabolic indicators of intermediate metabolism were evaluated weekly. Ruminal fluid was collected at 6, 8, and 10 wk of age. Behavioral analysis was conducted on wk 7 (preweaning) and 10 (postweaning). There was a quadratic effect for dry matter intake from wk 7 to 10, with higher intake for the 10CS diet than the 0CS and 20CS diets. Consequently, the 10CS diet also promoted greater average daily gain at wk 8 and 9 compared with the 0CS and 20CS diets. However, the final body weight was not affected by the different solid diets. Silage inclusion in calves' diet positively affected time spent ruminating and chewing pre- and postweaning. Including 10% of whole-plant flint corn silage in the diets of young dairy calves is a strategy to increase total solid intake and decrease acidosis risk by increasing pH and ruminating activity around weaning.

Physical effectiveness of corn silage fractions stratified with the Penn State Particle Separator for lactating dairy cows.

This study evaluated the physical effectiveness of whole-plant corn silage (CS) particles stratified with the Penn State Particle Separator, composed of 19- and 8-mm-diameter sieves and a pan, for lactating dairy cows. Eight Holstein cows (27.6 ± 2.8 kg/d of milk, 611 ± 74 kg body weight; 152 ± 83 d in milk) were assigned to two 4 × 4 Latin squares (22-d periods, 16-d adaptation), where one square was formed with rumen-cannulated cows. Three CS particle fractions were manually isolated using the 8- and 19-mm diameter sieves and re-ensiled in 200-L drums. The 4 experimental diets were (% dry matter): (1) CON (control): 17% forage neutral detergent fiber (NDF) from CS (basal roughage), 31.5% starch, and 31.9% NDF; (2) PSPan: 17% forage NDF from CS + 9% NDF from CS particles <8 mm, 25.9% starch, and 37.9% NDF; (3) PS8: 17% forage NDF from CS + 9% NDF from CS particles 8 to 19 mm, 25.5% starch, and 38.3% NDF; and (4) PS19: 17% forage NDF from CS + 9% NDF from CS particles >19 mm, 24.9% starch, and 38.8% NDF. Cows fed PS8 had greater dry matter intake and energy-corrected milk yield (22.4 and 26.9 kg/d, respectively) than cows fed CON (20.8 and 24.7 kg/d) and PS19 (21.2 and 24.8 kg/d), but no difference was detected between PSPan (21.6 and 25.8 kg/d) and other treatments. Milk fat concentration was greater for PS8 than CON, with intermediate values for PSPan and PS19. Milk fat yield was greater for cows fed PS8 than CON and PS19, and cows fed PSPan secreted more fat than CON cows but were not different from cows fed the other 2 diets. Cows fed CON had a lower meal frequency than cows fed PSPan, shorter meal and rumination times than PS8, and greater meal size and lower rates of rumination and chewing than the other 3 diets. Total chewing per unit of NDF was higher for PS8 than PSPan, although neither treatment differed from CON or PS19. Cows fed PS19 had higher refusal of feed particles >19 mm than cows fed CON and PSPan. The refusal of dietary NDF and undigested NDF in favor of starch were all greater for PS19 than on the other treatments. Cows fed PS19 had a greater proportion of the swallowed bolus and rumen digesta with particles >19 mm than the other 3 diets. Cows fed CON had the lowest ruminal pH and greatest lactate concentration relative to the other 3 diets. Plasma lipopolysaccharide was higher for cows fed CON and PSPan than for cows fed PS8 and PS19, and serum d-lactate tended to be lower on PSPan than for CON and PS8. In summary, the inclusion of CS fractions in a low-forage fiber diet (CON) reduced signs of ruminal acidosis. Compared with CS NDF <8 and >19 mm, CS NDF with 8- to 19-mm length promoted better rumen health and performance of dairy cows. These results highlight the importance of adjusting CS harvest and formulating dairy diets based on the proportion of particles retained between the 8- and 19-mm sieves.

Effect of physically effective neutral detergent fiber on nutrient intake and digestibility, ruminal and blood parameters, and ingestive behavior of confined beef cattle.

We aimed to evaluate the effect of levels of physically effective neutral detergent fiber from forage (NDFfor) on confined cattle's metabolism and ingestive behavior. Four crossbred steers (514.0 ± 4.54 kg BW) rumen-cannulated were used. The animals were randomly distributed in a 4×4 Latin square design, and the treatments were diets with 9.5%, 5.5%, 2.5%, and 0.0% NDF from whole plant corn silage. The trial was divided into 4 periods of 21 days. The dry matter, organic matter (OM), crude protein, neutral detergent fiber (NDF), physically effective NDF 8mm (peNDF8mm) and NDF1.18mm intakes, and the digestibility of OM and NDF showed a quadratic behavior. The rumen pH values showed a decreasing linear, and the time at pH below 5.8 increased linearly in the diets with lower NDFfor. The production of volatile fatty acids and the proportions of propionate and butyrate showed an increasing quadratic behavior. On the other hand, the proportion of acetate fitted a decreasing quadratic equation. With the lower participation of forage in the diets, the time spent on rumination activity decreased in a quadratic way, and the time spent in idleness increased in a quadratic way. The corn silage can be reduced to 135 g/kg DM in the diet to obtain a minimum of 5.5% of NDF from roughage.

Symposium review: Physical characterization of feeds and development of the physically effective fiber system.

Historical research had shown that forage particle size influences chewing activity, ruminal pH, volatile fatty acid profiles, and milk fat percentage. With this in mind, Mertens in 1997 published one of the most frequently cited papers in the Journal of Dairy Science that laid out a comprehensive system for integrating neutral detergent fiber (NDF) and particle size of feeds into one measure: physically effective NDF (peNDF). Based on total chewing time (i.e., eating plus ruminating), peNDF enabled ration formulation to meet the minimum fiber requirements of ruminants to maintain ruminal pH and milk fat. Total chewing time is related to feed NDF content and particle size, so Mertens proposed that peNDF could be determined simply from a chemical measure of NDF and particle size measured as the fraction of dry matter retained on a 1.18-mm sieve with vertical shaking of a dried sample. In the past 2 decades, the peNDF system has been incorporated into nutrition models and is routinely used in ration formulation. Early on, Mertens recognized that starch would affect the minimum peNDF requirements, and his work was the first to demonstrate that starch and fermentation pH affect ruminal fiber degradation kinetics. Subsequently, Mertens's insight into particle size analysis was extended from fibrous feeds to corn silage processing with the development of the commonly used corn silage fragmentation index for assessing starch availability. Participants at the 33rd Discover Conference on fiber in 2017 ranked improved physical description of feeds as a top priority for future research, undoubtedly recognizing the need to carry forward Mertens's pioneering work. Future research will likely focus on improving the physicochemical and biological evaluation of rumen fiber degradation and passage, thereby improving the prediction of animal response. The comprehensive system that David Mertens built for meeting the fiber requirements of ruminants has transformed ration formulation.

Fibrous coproducts of corn and citrus as forage and concentrate sources for dairy cows.

This study evaluated the effect on dairy cows of the partial replacement of whole plant corn silage (WPCS) with corn ear fibrous coproduct (CEFC) in diets with concentrate coproducts from citrus and corn on dry matter intake (DMI), lactation performance, digestibility, and chewing behavior. Holstein dairy cows (n = 20) in 5, 4 × 4 Latin squares (21-d periods) were fed a combination of strategies for feeding fibrous coproducts in a 2 × 2 factorial arrangement of the following treatments: (1) forage feeds: the partial replacement of WPCS (CS) with CEFC (CO), and (2) concentrate feeds: the partial replacement of wet corn gluten feed (GF) with a blend of pelleted citrus and corn distillers dried grains (CD) to have isonitrogenous diets. The concentrations of physically effective neutral detergent fiber (NDF; peNDF>8) were (% of dry matter): 21.8% for CS, 19.2% for CO, 20.7% for GF, and 20.2% for CD. Cows fed diet CS-CD had the highest yield of energy-corrected milk (30.0 kg/d) relative to the other diets (28.4 kg/d). Milk fat concentration was reduced on CO relative to CS. Cows fed the CO diets had higher DMI (21.2 vs. 20.2 kg/d) and digestible organic matter intake and tended to have a lower ratio of energy-corrected milk to DMI than cows fed CS. Diets CO reduced the daily intake of peNDF>8 and the intake as percent of body weight of peNDF>8, forage NDF, and total NDF relative to CS. Cows fed CO had greater meal frequency and lower daily meal time, meal duration, meal size, and duration of the largest meal than cows fed CS. The CO diet reduced rumination and total chewing in minutes per day and minutes per kilogram of DMI. When expressed per unit of peNDF>8 intake, rumination and total chewing were not affected by forage source. The total-tract starch digestibility coefficient was lower for cows fed CO than CS, but the intake of digestible starch was higher on CO than CS. Cows fed GF had reduced milk yield (29.6 vs. 30.8 kg/d), tended to have reduced DMI (20.4 vs. 21.0 kg/d), and had reduced digestible organic matter intake than cows fed CD. Feed efficiency was not affected by source of concentrate. The type of concentrate did not affect the intake of forage NDF and peNDF>8, but cows fed GF had higher intake of total NDF as percent of body weight than cows fed CD. The GF increased meal frequency and reduced meal size and largest meal duration and size. Cows fed GF had higher rumination and total chewing than cows fed CD (min/d, min/kg of DMI, and min/kg peNDF>8). Starch digestibility was higher and the intake of digestible starch tended to be higher on cows fed GF than CD. Plasma urea-N was higher, milk urea-N tended to be higher, and N utilization efficiency tended to be lower on cows fed GF than CD. Ruminal microbial yield was not affected by any treatment. All strategies evaluated were nutritionally viable and CEFC was a feasible partial replacement for WPCS.

Impacts of including Sweet Bran and wet distillers grains with solubles alone or in combination in finishing cattle diets on physically effective fiber concentrations and rumen buffering characteristics of feedlot cattle.

This study evaluated the effects of Sweet Bran (SB) and wet distillers grains with solubles (WDGS) in the diet alone or in combination on physically effective neutral detergent fiber (peNDF), ruminal pH, and rumination behavior of finishing beef cattle. For this study, 455 steers (373 ± 15.5 kg) were allocated to 48 pens in a randomized complete block design. Treatments (n = 12 pens per treatment) were one of four steam-flaked corn-based diets containing no corn-milling products (CON), 20% WDGS (WDGS20), 20% SB (SB20), or 20% SB and 10% WDGS (COMBO). Within each pen, two steers were randomly selected to receive an indwelling ruminal pH bolus to quantify ruminal pH and a 3-axis accelerometer tag to measure rumination for the first 92 d of the study. Diet samples were collected weekly to determine particle size, neutral detergent fiber (NDF) concentration, and peNDF. Physically effective NDF was calculated using both the proportion of particles > 4.0 mm (peNDF4.0 ) and the proportion of particles > 8.0 mm (peNDF8.0). The percentage of particles > 4.0 mm was greatest (P < 0.01) for CON, intermediate for SB20, and least for WDGS20 and COMBO. Both NDF (P < 0.01) and peNDF4.0 (P < 0.01) were greatest for COMBO, intermediate for WDGS20 and SB20, and least for CON. The percentage of particles > 8.0 was greatest (P < 0.01) for CON, intermediate for WDGS20 and SB20, and least for COMBO, but peNDF8.0 did not differ (P = 0.40). A diet × day interaction (P < 0.01) was observed for daily rumination minutes per kg of DMI, NDF, peNDF4.0, and peNDF8.0. A diet × hour interaction (P < 0.01) was observed where CON cattle spent less time ruminating at 0800 and 1000 h in a 24 h period. Daily ruminal pH was greatest (P < 0.01) for COMBO, intermediate for SB20 and WDGS20, and least for CON. A diet × hour interaction (P < 0.01) was also observed for circadian ruminal pH, where pH was least for CON from 0800 to 1800 h. Relationships between peNDF, rumination behavior, and ruminal pH observed in this study suggest that SB and WDGS similarly enhance rumen buffering capacity when steam-flaked corn is replaced in the diet.

Models to predict the risk of subacute ruminal acidosis in dairy cows based on dietary and cow factors: A meta-analysis.

The present research aimed at developing practical and feasible models to optimize feeding adequacy to maintain desired rumen pH conditions and prevent subacute ruminal acidosis (SARA) in dairy cows. We conducted 2 meta-analyses, one using data from recent published literatures (study 1) to investigate the prediction of SARA based on nutrient components and dietary physical and chemical characteristics, and another using internal data of our 5 different published experiments (study 2) to obtain adjustments based on cow status. The results of study 1 revealed that physically effective neutral detergent fiber inclusive of particles >8 mm (peNDF >8) and dietary starch [% of dry matter (DM)] were sufficient for predicting daily mean ruminal pH {y = 5.960 - (0.00781 × starch) + (0.03743 × peNDF >8) - [0.00061 × (peNDF >8 × peNDF >8)]}. The model for time of pH suppression (<5.8 for ruminal pH or <6.0 for reticular pH, min/d) can be predicted with additionally including DMI (kg/d): 124.7 + (1.7007 × DMI) + (20.9270 × starch) + (0.2959 × peNDF >8) - [0.0437 × (DMI × starch × peNDF >8)]. As a rule of thumb, when taken separately, we propose 15 to 18% peNDF >8 as a safe range for diet formulation to prevent SARA, when starch or NFC levels are within 20 to 25% and 35 to 40% ranges, respectively. At dietary starch content below 20% of DM, grain type was insignificant in affecting ruminal pH. However, increasing dietary starch contents by using corn as the sole grain source could lead to more severe drops of pH compared with using grain mix based on barley and wheat, as underlined by an interaction between starch content and grain type. Data from study 2 emphasized an increased risk of SARA for cows in the first and second lactation with lower mean pH (0.2 units) and double amounts of time at pH <5.8 compared with the cows with ≥3 parities. Given that a lower ruminal pH is expected in these high-risk cows, it is advisable to keep the lower end of recommended starch (20%) and higher peNDF >8 (18%) contents in the diet of these cows. Overall, the present study underlines the possibility of predicting SARA based on dietary factors including peNDF >8 and starch contents, as well as DMI of the cows, which can be practically implemented for optimal diet formulation for dairy cows. With more data available, future studies should attempt to improve the predictions by including additional key dietary and cow factors in the models.

Performance of growing lambs supplemented with ground licuri (Syagrus coronata).

OBJECTIVE: The aim of this study was to determine the effect of dietary ground licuri on lamb performance. METHODS: Forty male lambs were used in a completely randomized design to test the effects of 0, 5, 10, and 15 g/kg of ground licuri added to diets. The trial lasted for 75 days. Intake, digestibility, physically effective neutral detergent fiber, and chewing activity were estimated. Blood samples were taken on day 45 to determine the concentrations of glucose, urea, nonesterified fatty acids, and triglycerides. Average daily gain (ADG) were determined on the last day of the experimental trial. RESULTS: Licuri inclusion markedly increased dietary neutral detergent fiber and ether extract (EE) content, but it decreased dry matter (DM) intake. However, the intake and digestibility of EE linearly increased. The ADG decreased linearly (p<0.05) with licuri inclusion. Licuri had no effect (p>0.05) on the concentrations of blood metabolites; however, blood urea increased (p<0.05), while serum glucose decreased (p<0.05). CONCLUSION: The physically effective fiber of ground licuri is similar to Tyfton hay and licuri inclusion decreases lamb performance due to a decreased in DM intake.

Distinct responses in feed sorting, chewing behavior, and ruminal acidosis risk between primiparous and multiparous Simmental cows fed diets differing in forage and starch levels.

During early lactation, both primiparous (PP) and multiparous (MP) cows are commonly fed diets rich in starch and low in forages to support their high energy requirements. Yet, the PP cows experience this dietary challenge for the first time, which might result in higher odds for them to develop rumen and systemic health disorders. The primary objective of this study was to evaluate the effect of decreasing the amount of forages in the diet on chewing and sorting behaviors and rumen and systemic health variables in PP and MP dairy cows. Twenty-four lactating Simmental cows [8 PP, average dry matter intake (DMI) of 19.1 ± 1.1 kg/d; 16 MP, average DMI of 22.5 ± 1.1 kg/d] with a body weight of 737 ± 90 kg and 50 ± 22 days in milk were used in this study. Cows were first fed a total mixed ration with 60% forage and 40% concentrate [on a dry matter (DM) basis] considered marginal in forages for 2 wk. Then, cows were switched to a diet low in forages with 40% forage and 60% concentrate (on a DM basis) for 4 wk. Reticular pH was measured continuously with wireless pH-sensors inserted into the reticulum to calculate the subacute ruminal acidosis (SARA) index. Chewing activity was measured with noseband-sensor halters, and feed sorting was measured weekly. Blood samples were collected weekly and analyzed for metabolic and inflammation markers. Switching PP and MP cows from a marginal to low-forage diet decreased the time spent eating and ruminating per kilogram of DM. Primiparous cows chewed longer per kilogram of DMI than MP cows. Also, the PP cows sorted more pronounced for longer particles and against fine particles than MP cows did. Despite higher rumination activity per kilogram of DMI and the adaptive sorting behavior, the PP cows spent on average 4.6 h/d longer below a pH of 5.8 and had a higher SARA index (i.e., area pH <5.8/DMI) than MP cows, especially during the first week of the low-forage diet (9.5 vs. 4.8). The concentration of liver enzymes increased with the low-forage diet, which was especially pronounced in the PP cows. In conclusion, this study demonstrated greater susceptibility of PP cows to SARA and liver damage than MP cows fed the same diets. Although PP cows demonstrated greater chewing and ruminating activity per kilogram of DMI, as well as adapted sorting behavior in favor of large particles during the low-forage high-starch feeding, they developed more severe signs of SARA. This suggests higher forage fiber requirements for PP cows and the need for improved feeding strategies to mitigate rumen fermentation disorders during early lactation in these cows.

Increasing the content of physically effective fiber in high-concentrate diets fed to beef heifers affects intake, sorting behavior, time spent ruminating, and rumen pH.

AbstractThe importance of fiber particle size in ruminal health is well known, but there are fewer studies to assess the requirements of physically effective NDF (peNDF) in beef cattle than in dairy cattle. The objective of this study was to establish the optimal peNDF proportion in high-concentrate diets fed to beef cattle, to reduce the risk of subacute ruminal acidosis. The experimental design was a replicated Latin Square 4 × 4, with four periods of 21 d. Treatments consisted of four diets with different peNDF proportions: 6.4%, 10.4%, 13.6%, and 15.4%, offered ad libitum as total mixed ration, and containing 15% barley straw and 85% concentrate. Diets, which differed in proportions of straw > 4 mm (considered peNDF) and straw < 4 mm, were manually mixed with concentrate. This concentrate was the same for all diets. A ruminal bolus was orally administered to each heifer for pH measurement. Intake, water consumption, intake by particle size, feed sorting, feeding behavior, behavioral activities, and rumen pH were recorded. Chemical composition and particle sizes of diets offered were assessed in the last week of each period. Data were analyzed using the MIXED procedure of SAS. Orthogonal contrasts determined the linear and quadratic effects of increasing peNDF proportion. T-test procedure determined whether heifers carried out sorting behavior. Particles >4 mm linearly increased (P = 0.001), and particles <4 mm linearly decreased (P = 0.001) as peNDF increased. Water consumption and feeding behavior were unaffected by treatment. As peNDF increased, intakes of DM and NDF linearly decreased (P = 0.001), whereas peNDF intake increased (P = 0.001). Intake of particles > 4 mm linearly increased, whereas intake of particles < 4 mm linearly decreased (P = 0.001) as peNDF increased. Diet 6.4% performed sorting for particles > 4 mm (P < 0.01), and diets 13.6% and 15.4% against particles > 4 mm (P < 0.01). Diet 10.4% tended to sort against particles > 4 mm (P < 0.10). Time spent ruminating linearly increased (P = 0.001) as peNDF increased. Diets did not differ in mean and minimum rumen pH, but time under rumen pH thresholds (5.8, 5.7, 5.6, and 5.5) linearly decreased as peNDF increased (P < 0.05). The results suggested that the diet that best met the requirements of not compromising intake, limiting sorting behavior, and promoting time spent ruminating to reduce the number of hours under rumen pH thresholds, was the 10.4% diet.

Effect of stocking density and effective fiber on the ruminal bacterial communities in lactating Holstein cows.

Overstocking can be a major issue in the dairy cattle industry, leading to negative changes in feeding and resting behavior. Additional stress imposed and alterations in feeding behavior may significantly impact the rumen microbiome. The rumen microbiome is responsible for the successful conversion of feed to usable energy for its host. Thus, understanding the effects of stocking density on the rumen microbiome is imperative for further elucidation of potentially negative consequences of overstocking in dairy cattle. This study implemented a Latin Square design accounting for four pens of cattle and four treatment periods so that all treatment combinations were assigned to every pen during one period of the study. Two treatment factors, including two levels of physically effective neutral detergent fiber, achieved with addition of chopped straw, and stocking density (100% vs. 142%) of freestalls and headlocks, were combined and tested within a factorial treatment design. Within each pen, three or four cannulated cows (n = 15 total) were sampled for rumen content on the final day of each treatment period. Each treatment was randomly assigned to a single pen for a 14-day period. The V1-V3 hypervariable regions of the 16S rRNA gene were targeted for bacterial analyses. Variables with approximately normally-distributed residuals and a Shapiro-Wilk statistic of ≥0.85 were analyzed using a mixed model analysis of variance with the GLIMMIX procedure with fixed effects of feed (straw vs. no straw), stocking density (100% vs. 142%), and the interaction of feed × stocking density, and random effects of pen, period, feed × stocking × pen × period. Pen was included as the experimental unit in a given period and the sampling unit as cow. Variables included Shannon's Diversity Index, Faith's phylogenetic diversity index, chao1, observed OTU, and Simpson's evenness E as well as most individual taxa. Data were analyzed in SAS 9.4 utilizing the GLIMMIX procedure to perform mixed model analysis of variance. If data were not normally distributed, a ranked analysis was performed. No differences were observed in α-diversity metrics by fiber or stocking density (P > 0.05). Beta diversity was assessed using weighted and unweighted Unifrac distances in QIIME 1.9.1 and analyzed using ANOSIM. No differences were observed in weighted (P = 0.6660; R = -0.0121) nor unweighted (P = 0.9190; R = -0.0261) metrics and R values suggested similar bacterial communities among treatments. At the phylum level, Tenericutes differed among treatments with an interaction of stocking density by feed (P = 0.0066). At the genus level, several differences were observed by treatment, including Atopobium (P = 0.0129), unidentified members of order RF39 (P = 0.0139), and unidentified members of family Succinivibrionaceae (P = 0.0480). Although no diversity differences were observed, taxa differences may indicate that specific taxa are affected by the treatments, which may, in turn, affect animal production.

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 physically effective fiber in diets based on rice straw and cassava pulp on chewing activity, ruminal fermentation, milk production, and digestibility in dairy cows.

The objective of this study was to evaluate the effects of physically effective neutral detergent fiber (peNDF) in rice straw and cassava pulp diets on the chewing activity, ruminal fermentation, milk production, and digestibility in low-producing dairy cows. Eight lactating Holstein crossbred cows were randomly divided into two groups in a crossover design with two dietary treatments over two 21-day periods. The difference in peNDF contents was achieved by balancing the ratio of rice straw, cassava pulp, and concentrate. The high cassava pulp diet had 15.5% peNDF and the low cassava pulp diet had 20.2% peNDF. The results showed that feeding the low cassava pulp diet increased the concentrations of milk protein, milk fat, solids-not-fat, and total solids in the milk. In contrast, the dry matter intake, milk yield, lactose content, chewing activity, nutrient digestibility, ruminal fermentation, and pH were not affected by treatments.

Relationship between forage neutral detergent fiber and non-fibrous carbohydrates on ruminal fermentation products and neutral detergent fiber digestibility in goats / Relación entre la fibra detergente neutra del forraje y los carbohidratos no fibrosos sobre los productos de la fermentación ruminal y digestibilidad de la fibra detergente neutra en cabras / Efeito da relação da fibra em detergente neutro advindo de forragem e carboidratos não fibrosos sobre os produtos da fermentação ruminal e digestibilidade da fibra em detergente neutro em caprinos

Abstract Background: There is a comprehensive understanding of the role of dietary fiber as a nutrient and its function during digestion in cattle. On the other hand, the role of fiber digestion in goats has not received similar attention. Objective: To evaluate the effects of different ratios of forage neutral detergent fiber (fNDF) and non-fibrous carbohydrates (NFC) on ruminal fermentation products, and in vitro neutral detergent fiber (NDF) digestibility in goats. Methods: A 3 × 5 factorial arrangement in a completely randomized design with three fNDF levels (100, 190, and 290 g/kg) and five NFC levels (350, 400, 450, 500, and 550 g/kg) was used. The experiment was performed in vitro. Two ruminally fistulated goats were used as rumen liquid donors. Results: The ratios between fNDF and NFC affected all ruminal parameters (p<0.05). Increasing NFC levels in diets containing 100 and 290 g/kg fNDF resulted in linear increase (p<0.05) in ammonia concentration after 48 h fermentation. There was no adjustment of linear models (p>0.05) for pH values. Total volatile fatty acids (VFA) and their individual molar proportions were affected (p<0.05) at all fNDF and NFC levels. The NDF digestibility was not affected (p>0.05) by fNDF or NFC levels, except for diets containing 290 g/kg fNDF, which were fit to a quadratic model (p<0.05). Conclusion: The relationship between fNDF and NFC concentrations affect the fermentation end products and in vitro NDF digestibility. NFC plays a more consistent role than fNDF in the ruminal microbial ecosystem of goats during in vitro fermentation.

Resumen Antecedentes: Aunque hay una amplia comprensión del papel que juega la fibra dietética como nutriente y su función durante la digestión en el ganado vacuno, el papel de la digestión de la fibra en las cabras no ha recibido una atención similar. Objetivo: Evaluar los efectos de diferentes proporciones de fibra detergente neutra proveniente del forraje (fNDF) y carbohidratos no fibrosos (NFC) sobre los productos de la fermentación ruminal y la digestibilidad in vitro de la fibra detergente neutra (NDF) en cabras. Métodos: Se utilizó un arreglo factorial de 3 × 5, distribuidos en un diseño completamente aleatorizado con tres niveles de fNDF (100, 190 y 290 g/kg) y cinco niveles de NFC (350, 400, 450, 500 y 550 g/kg). El experimento se realizó in vitro. Se utilizaron dos cabras fistuladas en rumen como donantes de líquido ruminal. Resultados: La relacion entre fNDF y NFC afectó todos los parámetros ruminales estudiados (p<0,05). El aumento de los niveles de NFC en dietas con 100 y 290 g/kg de fNDF resultó en aumento lineal (p<0,05) de la concentración de amoníaco después de 48 h de fermentación. No hubo ajuste de modelos lineales (p>0,05) para valores de pH. Los ácidos grasos volátiles totales y sus proporciones molares individuales se afectaron (p<0,05) en todos los niveles de fNDF y NFC. La digestibilidad de NDF no fue afectada (p>0,05) por los niveles de fNDF ni NFC, con excepción de las dietas con 290 g/kg fNDF, que se ajustaron a un modelo cuadrático (p<0,05). Conclusión: La relación entre las concentraciones de fNDF y NFC afecta los productos finales de fermentación y la digestibilidad in vitro de NDF. Los niveles de NFC juegan un papel más consistente que fNDF en el ecosistema microbiano ruminal de la cabra durante la fermentación in vitro.

Resumo Antecedentes: Embora exista um compreensível entendimento do papel que a fibra dietética desempenha como nutriente e sua função durante a digestão em bovinos, o papel da digestão das fibras em caprinos não recebeu atenção semelhante. Objetivo: Avaliar os efeitos de diferentes relações da fibra em detergente neutro advindo de forragem (fNDF) e carboidratos não-fibrosos (NFC) sobre produtos da fermentação ruminal e digestibilidade in vitro da fibra em detergente neutro (NDF) em caprinos. Métodos: Utilizou-se um esquema fatorial de 3 × 5 distribuídos em um delineamento inteiramente casualizado com três níveis de fNDF (100, 190 e 290 g/kg) e cinco níveis de NFC (350, 400, 450, 500 e 550 g/kg). O experimento foi realizado in vitro. Duas cabras fistuladas no rúmen foram utilizadas como doadoras de líquido ruminal. Resultados: As relações entre fNDF e NFC impactaram todos os parâmetros ruminais estudados (p<0,05). O aumento dos níveis de NFC em dietas contendo 100 e 290 g/kg de fNDF resultou em um aumento linear (p<0,05) na concentração de amônia após 48 h de fermentação. Não houve ajuste de modelos lineares (p>0,05) para valores de pH. Os ácidos graxos voláteis totais e suas proporções molares individuais foram afetados (p<0,05) em todos os níveis de fNDF e NFC. A digestibilidade NDF não foi afetada (p>0,05) pelos níveis de fNDF e NFC, com exceção de dietas experimentais contendo 290 g/kg fNDF, que foram ajustadas a um modelo quadrático (p<0,05). Conclusão: A relação entre as concentrações de fNDF e NFC afeta os produtos finais de fermentação e a digestibilidade in vitro de NDF de dietas experimentais. Os níveis de NFC desempenham um papel mais consistente do que o fNDF no ecossistema microbiano ruminal de cabras durante a fermentação in vitro.

Invited review: Current perspectives on eating and rumination activity in dairy cows.

Many early studies laid the foundation for our understanding of the mechanics of chewing, the physiological role of chewing for the cow, and how chewing behavior is affected by dietary characteristics. However, the dairy cow has changed significantly over the past decades, as have the types of diets fed and the production systems used. The plethora of literature published in recent years provides new insights on eating and ruminating activity of dairy cows. Lactating dairy cows spend about 4.5 h/d eating (range: 2.4-8.5 h/d) and 7 h/d ruminating (range: 2.5-10.5 h/d), with a maximum total chewing time of 16 h/d. Chewing time is affected by many factors, most importantly whether access to feed is restricted, intake of neutral detergent fiber from forages, and mean particle size of the diet. Feed restriction and long particles (≥19 mm) have a greater effect on eating time, whereas intake of forage neutral detergent fiber and medium particles (4-19 mm) affects rumination time. It is well entrenched in the literature that promoting chewing increases salivary secretion of dairy cows, which helps reduce the risk of acidosis. However, the net effect of a change in chewing time on rumen buffing is likely rather small; therefore, acidosis prevention strategies need to be broad. Damage to plant tissues during mastication creates sites that provide access to fungi, adhesion of bacteria, and formation of biofilms that progressively degrade carbohydrates. Rumination and eating are the main ways in which feed is reduced in particle size. Contractions of the rumen increase during eating and ruminating activity and help move small particles to the escapable pool and into the omasum. Use of recently developed low-cost sensors that monitor chewing activity of dairy cows in commercial facilities can provide information that is helpful in management decisions, especially when combined with other criteria. Although accuracy and precision can be somewhat variable depending on sensor and conditions of use, relative changes in cow behavior, such as a marked decrease in rumination time of a cow or sustained low rumination time compared with a contemporary group of cows, can be used to help detect estrus, parturition, and some illnesses. This review provides a comprehensive understanding of the dietary, animal, and management factors that affect eating and ruminating behavior in dairy cows and presents an overview of the physiological importance of chewing with emphasis on recent developments and practical implications for feeding and managing the modern housed dairy cow.

Invited review: Practical feeding management recommendations to mitigate the risk of subacute ruminal acidosis in dairy cattle.

Rumen health is of vital importance in ensuring healthy and efficient dairy cattle production. Current feeding programs for cattle recommend concentrate-rich diets to meet the high nutritional needs of cows during lactation and enhance cost-efficiency. These diets, however, can impair rumen health. The term "subacute ruminal acidosis" (SARA) is often used as a synonym for poor rumen health. In this review, we first describe the physiological demands of cattle for dietary physically effective fiber. We also provide background information on the importance of enhancing salivary secretions and short-chain fatty acid absorption across the stratified squamous epithelium of the rumen; thus, preventing the disruption of the ruminal acid-base balance, a process that paves the way for acidification of the rumen. On-farm evaluation of dietary fiber adequacy is challenging for both nutritionists and veterinarians; therefore, this review provides practical recommendations on how to evaluate the physical effectiveness of the diet based on differences in particle size distribution, fiber content, and the type of concentrate fed, both when the latter is part of total mixed ration and when it is supplemented in partial mixed rations. Besides considering the absolute amount of physically effective fiber and starch types in the diet, we highlight the role of several feeding management factors that affect rumen health and should be considered to control and mitigate SARA. Most importantly, transitional feeding to ensure gradual adaptation of the ruminal epithelium and microbiota; monitoring and careful management of particle size distribution; controlling feed sorting, meal size, and meal frequency; and paying special attention to primiparous cows are some of the feeding management tools that can help in sustaining rumen health in high-producing dairy herds. Supplementation of feed additives including yeast products, phytogenic compounds, and buffers may help attenuate SARA, especially during stress periods when the risk of a deficiency of physically effective fiber in the diet is high, such as during early lactation. However, the usage of feed additives cannot fully compensate for suboptimal feeding management.

Levels of neutral detergent fiber in diets with forage palm for dairy goats / Fibra em detergente neutro em dietas com palma forrageira para cabras leiteiras

This study aimed to evaluate the amount of fiber in the diet that is able to promote better use of nutrients in the diet of dairy goats when forage palm is the main source of roughage. Fifteen Alpine dairy goats were distributed in a 5 × 5 triple Latin square containing five treatments and five periods, and each treatment contained. We tested five diets composed of different contents of neutral detergent fiber from Tifton hay (NDFf) in the dry matter of rations containing forage palm: D1: 11.98%; D2: 18.31%; D3: 23.68%; D4: 28.76% and D5: 32.12% NDFf. The intake of dry matter, crude protein, neutral detergent fiber, non-fiber carbohydrates and ether extract decreased linearly with the increase in NDFf content. There was a linear increase of milk production and milk protein with increasing dietary NDFf. The fat, dry extract, protein, pH and acidity of the evaluated milk were not affected by increasing the levels of NDFf in the diet. In situations where dairy goats are fed forage palm and other types of forage are limited, 11.98% NDF from forage other than palm can be used as an effective source of NDF.(AU)

Objetivou-se, com este trabalho, avaliar a quantidade de fibra na dieta que é capaz de promover melhor uso de nutrientes na dieta de cabras leiteiras quando a palma forrageira é a principal fonte de forragem. Quinze cabras leiteiras alpinas foram distribuídas em um quadrado latino triplo 5 × 5 contendo cinco tratamentos e cinco períodos. Testaram-se cinco dietas compostas por diferentes teores de fibra em detergente neutro de feno de tifton (FDNf) na matéria seca de rações contendo palma forrageira: D1: 11,98%; D2: 18,31%; D3: 23,68%; D4: 28,76% e D5: 32,12% de FDNf. A ingestão de matéria seca, proteína bruta, fibra em detergente neutro, carboidratos não fibrosos e extrato etéreo diminuiu linearmente com o aumento do conteúdo de FDNf. Houve um aumento linear da produção de leite e da proteína do leite com o aumento da FDNf dietética. A gordura, a lactose, o extrato seco, o pH e a acidez do leite não foram afetados pelo aumento dos níveis de FDNf na dieta. Em situações em que as cabras leiteiras são alimentadas com palma forrageira e outros tipos de forragem são limitados, 11,98% de FDN de forragem diferente da palma podem ser usados como fonte efetiva de fibra.(AU)