Effects of forage quality and particle size on feed intake and ruminoreticulum content of goats

The aim was to evaluate the effect of particle size and hay quality on feed intake, granulometric profile, and composition of the ruminoreticulum content in goats. We used 54 Alpine bucks in a completely randomized design with a factorial arrangement of 3 × 3. Treatments were a combination of Bermuda grass hay (Cynodon dactylon) with three quality levels: high (35 days), medium (50 days), and low (65 d) harvested at regrowth times. Were evaluated three particle sizes: small (16% ≥4.76 mm), medium (48% ≥4.76 mm), and large (75% ≥4.76 mm), which accounted for 66%, 75%, and 94% of physically effective fiber, respectively. Samples of offered diet, intake, and ruminoreticulum content were used to generate the granulometric profile. The offered diet, intake, and ruminoreticulum content presented different granulometric profiles regarding hay quality and particle size. Dry matter intake (DMI) and neutral detergent fiber intake (NDFI) increased (P < 0.05) when low-quality hay and large particles were offered. However, when particle size in low-quality hay was reduced, DMI and NDF decreased (P < 0.05). When analyzing the ruminoreticulum content (DM, NDF, peNDF, and indigestible DM), we did not observe any effect (P > 0.05) of hay quality or particle size on the variables. Thus, reducing hay quality and increasing particle size increase dry matter and fiber intake, presenting an interaction between forage quality and particle size. Forage quality and particle size promote intense selective behavior and chewing, which leads to a homogeneous content of particle profile in ruminoreticulum and a uniform average retention time.

Dietary Neutral Detergent Fiber Levels Impacting Dairy Cows' Feeding Behavior, Rumen Fermentation, and Production Performance during the Period of Peak-Lactation

This study investigated the impact of dietary neutral detergent fiber (NDF) levels (25.49%, 28.65%, 31.66%, and 34.65%, respectively) on the feeding behavior, rumen fermentation, cellulolytic bacteria, and production performance of dairy cows during peak lactation. A feeding experiment was conducted using four fistulated Holstein dairy cows (600 ± 25 kg) with days in milk (50 ± 15 days), employing a 4 × 4 Latin square design to assign the cows to four groups. The results demonstrated that increasing NDF levels in the diet had the following effects: (1) A linear decrease in dry matter intake (DMI), NDF intake, and physically effective NDF8.0 (peNDF8.0) intake; a linear increase in the average time spent eating and ruminating, as well as the time spent eating and ruminating per kilogram of dry matter (DM); a quadratic response in the time spent ruminating per kilogram of NDF and peNDF8.0. (2) A linear increase in average pH value, acetate concentration, and the proportions of Fibrobacter succinogenes and Ruminococcus flavefaciens among total bacteria; a linear decrease in ammonia nitrogen (NH3-N) concentration, microbial crude protein (MCP), total volatile fatty acid (TVFA), propionate, butyrate, and lactate. (3) A linear decrease in milk yield, milk protein percentage, and nitrogen efficiency of dairy cows; a linear increase in milk fat percentage and milk urea nitrogen (MUN) concentration. Based on the combined results, it was found that diets with 25% and 34% NDF had detrimental effects on the feeding behavior, rumen fermentation, and production performance of dairy cows. However, the diet with 28% NDF showed superior outcomes in production performance compared to the one with 31% NDF. Therefore, it is strongly recommended to include a diet containing 28% NDF during the critical peak lactation period for dairy cows.

Sodium Propionate Relieves LPS-Induced Inflammation by Suppressing the NF-ĸB and MAPK Signaling Pathways in Rumen Epithelial Cells of Holstein Cows

Subacute ruminal acidosis (SARA) is a prevalent disease in intensive dairy farming, and the rumen environment of diseased cows acidifies, leading to the rupture of gram-negative bacteria to release lipopolysaccharide (LPS). LPS can cause rumentitis and other complications, such as liver abscess, mastitis and laminitis. Propionate, commonly used in the dairy industry as a feed additive, has anti-inflammatory effects, but its mechanism is unclear. This study aims to investigate whether sodium propionate (SP) reduces LPS-induced inflammation in rumen epithelial cells (RECs) and the underlying mechanism. RECs were stimulated with different time (0, 1, 3, 6, 9, 18 h) and different concentrations of LPS (0, 1, 5, 10 μg/mL) to establish an inflammation model. Then, RECs were treated with SP (15, 25, 35 mM) or 10 μM PDTC in advance and stimulated by LPS for the assessment. The results showed that LPS (6h and 10 μg/mL) could stimulate the phosphorylation of NF-κB p65, IκB, JNK, ERK and p38 MAPK through TLR4, and increase the release of TNF-α, IL-1β and IL-6. SP (35 mM) can reduce the expression of cytokines by effectively inhibiting the NF-κB and MAPK inflammatory pathways. This study confirmed that SP inhibited LPS-induced inflammatory responses through NF-κB and MAPK in RECs, providing potential therapeutic targets and drugs for the prevention and treatment of SARA.

Relationships among total mixed ration nutritional components and reproductive performance in high-producing dairy herds

The main objective of the present study was to determine whether composition of total mixed ration influences reproductive performance in high-producing commercial dairy farms. Dairy producers and nutritional consultants from 48 dairy farms located in Wisconsin agreed to provide reproductive data and dietary information on high milk production pens during the main breeding period for the previous 12 mo. Dietary components (percentage of dry matter) were crude protein (CP), rumen degradable (RDP) and undegradable (RUP) protein, neutral detergent fiber (NDF), nonfiber carbohydrates (NFC), starch, and fat. Reproductive data were service rate (SR), overall pregnancy per artificial insemination (P/AI) and P/AI at the first service, 21-d pregnancy rate (PR), days open, and percentage of cows pregnant by 150 d in milk (PREG150). Participating herds had lactating Holstein cows (range = 143 to 2,717) housed in freestall facilities. Statistical analyses were performed with CORR and GLIMMIX of SAS (SAS Institute Inc.). Daily average milk production of herds was 38.9 ± 0.60 kg/d (30.0 to 50.4 kg/d). Overall SR was 58.5% (39-73) and P/AI was 36.1% (22-49). Overall 21-d PR was 20.3% (10-42%). Correlation between SR and PR was 0.59, whereas correlation of overall P/AI and P/AI at first service with PR were both 0.72. Similarly, for PREG150, correlation with overall P/AI (0.63) and P/AI at first service (0.66) were greater than with SR (0.48). There was large variation in diet composition, with CP varying from 16.0 to 18.7%, NDF from 24.9 to 35.1%, NFC from 31.7 to 46.6%, starch from 20.1 to 30.8%, and fat from 3.1 to 6.7%. Overall, there were no detectable associations of CP, RDP, and RUP with reproductive measures. The strongest relationship was a decrease in reproductive performance with increasing dietary NFC including overall P/AI (-0.48), P/AI at first service (-0.51), and PREG150 (-0.33). Starch also had a negative relationship with P/AI at first service (-0.35). Conversely, greater NDF was positively associated with P/AI at first service (0.34). Fat content was also positively associated with P/AI at first service (0.34). When NFC was divided in tertiles (<40, 40 to 42.2, and >42.2% NFC), the highest tertile had lower overall P/AI (39 vs. 36 vs. 31%), P/AI at first service (43 vs. 40 vs. 33%), and PREG150 (54 vs. 53 vs. 47%). In conclusion, farms with greater dietary NFC may have compromised reproductive performance. Correspondingly, herds with greater NDF content may achieve high milk production with potentially positive associations with reproduction. Other relationships of dietary components on reproduction were not as obvious in this herd-level analysis.

Effects of extrinsic factors on some rumination patterns: A review

The rumen and its activity, rumination, are the characterizing traits of the suborder Ruminantia, and it is accompanied by related feeding habits and consequent animal behavior. Several extrinsic (not related to the animal itself) factors affect rumination behavior; most are reflected in rumination timing (considering overall daily duration as well as circadian differences in rumination patterns): age, environmental factors, and diet. For these reasons, great efforts have been sustained at the research level for monitoring rumination patterns. Currently, some research outcomes are applied at the farm level; others are still at the experimental level. All of these efforts are finalized mainly for the use of rumination pattern recording as an effective prediction tool for the early detection of health and welfare problems, both in a single head and at the herd level. Moreover, knowledge of the effects of extrinsic factors on rumination physiology represents a great challenge for improving the efficiency of ruminant livestock management, from the diet to the housing system, from parasites to heat stress. The present review deals mainly with the worldwide raised ruminant species.

Effects of pigeon pea leaves and concentrate mixture on feed intake, milk yield, and composition of crossbred dairy cows fed native pasture hay

Protein supplements are expensive and not easily accessible under small-scale livestock production systems in Ethiopia and other developing countries, which necessitates investigating the alternative protein sources for cost-effective livestock production. Pigeon pea (Cajanus cajan L. Millsp) leaves (PPLs) are rich in protein and are well-suited for feeding small ruminants; however, the effect of inclusion of PPL in the concentrate mixture (CM) on the performance of dairy cows was not well documented. This experiment was conducted to evaluate the effect of supplementation of PPL and CM to native pasture hay-based rations on feed intake, milk yield and composition, and blood metabolites of crossbred dairy cows (Holstein × Zebu). A 4 × 4 Latin square design with three replications, balanced for carryover effects, was used for this study. The treatments included native pasture hay provided ad libitum as a basal diet, supplemented with a CM alone (T1), the inclusion of 10% of PPL in the CM (T2), 20% PPL in the CM (T3), or 30% PPL in the CM (T4). Supplements were isocaloric and isonitrogenous. Total DM intake (hay + supplement intake) was similar (P > 0.05) among treatments. Hay intake was greater (P = 0.05) for T1 and T2 than for T4, while supplement intake was the least for T1 (P < 0.05). The treatment groups T2, T3, and T4, where PPL was included, had similar (P > 0.05) supplement intake. Feed intake, milk yield and composition, feed conversion efficiency, body condition score, serum total protein, albumin, globulin, glucose, triglyceride, urea N, creatinine, and cholesterol were similar (P > 0.05) among treatments. The inclusion of up to 30% of PPL in the CM resulted in a comparable performance of crossbred dairy cows as supplementation with CM under the conditions of the current experiment. Therefore, further study is required to evaluate the effect of the inclusion of a higher level of PPL in the concentrate mixture on the performance of lactating crossbred dairy cows.

Comparisons of Ramie and Corn Stover Silages: Effects on Chewing Activity, Rumen Fermentation, Microbiota and Methane Emissions in Goats

The study aimed to investigate the nutritional value of ramie (Boehmeria nivea) silage, and its consequences for chewing activity, rumen fermentation, and enteric methane (CH4) emissions in goats, by comparing it with corn stover (CS) silage. An in vitro ruminal experiment was firstly performed to investigate the substrate degradation and fermentation of CS and ramie silage. The ramie silage diet was formulated by replacing 60% of CS silage with ramie silage (dry matter (DM) basis). Eight female Xiangdong Black goats (a local breed in Southern China, 1 to 1.2 years of age) with BW of 21.0 ± 1.05 kg were used for this experiment and were randomly assigned to either one of the two dietary treatments in a cross-over design. The ramie silage had higher crude protein (CP) and ash content and lower hemicellulose content, together with decreased (p < 0.05) nutrient degradation and methane production and increased (p < 0.05) acetate molar percentage and acetate to propionate ratio through in vitro ruminal fermentation. Feeding the ramie silage diet did not alter feed intake (p > 0.05), decreased (p < 0.05) nutrient digestibility, and increased (p < 0.05) chewing activity and rumination activity, with reductions (p < 0.05) in eating activity and idle activity. Although feeding the ramie silage diet caused a greater (p < 0.05) molar percentage of acetate and lower molar percentage of propionate, it decreased the rumen-dissolved CH4 concentration and enteric CH4 emissions (p < 0.05). Feeding the ramie silage diet did not alter (p > 0.05) the population of bacteria, protozoa, and fungi; it increased the 16S rRNA gene copies of Ruminococcus flavefaciens (p < 0.05). Further 16SrRNA gene amplicon analysis indicated a distinct bacterial composition between the two treatments (p < 0.05). Feeding the ramie silage diet led to a lower abundance of genera Lawsonibacter, Sedimentibacter, Saccharofermentans, Sediminibacterium, and Bifidobacterium (p < 0.05). Ramie can be an alternative forage resource to stimulate chewing activity and reduce CH4 emissions in ruminants.

The Role of Rumen Microbiota and Its Metabolites in Subacute Ruminal Acidosis (SARA)-Induced Inflammatory Diseases of Ruminants

Subacute ruminal acidosis (SARA) is a common metabolic disease in ruminants. In the early stage of SARA, ruminants do not exhibit obvious clinical symptoms. However, SARA often leads to local inflammatory diseases such as laminitis, mastitis, endometritis and hepatitis. The mechanism by which SARA leads to inflammatory diseases is largely unknown. The gut microbiota is the totality of bacteria, viruses and fungi inhabiting the gastrointestinal tract. Studies have found that the gut microbiota is not only crucial to gastrointestinal health but also involved in a variety of disease processes, including metabolic diseases, autoimmune diseases, tumors and inflammatory diseases. Studies have shown that intestinal bacteria and their metabolites can migrate to extraintestinal distal organs, such as the lung, liver and brain, through endogenous pathways, leading to related diseases. Combined with the literature, we believe that the dysbiosis of the rumen microbiota, the destruction of the rumen barrier and the dysbiosis of liver function in the pathogenesis of SARA lead to the entry of rumen bacteria and/or metabolites into the body through blood or lymphatic circulation and place the body in the “chronic low-grade” inflammatory state. Meanwhile, rumen bacteria and/or their metabolites can also migrate to the mammary gland, uterus and other organs, leading to the occurrence of related inflammatory diseases. The aim of this review is to describe the mechanism by which SARA causes inflammatory diseases to obtain a more comprehensive and profound understanding of SARA and its related inflammatory diseases. Meanwhile, it is also of great significance for the joint prevention and control of diseases.

Effects of changes in diet energy density and milking frequency and a single injection of cabergoline at dry-off on feeding behavior and rumination time in dairy cows

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Diluting the lactation diet with straw induced feeding behavior changes.

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Behavioral effects of gradual milking cessation were unclear.

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Cabergoline induced a reduction in feeding behavior lasting approximately 24 h.

Dry-off is a typical management practice, but research on the effects of dry-off on feeding behavior in high-yielding cows is limited. The present study investigated the effects of 2 diet energy densities: lactation diet (normal energy density, NORM) versus a lactation diet diluted with 30% straw (reduced energy density, REDU), both offered ad libitum, and 2 daily milking frequencies (2× vs. 1×) during the 7 d before dry-off day (d 0), and the effects of an injection of either a dopamine agonist [cabergoline (CAB); Velactis, Ceva Santé Animale; labeled for use only with abrupt dry-off; i.e., no reduction in feeding level or milking frequency before the last milking] or saline (SAL) following the last milking on d 0 (2 × 2 × 2 factorial arrangement), on automatically monitored feeding behavior and rumination time in 119 clinically healthy, loose-housed, pregnant, lactating Holstein cows during the week before and after d 0. From d 0, all cows were fed the same dry-cow diet ad libitum. Data were analyzed in R using mixed-effects models. Over the days before d 0, REDU cows spent 30% more time feeding at a 50% lower feeding rate, visited both assigned and unassigned feed bins more frequently, and spent more time ruminating than NORM cows. No clear behavioral effects of reduced milking frequency were found. Within 24 h following injection, CAB cows spent approximately 40% less time feeding at a lower feeding rate, visited their feed bin 28% less often, and spent 40% less time ruminating than SAL cows, irrespective of treatment before dry-off. The current study demonstrates that reducing diet energy density for 1 wk before dry-off led to clear behavioral changes in high-yielding cows. Administering CAB after the last milking induced decreased feeding behavior lasting approximately 24 h, indicating collateral effects other than reduced prolactin secretion.

Effects of sucrose and lactose as partial replacement to corn in lactating dairy cow diets. A review

Carbohydrates are one of the three macronutrients that provides energy in diets and are classified by their structures. Starch is a nonstructural carbohydrate and polysaccharide made of glucose monomers used for storage in plant cells. When starch makes up greater than 30% of the DM in diets there can be adverse effects on NDF digestibility due to decreases in ruminal pH. Sugars are water soluble carbohydrates that consist of monosaccharide and disaccharide units. Sugars ferment faster than starch because microorganisms in the rumen can ferment carbohydrates at different rates depending on their structure; however, this has not been shown to have negative effects on the ruminal pH. Sources of sugars such as molasses (sucrose) or whey (lactose) can be included in the diet as a partial replacement for starch in dairy cow diets. The purpose of replacing starch with sugars in a diet would be to add differing sources of carbohydrates in the diet to allow for continual fermentation of carbohydrates by the microorganisms in the rumen. It has been seen in studies and previous literature that the partial replacement of starch with sugars has the potential to maintain the ruminal environment and milk yield and composition in dairy cows without reducing NDF digestibility. The objective of this review is to evaluate the effects of partially replacing starch with sugars in dairy diets and its implication on ruminal fermentation, nutrient utilization, milk production, and feeding replacement strategy.

Characteristics of various fibrolytic isozyme activities in the rumen microbial communities of Japanese Black and Holstein Friesian cattle under different conditions

Rumen microorganisms produce various fibrolytic enzymes and degrade lignocellulosic materials into nutrient sources for ruminants; therefore, the characterization of fibrolytic enzymes contributing to the polysaccharide degradation in the rumen microbiota is important for efficient animal production. This study characterized the fibrolytic isozyme activities of a rumen microbiota from four groups of housed cattle (1, breeding Japanese Black; 2, feedlot Japanese Black; 3, lactating Holstein Friesian; 4, dry Holstein Friesian). Rumen fluids in all cattle groups showed similar concentrations of total volatile fatty acids and reducing sugars, whereas acetic acid contents and pH were different among them. Predominant genera were commonly detected in all cattle, although the bacterial compositions were different among cattle groups. Zymograms of whole proteins in rumen fluids showed endoglucanase activities at 55 and 57 kDa and xylanase activity at 44 kDa in all cattle. Meanwhile, several fibrolytic isozyme activities differed among cattle groups and individuals. Treponema, Succinivibrio, Anaeroplasma, Succiniclasticum, Ruminococcus, and Butyrivibrio showed positive correlations with fibrolytic isozyme activities. Further, endoglucanase activity at 68 kDa was positively correlated with pH. This study suggests the characteristics of fibrolytic isozyme activities and their correlations with the rumen microbiota.

Rumen Fermentation, Digestive Enzyme Activity, and Bacteria Composition between Pre-Weaning and Post-Weaning Dairy Calves

Simple Summary

Weaning is very important for young ruminants. At this stage, calves’ main source of nutrients is transferred from milk into solid feed, such as starter and roughage. At the same time, the rumen function of calves undergoes tremendous changes, such as bacteria, which are the main players in rumen function. Our research found that the rumen bacteria network of post-weaning calves was more complex. The fermentation end products, such as acetate, propionate, and butyrate, were higher in the post-weaning calves than the pre-weaning group. However, digestive enzymes such as protease, carboxymethyl cellulase, cellobiohydrolase, and glucosidase were lower in the post-weaning calves than the pre-weaning calves. These findings provided useful information for reference regarding the feeding management of calves.

Abstract

To better understand the transition of rumen function during the weaning period in dairy calves, sixteen Holstein dairy calves were selected and divided into two groups: pre-weaning (age = 56 ± 7 day, n = 8) and post-weaning (age = 80 ± 6 day, n = 8). The rumen fluid was obtained by an oral gastric tube. The rumen fermentation profile, enzyme activity, bacteria composition, and their inter-relationship were investigated. The results indicated that the post-weaning calves had a higher rumen acetate, propionate, butyrate, and microbial crude protein (MCP) than the pre-weaning calves (p < 0.05). The rumen pH in the post-weaning calves was lower than the pre-weaning calves (p < 0.05). The protease, carboxymethyl cellulase, cellobiohydrolase, and glucosidase in the post-weaning calves had a lower trend than the pre-weaning calves (0.05 < p < 0.1). There was no difference in α and β diversity between the two groups. Linear discriminant analysis showed that the phylum of Fibrobacteres in the post-weaning group was higher than the pre-weaning group. At the genus level, Shuttleworthia, Rikenellaceae, Fibrobacter, and Syntrophococcus could be worked as the unique bacteria in the post-weaning group. The rumen bacteria network node degree in the post-weaning group was higher than the pre-weaning group (16.54 vs. 9.5). The Shuttleworthia genus was highly positively correlated with MCP, propionate, total volatile fatty acid, glucosidase, acetate, and butyrate (r > 0.65, and p < 0.01). Our study provided new information about the rumen enzyme activity and its relationship with bacteria, which help us to better understand the effects of weaning on the rumen function.

Effects of Age, Diet CP, NDF, EE, and Starch on the Rumen Bacteria Community and Function in Dairy Cattle

To understand the effects of diet and age on the rumen bacterial community and function, forty-eight dairy cattle at 1.5 (M1.5), 6 (M6), 9 (M9), 18 (M18), 23 (M23), and 27 (M27) months old were selected. Rumen fermentation profile, enzyme activity, and bacteria community in rumen fluid were measured. The acetate to propionate ratio (A/P) at M9, M18, and M23 was higher than other ages, and M6 was the lowest (p < 0.05). The total volatile fatty acid (TVFA) at M23 and M27 was higher than at other ages (p < 0.05). The urease at M18 was lower than at M1.5, M6, and M9, and the xylanase at M18 was higher than at M1.5, M23, and M27 (p < 0.05). Thirty-three bacteria were identified as biomarkers of the different groups based on the linear discriminant analysis (LDA) when the LDA score >4. The variation partitioning approach analysis showed that the age and diet had a 7.98 and 32.49% contribution to the rumen bacteria community variation, respectively. The richness of Succinivibrionaceae_UCG-002 and Fibrobacter were positive correlated with age (r > 0.60, p < 0.01) and positively correlated with TVFA and acetate (r > 0.50, p < 0.01). The Lachnospiraceae_AC2044_group, Pseudobutyrivibrio, and Saccharofermentans has a positive correlation (r > 0.80, p < 0.05) with diet fiber and a negative correlation (r < −0.80, p < 0.05) with diet protein and starch, which were also positively correlated with the acetate and A/P (r > 0.50, p < 0.01). The genera of Lachnospiraceae_AC2044_group, Pseudobutyrivibrio, and Saccharofermentans could be worked as the target bacteria to modulate the rumen fermentation by diet; meanwhile, the high age correlated bacteria such as Succinivibrionaceae_UCG-002 and Fibrobacter also should be considered when shaping the rumen function.

A comparative analysis of rumen pH, milk production characteristics, and blood metabolism of Holstein cattle according to the forage ratio for the establishment of objective indicators of the animal welfare certification standard

Objective

This study was conducted to present an objective index that can be quantified and statistically analyzed by comparing rumen pH, ruminating time, milk yield, milk quality, and blood components among cows from farms with forage ratios of 90% or more of grass feed and farms that routinely manage more than 40% of the forage ratio, in consideration welfare of Holstein cow welfare.

Methods

Data on rumen pH, rumination time, milk yield, milk fat ratio, milk protein ratio, and blood metabolism were collected from 12 heads from a welfare farm (forage rate 88.5%) and 13 heads from a conventional (forage rate 34.5%) three days in October 2019.

Results

The rumination time was significantly longer in cattle on the welfare farm than on the conventional farm (p<0.01), but ruminal pH fluctuation was significantly greater in the cattle on conventional farm than the welfare farm (p<0.01). Conventional farms with a high ratio of concentrated feed produced a higher average daily milk yield than welfare farms, but milk fat and milk production efficiency (milk fat and milk protein corrected milk/total digestible nutrients) was higher in cattle on welfare farms. Blood test results showed a normal range for both farm types, but concentrations of total cholesterol and NEFA were significantly higher in cows from conventional farms with a high milk yield (p<0.01).

Conclusion

The results of this study confirmed that cows on the animal welfare farm with a high percentage of grass feed had better rumen pH, milk production efficiency, and various blood metabolism parameters compared to those on the conventional farm.

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.

Short-term screening of multiple phytogenic compounds for their potential to modulate chewing behavior, ruminal fermentation profile, and pH in cattle fed grain-rich diets

In cattle, proper rumen functioning and digestion are intimately linked to chewing behavior. Yet, high grain feeding impairs chewing activity, increasing the risk of subacute ruminal acidosis and dysfermentation. This study aimed to screen 9 different phytogenic compounds for their potential to modulate chewing activity, meal size, rumino-reticular short-chain fatty acids (SCFA), and pH during consumption in a first daily meal and shortly thereafter in cattle fed a grain-rich diet. Treatments were control (total mixed ration without phytogenic) or addition of a phytogenic compound at a low or high dose. Phytogenic compounds and doses (all in mg/kg) were angelica root (6.6 and 66), capsaicin (10 and 100), gentian root (6.6 and 66), garlic oil (0.3 and 3), ginger extract (40 and 400), L-menthol (6.7 and 67), mint oil (15.3 and 153), thyme oil (9.4 and 94), and thymol (5 and 50), for the low and high groups, respectively. Before the start of the screening experiment, cows were fed to reach subacute ruminal acidosis conditions, confirmed with the time of ruminal pH <5.8 being 655 ± 148.2 min/d. During the screening experiment, the treatments were offered in a controlled meal (2.5 kg of DM for 4 h) as part of the daily diet with 65% concentrate. Each treatment was tested in 4 of the 9 cannulated Holstein cows using an incomplete Latin square design. Ruminal and reticular fluids were sampled before and after each treatment, and data collected before the meal were used as covariates. Chewing and ruminal pH were monitored during the treatment, followed by 2 h of complete feed restriction, and then 4 h of ad libitum feed intake without phytogenic. Data showed that supplementation of angelica root tended to linearly increase rumination time immediately after the first meal when feed was restricted (27.3, 41.9, and 42.6 ± 5.99 min for control, low and high groups, respectively). Capsaicin increased eating time (43.6, 49.4, and 66.4 ± 4.93 min) during consumption but did not affect ruminal total SCFA or mean ruminal pH. Garlic oil reduced the concentration of reticular total SCFA (75.7, 71.3, and 60.1 mM) and tended to decrease ruminal acetate-to-propionate ratio (2.50, 1.78, and 1.87 ± 0.177) with no effect on ruminal pH. The L-menthol affected reticular total SCFA quadratically (76.1, 64.9, and 81.0 ± 4.22%), and ruminal pH responded quadratically when feed was reintroduced ad libitum (6.0, 6.3, and 6.1 ± 0.07). Mint oil did not affect chewing or total SCFA during consumption, but the low dose increased ruminal pH (6.5, 6.7, and 6.5 ± 0.08). Thyme oil tended to lower the severity of ruminal acidosis. Overall, phytogenic compounds demonstrated distinct dose-dependent effects to beneficially influence chewing behavior, modulate fermentation, and mitigate ruminal acidosis in dairy cows under a high-grain challenge diet.

Development of a subacute ruminal acidosis risk score and its prediction using milk mid-infrared spectra in early-lactation cows

A routine monitoring for subacute ruminal acidosis (SARA) on the individual level could support the minimization of economic losses and the ensuring of animal welfare in dairy cows. The objectives of this study were (1) to develop a SARA risk score (SRS) by combining information from different data acquisition systems to generate an integrative indicator trait, (2) the investigation of associations of the SRS with feed analysis data, blood characteristics, performance data, and milk composition, including the fatty acid (FA) profile, (3) the development of a milk mid-infrared (MIR) spectra-based prediction equation for this novel reference trait SRS, and (4) its application to an external data set consisting of MIR data of test day records to investigate the association between the MIR-based predictions of the SRS and the milk FA profile. The primary data set, which was used for the objectives (1) to (3), consisted of data collected from 10 commercial farms with a total of 100 Holstein cows in early lactation. The data comprised barn climate parameters, pH and temperature logging from intrareticular measurement boluses, as well as jaw movement and locomotion behavior recordings of noseband-sensor halters and pedometers. Further sampling and data collection included feed samples, blood samples, milk performance, and milk samples, whereof the latter were used to get the milk MIR spectra and to estimate the main milk components, the milk FA profile, and the lactoferrin content. Because all measurements were characterized by different temporal resolutions, the data preparation consisted of an aggregation into values on a daily basis and merging it into one data set. For the development of the SRS, a total of 7 traits were selected, which were derived from measurements of pH and temperature in the reticulum, chewing behavior, and milk yield. After adjustment for fixed effects and standardization, these 7 traits were combined into the SRS using a linear combination and directional weights based on current knowledge derived from literature studies. The secondary data set was used for objective (4) and consisted of test day records of the entire herds, including performance data, milk MIR spectra and MIR-predicted FA. At farm level, it could be shown that diets with higher proportions of concentrated feed resulted in both lower daily mean pH and higher SRS values. On the individual level, an increased SRS could be associated with a modified FA profile (e.g., lower levels of short- and medium-chain FA, higher levels of C17:0, odd- and branched-chain FA). Furthermore, a milk MIR-based partial least squares regression model with a moderate predictability was established for the SRS. This work provides the basis for the development of routine SARA monitoring and demonstrates the high potential of milk composition-based assessment of the health status of lactating cows.

Effect of cattle breed and basal diet on digestibility, rumen bacterial communities, and eating and rumination activity

The objectives of this study were to compare ruminal total tract digestibility, bacterial communities, and eating and rumination activity between Holstein and Angus steers fed grain- or forage-based diets. Six Holstein steers (average body weight [BW] = 483 ± 23 kg) and six Angus steers (average BW = 507 ± 29 kg), previously fitted with rumen cannulae, were fed in a crossover design with a 2 × 2 factorial arrangement of four treatments: 1) Holsteins fed a grain-based diet, 2) Holsteins fed a forage-based diet, 3) Angus fed a grain-based diet, and 4) Angus fed a forage-based diet. Each period was 35 d with 26 d of diet adaptation and 9 d of sample collection. On days 1 and 2 of collection, feeding activity was recorded for 48 h. On day 3, rumen contents were sampled to measure ruminal pH at 0, 3, 6, 12, and 18 h after feeding. A portion of the strained ruminal fluid was subsampled at 0, 3, and 6 h for volatile fatty acids (VFA) analysis. Rumen contents were subsampled at 3 h for analysis of bacterial communities. From day 4 to 8, total fecal excretion, feed, and refusals samples were collected and analyzed for dry matter (DM), neutral detergent fiber (NDF), and starch. On days 8 and 9 (0 and 3 h post-feeding, respectively), total reticulorumen evacuation was conducted and contents were weighed. Data were analyzed using the MIXED procedures in SAS (v9.4 SAS Inst. Inc., Cary, NC). Repeated measures were used to analyze changes in ruminal pH and VFA over time. There were no interactions of diet × breed (P ≥ 0.07). While the main effects of diet were expected, unique to these data is the fact that bacterial diversity and richness were reduced (P < 0.01) in cattle fed grain-based diets. There was no main effect (P > 0.34) of breed on total tract DM, organic matter, and starch digestibility, but Angus cattle had greater (P = 0.01) NDF digestibility than Holsteins. The increased NDF digestibility may be associated with a numerical (P = 0.08) increased numbers of bacterial species in Angus steers compared with Holstein steers. Holstein steers also spent more time (P ≤ 0.05) ruminating than Angus steers. There was no effect (P > 0.80) of breed on reticulorumen content at feeding time; however, Holstein steers had greater (P = 0.04) reticulorumen content on a wet basis 3 h post-feeding. Although Holstein steers spent more time ruminating, Angus steers were better able to digest NDF when compared with Holsteins, regardless of basal diet, and this improvement may be related to changes in bacterial communities in the rumen or to rumination activity.

Modeling reticular and ventral ruminal pH of lactating dairy cows using ingestion and rumination behavior

The prevention and control of metabolic and digestive diseases is an enormous challenge in dairy farming. Subacute ruminal acidosis (SARA) is assumed to be the most severe feed-related disorder and it impairs both animal health and economic efficiency. Currently, ruminal pH as well as variables derived from the daily pH curve are the main indicators for SARA. The objective of this study was to explain the daily pH course in the ventral rumen and reticulum of dairy cows using ingestion pattern and rumination behavior data gathered by automated data recording systems. The data of 13 ruminally fistulated lactating cows were collected at the experimental station of the Friedrich-Loeffler-Institut (Brunswick, Germany). The data included continuous pH measurements, which were recorded simultaneously in the reticulum by pH-measuring boluses and in the ventral rumen by a separate data logger. In addition, rumination behavior was measured using jaw movement sensors, and feed and water intakes were recorded by transponder-assisted systems. Milk yield and body weight were determined during and after each milking, respectively. For statistical evaluation, the data were analyzed using time-series modeling with multiple linear mixed regressions. Before applying the developed mathematical statistical modeling, we performed a plausibility assessment to ensure data quality. The major part of the mathematical statistical modeling consisted of data preparation, where all variables were transformed into a uniform 1-min resolution. Signal transformations were used to model individual feed and water intakes as well as rumination behavior events over time. Our results indicated that diurnal pH curves of both the reticulum and ventral rumen could be predicted by the transformed feed and water intake rates. Rumination events were associated with a marginal temporal increase in pH. We observed that the pH of the ventral rumen was delayed by approximately 37 min compared with that of the reticulum, which was therefore considered in the modeling. With the models developed in this study, 67.0% of the variance of the reticular pH curves and 37.8% of the variance of the ruminal pH curves could be explained by fixed effects. We deduced that the diurnal pH course is, to a large extent, associated with the animal's individual feed intake and rumination behavior.

Effect of diet-induced negative energy balance on the feeding behavior of dairy cows

The objective of this study was to determine how feeding behavior of dairy cows is altered in response to diet-induced negative energy balance, and if this response varies depending on dietary particle size distribution. Multiparous Holstein cows (n = 30; days in milk = 59 ± 5; parity = 2.8 ± 0.19), producing 44.6 ± 1.2 kg/d of milk, were fed (on a dry matter basis) a lactating diet [net energy of lactation (NE_L) = 1.66 Mcal/kg; 68% forage, including 1.8% wheat straw] during a 2-wk baseline period. To induce negative energy balance, cows were then exposed for 3 wk to 1 of 2 diets formulated for a 20% reduction in energy available for milk (NE_L = 1.58 Mcal/kg; 73% forage, including 17.2% wheat straw). These diets were identical, only varying in straw chop length: (1) long straw diet (LS): straw chopped with a 10.2-cm screen, or (2) short straw diet (SS): straw chopped with a 2.54-cm screen. Cows consumed 25.6 ± 0.26 kg/d during the baseline period. Dry matter intake decreased on the experimental diets; dry matter intake was greater for the SS diet as compared with the LS diet (23.1 vs. 22.5 kg/d; standard error = 0.47). During the baseline period, cow serum nonesterified fatty acids (NEFA) and blood β-hydroxybutyrate averaged 0.27 ± 0.02 and 0.71 ± 0.05 mmol/L, respectively. During the experimental period, NEFA and β-hydroxybutyrate averaged 0.34 and 1.04 mmol/L, respectively, with a peak of NEFA (0.63 ± 0.06 mmol/L) occurring 4 d after dietary change. During baseline, cows produced 42.3 ± 0.33 kg/d of milk; milk yield was decreased for both SS cows and LS cows during the experimental period (SS = 39.0, LS = 37.8 kg/d; standard error = 0.67). On the experimental diets, cows spent more time eating (266.8 vs. 221.8 min/d), had longer meal lengths (46.9 vs. 37.5 min/meal), and consumed fewer meals (7.1 vs. 7.7 meals/d) compared with the baseline period. Within the experimental period, LS cows spent more time eating per day than SS cows (LS = 281.3, SS = 252.2 min/d). During the baseline period cows sorted against long particles (>19 mm), did not sort medium particles (8 to 19 mm), and sorted for short (4 to 8 mm) and fine (<4 mm) particles. Cows did not change sorting of long particles on the SS diet, but increased sorting against these on the LS diet. On the SS diet cows did not change their sorting of short and fine particles. On the LS diet cows increased sorting for short and fine particles. In the baseline period, no association was detected between feed sorting and serum NEFA concentration. During the experimental period, greater NEFA concentration was associated with greater sorting in favor of short particles for both the LS and SS diets. Furthermore, greater NEFA concentration was associated with greater sorting against the longest particles for both the LS and SS diets. No associations of blood and meal variables were detected during the experimental period. Overall, cows altered their feed sorting behavior in response to experiencing a diet-induced period of negative energy balance and the severity of negative energy balance was associated with the extent of that change in feed sorting.

Statistical modeling of ruminal pH parameters from dairy cows based on a meta-analysis

Adequate feeding of high-performance dairy cows is extremely important to avoid the digestive disorder subacute ruminal acidosis. Subacute ruminal acidosis is defined as a status with a below-average ruminal pH that does not cause direct clinical symptoms at the individual level but is relevant for animal welfare due to a higher risk of secondary health problems at the herd level. The main objective of this study was to apply meta-analytical methods in an exploratory approach to investigate the association between pH parameters of the ventral rumen with milk and diet parameters. Data from 32 studies using continuous pH measurement in the ventral rumen of lactating cows were included in the meta-analysis. Available information extracted from all studies was categorized into parameters associated with management, cow, diet, milk, and pH. The statistical analysis was divided into 4 sections. First, a multiple imputation procedure based on a principal component model was applied, since approximately 19% of the data set consisted of missing values due to heterogeneity in provided information between the studies included in the analysis. In a second step, all potential predictors for the pH parameters, including the daily mean pH, the time with a pH below 5.8, and the pH range, were examined for their prediction suitability using multi-level mixed effects meta-regression models. These analyses were performed on the raw and the imputed data. Because the results of both approaches were consistent, the imputing procedure was considered to be appropriate. Third, automated variable selection was applied to all 3 pH parameters separately for the predictor groups milk and diet using the imputed data set. Thereby, multi-model inference was used to estimate the relative importance of the selected variables. Finally, a functional relationship between the 3 pH parameters was established. The fat to protein ratio of milk, milk fat, and milk protein showed significant associations in meta-regression analysis for all 3 pH parameters when used as a single predictor. Out of the group of diet-specific variables, the acid detergent fiber, neutral detergent fiber, nonfiber carbohydrate, starch content, as well as the forage to concentrate ratio, showed the highest significance in the models. In particular, the multi-model inference showed that the protein, fat, and lactose content of the milk can best quantify the association to the daily mean pH and the time with a pH below 5.8 in a multiple regression model.

The relationship of body condition indicators with the level of plasma cocaine and amphetamine regulated transcript and energy metabolism indicators in dairy cows

The factors affecting the course of lactation and intensity of milk secretion include the condition and body weight, as well as chewing time. A little researched factor is also the cocaine and amphetamine regulated transcript (CART) which has been suggested to have an anorexigenic function. This study sought to examine the dependent indicators of condition and chewing time on daily milk yield assessment in the context of the concentration of CART, glucose and ß-hydroxybutyrate (BHB) in blood. Higher CART levels contributed to shorter chewing time (min/day), lower body condition and lower body weight. Blood glucose concentration showed a stronger correlation with body weight and condition than with blood BHB concentration. An important practical aspect of the results is the relationship shown between CART and chewing time and the potential relation between daily milk production and chewing time. Importantly, the animals with lower daily milk production had relatively the highest concentration CART. This may suggest that this neuropeptide is indirectly involved in milk production, especially by shortening the chewing time. The obtained results help to better explain the mechanisms involved in milk secretion and the process of rumination and digestion. More research is required, but they also show important functions of other examined neuropeptides.

Effects of forage source and particle size on chewing activity, ruminal pH, and saliva secretion in lactating Holstein cows

The present study investigated the effects of dietary forage source (quality) and particle size on chewing activity, saliva secretion, and ruminal pH. Twelve multiparous lactating Holstein cows, four of which were ruminally cannulated, were used in a replicated 4 × 4 Latin square experimental design with a 2 × 2 factorial arrangement of treatments. Cows fed wild-rye hay diets had longer daily eating times than cows fed oaten hay diets. Treatments had no effect on ruminating time; therefore, resting time varied inversely to eating time. Neither the rate nor the amount of saliva secretion while eating, ruminating, or resting was affected by diet, resulting in similar total daily saliva secretions across treatments (231 L/day). Total volatile fatty acids (VFAs) in the ruminal fluid from animals fed oaten hay diets were higher than those from animals fed wild-rye hay diets; further, VFAs increased with decreasing forage particle size (FPS). Consistent with elevated VFA concentrations, reducing FPS and including oaten hay in the diet decreased mean ruminal pH and increased the daily time of ruminal pH under 5.8. Results of this study suggest that forage source and particle size affect ruminal pH might be via variations in VFA production rather than increased salivary recycling of buffering substrates.

Silage review: Silage feeding management: Silage characteristics and dairy cow feeding behavior

Feeding environment and feed accessibility influence the dairy cow's response to the ration and forage composition. Fiber content, physical form, and fermentability influence feeding behavior, feed intake, and overall cow metabolic and lactational responses to forage. It is possible to vary eating time of lactating dairy cattle by over 1 h/d by changing dietary silage fiber content, digestibility, and particle size. Optimizing silage particle size is important because excessively long particles increase the necessary chewing to swallow a bolus of feed, thereby increasing eating time. Under competitive feeding situations, excessively coarse or lower fiber digestibility silages may limit DMI of lactating dairy cows due to eating time requirements that exceed available time at the feed bunk. Additionally, greater silage particle size, especially the particles retained on the 19-mm sieve using the Penn State Particle Separator, are most likely to be sorted. Silage starch content and fermentability may influence ruminal propionate production and thereby exert substantial control over meal patterns and feed consumption. Compared with silage fiber characteristics, relatively little research has assessed how silage starch content and fermentability interact with the feeding environment to influence dairy cow feeding behavior. Finally, voluminous literature exists on the potential effects that silage fermentation end products have on feeding behavior and feed intake. However, the specific mechanisms of how these end products influence behavior and intake are poorly understood in some cases. The compounds shown to have the greatest effect on feeding behavior are lactate, acetate, propionate, butyrate, ammonia-N, and amines. Any limitation in the feeding environment will likely accentuate the negative response to poor silage fermentation. In the future, to optimize feeding behavior and dry matter intake of silage-based diets fed to dairy cattle, we will need to consider the chemical and physical properties of silage, end products of silage fermentation, and the social and physical components of the feeding environment.

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.

Dairy cows fed on tropical legume forages: effects on milk yield, nutrients use efficiency and profitability

Two trials with multiparous dairy cows were conducted. Experiment 1 tested the effects of increasing forage proportion in the diet (500, 600, and 700 g/kg DM) when a mixed sorghum (Sorghum bicolor) and jackbean (Cannavalia ensiformis) silage was used as forage. Experiment 2 studied the substitution of sorghum silage and soybean meal by jackbean silage or fresh cowpea (Vigna unguiculata) forage in the diet. All diets were iso-energetic and iso-proteic. In each experiment, 30 cows were used and separated into three groups. In experiment 1, there were no differences in dry matter intake (DMI), milk yield (MY), or apparent total tract digestibility (aTTd) among the three diets, but milk fat content increased with increasing forage proportion, even though the similar neutral detergent fiber of all diets. Nitrogen use efficiency was highest in the diet containing 600 g forage/kg DM, and some evidence was observed for a better profitability with this forage proportion. In experiment 2, feeding legumes increased DMI despite no effects on aTTd. Milk yield increased in line with DMI, with a larger increase for the fresh cowpea. Nitrogen use efficiency and milk composition were not affected by the diets. The increased MY and lower feed costs increased the economic benefits when feeding legumes, particularly when feeding fresh cowpea. Feeding fresh cowpea or jackbean silage to dairy cows appears to be an alternative to soybean as protein source, ideally at a forage proportions of 600 g/kg DM, without altering milk yield and quality and increasing the farm profitability.

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.