Impact of nutrient restriction at dry-off on performance and metabolism

Thanks to improvements in genetics, nutrition, and management, modern dairy cows can still produce large amounts of milk at the end of lactation, with possible negative effects on health and welfare, particularly when milking is stopped abruptly. To limit yield at dry-off, strategies involving different types of dietary restriction have been used worldwide. Thus, we aimed to investigate the effects of a reduced nutrient density at dry-off on milk production, metabolism, the pattern of rumen fermentation, and milk fatty acid profile around dry-off and in the ensuing periparturient period. During the last week before dry-off, 26 Holstein cows were enrolled in pairs according to the expected calving date and either fed ad libitum ryegrass hay (nutrient restricted, NR; 13 cows) or continued to receive lactation diet (control group, CTR; 13 cows). After dry-off, both groups received only grass hay for 7 d, and free access to water was always provided. Blood, milk, and rumen fluid samples were collected from 7 d before dry-off to 28 DIM. Milk production, DMI (during the periparturient period), and rumination times were recorded daily. At dry-off, NR cows had decreased milk yield (-62%) and milk lactose compared with CTR but had higher fat and protein contents. In the subsequent lactation, no significant differences were observed in milk yield and composition. The BCS did not differ between groups during the transition period, but it decreased in NR after dry-off. Before dry-off, NR had decreased glucose, urea, and insulin, but higher creatinine, BHB, and nonesterified fatty acids (NEFA). The day after dry-off, NEFA were lower in NR, but they were higher 7 d after calving. At dry-off, NR had higher rumen pH, lower lactate, urea, and total volatile fatty acid concentrations. Considering volatile fatty acid molar proportions, NR had increased acetate but decreased propionate and butyrate at dry-off. Rumination time dropped 6 d before dry-off in NR and after dry-off in CTR, but no differences were observed in the periparturient period. Milk fatty acid profile revealed a remarkably lower proportion of short-chain fatty acids in NR at dry-off and a higher proportion of medium- and long-chain ones. These results confirmed that decreasing nutrient density reduce milk yield before dry-off. However, metabolism around dry-off was significantly affected, as suggested by plasma, rumen fluid, and milk analyses. Further research is required to investigate the impact of the metabolic effects on the inflammatory response, liver function, and immune system, particularly concerning the mammary gland.

Farm-level risk factors associated with increased milk β-hydroxybutyrate and hyperketolactia prevalence on farms with automated milking systems

The objectives of this study were to determine the farm-level hyperketolactia (HKL) prevalence, as diagnosed from milk β-hydroxybutyrate (BHB) concentration, on dairy farms milking with an automatic milking system (AMS) and to describe the farm-level housing, management, and nutritional risk factors associated with increased farm-average milk BHB and the within-herd HKL prevalence in the first 45 DIM. Canadian AMS farms (n = 162; eastern Canada n = 8, Quebec n = 23, Ontario n = 75, western Canada n = 55) were visited once between April to September 2019 to record housing and herd management practices. The first test milk data for each cow under 45 DIM were collected, along with the final test of the previous lactations for all multiparous cows, from April 1, 2019 to September 30, 2020. The first test milk BHB was then used to classify each individual cow as having HKL (milk BHB ≥ 0.15 mmol/L) at the time of testing. Milk fat and protein content, milk BHB, and HKL prevalence were summarized by farm and lactation group (all, primiparous, and multiparous). During this same time period, formulated diets for dry and lactating cows, including ingredients and nutrient composition, and AMS milking data were collected. Data from the AMS were used to determine milking behaviors and milk production of each herd during the first 45 DIM. Multivariable regression models were used to associate herd-level housing, feeding management practices, and formulated nutrient composition with first test milk BHB concentrations and within-herd HKL levels separately for primiparous and multiparous cows. The within-herd HKL prevalence for all cows was 21.8%, with primiparous cows having a lower mean prevalence (12.2 ± 9.2%) than multiparous cows (26.6 ± 11.3%). Milk BHB concentration (0.095 ± 0.018 mmol/L) and HKL prevalence for primiparous cows were positively associated with formulated prepartum DMI and forage content of the dry cow diet while being negatively associated with formulated postpartum DMI, the major ingredient in the concentrate supplemented through the AMS, and the PMR-to-AMS concentrate ratio. However, multiparous cows' milk BHB concentration (0.12 ± 0.023 mmol/L) and HKL prevalence were positively associated with the length of the previous lactation, milk BHB at dry off, prepartum diet nonfiber carbohydrate content, and the major forage fed on farm, while tending to be negatively associated with feed bunk space during lactation. This is the first study to determine the farm-level risk factors associated with herd-level prevalence of HKL in AMS dairy herds, thus helping optimize management and guide diet formulation to promote the reduction of HKL prevalence.

Rumen fermentation parameters and papillae development in Simmental growing bulls with divergent residual feed intake

Residual feed intake (RFI), a widespread index used to measure animal feed efficiency, is influenced by various individual biological factors related to inter-animal variation that need to be assessed. Herein, 30 Simmental bulls, raised under the same farm conditions, were divided on the basis of RFI values into a high efficient group (HE, RFI =  - 1.18 ± 0.33 kg DM/d, n = 15) and a low efficient group (LE, RFI = 0.92 ± 0.35 kg DM/d, n = 15). Subsequently, bulls were slaughtered at an average BW of 734 ± 39.4 kg. Their ruminal fermentation traits were analysed immediately after slaughtering and after 24 h of in vitro incubation. Furthermore, ruminal micro-biota composition and ruminal papillae morphology were examined. The LE group exhibited a higher propionate concentration as a percentage of total volatile fatty acids (17.3 vs 16.1%, P = 0.04) in the rumen fluid collected during slaughtering, which was also confirmed after in vitro fermentation (16.6 vs 15.4% respectively for LE and HE, P = 0.01). This phenomenon resulted in a significant alteration in the acetate-to-propionate ratio (A:P) with higher values for the HE group, both after slaughter (4.01 vs 3.66, P = 0.02) and after in vitro incubation (3.78 vs 3.66, P = 0.02). Methane production was similar in both groups either as absolute production (227 vs 218 mL for HE and LE, respectively) or expressed as a percentage of total gas (approximately 22%). Even if significant differences (P < 0.20) in the relative abundance of some bacterial genera were observed for the two RFI groups, no significant variations were observed in the alpha (Shannon index) and beta (Bray-Curtis index) diversity. Considering the papillae morphology, the LE subjects have shown higher length values (6.26 vs 4.90 mm, P < 0.01) while HE subjects have demonstrated higher papillae density (46.4 vs 40.5 n/cm2, P = 0.02). Histo-morphometric analysis did not reveal appreciable modifications in the total papilla thickness, boundaries or surface between the experimental groups. In conclusion, our results contribute to efforts to analyse the factors affecting feed efficiency at the ruminal level. Propionate production, papillae morphology and a few bacterial genera certainly play a role in this regard, although not a decisive one.

Postnatal Growth and Development of the Rumen: Integrating Physiological and Molecular Insights

The rumen plays an essential role in the physiology and production of agriculturally important ruminants such as cattle. Functions of the rumen include fermentation, absorption, metabolism, and protection. Cattle are, however, not born with a functional rumen, and the rumen undergoes considerable changes in size, histology, physiology, and transcriptome from birth to adulthood. In this review, we discuss these changes in detail, the factors that affect these changes, and the potential molecular and cellular mechanisms that mediate these changes. The introduction of solid feed to the rumen is essential for rumen growth and functional development in post-weaning calves. Increasing evidence suggests that solid feed stimulates rumen growth and functional development through butyric acid and other volatile fatty acids (VFAs) produced by microbial fermentation of feed in the rumen and that VFAs stimulate rumen growth and functional development through hormones such as insulin and insulin-like growth factor I (IGF-I) or through direct actions on energy production, chromatin modification, and gene expression. Given the role of the rumen in ruminant physiology and performance, it is important to further study the cellular, molecular, genomic, and epigenomic mechanisms that control rumen growth and development in postnatal ruminants. A better understanding of these mechanisms could lead to the development of novel strategies to enhance the growth and development of the rumen and thereby the productivity and health of cattle and other agriculturally important ruminants.

Effects of offering free-choice hay for the first 5 days postpartum on productivity, serum inflammatory markers, gut permeability, and colon gene expression in fresh dairy cows

The objective of the present study was to evaluate the effects of offering free-choice hay to cows during the first 5 d immediately after calving on feed intake, milk yield, plasma metabolites, serum inflammatory markers, rumination, gut permeability, and colon gene expression. It was hypothesized that cows offered free-choice hay would have lower gut permeability, lower inflammation, and higher milk production, compared with cows not offered hay. Thirty-two multiparous cows were fed a closeup total mixed ration (TMR; 21.5% starch, 32.1% forage neutral detergent fiber [NDF] on a dry matter basis) until calving. In the postpartum period, all cows were fed a fresh cow TMR (26.8% starch and 23.4% forage NDF) from calving until 21 DIM, and were assigned randomly to receive 1 of 2 treatments as follows: (1) free-choice timothy hay (61.6% NDF; 9.6% crude protein), offered outside of the TMR in a separate manger, for the first 5 d postpartum (FCH; n = 20), or 2) no free-choice hay (NH; n = 12). The FCH cows tended to have lower serum haptoglobin concentration on d 3, compared with NH (0.95 vs. 1.52 mg/mL). Within the FCH group, cows with greater hay intake had a smaller increase in serum amyloid A from d 1 to 3 after calving (r = 0.37), and tended to have a smaller increase in serum haptoglobin concentration (r = 0.36). Cows in the FCH group had a lower ratio of starch intake (kg) to forage NDF intake (kg) on d 1 and 2, compared with NH (0.91 vs. 1.14 ± 0.03), and cows that had a lower starch:forage NDF ratio tended to have a smaller increase in serum haptoglobin concentration from d 1 to 3 after calving (r = 0.32). Cows in the FCH group had lower TMR dry matter intake (DMI; 15.0 vs. 17.1 ± 0.93 kg/d) and lower total DMI (TMR + hay DMI; 15.9 vs. 17.1 ± 0.87 kg/d), from d 1 to 5 when free-choice hay was offered, compared with NH. However, the hay treatment did not affect plasma energy metabolite concentration, gut permeability, colon gene expression, milk yield, rumination time, or change in body weight or body condition score. Overall, these findings suggest that offering free-choice hay for the first 5 d after calving may reduce serum inflammatory marker concentration, but milk yield may not increase, due to lower intake.

Integrated microbiota-host-metabolome approaches reveal adaptive ruminal changes to prolonged high-grain feeding and phytogenic supplementation in cattle

Diets rich in readily fermentable carbohydrates primarily impact microbial composition and activity, but can also impair the ruminal epithelium barrier function. By combining microbiota, metabolome, and gene expression analysis, we evaluated the impact of feeding a 65% concentrate diet for 4 weeks, with or without a phytogenic feed additive (PFA), on the rumen ecosystem of cattle. The breaking point for rumen health seemed to be the second week of high grain (HG) diet, with a dysbiosis characterized by reduced alpha diversity. While we did not find changes in histological evaluations, genes related with epithelial proliferation (IGF-1, IGF-1R, EGFR, and TBP) and ZO-1 were affected by the HG feeding. Integrative analyses allowed us to define the main drivers of difference for the rumen ecosystem in response to a HG diet, identified as ZO-1, MyD88, and genus Prevotella 1. PFA supplementation reduced the concentration of potentially harmful compounds in the rumen (e.g. dopamine and 5-aminovaleric acid) and increased the tolerance of the epithelium toward the microbiota by altering the expression of TLR-2, IL-6, and IL-10. The particle-associated rumen liquid microbiota showed a quicker adaptation potential to prolonged HG feeding compared to the other microenvironments investigated, especially by the end of the experiment.

Elucidating the factors and consequences of the severity of rumen acidosis in first-lactation Holstein cows during transition and early lactation

First-lactation cows are particularly prone to subacute ruminal acidosis (SARA) during transition. Besides common risk factors of SARA, such as feeding of starch-rich diets, an individual severity of SARA in cows has been recently evidenced. Yet, the factors that play a role in SARA severity have not been elucidated. The main goal of this research was to evaluate the factors of SARA severity in first-lactation cows during transition and early lactation, which go beyond high-grain feeding, and to explore their impact on behavior, health, and fermentation in the rumen and hindgut. Twenty-four first-lactation Holstein cows with the same feeding regime were used starting from 3 wk before the expected calving day until 10 wk postpartum. Cows received a close-up diet (32% concentrate) until calving and were then transitioned to a lactation diet (60% concentrate) within 1 week. The SARA severity was assessed by cluster analysis of several rumen pH metrics, which revealed exceptionally longer and more severe SARA in cows denominated as high (n = 9), as compared to moderate (n = 9) and low (n = 6) SARA severity cows (P < 0.01). The logistic analysis showed that the length of close-up feeding, age at parturition, and the level of dry matter intake (DMI) were the main factors that influenced the cows' odds for high SARA severity (each P ≤ 0.01). Moreover, the ANOVA hinted differences in the metabolic activity of the ruminal microbiome to promote SARA severity, as indicated by highest ruminal propionate proportions (P = 0.05) in high SARA severity cows, also with similar DMI. The distinct SARA severity was marginally reflected in behavior and there were no effects of SARA severity or high-grain feeding on blood inflammation markers, which peaked at parturition regardless of SARA severity (P < 0.01). Still, ongoing high-grain feeding increased liver enzyme concentrations from 6 wk postpartum on, compared to weeks before (P < 0.01), yet irrespectively of SARA severity. In conclusion, first-lactation cows differed in SARA severity under the same feeding regime, which was ascribed to management factors and differences in ruminal fermentation. Further research is warranted to validate these findings and to understand the mechanisms behind differences in the metabolic function of rumen microbiome, in particular in terms of evaluating markers for various SARA severity, as well as to evaluate potential long-term effects on health, performance, fertility, and longevity of dairy cows.

Graduate Student Literature Review: The challenge of drying-off high-yielding dairy cows

The cessation of lactation (i.e., dry-off) in dairy cattle is an area of research that has received much focus in recent years. The dry period is necessary to optimize tissue remodeling of the mammary gland, but represents a stressful event, incorporating several changes in daily routine, diet, and metabolism. Moreover, the high milk yields achieved by modern cows in late gestation exacerbate the need for relevant manipulations in the days around dry-off, as excessive accumulation of milk might jeopardize the success of the dry period, with potential negative effects on future lactation. Production levels over 15 kg/d are an additional risk factor for udder health, delay mammary involution, and worsen metabolic stress and inflammatory responses. Furthermore, the pressure to reduce antibiotic usage in farm animals has resulted in increased attention on the dry period, given that historically most dairy cattle were provided prophylactic intramammary antibiotic treatment at dry-off as a means to reduce the risk of intramammary infections in the subsequent lactation. Several strategies have been proposed over the years to cope with these challenges, aiming to gradually reduce milk yield before dry-off, promoting at the same time the start of mammary involution. Among them, the most common are based on feed or nutrient restriction, a decrease in milking frequency, or administration of prolactin inhibitors. These practices have different capacities to reduce milk yield through different mechanisms and entail several implications for udder health, animal welfare, behavior, endocrine status, metabolism, and inflammatory conditions. The present review aims to provide a comprehensive overview of the dry-off phase in high-yielding cows and of the impact of high milk production at dry-off, and to describe possible strategies that might be implemented by farmers and veterinarians to optimize this critical phase in an integrated way.

Effect of Prepartum Magnesium Butyrate Supplementation on Rumination Time, Milk Yield and Composition, and Blood Parameters in Dairy Cows

Background: Magnesium butyrate (MgB) supplementation of dairy cows during the three-week close-up period was tested for its effects on blood energy analytes, rumination time, inflammation, and lactation performance. Methods: Daily milk yield was recorded and weekly milk samples collected for the first 70 days of lactation from MgB supplemented (MgB, n = 34), and unsupplemented (Control, n = 31) multiparous Holstein-Friesian cows. During a period from week 3 to week 10 postpartum, blood samples were taken and analyzed for various parameters, and ruminant activity was measured. Results: The MgB group yielded 25.2% more milk than the Control during week 1, and had increased milk fat and protein concentrations over a longer duration. Somatic cell counts (SCC) were decreased in the MgB group independent of days in milk. No differences were observed between groups in terms of plasma non-esterified fatty acids, β-hydroxybutyrate, glucose, or blood iCa levels. The MgB group had lower haptoglobin (Hp) levels during lactation relative to the Control group. Time spent ruminating increased after calving with MgB due to a shorter post calving rumination delay relative to the Control group. Conclusions: Prepartum MgB supplementation improved lactation performance without affecting blood energy analytes. The basis by which MgB also improved rumination activity remains to be determined, as DMI could not be assessed. As MgB lowered SCC and Hp concentrations, it is speculated that MgB may help minimize postpartum inflammatory processes.

Rumen Biogeographical Regions and Microbiome Variation

The rumen is a complex organ that is critical for its host to convert low-quality feedstuffs into energy. The conversion of lignocellulosic biomass to volatile fatty acids and other end products is primarily driven by the rumen microbiome and its interaction with the host. Importantly, the rumen is demarcated into five distinct rumen sacs as a result of anatomical structure, resulting in variable physiology among the sacs. However, rumen nutritional and microbiome studies have historically focused on the bulk content or fluids sampled from single regions within the rumen. Examining the rumen microbiome from only one or two biogeographical regions is likely not sufficient to provide a comprehensive analysis of the rumen microbiome and its fermentative capacity. Rumen biogeography, digesta fraction, and microbial rumen–tissue association all impact the diversity and function of the entirety of the rumen microbiome. Therefore, this review discusses the importance of the rumen biographical regions and their contribution to microbiome variation.

Differential carbon utilization enables co-existence of recently speciated Campylobacteraceae in the cow rumen epithelial microbiome

The activities of different microbes in the cow rumen have been shown to modulate the host's ability to utilize plant biomass, while the host-rumen interface has received little attention. As datasets collected worldwide have pointed to Campylobacteraceae as particularly abundant members of the rumen epithelial microbiome, we targeted this group in a subset of seven cows with meta- and isolate genome analysis. We show that the dominant Campylobacteraceae lineage has recently speciated into two populations that were structured by genome-wide selective sweeps followed by population-specific gene import and recombination. These processes led to differences in gene expression and enzyme domain composition that correspond to the ability to utilize acetate, the main carbon source for the host, at the cost of inhibition by propionate. This trade-off in competitive ability further manifests itself in differential dynamics of the two populations in vivo. By exploring population-level adaptations that otherwise remain cryptic in culture-independent analyses, our results highlight how recent evolutionary dynamics can shape key functional roles in the rumen microbiome.

Prevalence of Ruminant Paramphistomosis and Comparative Histopathology of the Infected Rumens in Narowal District, Punjab, Pakistan

The present study reports the prevalence of Paramphistomum spp. in small and large ruminants and their association with the histopathology of the infected rumens. A total of 384 animals were screened for Paramphistomum spp. The animals found positive for Paramphistomum spp. were divided into three groups according to the worm load/5 cm2 (G1: 10 - 20 worms/5 cm2 = Low, G2: 20 - 40 worms/5 cm2 = Medium, and G3: >41 worms/5 cm2 = High). Tissue slides were prepared from samples of the rumen (1 cm2) taken from animals positive for ruminal fluke to determine the histological parameters, including epithelial length or thickness, length and width of the ruminal papilla, and thickness of tunica submucosa and mucularis externae. The overall prevalence of Paramphistomum spp. in the ruminant population of district Narowal was 56.25 % with a significant (P < 0.05) variation among different species of ruminants. The highest prevalence was in cattle, followed in order by buffalo, goat, and sheep. Epithelium thickness was significantly correlated with parasite load in large ruminants and the most significant (P < 0.05) decrease in epithelium thickness was in Group B (31.12 ± 1.82 μm) and Group C (31.07 ± 1.68 μm) and a same trend was recorded in small ruminants. Histopathological changes due to Paramphistomum spp. are reported for the first time, which explained the histomorphological and physiological changes in Paramphistomum-infected rumens which might be associated with lowered feed efficiency and productivity in ruminants.

Invited review: Effect of subacute ruminal acidosis on gut health of dairy cows

Subacute ruminal acidosis (SARA) is assumed to be a common disease in high-yielding dairy cows. Despite this, the epidemiological evidence is limited by the lack of survey data. The prevalence of SARA has mainly been determined by measuring the pH of ruminal fluid collected using rumenocentesis. This may not be sufficiently accurate, because the symptoms of SARA are not solely due to ruminal pH depression, and ruminal pH varies among sites in the rumen, throughout a 24-h period, and among days. The impact of SARA has mainly been studied by conducting SARA challenges in cows, sheep, and goats based on a combination of feed restriction and high-grain feeding. The methodologies of these challenges vary considerably among studies. Variations include differences in the duration and amount of grain feeding, type of grain, amount and duration of feed restriction, number of experimental cows, and sensitivity of cows to SARA challenges. Grain-based SARA challenges affect gut health. These effects include depressing the pH in, and increasing the toxin content of, digesta. They also include altering the taxonomic composition of microbiota, reducing the functionality of the epithelia throughout the gastrointestinal tract (GIT), and a moderate inflammatory response. The effects on the epithelia include a reduction in its barrier function. Effects on microbiota include reductions in their richness and diversity, which may reduce their functionality and reflect dysbiosis. Changes in the taxonomic composition of gut microbiota throughout the GIT are evident at the phylum level, but less evident and more variable at the genus level. Effects at the phylum level include an increase in the Firmicutes to Bacteroidetes ratio. More studies on the effects of a SARA challenge on the functionality of gut microbiota are needed. The inflammatory response resulting from grain-based SARA challenges is innate and moderate and mainly consists of an acute phase response. This response is likely a combination of systemic inflammation and inflammation of the epithelia of the GIT. The systemic inflammation is assumed to be caused by translocation of immunogenic compounds, including bacterial endotoxins and bioamines, through the epithelia into the interior circulation. This translocation is increased by the increase in concentrations of toxins in digesta and a reduction of the barrier function of epithelia. Severe SARA can cause rumenitis, but moderate SARA may activate an immune response in the epithelia of the GIT. Cows grazing highly fermentable pastures with high sugar contents can also have a low ruminal pH indicative of SARA. This is not accompanied by an inflammatory response but may affect milk production and gut microbiota. Grain-based SARA affects several aspects of gut health, but SARA resulting from grazing high-digestible pastures and insufficient coarse fiber less so. We need to determine which method for inducing SARA is the most representative of on-farm conditions.

Increased intake of mono- and disaccharides by Reeves's muntjac (Muntiacus reevesi). Effect on gastrointestinal tract structure and function and blood parameters

The aim of this study was to determine the effect of an increased mono- and disaccharide (MD) intake on selected functions and structure of the gastrointestinal tract (GIT), and selected blood parameters in Reeves's muntjac (Muntiacus reevesi), a small browsing ruminant. Eighteen male muntjacs were fed diets consisting of lucerne (ad libitum), a high fibre pellet (100 g/day) and wheat bran (30 g/day) without (MD0) or with addition of 10 or 20 g of glucose, fructose and sucrose mixture/day (MD10 and MD20, respectively) for 14 days. MD dosages were set to increase intake of these saccharides by 25% and 50% relative to MD0, which resulted in a range of water-soluble carbohydrate content in the consumed dry matter from 7% to 12%. Compared to MD0 animals, MD20 animals had a lower dry matter intake, a higher MD concentrations in the reticulorumen (RR), abomasal and small intestinal digesta, higher ruminal butyrate concentration, higher SGLT1 expression in the epithelium of proximal jejunum, higher plasma glucose, lower RR tissue weight but greater caecal tissue weight (p ≤ 0.05), and had or tended to have shorter papillae and lower mucosa surface area in the Atrium ruminis (by 44%; p = 0.02 and p = 0.10, respectively); MD10 animals tended to have higher MD concentrations in the abomasal and small intestinal digesta (p ≤ 0.10), and a higher amylolytic activity (p = 0.02) as well as a tendency to lower xylanolytic activity in the RR digesta (p = 0.06). MD supplementation did not affect ruminal pH. In conclusion, low to moderate increase of MD intake increased MD concentrations in the RR, abomasal and intestinal digesta, and SGLT1 expression in intestinal epithelium, suggesting incomplete fermentation of those saccharides in the RR. MD supplementation dose-dependently affects structure of GIT in Reeves's muntjac.

Light microscopic observations of the ruminal papillae of cattle on diets with divergent forage to cereal ratios

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Characteristic histological change is associated with dietary cereal proportion.

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Immune-related cells are found in higher densities in cattle on lower cereal diets.

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Cereal proportion is associated with cell layer thickness, integrity, and sloughing.

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No benefit of Elastin Martius Scarlet Blue stain use over Haematoxylin and Eosin.

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Novel scoring system can differentiate groups by approximate dietary cereal level.

High levels of supplementation with cereal increases production rates in cattle but can increase incidence of disease, ranging from mild indigestion to acute ruminal acidosis and death. Therefore, there is motivation to determine biological markers which can be used to identify whether animals have been, or are being fed, sufficient or excessive cereals. This study aimed to describe light microscopic findings from animals being fed diverse dietary cereal proportions and to test the performance of a novel rumen epithelial scoring system. Rumen wall tissue samples were obtained from the abattoir from 195 cattle from 11 Scottish farms and processed for histological examination. Light microscopic examination was used to characterise ruminal epithelial response to dietary challenge. Secondary objectives included describing the distribution of immune-related cells in bovine ruminal epithelium and assessing the use of a modified Elastin Martius Scarlet Blue stain (EMSB) for histological examination of the rumen epithelium. Cells staining positive for cluster of differentiation 3 were distributed mainly in the lower layers of the stratum basale and were found in higher densities in animals offered lower cereal proportion diets. Cells staining positive for major histocompatibility complex class 2 (MHCII) were most common in perivascular locations and in the junction between the lower stratum basale and the propria-submucosa. The density of MHCII positive staining cells was higher in animals on lower cereal diets. The level of supplementation with cereal was also associated with the thickness of the stratum corneum (SCT) and stratum granulosum (SGT), the integrity of the stratum corneum and sloughing of cornified cells. There were no advantages in using EMSB stain over haematoxylin and eosin (H&E) in this scoring system. We concluded that a scoring system that included only SCT, SGT and a measure of the loss of appearance of intercellular space allowed differentiation of groups of animals according to the level of cereal supplementation.

Effects of Heat Stress on the Ruminal Epithelial Barrier of Dairy Cows Revealed by Micromorphological Observation and Transcriptomic Analysis

Heat stress (HS) alters the rumen fermentation of dairy cows thereby affecting the metabolism of rumen papillae and thus the epithelial barrier function. The aim of the present study was to investigate if HS damages the barrier function of ruminal epithelia. Eight multiparous Holstein dairy cows with rumen cannula were randomly equally allocated to two replicates (n = 4), with each replicate being subjected to heat stress or thermal neutrality and pair-feeding in four environmental chambers. Micromorphological observation showed HS aggravated the shedding of the corneum and destroyed the physical barrier of the ruminal epithelium to a certain extent. Transcriptomics analysis of the rumen papillae revealed pathways associated with DNA replication and repair and amino acid metabolism were perturbated, the biological processes including sister chromatid segregation, etc. were up-regulated by HS, while the MAPK and NF-kB cell signaling pathways were downregulated. However, no heat stress-specific change in the expression of tight junction protein or TLR4 signaling was found, suggesting that HS negatively affected the physical barrier of the ruminal epithelium to some extent but did not break the ruminal epithelium. Heat stress invoked mechanisms to maintain the integrity of the rumen epithelial barrier by upregulating the expression of heat shock protein and repairments in rumen papillae. The increase in amino acid metabolism in rumen papillae might affect the nutrient utilization of the whole body. The findings of this study may inform future research to better understand how heat stress affects the physiology and productivity of lactating cows and the development of mitigation strategies.

Sodium butyrate administration modulates the ruminal villus height, inflammation-related gene expression, and plasma hormones concentration in dry cows fed a high-fiber diet

The objectives of this study were to evaluate the effects of sodium butyrate on the ruminal villus morphology, mRNA expression associated with nutrient metabolism and inflammation in the ruminal epithelium, and plasma concentrations of metabolites and hormones in non-lactating cows fed a high-fiber diet. Four Holstein cows with a rumen cannula were assigned to two treatments in a crossover design. The treatments were ruminal administration of sodium butyrate premix or control premix before feeding to cows fed the same total mixed ration mainly composed of glass silage once a day. Sodium butyrate was provided at a butyrate dose of 0.04% per kg body weight. The control premix was made by replacing sodium-butyrate with wheat bran. The plasma β-hydroxybutyrate concentration increased 3 to 6 h after the butyrate premix administration but returned to a concentration similar to that of the control before feeding. After continuous administration, increases in the ruminal villus height and plasma concentration of glucagon-like peptide-2, and lower gene expression of TNF-α, IL-1β, and TLR-2 in the rumen epithelium were observed in cows supplied with the butyrate premix. These results showed that sodium butyrate affects rumen epithelial morphology and plasma concentrations of hormones even under a low fermentable diet.

Pathomorphological changes in the early postnatal period in a calf with abomasum rupture

The main cause of the disease and death of calves in the early postembryonic period of development is a feeding disorder. The aim of the work was to analyze macro-and micromorphological changes in the digestive system of a calf with a rennet rupture. To achieve this goal, standard macro-and microscopic research methods were used. Macroscopic examination revealed thickening, erosion of the mucous membrane of the esophageal gutter rollers, accumulation of contents in the scar, mesh and book, hyperemia of the mucous membranes; thinning and rupture of the rennet wall; pronounced hyperemia of the mucous membrane of the small intestine, thickening of the mucous membrane of the thick section; an increase in mesenteric lymph nodes and a change in their consistency. Microscopically, the thickness of the epithelium, submucosal and muscle layer is most developed in the abomasum and was, respectively, 0.68-0.72 mm, 0.23-0.32 mm and 0.98-1.05 mm. Villi were found in the folds of the scar, numerous well – developed longitudinally oriented protrusions were found in the book, lymphocellular clusters and bottom glands were found in the rennet; folds with well – developed crypts were found in the colon. Thus, as a result of feeding coarse feed, the deceased calf has catarrhal erosive lesions of the esophageal trough; serous-catarrhal abomasitis with signs of hemorrhagic with dilation and perforation in the cardiac part; hemorrhagic omasitis against the background of a book blockage; catarrhal reticulitis; catarrhal ruminitis and catarrhal enterocolitis.

Rumen Development of Artificially-Reared Lambs Exposed to Three Different Rearing Regimens

The objective of this study was to examine the effect of three different rearing regimens on rumen development in lambs reared artificially. Romney ram lambs were randomly allocated to one of three treatments: commercial milk replacer fed to 57 d of age and high fibre concentrate pellets (HFP57); commercial milk replacer, high fibre concentrate pellets, and early weaning from milk replacer at 42 d of age (HFP42); high protein milk replacer from 2-16 d of age followed by commercial milk replacer, low fibre concentrate pellets, and early weaning from milk replacer at 42 d of age (LFP42). Lambs were slaughtered at 57 d of age. Volatile fatty acid content in rumen fluid at slaughter was analysed and rumen tissue samples were collected for histological examination. The rumen n-butyric content was greater (p < 0.05) in both LFP42 and HFP42 treatment lambs compared to HFP57 lambs. The n-valeric content was greater (p < 0.05) in LFP42 lambs compared to both HFP57 and HFP42 treatment lambs. Thickness of the rumen dorsal wall determined by ultrasound scanning at 49 d was greater (p < 0.05) in both HFP42 and LFP42 lambs compared to HFP57 lambs. There was an interaction (p < 0.05) between treatment and site of rumen tissue sampling on papillae width, density, and rumen muscular layer thickness. Collectively, early weaning and the provision of a low fibre pellet leads to improved rumen function and physical development.

Gene network expression of whole blood leukocytes in dairy cows with different milk yield at dry-off

Dairy cows at dry-off undergo several management and physiological changes, resulting in alterations in plasma biomarkers of inflammation, oxidative stress, and immune system. High milk yield at the end of lactation exacerbates these responses. The underlying mechanism of these changes has yet to be elucidated. We hypothesized altered leukocyte gene expression after dry-off and different responses in cows with different milk yield. Thirteen Holstein dairy cows were sampled at the turn of dry-off to investigated whole blood leukocyte gene expression and were grouped according to the average milk yield during the last week of lactation: low (< 15 kg/d) and high milk yield (> 15 kg/d). Blood samples were collected in PAXgene tubes (Preanalytix, Hombrechtikon, Switzerland) at -7, 7, and 34 days from dry-off (DFD) to measure mRNA abundance of 37 genes. Normalized gene abundance data were subjected to MIXED model ANOVA (SAS Institute Inc., Cary, NC). Compared with -7 DFD, at 7 DFD RNA abundance of lipoxygenase genes (ALOX5, ALOX15) and myeloperoxidase (MPO) increased, and that of the antioxidant gene (SOD2) decreased. Meanwhile, genes related to recognition and immune mediation (CD16, MYD88, TLR2), migration and cell adhesion (CX3CR1, ITGAL, ITGB2, TLN1), and the antimicrobial gene MMP9 were downregulated at 7 or 34 DFD, whereas the antimicrobial IDO1 gene was upregulated. Compared with low-producing cows, cows with high milk yield at dry-off cows had upregulated expression of the pro-inflammatory cytokines IL8 and IL18 and a greater reduction in transcript abundance of the toll-like receptor (TLR) recognition-related gene TLR2. Overall, the dry-off confirmed to be a phase of intense changes, triggering an inflammatory response and somewhat suppressing leukocyte immune function. In cows with high milk yield during the week before dry-off, the inflammatory response was exacerbated.

The Transition Period Updated: A Review of the New Insights into the Adaptation of Dairy Cows to the New Lactation

Recent research on the transition period (TP) of dairy cows has highlighted the pivotal role of immune function in affecting the severity of metabolic challenges the animals face when approaching calving. This suggests that the immune system may play a role in the etiology of metabolic diseases occurring in early lactation. Several studies have indicated that the roots of immune dysfunctions could sink way before the “classical” TP (e.g., 3 weeks before and 3 weeks after calving), extending the time frame deemed as “risky” for the development of early lactation disorders at the period around the dry-off. Several distressing events occurring during the TP (i.e., dietary changes, heat stress) can boost the severity of pre-existing immune dysfunctions and metabolic changes that physiologically affect this phase of the lactation cycle, further increasing the likelihood of developing diseases. Based on this background, several operational and nutritional strategies could be adopted to minimize the detrimental effects of immune dysfunctions on the adaptation of dairy cows to the new lactation. A suitable environment (i.e., optimal welfare) and a balanced diet (which guarantees optimal nutrient partitioning to improve immune functions in cow and calf) are key aspects to consider when aiming to minimize TP challenges at the herd level. Furthermore, several prognostic behavioral and physiological indicators could help in identifying subjects that are more likely to undergo a “bad transition”, allowing prompt intervention through specific modulatory treatments. Recent genomic advances in understanding the linkage between metabolic disorders and the genotype of dairy cows suggest that genetic breeding programs aimed at improving dairy cows’ adaptation to the new lactation challenges (i.e., through increasing immune system efficiency or resilience against metabolic disorders) could be expected in the future. Despite these encouraging steps forward in understanding the physiological mechanisms driving metabolic responses of dairy cows during their transition to calving, it is evident that these processes still require further investigation, and that the TP—likely extended from dry-off—continues to be “the final frontier” for research in dairy sciences.

Unveiling the Bovine Epimural Microbiota Composition and Putative Function

Numerous studies have used the 16S rRNA gene target in an attempt to characterize the structure and composition of the epimural microbiota in cattle. However, comparisons between studies are challenging, as the results show large variations associated with experimental protocols and bioinformatics methodologies. Here, we present a meta-analysis of the rumen epimural microbiota from 11 publicly available amplicon studies to assess key technical and biological sources of variation between experiments. Using the QIIME2 pipeline, 332 rumen epithelial microbiota samples were analyzed to investigate community structure, composition, and functional potential. Despite having a significant impact on microbial abundance, country of origin, farm, hypervariable region, primer set, animal variability, and biopsy location did not obscure the identification of a core microbiota. The bacterial genera Campylobacter, Christensenellaceae R-7 group, Defluviitaleaceae UCG-011, Lachnospiraceae UCG-010, Ruminococcaceae NK4A214 group, Ruminococcaceae UCG-010, Ruminococcaceae UCG-014, Succiniclasticum, Desulfobulbus, and Comamonas spp. were found in nearly all epithelium samples (>90%). Predictive analysis (PICRUSt) was used to assess the potential functions of the epithelial microbiota. Regularized canonical correlation analysis identified several pathways associated with the biosynthesis of precursor metabolites in Campylobacter, Comamonas, Desulfobulbus, and Ruminococcaceae NK4A214, highlighting key metabolic functions of these microbes within the epithelium.

Effects of pre- and postpartum dietary starch content on productivity, plasma energy metabolites, and serum inflammation indicators of dairy cows

The objective of this study was to evaluate the effects of the starch content of pre- and postpartum diets on productivity, plasma energy metabolites, and serum markers of inflammation of dairy cows during the calving transition period. Eighty-eight primiparous and multiparous cows were randomly assigned to pre- and postpartum dietary treatments balanced for parity and pretrial body condition score at d 28 ± 3 before expected calving date. Cows were fed either a control [Control; 14.0% starch, dry matter (DM) basis] or high-starch (High; 26.1% starch, DM basis) prepartum diet commencing 28 ± 3 d before expected calving date. Following calving, cows were fed either a high-fiber (HF; 33.8% neutral detergent fiber, 25.1% starch, DM basis) or high-starch (HS; 27.2% neutral detergent fiber, 32.8% starch, DM basis) postpartum diet for the first 20 ± 2 d following calving. Cows fed the High prepartum diet had greater DM intake (12.4 vs. 10.2 kg/d), plasma concentrations of insulin (1.72 vs. 14.2 ng/mL), glucose (68.1 vs. 65.0 mg/dL), and glucagon-like peptide-2 (0.41 vs. 0.32 ng/mL) before parturition, but increased plasma free fatty acid concentration (452 vs. 363 µEq/L) and milk fat yield (1.64 vs. 1.48 kg/d) after parturition. Cows fed the HS postpartum diet had lower plasma free fatty acid (372 vs. 442 µEq/L) and serum haptoglobin (0.46 vs. 0.70 mg/mL) concentrations over a 3-wk period after calving. In addition, there was a tendency for interaction between prepartum and postpartum diets for milk yield, where feeding the HS postpartum diet increased milk yield compared with the HF diet for cows fed the Control prepartum diet (40.8 vs. 37.9 kg/d) but not for cows fed the High prepartum diet. These results suggest that management efforts to minimize the change in diet fermentability during the calving transition by feeding the High prepartum diet, the HF postpartum diet, or both did not increase productivity of dairy cows but increased fat mobilization after calving. Our findings also suggest that feeding high-starch postpartum diets can decrease fat mobilization and serum indicators of systemic inflammation and increase milk production even with the transition from a low-starch prepartum diet.

Effects of starch concentration of close-up diets on rumen pH and plasma metabolite responses of dairy cows to grain challenges after calving

The objective of this study was to evaluate the effects of starch concentration of close-up diets on plasma concentrations of energy metabolites and rumen pH of dairy cows after calving. Eighteen multiparous Holstein dairy cows (mean parity = 2.78; mean body weight = 708 kg; mean body condition score = 3.08) fitted with ruminal cannulas were assigned to treatment balanced for parity, body condition score, and expected calving date. Cows were enrolled in the study at d 28 ± 3 before the expected calving date and fed either a low-starch (LS; 14.0% starch) or high-starch (HS; 26.1% starch) diet until parturition. All cows were fed a common diet after calving (25.1% starch). A grain challenge was performed on d 7 ± 2 and 21 ± 2 after calving by dosing 6.35 kg (dry matter basis) of finely ground barley and wheat grain (1:1) into the rumen via cannula. Feeding the HS diet before calving increased the duration (369 vs. 49 min/d) and area of pH below 5.8 (85.1 vs. 5.2 pH × min/d) during d -10 to -8. In addition, even though all cows were fed a common diet after calving, HS cows tended to have longer duration (177 vs. 76 min/6 h) and greater area of pH below 5.8 (67.8 vs. 20.3 pH × min/6 h) during a grain challenge on d 7. Plasma concentration of insulin tended to be greater in cows fed the HS diet (1.40 vs. 1.09 ng/mL), whereas plasma free fatty acid concentration was not different between treatments during the grain challenge on d 7. During the grain challenge on d 21, neither rumen pH nor blood metabolites were different between the HS and LS cows. These findings suggested that feeding an HS diet during the close-up period does not mitigate rumen pH depression but may exacerbate it after calving compared with feeding an LS diet.

Metabolic Stress in the Transition Period of Dairy Cows: Focusing on the Prepartum Period

All modern, high-yielding dairy cows experience a certain degree of reduced insulin sensitivity, negative energy balance, and systemic inflammation during the transition period. Maladaptation to these changes may result in excessive fat mobilization, dysregulation of inflammation, immunosuppression, and, ultimately, metabolic or infectious disease in the postpartum period. Up to half of the clinical diseases in the lifespan of high-yielding dairy cows occur within 3 weeks of calving. Thus, the vast majority of prospective studies on transition dairy cows are focused on the postpartum period. However, predisposition to clinical disease and key (patho)physiological events such as a spontaneous reduction in feed intake, insulin resistance, fat mobilization, and systemic inflammation already occur in the prepartum period. This review focuses on metabolic, adaptive events occurring from drying off until calving in high-yielding cows and discusses determinants that may trigger (mal)adaptation to these events in the late prepartum period.

Supplementation of Spring Pasture with Harvested Fodder Beet Bulb Alters Rumen Fermentation and Increases Risk of Subacute Ruminal Acidosis during Early Lactation

Simple Summary

Fodder beet (FB) is widely used in grazing dairy systems of New Zealand to support early- and late-lactation milk production, however, the large fraction of water-soluble carbohydrate present in FB bulbs presents a risk of subacute and acute ruminal acidosis. Despite widespread use of FB across New Zealand, the incidence of ruminal acidosis using industry-recommended methods of feeding FB has not been investigated. This study analyzed the time-dependent changes to rumen fermentation, apparent dry matter intake, milk production, milk composition and plasma amino acid concentration of grazing dairy cows supplemented with moderate amounts (40% of dry matter intake) of FB during early lactation. Our findings indicate that incidence of subacute ruminal acidosis due to FB is greater than currently realized, as 25% of cows developed severe subacute ruminal acidosis following transition to target FB allocation (40% of daily intake). Across all cows, FB reduced rumen pH, feed conversion efficiency and was not advantageous to milk production. These results suggest methods for adapting cows to a diet containing FB require further evaluation to reduce the risk of subacute ruminal acidosis (SARA) experienced by individuals within the herd.

Abstract

In a cross-over design, eight rumen cannulated dairy cows were used to explore the industry-recommended method for dietary transition to fodder beet (FB: Beta vulgaris L.) on changes to rumen fermentation and pH, milk production, dry matter intake (DMI) and the risk of subacute ruminal acidosis (SARA) during early lactation. Cows were split into two groups and individually allocated a ryegrass (Lolium Perenne L.) and white clover (Trifolium repens L.) diet (HO) or the same herbage supplemented with 6 kg DM/cow of harvested fodder beet bulbs (FBH). Dietary adaptation occurred over 20 days consisting of: stage 1: gradual transition to target FB intake (days 1–12, +0.5 kg DM of FB/d); stage 2: acclimatization (days 13–17) and stage 3: post-adaption sampling (days 18–20). Response variables were analyzed as a factorial arrangement of diet and stage of adaption using a combination of ANOVA and generalized linear mixed modelling. Dietary proportion of FB represented 22, (stage 1), 32 (stage 2) and 38% (stage 3) of daily DMI. One cow during each period developed SARA from FB and the duration of low pH increased with FBH compared to the HO treatment (p < 0.01). Rumen concentrations of lactic and butyric acid increased with FBH but concentrations of acetate, propionate and total volatile fatty acids (VFA) declined by 9.3% at day 20, compared to the HO treatment (p < 0.01). Treatments did not affect milk production but total DMI with supplemented cows increased during the final stage of adaptation and feed conversion efficiency (FCE kg milk/kg DM) declined with the FBH treatment. The occurrence of SARA in 25% of animals fed FB suggest it is a high-risk supplement to animal health and further evaluation of industry-recommended methods for feeding FB at the individual- and herd-scale are needed.

Effect of Dry-Period Diet on the Performance and Metabolism of Dairy Cows in Early Lactation

Simple Summary

In dairy cows, the management of the dry period should optimize milk production and limit impact on metabolic health. In early lactation, there is little information on the effect of the dry-period diet composition on the production and composition of milk and the blood metabolites. The aim of this study was to compare the effects of different dry-period diets on the blood metabolites of dairy cows during the peripartum period and the milk yield and fatty acid profile at onset of lactation. This study showed that different dry-period diets can be used without impact on milk production and composition when these diets cover the needs of dairy cows. However, blood metabolites were more sensitive to the diet offered during the dry period. In early lactation, a dry-period diet based on corn and grass silages allowed a smooth transition with better rumen and liver function parameters.

Abstract

The objective of this work was to observe the effect of three different dry-period diets on blood metabolites (p = 9) and the production and fatty acid (FA) profile of milk (p = 19) in the peripartum period. In this study, 32 Holstein dairy cows, during their dry period, were divided in 3 different diet groups, as follows: the CONC diet (n = 11) was based on concentrate meal and straw, the CORN diet (n = 11) was based on corn silage, and the MIXED diet (n = 10) was based on corn and grass silages. According to our results, the variations of C18:2n-6, C18:3n-3, non-esterified fatty acid (NEFA), NEFA/cholesterol ratio, and albumin were significantly (p < 0.05) different, according to the dry diet. The dry-period diet also had a significant effect on the concentrations of urea and vitamin B₁₂ in the blood. In early lactation, this work showed that blood metabolites were more sensitive to changes in the dry diet than the production and FA profile of milk.

Review: Rumen sensors: data and interpretation for key rumen metabolic processes

Rumen sensors provide specific information to help understand rumen functioning in relation to health disorders and to assist in decision-making for farm management. This review focuses on the use of rumen sensors to measure ruminal pH and discusses variation in pH in both time and location, pH-associated disorders and data analysis methods to summarize and interpret rumen pH data. Discussion on the use of rumen sensors to measure redox potential as an indication of the fermentation processes is also included. Acids may accumulate and reduce ruminal pH if acid removal from the rumen and rumen buffering cannot keep pace with their production. The complexity of the factors involved, combined with the interactions between the rumen and the host that ultimately determine ruminal pH, results in large variation among animals in their pH response to dietary or other changes. Although ruminal pH and pH dynamics only partially explain the typical symptoms of acidosis, it remains a main indicator and may assist to optimize rumen function. Rumen pH sensors allow continuous monitoring of pH and of diurnal variation in pH in individual animals. Substantial drift of non-retrievable rumen pH sensors, and the difficulty to calibrate these sensors, limits their application. Significant within-day variation in ruminal pH is frequently observed, and large distinct differences in pH between locations in the rumen occur. The magnitude of pH differences between locations appears to be diet dependent. Universal application of fixed conversion factors to correct for absolute pH differences between locations should be avoided. Rumen sensors provide high-resolution kinetics of pH and a vast amount of data. Commonly reported pH characteristics include mean and minimum pH, but these do not properly reflect severity of pH depression. The area under the pH × time curve integrates both duration and extent of pH depression. The use of this characteristic, as well as summarizing parameters obtained from fitting equations to cumulative pH data, is recommended to identify pH variation in relation to acidosis. Some rumen sensors can also measure the redox potential. This measurement helps to understand rumen functioning, as the redox potential of rumen fluid directly reflects the microbial intracellular redox balance status and impacts fermentative activity of rumen microorganisms. Taken together, proper assessment and interpretation of data generated by rumen sensors requires consideration of their limitations under various conditions.

Tibetan sheep have a high capacity to absorb and to regulate metabolism of SCFA in the rumen epithelium to adapt to low energy intake

The nutritional intake of Tibetan sheep on the harsh Qinghai-Tibetan Plateau is often under maintenance requirements, especially during the long, cold winter. However, they have adapted well and even thrive under these conditions. The aim of the present study was to gain insight into how the rumen epithelium of Tibetan sheep has adapted to the consumption of low-energy-level diets. For this purpose, we compared Tibetan and small-tailed Han sheep (n 24 of each breed, all wethers and 1·5 years of age), which were divided randomly into one of four groups and offered ad libitum diets of different digestible energy (DE) densities: 8·21, 9·33, 10·45 and 11·57 MJ DE/kg DM. The Tibetan sheep had higher rumen concentrations of total SCFA, acetate, butyrate and iso-acids but lower concentrations of propionate than small-tailed Han sheep. The Tibetan sheep had higher absorption capability of SCFA due to the greater absorption surface area and higher mRNA expression of the SCFA absorption relative genes than small-tailed Han sheep. For the metabolism of SCFA in the rumen epithelium, the small-tailed Han sheep showed higher utilisation of the ketogenesis pathway than Tibetan sheep; however, Tibetan sheep had greater regulation capacity in SCFA metabolism pathways. These differences between breeds allowed the Tibetan sheep to have greater capability of absorbing SCFA and better capacity to regulate the metabolism of SCFA, which would allow them to cope with low energy intake better than small-tailed Han sheep.

Environmental sustainability assessment of tropical dairy buffalo farming vis-a-vis sustainable feed replacement strategy

Feeding management in dairy animals is crucial for ensuring optimal production apart from making the farming as a whole, a more sustainable activity. In our study we evaluated the production and environmental effects of two different feeding regimens i.e., one dominated by traditional cottonseed meal (CSM) and other with coated urea (slow release urea - SRU) as a replacement for CSM on dairy buffalo production. The SRU at 2% level was evaluated by conducting two different trials using twelve lactating Murrah buffaloes and four adult Murrah buffalo bulls. Neither diet nor dry period management showed any substantial effect on milk components, intakes, nutrients’ digestibility coefficients, and nutritive values. The SRU diet revealed increased (P < 0.01) rumen pH, ammonia nitrogen, volatile fatty acids, and microbial nitrogen yield, which were interacted with time of post-prandial sampling. The dynamics of nitrogen metabolism revealed unaltered N-based parameters, except for degradable-N intake and serum urea-N at 3 hr post-feeding. The CSM replacements did not influence (P > 0.05) the residual feed intake, but led to an enhanced milk retention efficiency of nitrogen, calcium, and phosphorus contents, thus reducing their impact on soil pollution and eutrophication of water bodies. Despite an unaltered (P > 0.05) enteric methane emission, SRU diets achieved in decreasing manure methane and nitrous oxide emission. Furthermore, the virtual water flow and lifecycle assessment revealed a water sparing effect and low carbon foot print per unit milk production. In summary, the CSM replacements with SRU could achieve an economical and eco-friendly production system from animal nutrition perspective.

Jersey steer ruminal papillae histology and nutrigenomics with diet changes

The transition from a high forage to a high concentrate diet is an important milestone for beef cattle moving from a stocker system to the feedlot. However, little is known about how this transition affects the rumen epithelial gene expression. This study assessed the effects of the transition from a high forage to a high concentrate diet as well as the transition from a high concentrate to a high forage diet on a variety of genes as well as ruminal papillae morphology in rumen fistulated Jersey steers. Jersey steers (n = 5) were fed either a high forage diet (80% forage and 20% grain) and transitioned to a high concentrate diet (20% forage and 80% grain) or a high concentrate diet (40% forage and 60% grain) and transitioned to a high forage diet (100% forage). Papillae from the rumen were collected for histology and RT‐qPCR analysis. Body weight had a tendency for significant difference (p = .08). Histological analysis did not show changes in papillae length or width in steers transitioning from a high forage to a high concentrate diet or vice versa (p > .05). Genes related to cell membrane structure (CLDN1, CLDN4, DSG1), fatty acid metabolism (CPT1A, ACADSB), glycolysis (PFKL), ketogenesis (HMGCL, HMGCS2, ACAT1), lactate/pyruvate (LDHA), oxidative stress (NQO1), tissue growth (AKT3, EGFR, EREG, IGFBP5, IRS1) and the urea cycle (SLC14A1) were considered in this study. Overall, genes related to fatty acid metabolism (ACADSB) and growth and development (AKT3 and IGFBP5) had a tendency for a treatment × day on trial interaction effect. These profiles may be indicators of rumen epithelial adaptations in response to changes in diet. In conclusion, these results indicate that changes in the composition of the diet can alter the expression of genes with specific functions in rumen epithelial metabolism.

Effects of supplementing a Saccharomyces cerevisiae fermentation product during the transition period on rumen fermentation of dairy cows fed fresh diets differing in starch content

The objective of this study was to evaluate the effects of supplementing a Saccharomyces cerevisiae fermentation product (SCFP; NutriTek, Diamond V, Cedar Rapids, IA) during the transition period (d -28 ± 3 to 23 ± 3 relative to calving) on rumen fermentation and mRNA abundance of genes in the rumen epithelium of fresh cows (d 1 to 23 ± 3 after calving) fed diets differing in starch content. Eighteen ruminally cannulated multiparous Holstein cows were fed diets with SCFP (n = 9) or without (CON; n = 9) throughout the experiment. All cows were fed a common basal controlled-energy close-up diet (1.43 Mcal/kg, net energy for lactation; 13.8% starch) before calving. Cows within each treatment (CON or SCFP) were fed either a low-starch (LS; 22.1% starch) or high-starch (HS; 28.3% starch) diet during the fresh period. Cows were assigned to treatment after balancing for parity, body condition score, and expected calving date. Rumen pH was measured continuously for 72 h starting on d -10, -3, 1, 7, and 21 relative to calving date. Rumen papillae were collected on d -10 and 21 relative to calving. Supplementation of SCFP had no effect on rumen pH during d -10 to -8, but mean rumen pH tended to be higher (6.64 vs. 6.49) for SCFP cows than for CON cows during d -3 to -1. Feeding SCFP decreased the range of rumen pH variation compared with CON within the HS group during both d 7 to 9 (1.08 vs. 1.38) and d 21 to 23 (1.03 vs. 1.30) after calving. In addition, nadir rumen pH tended to be higher (5.64 vs. 5.44) and duration of pH below 5.8 tended to be shorter (116 vs. 323 min/d) for the SCFP group than for the CON group during d 21 to 23 after calving. Supplementation of SCFP increased the mRNA abundance of insulin-like growth factor-6 (1.10 vs. 0.69) before calving and decreased the mRNA abundance of putative anion transporter isoform 1 (1.12 vs. 2.27) after calving. Nadir rumen pH tended to be higher during d 1 to 3 (5.63 vs. 5.41) for LS cows than for HS cows, but rumen pH was not affected by dietary starch content during other time periods. Dietary starch content had no effect on mRNA abundance of genes in the rumen epithelium after calving. These results suggest that supplementation of SCFP may reduce the range of variation in rumen pH in fresh cows fed HS diets and the duration of subacute ruminal acidosis by the end of the fresh period regardless of dietary starch content and that decreasing dietary starch content during the fresh period may reduce the decrease in rumen pH immediately after parturition.

Effect of exogenous butyrate on the gastrointestinal tract of sheep. I. Structure and function of the rumen, omasum, and abomasum

The aim of this study was to determine the effect of exogenous butyrate on the structure and selected functions of the stomach in sheep. Eighteen rams (30.8 ± 2.1 kg; 12 to 15 mo of age) were allocated to the study and fed a diet for 14 d without (CTRL) or with sodium butyrate (BUT; 36 g/kg of offered DM). Neither DMI nor initial BW differed between treatments (P ≥ 0.61), but final BW was greater for BUT compared with CTRL (P = 0.03). Butyrate concentration in the reticuloruminal fluid and abomasal digesta was greater for BUT compared with CTRL (P ≤ 0.01), but total short-chain fatty acids (SCFA) concentration, as well as concentration of other SCFA, did not differ between treatments (P ≥ 0.07). Relative to BW, reticuloruminal tissue mass tended (P = 0.09) to be greater and omasal digesta was less (P = 0.02) for BUT compared with CTRL. Dietary butyrate did not affect ruminal papillae length, width, and density nor did it affect ruminal epithelium thickness (P ≥ 0.12) in the ventral sac of the rumen. However, the DM of ruminal epithelium (mg/cm2) tended (P = 0.06) to be greater for BUT compared with CTRL. Omasal and abomasal epithelium thicknesses were greater (P ≤ 0.05) for BUT compared with CTRL. Mitosis-to-apoptosis ratio in the abomasal epithelium was less for BUT compared with CTRL (P = 0.04). Finally, the mRNA expression of peptide transporter 1 in the omasal epithelium was less (P = 0.02) and mRNA expression of monocarboxylate transporter 1 in the abomasal epithelium tended (P = 0.07) to be greater for BUT compared with CTRL. It can be concluded that exogenous butyrate supplementation affected not only the rumen but also omasum and abomasum in sheep.

Effects of a Change from an Indoor-Based Total Mixed Ration to a Rotational Pasture System Combined With a Moderate Concentrate Feed Supply on Rumen Fermentation of Dairy Cows

Simple Summary

In temperate climate zones, cows are in spring traditionally transitioned from a silage and concentrate- ration to a pasture-based ration. This transition requires complex nutritional and metabolic adaptions for the cow, resulting in a lower feed intake with consequences on energy metabolism. Normally concentrate feed is supplied to support the cows after transition to pasture. Depending on weather influences and growing stage, grass contains high amounts of fast fermentable carbohydrates and low amounts of physical effective fiber. In a previous trial, pasture feeding combined with low amounts of concentrate supply did not prevent an energy shortage after transition to pasture but led to changes in ruminal fermentation patterns indicating a possible risk for rumen health. However, the impact of ration change has not been extensively researched so far when moderate concentrate feed was supplied moderately in order to prevent an energy deficiency. To investigate the influences different rumen variables were documented, using continuous pH measuring devices and weekly diurnal fermentation assessments in rumen fistulated animals. Influence on rumen epithelial morphology was measured by the collection of rumen papillae biopsies and subsequent surface area, as well as histopathological analyses. With the help of this data, a greater understanding of the adaption period of the animals during transition from confinement to pasture is made possible.

Abstract

In spring, transition from a total mixed ration (TMR) to pasture requires rumen adaptions for the cow. It had been shown that transition period does not necessarily mean an increased risk for subacute ruminal acidosis (SARA). After adaption to pasture, however, supplying low amounts of concentrate did indicate increased risk, but caused no adverse effects on rumen morphology and absorption capacity. The present study aimed to investigate the effect of transition, and how a supply of 4.5 kg dry matter concentrate·cow⁻¹·day⁻¹ during fulltime grazing influenced different rumen parameters. During a 12-week trial eleven rumen-cannulated dairy cows were observed during transition from confinement to pasture (PG; n = 6) and compared to cows fed TMR indoors (CG; n = 5). The CG stayed on a TMR based ration (35% corn silage, 35% grass silage, 30% concentrate; dry matter basis), whereas the PG slowly switched to a pasture-based ration (week 0 and 1 = TMR, week 2 = TMR and 3 h pasture·day⁻¹, week 3 and 4 = TMR and 12 h pasture·day⁻¹, and week 5 to 11 = pasture combined with 4.5 kg DM concentrate·cow⁻¹·day⁻¹). Papillae surface area decreased during transition and increased again during fulltime grazing, while the fractional absorption rate of volatile fatty acids (VFA) was not influenced. This suggests only a limited effect of papillae surface area on VFA absorption rate. Feeding changes resulted in different fermentation profiles of VFA. Changing ratio of starch to sugar during transition to fulltime grazing plus concentrate supply did not lead to lower rumen pH. In conclusion, the concentrate supply combined with high fermentable grass during fulltime grazing increased papillae surface area but did not affect absorption rate or rumen pH, so that risk for SARA was not increased.

Morphological adaptation of sheep's rumen epithelium to high-grain diet entails alteration in the expression of genes involved in cell cycle regulation, cell proliferation and apoptosis

Background

The objectives of this study were to characterize changes in the relative mRNA expression of candidate genes and proteins involved in cell cycle regulation, cell proliferation and apoptosis in the ruminal epithelium (RE) of sheep during high-grain (HG) diet adaptation.

Results

Twenty sheep were assigned to four groups with five animals each. These animals were assigned to different periods of HG diet (containing 40% forage and 60% concentrate mix) feeding. The HG groups received an HG diet for 7 (G7, n = 5), 14 (G14, n = 5) and 28 d (G28, n = 5), respectively. In contrast, the control group (CON, n = 5) was fed the forage-based diet for 28 d. The results showed that HG feeding linearly decreased (P <  0.001) the ruminal pH, and increased the concentrations of ruminal total volatile fatty acid (linear, P = 0.001), butyrate (linear, P <  0.001), valerate (quadratic P = 0.029) and the level of IGF-1 (quadratic, P = 0.043) in plasma. The length (quadratic, P = 0.004), width (cubic, P = 0.015) and surface of the ruminal papillae (linear, P = 0.003) were all enlarged after 14 d of HG diet feeding. HG feeding cubically increased the number of cell layers forming the stratum corneum (SC, P <  0.001) and the thickness of the SC (P <  0.001) and stratum basale (P <  0.001). The proportion of basal layer cells in the RE decreased (linear, P <  0.001) in the G0/G1-phase, but it increased linearly (P = 0.006) in the S-phase and cubically (P = 0.004) in the G2/M-phases. The proportion of apoptosis cells in G7, G14 and G28 was reduced compared to the CON (quadratic, P < 0.001). HG diet feeding linearly decreased the mRNA expression of Cyclin E1 (P = 0.021) and CDK-2 (P = 0.001) and (P = 0.027) the protein expression of Cyclin E1. Feeding an HG diet linearly increased the mRNA expression of genes IGFBP-2 (P = 0.034) and IGFBP 5 (P < 0.009), while linearly decreasing (P < 0.001) the IGFBP 3 expression. The expression of cell apoptosis gene Caspase 8 decreased (quadratic, P = 0.012), while Bad mRNA expression tended to decrease (cubic, P = 0.053) after HG feeding.

Conclusions

These results demonstrated sequential changes in rumen papillae size, cell cycle regulation and the genes involved in proliferation and apoptosis as time elapsed in feeding a high-grain diet to sheep.

Electronic supplementary material

The online version of this article (10.1186/s40104-018-0247-z) contains supplementary material, which is available to authorized users.

Microanatomy of the digestive tract, hooves and some visceral organs of addax antelope (Addax nasomaculatus) following a concentrate or forage feeding regime

Subacute ruminal acidosis is a common disease in captive non-domesticated ruminants and is mainly diagnosed by rumen fluid pH and rumen histology. Furthermore, differences in ruminant gastrointestinal histology have been hypothesized to correlate with the browser-grazer continuum. Twelve surplus addax antelope (Addax nasomaculatus) were divided into two groups, fed either their usual diet, consisting of a concentrate feed with a limited amount of hay, or a diet of unlimited hay only, for 3 months. After culling, descriptive and morphometric histology and pH measurements were compared between groups. Significant variations in cellular subpopulations were noted between groups, with roughage-fed individuals presenting primarily with balloon cells of the Stratum corneum and living layer cell vacuolization, whereas parakeratosis and intermediate-type cells were more frequent in the concentrate-fed group. Lesions typical of subacute ruminal acidosis were significantly more pronounced in concentrate-fed individuals. Ruminal pH measurements did not differ significantly, but were more consistent in forage-fed individuals, indicating a more stable reticuloruminal environment. The results indicate that ruminal histology may be more appropriate in assessing ruminal health compared to a single post-mortem pH measurement. It is proposed that Stratum corneum balloon cells may indicate cell maturation and not, as previously assumed, hyperfunction. Concentrate-fed individuals scored higher on the presence of inflammatory cells on hoof corium histology. The study further emphasizes the adaptability of ruminant digestive tract microanatomy in adult animals even after a short period of time and the positive effects an increased roughage diet may have in populations of captive grazing ruminants.

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.

Consequences of dietary energy source and energy level on energy balance, lactogenic hormones, and lactation curve characteristics of cows after a short or omitted dry period

Omitting the dry period (DP) generally reduces milk production in the subsequent lactation. The aim of this study was to evaluate the effect of dietary energy source-glucogenic (G) or lipogenic (L)-and energy level-standard (std) or low-on milk production; energy balance (EB); lactogenic hormones insulin, insulin-like growth factor 1 (IGF-1), and growth hormone (GH); and lactation curve characteristics between wk 1 and 44 postpartum in cows after a 0-d or 30-d DP. Cows (n = 110) were assigned randomly to 3 transition treatments: a 30-d DP with a standard energy level required for expected milk yield [30-d DP(std)], a 0-d DP with the same energy level as cows with a 30-d DP [0-d DP(std)], and a 0-d DP with a low energy level [0-d DP(low)]. In wk 1 to 7, cows were fed the same basal ration but the level of concentrate increased to 6.7 kg/d for cows fed the low energy level and to 8.5 kg/d for cows fed the standard energy level in wk 4. From wk 8 postpartum onward, cows received a G ration (mainly consisting of corn silage and grass silage) or an L ration (mainly consisting of grass silage and sugar beet pulp) with the same energy level contrast (low or std) as in early lactation. Cows fed the G ration had greater milk, lactose, and protein yields, lower milk fat percentage, greater dry matter and energy intakes, and greater plasma IGF-1 concentration compared with cows fed the L ration. Dietary energy source did not affect EB or lactation curve characteristics. In cows with a 0-d DP, the reduced energy level decreased energy intake, EB, and weekly body weight gain, but did not affect milk production or lactation curve characteristics. A 30-d DP resulted in a greater total predicted lactation yield, initial milk yield after calving, peak milk yield, energy intake, energy output in milk, days to conception [only when compared with 0-d DP(low)], plasma GH concentration [only when compared with 0-d DP(std)], and decreased weekly body weight gain compared with a 0-d DP. A 30-d DP decreased both the increasing and the declining slope parameters of the lactation curve and the relative rate of decline in milk yield (indicating greater lactation persistency) compared with a 0-d DP, and decreased plasma insulin and IGF-1 concentration, and EB. In conclusion, feeding a G ration after wk 7 in milk improved energy intake and milk production, but did not affect EB compared with an L ration. For cows without a DP, a reduced dietary energy level did not affect milk production and lactation curve characteristics, but did decrease EB and weekly body weight gain. A 30-d DP increased milk yield and lactation persistency, but decreased milk fat and protein content, EB, and plasma insulin and IGF-1, compared with a 0-d DP.

The effect of dry period length and postpartum level of concentrate on milk production, energy balance, and plasma metabolites of dairy cows across the dry period and in early lactation

Shortening or omitting the dry period (DP) improves energy balance (EB) in early lactation because of a reduction in milk yield. Lower milk yield results in lower energy demands and requires less energy intake. The aim of this study was to evaluate the effects of DP length and concentrate level postpartum on milk yield, feed intake, EB, and plasma metabolites between wk -4 and 7 relative to calving of cows of second parity or higher. Holstein-Friesian dairy cows (n = 123) were assigned randomly to 1 of 2 DP lengths: 0-d DP (n = 81) or 30-d DP (n = 42). Prepartum, cows with a 0-d DP received a lactation ration based on grass silage and corn silage (6.4 MJ of net energy for lactation/kg of dry matter). Cows with a 30-d DP received a dry cow ration based on grass silage, corn silage, and straw (5.4 MJ of net energy for lactation/kg of dry matter). Postpartum, all cows received the same basal lactation ration as provided to lactating cows prepartum. Cows with a 0-d DP were fed a low level of concentrate up to 6.7 kg/d based on the requirement for their expected milk yield (0-d DP-L; n = 40) or the standard level of concentrate up to 8.5 kg/d (0-d DP-S; n = 41), which was equal to the concentrate level for cows with a 30-d DP (30-d DP-S; n = 42) based on requirements for their expected milk yield. Prepartum dry matter intake, concentrate intake, basal ration intake, energy intake, plasma β-hydroxybutyrate (BHB), and insulin concentrations were greater and plasma free fatty acids (FFA) and glucose concentrations were lower, but EB was not different in cows with a 0-d DP compared with cows with a 30-d DP. During wk 1 to 3 postpartum, milk fat yield and plasma BHB concentration were lower and dry matter intake and concentrate intake were greater in cows with a 0-d DP compared with cows with a 30-d DP. During wk 4 to 7 postpartum, fat- and protein-corrected milk (FPCM), lactose content, and lactose and fat yield were lower in 0-d DP-L or 0-d DP-S cows compared with 30-d DP-S cows. Basal ration intake, EB, body weight, plasma glucose, and insulin and insulin-like growth factor-1 concentrations were greater and plasma FFA and BHB concentrations were lower in 0-d DP-L and 0-d DP-S cows compared with 30-d DP-S cows. Concentrate and energy intake were lower in 0-d DP-L cows than in 0-d DP-S or 30-d DP-S cows. Milk yield and concentrations of plasma metabolites did not differ in wk 4 to 7, although EB was lower in wk 6 and 7 postpartum in 0-d DP-L cows than in 0-d DP-S cows. In conclusion, a 0-d DP reduced milk yield and improved EB and metabolic status of cows in early lactation compared with a 30-d DP. Reducing the postpartum level of concentrate of cows with a 0-d DP did not affect fat- and protein-corrected milk yield or plasma FFA and BHB concentrations in early lactation but did reduce EB in wk 6 and 7 postpartum.