Morphological and functional development of the rumen in the calf: influence of the time of weaning. 1. Morphological development of rumen mucosa

Effects of supplementation with Saccharomyces cerevisiae products on dairy calves: A meta-analysis

Saccharomyces cerevisiae products (SCP) have the potential to promote the growth and development of the gastrointestinal tract and immunity in young livestock animals. However, the effects of SCP supplementation on calves are inconsistent among the reported studies in the literature. Hence, we performed a meta-analysis to comprehensively assess the effects of SCP on the growth performance, ruminal fermentation parameters, nutrients digestibility, ruminal histological morphology, serum immune response, and fecal pathogen colony counts in calves. We searched the Web of Science, ScienceDirect, PubMed, and China National Knowledge Infrastructure for relevant studies published up to October 1, 2021. After screening against a set of criteria, the data of 36 studies were included in our meta-analysis (2,126 calves in total). We evaluated the quality of the data using sensitivity analysis and assessed publication bias. Our meta-analysis revealed several important findings. First, SCP supplementation increased the ruminal short-chain fatty acid concentration, ruminal papilla height, and fiber digestibility, pointing toward stimulation of the development of the rumen in calves. Second, SCP supplementation increased the serum concentrations of total protein, IgA, and IgG but decreased fecal pathogen colony counts, suggesting that SCP could help calves to promote immunity (especially maintaining circulating concentrations of immunoglobulins in preweaning calves) and resistance to pathogens. Third, a subgroup analysis between preweaning and postweaning calves showed that SCP increased average daily gain and dry matter intake preweaning but not postweaning, suggesting that SCP is better supplemented to preweaning calves to achieve the best results. Forth, based on the dose-response curve, 24 to 25 g/d might be the optimal dose range of SCP supplementation (into starter feed) preweaning to achieve the best overall effect, meanwhile, we need more studies to improve the consistency and accuracy of the dose-response curve prediction. Overall, SCP supplementation improved growth performance, rumen development, and immunocompetence in calves, particularly in preweaning calves.

Review of Strategies to Promote Rumen Development in Calves

Simple Summary

The rumen is an important digestive organ that plays a key role in the growth, production performance and health of ruminants. Promoting rumen development has always been a key target of calf nutrition. Current research reveals that an early feeding regime and nutrition have effects on rumen development and the establishment of rumen microbiota. The effects may persist for a long time, and consequently, impact the lifetime productive performance and health of adult ruminants. The most sensitive window for rumen manipulation may exist in the postnatal and weaning period. Thus, the early feeding regime and nutrition of calves deserve further research. The establishment of the rumen bacterial community is a mysterious and complex process. The development of microbial 16S rDNA gene sequencing and metagenome analysis enables us to learn more about the establishment of rumen microbes and their interactions in host gastrointestinal (GI) tract development.

Abstract

Digestive tract development in calves presents a uniquely organized system. Specifically, as the rumen develops and becomes colonized by microorganisms, a calf physiologically transitions from a pseudo-monogastric animal to a functioning ruminant. Importantly, the development of rumen in calves can directly affect the intake of feed, nutrient digestibility and overall growth. Even minor changes in the early feeding regime and nutrition can drastically influence rumen development, resulting in long-term effects on growth, health, and milk yields in adult cattle. Rumen development in newborn calves is one of the most important and interesting areas of calf nutrition. This paper presents a comprehensive review of recent studies of the gastrointestinal (GI) tract development in calves. Moreover, we also describe the effect of the environment in shaping the GI tract, including diet, feed additives and feeding management, as well as discuss the strategies to promote the physiological and microbiological development of rumen.

Age-associated changes of the intrinsic nervous system in relation with interstitial cells in the pre-weaning goat rumen

In this study, we investigated the neural changes and their relationships with interstitial cells (ICs) in the rumen of pre-weaning goats by transmission electron microscopy, western blot and immunofluorescence (antibody: general neuronal marker-Protein Gene Product (PGP9.5)/ IC marker-vimentin). The immunofluorescence results showed that PGP9.5-positive reaction was widely distributed in neuronal soma (NS) and nerve fibre (NF). The NSs were observed in the ganglia of the myenteric plexus (MP) but not in the submucosal plexus. The mean optical density (MOD) of the whole of PGP9.5-positive nerves and the protein expression level of PGP.5 in the rumen wall both decreased significantly with age. However an obvious increase MOD of PGP.5-positive NFs within the rumen epithelium were observed. In the MP, the nerves and ICs were interwoven to form two complex networks that gradually tightened with age. Furthermore, NSs and nerve trunks were surrounded by a ring-boundary layer consisting of several ICs that became physically closer with aging. Moreover, ICs were located nearby NFs within the ML, forming connections between ICs, smooth muscle cells and axons. This study describes the pattern of neural distribution and its association with ICs in the developing rumen which shed light on the postpartum development of ruminants.

Weaning Ages Do Not Affect the Overall Growth or Carcass Traits of Hu Sheep

This study aimed to determine effects of weaning ages on growth, rumen development, and carcass characteristics and meat quality of Hu lambs. Thirty male Hu lambs were randomly divided into two weaning age groups: Weaned at 30 (W30) or 45 (W45) d of age. Blood samples were collected on the day of weaning before lambs (n = 5) were slaughtered, and then rumen sample was collected immediately after they were slaughtered. The intake of all feeds increased with age (p < 0.05), but were not affected by weaning age (p > 0.05). Oxidative stress indicators and immune variables, the plasma biochemical parameters did not differ between the two different weaning ages (p > 0.05). The two weaning age groups also had similar (p > 0.05) concentration of ruminal total volatile fatty acid. The two weaning age groups did not differ in body weight, carcass characteristics, or meat quality (p > 0.05) at d 120. These results indicate that weaning half a month earlier than the typical weaning age does not significantly affect the growth, ruminal development, or carcass characteristics of Hu lambs, and they can be weaned at 30 d of age to improve production efficiency.

Growth performance and rumen development in Malabari kids reared under different production systems

In order to investigate the effect of rearing systems on growth and rumen development in Malabari male kids, 14 pre-weaned Malabari male kids of uniform morphological characters were randomly divided into two equal groups as T₁ and T₂. Both the groups were reared intensively for 12 weeks whereby kids under T₁ group were allowed to suckle their dams and provided green grass ad libitum. The kids under T₂ were weaned at the age of 7 days and provided formulated semi-solid broiler goat concentrate diet through the feeding bottle and were not offered any grass/roughage. Parameters like live weight gain, daily weight gain and body measurements were studied to evaluate the growth performance. However, gastrointestinal tract morphometric studies and qualitative morphological analysis of rumen papillae were undertaken to measure the rumen development. The daily weight gain of kids under T₂ was significantly (P ≤ 0.01) higher than the daily weight gain of kids under T₁. Also, the body measurements like height at withers, heart girth and body length were significantly (P ≤ 0.01) higher in T₂ than in T₁. The rumen and abomasum were comparatively more developed in T₂ than in T₁. The morphology of rumen papillae in both groups was different in size, shape and colour. The length, width, density and surface area of rumen papillae among kids in T₂ were significantly (P ≤ 0.01) higher than those kids in T₁. The results of the present study indicated that the feeding of semi-solid broiler goat concentrate diet improved growth performance and early rumen development in kids.

Effect of the supplementation with a blend containing short and medium chain fatty acid monoglycerides in milk replacer on rumen papillae development in weaning calves

Feeding of neonates with artificial milk formulas is a popular trend toward early weaning of newborn dairy calves. These milk replacers (MR) should accelerate the rumen development, determining early solid feed intake and leading to better performances in cattle. Previous research demonstrated that sodium butyrate supplementation in MR can affect both small intestine and rumen development. Also acetate and propionate showed similar properties, while only a few studies indicate some potential benefit of monoglycerides on gut functions. The present study is aimed to determine the effect of the supplementation of a blend containing short and medium chain fatty acids monoglycerides (SMCFA) in milk replacer on rumen papillae development and growth performances in weaning calves. Twenty bull calves (about 2 weeks old, weighing around 43kg) were randomly allocated into two groups: control (C) and treated (T). Besides MR and starter diet, the latter offered at libitum, T calves received 0.2% SMCFA in MR. Animals were slaughtered after 56 days from the beginning of the trial. No difference was found between groups either in growth performances or in mean number of papillae/cm(2) of mucosa, total surface of papillae (mm(2))/cm(2) of mucosa or papillary size. In both groups, the morphology of the rumen epithelium was typical of parakeratosis. The cells of the stratum spinosum were directly transformed into swollen, ovoid, still nucleated keratinocytes, particularly at the papillary tip, probably as a result of unphysiological osmolarities caused by high concentrate intake. Degenerated squamous horn cells covered the "balloon like" cells forming several layers, particularly in the places of the rumen mucosa more protected from an abrasive action of solid feed. This was more evident in C animals. The squamous cells covering the papillary tip showed cytoplasmic protrusion, representing remains of the attachment sites of desmosomes, which increased the total absorptive surface and were more numerous and higher in T compared to C animals. It might be hypothesized that SMCFA supplementation in MR could better regulate epithelial cell proliferation and probably have an "emollient effect" leading to an easier "peeling" that might increase efficiency for nutrient transport across the epithelium.

Rumen fluid inhibits proliferation and stimulates expression of cyclin-dependent kinase inhibitors 1A and 2A in bovine rumen epithelial cells

It has been known for decades that microbial fermentation within the rumen is critical to postnatal rumen epithelial growth and maturation in ruminants, but the underlying mechanism is largely unknown. In this study, we determined the effect of rumen fluid, which should contain all products from rumen fermentation, on growth of rumen epithelial cells in vitro. Addition of 10% rumen fluid from cows to the culture medium inhibited (P < 0.05), whereas addition of 6.5 mM acetate, 2.5 mM propionate, or 1 mM butyrate had no effect (P > 0.1) on, the proliferation of rumen epithelial cells isolated from newborn calves. Flow cytometric assays showed that 10% rumen fluid inhibited (P < 0.05) the transition of rumen epithelial cells from the G1 phase to the S phase during the cell cycle. Real-time RT-PCR analyses of mRNA for key cell cycle regulators indicated that 10% rumen fluid did not change (P > 0.1) the expression of cyclin D1, D2, D3, E1, or E2 mRNA or that of cyclin-dependent kinase inhibitor 1B or 2B mRNA, but increased (P < 0.05) the expression of cyclin-dependent kinase inhibitors 1A and 2A mRNA in rumen epithelial cells. These mRNA data support the possibility that rumen fluid inhibits proliferation of rumen epithelial cells in vitro by increasing the expression of cyclin-dependent kinase inhibitors 1A and 2A. The result that rumen fluid inhibits proliferation of bovine rumen epithelial cells in culture indicates that rumen fermentation does not stimulate the postnatal rumen epithelial growth in cattle by directly stimulating proliferation of rumen epithelial cells.

Investigation of calf health and welfare on dairy farms in south-west England

A questionnaire was designed to investigate calf health and welfare on dairy farms in the south west of England with regard to the degree of compliance with the Welfare of Farmed Animals (England) Regulations 2000. The level of veterinary involvement in calf rearing and management on dairy farms in the south west of England was also assessed. The questionnaire was sent to 32 large animal practices in the catchment area of the Veterinary Laboratories Agency--Langford. Compliance with the regulations was found to be variable. The requirements for the isolation of sick calves, provision of bovine colostrum within six hours of birth, the provision of fresh, clean water and restrictions concerning tethering were not well complied with. However, the requirements for twice-daily feeding and inspection, visual and tactile contact between calves, access to forage and the provision of clean, dry bedding were well complied with. The results also suggested that there was some lack of veterinary input into the health and welfare of calves on dairy farms visited by the practices routinely and non-routinely.

An energy-rich diet causes rumen papillae proliferation associated with more IGF type 1 receptors and increased plasma IGF-1 concentrations in young goats

We tested the hypothesis that the dietary energy-dependent alterations of the rumen papillae size are accompanied by corresponding changes in systemic insulin-like growth factor (IGF)-1 concentration and in rumen papillary IGF type 1 receptors (IGF-1R). Young male goats (n=24) were randomly allocated to two groups (n=12) and fed a high level (HL) metabolizable energy [1200 kJ/(kg(0.75).d)] or a low level (LL) [500 kJ/(kg(0.75).d)] diet for 42 d. The concentration of ruminal total SCFA did not differ between the groups, but the molar proportion of butyric acid was enhanced by 70% in the HL group (P<0.05). Both the length and width of the papillae were greater (P<0.05) in the HL group, and the surface was 50-100% larger (P<0.05) in the tissue sampled from the artrium ruminis, the ventral ruminal sac and the ventral blind sac. Transport of Na+ across the rumen epithelium, which is amiloride sensitive, was higher (P<0.05) in the HL than in the LL group. Furthermore, the plasma IGF-1 concentration was about twofold higher in the HL group (P<0.05), and the maximal rumen epithelial IGF-1R binding was also higher in the HL (P<0.05) than in the LL group. IGF-1R mRNA and IGF-1 mRNA were detected in rumen papillae; however, they were unaffected by dietary treatments. DNA synthesis and cell proliferation of cultured rumen epithelial cells were higher (P<0.05) after IGF-1 treatment (25 or 50 microg/L) compared with those in the medium without IGF-1. Thus dietary energy-dependent alterations of rumen morphology and function are accompanied by corresponding changes in systemic IGF-1 and ruminal IGF-1R.

Research note: Postnatal development of electrolyte transport in calf rumen as affected by weaning time

In a previous study we found a positive correlation between early weaning in calves and morphological parameters which were indicative of ruminal development, i.e. the length and width of the papillae. The objective of the present study was to determine to what extent this observation could be reflected by modulations of absorptive and secretory functions of the rumen mucosa. For this purpose the short-circuit currents (Isc) as a measure of electrogenic net ion fluxes and the transepithelial conductances (G(T)) as a measure of the overall tissue permeability were measured in vitro applying the Ussing-chamber technique. Simultaneously, the unidirectional flux rates of sodium and chloride across rumen wall epithelia were determined in the absence of electrochemical gradients. Under these conditions, significant positive net flux rates (Jnet) clearly indicate active mechanisms for electrolyte absorption. For the experiments 12 male Holstein calves 7 d of age were assigned to three groups of 4 animals each: milk group (I, slaughtered after 6 weeks of age), late weaning group (II, slaughtered after 9 weeks of age) and early weaning group (II, weaned after 6 weeks of age and slaughtered after 9 weeks of age). Whereas G(T) values remained unaffected by different age and feeding, Isc values were significantly affected by early weaning but were not influenced by age. Irrespective of weaning time active absorption of Na+ tended to be higher by about 60% in 9 weeks old animals. Active absorption of chloride was significantly increased in milk fed 9 weeke old calves and this effect was further stimulated by early weaning. In conclusion, the data show an increasing active Na+ absorption with age in calf rumen that could not be influenced by early weaning. Similarly, active Cl- absorption was initially increased during postnatal development and this effect could be stimulated further by early weaning.

Butyric acid stimulates rumen mucosa development in the calf mainly by a reduction of apoptosis

In ruminants the stimulation of papillar growth by butyric acid is well described but effects on mitosis and apoptosis are not known. To clarify the effect of short chain fatty acids three groups of three calves received a basic ration of 100 g hay per day for 6 weeks and additionally milk replacer. From these, two groups were fed with increasing amounts of the salts of either propionic acid (53 to 390 g) or butyric acid up to (54 to 326 g). The control group instead received an additional isocaloric amount of milk replacer. Mitosis was characterized by Ki67 immunoreactivity, apoptosis by a modified TUNEL assay and by electron microscopy. The feeding regimes led to significant differences of papillar length, increasing from 1.0 mm (controls) to 2.2 mm (propionic acid) and 4 mm (butyric acid). This enlargement was partly explained by an increased mitotic rate for the two fatty acid groups. The difference between the fatty acid groups was mainly explained by different apoptotic rates which were only one third for butyric acid compared to propionic acid (P < 0.001). In conclusion, butyric acid is a specific inhibitor of ruminal apoptosis in vivo.