Development of microbial activity in the alimentary tract of lambs

Utilizing the Gastrointestinal Microbiota to Modulate Cattle Health through the Microbiome-Gut-Organ Axes

The microorganisms inhabiting the gastrointestinal tract (GIT) of ruminants have a mutualistic relationship with the host that influences the efficiency and health of the ruminants. The GIT microbiota interacts with the host immune system to influence not only the GIT, but other organs in the body as well. The objective of this review is to highlight the importance of the role the gastrointestinal microbiota plays in modulating the health of a host through communication with different organs in the body through the microbiome-gut-organ axes. Among other things, the GIT microbiota produces metabolites for the host and prevents the colonization of pathogens. In order to prevent dysbiosis of the GIT microbiota, gut microbial therapies can be utilized to re-introduce beneficial bacteria and regain homeostasis within the rumen environment and promote gastrointestinal health. Additionally, controlling GIT dysbiosis can aid the immune system in preventing disfunction in other organ systems in the body through the microbiome-gut-brain axis, the microbiome-gut-lung axis, the microbiome-gut-mammary axis, and the microbiome-gut-reproductive axis.

Feed efficiency phenotypes in lambs involve changes in ruminal, colonic, and small-intestine-located microbiota

Several studies have revealed differences in rumen-located microbes between greatly efficient and inefficient animals; however, how the microbiota vary in the hind gastrointestinal tract (GIT) has only been sparsely explored and how they vary in the small intestine remains to be determined. We therefore sampled the microbiota of the duodenum, jejunum, ileum, colon, and colorectally-obtained feces, in addition to the rumen of 12 lambs that, in a residual feed intake trial, were found to be at either extreme of feed efficiency phenotypes. The 16S rRNA gene (V3-V4 region) profiles of all samples were analyzed and revealed unique microbiota in all GIT locations except the jejunum and ileum (ANOSIM > 0.2, < 0.001). Measures of β-diversity revealed greater dissimilarity between more anatomically distant GIT locations (e.g., Rumen-Duodenum, ANOSIM = 0.365, < 0.001; Rumen-Colon, ANOSIM = 1, < 0.001) with the nearest distal region typically more similar than the nearest proximal location. The relative abundances of 13 operational taxonomic units (OTUs) from the duodenum, jejunum, colon, and feces, as well as the rumen, differed between efficient and inefficient animals (Bonferroni corrected, < 0.05), while another 2 OTUs trended toward significance. These OTUs were classified as taxa with known roles in fibrolysis (Fibrobacteres, Ruminococcaceae, and Saccharofermentans) and others that are commonly associated with health (Bifidobacteriaceae, and Christensenellaceae) and dysbiosis (Proteobacteria). Our findings show biospatial delineations of microbiota throughout the GIT and suggest that feed efficiency extends beyond the rumen, transcending these regions, and involves increases in both rumen- and colon-located fibrolytic taxa, increases in bifidobacterial species in the small intestine, and reductions in small intestine and distal GIT-located Proteobacteria.

Gastrointestinal tract microbiota and probiotics in production animals

The gastrointestinal tract (GIT) microbiomes of production animals are now firmly established as a key feature underscoring animal health, development, and productivity. In particular, early gut colonization is critically important to the morphological and immunological development of the GIT, development of a functional fermentative environment, and neonatal resistance to pathogenic challenge. Although perturbations of an animal's GIT microbiome at any age can have profound consequences, perturbations during early GIT development can be particularly severe and result in significant and long-lasting sequelae. As the GIT microbiome matures, it exhibits significant diversity, ostensibly an important indicator of ecosystem health. Recognition of the immense importance of the GIT microbiota to the host has led to the development of probiotic and prebiotic feedstuffs with the express aim of ensuring animal health. We herein review the current collective understanding of the GIT microbiota of production animals.

Influence of experience on intake and feeding behavior of dairy sheep when offered forages from woody plants in a multiple-choice situation

A satisfactory intake of novel low-quality forages by ruminants may require previous experience with this feed. Therefore, this study tested in sheep whether experience with forages from woody plants had an influence on feed intake, feeding behavior, and nutrient supply when offered in a multiple-choice arrangement. Two sheep experiments were conducted, 1 in Syria (Mediterranean region; Exp. 1) and the other in Switzerland (Central Europe; Exp. 2), that investigated 5 and 6 woody test plants, respectively. In Exp. 1, the test plants were Artemisia herba-alba, Atriplex leucoclada, Haloxylon articulatum, Noaea mucronata, and Salsola vermiculata. In Exp. 2, Betula pendula, Castanea sativa, and Juglans regia were used in addition to A. leucoclada, H. articulatum, and S. vermiculata (the plants most consumed in Exp. 1). In each experiment, 12 lactating sheep (Awassi sheep in Exp. 1 and East Friesian Milk sheep in Exp. 2) were allocated to 2 groups ("experienced" and "naïve"). Experienced sheep subsequently were familiarized with each test plant during a learning period of binary choices (1 test plant vs. barley straw) for 4 h in the morning for 7 d each. The naïve group received only straw. During the rest of the day, a basal diet composed of barley straw (ad libitum) and concentrate was offered to both groups. For the 2 wk following the learning period, the sheep were subjected to feeding of the basal diet to avoid carryover effects of the last offered test plant. In the following multiple-choice period, both groups were allowed to select from all test plants during 4 h in the morning for 14 d. Forage intake after 4 and 24 h and feeding behavior during the first 30 min of the test feeding were assessed. Milk yield and composition were measured at the end of the multiple-choice period. Nutrient intake was calculated using feed intake measurements and compositional analyses. Only in Exp. 2, group differences (P < 0.05) were found on d 1 of the multiple-choice period. The experienced sheep consumed more total forage, straw, OM, NDF, ADF, and ADL (nutrients without concentrate). However, across the entire multiple-choice period, there were no differences (P ≥ 0.05) in forage and nutrient intake, feeding behavior, and milk yield and composition between the groups in both experiments. This suggests that sheep can quickly adapt to previously unknown woody feeds of varying origin and quality offered as dried supplements.

Methane emissions from weaned lambs measured at 13, 17, 25 and 35 weeks of age compared with mature ewes consuming a fresh forage diet

Daily methane (CH4) emissions and dry matter intake (DMI) were measured on 14 mature ewes (3–4 years old) and 13 lambs when the lambs were 13, 17, 25 and 35 weeks of age. During the four CH4 measurement periods, all animals were kept in individual metabolism cages and fed pasture cut daily and fed at 1.5 times maintenance. Feed was offered in equal amounts at 0800 and 1500 hours daily. Methane emissions were measured using the sulfur hexafluoride tracer technique and values reported were the mean of measurement on 4–5 days for each animal. In the intervals between CH4 measurements, ewes and lambs grazed separate paddocks containing predominantly ryegrass. Daily CH4 emissions for the ewes ranged from 21.5 to 22.5 ± 1.50 g/day and were significantly higher than those of the lambs which ranged from 10.7 to 17.5 ± 1.50 g/day. Averaged across all four periods, the overall mean CH4 emission for lambs was 8% lower (P < 0.05) than for ewes (21.9 v. 23.8 ± 0.95 g CH4/kg DMI). However, within each measurement period, the emissions of CH4/kg DMI from lambs was significantly lower (P < 0.05) than those of ewes only in the fourth period when the lambs were 35 weeks of age (17.9 v. 21.9 g/kg DMI for lambs and ewes, respectively). The pasture offered to both ewes and lambs in this period was of higher quality than in the other periods (organic matter digestibility of 80% DM v. 68–71% DM at other times) and CH4 emission per kg DMI was lower in both groups of animals than in the other periods. This study supports the hypothesis that young sheep have lower CH4 emissions per unit of intake than mature animals. However, the age at which the lambs produced similar CH4/kg DMI to adult sheep could not be determined precisely because of the changes in pasture quality between different measurement periods.

Cellular expression of monocarboxylate transporters (MCT) in the digestive tract of the mouse, rat, and humans, with special reference to slc5a8

Short-chain fatty acids (SCFA) are monocarboxylates produced by bacterial fermentation that play a crucial role in maintaining homeostasis in the large intestine. Two major transporters for SCFA, monocarboxylate transporter (MCT) and slc5a8 (or SMCT), exist in the digestive tract. The present histochemical study using in situ hybridization and immunohistochemistry revealed the distribution and subcellular localization of the MCT family in the digestive tract of mice, rats, and humans, comparing these with that of slc5a8. The expression of mucosal MCT1 in the mouse and rat was most intense in the cecum, followed by the colon, but low in the stomach and small intestine. Among other MCT subtypes, only MCT2 was detected in the parietal cell region of the gastric mucosa. Slc5a8 had predominant expression sites in the distal half of the large bowel and in the most terminal ileum. The mucosal MCT1 was localized in the basolateral membrane of enterocytes, while slc5a8 was restricted to the apical cell membrane, suggesting the involvement of slc5a8 in the uptake of luminal SCFA, and of MCT1 in the efflux of SCFA and monocarboxylate metabolites towards blood circulation. The large intestine expressed both types of the transporter, but their distribution patterns differed along the longitudinal axis of the intestine and along the perpendicular axis of the mucosa.

Suitability of electronic mini-boluses for early identification of lambs

Three types of ceramic mini-boluses, B1 [13.8 g; 10.5 x 51.0 mm (o.d. x length)], B2 (16.2 g; 12.2 x 42.2 mm), and B3 (20.1 g; 11.2 x 56.4 mm), were used to electronically identify as soon as possible after birth a total of 545 lambs of 3 breeds: Ripollesa (meat breed, n = 274), Manchega (dairy breed, n = 129), and Lacaune (dairy breed, n = 142). Boluses were administered by a trained operator using a balling gun or directly by hand. Lambs were also identified with 2 types of plastic ear tags in the left (temporary, 1.5 g) and the right (permanent, 4.1 g) ears. Lamb and identification device performances were checked during suckling (to wk 5 or 7) and fattening. At 24 kg of BW, lambs were slaughtered (n = 385) or kept for breeding (n = 144). No differences in performance were observed between the 2 dairy breeds, and their data were pooled. Minimum BW for bolus administration was lower in dairy than in meat lambs (P < 0.001). Across breeds, B1 and B3 did not differ in lamb age (27 d) and weight (9.2 kg) at administration, but B2 required older and heavier lambs (33 d and 11.1 kg; P < 0.01). Boluses did not affect lamb performance, but final readability at slaughter differed between B1 and B2 (97.7 and 95.2%, respectively) and B3 (100%), and between ear tags (temporary, 98.1; permanent, 100%). Bolus recovery was 100% in all cases, but the proportion of boluses found in the reticulum varied among bolus type (83.3 to 93.8%; P < 0.05). Three B1 (2%) were recovered from the abomasum. In a second experiment, effects of the intermediate mini-bolus (B2) on diet digestibility were evaluated. Digestibility of control and bolus-administered, Manchega ram lambs (14.9 kg of BW; n = 8) fed ad libitum with 2 pelleted concentrates and barley straw was assessed in digestibility crates. Feed intake and nutrient digestibility were measured in four 21-d periods, during which lambs received the 2 diets consecutively. No differences in intake, growth performance, or nutrient digestibility were observed between control and bolused lambs. In conclusion, the B3 mini-bolus proved to be an efficient device for identification of lambs before weaning (recommended age, >4 wk; recommended BW, >10 kg), allowing a reliable traceability of dairy and meat lambs until slaughter.

Expression and distribution of monocarboxylate transporter 1 (MCT1) in the gastrointestinal tract of calves

In the present study the expression and distribution of monocarboxylate transporter 1 (MCT1) along the gastrointestinal tract (rumen, reticulum, omasum, abomasum, duodenum, jejunum, ileum, cecum and colon) of calves were investigated on both mRNA and protein levels. The expression of MCT1 protein and its distribution were determined by Western blotting and immunohistochemical staining, respectively by using antibody for MCT1. MCT1 protein was visualized as a 43-kDa band on immunoblots of the membrane proteins prepared from the various regions examined, and it was more highly expressed in forestomach and large intestine than in abomasum and small intestine. With the use of reverse transcriptase-polymerase chain reaction, mRNA encoding for MCT1 was demonstrated in the different tissues examined. The immunohistochemical study confirmed the Western blot findings and showed strong MCT1 immunopositive staining in the stratified squamous epithelia of the forestomach as well as the epithelial cells lining the digestive tract in the cecum, proximal colon, and distal colon. The results suggest that MCT1 may play a role in the transport of SCFA and their metabolites in the gastrointestinal tract of bovines.

16S ribosomal DNA-directed PCR primers for ruminal methanogens and identification of methanogens colonising young lambs

The population densities and identities of methanogens colonising new-born lambs in a grazing flock were determined from rumen samples collected at regular intervals after birth. Methanogen colonisation was found at the first sampling (1-3 days after birth) and population densities reached around 10(4) methanogens per gram at 1 week of age. Population densities increased in an exponential manner to a maximum of 10(8)-10(9) per gram at 3 weeks of age. To identify methanogens, PCR primers specific for each of the Archaea; a grouping of the orders Methanomicrobiales, Methanosarcinales and Methanococcales; the order Methanobacteriales; the order Methanococcales; the order Methanosarcinales; the genus Methanobacterium; and the genus Methanobrevibacter were designed. Primer-pair specificities were confirmed in tests with target and non-target micro-organisms. PCR analysis of DNA extracts revealed that all the detectable ruminal methanogens belonged to the order Methanobacteriales, with no methanogens belonging to the Methanomicrobiales, the Methanosarcinales, or the Methanococcales being detected. In 3 lambs, the initial colonising methanogens were Methanobrevibacter spp. and in 2 lambs were a mixture of Methanobrevibacter and Methanobacterium spp. In the latter case, the initial colonising Methanobacterium spp. subsequently disappeared and were not detectable 12-19 days after birth. Seven weeks after birth, lambs contained only Methanobrevibacter spp. This study, the first to provide information on the identities of methanogens colonising pre-ruminants, suggests that the predominant methanogens found in the mature rumen establish very soon after birth and well before a functioning rumen develops.

Effects of small ruminal boluses used for electronic identification of lambs on the growth and development of the reticulorumen

Fifty-four male lambs were used to study the effects of two types of small electronic boluses on the dimensions and epithelial characteristics of their reticulorumen. Newborn lambs were assigned according to bolus type and age of application to the following treatments: 1) control (C, n = 21), without bolus; 2) mini (M, n = 21), identified with a 9.3 x 37.4-mm, 5.2-g bolus during the first week after birth; and 3) small (S, n = 12), identified with a 15.0 x 39.1-mm, 20-g bolus after weaning at wk 5, when lambs weighed more than 12 kg. After weaning, lambs were given ad libitum access to concentrate and barley straw. Six lambs were euthanized at the start of the experiment to measure initial reticulorumen characteristics. Ten lambs (five from M and five from C treatments) were slaughtered at weaning and 24 (eight per treatment) were slaughtered when they reached 24 kg. After bolus recovery, the reticulorumen was emptied and filled with polyurethane foam to obtain reticulorumen casts. Weight of the emptied reticulorumen and volume of the casts were measured. Four representative lambs from each treatment were also slaughtered at 24 kg, and their reticulorumen used to evaluate papillae size, number of dead cells, and degree of keratinization of both the reticulum wall and the rumen wall epithelia. Weight at weaning (13.8 kg), age at the end of fattening (65 d), and mortality rate (4%) did not differ among treatments. Retention rate for M and S boluses was 82.4 and 100%, respectively. Fresh weight and volume of the reticulorumen did not differ among treatments at weaning (130 g and 1,679 mL) or at the end of the fattening period (640 g and 5,931 mL). Lambs in the M treatment had greater (P < 0.05) rumen papillae size and lower (P < 0.10) keratinization than C lambs; values in the S lambs were intermediate between M and C lambs. Neither the M nor S type of bolus affected dimensions of the reticulorumen, but the earlier presence of M boluses induced a greater papillae size, with no negative effects on health and fattening performances of young lambs.

Leucine degradation in sheep

1. In vitro leucine catabolism in adipose tissue, skeletal muscle, kidney and liver homogenates was studied in sheep. 2. In Expt 1, Suffolk X Targhee ram lambs were slaughtered at 1, 28, 56, 84, 112, 140, 168, 196, 224 and 365 d of age. In Expt 2, 5-month-old crossbred wethers were fed on 80, 120 or 180 g crude protein (nitrogen X 6.25)/kg diets for 4 weeks or fed on 120 g crude protein/kg for 4 weeks and then fasted for 48 or 96 h before slaughter. Leucine catabolism was assayed in tissue homogenates for Expts 1 and 2. 3. Leucine deamination (per unit protein) was highest in skeletal muscle at day 1 and then declined; liver exhibited an activity pattern akin to muscle while kidney activity tended to rise over the duration of the study. Adipose tissue in vitro leucine deamination was higher at all ages studied and 9- to 50-fold higher than all other tissues at 365 d. Leucine decarboxylation (per unit protein) was highest at day 1 in muscle and declined to low levels (P less than 0.01) after 28 d; liver and kidney decarboxylation activities were higher than muscle at all ages with kidney showing the highest activity. Whilst adipose had high initial activity it declined significantly (P less than 0.01) by day 28 and remained low. 4. Dietary protein intake had no effect on leucine deamination in any tissue. Leucine decarboxylation tended to increase with protein intake for all tissues except kidney.(ABSTRACT TRUNCATED AT 250 WORDS)

Successive changes in the epimural bacterial community of young lambs as revealed by scanning electron microscopy

Scanning electron microscopy was used to determine the time of initial colonization of the rumen epithelium of young lambs and successive changes with time in the morphological composition of the epimural community. Tissue samples were obtained from two groups of lambs at 1, 2, 4, 6, 8, and 10 weeks of age. Comparisons were made with the epimural communities observed at 12 well-distributed sites in the rumen of a mature wether. Epimural bacteria were already present on the epithelium at 1 week of age. The morphological composition of the epimural community changed with age, with the pattern of succession being similar in both groups of lambs. A total of 24 morphotypes were distinguished by scanning electron microscopy; 17 were rod shaped, 4 were cocci, 2 were spiral, and 1 was filamentous. These morphotypes were further subdivided into: (i) those persisting after their initial colonization in young lambs and present in the adult (7 morphotypes), (ii) those seen only in the adult (2 morphotypes), and (iii) those present only in young lambs (15 morphotypes). The seven morphotypes present in both the lamb and the adult could be considered indigenous members of the epimural community. Several morphotypes appeared restricted in their colonization to certain regions of the papillae, suggesting the presence of microhabitats within the epithelial habitat. Two rod-shaped bacteria were repeatedly seen specifically attached to one another, suggesting an interspecific association.