Pre-weaned Animals Research Articles

An update on joint ill in sheep.

This focus article has been prepared by Vanessa Swinson of the APHA Small Ruminant Expert Group.

Cryptosporidium species and Cryptosporidium parvum subtypes in dairy calves and goat kids reared under traditional farming systems in Turkey

Molecular characterizations of Cryptosporidium spp. in ruminants reared under traditional animal management systems are scarce and studies conducted thus far have revealed largely an absence of the pathogenic and zoonotic species Cryptosporidium parvum in pre-weaned animals. In this study, we examined Cryptosporidium species and subtype distribution in free-range pre-weaned dairy calves and goat kids with diarrhea. Cryptosporidium-positive specimens from pre-weaned calves on 10 farms and goat kids on 4 farms in Ankara, Balikesir, Corum, Kirikkale, and Kirsehir Provinces, Turkey were genotyped by PCR-restriction length polymorphism analysis of the small subunit rRNA gene, which identified C. parvum in 27 calves and 9 goat kids and Cryptosporidium ryanae in 1 calf. Among the C. parvum isolates successfully subtyped by DNA sequence analysis of the 60 kDa glycoprotein gene, three subtypes were detected in calves, including IIaA13G2R1 (20/23), IIdA18G1 (2/23), and IIdA20G1b (1/23), and four subtypes were detected in goat kids, including IIaA13G2R1 (3/8), IIaA15G1R1 (2/8), IIdA22G1 (2/8), and IIdA18G1 (1/8). Data of the study suggest that dairy calves reared in a traditional cow-calf system in Turkey are mainly infected with a C. parvum subtype rarely seen elsewhere, whereas goat kids are infected with diverse subtypes. As all five C. parvum subtypes found in this study are known human pathogens, pre-weaned farm animals could play a potential role in the transmission of human cryptosporidiosis.

Development of the polymeric immunoglobulin secretory immune system (PISIS) in the respiratory tract of a porcine model

Development of the polymeric immunoglobulin secretory immune system (PISIS) in the respiratory tract of a porcine model

Occurrence of Cryptosporidium species coproantigens on a University teaching farm in Nigeria

This study was carried out to assess the potential of animals, used for teaching and research, as a source of Cryptosporidium infection for students and staff of a University in Nigeria. Faecal samples from 185 animals reared on the teaching and research farm were collected and examined for Cryptosporidium spp. antigens by the use of an enzyme-linked immunosorbent assay (ELISA). From all the samples evaluated, 35.7% (66/185) were positive for Cryptosporidium spp. antigens with an infection rate of 30.6% (15/49), 40.7% (22/54), 43.9% (18/41) and 26.8% (11/41) for cattle, sheep, goats and pigs respectively. The rate of infection was significantly higher (p<0.05) in pre-weaned animals (63.6%) than in the post-weaned (23.6%) and adult (29.1%) animals. The infection rates, 54.8% and 42.3%, for diarrhoeic and female animals were significantly higher (p<0.05) than in non-diarrhoeic and male animals respectively. The presence of coproantigens of Cryptosporidium spp. observed in stool samples of ruminants and pigs suggests that these animals may be considered as a potential reservoir of this protozoa, that is able to contaminate the environment, infect other domestic and wild animals and in some cases humans.Keywords: Cryptosporidium, ELISA, Nigeria, Pigs, Ruminants

Early postnatal repeated maternal deprivation causes a transient increase in OMpg and BDNF in rat cerebellum suggesting precocious myelination

Repetitive maternal deprivation (MD) of neonatal rats during early life is known as one of the strongest stressors to pre-weaned animals. There is increasing evidence that the cerebellum is involved in cognition and emotion. In the present study, we examined how neurotrophic factors and myelin-associated molecules and their receptors (NGF, BDNF, OMgp, TrkA, TrkB, p75 NTR, and NgR) in the cerebellum are affected by early postnatal maternal separation. Rat pups were separated from their mothers for 3h/day during postnatal days (PND) 10–15. At PND 16 and 30, the levels of mRNA and protein in the cerebellum were determined using real-time PCR and Western blot analysis. Cerebellar mRNA and protein levels of BDNF, TrkB, and OMgp were significantly increased in MD rats at PND 16. However, by PND 30 these variables normalized to control levels. In contrast, the levels of mRNA and protein for NGF, TrkA, p75 NTR, and NgR were unchanged at both ages examined. Transient enhancement of neurotrophic system and myelin-associated molecule expression may cause interference of normal development of the cerebellum such as precocious myelination, which may lead to functional and cognitive deficits later in life.

Cryptosporidiosis in small ruminants

Cryptosporidiosis is an infection caused by protozoan parasites belonging to the genus Cryptosporidium which is responsible for a potentially severe disease in new-born ruminants. This infection is highly prevalent in small ruminants throughout the world, especially in pre-weaned animals. The clinical expression is different between goat kids and lambs, the infection being generally more severe in the former. Molecular data demonstrate geographical variations in the species of Cryptosporidium infecting small ruminants. They also support the possibility of transmission of zoonotic species from these hosts to humans. Studies are still needed on molecular epidemiology, especially in goats, and on ways to control infection.

Investigation of farms linked to human patients with cryptosporidiosis in England and Wales

The study investigates farms suspected of being sources of zoonotic human cryptosporidiosis. A variety of implicated farm animal species were sampled and tested to detect Cryptosporidium oocysts and investigate genetic linkage with human patients. Risk factor information was collected from each farm and analysed by multivariable logistic regression to detect significant associations between factors and Cryptosporidium in animals. The results showed that average sample prevalence of Cryptosporidium infection was highest in cattle, sheep and pigs (∼40–50%), in the mid-range in goats and horses (20–25%) and lowest in rabbits/guinea pigs, chickens and other birds (∼4–7%). A single sample from a farm dog was also positive. Cryptosporidium parvum, which has zoonotic potential, was the commonest species and was most likely to be present in cattle and, to a lesser extent, in sheep. In particular, young calves and lambs shed C. parvum and this finding was corroborated in a statistical model which demonstrated that samples from groups of preweaned animals were 11 times, and immature animal groups six times, more likely to be positive than groups of adult animals, and that samples from a farm with a cattle enterprise were twice as likely to be positive than farms without a cattle enterprise. On seven out of eight farms, at least one C. parvum isolate from an animal sample was indistinguishable at the gp60 locus from those found in the human patients, indicating that farm animals are a likely source of infection for humans.

Effect of weight of slaughter and feeding regimen on conjugated linoleic acid and trans fatty acid content in lamb meat: a meta-analysis approach

A meta-analysis approach was used in order to synthesize findings of six trials comparing 177 individual data of CLA, vaccenic acid (VA) and total trans fatty acids (TFA) of lamb’s meat: “slaughter weight” (0-14kg, 14-18kg, 18-24kg and <24kg), “muscle” (longissimus dorsi, and other muscles); “feeding regimen”: milk (pre-weaned animals fed maternal milk); pasture (weaned grazing animals) and “confined” (weaned animals reared indoor and fed hay and concentrate). The fixed effects included in the model. Results showed that the meat from lambs slaughtered at 14-18kg and from grazing animals maximized the content of CLA and VA and minimized the content of others TFA.

Molecular identification and prevalence of Isospora sp. in pigs in Western Australia using a PCR–RFLP assay

Little is known about the prevalence of Isospora in domestic pigs in Western Australia. A total of 289 pig faecal samples were collected from pre- and post-weaned pigs and sows from 1 indoor and 3 outdoor piggeries located in the south-west region of Western Australia. Faecal samples were screened using a PCR–RFLP assay based on the ITS-1 rDNA locus. An overall prevalence of 10.4% (30/289) was identified. Isospora was detected in 16.3% (20/123) of pre-weaned animals and 6.4% (10/156) of post-weaned animals. PCR–RFLP analysis confirmed the presence of Isospora suis in 86.7% of the positive Isospora isolates. Isospora was significantly associated with diarrhea and the findings of this study suggest that management factors such as cleaning practices, flooring types and stocking densities need to be investigated in the porcine host to find new and improved measures for control.

Prevalence of Cryptosporidium genotypes in pre and post-weaned pigs in Australia

A total of 289 pig faecal samples were collected from pre-weaned and post-weaned piglets and sows from 1 indoor and 3 outdoor piggeries located in the south-west region of Western Australia and screened at the 18S rRNA locus for the presence of Cryptosporidium. An overall prevalence of 22.1% (64/289) was identified. Cryptosporidium was more prevalent in post-weaned animals ( p < 0.05); 32.7% (51/156) versus 10.6% (13/123) for pre-weaned animals. Sequence analysis identified Cryptosporidium suis in all pre-weaned isolates genotyped (7/13). In post-weaned pigs that were genotyped ( n = 38), the non-zoonotic Cryptosporidium species, pig genotype II was identified in 32 samples and C. suis in 6 samples. The zoonotic species Cryptosporidium parvum was not detected, suggesting that domestic pigs do not pose a significant public health risk. Pig genotype II was significantly ( p < 0.05) associated with ‘normal’ stools, indicating an asymptomatic nature in the porcine host.

Developmentally Regulated Intestinal Expression of IFN-γ and Its Target Genes and the Age-Specific Response to Enteric Salmonella Infection

Young infants are highly susceptible to systemic dissemination of enteric pathogens such as Salmonella typhimurium when compared with older individuals. The mechanisms underlying this differential susceptibility have not been defined clearly. To better understand this phenomenon, we examined the responses of adult mice and preweaned pups to oral infection by S. typhimurium. We found clear age-specific differences, namely, an attenuated intestinal inflammatory response and a higher systemic bacterial burden in the pups compared with the adults. To elucidate the molecular basis for these differences, we obtained a microarray-based profile of gene expression in the small intestines of uninfected adult and preweaned animals. The results indicated a striking age-dependent increase in the intestinal expression of a number of IFN-gamma-regulated genes involved in antimicrobial defense. This finding was confirmed by real-time quantitative PCR, which also demonstrated an age-dependent increase in intestinal expression of IFN-gamma. The developmental up-regulation of the IFN-gamma-regulated genes was dependent on both IFN-gamma and a normal commensal microflora, as indicated by experiments in IFN-gamma-knockout mice and germfree mice, respectively. However, the increase in expression of IFN-gamma itself was independent of the commensal flora. The functional importance of IFN-gamma in the immunological maturation of the intestine was confirmed by the observation that the response of adult IFN-gamma-knockout animals to S. typhimurium infection resembled that of the wild-type pups. Our findings thus reveal a novel role for IFN-gamma in the developmental regulation of antimicrobial responses in the intestine.

The antimicrobial properties of milkfat after partial hydrolysis by calf pregastric lipase

Studies on the kinetic characteristics of calf pregastric lipase (EC 3.1.1.3) have shown that it preferentially releases short chain fatty acids (SCFAs) from bovine milkfat. The released fatty acids form mixed micelle structures. The aim of this investigation has been to test whether hydrolysed milkfat is antimicrobial, and how the state of the emulsion alters the bactericidal or bacteriostatic effects. Partial hydrolysis of milkfat by pregastric lipase was carried out in two types of emulsion systems, containing either Triton X-100 or casein/lecithin, plus milkfat in citrate/phosphate buffer (pH 5.0–6.0). The concentrations and compositions of fatty acids were determined by gas chromatography. The minimum percentages of hydrolysed milkfat which affected growth and survival of selected Gram-positive and Gram-negative bacteria were measured. The bacterial experiments were repeated using pure fatty acids at similar concentrations. Lauric acid (C12:0) was found to be the most potent bactericidal fatty acid against Enterococcae (Gram-positive), and caprylic acid (C8:0) was the most potent against coliforms (Gram-negative). Use of Triton X-100 for milkfat emulsification provided a more compatible medium for studying bacterial growth in the hydrolysed milkfat than did use of casein/lecithin. The results also show that the antimicrobial effects of individual fatty acids released from hydrolysed milkfat were at least additive and suggest that hydrolysis of milkfat may be a significant factor in controlling growth of organisms imbibed with food in pre-weaned animals. The amount of pregastric catalyzed triglyceride hydrolysis in the digestive tract is sufficient to produce an antibacterial concentration of fatty acids and monoglycerides.

The effect of pH on the inhibition of bacterial growth by physiological concentrations of butyric acid: Implications for neonates fed on suckled milk

Butyric acid is released from milk by pre-intestinal lipases during suckling. It is also known to inhibit bacterial growth. To investigate whether butyric acid may be a significant factor in controlling bacterial growth in the stomach of pre-weaned animals, the ability of butyric acid to inhibit growth of selected bacteria was tested over physiological ranges of pH and butyric acid concentrations. Six enteric and environmental strains of bacteria were used: two strains of Escherichia coli, Klebsiella pneumoniae, Enterococcus faecium, Enterococcus faecalis, and Enterococcus casseliflavus. At pH 4.5 and 5.0, the growth of all organisms was significantly inhibited in the presence of butyrate, and in some cases growth was completely arrested. At pH 6.0, butyric acid did not affect bacterial growth until the concentration reached 40 mM. The maximum concentration of butyric acid available in cow’s milk after incubation with pre-gastric lipase is ≈16 mM, which would be sufficient to prevent growth of the organisms tested at pH values occurring in the stomach. Therefore, butyric acid inhibition of bacterial growth may explain in part, the role of pre-intestinal lipases in young animals' natural defenses against bacteria in ingested food prior to weaning.

Dietary control of the lactase mRNA distribution along the rat small intestine.

At weaning, the lactase-phlorizin hydrolase (LPH) mRNA was shown to disappear specifically from the distal part of ileum while remaining abundant in the more proximal segments of the small intestine. The purpose of this study was to analyze the longitudinal distribution of this transcript in rats whose intestinal lumen content was modified before and after weaning. Preweaned animals force-fed with an artificial diet retained a high amount of LPH mRNA in the jejunum, whereas this transcript precociously decreased in the distal ileum. Conversely, prolonged nursing delayed the specific decay of the LPH mRNA in the latter segment. Food deprivation in preweaned animals did not alter the longitudinal distribution of this transcript in that it remained abundant in the distal ileum. In adult rats, rearranging the order of the small intestinal segments with regard to the intraluminal flow of nutrients did not modify the typical distribution of the LPH mRNA. These results suggest that switching over from milk to the adult-type diet at weaning contributes to the modification of the longitudinal distribution of the LPH mRNA that normally occurs at this stage. However, once the adult pattern of expression of this transcript is established, it cannot be significantly altered by changing the position of each intestinal segment as well as its luminal content.

Intestinal lactase in the neonatal rat. Maturational changes in intracellular processing and brush-border degradation.

The mechanism of decline in the catalytic activity of intestinal lactase during neonatal maturation has not been defined, but a shift in the lactase subunit synthesis from an active 130-kDa subunit to an inactive 100-kDa species has now been noted in the adult rat (Quan, R., Santiago, N. A., Tsuboi, K. K., and Gray, G. M. (1990) J. Biol. Chem. 265, 15882-15888). The subunit structure, synthesis, intracellular assembly, and subsequent degradation of lactase from the brush-border surface membrane was examined in 15-day-old pre-weaned and 30-day-old post-weaned intact rats. Lactase was labeled intraintestinally with [35S]methionine, isolated from Triton-solubilized membranes with monospecific polyclonal anti-lactase, and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. The protein-stained gel revealed subunits of 225 and 130 kDa, the latter species predominating in both the pre- and post-weaned state. The distinct adult-type 100-kDa moiety was present in post-weaned animals while only a trace of a slightly larger (approximately 110 kDa) species was observed in pre-weaned animals. Quantitation of radioactivity in newly synthesized lactase revealed an increasing prominence of the 100-kDa species in post-weaned rats (130/100 incorporation ratio: pre-weaned 6.2; post-weaned 3.3). Accumulation of newly labeled lactase in brush-border membranes after intraperitoneal [35S]methionine labeling was similar in both groups at 3 h. Despite these comparable rates of lactase synthesis, assembly and insertion in the pre- and post-weaned state, subsequent removal of the 130-kDa unit was more rapid in post-weaned animals (t1/2 = 11 h; pre-weaned t1/2 = 37 h). In intact rats, the neonatal maturational decline in lactase catalytic activities involves both a shift to production of the inactive 100-kDa subunit and increased membrane surface degradation of the active 130-kDa subunit.