Absorption and secretion of calcium and phosphorus in the alimentary tract of lambs infected with daily doses of Trichostrongylus colubriformis or Ostertagia circumcincta larvae

The effect of Haemonchus contortus and Trichostrongylus colubriforms infection on the ruminal microbiome of lambs

We evaluated Haemonchus contortus (HC) and Trichostrongylus colubriformis (TC) infection on the ruminal microbial community of Santa Ines lambs to better understand the pathophysiology of parasite infections and the interactions among gastrointestinal nematodes and gut resident microbiota. In this study, 18 six months of age lambs were maintained for 34 days in individual pens divided into three treatments that included animals infected with HC and TC, and control (infection-free). Haematological, ruminal parameter and microbial nitrogen absorbed by pune derivatives, as well as enteric methane emission (CH₄), were analysed, and the rumen microbial taxonomic and functional profile assessed by shotgun metagenomics. The analysis showed that total protein, albumin, urea, and butyrate level were lower in animals infected by both parasites, while HC infection also decreased the haemoglobin level. Both infected groups (TC and HC) increased the enteric methane emission (CH₄). TC and HC infections increased the diversity and richness of functional microbial genes. Most alterations in the rumen microbiome composition of infected groups are associated with the suppression of microbes involved in microbial homeostasis maintenance and expansion of the archaeal community in the infected animals. Infection led to an increased abundance of nitrogen, amino acid, protein, and energy metabolism genes. Overall, TC and HC infection increased the enteric methane emission, negatively affected taxon's responsible for maintenance de rumen homeostasis and modulated some important genes related to protein and energy metabolism.

Trichostrongylus colubriformis affecting sheep phosphorus metabolism and precision feeding as a mitigating strategy

This review details the negative effects of Trichostrongylus colubriformis infection in sheep phosphorus metabolism and direct and indirect impacts from high excretion from susceptible animals, as well as the advantages offered by precision feeding as potential strategies to mitigate loss. In sheep infected with T. colubriformis there is a high reduction in P bioavailability, because of depression in the absorptive capacity of this mineral, affecting the absorption and recycling of P to the digestive tract, causing mineral deficiency. Therefore, precision feeding compiles animal genetics information, feeding type and grazing management to control animal feed intake and quantity and quality of manure produced. In this sense, the adoption of precision feeding can provide a better arrangement of the information, making sheep production more economically, socially and environmentally sustainable.

Effect of gastrointestinal nematodes on serum copper and phosphorus of growing beef calves in northwestern Argentina

The aim of this work was to study the effect of gastrointestinal nematodes (GINs) on copper (Cu) and phosphorus (P) in blood of beef cattle in two ranches (R1 and R2) located in northwestern Argentina. In 2015-2016 (R1) and 2016-2017 (R2), in each ranch, 22 weaned female calves were divided into two groups: calves treated systematically with 200 mcg/kg moxidectin every 45-50 days (TG) and untreated calves (UTG). The following parameters were measured: number of fecal eggs (epg), fecal cultures, serum Cu and P levels, and live weight gain (LWG). Differences between groups were compared using analysis of variance and Tukey test. GIN infections in both ranches were subclinical and moderate, showing the highest epg (R1 = 907 ± 754; R2 = 1049 ± 1040) by mid-winter. Epg values of TG groups were always negligible (> 93% of moxidectin efficacy). The dominant nematode genera were Cooperia and Haemonchus. The average serum Cu values (μg/dl) indicated low (R1 = 49.7 ± 18) and severe (R2 = 27.2 ± 14) deficiency. The effect of treatments was evident in both ranches from late winter, with TG showing significantly (p < 0.01) higher serum levels in winter, spring, and early autumn (R1 = 65.1, 50.9, and 60.3; R2 = 48.0, 25.7, and 22.4) than UTG (R1 = 44.3, 33.9, and 32.9; R2 = 25.5, 18.2, and 16.4). There were no differences in serum P levels between groups. LWG of TG increased significantly (p < 0.008) (27.2% in R1 and 38.6% in R2), with respect to those of UTG. This study showed a negative effect of GIN on serum Cu values in moderately infected growing calves.

Parasitism and production in farm animals

The impact of internal and external parasitism on productivity of farm animals is considered for cattle, sheep, pigs and poultry. The parasitic challenge experienced and the outcome of that challenge is a dynamic one in which environment, management practices, including housing or grazing management, nutritional status, the host's ability to develop effective immunity and the speed with which this can occur, play a significant role. Much of our assessment of the impact of infection comes from pathophysiological and nutritional studies with contrived infestations. A common feature of all infestations is reduced efficiency of food utilization through reduction in food intake, though in some cases increases in nutrient requirement are induced as a result of damage to or loss of host tissue. Assessment of the impact on productivity in the field is technically very difficult and must take account of fluctuating challenge, determined by environmental and management decisions, and the manager's objectives for the performance of a particular category of livestock. This review attempts to integrate the assessment of losses in productivity based on pathophysiological studies with those based on protection of groups of livestock in production systems by regular pesticide use. Throughout the review the limitations inherent in both approaches and in our knowledge of how parasites impair productivity of the host are emphasised.

Feeding practices and effects of gastrointestinal parasite infections on live weight gain of small ruminants in smallholder mixed farms in Kenya

The objective of this study was to quantify the effects of gastrointestinal nematodosis on live weight gain (LWG) of sheep and goats kept in smallholder farms in Kenya. A total of 307 sheep and goats from smallholder farms were sampled using a 2-stage cluster and systematic random approach. Sampled farms were visited once a month for nine months during which a health and production survey questionnaire was administered, animals weighed and fecal samples taken for fecal egg count. Descriptive statistics and a generalized linear mixed model were performed in SAS. The mean LWG of suckling kids and lambs was low (mean=46 g/day). High fecal egg count and lack of feed supplementation were identified as the main factors limiting growth. Improved helminth control and nutrition are required to optimize production.

Osteopenia and reduced serum alkaline phosphatase activity in grazing lambs naturally infected with gastrointestinal nematodes

The effect of gastrointestinal nematode infections on bone development was investigated in growing sheep on pasture. Forty-five weaned lambs from six groups in a two-factorial design incorporating stocking rate (SR; low, medium and high) and presence or absence of infection on pasture were sampled in the late grazing season. Worm counts were performed at slaughter, and the left metacarpal bones were excised for bone assessment. Faecal egg counts and worm burdens, primarily of Ostertagia circumcincta and Trichostrongylus vitrinus, were considerably higher in the high SR infected group ("I-High") than in comparable animals at low or medium SRs, whereas uninfected groups showed negligible egg excretion. Clinical biochemistry revealed significantly reduced serum concentrations of albumin, calcium and alkaline phosphatase in infected lambs. Nematode infections were associated with significant reductions in bone mineral density (30% at high SR), measured by dual energy X-ray absorptiometry, and in bone size (9%). Histomorphometry indicated thinning of the trabecular structure and reduced bone formation in the infected groups, particularly the I-High group. Bone mineral density, bone tissue volume and structural changes were strongly associated with log-transformed worm counts. The study showed that lambs suffering from moderate to heavy degrees of naturally acquired gastrointestinal nematode infection developed marked osteopenia after weaning, i.eduring the later part of the grazing season.

Implications of nutrition for the ability of ruminants to withstand gastrointestinal nematode infections

Resistance and resilience of the ruminant host to gastrointestinal (GI) parasitic nematode infections are influenced by many factors, including nutrition. This review examines the effects of host nutrition on the ability of ruminants to withstand GI nematode infections. Firstly the effects of infection on host metabolism are summarised briefly. An important factor in the pathogenesis is a reduction in feed intake by the host. Gut nematodes also increase endogenous protein losses, which result in net loss of amino acids to the parasitised host, though energy and mineral metabolism are also perturbed. The indications are that the major nutritional change is in protein metabolism. Resilience (the ability of an animal to withstand the effects of infection) can be enhanced markedly by increasing metabolisable protein supply and to a lesser extent metabolisable energy supply. Resistance to GI nematodes (ability of host to prevent establishment and/or development of infection) is also influenced by diet, particularly metabolisable protein supply. While there do not appear to be any effects of host nutrition on establishment of infective larvae, the rate of rejection of adult worms can be enhanced by improved nutrition. The exact nutritional requirements or the mechanisms involved are not known. It appears that the effects of improving nutritional status on host resilience are more clearly defined than effects on host resistance. The implication of changes in host resistance with nutritional state for host productivity need to be better described. Understanding the role of nutrition in improving both resistance and resilience of the host to GI parasites will be important if producers are to make better use of host acquired immunity and reduce dependence on pesticides for prophylaxis.

The pathophysiology and development of immunity during long-term subclinical infection with Trichostrongylus colubriformis of sheep receiving different nutritional treatments

The objective of this study was to investigate the relationship between protein nutrition, the pathophysiology, and acquisition and expression of immunity in long-term subclinical intestinal parasitism in sheep. Growing sheep were either uninfected controls or parasitised for 27 weeks with a daily dose of 2500 larvae of Trichostrongylus colubriformis, whilst they were given access to: (1) a low protein food, (2) a high protein food, or (3) a choice between the two foods, where they were allowed to select their diet. Blood samples were taken weekly for determination of serum albumin, total protein, Ca, P, urea and fructosamine concentrations. At the end of the study all sheep received a single (secondary) challenge infection (30,000 T. colubriformis L3) after treatment with anthelmintic to assess their immune status. The concentrations of sheep-mast cell proteinases (SMCP) in intestinal tissue, the number of circulating eosinophils and the total worm numbers recovered from the intestinal tract were used to investigate the effects of previous nutrition on the acquisition and expression of immunity. From the biochemical variables measured over 27 weeks, only serum fructosamine was affected by the interaction between feeding treatment and parasitism: fructosamine concentrations declined only in the parasitised animals on the low protein food during Weeks 6-15 of infection. This casts doubt on the usefulness of plasma fructosamine levels as an indicator of gastrointestinal parasitism, due to its being influenced by the nutritional environment. Total protein, albumin, calcium and phosphorus concentrations in the serum were affected by parasitism, but independently of feeding treatment. During the period of secondary challenge eosinophil numbers and SMCP concentrations were higher in the parasitised animals, reflecting the animals immune responsiveness. The numbers of worms recovered from the intestine of previously parasitised sheep were low; all three indicators of the development of acquired immunity were unaffected by previous nutritional treatment of the sheep. The results do not support the view that the pathophysiology of long term subclinical intestinal parasitism and the expression of acquired immunity induced by a trickle infection could be affected by the feeding treatment of the sheep (protein nutrition).

Nutrition and parasite interaction

This overview focuses on the interaction between nutritional status and gastrointestinal nematode infection in ruminants and considers: (i) the influence of the parasite on host metabolism; and (ii) the effect of host nutrition on the establishment and survival of parasite populations, the development of the host-immune response and the pathophysiology of infection. Gastrointestinal nematodes reduce voluntary feed intake and efficiency of feed utilisation, a key feature being an increased endogenous loss of protein into the gastrointestinal tract. Overall there is movement of protein from productive processes into repair of the gastrointestinal tract, synthesis of plasma proteins and mucoprotein production. Although reduction in feed intake is a major factor contributing to the reduced performance of parasitised ruminants, the underlying mechanisms of the anorexia are poorly understood. Supplementation of the diet with additional protein does not appear to affect initial establishment of nematode infections but the pathophysiological consequences are generally more severe on lower planes of protein nutrition. The main effect of protein supplementation is to increase the rate of acquisition of immunity and increase resistance to reinfection and this has been associated with an enhanced cellular immune response in the gastrointestinal mucosa. The unresponsiveness of the young lamb can be improved by dietary protein supplementation. Recent trials have shown that growing sheep offered a free choice between a low and a high protein ration are able to modify their diet selection in order to alleviate the increase in protein requirements which result from gastrointestinal nematode infection. Studies on the influence of nutrition on the expression of genotype have shown that the benefits of a superior genotype are not lost on a low protein diet whereas a high protein diet can partially emeliorate the disadvantages of an inferior genotype. In addition to dietary protein both macro-minerals and trace elements can influence the host-parasite relationship.

Influence of supplementation with dietary soyabean meal on resistance to haemonchosis in Hampshire down lambs

The influence of dietary protein supplementation on resistance to haemonchosis was examined in Hampshire down lambs fed either a basal diet or a diet supplemented with soyabean. At seven months of age the lambs were challenged with an initial loading dose of Haemonchus contortus, followed by a trickle infection three times a week. Blood and faecal samples were collected three times a week and bodyweights were recorded weekly. After 10 weeks the lambs were slaughtered and their worm burdens and carcase composition determined. Although their mean worm burdens were similar, the lambs given the basal diet had higher faecal egg counts, lower packed red cell volumes and lower concentrations of total plasma protein and plasma albumin than the lambs given the supplemented diet. The dietary supplementation also improved the carcase composition of the lambs.

The absorption of phosphate from the digestive tract of ruminant animals

Under normal dietary conditions in which the phosphorus (P) intake of ruminant animals is adequate, the absorption of phosphate (Pi) ions takes place from both the fore-stomachs and the small intestine. The rate of Pi absorption from the latter appears to be at least three times greater than that from the former. When absorption of Pi ions from the reticulorumen is severely reduced, as in dietary P deficiency, the absorption of both calcium and magnesium ions from the reticulorumen becomes impaired. Thus, dietary P deficiency may play a role in the aetiology of acute grass tetany.

Interactions of Ostertagia species with their bovine and ovine hosts

Ostertagia spp. affect their hosts in several complex interactions involving structural, biochemical, hormonal, nutritional and immunological mechanisms. Following infection with Ostertagia spp. the specialised secretory function and junctional integrity of gastric epithelial cells is lost. The pH of the abomasal contents is elevated and pepsinogen concentration in the plasma increases. There is a concurrent elevation in the concentration of blood gastrin. The effects may be a response to the physical interaction of parasite with epithelial cells, may be mediated through parasite excretory/secretory products, or by neural mechanisms. There may also be interactions between the responses since elevated abomasal pH stimulates secretion of gastrin. Hormonal changes may also have a role in the increased susceptibility of host to parasite during the periparturient period. Prolactin was considered the most likely hormone candidate although there is now a body of evidence to suggest that elevated prolactin concentrations are not solely responsible. Infection with Ostertagia spp. causes a marked inappetance, negative nitrogen balance and reduction in apparent gross energy digestion. The level of nutrition may also affect the response of the host to the parasites and establishment of O. circumcincta is lower in animals on a low plane of nutrition than those on a high plane. Immunity of Ostertagia spp. develops slowly and once established is manifest following challenge by an initial hypersensitivity response, followed by a cell mediated response and then an antibody response. Parasites may fail to establish or may be expelled from immune animals and if they do establish may be stunted with small vulval flaps and lower biotic potential and may become inhibited at the early fourth stage of development.

Pathophysiology of infection with Ostertagia ostertagi in cattle

Infection with the abomasal nematode, Ostertagia ostertagi, is an important cause of impaired productivity in young cattle in temperate parts of the world. Such losses have been associated with marked changes in feed intake, gastrointestinal function, protein, energy and mineral metabolism, and in body composition. The reduction in feed intake is an important factor in the pathogenesis of infection and may account for a large part of the difference in weight gain between ad libitum fed control and infected calves. Despite the obvious importance of inappetance, only recently has an association been made between reduced intake, altered gut motility and elevated levels of certain gastrointestinal hormones, such as gastrin. It has been suggested that the elevated gastrin levels accompanying abomasal parasitism may impair reticulo-ruminal motility and slow down abomasal emptying, leading to a stasis of ingesta and a reduction in feed intake. The rise in blood gastrin levels may also be partly responsible for the marked hyperplasia of the fundic mucosa seen in abomasal infections. Pronounced changes in protein metabolism have also been associated with Ostertagia infection. Radioisotopic studies have demonstrated increased losses of albumin into the gastrointestinal tract which are accompanied by an increase in the rate of synthesis in the liver. Dietary protein breakdown in the abomasum is also likely to be impaired, although there is evidence of a compensatory increase in protein digestion in the lower gut of parasitised calves. Increased losses of albumin are not always accompanied by increases in faecal nitrogen, suggesting that albumin is broken down and recycled as ammonia. Radioisotopic studies in animals with intestinal nematode infections have demonstrated a marked reduction in muscle protein synthesis and an increase in protein synthesis in gastrointestinal tissue. Such changes in the balance of protein synthesis are likely to be brought about by alterations in the balance of certain metabolic hormones. Marked changes in energy metabolism also accompany Ostertagia infection. Parasitised calves exhibit a marked increase in non-esterified fatty acid levels, resulting from the mobilisation of adipose tissue, and a reduction in digestive efficiency of energy, probably associated with the increase in cycling of protein through the gastrointestinal tract and the compensatory increases in protein synthesis. Mineral metabolism may also be affected although relatively little work has been conducted in cattle. Changes in body composition reflect a reduction in deposition of muscle protein and fat, and an increase in bone content and water retention.

The effects of a concurrent infection of Trichostrongylus colubriformis and Ostertagia circumcincta on calcium, phosphorus and magnesium transactions along the digestive tract of lambs

Twelve lambs, paired on the basis of live weight, were cannulated in the abomasum, proximal jejunum and terminal ileum. Six were infected with 3000 T. colubriformis and 3000 O. circumcincta larvae per day for 18 weeks. The other six lambs were pair-fed to the infected lambs. All animals were offered fresh ryegrass and white clover pasture, cut daily. Dry matter intake, live weight and plasma Ca, P and Mg concentrations were measured throughout the experiment. During weeks 7 and 17 post-infection, digesta flow along the gastrointestinal tract of infected and control animals was measured. Parasitism depressed dry matter intake by 60 per cent and was associated with a reduction in retention of Ca, P and Mg in both infected and control animals. During weeks 7 and 17, parasitism increased the flow of Ca past the proximal jejunum and, during week 17, the flow of P past the terminal ileum. Increased endogenous Ca and P losses, together with a net reduction in absorption of Ca and P, were associated with depressed plasma Ca and P concentrations. These findings, together with evidence of reduced addition of P to anterior regions of the tract, indicate induced Ca and P deficiency. There was evidence for compensatory absorption of Ca and P in the large intestine and distal small intestine, respectively. Magnesium metabolism was apparently not affected by parasitism.

Effects of concurrent copper deficiency and gastro-intestinal nematodiasis on circulating copper and protein levels, liver copper and bodyweight in sheep

Sheep were rendered hypocupraemic using parenteral ammonium tetrathiomolybdate (ATM). Fifteen thousand third stage larvae of Trichostrongylus axei and T. colubriformis in the ratio 1:1 were administered three times per week for six weeks, starting four weeks after cessation of ATM treatment. The changes in liver and plasma copper (Cu), caeruloplasmin activity, serum proteins, faecal nematode egg counts and total nematode counts were measured in the sheep for 10 weeks after infection. Decreases in liver Cu, plasma Cu and caeruloplasmin activities were detected soon after infection. There was a significant (P less than 0.05) interaction of the effects of Cu deficiency and nematode infection on these changes. Hypoproteinaemia, attributed to serum albumin loss, was demonstrated seven weeks after infection, but this was not associated with the interaction of Cu deficiency and nematode infection. No changes in serum globulins were detected. Although the results support the contention that gastro-intestinal nematodiasis can significantly exacerbate an existing Cu deficiency in sheep, there was no evidence that hypocuprosis would predispose sheep to higher nematode burdens.

Calcium and phosphorus absorption in lambs exposed to Trichostrongylus colubriformis

Ten lambs (29 +/- 1.2 kg) reared parasite-free and prepared with rumen, duodenal and ileal cannulae were paired and one of each pair was given a daily oral dose of 2500 Trichostrongylus colubriformis larvae for 14 weeks. Untreated animals received the amount of ration consumed by their infected pair-mates the previous day. During weeks 6 and 12 of infection, all lambs underwent a 7 day calcium (Ca) and phosphorus (P) balance. During weeks 7 and 13, duodenal and ileal samples were collected to determine the amounts of Ca and P entering and leaving the small intestine. The infection caused varying degrees of feed refusal in all infected animals. As a result, the data on Ca and P in excreta and the amounts of Ca and P entering and leaving the small intestine were regressed against dry matter (DM) intake for each group at each period. There were no between-period differences in these relationships. Calcium absorption and retention were unaffected by the stress of infection. Infection affected several aspects of P metabolism. Blood P concentrations were markedly reduced. Absorption of P from the small intestine was greater (P less than 0.01) in control lambs (at 1 kg DM intake 6.6 g per day) than in infected animals (2.2 g P per day), but there was a greater (P less than 0.05) duodenal flow rate of P in control lambs which suggested much higher rates of salivary secretion of P than in infected animals. Phosphorus flow rates at the ileum were greater (P less than 0.01) in infected lambs, despite the lower duodenal flow rates, which indicated a major abnormality (P less than 0.01) in small intestine absorption of P in infected animals; this may have contributed to the growth check experienced by these lambs.