The effects of arginine and branched-chain amino acid supplementation to reduced-protein diet on intestinal health, cecal short-chain fatty acid profiles, and immune response in broiler chickens challenged with Eimeria spp.

We investigated the effects of supplementing arginine (Arg) and branched-chain amino acids (BCAA) in broilers fed reduced-protein diets and challenged with Eimeria spp. All birds were fed the same starter diet meeting Cobb 500 nutrient specifications from d 1 to 9. Four grower diets: positive control (PC) with 20.0% crude protein (CP); reduced-protein negative control (NC) with 17.5% CP; or NC supplemented with Arg or BCAA at 50% above recommendations (ARG or BCAA) were fed to the birds from d 9 to 28. Birds were allocated in a 2 × 4 factorial arrangement (4 diets, each with or without challenge), with 8 replicates per treatment. On d 14, the challenge groups were orally gavaged with mixed Eimeria spp. Intestinal permeability was higher (P < 0.05) in NC than PC, whereas the permeability of ARG and BCAA groups did not differ significantly from PC. On d 28, a significant interaction (P < 0.01) was observed in CD8+: CD4+ ratios in cecal tonsils (CT), Eimeria challenge increased the ratios in all groups except for the ARG group. On d 21, a significant interaction was found for CD4+CD25+ percentages in CT (P < 0.01) that Eimeria challenge increased the percentages only in PC and NC groups. On d 21 and 28, significant interactions (P < 0.01) were found for macrophage nitric oxide (NO) production. In nonchallenged birds, NO was higher in the ARG group than other groups, but in challenged birds, NO was higher in both ARG and BCAA groups. On d 21, a significant interaction was found for bile anticoccidial IgA concentrations (P < 0.05) that Eimeria challenge increased IgA only in NC and ARG groups. The results suggest that a reduced-protein diet exacerbates the impact of the Eimeria challenge on intestinal integrity, but this could be mitigated by Arg and BCAA supplementations. Arginine and BCAA supplementations in reduced-protein diets could be beneficial for broilers against Eimeria infection by enhancing the immune responses. The beneficial effects of Arg supplementation tended to be more pronounced compared to BCAA supplementation.

How do pigs deal with dietary phosphorus deficiency?

Feeding strategies for growing monogastric livestock (particularly pigs) must focus on maximising animal performance, while attempting to reduce environmental P load. Achieving these goals requires a comprehensive understanding of how different P feeding strategies affect animal responses and an ability to predict P retention. Although along with Ca, P is the most researched macromineral in pig nutrition, knowledge gaps still exist in relation to: (1) the effects of P feed content on feed intake (FI); (2) the impact of P intake on body composition; (3) the distribution of absorbed P to pools within the body. Here, we address these knowledge gaps by gathering empirical evidence on the effects of P-deficient feeds and by developing a predictive, mechanistic model of P utilisation and retention incorporating this evidence. Based on our statistical analyses of published literature data, we found: (1) no change in FI response in pigs given lower P feed contents; (2) the body ash-protein relationship to be dependent upon feed composition, with the isometric relationship only holding for pigs given balanced feeds and (3) the priority to be given towards P retention in soft tissue over P retention in bones. Subsequent results of the mechanistic model of P retention indicated that a potential reduction in P feeding recommendations could be possible without compromising average daily gain; however, such a reduction would impact P deposition in bones. Our study enhances our current knowledge of P utilisation and by extension excretion and could contribute towards developing more accurate P feeding guidelines.

Effects of reducing growth rate via diet dilution on bone mineralization, performance and carcass yield of coccidia-infected broilers.

Coccidiosis and rapid growth rate (GR) compromise bone mineralization in modern broilers. We tested the hypothesis that reducing GR via diet dilution during peak bone development will improve bone mineralization in both infected and uninfected broilers. A total of 384 male Ross 308 chicks were allocated to a basal grower diet (3,107 kcal/kg ME and 19.4% CP) diluted with 0, 5, 10, or 15% lignocellulose (n = 12 pens/treatment, 8 birds/pen) at day 10 of age. Prior to this, birds in each group received half the intended diet-dilution levels (day 8 to 10 of age) and a common starter diet (day 1 to 7 of age). At day 13 of age (day 0 post-infection, pi), birds were orally inoculated with either 7,000 sporulated Eimeria maxima oocysts (I) or water (C), forming a 4 diet-dilution level × 2 infection status factorial experiment. Performance was measured over 12 days pi and scaled to BW at infection (day 0 pi) to account for a priori BW differences. At day 12 pi (day 25 of age), 1 bird/pen (a total of 6 birds/treatment) was sampled to assess tibia and femur mineralization relative to BW, and carcass yield. There was no interaction (P > 0.05) between infection status and diet-dilution level on ADFI/BW measured over day 1 to 12 pi, or on any bone variable. ADG/BW pi decreased (P < 0.01) with diet dilution amongst C birds, but was statistically similar (P > 0.05) amongst I birds. I compared to C birds had reduced breast meat (P < 0.05) and eviscerated carcass yield (P < 0.01), femur (P < 0.05) and tibia (P < 0.01) breaking strength (BS), and femur ash weight (AW) (P < 0.05). Diet dilution did not affect carcass yield, but improved femur BS (P < 0.001), and tended to improve (P < 0.1) femur and tibia AW. Overall, diet dilution significantly affected femur, more than tibia, variables: relative BS, robusticity index, and ash percentage. Reducing GR affected broiler long bone mineralization to a similar degree in the presence or absence of coccidiosis.

Dietary vitamin D improves performance and bone mineralisation, but increases parasite replication and compromises gut health in Eimeria-infected broilers.

Coccidial infections reduce fat-soluble vitamin status and bone mineralisation in broiler chickens. We hypothesised that broilers infected with Eimeria maxima would benefit from increased dietary supplementation with vitamin D (vitD) or with 25-hydroxycholecalciferol (25(OH)D3 or 25D3). Broilers were assigned to diets with low (L) or commercial (M) vitD levels (25 v. 100 µg/kg) supplemented as cholecalciferol (D3) or 25D3. At day 11 of age, birds were inoculated with water or 7000 E. maxima oocysts. Pen performance was calculated over the early (days 1-6), acute (days 7-10) and recovery periods (days 11-14) post-infection (pi). At the end of each period, six birds per treatment were dissected to assess long bone mineralisation, plasma levels of 25D3, Ca and P, and intestinal histomorphometry. Parasite replication and transcription of cytokines IL-10 and interferon-γ (IFN-γ) were assessed at day 6 pi using quantitative PCR. Performance, bone mineralisation and plasma 25D3 levels were significantly reduced during infection (P < 0·05). M diets or diets with 25D3 raised plasma 25D3, improved performance and mineralisation (P < 0·05). Offering L diets compromised feed efficiency pi, reduced femur breaking strength and plasma P levels at day 10 pi in infected birds (P < 0·05). Contrastingly, offering M diets or diets with 25D3 resulted in higher parasite loads (P < 0·001) and reduced jejunal villi length at day 10 pi (P < 0·01), with no effect on IL-10 or IFN-γ transcription. Diets with M levels or 25D3 improved performance and mineralisation, irrespective of infection, while M levels further improved feed efficiency and mineralisation in the presence of coccidiosis.

Interactions between dietary calcium and phosphorus level, and vitamin D source on bone mineralization, performance, and intestinal morphology of coccidia-infected broilers1.

Coccidiosis penalizes calcium (Ca), phosphorus (P), and fat-soluble vitamin status, as well as bone mineralization in broiler chickens. We hypothesized that dietary vitamin D (VitD) supplementation in the form of 25-hydroxycholecalciferol (OHD), compared to cholecalciferol (D3), would improve bone mineralization in broilers receiving marginally deficient Ca/P diets, with more pronounced effects during malabsorptive coccidiosis. In a 2 VitD source × 2 Ca/P levels × 2 levels of infection factorial experiment (n = 6 pens per treatment, 6 birds/pen), Ross 308 broilers were assigned to an Aviagen-specified diet supplemented with 4,000 IU/kg of either OHD or D3 between days 11 and 24 of age. The diet contained adequate (A; 8.7:4.4 g/kg) or marginally deficient (M; 6.1:3.1 g/kg) total Ca and available (av)P levels. At day 12 of age, birds were inoculated with water (C) or 7,000 Eimeria maxima oocysts (I). Pen performance was measured over 12 days post-infection (pi). One bird per pen was assessed for parameters of bone mineralization and intestinal histomorphometric features (day 6 and 12 pi), as well as E. maxima replication and gross lesions of the small intestine (day 6 pi). There was no interaction between infection status and Ca/avP level on bone mineralization. Bone breaking strength (BS), ash weight (AW), and ash percentage (AP) were highest in broilers fed the OHD-supplemented A diets irrespective of infection status. Eimeria maxima infection impaired (P < 0.05) ADG and FCR pi; Ca and P status at day 6 pi; OHD status, BS, AW, and AP at day 12 pi; and intestinal morphology at day 6 and 12 pi. A- compared to M-fed broilers had higher BS, AW, and AP at day 6 pi, and AW at day 12 pi. VitD source affected only OHD status, being higher (P < 0.001) for OHD- than D3-fed broilers at day 6 and 12 pi. In conclusion, offering OHD and adequate levels of Ca and P improved bone mineralization, with no effect on performance. Dietary D3 and OHD supplemented at 4,000 IU/kg had similar effects on coccidiosis-infected and uninfected broilers, which led to the rejection of our hypothesis.

Does selection for growth rate in broilers affect their resistance and tolerance to Eimeria maxima?

Chickens exhibit varied responses to infection with Eimeria parasites. We hypothesise that broilers selected for increased growth rate will show lower resistance and tolerance to a coccidian challenge. 288 chickens of fast (F) or slow (S) growing lines were inoculated with 0 (control), 2500 (low-dose), or 7000 (high-dose) sporulated E. maxima oocysts at 13 days of age in two consecutive rounds. Gain and Intake were measured daily and their values relative to BW at the point of infection were calculated over the pre-patent (days 1-4 post-infection), acute (d5-8 pi), and recovery (d9-12 pi) phases of infection to assess the impact of infection. Levels of plasma carotenoids, vitamins E and A, long bone mineralisation, caecal microbiota diversity indices, and histological measurements were assessed at the acute (d6 pi) and recovery stage (d13 pi). In addition, we measured the levels of nitric oxide metabolites and the number of parasite genome copies in the jejunumat d6pi. In absolute terms F birds grew 1.42 times faster than S birds when not infected. Infection significantly reduced relative daily gain and intake (P < 0.001), with the effects being most pronounced during the acute phase (P < 0.001). Levels of all metabolites were significantly decreased, apart from NO which increased (P < 0.001) in response to infection on d6pi, and were accompanied by changes in histomorphometric features and the presence of E. maxima genome copies in infected birds, which persisted to d13pi. Furthermore, infection reduced tibia and femur mineralisation, which also persisted to d13pi. Reductions in measured variables were mostly independent of dose size, as was the level of parasite replication. The impact of infection was similar for S and F-line birds for all measured parameters, and there were no significant interactions between line x dose size on any of these parameters. In conclusion, our results suggest that line differences in productive performance do not influence host responses to coccidiosis when offered nutrient adequate diets.

Do not neglect calcium: a systematic review and meta-analysis (meta-regression) of its digestibility and utilisation in growing and finishing pigs.

Ca digestibility and utilisation in growing pigs are not well understood, and are usually neglected in diet formulation. This has implications not only for the accurate determination of its requirements but also for its interactions with other nutrients. A systematic review and meta-analysis (meta-regression) of published trials was carried out to quantify factors affecting Ca absorption and utilisation, and to derive an estimate of Ca endogenous excretion. The analysis was carried out on the data from forty studies, corresponding to 201 treatments performed on 1204 pigs. The results indicated that although Ca absorption and retention (g/kg of body weight per d) increased with increasing Ca intake (P<0·001), non-phytate-P intake (P<0·001) and exogenous phytase supplementation (P<0·001), these values decreased with increasing phytate-P intake (P<0·05). Interactions between exogenous phytase and Ca intake, indicating reduced efficacy of this enzyme (P<0·001), and between phytate-P intake and exogenous phytase, counteracting the direct negative effect of phytate-P (P<0·05) on Ca absorption and retention, were also detected. There were no effects of animal-related characteristics, such as pig genotype in Ca absorption and retention. The large amount of variance explained in Ca absorption (90 %) and retention (91 %) supported our choice of independent variables. Endogenous Ca losses obtained via linear regression were 239 mg/kg of DM intake (95 % CI 114, 364). These outcomes advance the current understanding of Ca digestibility and utilisation, and should contribute towards establishing requirements for digestible Ca. Consequently, pig diets will be more correctly formulated if digestible Ca values are used in estimating requirements for Ca.

Consequences of infection pressure and protein nutrition on periparturient resistance to Teladorsagia circumcincta and performance in ewes.

The consequences of protein nutrition on the degree of periparturient relaxation of immunity to nematode parasites in sheep may be more pronounced at higher levels of infection pressure. Here, we investigated interactive effects of metabolizable protein (MP) nutrition and infection pressure on resistance and lactational performance of ewes. Twin-rearing ewes were trickle infected with either 1000, 5000 or 10,000 infective Teladorsagia circumcincta larvae and fed either at 0.8 (low protein, LP) or 1.3 (high protein, HP) times their estimated MP requirement. Expected interactions between feeding treatment and infection pressure were not observed. Periparturient relaxation of immunity, as indicated by variation in faecal egg counts, was higher in LP ewes than in HP ewes and FEC showed an inverse relationship with infection pressure indicating possible density dependency effects on worm fecundity. Plasma pepsinogen concentration linearly increased with infection pressure. Daily total nematode egg excretion, assessed at week three of lactation, was not significantly affected by infection pressure but was reduced by 65% in HP ewes compared to LP ewes. MP supplementation improved lamb performance but had little effect on ewe body weight and plasma protein concentrations, whilst lactational performance, as judged from lamb performance, tended to be reduced with increased infection pressure. The results suggest periparturient MP supplementation to ewes reduces nematode egg excretion independent of infection pressure and improves lactational performance of parasitized ewes even in the presence of moderate MP scarcity.

Consequences of protein supplementation for anorexia, expression of immunity and plasma leptin concentrations in parasitized ewes of two breeds.

The periparturient relaxation of immunity (PPRI) against parasites in ewes has a nutritional basis. We investigated whether ewes experience a reduction in food intake (anorexia) during PPRI and if the magnitude of anorexia is affected by host production potential and dietary protein supplementation. We also investigated whether nematode infection is linked to plasma leptin concentrations in periparturient ewes. The experiment was a 2 x 2 x 2 factorial design. Two breeds of twin-bearing/lactating ewes (Greyface cross, G (n 32) and Scottish Blackface, B (n 32)) were used. Half of the ewes were trickle infected with 30,000 larvae of the abomasal parasite Teladorsagia circumcincta per week and the other half were not. During the experiment, all ewes had ad libitum access to a low-protein diet that provided less protein than the recommended allowance. In addition, half of the ewes received a protein supplement that resulted in protein intakes that exceeded recommendations. Nematode infection resulted in a breakdown of immunity to parasites and a reduction in food intake in both breeds. The breeds differed in the extent of PPRI (G ewes having higher faecal egg counts than B ewes), but not in the magnitude of anorexia. Protein supplementation resulted in a reduction in faecal egg counts, but had no effect on the magnitude of anorexia. Plasma leptin concentrations changed significantly over time, but were not affected by protein supplementation or infection. It is concluded that infection with T. circumcincta in periparturient ewes results in anorexia that is not alleviated by protein supplementation and seems unrelated to plasma leptin concentrations.

Plant secondary metabolites: antiparasitic effects and their role in ruminant production systems.

The purported antiparasitic properties of plant secondary metabolites (PSM) have been the cause of controversy amongst the scientific community. Despite long-standing knowledge of the prophylactic and therapeutic properties of PSM-rich extracts, which comes mainly from ethnoveterinary sources, the scientific evidence of the antiparasitic effects of PSM is inconsistent. In the first part of the present paper the causes of this controversy are addressed, and the evidence available on the antiparasitic effects of PSM is critically examined. The focus is on examples of the antiparasitic activity of PSM against helminth nematodes. The conclusion is that PSM can have antiparasitic properties, which depend on their structure, level of ingestion and availability within the gastrointestinal tract of the animal. The second part is an appraisal of the potential role of PSM for parasite control in ruminant production systems. Despite their antiparasitic properties, PSM consumption does not necessarily have positive consequences in parasitised herbivores, as excessive consumption of PSM can adversely affect herbivore fitness and survival, through their anti-nutritional properties. For this reason it is suggested that the antiparasitic properties of PSM should be assessed at the same time as their anti-nutritional effects. The same measure, e.g. the performance of parasitised hosts, should be used when assessing these properties. The assessment of the costs and benefits suggests that parasitised herbivores can benefit from the long-term consumption of PSM only if the antiparasitic benefits outweigh the anti-nutritional costs of PSM. In addition, it is proposed that parasitised animals might be able to benefit from PSM consumption even if their performance is impaired, as long as the latter is a short-term compromise that leads to long-term benefits.

The effect of consumption of foods that differ in energy density and/or sodium bicarbonate supplementation on subsequent diet selection in sheep.

The short-term consumption of foods that differed in energy density (ED) and/or NaHCO3 supplementation, on subsequent food intake and diet selection in sheep were measured. Thirty sheep weighing 35.9 (sd 2.89) kg were used. Two foods were formulated: H had 11 and L had 8 MJ metabolizable energy/kg fresh matter. Four further foods were formulated by adding either 40 g NaHCO3/kg or 16.5 g NaCl/kg to foods H and L. NaCl was added to give the same Na concentration as with 40 g NaHCO3/kg to control for any effects of Na per se. In a preliminary test, it was found that a 2 h consumption of food H supplemented with NaHCO3 could buffer potential impact on the rumen environment of subsequent consumption of food H alone (as judged by rumen pH and acid-buffering capacity); however, it was not as effective as the consumption of food L alone in doing so. Each food treatment was offered to one of six groups (n 5) for 2 h following 16 h of food deprivation. Sheep were then offered a choice between H and L for a further 6 h. Supplementing H or L with either NaHCO3 or NaCl had no significant effect on either intake or diet selection. ED significantly (P<0.01) affected intake during the 2 h single feeding period, with sheep offered H or L consuming 540 and 663 (sed 37) g respectively, but had no effect on subsequent intake during the choice period. During the choice period all sheep showed a preference for food H, but sheep previously offered L selected significantly more H (0.873 g/g) than sheep previously offered H (0.544 (sed 0.028) g/g; P<0.001). It is concluded that short-term consumption of foods that differ in ED, and hence in their potential impact on the rumen environment, significantly affects subsequent diet selection. This is in agreement with the hypothesis that ruminant animals select a diet to help maintain the rumen environment within a certain physiological range. Food H with 40 g NaHCO3 added/kg may not have been sufficient to affect subsequent diet selection. It is suggested that larger, rather than smaller, changes in the rumen environment achieved through previous feeding should be expected to alter subsequent diet selection.