In this experiment, we assessed the effect of amino acid (AA) intake restriction in entire male Yorkshire pigs between 15 and 38 kg BW (restriction phase) on BW gain, body composition and plasma levels of blood urea nitrogen (BUN), cortisol, insulin-like growth factor I (IGF-I), growth hormone (GH) and leptin during the subsequent re-alimentation phase. During the restriction phase, 36 pigs were allotted to one of two dietary treatments: adequate AA intake (control) or AA-limiting diets (AA-30%). Thereafter, pigs were fed common non-limiting diets up to 110 kg BW. Throughout the experiment, pigs were scale-fed at 90% of the estimated voluntary daily digestible energy intake. At the end of the restriction phase, pigs on AA-30% had lesser BW gain (650 v. 784 g/day; P < 0.001), loin area (LA; 12.2 v. 14.2 cm2; P < 0.001), BUN (4.6 v. 6.3 mg/dl; P < 0.02), lesser plasma levels of IGF-I (440 v. 640 ng/m; P < 0.001) and cortisol (8.2 v. 19.2 μg/dl; P < 0.001), greater backfat thickness (BF; 7.56 v. 6.56 mm; P < 0.02), and greater plasma levels of leptin (2.7 v. 1.8 ng/ml; P = 0.027) and GH (3.3 v. 2.0 ng/ml; P = 0.05) than pigs on control. During the re-alimentation phase, previously restricted pigs showed full compensatory growth (CG) in terms of BW gain (1170 v. 1077 g/day; P < 0.002), whole-body protein deposition (Pd) (179 v. 163 g/day; P < 0.001) as well as physical and chemical body composition (whole-body lipid to body protein mass ratio, LB/PB; 1.14 v. 1.15; P > 0.10). Besides GH at 45 kg BW (4.2 v. 2.4 ng/ml; P = 0.066), there were no effects of previous AA intake restriction on leptin, IGF-I and BUN during the re-alimentation phase (P > 0.10). Plasma cortisol and IGF-I levels may act as an indicator of AA-induced restriction in Pd in growing pigs. Plasma BUN level does not appear as a sensitive indicator for compensatory Pd. Plasma leptin and GH levels allow for the involvement of the brain in controlling chemical body composition. Full CG was observed during the energy-dependent phase of Pd in growing pigs and might be driven by a target LB/PB, possibly mediated via plasma leptin, IGF-I and GH levels.

Considerable progress has been made in the nutritional modelling of growth. Most models typically predict (or analyse) the response of a single animal. However, the response to nutrients of a single, representative animal is likely to be different from the response of the herd. To address the variation in response between animals, a stochastic approach towards nutritional modelling is required. In the present study, an analysis method is presented to describe growth and feed intake curves of individual pigs within a population of 192 pigs. This method was developed to allow end-users of InraPorc (a nutritional model predicting and analysing growth in pigs) to easily characterise their animals based on observed data and then use the model to test different scenarios. First, growth and intake data were curve-fitted to characterise individual pigs in terms of BW (Gompertz function of age) and feed intake (power function of BW) by a set of five parameters, having a biological or technico-economical meaning. This information was then used to create a population of virtual pigs in InraPorc, having the same feed intake and growth characteristics as those observed in the population. After determination of the mean lysine (Lys) requirement curve of the population, simulations were carried out for each virtual pig using different feeding strategies (i.e. 1, 2, 3 or 10 diets) and Lys supply (ranging from 70% to 130% of the mean requirement of the population). Because of the phenotypic variation between pigs and the common feeding strategies that were applied to the population, the Lys requirement of each individual pig was not always met. The percentage of pigs for which the Lys requirement was met increased concomitantly with increasing Lys supply, but decreased with increasing number of diets used. Simulated daily gain increased and feed conversion ratio decreased with increasing Lys supply (P < 0.001) according to a curvilinear–plateau relationship. Simulated performance was close to maximum when the Lys supply was 110% of the mean population requirement and did not depend on the number of diets used. At this level of Lys supply, the coefficient of variation of simulated daily gain was minimal and close to 10%, which appears to be a phenotypic characteristic of this population. At lower Lys supplies, simulated performance decreased and variability of daily gain increased with an increasing number of diets (P < 0.001). Knowledge of nutrient requirements becomes more critical when a greater number of diets are used. This study shows the limitations of using a deterministic model to estimate the nutrient requirements of a population of pigs. A stochastic approach can be used provided that relationships between the most relevant model parameters are known.

A field enquiry mentioned the potential positive impact of a feed restriction on the health of young rabbits, but no objective information relates the intake to digestive health. The effects of a post-weaning feed restriction strategy were thus studied on digestive health and growth and carcass parameters of the growing rabbit, using a monofactorial design that produces a quantitative linear reduction of the intake, from ad libitum (AL group) to 80%, 70% and 60% of AL. The study was performed simultaneously in six experimental sites, on 1984 growing rabbits (496 per treatment) collectively caged from weaning (34 to 38 days of age, depending on the site) to slaughter (68 to 72 days). The feeding programme was applied as followed: restriction during 21 days after weaning, and then ad libitum till slaughter. During the feed restriction period the growth rate was linearly reduced with the restriction level, by 0.5 g/day for each percent of intake reduction. When returning to ad libitum intake (after 54 days old) a compensatory growth and a higher feed efficiency occurred. Therefore, the impact of the feeding programme on the slaughter weight (SW) was significant (−4.5 g/% of restriction), but relatively moderate: the weight loss of the more-restricted rabbits (60%) reached 7.7% (−200 g) compared to the AL group. Over the whole fattening period, the feed restriction reduced linearly and significantly the feed conversion (FC) (−0.0077 unit/% of restriction). Carcass traits were little affected by the feeding programme, except for a slightly lower decrease of the dressing percentage (mean: 1.2 units between AL and the three restricted groups). On the six experimental sites, mortality and morbidity were always caused by acute digestive disorders, namely diarrhoea and/or caecal impaction. Independent of the treatment, the mortality rate strongly varied according to the site (between 7% and 18% from weaning to 54 days and for the AL group). During feed restriction, the mortality was significantly lower from a restriction threshold of 80% (meanly: −9% compared to AL). The morbidity was also significantly reduced (−6%) for the two most restricted groups (70% and 60%). The favourable effect of a lower intake on health did not persist after returning to ad libitum intake (54 days to slaughter), since mortality and morbidity were not significantly different among the treatments. Such a feeding strategy thus represents a double benefit in terms of feed costs and lower losses of young rabbits.

Probiotics such as lactic acid bacteria directly influence the host’s health and have beneficial effects such as decreasing the number of enteric pathogens, regulating intestinal immune responses and preventing diseases. Among domestic animals, probiotics have been expected to be an alternative to antibiotics added in the diet; and fermented liquid diet (FLD) containing probiotics has great potential as a diet for reducing the use of antibiotics. In this study, we evaluated the immunomodulatory effects of FLD, prepared using Lactobacillus plantarum LQ80 (LQ80), on the immune response of weaning pigs. Ten weaning piglets were divided into two groups and were fed the FLD (n = 5) or a non-fermented liquid diet (NFLD) (n = 5) for 28 days. At the end of the experiment, the total immunoglobulin M (IgM) and immunoglobulin G (IgG) levels in the sera of the FLD-fed piglets were significantly higher than those of the NFLD-fed piglets (P < 0.05). In contrast, the total immunoglobulin A (IgA) levels in the feces and saliva were not significantly affected by FLD feeding. However, the mean fecal IgA levels of FLD-fed piglets at day 28 were higher than those at 14 and 21 days (P < 0.05). Blood cells from the FLD-fed piglets showed a low level of interferon-γ secretion and mitogen-induced proliferation compared to that of the NFLD-fed piglets. Furthermore, the levels of interluekin-8 and tumor necrosis factor-α, which are proinflammatory cytokines, in the blood cells of the FLD-fed piglets were lower than those of the NFLD-fed piglets (P < 0.05). In conclusion, the FLD used in this study could alter the immune responses of weaning piglets by stimulation of the systemic or mucosal antibody response, without unnecessary inflammatory reactions. This indicates, that the FLD feed prepared with the use of LQ80 may be a candidate feed, with regard to enhancing immune responses and preventing diseases in weaning piglets.

The Ram Genotyping Scheme was launched in Great Britain in 2001 as part of the National Scrapie Plan and was devised to reduce and eventually eradicate classical scrapie susceptible genotypes from the national pedigree flock. Anecdotal claims from breeders suggest that sheep with more resistant PrP genotypes may have inferior phenotypes. In this study, we test this possibility for lamb production traits in three breeds of lowland sheep: Charollais (22 752 lambs), Poll Dorset (22 589 lambs) and Texel (23 492 lambs). Data were received from 50 breeders and comprised weights at birth, 8 weeks and scanning (from which average daily weight gain was derived), and ultrasonic muscle and fat depths. Animal (direct) genetic effects and up to three maternal effects were fitted in linear mixed models for each trait. Fitting either PrP genotype or number of copies of individual alleles carried as fixed effects allowed potential associations with the PrP gene to be assessed. There were no significant associations seen in the Poll Dorset breed; however, significant associations were found with the number of allele copies carried in the other two breeds included in this study. Charollais lambs carrying one copy of the VRQ allele had significantly (P < 0.01) greater ultrasonic muscle depth (0.58 mm) and fat depth (0.2 mm) than non-carriers. In the Texel breed, lambs with one ARR allele were significantly heavier than those with two or zero ARR alleles; heterozygous ARR lambs were 0.07 kg heavier at birth (P < 0.05), 0.42 kg heavier at 8 weeks (P < 0.01) and 0.17 kg heavier at scan weight (P < 0.01), than non-carriers. After Bonferroni corrections to adjust significance thresholds to account for the large number of independent comparisons made, all significant results remained so at P < 0.05 or greater, except for the ARR allele effect on birth weight in the Texel breed, which was no longer significant. These results compare favourably with others from studies on many continental breeds of sheep, published in recent years, and add credence to the conclusion that selection on PrP genotype is unlikely to have any noticeable impact on the measured growth and carcass traits in sheep.

We measured the incorporation of recycled urea-nitrogen (N) by ruminal microbes, using five ruminally and duodenally fistulated steers (237 kg) fed low-quality grass hay (47 g crude protein/kg dry matter (DM)). Three received 1 kg/day of soybean meal (SBM) and two received no supplemental protein (control). The experiment was 15 days long. Background enrichments of 15N were measured on day 9 and continuous jugular infusion of 0.12 g/day [15N15N]urea began on day 10. Daily samples of urine, feces, ruminal bacteria and duodenal digesta from days 10 through 14 were used to determine plateaus in 15N enrichment. Duodenal and bacterial samples collected on day 15 were used to measure duodenal N flows. Bacterial N flow was calculated as duodenal N flow multiplied by duodenal 15N enrichment divided by bacterial 15N enrichment. Bacterial N from recycled urea-N was calculated as bacterial N flow multiplied by bacterial 15N enrichment divided by urinary urea 15N enrichment. Urinary enrichment of [15N15N]urea plateaued within 24 h, whereas 14N15N urea plateaued within 48 h of [15N15N]urea infusion. Bacteria reached a plateau in 15N enrichment within 24 h and duodenal samples within 48 h. Urea production was 17.6 g of urea-N/day for control and 78.0 g/day for SBM. Gut entry was 0.99 g of urea-N/g of urea-N produced for control and 0.87 g/g for SBM. Incorporation of recycled N into microbial N was 9.0 g of N/day for control and 23.0 g/day for SBM. Recycled urea-N accounted for 0.33 g of N/g of microbial N at the duodenum for control and 0.27 g/g for SBM. Our methods allowed measurement of incorporation of recycled urea-N into ruminal microbial N.

From the simultaneous accumulation of hydrogenation intermediates and the disappearance of Isotricha prostoma after algae supplementation, we suggested a role of this ciliate and/or its associated bacteria in rumen biohydrogenation of unsaturated fatty acids. The experiments described here evaluated the role of I. prostoma and/or its associated endogenous and exogenous bacteria in rumen biohydrogenation of C18:2n-6 and its main intermediates CLA c9t11 and C18:1t11. Fractions of I. prostoma and associated bacteria, obtained by sedimentation of rumen fluid sampled from a monofaunated sheep, were used untreated, treated with antibiotics or sonicated to discriminate between the activity of I. prostoma and its associated bacteria, the protozoan or the bacteria, respectively. Incubations were performed in triplicate during 6 h with unesterified C18:2n-6, CLA c9t11 or C18:1t11 (400 μg/ml) and 0.1 g glucose/cellobiose (1/1, w/w). I. prostoma did not hydrogenate C18:2n-6 or its intermediates whereas bacteria associated with I. prostoma converted a limited amount of C18:2n-6 and CLA c9t11 to trans monoenes. C18:1t11 was not hydrogenated by either I. prostoma or its associated bacteria but was isomerized to C18:1c9. A phylogenetic analysis of clones originating from Butyrivibrio-specific PCR product was performed. This indicated that 71% of the clones from the endogenous and exogenous community clustered in close relationship with Lachnospira pectinoschiza. Additionally, the biohydrogenation activity of solid-associated bacteria (SAB) and liquid-associated bacteria (LAB) was examined and compared with the activity of the non-fractioned I. prostoma monofaunated rumen fluid (LAB + SAB). Both SAB and LAB were involved in rumen biohydrogenation of C18:2n-6. SAB fractions performed the full hydrogenation reaction to C18:0 while C18:1 fatty acids, predominantly C18:1t10 and C18:1t11, accumulated in the LAB fractions. SAB and LAB sequence analyses were mainly related to the genera Butyrivibrio and Pseudobutyrivibrio with 12% of the SAB clones closely related to the C18:0 producing B. proteoclasticus branch. In conclusion, this work suggests that I. prostoma and its associated bacteria play no role in C18:2n-6 biohydrogenation, while LAB convert C18:2n-6 to a wide range of C18:1 fatty acids and SAB produce C18:0, the end product of rumen lipid metabolism.

This paper constitutes a review on the welfare aspects of piglet castration that considers the scientific literature published after 2004. Castrating during the neonatal period (1 to 3 days of age) is clearly painful. In addition, inflammatory processes may take place at the sites of incision, thus adding further pain to the procedure. Surgical castration with general and local anaesthesia, in combination with long-term analgesia, has been shown to reduce pain but the additional handling and injection of the anaesthetic, the effectiveness and limited safety margins have to be thoroughly evaluated. Raising entire males during the whole fattening period or immunocastration of males towards the end of the fattening period are other alternatives with welfare benefits in young pigs compared to current surgical castration, but with some potential welfare drawbacks regarding handling stress and behaviour during fattening. Based on the current knowledge, it can be concluded that sperm sexing and raising entire males after genetic control of boar taint are potentially preferable alternatives to current practices, but need further research, as these methods are not yet available.

The effect of commensal microbiota and feeding corn or wheat/barley-based diets on the apparent gastrointestinal absorption of dl-methionine (MET) and 2-hydroxy-4-methylthiobutanoic acid (MHA-FA) was studied in conventional (n = 32) and gnotobiotic pigs (n = 24). Conventional pigs (CON) were vaginally delivered and sow-reared until weaning at 14 days of age. Gnotobiotic pigs were derived by caesarian section and reared in HEPA (high efficiency particulate air)-filtered isolator units with ad libitum access to a milk-based formula. Corn or wheat/barley-based diets were fed to all pigs from 14 to 24 days of age. At 24 days of age, after an overnight fast, pigs were fed 20 g/kg BW of experimental diet supplemented with 107 Bq of either 3H-l-MET or 3H-l-MHA-FA per kg of feed and chromic oxide (0.5% wt/wt). Pigs were killed for sample collection 3 h after consuming the meal. Residual 3H-MET and 3H-MHA-FA were estimated in gastrointestinal contents as the ratio of 3H : chromic oxide in digesta samples to the ratio of 3H : chromic oxide in feed. In CON pigs, feeding a wheat/barley-based diet increased (P < 0.05) total aerobes, whereas supplementation with MHA-FA increased (P < 0.05) total aerobes and lactobacilli populations in proximal small intestine (SI). Among the gnotobiotic pigs, bacterial contamination occurred such that eight pigs (two isolators) were monoassociated with a Gram-negative bacteria closely related to Providencia spp. and 16 pigs (four isolators) were monoassociated with Gram positive Enterococcus faecium. Species of monoassociated bacterial contaminant and diet composition did not affect residual methionine or MHA-FA in digesta. In both CON and monoassociated (MA) pigs, methionine and MHA-FA were retained in stomach (92%) but disappeared rapidly from proximal SI. Residual methionine and MHA-FA in digesta was not different in MA pigs; however, in CON pigs, less (P < 0.01) apparent residual methionine was found in digesta recovered at 25% (from cranial to caudal) and 75% of SI length compared with MHA-FA. Apparent residual methionine was 16% and 8% compared with 34% and 15% for MHA-FA, at the 25% and 75% locations, respectively. In proximal SI tissue, significantly (P < 0.05) higher radioactivity (cpm/mg wet tissue) was associated with MET pigs (8.56 ± 0.47) as compared to MHA-FA ones (5.45 ± 0.50). This study suggests that microbial metabolism of MHA-FA increases retention in small intestinal digesta relative to methionine and contributes, in part, to the lower bioefficacy of MHA-FA compared to methionine.

Lactic acidosis is a major welfare issue affecting animal health and production systems such as dairy and feedlot beef. We used two bioassays to identify bioactive plants of Australia with the potential to prevent acidosis in ruminants. In the first bioassay, a potentially acidotic environment was induced by adding glucose to rumen fluid and pH and gas production were used to estimate the effect on acid production and microbial fermentation after 5-h incubation. Australian plants (n = 104) were screened for their ability to prevent a decline in the pH without inhibiting normal gas production, and five plants namely Eremophila glabra, Kennedia eximia, Acacia saligna, Acacia decurrens and Kennedia prorepens with such properties were identified. We investigated further the two top ranking plants, E. glabra and K. prorepens, in the second bioassay to determine the extent of their effect in vitro, by extending the incubation to 24 h and measuring d-lactate, and volatile fatty acids (VFA) in addition to pH and gas production. These were measured at 0, 5, 10, 16 and 24 h after inoculation. Eremophilaglabra maintained pH values that were higher and d-lactate concentrations that were lower than the control (P < 0.001), and comparable to the antibiotic-protected environment (AB; 12 μg of virginiamycin/ml). Eremophilaglabra and AB treatments did not restrict fermentation, as judged by gas production and VFA. Kennedia prorepens slowed the decline in pH and reduced the accumulation of lactate but inhibited gas production. We concluded that, in vitro, E. glabra was effective at controlling events that can lead to acidosis and the effect was comparable to that of virginiamycin, while K. prorepens was less effective than E. glabra and also inhibited fermentation.

In addition to its economic value, milk fat is responsible for many of milk’s characteristics and can be markedly affected by diet. Diet-induced milk fat depression (MFD) was first described over a century ago and remains a common problem observed under both intensive and extensive management. The biohydrogenation theory established that MFD is caused by an inhibition of mammary synthesis of milk fat by specific fatty acids (FA) produced as intermediates in ruminal biohydrogenation. During MFD, lipogenic capacity and transcription of key lipid synthesis genes in the mammary gland are down-regulated in a coordinated manner. Our investigations have established that expressions of sterol response element-binding protein 1 (SREBP1) and SREBP-activation proteins are down-regulated during MFD. Importantly, key lipogenic enzymes are transcriptionally regulated via SREBP1. Collectively, these results provide strong evidence for SREBP1 as a central signaling pathway in the regulation of mammary FA synthesis. Spot 14 is also down-regulated during MFD, consistent with a lipogenic role for this novel nuclear protein. In addition, SREBP1c and Spot 14 knock-out mice exhibit reduced milk fat similar to the magnitude and pattern of MFD in the cow. Application of molecular biology approaches has provided the latest chapter in the regulation of milk fat synthesis and is reviewed along with a brief background in nutritional regulation of milk fat synthesis in ruminants.

Capric acid (C10:0), a medium chain fatty acid, was evaluated for its anti-methanogenic activity and its potential to modify the rumen biohydrogenation of linoleic (C18:2n-6) and α-linolenic acids (C18:3n-3). A standard dairy concentrate (0.5 g), supplemented with sunflower oil (10 mg) and linseed oil (10 mg) and increasing doses of capric acid (0, 10, 20 and 30 mg), was incubated with mixed rumen contents and buffer (1 : 4 v/v) for 24 h. The methane inhibitory effect of capric acid was more pronounced at the highest (30 mg) dose compared to the medium (20 mg) (−85% v. −34%), whereas the lower dose (10 mg) did not reduce rumen methanogenesis. A 23% decrease in total short-chain fatty acid (SCFA) production was observed, accompanied by shifts towards increased butyrate at 20 mg and increased propionate at 30 mg of capric acid (P < 0.001). Capric acid linearly decreased the extent of biohydrogenation of C18:2n-6 and C18:3n-3, by up to 60% and 86%, respectively. This reduction was partially due to a lower extent of lipolysis when capric acid was supplemented. Capric acid at 20 and 30 mg completely inhibited the production of C18:0 (P < 0.001), resulting in an accumulation of biohydrogenation intermediates, mainly C18:1t10 + t11 and C18:2t11c15. In contrast to effects on rumen fermentation (methane production and proportions of SCFA), 30 mg of capric acid did not induce major changes in rumen biohydrogenation as compared to the medium (20 mg) dose. This study revealed the dual action of capric acid, being inhibitory to both methane production and biohydrogenation of C18:2n-6 and C18:3n-3.

Fertility can be defined as the natural capability of giving life. It is an important factor both for human medicine, where ~10% of the couples call for the services of assisted reproductive technologies, and for species of economic interest. In particular, in dairy cows, the recent years have seen a kind of competition between milk production and fertility, and genes improving fertility are now considered as parameters to be selected for. The study of fertility pathways is nevertheless made difficult by the strong impact of environmental factors on this parameter, as well as by the number of genes potentially involved (as shown by systematic transcriptome analysis studies in the recent years). One additional level of complexity is given by the fact that factors modulating fertility will probably be sex specific. The usage of mouse models has been one of the solutions exploited for tackling with these difficulties. Here, we review three different approaches using mice for identifying genes modulating fertility in mammals: gene invalidation, positional cloning and in vitro mutagenesis. These three approaches exploit specific characteristics of the mouse, such as the possibility of controlling precisely the environment, an excellent genetic characterization and the existence of genomic and molecular tools equalled only in humans. Many indications suggest that at least some of the results obtained in mice could be easily transposed to the species of interest.

This work set out to establish the response equations for hepatic blood flows in sheep and the contribution of hepatic arterial flow to hepatic venous blood flow due to changes in intake levels at constant diet composition. The FLORA (FLuxes across Organs and tissues in Ruminant Animals) database was used, and meta-analysis performed. The meta-analysis involved selection of published papers, identification of studies, description and coding of the selected dataset and statistical analysis using a covariance model. Meta-analyses were carried out using a within-study approach. To ensure absence of bias, the analysis incorporated interfering variables and factors studied in between-study comparisons. Variables concerned diet composition; qualitative factors concerned the physiological state of the animals and the methods used to measure blood flow. The results obtained showed that hepatic blood flows were positively related to intake in sheep. The magnitude of the response (as indicated by the slope) varied with the level of intake and the blood vessel (portal, hepatic venous or arterial). Nine linear relationships were established for the portal, hepatic venous and arterial blood flows as a function of dry matter intake (DMI) with below- and above-maintenance levels considered separately. Data obtained at below- and above-maintenance levels were considered together and four quadratic relationships were established for hepatic blood flows as a function of DMI. These relationships expressed a strong effect of intake on hepatic blood flows. The contribution of hepatic arterial to hepatic venous blood flow averaged 18.2%, with a wide variability. It did not vary significantly with level of intake. Although in between-study comparisons the arterial/venous blood flow was positively influenced by the organic matter digestibility of the diet, the relationships we obtained were robust. They can be used in models of net hepatic nutrient fluxes to predict variations and absolute values of hepatic blood flows from variations and absolute values of DMI.

Management of intestinal microbiota of monogastric animals has increased in importance since the ban of growth promoting antibiotics in many countries. Organic acids have been used as alternatives to antibiotics by many feed manufacturers. Regardless of the wide usage, the effect, dose response and mode of action of acids on intestinal microbes is poorly understood. In this study, we investigated the effects of dietary supplementation of three commonly used products, namely formic acid (FA) (90%), dl-methionine (DLM) (99%) and liquid methionine hydroxy analogue-free acid (88%), on ileal microbiota of pigs. Laboratory simulation system, mimicking swine ileum, was used to study the products at various concentrations and combinations. Furthermore, selected combinations were tested in a piglet trial to confirm the findings made in in vitro studies. FA turned out to have a dual effect on ileal microbiota. At concentrations below 0.5%, it significantly stimulated bacteria, but at higher inclusion rates it was highly inhibitory. This finding, which was consistent in in vitro and in vivo studies, implies that reducing the dose of FA does not lead to a diluted inhibitory effect, but in fact, an opposite, stimulatory effect on intestinal microbiota. It is highly important that feed compounders acknowledge this finding. Unlike FA, the inhibitory effect of methionine hydroxy analogue on ileal bacteria was linearly dose dependent and significant at inclusion levels above 0.2%, in vitro. Partial replacement of methionine hydroxy analogue by FA, or FA by methionine hydroxy analogue, led to an unpredictable outcome due to the dual effects of FA; e.g., a minor inclusion of added FA changed the inhibitory effect of methionine hydroxy analogue into microbial stimulation by FA. Inhibition of ileal microbiota by methionine hydroxy analogue was detected only in in vitro studies, suggesting that intact methionine hydroxy analogue may not have reached the ileum, in live animals. Therefore, if the target is to ensure the inhibitory effect of FA, the FA level in feed should be kept above 0.6%, and not reduced, if methionine hydroxy analogue is used as a methionine source instead of DLM. DLM was totally inert with regard to bacterial growth and metabolism, both in vitro and in vivo. The results of these studies reveal the importance of knowing how each acid product works. Inconsistent results in animal trials may have been partly due to quadratic dose–response effects of products, and unpredictable product combination effects.

The present study aimed to evaluate some cytochrome P450 metabolic enzyme activities in hepatic microsomes prepared from entire male pigs (uncastrated pigs), surgically castrated pigs and pigs immunized against gonadotropin-releasing hormone (immunocastrated pigs). The activities of the following enzymes were measured: ethoxyresorufin O-deethylase (EROD, CYP1A1/1A2), methoxyresorufin O-deethylase (MROD, CYP1A2), pentoxyresorufin O-depentylase (PROD, CYP2B), coumarin hydroxylase (COH, CYP2A) and p-nitrophenol hydroxylase (PNPH, CYP2A/2E1). The total cytochrome P450 contents were not affected by either surgical or immunocastration. Hepatic microsomal activities for EROD, PROD, COH and PNPH were lower in entire male pigs compared with surgically castrated and immunocastrated pigs (P < 0.05). Surgically and immunocastrated male pigs were similar with respect to EROD, MROD, PROD and COH activities (P > 0.05), whereas surgically castrated pigs exhibited lower PNPH activity compared with immunocastrated pigs (P = 0.029). The effect of different concentrations of testicular steroids – testosterone, 17β-estradiol, free estrone and androstenone – on enzyme activities was evaluated by in vitro microsomal study. Testosterone at the concentration of 8 pmol/ml inhibited EROD activities and estradiol-17β at the concentration of 1.8 pmol/ml inhibited PROD activities in hepatic microsomes from surgically castrated pigs. The highest concentration of androstenone (7520 pmol/ml) inhibited COH activities, whereas a 42-fold lower concentration of androstenone (180 pmol/ml) stimulated COH activities in surgically castrated pigs. Both free estrone (3.5 pmol/ml) and androstenone (55 pmol/ml) inhibited EROD activities in microsomes from entire male pigs. Stimulation of COH activities by the highest dose of free estrone (18 pmol/ml) was recorded in microsomes from entire male pigs. However, these effects of steroids were not concentration-dependent and the maximum extent did not exceed ±15% variation compared with the controls. There was no inhibition of PNPH activities in the hepatic microsomes from either entire or castrated pigs. In conclusion, we showed that EROD, PROD, COH and PNPH activities were lower in entire male pigs compared with those in surgically and immunocastrated pigs. Direct inhibition by the testicular steroids – testosterone, 17β-estradiol, free estrone and androstenone – was not the primary cause of the reduced enzyme activities.

This study aimed to assess the interaction between different dietary vitamin A (dVitA) levels and the same concentration of vitamin E (100 IU all-rac-α-tocopheryl acetate/kg feed) in growing-finishing pigs. In the first experiment, two fat sources × two dVitA levels (0 v. 100 000 IU) were used. The supplementation of 100 000 IU dVitA induced a range of 5.13 to 30.03 μg retinol/g liver, 62.78 to 426.88 μg retinol palmitate/g liver, and 0.60 to 1.96 μg retinol/g fat. Dietary fat did not affect retinol or retinyl palmitate deposition in pigs. The high concentration of dVitA produced lower fat and liver α-tocopherol concentrations, and increased susceptibility of muscle tissue to oxidation. A second experiment was carried out to study the retinol and α-tocopherol retention at different withdrawal times prior to slaughter (two dVitA levels; 0 v. 100 000 IU). A high dose of 100 000 IU vitamin A during a short 2-week period was enough to induce α-tocopherol depletion in liver and fat to a similar extent as when 100 000 IU were administered during the whole fattening. Muscle, fat and liver α-tocopherol concentrations were not affected by dVitA in the 1300–13 000 IU/kg range, but liver α-tocopherol concentration was higher when vitamin A was removed from the vitamin mix 5 weeks prior to slaughter (experiment 3).

In order to determine the effect of dietary vitamin E level and basal diet on vitamin E status, performance and tissue fatty acid content, five groups of eight Suffolk × Charollais wether lambs with an initial live weight of 28.4 (s.d. 1.6) kg were allocated to one of five concentrate-based diets supplemented with all-rac-α-tocopheryl acetate to contain 30 mg (C-30), 60 mg (C-60), 120 mg (C-120), 250 mg (C-250) or 500 mg (C-500) α-tocopheryl acetate/kg dry matter (DM), for 63 days. Two additional groups of eight lambs entered the study at 31.2 (s.d. 3.3) kg and were fed grass silage and 400 g/day concentrate for 56 days, with the whole diet providing the equivalent of 60 mg (S-60) or 500 mg (S-500) α-tocopheryl acetate/kg DM. Lambs were weighed and blood samples obtained by venipuncture weekly. Dietary vitamin E level did not affect performance (P > 0.05), but lambs fed grass silage grew more slowly (P < 0.001) and had a higher (P < 0.001) feed conversion ratio (kg feed/kg gain) than those fed concentrates. At day 0 plasma α-tocopherol concentrations were 0.8 μg/ml and did not differ between treatments (P > 0.05). Plasma α-tocopherol concentrations then decreased in all lambs except for those fed S-500, which increased, and at slaughter were (μg/ml) 0.07, 0.23, 0.39, 0.76 and 1.57 in C-30, C-60, C-120, C-250 and C-500 and 1.18 and 1.93 in S-60 and S-500, respectively. At slaughter, muscle and liver α-tocopherol concentrations were in the deficiency range for lambs fed C-30, C-60 or C-120, whereas plasma creatine kinase and tissue polyunsaturated fatty acids were unaffected by dietary vitamin E level, but creatine kinase levels were higher (P < 0.05) and glutathione peroxidise levels lower (P < 0.001) in lambs fed grass silage than concentrates alone. Muscle and liver α-tocopherol concentrations were 1.8- and 4.1-fold higher in lambs fed S-60 than C-60, but there was less of a difference between lambs fed S-500 or C-500 with muscle and liver differences of 0.4- and 0.7-fold, respectively. Tissue n-3 polyunsaturated fatty acid concentrations were higher (P < 0.05) and n-6 fatty acids lower in lambs receiving the grass silage compared to concentrate-based diets, but were not affected by dietary vitamin E level. It is concluded that lower plasma and tissue levels of α-tocopherol are present in lambs supplemented with all-rac-α-tocopheryl acetate on a concentrate compared to a mixed diet of silage and concentrates, and that normal growth can be achieved at tissue levels previously considered to represent deficiency.

The objective of the two studies was to determine the bioavailability of threonine (thr) and tryptophan (trp) in peanut meal, relative to l-thr and l-trp, for starter pigs using the slope-ratio bioassay. Basal diets (BDs) contained surfeit amounts of all amino acids for 10 to 20 kg pigs, except for thr (Experiment 1) or trp (Experiment 2). In the first study, four reference diets were formulated by supplementing the BD with 0, 0.4, 0.8 or 1.2 g of l-thr/kg at the expense of cornstarch; two test diets were formulated by replacing cornstarch in the BD with peanut meal at 32 or 64 g/kg of diet to supply 0.4 or 0.8 g thr/kg, respectively. Four reference diets consisting of the BD supplemented with 0, 0.15, 0.3 or 0.45 g of l-trp/kg at the expense of cornstarch and two test diets in which cornstarch in the BD was replaced with peanut meal at 30 or 60 g/kg of diet to supply 0.14 or 0.28 g trp/kg, respectively were used in the second study. Body weight gain responded in a linear way to supplemental l-thr or thr from peanut meal (P < 0.001). There was a linear response (P < 0.001) to thr supplementation from l-thr or peanut meal in gain-to-feed ratio. The addition of trp to the BD linearly increased (P < 0.05) body weight gain, feed intake and gain-to-feed ratio regardless of the trp source. Common-intercept, multiple linear regression in slope-ratio methodology using weight gain or gain-to-feed ratio as dependent variables and supplemental thr intake as independent variable gave relative bioavailability estimates of 71.9% or 75.7%, respectively. Corresponding values for trp were 92% and 75.7%. The fiducial limits for none of the relative bioavailability estimates included 100%. The data from these studies suggest that the bioavailabilities of thr and trp in peanut meal are less than those of l-thr and l-trp, and that the bioavailabilities of thr and trp in peanut meal are 72% to 76% and 76% to 92%, respectively.

A feeding trial involving four Thoroughbred race horses was undertaken to establish whether inclusion of grape seed extract (GSE) in the diet of horses undergoing mild exercise had any effects on their general health, intake and digestion. Supplementation with GSE had no effect on either feed or water intake of the horses and the supplement was readily palatable to the horses at all levels of inclusion. Feeding GSE caused no adverse effects in terms of animal health (temperature, pulse and respirations rates), and there were some positive effects related to a presumed alteration in fermentation in the hindgut. Feeding GSE increased faecal pH, changing from acid faeces (pH 6.6) when no GSE was fed to neutral faeces (pH 7.0) when 150 mg GSE/kg body weight (BW) was fed. In addition, blood glucose concentrations were significantly (P < 0.05) decreased when GSE was fed at 100 and 150 mg/kg BW (5.50 ± 0.26 and 5.32 ± 0.72 mmol/l, respectively) compared with the control diet (5.77 ± 0.31 mmol/l). The actual mechanisms causing these alterations are yet to be elucidated, but could have important implications for the prevention of acidosis.