Biomedical subjects

W C McNabb

Publications and source records attributed to W C McNabb.

At least 19 recordsLinked to original sources

PubMed2006

In vivo anthelmintic activity of Dorycnium rectum and grape seed extract against Ostertagia (Teladorsagia) circumcincta and Trichostrongylus colubriformis in sheep.

AIM: To assess the in vivo anthelmintic activity of condensed tannins (CT) in the forage species Dorycnium rectum and Medicago sativa, and in an extract from grape (Vitus vinifera) seeds (GSE), against two species of parasite, Teladorsagia (Ostertagia) circumcincta and Trichostrongylus colubriformis, at different stages of their life cycle, in sheep that were parasite-naïve or previously exposed to nematodes. METHODS: In Trial 1, a factorial treatment structure was used to compare faecal nematode egg counts (FEC) and worm burdens in 40 weaned Romney lambs fed either the CT-containing forage D. rectum (12% dry matter; DM) or M. sativa (lucerne; 0.2% DM). Twenty naïve and 20 previously-exposed lambs were drenched free of parasites then reinfected with known species and numbers of parasites, and housed in pens indoors on a diet of lucerne pellets and chaffed hay. Groups of lambs (n=5 lambs per group) were fed one of the forages over one of two time periods within the parasite's life cycle. Six to nine days after the last feeding of fresh forages, faecal samples were collected for FEC, and all lambs were slaughtered and worm counts conducted. In Trial 2, 12 Suffolk x Romney lambs were surgically implanted with an abomasal cannula and then housed indoors in metabolism crates. After infection with parasites, six lambs were infused continuously over a 14-day period with a commercially available CT GSE (96% DM, made up to 34 g/L in water); the remaining lambs were infused with water. During infusion, samples were collected for egg hatch and larval development assays. After infusion, samples were collected for FEC, and all lambs were slaughtered and worm counts conducted. RESULTS: In Trial 1, there was a significant (p<0.001) difference in burdens of O. circumcincta between naïve lambs and those previously exposed to parasites, but no other differences were recorded. In Trial 2, lambs infused with GSE had significantly (p<0.05) fewer T. colubriformis at slaughter and significantly (p<0.001) fewer eggs hatched in the egg hatch assay (EHA) than for lambs infused with water. Overall, the differences attributable to GSE were small in magnitude, being an 11% drop in egg hatch, and an 18% drop in numbers of adult T. colubriformis after 14 days of continuous infusion. No other differences were recorded. CONCLUSION: The results indicate that the in vivo anthelmintic activity of these CT sources is, at best, modest and is unlikely to be of any practical value. Further, these data emphasise that in vitro activity is an unreliable indicator of in vivo efficacy for CT-containing forages and extracts.

Animals↗

PubMed2004

Adding nutritional value to meat and milk from pasture-fed livestock.

Staple meat and milk provide excellent nutrition, but when traditional foods and ingredients are tailored to meet the particular nutritional or lifestyle demands of a population they become even more attractive and valuable. These foods can be considered as delivery systems for health-promoting nutrients. Nutritional improvement of meat and milk can be achieved several ways, preferably by making desirable changes on-farm to directly improve the food without subsequent manipulations. Scope for these changes is limited by animal homeostasis, but alternatives may be less desirable. Methods in vivo that suit typical pastoral farming practice and can complement the solving of animal health and production problems include: selection of traits or phenotypes; specialty diets; long-acting parenteral supplements; and modification of ruminal microflora. Successful techniques to increase the concentration of calcium, selenium, iodine and iron in milk or meat are described. Manipulations to change composition are only one part of bringing tailored foods to market. Commercial realisation of these new products needs the initiative and collaboration of scientists, veterinarians, growers and producers responding to market pull. The uptake of future biotechnologies to capture more value inside the farm gate will also be required if the pastoral industry in New Zealand is to sustain a global competitive advantage.

Journal Article↗

PubMed2003

Whole-body fluxes and partitioning of amino acids to the mammary gland of cows fed fresh pasture at two levels of intake during early lactation.

The utilisation of essential amino acids (EAA) by the mammary gland of lactating dairy cows fed fresh forages was studied to provide basic information useful in designing strategies to increase the production of milk protein from pasture-fed dairy cows. The relationship between the flux of EAA in the whole body and their uptake by the mammary gland was determined in four cows in early lactation (length of time in milk 44 (SD 14.5) d) producing 21 (SD 4.0) kg milk/d. The cows were maintained in metabolism stalls and fed fresh perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) pasture ad libitum or restricted to 75 % ad libitum intake. The whole-body fluxes of amino acids (AA) were measured using an arterio-venous infusion of universally (13)C-labelled AA. Whole-body fluxes of fourteen AA were estimated. Isotope dilution indicated that mammary utilisation accounted for one-third of the whole-body flux of EAA, with individual AA ranging between 17 and 35 %. Isoleucine, leucine, valine and lysine were the EAA with the greatest partitioning towards the mammary gland (up to 36 % of the whole-body flux), which could reflect a potentially limiting effect on milk protein synthesis. In the case of AA with low partitioning to the mammary gland (for example, histidine), it is suggested that non-mammary tissues may have priority over the mammary gland and therefore the supply of this AA may also limit milk protein synthesis.

Amino Acids↗

PubMed2002

Effects of grazing undrenched weaner deer on chicory or perennial ryegrass/white clover pasture on the viability of gastrointestinal nematodes and lungworms.

This study determined the in vitro effects on the viability of internal parasites of grazing undrenched weaner deer on either chicory (Cichorium intybus) or perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) pasture. One experiment investigated the hatching and development of gastrointestinal nematode eggs and larvae, and the development and motility of L1 lungworm (Dictyocaulus eckerti) larvae, and a second experiment used larval migration inhibition assays to test the viability of L1 lungworm larvae extracted from the faeces of weaner deer grazed on either chicory or pasture when they were incubated with rumen and abomasal fluids from fistulated deer also grazing on chicory or pasture. The incubations were undertaken with and without added condensed tannins purified from chicory and with or without polyethylene glycol (PEG) to bind the tannins. Chicory had no effect on the hatching and development of gastrointestinal nematode eggs and larvae. Grazing chicory reduced the number of lungworm larvae developing to the L3 stage, and L1 lungworm larvae from the faeces of chicory-grazed deer were less viable in rumen and abomasal fluid than larvae from pasture-grazed animals. Abomasal fluid was significantly (P < 0.001) less inhibitory to the migration of L1 lungworms than rumen fluid. When the larvae were incubated in rumen and abomasal fluids from chicory-grazed deer, their passage through sieves was significantly (P < 0.001) reduced in comparison with when they were incubated in the fluids from pasture-grazed deer Adding condensed tannins to rumen fluid increased the inhibition of the migration of L1 lungworm larvae but PEG removed this inhibition; this effect was not observed with abomasal fluid.

Animal Feed↗

PubMed2002

Effect of condensed tannins on egg hatching and larval development of Trichostrongylus colubriformis in vitro.

The effects of condensed tannins extracted from seven forages on the viability of the eggs and first stage (L1) larvae of the sheep nematode Trichostrongylus colubriformis were evaluated in in vitro assays. The extracts of condensed tannins were obtained from Lotus pedunculatus (LP), Lotus corniculatus (LC), sulla (Hedysarum coronarium), sainfoin (Onobrychus viciifolia), Dorycnium pentaphylum (DP), Dorycnium rectum (DR) and dock (Rumex obtusifolius). Extracts containing 200 to 500 microg/ml reduced the proportion of eggs that hatched. The larval development assay was used to evaluate the effect of the extracts on the development of either eggs or L1 larvae to L3 infective larvae. Development was allowed to proceed for seven days by which time the larvae in control incubations had reached the infective L3 stage. Extracts containing 200 microg/ml from LP, DP, DR or dock prevented egg development, and only 11, 8 and 2 per cent of the eggs developed to L3 larvae with extracts from LC, sulla and sainfoin, respectively. When the concentration was 400 microg/ml no eggs developed to L3 larvae. The addition of the extracts after hatching also inhibited the development of L1 to L3 larvae; 200 microg/ml extracted from LP, LC, sulla, sainfoin, DP, DR and dock resulted in only 14, 18, 17, 15, 14, 16 and 4 per cent of L1 larvae developing to the L3 stage compared with 85 per cent for controls, and 400 microg/ml further reduced the development of L1 larvae. Statistical analyses showed that when the extracts were added before hatching they were significantly (P<0.001) more effective at inhibiting the larval development than when they were added after hatching. The condensed tannins from dock had the greatest inhibitory effect on egg development followed by the tannins from DR, sainfoin, DP, LP, sulla and LC.

Animals↗

PubMed2002

Lotus corniculatus condensed tannins decrease in vivo populations of proteolytic bacteria and affect nitrogen metabolism in the rumen of sheep.

Condensed tannins in forage legumes improve the nutrition of sheep by reducing ruminal degradation of plant protein and increasing crude protein flow to the intestine. However, the effects of condensed tannins in forage legumes on rumen bacterial populations in vivo are poorly understood. The aim of this study was to investigate the specific effects of condensed tannins from Lotus corniculatus on four proteolytic rumen bacteria in sheep during and after transition from a ryegrass (Lolium perenne)-white clover (Trifolium repens) diet (i.e., low condensed tannins) to a Lotus corniculatus diet (i.e., higher condensed tannins). The bacterial populations were quantified using a competitive polymerase chain reaction. Lotus corniculatus was fed with or without ruminal infusions of polyethylene glycol (PEG), which binds to and inactivates condensed tannins, enabling the effect of condensed tannins on bacterial populations to be examined. When sheep fed on ryegrass-white clover, populations of Clostridium proteoclasticum B316T, Butyrivibrio fibrisolvens C211a, Eubacterium sp. C12b, and Streptococcus bovis B315 were 1.5 x 10(8), 1.1 x 10(6), 4.6 x 10(8), and 7.1 x 10(6) mL(-1), respectively. When the diet was changed to Lotus corniculatus, the average populations (after 8-120 h) of C. proteoclasticum, B. fibrisolvens, Eubacterium sp., and S. bovis decreased (P < 0.001) to 2.4 x 10(7), 1.1 x 10(5), 1.1 x 10(8), and 2.5 x 10(5) mL(-1), respectively. When PEG was infused into the rumen of sheep fed Lotus corniculatus, the populations of C. proteoclasticum, B. fibrisolvens, Eubacterium sp., and S. bovis were higher (P < 0.01-0.001) than in sheep fed Lotus corniculatus without the PEG infusion, with average populations (after 8-120 h) of 4.9 x 10(7), 3.8 x 10(5), 1.9 x 10(8), and 1.0 x 10(6), respectively. Sheep fed the Lotus corniculatus diet had lower rumen proteinase activity, ammonia, and soluble nitrogen (P < 0.05-0.001) than sheep that were fed Lotus corniculatus plus PEG. The Lotus corniculatus diet reduced rumen nitrogen digestibility (P < 0.05) and ammonia pool size and increased the flow of undegraded feed nitrogen to the abomasum. The nitrogen intake, rumen non-ammonia nitrogen pool size, rumen microbial non-ammonia nitrogen pool size, and abomasal microbial non-ammonia nitrogen fluxes were similar both in sheep fed only Lotus corniculatus and in sheep fed Lotus corniculatus plus PEG, but nonmicrobial non-ammonia nitrogen flux to the abomasum was higher (P < 0.01) for the sheep fed only Lotus corniculatus. Although condensed tannins in Lotus corniculatus reduced the populations of some proteolytic bacteria, total ruminal microbial protein and microbial protein outflow to the abomasum were unchanged, suggesting a species-specific effect of condensed tannins on bacteria in the rumen.

Animals↗

PubMed2001

The effect of condensed tannins from Lotus pedunculatus and Lotus corniculatus on the growth of proteolytic rumen bacteria in vitro and their possible mode of action.

Five strains of proteolytic rumen bacteria were treated with condensed tannins (CT) purified from Lotus pedunculatus and Lotus corniculatus to investigate their effect on the growth of these bacteria in vitro. Streptococcus bovis NCFB 2476, Eubacterium sp. C124b, Prevotella bryantii B14, Butyrivibrio fibrisolvens H17c, and Clostridium proteoclasticum B316T were tested against 200, 400, and 600 microg CT x mL(-1) extracted from L. pedunculatus and L. corniculatus. In the absence of CT, all bacterial strains showed typical growth and reached maximum optical density (OD) after 6-8 h of incubation in a plant protein medium. Growth of Eubacterium sp., P. bryantii, and B. fibrisolvens was inhibited (P < 0.01-0.001) more by the CT from L. pedunculatus than by the CT from L. corniculatus. All strains continued to grow in the presence of 200 microg x mL(-1) of the CT from L. pedunculatus, but attained significantly (P < 0.05-0.01) lower maximum OD600 values than (minus CT) controls, except for S. bovis. At 400 and 600 microg x mL(-1), the addition of CT from L. pedunculatus inhibited (P < 0.05-0.001) the growth of all bacterial strains tested compared with controls. The growth of Eubacterium sp. and P. bryantii was stimulated for the first 4-6 h of incubation (P < 0.001) by 200 microg x mL(-1) of CT from L. corniculatus, but then declined leading to a significant difference in OD values compared with the controls. At 400 microg x mL(-1), the CT from L. corniculatus reduced (P < 0.05-0.01) the growth of all strains except S. bovis, while 600 microg x mL(-1) inhibited (P < 0.01-0.001) the growth of all strains. To study the mechanism of CT action, the degradation of the large subunit (LSU) of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco; Fraction 1 Leaf protein) was followed after bacterial cells or Rubisco were preincubated with CT extracted from L. corniculatus and L. pedunculatus. Both preincubations decreased LSU degradation, but they differed in their response to polyethylene glycol (PEG) addition. Addition of PEG to CT-Rubisco preincubations negated the effects of CT, while PEG addition to CT-bacteria preincubations did not. This implies that the CT-bacterial interaction is stronger than the CT-Rubisco interaction or the interaction is of a different type. Also, L. pedunculatus CT reduced the degradation of the LSU to a greater extent than the CT from L. corniculatus when preincubated with bacteria.

Animals↗

PubMed2001

Immunohistochemical detection of myogenic cells in muscles of fetal and neonatal lambs.

Previous studies have implied that myonuclei accumulation in a muscle is more important than myofibre number in the determination of muscle size in fetal/neonatal lambs. However, due to the lack of a reliable marker, the role of myogenic precursor nuclei (satellite cells) in myofibre hypertrophy in late fetal and postnatal life is not well understood. In this study, MyoD was shown to be a useful marker for actively proliferating satellite cells in both fetal and neonatal lambs. MyoD was used to determine whether there were differences in the number of actively proliferating satellite cells between single and twin fetuses/neonates, which may explain at least some of the difference in myofibre size observed near birth. Eighteen single-bearing and 9 twin-bearing Coopworth ewes were randomly assigned to one of three slaughter groups (100, 120 and 140 days of gestation). The remaining ewes were kept on pasture until 20 days postpartum at which time 4 single and 4 twin lambs were sacrificed. Twin fetuses/neonates had lower body weights and muscle weights compared to singles. Lower muscle weights in the twins were associated with smaller myofibre cross-sectional areas and lower total nuclei numbers and myogenic precursor cell numbers per muscle in selected hind-limb muscles. These results indicate that myofibre hypertrophy in late gestation and early postnatal life is related to myogenic precursor cell number which may have important implications for growth potential of the growth-restricted fetus.

Animals↗

PubMed2000

Effect of condensed tannins extracted from four forages on the viability of the larvae of deer lungworms and gastrointestinal nematodes.

The inhibitory activity of condensed tannins extracted from four forage legume plants were evaluated by using a larval migration inhibition assay. The first (L1) and third (L3) stages of deer lungworm (Dictyocaulus viviparus), and the third stage (L3) of deer gastrointestinal nematodes were incubated with tannins extracted from Lotus pedunculatus, Lotus corniculatus, sulla (Hedysarum coronarium) and sainfoin (Onobrychus viciifolia). The tannins extracted from all the forages had inhibitory activity as measured by their ability to paralyse the larvae and inhibit them from passing through sieves. At the highest concentration used (1200 microg/ml) the tannins extracted from sainfoin had the highest activity against ensheathed L1 lungworm larvae (58 per cent), followed by L. pedunculatus (45 per cent), sulla (42 per cent) and L. comiculatus (35 per cent) when the larvae were incubated at 37 degrees C. The same trend, but with lower activities, was observed when the larvae were incubated at 22 degrees C. Anthelmintic activity against L3 lungworm larvae was evaluated by measuring the death rate of ensheathed L3 larvae after incubation with condensed tannins for two, 24 and 48 hours at room temperature (22 degrees C). The death rate was significantly higher (P<0.001) after 48 hours incubation than after two hours or 24 hours, and significantly higher (P<0.001) after 24 hours than after two hours incubation. Condensed tannins from sainfoin had the highest inhibitory activity followed by L. pedunculatus, sulla and L. comiculatus. The tannins from sainfoin also had the highest activity against L3 larvae of gastrointestinal nematodes, followed by L. pedunculatus, sulla and L. comiculatus. Exsheathed larvae of gastrointestinal nematodes were significantly more susceptible to the action of the tannins than ensheathed larvae.

Animals↗

PubMed2000

The phenols and prodelphinidins of white clover flowers.

White clover flowers (Trifolium repens L.) contain an abundance of phenolics, namely cis- and trans-p-coumaric acid 4-O-beta-D-glucopyranoside, the 3-O-beta-D-galactopyranosides of myricetin, quercetin and kaempferol together with two new derivatives namely myricetin 3-O-(6"-acetyl)-beta-D-galactopyranoside and kaempferol 3-O-(6"-acetyl)-beta-D-galactopyranoside. Gallocatechin, epigallocatechin, gallocatechin-(4alpha-8)-epigallocatechin and their corresponding prodelphinidin polymers were also present. The 13C-NMR spectra showed that the polymers consisted of only gallocatechin and epigallocatechin monomeric units with the latter being about twice as abundant in the extenders but only slightly more than that in the terminating units. The average degree of polymerization was estimated by 13C-NMR and ES-MS, which gave a remarkably consistent result of about 5.8 flavanol units.

Anthocyanins↗

PubMed2000

Phenolic glycosides of forage legume Onobrychis viciifolia.

A chemical examination of the extractives of the leaves of sainfoin was undertaken as part of a programme directed at understanding the factors which may contribute to its nutritive value as animal feed. Among the low molecular weight phenolic compounds characterized were seven cinnamic acid derivatives and nine flavonoid glycosides all of which were identified by NMR spectroscopy. Included among these compounds were two new natural hydroxycinnamic esters namely methyl 6-O-p-trans-coumaroyl-beta-D-glucopyranoside and methyl 6-O-p-cis-coumaroyl-beta-D-glucopyranoside and a novel flavonoid chrysoeriol-4'-O-(6''-O-acetyl)-beta-D-glucopyranoside.

Chromatography, High Pressure Liquid↗

PubMed2000

Muscle growth, cell number, type and morphometry in single and twin fetal lambs during mid to late gestation.

Muscle growth, myofibre number, type and morphometry were studied in large hindlimb muscles of single and twin fetal lambs during mid to late gestation. Placental insufficiency, evident by lower total placentome weight and number per fetus, resulted in reduced fetal weights from 100 to 140 days gestation in twins compared with singletons (at 140 days: 5016 +/- 108 g v. 5750 +/- 246 g, respectively; P<0.05). However, competition between littermates did not consistently reduce muscle mass (15-22%) until 140 days gestation. Apparent myofibre number increased with age, indicating that the full complement of myofibres in some large hindlimb muscles may be achieved during early postnatal life. Litter size did not impact on apparent myofibre number in the semitendinosus, plantaris or gastrocnemius muscles. However, a transient effect on myofibre number in the adductor femoris muscle was observed from 80-120 days gestation. The phenotypic maturation of myofibres was unaffected by increasing litter size. Smaller muscle mass in twins was associated with smaller myofibre cross-sectional area in the semitendinosus, adductor femoris and gastrocnemius muscles at 140 days gestation. A similar trend was observed for the plantaris muscle. These results indicate that while competition between littermates for nutrients in late gestation can impact on both fetal and muscle mass, the fetus has the capacity to buffer against the effects of restricted nutrient supply on myofibre hyperplasia and phenotypic maturation, but myofibre hypertrophy is compromised.

Animals↗

PubMed2000

Morphometric analysis of myofibre development in the adductor femoris muscle of single and twin fetal lambs.

Cellular development of the adductor femoris muscle from twin and single fetuses was studied at 140 days gestation to evaluate the effect of moderate fetal growth retardation on myofibre development. Twin fetuses had lower bodyweights (13%) and disproportionately small adductor femoris muscle weights (22%) compared with single fetuses. Reduced muscle mass was associated with smaller myofibre cross-sectional areas (CSA) and lower DNA content (22%), indicative of fewer myonuclei and retarded myofibre hypertrophy. Myofibre number and the phenotypic maturation of the myofibres were similar between twins and singletons. These results indicate that even modest growth restriction during fetal life can negatively influence myofibre hypertrophy, highlighting the importance of fetal nutrition for muscle growth. Large muscles, such as the adductor femoris, have intrafascicularly terminating myofibres, which necessitates accurate sampling of the muscle when investigating possible perturbations in morphological characteristics (e.g. between singletons and twins). The second objective of the present study was to investigate the impact of the sampling site on the morphological parameters of the adductor femoris muscle. The apparent total myofibre number decreased from the proximal to the distal region of the adductor femoris muscle. The apparent number of slow-twitch fibres also decreased from the proximal to the medial region, but was not different between the medial and distal regions of the muscle. Similarly, myofibre CSA differed between the medial and distal regions. These results indicate that, particularly with large muscles, such as the adductor femoris, which has intrafascicularly terminating myofibres, single site sampling for the determination of morphological fibre characteristics may generate misleading results and that careful selection of the sampling area may be necessary.

Animals↗

PubMed2000

The effect of condensed tannins from seven herbages on Trichostrongylus colubriformis larval migration in vitro.

The effects of condensed tannins (CT) extracted from seven forages on the motility of the economically important nematode, Trichostrongylus colubriformis (Giles, 1892), were evaluated by using a larval migration inhibition (LMI) assay. The assay involved incubation of third stage (L3) exsheathed T. colubriformis larvae with CT extracted from Lotus pedunculatus, Lotus corniculatus, sulla (Hedysarum coronarium), sainfoin (Onobrychis viciifolia), Dorycnium rectum, Dorycnium pentaphyllum and dock (Rumex obtusifolius) and measurement of larval migration through nylon mesh with a 20 microm pore size. At 100 microg ml(-1), CT from L. pedunculatus, L. corniculatus, sulla, sainfoin, D. rectum, D. pentaphyllum and dock inhibited 20%, 10%, 15%, 25%, 28%, 32% and 27% of the larvae, respectively from passing through the sieves compared to controls (no CT added). At 1000 microg CT ml(-1), CT purified from D. pentaphyllum had the highest inhibitory activity (63%) against 1-month old larvae followed by sainfoin (59%), L. pedunculatus (57%), D. rectum (53%), dock (50%), sulla (40%) and L. corniculatus (37%). Seven-month old larvae were more sensitive to the action of CT than 1-month old larvae (P < 0.001). Addition of 2 microg polyethylene glycol ([PEG] per microg CT; to remove the effect of CT) eliminated 81-93% of the CT activity (P < 0.001) compared to incubations without PEG. The impact of CT on larval migration suggests a possible role for these plants in ruminant diets as a means to reduce dependence upon proprietary anthelmintics.

Age Factors↗

PubMed1999

The implications of condensed tannins on the nutritive value of temperate forages fed to ruminants.

New methodology for measuring forage condensed tannin (CT) content is described and the effects of CT upon forage feeding and nutritive value for ruminant animals are reviewed. CT react with forage proteins in a pH-reversible manner, with reactivity determined by the concentration, structure and molecular mass of the CT. Increasing concentrations of CT in Lotus corniculatus and Lotus pedunculatus reduce the rates of solubilization and degradation of fraction 1 leaf protein in the rumen and increase duodenal non-NH3 N flow. Action of medium concentrations of total CT in Lotus corniculatus (30-40 g/kg DM) increased the absorption of essential amino acids from the small intestine and increased wool growth, milk secretion and reproductive rate in grazing sheep without affecting voluntary feed intake, thus improving the efficiency of food conversion. High concentrations of CT in Lotus pedunculatus (75-100 g/kg DM) depressed voluntary feed intake and rumen carbohydrate digestion and depressed rates of body and wool growth in grazing sheep. The minimum concentration of CT to prevent rumen frothy bloat in cattle is defined as 5 g/kg DM and sheep grazing CT-containing legumes were shown to better tolerate internal parasite infections than sheep grazing non CT-containing forages. It was concluded that defined concentrations of forage CT can be used to increase the efficiencies of protein digestion and animal productivity in forage-fed ruminants and to develop more ecologically sustainable systems of controlling some diseases under grazing.

Amino Acids, Essential↗

PubMed1997

Maternal constraint influences muscle fibre development in fetal lambs.

The objective was to examine myogenesis in two situations expected to be characterized by maternal constraint: (i) in fetuses due to be born in spring (n=10) or autumn (n=10); and (ii) in single (n=16) and twin (n=20) fetal lambs. Maternal constraint operating through limitation of placental size, as measured by placentome weight per fetus, was evident in each study. Although a lower placental weight did not influence body and muscle weights of fetuses due to be born in the spring or autumn, twins had lower body and muscle weights than singles. Fibre number and average fibre cross-sectional (CS) area were differentially affected by season and fetal number. The differences in muscle fibre morphology between spring- and autumn-born fetuses suggest that muscle fibre development was influenced by maternal constraint in the absence of an effect on fetal weight. The differences in muscle fibre number and CS area in particular muscles from twin and single fetuses suggest that more severe maternal constraint, reflected in a lower placental size per fetus, not only influences fetal weight but can also affect muscle development.

Animals↗

PubMed1996

The effect of condensed tannins from heated and unheated cottonseed on the ileal digestibility of amino acids for the growing rat and pig.

The effect of condensed tannins (CT) from heated and unheated cottonseed on the apparent ileal digestibility of amino acids for the growing rat and pig was determined. In Expt 1, twenty-four rats were allocated to four semi-purified diets which contained cottonseed kernel and hulls as the only protein source. Two of the diets contained unheated solvent-extracted cottonseed kernel and hulls, while the remaining two diets contained similar material but which had been heat-treated by autoclaving at 110 degrees for 120 min. In Expt 2, twelve rats and twelve pigs were fed on four semi-purified diets containing commercial cottonseed meal (CSM) as the only protein source. Cr2O3 was added to all diets as an indigestible marker. For each pair of diets in both experiments, PEG was either included or excluded. The effect of CT was assessed by comparing control animals (-PEG; CT acting) with PEG-supplemented animals (+PEG; CT inactivated). Ileal contents from the terminal 150 and 450 mm of ileum were collected at slaughter, 7 h from the start of feeding, for the rats and pigs respectively. Apparent ileal amino acid digestibility for rats fed on the diet containing cottonseed kernel and hulls was significantly depressed by the heat treatment, particularly for lysine and threonine. On average, apparent ileal amino acid digestibility in the diets without PEG was decreased from 0.80 to 0.70 by heat treatment. Dietary cottonseed CT depressed apparent ileal protein digestibility in the pig and in the rat. The addition of PEG to the diets significantly increased the apparent ileal digestibility of N and some amino acids for the pigs and the rats. The mean increase in apparent ileal digestibility due to PEG addition for the fourteen amino acids was 2 percentage units in both species fed on the commercial CSM diets, and 2 or 4 percentage units in rats fed on the unheated or the heated cottonseed kernel and hull diets respectively. The effect of PEG was similar in the heated and unheated cottonseed kernel and hulls for most amino acids, but apparent ileal digestibilities of threonine, tyrosine and lysine were increased more by PEG in heated than in unheated CSM. Apparent ileal N digestibility was lower in the pig than in the rat. For several of the amino acids there were significant animal species differences in apparent ileal digestibility. Studies into the effects of cottonseed CT should be carried out in the target animal species. The commercial CSM had a low apparent ileal amino acid digestibility overall, particularly for the essential amino acids lysine and threonine. It was concluded that effects of heating did not eliminate the reversible reactivity of cottonseed CT on amino acid digestion in rats and pigs but rather appeared to increase it for threonine, tyrosine and lysine in Expt 1, causing large reductions in apparent ileal digestibility of these amino acids.

Amino Acids↗

PubMed1996

The effect of condensed tannins in Lotus pedunculatus on the solubilization and degradation of ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39; Rubisco) protein in the rumen and the sites of Rubisco digestion.

Three experiments were undertaken to determine the effect of condensed tannin (CT) in Lotus pedunculatus (45-55 g extractable CT/kg DM) on the digestion of the principal leaf protein, ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39; Rubisco; fraction 1 leaf protein). In two of the experiments Lotus pedunculatus was fed to sheep, with one group receiving a continuous intraruminal infusion (per fistulum) of PEG (molecular weight 3500) to bind and inactivate the CT (PEG group). The other group, which did not receive PEG, was termed the control sheep (CT acting). Expt 3 involved in vitro incubations of Lotus pedunculatus in buffered rumen fluid, with and without PEG added. In all experiments the results have been interpreted in terms of the effects of CT on Rubisco solubilization and degradation. Disappearance of N and Rubisco from Lotus pedunculatus suspended in polyester bags in the rumen was used as a measure of solubilization. Degradation was defined as the disappearance of Rubisco from in vitro incubations of Lotus pedunculatus in rumen fluid. In Expt 1, CT reduced the digestion of Rubisco in the rumen from 0.96 to 0.72 of intake (P < 0.01). Rubisco digestion in the small intestine was 0.27 of intake in control sheep and 0.04 of intake in PEG sheep. In Expt 2, PEG had no effect on the loss of Rubisco from Lotus pedunculatus contained in polyester bags which were incubated in the rumen, hence CT did not affect the solubilization of Rubisco. Observations in Expt 1 were confirmed by in vitro incubations in Expt 3, where PEG addition substantially increased the rate of degradation of plant protein to NH3. Addition of PEG decreased the period of time taken to degrade 50% of the Rubisco from about 13.8 h to about 3.0 h. It was concluded that the action of CT reduced the digestion of Rubisco in the rumen of sheep fed on fresh Lotus pedunculatus, and that this was primarily due to the ability of CT to slow its degradation by rumen micro-organisms, without affecting its solubilization. Both fresh-minced, and freeze-dried and ground lotus were used for in sacco and in vitro incubations; however, fresh-minced lotus was more suitable for the evaluation of protein solubilization and degradation in fresh forages.

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