G. B. Douglas

Effect of condensed tannins upon the performance of lambs grazing Lotus corniculatus and lucerne ( Medicago sativa )

A grazing experiment, conducted for 22 weeks in 1992/93 at Aorangi Research Station, AgResearch Grasslands, Manawatu, New Zealand, compared the productivity of weaned lambs grazing Lotus corniculatus (birdsfoot trefoil) and lucerne (Medicago sativa). Effects of condensed tannins (CT) in lotus were evaluated by studying the responses of lambs to twice daily oral supplementation with polyethylene glycol (PEG). A rotational grazing system with restricted feed allowance was used. Measurements were made of pre- and post-grazing herbage mass, the composition of the feed on offer and diet selected, voluntary feed intake (VFI), liveweight gain (LWG), carcass growth, wool growth and the concentration of metabolites in rumen fluid. For both lotus and lucerne swards, the diet selected was mainly leaf. Lotus contained 34 g total CT/kg dry matter in the diet selected, whilst there were essentially no CT in lucerne. Compared to lambs grazing lucerne, lambs grazing lotus had slightly lower VFI, and higher LWG, carcass weight gain, carcass dressing-out percentage and wool growth. PEG supplementation had no effect on these measurements or upon the composition of rumen fluid in lambs grazing lucerne. However, in lambs grazing lotus, PEG supplementation reduced wool growth (10.9 v. 12.1 g/day), slightly reduced LWG (188 v. 203 g/day), increased rumen ammonia concentration, and increased the molar proportions of iso-butyric, isovaleric and n-valeric acids and protozoa numbers in rumen fluid. PEG supplementation did not affect carcass gain, carcass fatness or the molar proportion of rumen acetic, propionic or n-butyric acids in lambs grazing lotus. It was concluded that the principal effect of CT in growing lambs grazing lotus was to increase wool growth without affecting VFI, thereby increasing the efficiency of wool production, that the greater rate of carcass gain of lambs grazing lotus than those grazing lucerne was mainly caused by factors other than CT and that CT did not affect the rumen fermentation of carbohydrate to major volatile fatty acids.

Effect of condensed tannins in Lotus corniculatus upon lactation performance in ewes

A grazing experiment was conducted for 8 weeks in the spring/summer of 1993 at Palmerston North, New Zealand, to study the effects of condensed tannins (CT) in Lotus corniculatus (birdsfoot trefoil cv. Grasslands Goldie) upon the lactation performance of ewes rearing twin lambs. Effects of CT were evaluated by studying the responses of ewes to twice daily oral supplementation with polyethylene glycol (PEG; MW 3500), which binds and inactivates CT. A rotational grazing system with restricted feed allowance was used. Measurements were made of pre- and post-grazing herbage mass, the composition of the feed on offer and diet selected, voluntary feed intake (VF1), milk yield and composition, liveweight gain and wool production. The concentration of metabolites in rumen fluid and in blood plasma was also measured. Lotus contained 35–5 g total nitrogen and 44–5 g total CT/kg dry matter in the diet selected, with an in vitro digestibility of 73%. At peak lactation (weeks 3 and 4) milk yield and composition were similar for control (CT-acting) and PEG-supplemented (CTinactivated) ewes but, as lactation progressed, the decline in milk production and in the secretion rates of protein and lactose were less for control than for PEG-supplemented ewes. In mid and late lactation (weeks 6–11), control ewes secreted more milk (21 %), more milk protein (14%) and more lactose (12%) than PEG-supplemented ewes. Milk fat percentage was lower for control than for PEG-supplemented ewes, but secretion rates of fat were similar for the two groups. VFI, liveweight gain and wool growth were similar for both groups. Plasma urea and glucose concentrations were lower for control than for PEG-supplemented ewes, but concentrations of non-esterified fatty acids (NEFA), growth hormone and insulin were similar for the two groups. The concentrations of ammonia and molar proportions of iso -butyric, iso -and n -valeric acids in rumen fluid were lower for control than for PEG-supplemented ewes; molar proportions of acetic, propionic and H-butyric acids were similar for the two groups. It was concluded that for ewes rearing twin lambs grazing L. corniculatus , the action of CT increased milk yield and the secretion rates of protein and lactose without affecting VFI, thereby increasing the efficiency of milk production. The increased milk production did not appear to be mediated by effects on plasma concentrations of growth hormone or insulin.

Effect of condensed tannins upon body growth, wool growth and rumen metabolism in sheep grazing sulla ( Hedysarum coronarium ) and perennial pasture

Areas of sulla ( Hedysarum coronarium ) and pasture ( Lolium perenne/Trifolium repens/Holcus lanatus ) were grazed by young sheep (29·5–34·8 kg initial liveweight) in four experiments, and effects upon body growth, wool growth and rumen metabolism were measured. Sulla contained 40–50 g condensed tannins (CT)/kg DM, whilst the pasture contained small amounts of CT (2–6 g/kg DM). After chewing during eating, a lower proportion of total CT was readily extractable and greater proportions were protein-bound and fibre-bound. Nutritional effects attributable to CT were assessed by oral administration of polyethylene glycol (PEG), which binds and inactivates CT, to half the animals grazing each forage. Rates of body growth were consistently higher for lambs grazing sulla than those grazing pasture, with the CT concentration in sulla being neither stimulatory or inhibitory to body growth or voluntary feed intake (VFI). The action of CT reduced carcass fatness in sheep fed both diets, in the one experiment where this was measured. CT present in both sulla and pasture decreased rumen ammonia concentration and decreased molar proportions of iso-butyrate and iso and n -valerate. During spring and early summer, when wool growth rates were highest, CT present in both pasture and sulla increased wool growth rate; when wool growth rates were low during winter, CT had no effect upon the wool growth of sheep grazing either forage. Numbers of protozoa and molar proportions of n -butyrate in rumen fluid were increased by CT in sheep grazing sulla but not pasture. It was concluded that the higher rates of body growth and VFI in lambs grazing sulla was most likely to be due to its very high ratio of readily fermentable: structural carbohydrate.

Ecological mitigation of hillslope instability: ten key issues facing researchers and practitioners

BackgroundPlants alter their environment in a number of ways. With correct management, plant communities can positively impact soil degradation processes such as surface erosion and shallow landslides. However, there are major gaps in our understanding of physical and ecological processes on hillslopes, and the application of research to restoration and engineering projects.ScopeTo identify the key issues of concern to researchers and practitioners involved in designing and implementing projects to mitigate hillslope instability, we organized a discussion during the Third International Conference on Soil Bio- and Eco-Engineering: The Use of Vegetation to Improve Slope Stability, Vancouver, Canada, July 2012. The facilitators asked delegates to answer three questions: (i) what do practitioners need from science? (ii) what are some of the key knowledge gaps? (iii) what ideas do you have for future collaborative research projects between practitioners and researchers? From this discussion, ten key issues were identified, considered as the kernel of future studies concerning the impact of vegetation on slope stability and erosion processes. Each issue is described and a discussion at the end of this paper addresses how we can augment the use of ecological engineering techniques for mitigating slope instability.ConclusionsWe show that through fundamental and applied research in related fields (e.g., soil formation and biogeochemistry, hydrology and microbial ecology), reliable data can be obtained for use by practitioners seeking adapted solutions for a given site. Through fieldwork, accessible databases, modelling and collaborative projects, awareness and acceptance of the use of plant material in slope restoration projects should increase significantly, particularly in the civil and geotechnical communities.

Liveweight gain and wool production of sheep grazing Lotus corniculatus and lucerne (Medicago sativa)

Abstract Two grazing experiments were conducted to compare the productivity of lactating ewes (Experiment 1) and weaned lambs (Experiment 2) grazing swards of Lotus corniculatus (birdsfoot trefoil; cv. Grasslands Goldie), lucerne (Medicago sativa; cv. Grasslands Oranga), and a mixture of lucerne and lotus. Measurements were made of pre‐ and post‐grazing herbage mass, the composition of the feed on offer and diet selected, and of voluntary feed intake (VFI; Experiment 2 only), body growth, and wool growth. From the agronomic measurements, it was concluded that the diet selected was mainly leaf in both experiments. Total condensed tannin (CT) content was 32–57 g/kg DM for lotus, 8–10 g/kg DM for the mixture, and negligible for lucerne (less than 2 g/kg DM). In Experiment 1, ewe wool production and lamb liveweight gain (LWG) did not differ between forages, but ewe LWG was greater on lotus than on lucerne (251 versus 65 g/day; P < 0.001), with the mixture being intermediate (115 g/day). In Experiment 2, VFI (...

Digestibility and effects of condensed tannins on digestion of sulla (Hedysarum coronarium) when fed to sheep

Abstract Sulla (Hedysarum coronarium) is a short‐lived perennial legume with an erect growth habit which is grown as a fodder crop in Mediterranean regions but is not common in New Zealand agriculture. Recent experimental work has shown potential benefits of sulla for reducing the impact and numbers of intestinal nematodes in sheep and possible benefits for wool production, so that a feeding trial was undertaken to determine its digestibility. Twelve sheep aged about 6 months were held in metabolism crates and fed sulla as a sole diet for the 20‐day experimental period. Sulla contains condensed tannins (CT) so that one group of 6 sheep were given twice‐daily oral drenches of polyethylene glycol (PEG) to bind with and deactivate the CT (PEG group) enabling a comparison with the undrenched Tannin group. The dry matter (DM) content of the sulla was 15.5%, comprising (DM basis) 33% leaf, 41% stem, and 26% flower, and all portions of the plant were eaten. The DM contained about 7.2% CT and 3.0% nitrogen (N). D...

Cutting management of willows (Salix spp.) and leguminous shrubs for forage during summer

Abstract An experiment was conducted to determine the potential value of shrubs for providing fodder for ruminants during periods of feed insufficiency. The work was undertaken at a moist and a dry site in the lower North Island of New Zealand in 1992/93 with four shrub species: Chamaecytisus palmensis (tagasaste); Dorycnium rectum (erect dorycnium); Salix kinuyanagi (kinuyanagi willow); and Salix matsudana x alba (hybrid willow). Five cutting regimes were adopted which varied in cutting frequency and height, with. the latter being either a low (L) or high (H) cutting height. There was a single low cut (L) in April at the end of the growing season, 2 cuts (LL and HL treatments) in February and April, and 3 cuts (LLL and HHL treatments) in December, February, and April. Three cuts during the season were investigated only at the moist site. Whole plant yields over the 1992/93 growing season were highest from a single cut in April. However, 2‐ and 3‐cut treatments sometimes gave yields as high as those from ...

Effect of condensed tannins in birdsfoot trefoil (Lotus corniculatus) and sulla (Hedysarum coronarium) on body weight, carcass fat depth, and wool growth of lambs in New Zealand

Abstract The effects of dietary condensed tannins (CT) on growth and performance of young male weaned lambs were measured during a 4‐month grazing trial when either birdsfoot trefoil (Lotus corniculatus) cv. Grasslands Goldie or sulla (Hedysarum coronarium) cv. Grasslands Aokau were fed. Each legume was offered at restricted and ad libitum allowances and the effects of CT were determined by giving half the lambs in each treatment a twice‐daily drench of polyethylene glycol (PEG; mol wt 3350) to deactivate the CT. Both agronomic and animal performance characteristics were recorded. Sulla had higher (P < 0.01) pre‐grazing herbage masses than birdsfoot trefoil (11.6 cf. 7.1 t DM ha−1) and sulla stem (<6 mm diam.) was eaten, in contrast to birdsfoot trefoil where stem was rejected by the lambs. The sulla and birdsfoot trefoil diets had similar protein concentrations in the DM, but sulla had a higher concentration of total CT (88 cf. 50 g CT kg1 DM) and less structural carbohydrate (189 cf. 328 g kg−1 DM) rela...

Silvopastoralism in New Zealand: review of effects of evergreen and deciduous trees on pasture dynamics

Complex interactions between livestock, trees and pasture occur in silvopastoral systems. Between trees and pasture, competition for soil resources (nutrients and water) occurs, becoming especially relevant when one of them is in scarce supply. Trees reduce light and water reaching the understorey layers according to tree density and canopy size. However, they may ameliorate extreme climatological features (reducing wind speed and evapotranspiration, and alleviating extreme temperatures), and improve soil properties, for example, deciduous tree litter may contribute to increased pH and soil nutrient concentrations. During tree establishment, there are generally negligible effects on pasture, irrespective of tree type. However, there is a decline in pasture production and nutritive value under shade with increasing tree age and higher stand density. Under the same conditions, deciduous trees affect pasture later (extinction point of pasture occurs at 85% of canopy closure) than evergreen trees (about 67% for Pinus radiata D. Don). This is mainly because deciduous trees have a leafless period that enables pasture recovery, and their litter smothers pasture less intensely because of its relatively fast decomposition. Silvopastoral studies conducted in New Zealand are reviewed to discuss these effects, and differences in the effects of evergreen and deciduous trees are shown using the examples of P. radiata, and Populus and Salix spp. respectively, which exist in many temperate countries. Future research needs are outlined.

Establishment of perennial species useful for soil conservation and as forages

Abstract Field establishment of 11 potentially useful soil conservation/revegetation species comprising three grasses (Dactylis glomerata, Festuca arundinacea, Thinopyrum ponticum), seven legumes (Astragalus cicer, Dorycnium hirsutum, Dorycnium pentaphyllum, Dorycnium rectum, Lotus corniculatus, Lupinus polyphyllus, Medicago sativa), and one herb (Sanguisorba minor) was examined at a low‐moderately fertile, seasonally dry site in the lower North Island from spring 1989 to winter 1991. Final seedling emergence ranged from c. 10% (for D. hirsutum, L. corniculatus, and L. polyphyllus) to c. 100% for S. minor, which was unique in achieving complete emergence. The duration of emergence was 3 (L. polyphyllus) to 13 (D. pentaphyllum, D. rectum) days and emergence of all species was completed within 25 days after sowing. Seedling survival 10 weeks after sowing was 40–90% for all species. An exception was A. cicer (4%) and the reason(s) for its low survival were unknown. Ground covers of M. sativa, S. minor, and T...