Response of young<Emphasis Type="Italic"> Tsuga heterophylla</Emphasis> to deer browsing: developing tools to assess deer impact on forest dynamics

We used dendroecology to describe and understand the consequences of deer browsing on regenerating western hemlock (Tsuga heterophylla). We compared tree shape, growth rate, height and age at four different sites in Haida Gwaii (British Columbia, Canada) that had trees representative of the range of deer impact on trees: (1) trees showing no sign of browsing, (2) escaped trees which were still browsed below the browse line and (3) stunted and heavily browsed trees. Repeated and intense browsing resulted in the small size, compact heavily ramified shape of stunted trees and in the short compact and ramified lower branches of escaped trees. These contrasted with the shape of non-browsed trees, a shape that was also found in escaped trees above the browse line. Before release, all browsed trees experienced stagnation in growth characterised by narrow rings (0.3 mm/year) and a small annual height increment (2.5 cm/year). At release, growth rate increased and stabilised: rings were wider (1.3 mm/year) and annual height increments were greater (10.5 cm/year). Non-browsed trees had a mean ring-width of 1.3 mm/year and an annual height increment of 22 cm/year. Delay in tree recruitment caused by deer varied from site to site. It had been about 15 years for the escaped trees and is estimated at 30–40 years for the stunted trees. Spatial variation in deer impact may reflect spatial variation of browsing pressure resulting from local differences in the availability of preferred forage or to differences in tree chemical defences/nutritional values.     

In vitro digestibility of seasonal forages used by wapiti and roe deer in northeastern China

Seasonal changes in in vitro dry matter digestibility (IVDMD) of five forage classes (browses, sedges, forbs. ferns and the bark of Ulmus spp.) used by wapiti and roe deer were determined in relation to chemical composition, using the two-stage technique of in vitro trial with rumen inocula from one wapiti and one roe deer captured in winter. Wapiti and roe deer showed remarkable fluctuation in IVDMD among seasons and forage classes. IVDMD decreased from 43.8-64.3% in spring to 29.4-40.5% in winter for wapiti, and from 52.4-77.4% in spring to 25.9-36.5% in winter for roe deer. There was significant variation in IVDMD among species of browses for wapiti and roe deer. IVDMD ranged from 28.5% to 58.7% in twigs and from 39.8% to 58.2% in leaves for wapiti, and from 24.1% to 67.7% in twigs and from 40.0% to 71.7% in leaves for roe deer. Roe deer had higher IVDMD (40.0-71.7%) in both leaves and twigs of browses than wapiti (35.9-58.7%) during snow-free seasons, but IVDMD of twigs was lower for roc deer (25.9-36.5%) than wapiti (29.4-38.4%) in winter. Significant multiple correlation was found between NDF and ADF, and IVDMD in sedges, forbs and ferns for both wapiti and roe deer, whereas only roe deer showed the significant multiple correlation for leaves of browses.     

Food selection by the silver leaf monkey,Trachypithecus auratus sondaicus,in relation to plant chemistry

Summary Samples of leaves and fruits exploited as food items byTrachypithecus auratus sondaicus were analysed for nitrogen content, acid detergent fibre (ADF), pepsin cellulase digestibility (CDIG), condensed tannins (CT), total phenolics (TP) and protein precipitation capacity (PP) and compared with fruits and leaves not eaten. Differences in chemical measures for items eaten and not eaten were not statistically significant but trends indicate that leaves may have been selected for their lower fibre content and greater digestibility. Fruits eaten also had a higher mean level of CDIG and lower mean level of ADF than fruits not eaten but these measures are not considered to be of major importance in fruit selection as CDIG was lower and ADF higher in fruits eaten than in leaves eaten. Levels of CT, TP and PP capacity were higher in fruits eaten than in fruits not eaten but lower in leaves eaten than in leaves not eaten. The role of tannins and phenolics in food selection is discussed. Leaves (and fruits) were not strongly selected on the basis of protein content. Approximately half the dietary intake ofT. auratus sondaicus was leaves, a protein-rich food source. Possibly, protein levels in foliage at Pangandaran were sufficient that selection for this nutrient was not required. A nutrient other than protein (for example, soluble carbohydrates) may have been maximised through food selection. The protein/ADF ratio may provide an indicator of the acceptability of foliage in a habitat as potential food for a colobine. However, this ratio did not govern food selection byT. auratus sondaicus at Pangandaran.     

Genetic mapping and analysis of quantitative trait loci affecting fiber and lignin content in maize

Plant cell walls of forage provide a major source of energy for ruminant animals. Digestion of cell walls is limited by the presence of lignin, therefore the improving the digestibility of forages by reducing lignin content is a major goal in forage crop breeding programs. A recombinant inbred line maize population was used to map quantitative trait loci (QTL) for neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL) of leaf-sheath and stalk tissues. All traits were positively genetically correlated. The larger genetic correlations were between NDF and ADF in sheaths (r = 0.84), NDF and ADF (r = 0.96), ADF and ADL (r = 0.83), and NDF and ADL (r = 0.76) in stalks. Twelve QTL were detected for NDF and 11 QTL for ADF in leaf-sheaths. Eight QTL detected for both traits were defined by the same or linked marker loci. Eight QTL were associated with leaf-sheath ADL. Eleven QTL were detected for NDF and ADF, and 12 QTL for ADL in stalks. Nine of eleven QTL detected for both NDF and ADF in stalks coincided in their genomic position. A high proportion of QTL detected for these traits had the same parental effects and genomic locations, suggesting that it is only necessary to select on one fiber component (NDF or ADF) to improve digestibility. Favorable correlated responses of unselected fiber components are expected due to coincident genomic locations of QTL and the high genetic correlation between fiber components. Several QTL detected in this study coincided in their positions with putative cellulose synthase genes from maize.     

African Elephants Loxodonta africana Amplify Browse Heterogeneity in African Savanna

There is a growing concern that the feeding habits of the African elephant, which include pushing over, uprooting and snapping trees, may have a negative impact on other herbivores. Browsed trees are known to respond by either increasing production (shoots and leaves) or defence (secondary compounds). It is not clear, however, what proportion of the browsed biomass can be made available at lower feeding heights after a tree is pushed over or snapped; thus, it is also unclear how the forage quality is affected. In a field survey in Kruger National Park, South Africa, 708 Mopane trees were measured over four elephant utilization categories: snapped trees, pushed‐over trees, uprooted trees and control trees. The elephants' impact on the leaf biomass distribution was quantified, and the forage quality (Ca, P, K and Mg, N, digestibility and condensed tannin [CT] concentrations) were analyzed. Pushed‐over and uprooted trees had the maximum leaf biomass at lower heights (<1 m), snapped trees at medium heights (1–2 m) and control trees at higher heights (>2 m). In all three utilization categories, the minimum leaf biomass was seven times higher than it was for control trees at a height of below 1 m. Leaf nitrogen content increased in all three categories and was significantly higher in snapped trees. CT concentrations increased slightly in all trees that were utilized by elephants, especially on granitic soils in the dry season. The results provide the insight that elephants facilitate the redistribution and availability of browse and improve the quality, which may positively affect small browsing herbivores.     

Browse on mahoe and kamahi leaf-fall as a trigger for possum control

Introduced brushtail possums (Trichosurus vulpecula) are controlled over large parts of New Zealand to protect canopy trees. The condition of canopy trees is one of the cues used to trigger possum control, but selecting an indicator of canopy tree condition is difficult because many factors unrelated to possum browsing can affect canopy condition, and indices based on canopy scoring may not always quickly detect real changes in possum herbivory. We therefore investigated the usefulness of the percentage of fallen mahoe (Melicytus ramiflorus) and kamahi (Weinmannia racemosa) leaves browsed by possums (‘fallen-leaf browse’ or ‘FLB’) as a trigger for control aimed at protecting these tree species. We collected leaves falling from kamahi and mahoe trees every two months for two years at two study areas in the central North Island, one with initially high possum abundance (Oriuwaka) and the other with low possum abundance (Otupaka). We classified each of 92 384 leaves as either not-browsed, possum-browsed or insect-browsed. There was a strong and similar seasonal pattern in the mean number of fallen leaves per tree for both mahoe and kamahi at both study areas; fewest leaves fell in winter, and the most leaves fell in spring and early summer. Mahoe and kamahi FLB exhibited a similar seasonal pattern at both areas, being lowest in winter and highest in spring and early summer. FLB for both mahoe and kamahi declined following control of possums to low densities at Oriuwaka. The proportion of fallen mahoe and kamahi leaves browsed by possums was small compared with those browsed by insects or not browsed. We show that spring/early summer (i.e. September–December) is the best period for sampling FLB and that the mean FLB can be estimated with a CV of 20% if one trap is randomly placed under the canopy of each of 24 randomly located trees. However, CVs were much larger in other seasons and when possum abundance was low. We consider FLB to be a sensible trigger for initiating possum control when the objective of control is to protect canopy trees, but further work is needed to determine the relationships between possum abundance, FLB, canopy condition, and key tree demographic rates.     

A comparative study of the apparent total tract digestibility of carbohydrates in Icelandic and Danish warmblood horses fed two different haylages and a concentrate consisting of sugar beet pulp and black oats

Four Icelandic (ICE) and four Danish Warmblood (DW) horses were used in a crossover study with two treatments to investigate the effect of breed and the effect of stage of maturity of haylage on the apparent total tract digestibility (ATTD) of a diet consisting of sugar beet pulp, black oats and haylage early or late cut. Fibre was analysed as crude fibre (CF), acid detergent fibre (ADF), neutral detergent fibre (NDF) and dietary fibre (DF = non-starch polysaccharides (NSP) plus lignin). In haylage all analysed fibre fractions increased with advancing stage of maturity, with the cell wall components cellulose, non-cellulosic residue, xylose and lignin causing this increase. Crude protein (CP) and sugars decreased with advancing stage of maturity. Feeding early cut haylage resulted in a significantly (p < 0.05) higher ATTD of dry matter (DM), organic matter (OM), energy, NDF, total NSP, DF and CP compared to feeding late cut haylage. There was a significantly (p < 0.05) higher ATTD of CF, DF and starch in ICE than in DW. Diet affected several faecal parameters with a significantly (p < 0.05) lower pH in faeces when horses were fed the early cut haylage. Concentrations of total short-chain fatty acids were significantly (p < 0.05) higher in faeces from horses fed early cut haylage, reflecting the higher fermentability (higher ATTD) of this diet. There was no marked effect of breed on faecal parameters. The DF analysis method gave the most appropriate differentiation of the fibre fractions and their digestibility, compared to the traditional CF, ADF and NDF analyses. A major advantage of the DF analysis is the capacity of recovering soluble fibres. The results suggested that ICE had higher ATTD of DF than DW, and this was caused by a tendency for a higher ATTD of cellulose, but further studies are required to verify that in general.     

Inter- and intra-plant variations in nitrogen,tannins and shoot growth of <Emphasis Type="Italic">Sclerocarya birrea</Emphasis> browsed by elephants

Impacts of elephants (Loxodonta africana africana) on woody vegetation has attracted substantial attention for decades, but plant-level responses remain a gap in the understanding of savanna ecology. Marula (Sclerocarya birrea caffra) forms an important part of elephant diets. We investigated the relationships between browsing intensity and shoot/leaf size, nitrogen (N) and condensed tannin (CT) concentrations in upper and lower canopies of male and female marula individuals in Hluhluwe-iMfolozi Park, South Africa. Browsing intensity (54%) did not differ between sexes, suggesting no preference by elephants for either sex. Females had higher [CT] than males and tannin decreased with increasing browsing intensity in both sexes. In lightly or moderately browsed trees, [CT] was controlled by unmeasured factors such that within-tree impacts of browsing were more variable in lightly/moderately browsed than heavily browsed trees. There was little change in [N] up to ~60% browsing intensity, but [N] increased dramatically at higher intensity. Shoots and leaves on broken branches in the lower canopy were larger (2.5 and 1.2 times, respectively) than those on unbroken branches in either upper or lower canopies. Chemical responses were systemic and potentially influence browsing among trees, while growth responses were strongly localised and potentially influence browsing within trees. Although marula trees are able to compensate vigorously for browsing at the scale of individual organs, trees may become progressively carbon-deficient and have their lives shortened if total plant growth is negatively affected by chronic browsing, e.g. near permanent water.     

Improving utilization of crop residues. Evaluation of two chemicals used to improve digestibility of crop residues

Two chemical treatments involving chelating metal caustic swelling (CMCS) and sodium hydroxide (NaOH) were evaluated for their ability to affect in vitro dry matter and in vitro cellulose disappearance (IVDMD and IVCD, respectively), dry matter disappearance in sacco and the chemical composition of two low-quality crop residues, cornstalks (CS) and soya bean residue (SBR). At $\text{chemical}\text{substrate}$ ratios ranging from 0.25:1 to 5:1, linear increases in IVCD of both roughages were noted. Improvements in IVCD of CS and SBR were noted at 1:1, 3:1 and 5:1$\text{chemical}\text{substrate}$ ratios, regardless of whether the treated roughages were used immediately after treatment (fresh basis) or preserved by drying or freezing. Decreased concentrations of neutral detergent fibre (NDF), acid detergent fibre (ADF), acid detergent lignin (ADL) and crude protein (CP) resulted from chemical treatment. No effects of the water component of the solvent solutions were observed. Dry matter disappearance in sacco of CMCS- and NaOH-treated roughages was increased at all $\text{chemical}\text{substrate}$ ratios tested. Treatment of either roughage with CMCS resulted in greater digestibility in sacco than did treatment with NaOH. Treatment of CS with CMCS resulted in higher rates of digestion than did treatment with NaOH. No differences in rates of digestion of SBR were noted between chemicals. Both chemicals were more effective in improving digestibility of CS than of SBR.     

The effect of white-rot basidiomycetes on chemical composition andin Vitro digestibility of wheat straw

Five white-rot basidiomycetes were evaluated for their potential to improve ruminal degradation of wheat straw.Polyorus brumalis, Lyophyllum ulmarium III,Trametes gibbosa, Pleurotus ostreatus, and aPleurotus ostreatus mutant were incubated on wheat straw for 30 d at 28°C. Detergent fiber, crude protein andin vitro dry matter digestibility (IVDMD) were determined. The results showed increasing crude protein and ash contents in fungus-treated straw. IVDMD values were increased in straws treated withP. ostreatus, P. ostreatus mutant andT. gibbosa only. Relative to untreated wheat straw the detergent fiber content—neutral detergent fiber (NDF), and acid detergent fiber (ADF) was reduced in fungus-treated straw and out of three fractions—hemicellulose, cellulose and lignin, hemicellulose showed the largest proportionate loss whereas lignin the smallest one in all 5 samples of fungus treated straw.     

Cell Wall Composition and Ruminant Digestibility of Various Maize Tissues Across Development

Maize stover, including stalks, leaves, and cobs, has potential utility as a cellulosic biofeedstock. Understanding how total stover ethanol potential is affected by the proportion and quality of major plant components would facilitate the genetic improvement of stover quality and inform decisions regarding which plant parts should be targeted for harvesting. Our objectives were to determine how the proportion and composition of plant components affected ethanol potential and whether there are early season predictors of stover quality at maturity. Twenty-three hybrids were evaluated including 20 from a factorial mating design between five silage inbred lines and four commercial inbreds and a brown-midrib3, a Leafy1, and a commercial grain hybrid checks. Plants were harvested and dissected into component parts at developmental stages vegetative 3, vegetative 12, reproductive 3, and reproductive 6 (R6). Tissues were evaluated for acid detergent fiber (ADF), neutral detergent fiber (NDF), and NDF digestibility (NDFD). Stalk was the largest fraction of whole plant dry matter (46.2%) and had the lowest NDFD (3,750 g/kg) at R6. No relationship was found between stalk ADF at early developmental stages and whole plant ADF at R6, suggesting that quality at early developmental stages is not indicative of quality at physiological maturity. Differences were observed among hybrids for ADF and NDF for most plant parts evaluated. Hybrid-by-developmental stage and hybrid-by-plant part interactions were statistically significant. This indicates that there is minimal opportunity to identify superior hybrids for biofuel production based on the proportion of total biomass represented by a plant part and its quality at early developmental stages. Maximum conversion efficiency is attained when leaves are harvested compared to other tissue types at physiological maturity.     

Erratum to: Cell Wall Composition and Ruminant Digestibility of Various Maize Tissues Across Development

Maize stover, including stalks, leaves, and cobs, has potential utility as a cellulosic biofeedstock. Understanding how total stover ethanol potential is affected by the proportion and quality of major plant components would facilitate the genetic improvement of stover quality and inform decisions regarding which plant parts should be targeted for harvesting. Our objectives were to determine how the proportion and composition of plant components affected ethanol potential and whether there are early season predictors of stover quality at maturity. Twenty-three hybrids were evaluated including 20 from a factorial mating design between five silage inbred lines and four commercial inbreds and a brown-midrib3, a Leafy1, and a commercial grain hybrid checks. Plants were harvested and dissected into component parts at developmental stages vegetative 3, vegetative 12, reproductive 3, and reproductive 6 (R6). Tissues were evaluated for acid detergent fiber (ADF), neutral detergent fiber (NDF), and NDF digestibility (NDFD). Stalk was the largest fraction of whole plant dry matter (46.2%) and had the lowest NDFD (375.0 g/kg) at R6. No relationship was found between stalk ADF at early developmental stages and whole plant ADF at R6, suggesting that quality at early developmental stages is not indicative of quality at physiological maturity. Differences were observed among hybrids for ADF and NDF for most plant parts evaluated. Hybrid-by-developmental stage and hybrid-by-plant part interactions were statistically significant. This indicates that there is minimal opportunity to identify superior hybrids for biofuel production based on the proportion of total biomass represented by a plant part and its quality at early developmental stages. Maximum conversion efficiency is attained when leaves are harvested compared to other tissue types at physiological maturity.     

Linking deer browsing and terpene production among genetic identities in Chamaecyparis nootkatensis and Thuja plicata (Cupressaceae)

To investigate whether differential herbivore browsing reflects genetic variation in plant defense expression, variation in needle terpenes and damage caused by black-tailed deer (Odocoileus hemionus) was analyzed on yellow-cedar (Chamaecyparis nootkatensis) and western redcedar (Thuja plicata). In a 100-genet yellow-cedar population, three genets that were heavily browsed and had extremely low levels of monoterpenes (0-0.36% dry matter), sesquiterpenes, and diterpenes were compared to unbrowsed genets (0.85-3.83% monoterpenes in dry matter). These differences were maintained in individuals protected from browsing, suggesting genetically based variation in constitutive terpene production. In western redcedar, heavily browsed trees had significantly lower total monoterpene concentrations (1.69% dry matter) than lightly browsed trees (3.32% dry matter). One heavily browsed tree expressed no monoterpenes. No differences were found for diterpenes. In both species, the genotypes with extremely low monoterpene concentrations came from the same open-pollinated families.     

Digestibility of a high-fiber biscuit-based diet by black and white colobus (Colobus guereza)

The acceptability and digestibility of a high-fiber biscuit-based diet was investigated using two adult male Colobus guereza animals. Although the animals were initially reluctant to accept the biscuit, it was eventually readily consumed. Apparent digestion coefficients for the diet (average composition, dry matter basis: 16% crude protein, 25% neutral detergent fiber (NDF), 9.5% acid detergent fiber (ADF), 1.2% acid lignin) determined by total fecal collection were 0.871 for dry matter, 0.813 for NDF, 0.693 for ADF, and 0.208 for acid lignin. Fiber digestive capabilities in C. guereza generally exceeded those reported in ruminant species based on predictive equations. Use of acid lignin and Cr₂O₃ as markers underestimated dry matter digestibility by 3.9 and 6.0%, respectively.     

Impact of barley form on equine total tract fibre digestibility and colonic microbiota

This study aimed at assessing the impact of four barley forms on total tract apparent digestibility of dietary fibre in horses fed a large amount of starch in the morning meal (0.27% BW). Processed barley forms had a greater pre-caecal starch digestibility than the whole form. Based on this result, we hypothesised that using barley-processing methods would limit the potential dumping of undegraded starch in the hindgut of horses and, consequently, the potential negative effect on fibre degradation in the hindgut. In a 4×4 latin square design, four mature geldings fitted with a right ventral colon-fistula were fed a meadow hay : concentrate (62 : 38; dry matter (DM) basis) diet at 1.7% BW. The concentrate was made of 80% barley distributed either as whole grain or as processed forms: 2.5 mm ground, pelleted or steam-flaked. For each period, total tract apparent digestibilities of DM, NDF and ADF were determined over 3 consecutive days by total faecal collection, whereas pH, volatile fatty acids (VFA) concentrations and cultural functional bacteria counts (total anaerobic, cellulolytic bacteria, lactic acid producers, amylolytic bacteria and lactic acid utilisers) in colonic content were evaluated on 1 day 4 h after the morning meal. Total tract apparent digestibility of DM and dietary fibre was influenced (P<0.05) by barley form. Diets including thermo-mechanically treated barley forms led to a higher (P<0.05) total tract apparent digestibility of NDF than those constituted of ground barley and also led to a greater (P<0.05) total tract apparent digestibility of ADF than those made of whole or ground barley forms. However, no significant difference was observed in colonic pH, VFA concentrations and cultural bacteria concentrations. Owing to a high starch supply in the morning meal, the concentration of the functional bacteria in the colonic content averaged 7.8 log CFU/ml, 5.9 NPM/ml, 6.9 and 7.3 CFU/ml for total anaerobic, cellulolytic, amylolytic and lactic acid-utilising bacteria, respectively. Consequently, providing horses with pelleted or steam-flaked instead of ground barley forms may limit the negative impact of starch on fibre digestibility in horses fed a high level of starch in the morning meal (0.27% BW). Moreover, the fibre-to-starch ratio fed in this experiment did not cause any digestive upset.     

Effects of Forage Quality and Cell Wall Constituents of Bermuda Grass on Biochemical Conversion to Ethanol

Bermuda grass is an attractive candidate as a feedstock for biofuel production because over four million hectares of Bermuda grass are already grown for forage in the Southern USA. Because both rumen digestion and biochemical conversion to ethanol depend upon enzymatic conversion of the cell wall polysaccharides into fermentable sugars, it is probable that grasses bred for increased forage quality would be more amenable for ethanol production. However, it is not known how variation in rumen digestibility and cell wall/fiber components correlates with efficiency of conversion to ethanol via fermentation. The objective of this research was to determine relationships between ethanol production evaluated by simultaneous saccharification and fermentation (SSF), 72-h in vitro ruminal dry matter digestibility (IVDMD), in vitro ruminal gas production after 24 and 96 h, and biomass composition for 50 genetically diverse Bermuda grass accessions. The Bermuda grass samples were subjected to standard 72-h IVDMD and forage fiber analyses. Also, in separate labs, gas production was measured in sealed volume-calibrated vials after 24 (NNG24) and 96 h (NNG96) of in vitro fermentation by ruminal fluid; ethanol and pentose sugar productions were measured from a bench-top SSF procedure; cell wall constituents were determined by the Uppsala Dietary Fiber Method; and total nitrogen, carbon, and ash concentrations were determined by using the LECO combustion method. Ethanol production was moderately correlated with IVDMD (r?=?0.55) and NNG96 (r?=?0.63) but highly correlated with NNG24 (r?=?0.93). Ethanol was negatively correlated with neutral detergent fiber (NDF; r?=??0.53) and pentose sugars (r?=??0.60), but not correlated with glucose content. Regression models indicated that NDF and cell wall pentose sugar concentrations had significant negative effects on ethanol production. Variation among entries for IVDMD was affected by variability of NDF, pentose sugar concentrations, and biomass nitrogen content. Variation in Klason lignin content had only minor negative impacts on ethanol production and IVDMD. Biochemical conversion efficiency of Bermuda grass by SSF can be best estimated by NNG24 but not by IVDMD.     

Secondary metabolites and nutrients of woody plants in relation to browsing intensity in African savannas

Carbon-based secondary metabolites (CBSMs) are assumed to function as defences that contribute to herbivore-avoidance strategies of woody plants. Severe browsing has been reported to reduce concentrations of CBSMs and increase N concentrations in individual plants, causing heavily browsed plants to be characterised by N-rich/C-poor tissues. We hypothesised that concentrations of condensed tannins (CT) and total polyphenols (TP) should decrease, or N increase, in relation to increasing intensity of browsing, rendering severely browsed plants potentially more palatable (increased N:CT) and less N-limited (increased N:P) than lightly browsed ones. We sampled naturally browsed trees (taller than 2 m) of four abundant species in southern Kruger National Park, South Africa. Species-specific relationships between N:CT, CT, TP and P concentrations and increasing browsing intensity were detected, but N and N:P were consistently invariable. We developed a conceptual post-hoc model to explain diverse species-specific CBSM responses on the basis of relative allocation of C to total C-based defence traits (e.g. spines/thorns, tough/evergreen leaves, phenolic compounds). The model suggests that species with low allocation of C to C-based defence traits become C-limited (potentially more palatable) at higher browsing intensity than species with high allocation of C to C-based defences. The model also suggests that when N availability is high, plants become C-limited at higher browsing intensity than when N availability is low.     

How Herbivore Browsing Strategy Affects Whole-Plant Photosynthetic Capacity

If a browse damage index indicates that a tree has been 50% browsed by herbivores, does this mean half the leaves are entirely eaten or are all the leaves half eaten? Were the affected leaves old or young? Large or small? In sunshine or shade? Understanding what effect browsing will have on the photosynthetic capacity and the plant’s survival ability clearly requires a greater understanding of browsing strategy across the canopy than can be given by a single index value. We developed stochastic models of leaf production, growth and consumption using data from kamahi (Weinmannia racemosa) trees in New Zealand which have been browsed by possums (Trichosurus vulpecula), to ascertain which of six feasible browsing strategies possums are most likely to be employing. We compared the area distribution of real fallen leaves to model output in order to select the best model, and used the model to predict the age distribution of leaves on the tree and thus infer its photosynthetic capability. The most likely browsing strategy that possums employ on kamahi trees is a preference for virgin (i.e. previously unbrowsed) leaves, consistent with the idea that browsing increases the production of chemical plant defences. More generally, our results show that herbivore browsing strategy can significantly change the whole-plant photosynthetic capability of any plant and hence its ability to survive, and therefore, herbivore damage indices should be used in conjunction with more detailed information about herbivore browsing strategy.     

Effects of groundnut stover or Bermudagrass hay supplementation to doe kids on winter hardwood range

Goats in north-central Texas raised on rangeland often face winter forage quantity and quality deficits that may be mitigated by feeding hay or stover. Groundnut (Arachis hypogea) stover (8% CP, 35% ADF, 43% NDF and 8% acid detergent lignin (ADL) DM basis) and bermudagrass (Cynodon dactylon) hay (12% CP, 33% ADF, 73% NDF, and 5% ADL DM basis) were tested at Stephenville, Texas as 0.0, 0.5, or 2.0% BW supplement/substitution diets on 18 kg Boer X Spanish doe kids browsing native hardwoods (8 ha⁻¹). Both hay and stover were fed ad libitum in a traditional feedlot, using a complete formulated feed ration as a control. Trials ran for 10 weeks from January to March in 2003 (134 mm rainfall) and in 2004 (182 mm rainfall). Goats receiving 0.5% and 2% BW bermudagrass or 2% BW groundnut stover had greater ADG than those in the control and 0.5% BW groundnut paddocks (P < 0.05). Goats fed complete ration in the drylot had greater (P < 0.05) ADG than those eating either hay or stover ad libitum. Bermudagrass hay rejected by goats in the hardwood trial was 20% lower in CP, 7% greater in NDF, 8% greater in ADF, and 9% greater in ADL than the original fed hay; groundnut stover refusals were 21% lower in CP, 12% greater in NDF, 19% greater in ADF, and 20% greater in ADL concentration than the stover when fed. Supplementing goats on hardwood range with bermudagrass hay or groundnut stover may improve ADG when browse is scarce or of poor quality.     

Saturated fat supplemented in the form of triglycerides decreased digestibility and reduced performance of dairy cows as compared to calcium salt of fatty acids

The two most popular rumen-protected fatty acid supplements in dairy cow rations are calcium salts of palm oil fatty acid calcium salts of palm oil fatty acid (CSFA) and prilled saturated fatty acids (SFAs). The objectives of this study were to determine the effects of supplementing SFA in the form of triglycerides (TSFA), as compared to CSFA, on yields, efficiency and diet digestibility in high-yielding dairy cows. Twenty-eight (14 cows in each group) multiparous cows were fed a basal diet supplemented (on DM basis) with either 12 g/kg TSFA (~350 g/cow per day – contained 980 g/kg fat; 882.3 g/kg SFAs) or 14 g/kg CSFA (~440 g/cow per day – contained 800 g/kg fat; 566.4 g/kg SFAs). The supplement amounts in the diet were balanced according to fat content. Rumen samples were taken for measurements of ammonia and volatile fatty acids concentrations, and fecal samples were taken for digestibility measurements. The CSFA cows produced 3% higher milk yields (47.6 v. 46.2 kg/day; P < 0.0001) and 4.7% higher 4% fat-corrected milk (FCM; 44.7 v. 42.7 kg/day; P = 0.02) than the TSFA cows. No difference in milk-fat content was observed, but milk-protein content was higher in the TSFA than CSFA cows. Yields of fat and protein were similar, but lactose yields were higher in TSFA cows. There were no differences in dry matter intake or efficiency calculations between groups. The ruminal ammonia concentrations were similar between groups, whereas acetate concentrations and acetate : propionate ratio were greater for CSFA than TSFA cows. The apparent total-tract digestibility of dry (P < 0.0007) and organic matters (P < 0.0003), fat (P < 0.0001), NDF and ADF (P = 0.02) were lower in the TSFA v. CSFA cows. In conclusion, the CSFA-supplemented cows produced 3% higher milk and 4.7% higher 4% FCM than the TSFA cows. However, TSFA supplementation did not depress milk-protein content. The apparent total-tract digestibility was lower for all dietary components in the TSFA cows, which was probably due to the effects of both degree of saturation and triglyceride form of the TSFA supplement. Considering that diets were balanced according to the fat content of the supplements, the lower yields of milk and FCM observed in the TSFA than CSFA cows were likely due to the lower digestibility of the fat and other nutrients in the TSFA cows, which might have negatively influenced the dietary energy content.