Restricted Grazing Research Articles

Morphometry and carcass characteristics of goats submitted to grazing in the Caatinga

The objective of this study was to evaluate morphometric measures, carcass yields, absolute weights and yields of commercial cuts of carcass of kids with no defined breed. Eighteen castrated male goats, with average weight of 15 kg were used. The experimental period lasted 105 days. The experimental design was completely randomized; animals were allocated to three treatments: free grazing without supplementation; restricted grazing without supplementation and free grazing with supplementation. Animals were supplemented (1% of body weight) with forage cactus (Opuntia ficus - indica, Mill) and soybean meal (Glycine max). The feeding consisted of continuous grazing on caatinga. Supplemented animals had higher live slaughter weight and body score, and consequently higher morphometric measures in vivo and in carcasses. The supplementation provided carcasses with higher body weight and body score. For yields of carcass, there was no difference between treatments restricted grazing and grazing with supplementation; supplementation provided carcasses with higher yields. Supplemented animals had higher absolute weights for commercial cuts. Supplementation of grazing goats raised in the caatinga provides animals with higher body weight at slaughter, greater morphometric measures in vivo and in carcass and better body conformation. Therefore, for supplementation, the level used in this experiment is a good alternative in the creation of small ruminants during the dry period in the semi-arid region.

Effect of continuous v. daytime grazing on feed intake and growth of sheep grazing in a semi-arid grassland steppe

In the Inner Mongolian steppe, China, sheep generally graze during daytime and are kept in yards overnight. Hence, nutrients are not returned to the grassland, which might reduce its long-term productivity. Furthermore, the restricted grazing time may limit forage intake and thus the performance of sheep. The aim of this study was therefore to evaluate the impact of continuous 24-h grazing (CG) v. the common daytime grazing (DG) on herbage mass (HM), feed quality, feed organic matter intake (OMI) and live weight gain (LWG) of sheep in the Inner Mongolian steppe. Experiments were carried out from July to September, between 2005 and 2007 on two 2-ha plots per grazing treatment. Each month, the external faecal marker titanium dioxide (TiO2) was orally administered to six sheep per plot on 10 consecutive days. Faecal grab samples were obtained from day 6 to 10 and analysed for CP concentrations to estimate digestibility of organic matter (dOM). Faecal TiO2 concentrations were used to determine the total faecal output and hence OMI of sheep. Concomitant to faeces collection, HM and quality, as well as LWG of the animals were measured. HM and herbage quality did not differ between treatments. However, as the season progressed, concentrations of NDF, ADF and ADL increased, whereas HM and CP concentrations declined. HM and herbage quality parameters differed between years according to the annual precipitation. dOM was similar in CG (0.577) and DG (0.572) sheep, but it decreased from July (0.583) to September (0.558) and differed between years. Accordingly, the OMI of sheep was similar for both treatments across the entire grazing season and all study years. Although mean LWG differed between months and years, it was identical in CG (101.5 g/day) and DG sheep (101.8 g/day). Additional time on pasture during night does not increase feed intake or animal performance. Positive effects of a nutrient reflux on grassland productivity and herbage quality when animals remained on the plots overnight were not found, most likely because of the fact that sheep crowded together in one corner of the plots during darkness and faecal and urinary excretions were thus not evenly distributed across the entire pasture. Considering the risk of animal theft as well as the importance of sheep manure as fuel, the common penning of sheep at night seems to be an adequate management practice for pastoralists in the Inner Mongolian steppe.

Avaliação de controle leiteiro de bovinos usando análises de medidas repetidas

The objective of this study was to analyze the milk yield data at 14-day intervals of seven Holstein cows submitted to three treatments with alfalfa [T1: control (confinement in a rest area with corn silage +11.0 kg concentrate); T2: restricted grazing of alfalfa + corn silage+11.0 kg concentrate; T 3 : grazing of alfalfa ad libitum + corn silage + 8.0 kg concentrate] in randomized experiment. Data were analyzed as repeated measures through MIXED procedure, where each cow was a subject. In order to model the error variance-covariance structure of the evaluations within the subjects, the Huynh-Feldt matrix was selected, meeting the sphericity condition, indicating that for analysis of the milk yield data in this experiment, besides the mixed linear model using maximum likelihood resources, the ordinary least squares model can also be used, considering (co)variances in uniform time. Through the use of repeated measures analysis, it was possible to verify significant reduction (p ≤ 0.01) in the milk yield in the three treatments; however, there was no global significant difference (p > 0.05) between treatments or in treatments within each control (p > 0.05).

Fire and grazing influence food resources of an endangered rock-wallaby

Context Fire and grazing have complex and interacting impacts on food resources available to endangered herbivores and can potentially be manipulated as part of conservation strategies. Aims We examined the interacting impacts of fire and grazing on the food resources available to a colony of endangered brush-tailed rock-wallabies (Petrogale penicillata) to test fire as a potential management tool. Methods We conducted two manipulative experiments using a repeated-measures split-block design. We measured the effects of grazing and strategic burning on total vegetation biomass and on particular plants selected by rock-wallabies. In the first experiment we measured the impact of rock-wallaby grazing alone. In the second experiment we measured grazing impacts by both rock-wallabies and potentially competitive sympatric macropods. Grazing was manipulated with three treatments: grazed (open), ungrazed (fenced) and procedural control (half fence). Key results In both experiments, burning resulted in greater above-ground biomass of plants selected by rock-wallabies. The response of different plant functional groups to fire was staggered, with forb biomass peaking early and browse biomass increasing above unburnt levels a year after burning. Conclusions Despite the limited grazing pressure exerted by the small colony of rock-wallabies in Experiment 1 we detected a negative grazing effect on forbs growing after fire in burnt plots. In Experiment 2, grazing pressure was much more marked due to the high densities of sympatric macropods. In this case, while burning resulted in greater biomass of plants selected by rock-wallabies, grazing (predominantly by sympatric macropods) negated this effect. Implications Small patchwork burning can be a useful tool to improve food resources for brush-tailed rock-wallabies, with effects sustained over more than two years. However, when rock-wallabies are sympatric with possible competitor species, the grazing impacts of sympatric macropods may cancel out any benefits to rock-wallabies.

Disease, population viability, and recovery of endangered Sierra Nevada bighorn sheep

AbstractSierra Nevada bighorn sheep (Ovis canadensis sierrae) experienced a severe population decline after European settlement from which they have never recovered; this subspecies was listed as endangered under the United States Endangered Species Act (ESA) in 1999. Recovery of a listed species is accomplished via federally mandated recovery plans with specific population goals. Our main objective was to evaluate the potential impact of disease on the probability of meeting specific population size and persistence goals, as outlined in the Sierra Nevada bighorn sheep recovery plan. We also sought to heuristically evaluate the efficacy of management strategies aimed at reducing disease risk to or impact on modeled bighorn populations. To do this, we constructed a stochastic population projection model incorporating disease dynamics for 3 populations (Langley, Mono, Wheeler) based on data collected from 1980 to 2007. We modeled the dynamics of female bighorns in 4 age classes (lamb, yearling, adult, senescent) under 2 disease scenarios: 5% lower survival across the latter 3 age classes and persistent 65% lower lamb survival (i.e., mild) or 65% reduced survival across all age classes followed by persistent 65% lower lamb survival (i.e., severe). We simulated management strategies designed to mitigate disease risk: reducing the probability of a disease outbreak (to represent a strategy like domestic sheep grazing management) and reducing mortality rate (to represent a strategy that improved survival in the face of introduced disease). Results from our projection model indicated that management strategies need to be population specific. The population with the highest growth rate (${\hat {\lambda }}$; Langley; ${\hat {\lambda }}$ = 1.13) was more robust to the effects of disease. By contrast, the population with the lowest growth rate (Mono; ${\hat {\lambda }}$ = 1.00) would require management intervention beyond disease management alone, and the population with a moderate growth rate (Wheeler; ${\hat {\lambda }}$ = 1.07) would require management sufficient to prevent severe disease outbreaks. Because severe outbreaks increased adult mortality, disease can directly reduce the probability of meeting recovery plan goals. Although mild disease outbreaks had minimal direct effects on the populations, they reduced recruitment and the number of individuals available for translocation to other populations, which can indirectly reduce the probability of meeting overall, range‐wide minimum population size goals. Based on simulation results, we recommend reducing the probability of outbreak by continuing efforts to manage high‐risk (i.e., spatially close) allotments through restricted grazing regimes and stray management to ensure recovery for Wheeler and Mono. Managing bighorn and domestic sheep for geographic separation until Sierra Nevada bighorn sheep achieve recovery objectives would enhance the likelihood of population recovery. © 2011 The Wildlife Society.

Practical feeding and condition scoring for donkeys and mules

SummaryDonkeys have evolved to thrive on highly fibrous, poor quality foodstuffs and have evolved as browsers as well as grazers. As such, they have different nutrient requirements with significantly lower energy and protein needs when compared with horses. Dietary management of donkeys is essential when kept in a temperate climate as they are prone to obesity and related disorders. A diet based on fibrous forages and limited grazing is usually sufficient for the majority of donkeys and mules. Specialist feeding is discussed in this article.

Morphological, chemical and mineralogical characterization of developing soils and their management in the western Siwalik Himalayas

The western Siwalik Himalayas of India experienced the last climate shift 3500 years ago and the soils have been marked by rigorous human activities for a few centuries. An attempt was made to investigate the interactions between soil-forming factors and processes in soil development in relation to land forms and climate change. The hallmark of the soils is the considerable heterogeneity in solum and regolith thickness, horizon boundaries, structural development in surface soils, pH, electrical conductivity and soil mineralogy, irrespective of landscape form and position. A remarkable feature of the soils is the development of deep argillic horizons, or B horizons, in certain landscape positions. The minerals identified were quartz, micas and feldspars in the sand and silt fractions. Illite, kaolinite, vermiculite, smectite and chlorite were present in the clay fractions. Soils under forest vegetation and those recently brought under cultivation belong to Typic Hapludalfs. Soils cultivated over centuries, however, failed to qualify as Alfisols and were classified as Typic/Dystric Eutrudepts. The eroded barren soils were similarly classified as Typic Udorthents. All the soils were low to medium in available nitrogen and phosphorus. The use of nitrogen and phosphorus fertilizer is therefore needed to ameliorate nutrient deficiency and boost crop production. Because of the presence of appreciable amounts of potassium-bearing minerals, soils are likely to be non-responsive to potassium application. The soils of the Dala series (Typic Hapludalfs) are located on moderate hill slopes and thus soil erosion is less severe than for the Mansu series (Typic Udorthent). In the Chamror and Dhar series (Typic/Dystric Eutrudepts) soil erosion is not a serious problem because of terracing and the finer texture of the soils. Crops can thus be grown on profile-stored moisture during dry periods and limited grazing may be permitted.

Elevated sensitivity: riparian vegetation in upper mountain zones is especially vulnerable to livestock grazing

AbstractQuestion: Riparian zones provide ecologically rich interfaces between land and flowing water, and are favoured areas for grazing by native ungulates and livestock. Overgrazing can degrade riparian vegetation. Will sensitivity and vulnerability to grazing increase in upper mountain zones because of the harsh physical environment?Location: We compared the impact of cattle grazing along natural elevational corridors provided by two first‐order creeks in the Rocky Mountains of Alberta, Canada.Methods: Substrate and vegetation characteristics were assessed in quadrats within transects positioned in ungrazed or lightly grazed, versus moderately to heavily grazed sites extending from the alpine down through the subalpine, montane, parkland and prairie zones.Results: Analyses revealed that 18 of 19 substrate and vegetation characteristics varied along the elevational profile (17 P<0.05; 1 P<0.1). Fifteen differed with grazing (12 P<0.05; 3 P<0.1), which was associated with coarser substrate with lower pH, reduced diversity and density of shrubs and trees, reduced vegetation cover, increased percent cover and species of weeds and changes in proportions of particular plants such as increasing yarrow (Achillea millefolium) and decreasing mountain valerian (Valeriana sitchensis). Significant grazing × elevation interactions for seven characteristics (5 P<0.05; 2 P<0.1) indicated greater impacts at higher elevations.Conclusions: This study revealed that the upper elevations were heavily affected, despite their shorter, seasonally restricted grazing history. This indicates that riparian zones in upper mountain environments are particularly vulnerable to livestock grazing.

Silage-concentrate finishing of bulls versus silage or fresh forage finishing of steers: Effects on fatty acids and meat tenderness

The objective of this trial was to assess meat quality in terms of tenderness and fatty acid (FA) composition in M. longissimus dorsi and M. gluteus medius from bulls finished on ad lib silage-concentrates (SIL:CON) vs. steers fed ad lib silage (FF) or restricted silage and unrestricted grazing (RES-F). Warner-Brazler shear force value day 1 was lowest for the FF steers (p<0.05). Myofibril fragmentation index (MFI) values were similar after seven days of ageing, showing that ageing compensated for differences in meat tenderness associated with feeding programmes. Total monounsaturated FAs and 18:1c-9 levels were higher in the steer tissue (p<0.001). The SIL:CON bulls had higher polyunsaturated n-6 fatty acids and 18:2n-6 level (p<0.001). Polar lipid 18:2n-6 and n-6 levels were higher for FF than for RES-F steers, whereas the 18:3n-3 level was higher for RES-F than for FF steers (p<0.001). The n-6/n-3 ratio was lowest for the FF steers and highest for the SIL:CON bulls (p<0.001).

Effect of Restricted Grazing on Dry Matter Intake Rate

Effect of Restricted Grazing on Dry Matter Intake Rate

Desempenho de vacas leiteiras em pastagem de alfafa suplementada com silagem de milho e concentrado e viabilidade econômica do sistema

Avaliou-se o efeito da substituição parcial de silagem de milho por pastagem de alfafa no desempenho de vacas leiteiras e na viabilidade econômica do sistema. Utilizaram-se 24 vacas da raça Holandesa, em estádio médio de lactação, em delineamento em blocos ao acaso. Os tratamentos foram: dieta à base de silagem de milho em confinamento, silagem de milho substituída parcialmente por pastejo restrito (PR) e pastejo irrestrito (PI) de alfafa. O sistema de pastejo foi rotacionado, e a quantidade de concentrado igual em todos os tratamentos. A massa de forragem foi de 2.338 e de 1.878kg de MS/ha, e a oferta de 1,8 e 4,2kg de MS/100kg de peso vivo, nos tratamentos PR e PI, respectivamente. A produção de leite não diferiu entre os tratamentos, cujas médias foram de 25,9; 25,8 e 25,2 litros por vaca por dia no confinamento, no PR e no PI, respectivamente. A produção diária de leite por área foi de 59,3L/ha no PR e de 63,0L/ha no PI, enquanto no confinamento foi de 45,7L/ha. A substituição parcial de silagem de milho por alfafa em pastejo não limitou o desempenho produtivo dos animais e mostrou-se economicamente vantajosa em relação ao confinamento.

Nitrous Oxide Emission from Grazed Grassland Under Different Management Systems

Nitrous oxide (N2O) emissions from grazed grasslands are estimated to be approximately 28% of global anthropogenic N2O emissions. Estimating the N2O flux from grassland soils is difficult because of its episodic nature. This study aimed to quantify the N2O emissions, the annual N2O flux and the emission factor (EF), and also to investigate the influence of environmental and soil variables controlling N2O emissions from grazed grassland. Nitrous oxide emissions were measured using static chambers at eight different grasslands in the South of Ireland from September 2007 to August 2009. The instantaneous N2O flux values ranged from -186 to 885.6 μg N2O-N m−2 h−1 and the annual sum ranged from 2 ± 3.51 to 12.55 ± 2.83 kg N2O-N ha−1 y−1 for managed sites. The emission factor ranged from 1.3 to 3.4%. The overall EF of 1.81% is about 69% higher than the Intergovernmental Panel on Climate Change (IPCC) default EF value of 1.25% which is currently used by the Irish Environmental Protection Agency (EPA) to estimate N2O emission in Ireland. At an N applied of approximately 300 kg ha−1 y−1, the N2O emissions are approximately 5.0 kg N2O-N ha−1 y−1, whereas the N2O emissions double to approximately 10 kg N ha−1 for an N applied of 400 kg N ha−1 y−1. The sites with higher fluxes were associated with intensive N-input and frequent cattle grazing. The N2O flux at 17°C was five times greater than that at 5°C. Similarly, the N2O emissions increased with increasing water filled pore space (WFPS) with maximum N2O emissions occurring at 60–80% WFPS. We conclude that N application below 300 kg ha−1 y−1 and restricted grazing on seasonally wet soils will reduce N2O emissions.

Desempenho de novilhos mantidos em pastagens de capim-elefante e capim-mombaça

Foi avaliado o desempenho de novilhos mantidos em pastagens de capins elefante e mombaça no período de outubro a dezembro de 2006. Adotou-se o sistema de pastejo rotacionado, com oferta regulada de forragem. A área experimental consistia de duas repetições contendo 18 piquetes de 0,25 ha cada, divididos em nove piquetes formados de capim-elefante e nove com mombaça. Os efeitos de tratamentos foram as espécies forrageiras, a repetição de área, a interação entre estes, piquetes dentro da interação e o erro experimental. Este modelo foi usado para analisar os atributos do pasto. Para analisar o consumo, a digestibilidade e o ganho, foram aleatoriamente alocados 24 novilhos para as respectivas interações entre forragem vs. repetição vs. sistema de pastejo, o que totalizou três animais por interação tripla. Os sistemas de pastejo consistiram de pastejo ad libitum (AL) e restrito (PR). O capim-elefante apresentou maior biomassa de matéria seca total (BT) e biomassa de matéria seca verde foliar (BFV). Não houve diferença entre as forrageiras quanto à produção de biomassa de matéria seca verde foliar, no entanto a proporção de folhas foi maior no capim-mombaça. As extrusas apresentaram composição bromatológica semelhante. Apenas o consumo de proteína bruta diferiu entre as forrageiras, sendo este maior para o pasto de mombaça. A alimentação à vontade possibilitou maior consumo de todos os nutrientes em ambas as pastagens. A digestibilidade dos nutrientes foi maior para o capim-elefante, mas não diferiu entre os níveis de alimentação: apenas o teor em proteína bruta foi maior no pasto onde o pastejo foi restrito e o teor de energia bruta do pasto foi maior para o sistema de pastejo à vontade. Apesar das diferenças qualitativas e quantitativas entre as forrageiras, não foram encontradas diferenças quanto ao ganho em peso por animal e por área. Entre os animais com alimentação à vontade, o ganho médio em massa corporal foi de 850 g/dia e o ganho por área de 246 kg/ha durante o período experimental.

Milk urea concentration as an indicator of ammonia emission from dairy cow barn under restricted grazing

Bulk milk urea concentration was evaluated to assess its potential as an indicator of ammonia emission from a dairy cow barn in a situation with restricted grazing. An experiment was carried out with a herd of, on average, 52 Holstein-Friesian dairy cows. The cows were housed in a naturally ventilated barn with cubicles and a slatted floor, were fed ensiled forages and feed supplements, and each day were allowed 8.5h of grazing. The experiment was a balanced randomized block design, replicated 3 times. The experimental factor was the bulk milk urea level, which was adjusted to levels of 15, 35, and 55mg of urea per 100g of milk, respectively, by changing the level of nitrogen fertilization of the pasture, the herbage mass and grass regrowth age, and the level and type of feed supplement. Ammonia emission from the barn was measured using sulfur hexafluoride as the tracer gas. Ammonia emission generally increased upon an increase in adjusted milk urea levels. A dynamic regression model was used to predict ammonia emission from bulk milk urea concentration, temperature, and a slurry mixing index. This model accounted for 66% of the total variance in ammonia emission and showed that emission increases exponentially with increasing milk urea concentration. At levels of 20 and 30mg of urea per 100g of milk, ammonia emission increased by about 2.5 and 3.5%, respectively, when milk urea concentration increased by 1mg/100g. Furthermore, emissions from the barn increased 2.6% when temperature increased by 1°C. The study showed that bulk milk urea concentration is a useful indicator for ammonia emissions from a dairy cow barn in a situation with restricted grazing.

Do grazers prefer invasive seaweeds?

Sargassum muticum is an invasive alga that affects biodiversity of benthic communities. Its proliferation in recipient communities may be due to several factors including limited grazing effects by native herbivores (“Enemy Release Hypothesis”, ERH). Until now, there is no information about grazing preferences exerted by native herbivores over S. muticum and native seaweeds on the Galician coast. The aim of this study was to determine whether or not different grazers preferred S. muticum compared with native seaweeds. The hypothesis tested was that native meso- and macrograzers would prefer native seaweeds rather than the invasive seaweed S. muticum. Concentrations of polyphenols were also examined to see whether or not these compounds correlated with preferences for types of food. Despite variability of responses within and among herbivorous species, results suggested that grazers preferred native seaweeds over the invasive S. muticum. In most cases, the gastropods Littorina littorea and Aplysia punctata preferred to feed on Ulva sp., whereas L. obtusata fed mostly on Fucus vesiculosus. The sea urchin Paracentrotus lividus, however, showed no preference, feeding indiscriminately on different seaweeds. It is also important to highlight that in many cases, grazers did not show any preference (i.e. consumption when a choice was available could not be differentiated from consumption when there was no choice). These results, therefore, partially supported our prediction and reinforced the notion that well-designed experiments and analyses must be done before preference can be inferred. We suggest that the invader S. muticum is not under substantial pressure from grazers in the area of study.

Persistency of the effect of long-term administration of a whey protein gel composite of soybean and linseed oils on performance and milk fatty acid composition of dairy cows

To study the persistency of the effect of supplementing a whey protein emulsion gel (WPEG) of a mixture of linseed and soybean oil on milk fatty acids, a 10-wk experiment was carried out with 32 lactating Holstein Friesian dairy cows. During the first 5 wk, all cows were managed on a restricted grazing regime with pasturing during the daytime and receiving a mixed ration of maize silage, grass hay, soybean expeller and a mineral mix during night-time. During the last 5 wk, all cows were indoors throughout the day and received a mixed ration containing grass silage, maize silage, grass hay, and concentrates. Cows were randomly allotted to one of two treatments: a control treatment with no supplementation and a “Gel” treatment supplementing WPEG at a rate of approximately 1.5 kg/d per cow. Feed intake and milk production were monitored and samples of a.m. milking were analyzed for fat, protein, lactose and fatty acids. Supplementing WPEG had no significant effect on monitored dry matter intake (14 kg DM/d during restricted grazing — grass intake not determined; 21 kg DM/d during the last 5-wk period). Supplementing WPEG had no effect on milk yield (average 35 kg/d) and on concentrations and yields of milk fat and milk protein. Supplementing WPEG increased lactose concentration. Supplementing WPEG decreased the proportions in milk of medium-chain fatty acids and increased the proportions of most C18 fatty acids, except cis9 C18:1 and trans10, cis12 C18:2. Supplementing WPEG led to doubling of cis9, cis12 C18:2 (from 1.8 to 4.0 g/100 g of fatty acid) and a fourfold increase above control in cis9, cis12, cis15 C18:3 (from 0.5 to 2.2 g/100 g of fatty acids). From these results it is concluded that feeding vegetable oils as WPEG to dairy cattle has a persistent effect on the proportions of poly-unsaturated fatty acids in milk.

Exigências de proteína de bovinos anelorados em pastejo

Objetivou-se determinar as exigências proteicas de bovinos anelorados sob pastejo em cinco piquetes de Brachiaria decumbens. Utilizaram-se 27 animais não-castrados, com peso corporal (PC) médio inicial de 311,0 kg e idade média de 14 meses. Três animais foram abatidos após o período de adaptação para servirem como referência para as estimativas do peso de corpo vazio (PCVZ) e da composição corporal iniciais dos animais mantidos no experimento. Dos 24 animais restantes, quatro foram designados ao grupo mantença, que teve tempo de pastejo restrito. Os 20 demais foram distribuídos em quatro tratamentos: mistura mineral, autocontrole e duas frequências de alimentação: três vezes/semana (às segunda, quartas e sextas-feiras) ou diariamente. As exigências líquidas de proteína para ganho diminuíram com o aumento do peso vivo (PV) dos animais. A exigência líquida de proteína encontrada para um animal com peso corporal de 250 kg foi de 153,71 g/kg GPCVZ, enquanto para um animal de 400 kg foi de 141,86 g/kg GPCVZ. A seguinte equação foi obtida para estimativa da proteína retida em relação ao ganho de peso vivo em jejum (GPVJ) e da energia retida (ER): PR (g/dia) = -34,6109 + 257,956*GPVJ – 17,01*ER. As exigências de proteína metabolizável estimadas para mantença e ganho de peso foram de 357,77 e 288,33 g/kg PC, respectivamente, para um bovino não-castrado de 400 kg de PC sob pastejo. Animais que consomem suplementos proteicos apresentam maiores exigências de proteína degradável no rúmen (PDR) em comparação a animais sem suplementação, em virtude do maior consumo de nutrientes digestíveis totais. Para um animal de 400 kg de PV sob suplementação, as exigências de proteína degradável no rúmen e proteína não-degradável no rúmen são de 764,22 e 73,89, respectivamente, que correspondem à exigência de proteína bruta de 838,10 g/dia.

An assessment of coral reefs in Tobago

Abstract. The coral reefs of Tobago represent some of the southernmost reefs in the Caribbean and have developed under the influence of runoff (e.g. terrestrial sediment and nutrients) from South American rivers. Local terrestrial runoff resulting from poor land management practices have also impacted reef development. Benthic surveys were conducted at 11 sites around the island in order to assess reef status. Mean (±SD) coral cover across Tobago was 14.9 (±7.6) % and macroalgae cover was highly variable ranging between 65 % at Bulldog Reef (Atlantic Coast), to 1.2 % at Mt Irvine (Caribbean coast). Montastrea faveolata (Ellis) and Diploria strigosa (Dana) dominated scleractinian coral communities and gorgonians accounted for 12.3 (±7.1) % of total benthic cover. Yellow band disease was observed on the major reef builders, M. faveolata, at most sites. The grazing urchin, Diadema antillarum (Philippi), have not recovered since their demise in the 1980's. However despite limited grazing, the majority of moni...

Forest structure influences on rainfall partitioning and cloud interception: A comparison of native forest sites in Kona, Hawai’i

Vegetation can play a major role in the hydrologic ecosystem service tradeoffs resulting from land use change: by affecting the volume of rain water that reaches the ground surface, vegetation affects water supply. But because canopy interception of rainfall is affected in complex and competing ways by forest structure and ambient weather conditions, both of which vary at small and large scales, predicting the impacts of vegetation change is challenging. We explore rainfall and cloud interception in two native forests sites on leeward Hawai’i Island and find that although our study forests are superficially similar, with identical dominant species and no history of logging, throughfall in one forest is nearly double that in the other. Using micrometeorological and vegetation data collected over 20 months, we examine the dominance of different hydrologic processes at each site. Direct fog water input accounted for at least 12% of total water input in the North forest site, an average of about 0.1 mm/day, and 27% of total water input in the South forest, an average of 0.3 mm/day. In the North forest, canopy interception of rainfall dominates, and annual throughfall amounts to only 64% of rainfall. A large canopy surface area and low rainfall rates cause the high rate of interception. Direct interception of clouds by the canopy dominates in the South forest, where throughfall is 113% of rainfall. Increased throughfall at this site is not attributable to increased fogginess. Instead, taller trees and a denser mid-canopy increase canopy surface area, causing increased cloud interception. The denser forest structure is likely a result of cattle exclusion and limited grazing in this forest. This study illustrates the effects of subtle differences in vegetation structure on hydrologic fluxes and, by extension, the hydrologic effects of land use change. It also underscores the importance of replicate sites in ecohydrologic investigations.

Grazing strategies to protect soil physical properties and maximise pasture yield on a Southland dairy farm

intensive dairy cattle grazing on wet soil can have a detrimental effect on soil physical quality and consequently on pasture production. Soil physical properties (porosity, bulk density, saturated hydraulic conductivity) of a Pallic soil (Pukemutu silt loam) and pasture production were assessed on a dairy farm in Southland, New Zealand, under a number of different cattle grazing strategies: (i) normal grazing management on undrained land, (ii) normal grazing practice on drained land, (iii) restricted autumn grazing, (iv) restricted grazing when soil conditions were wet, (v) never pugged, and (vi) never grazed. a hand‐pushed cone penetrometer determined treatments (iv) and (v). Soil macroporos‐ity was significantly greater (P < 0.05) on the never grazed plot than all other treatments at post‐spring sampling each year. There were no significant differences in any soil physical properties measured on cattle grazed treatments. Spring pasture yield from the never grazed treatment was greater (P < 0.05) than the drained and undrained standard practice grazing treatments for one of the three seasons. The lack of treatment differences in soil physical properties and pasture yield from grazing treatments suggests that the never pugged grazing strategy failed to prevent soil compaction by dairy cows. To some extent this is expected as soil compaction occurs at soil water contents lower than the thresholds for pugging damage. However, the large number of grazing events when soil conditions were considered safe according to the never pugged treatment protocol, but when soil water content was greater than the plastic limit, probably contributed to both soil treading damage and compaction during the traditionally wet early spring period.