Levels Of Forage Allowance Research Articles

Metabolic and hormonal profiles and productive performance in primiparous and multiparous cows grazing different forage allowance in late gestation

The aim of this study was to evaluate two levels of forage allowance (FA) during the prepartum period on metabolic, hormonal, productive, and reproductive variables in primiparous (P) and multiparous (M) beef cows. Six weeks before calving, 40 P and 42 M cows were assigned to two FA (native pastures) treatments until calving (day 0): High (15 kg DM/100 BW; H) and Low (5 kg DM/100 BW; L). After calving all cows were managed together. High FA cows presented greater intake than L cows, while M tended to have greater intake than P cows. Increased herbage allowance in late gestation in beef cows successfully improved forage intake and energy balance reflected in body condition score and metabolic and endocrine markers. Also, high forage allowance increased milk yield (5.4 vs 4.6 kg/d, P < 0.05) and calves daily gain rate during the first two months of age (0.88 vs 0.82 kg/d, P < 0.05) in H respect to L cows. Pregnancy rate was greater in H vs L cows (40 vs 28 %, P < 0,05). The endocrine metabolic response to higher forage allowance depended on parity, as primiparous cows showed a greater imbalance around calving. Moreover, most primiparous cows were not pregnant at the end of the breeding season, consistent with their prolonged anestrous. Multiparous cows had better productive and reproductive performance than primiparous cows, showing that growing cows have a pronounced negative energy balance reflected in most of the evaluated parameters.

Influence of different feeding strategies on carcass and meat quality of grassfed cull cows

Animal performance, carcass and meat quality characteristics of beef cull cows under different feeding strategies were evaluated. Cows were allotted to one of four direct grazing treatments combining different levels of forage allowance (FA) and supplementation rate (% of live body weight, BW) using rice bran (RB): T1= FA2%+RB0, T2= FA4%+RB0, T3= FA2%+RB0.8% and T4= FA2%+RB1.6%. Cows from T1 presented lower (P&lt;0.05) slaughter weight (SW) than the other three treatments. Additionally, T1 presented lower weight (P&lt;0.05) for rump and loin, striploin, sirloin, inside round and tri-tip, compared to T2, T3 and T4. Intramuscular fat (IMF), pH (48 h), Warner-Bratzler shear force (WBSF; aged for 7 or 21 days), lean colour, saturated fatty acid (SFA), monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) concentrations did not differ among treatments (P&gt;0.05). A strategic use of low RB supplementation rate grazing on an oats forage crop, improves both carcass and meat qualitry traits of cull cows, adding value and promoting healthy meat production for human consumption from grass-based production systems.

Feed intake, methane yield, and efficiency of utilization of energy and nitrogen by sheep fed tropical grasses.

Forage allowance impacts dry matter (DM) intake and the use of nutrients by ruminants. The efficient use of protein and energy from pasture is related to better livestock performance and lower environmental impacts. The aims of this study were to evaluate the effect of forage allowance levels on intake, digestibility, nitrogen (N) and energy balance, and methane (CH4) emissions by lambs fed fresh pearl millet [Pennisetum americanum (L.) Leeke]. An indoor trial was performed using lambs in a completely randomized design with four treatments [forage allowance at 1.5, 2.0, 2.5kg DM/100kg of live weight (LW), and ad libitum allowing 20% of refusals] and four replicates (lambs). Forage intake, digestibility, total urine and feces excretion, and CH4 emission were measured to calculate N and energy balances. An increase in forage allowance resulted in a linear increase in lamb forage intake, N retention, and metabolizable energy intake. Moreover, lamb CH4 emission (g/day) also increased with greater forage allowance, while CH4 yield decreased linearly as forage allowance increased. Our results indicate that maximizing forage intake improves N and energy use efficiency and mitigates CH4 yield and decreases CH4 conversion factor (Ym) by lambs fed pearl millet forage. Thus, management strategies that optimize intake of tropical forages by ruminants improve the use of nutrients ingested and mitigates negative impacts to the environment.

Seasonal patterns of endozoochory by cattle in subtropical grassland in southern Brazil

AbstractSeed dispersal influences plant community dynamics and regeneration. Zoochory by cattle is a particularly important type of dispersal in grasslands, but still poorly understood in subtropical grasslands. We studied endozoochory in a native grassland area with different grazing intensities, defined by distinct forage allowance levels. On one day in each of the four seasons of the year, dung samples were collected and kept in a greenhouse for germination over one full year. At each dung collection date, a survey of reproducing plants was conducted to relate the species composition of seed within dung to the community in dispersal phase. We used randomisation tests to compare grazing intensities and seasons in terms of dung community richness, abundance and composition. We recorded 93 species in the dung samples, with 65 species in the spring samples, 61 in summer samples, 45 in the autumn samples and 37 in the winter samples. Of the 90 species identified in the vegetation, almost 50% (43 species) also occurred in dung samples. Graminoid herbs presented the largest number of species in all samples. Grazing had no effect on overall seed and species number, but was related to compositional differences in the cattle dung communities. Grazing also influenced the species composition in relation to life cycle, by the increase of annual species at the extremes of our grazing gradient (very high or very low grazing intensities). We conclude that endozoochory by cattle is an important process for the dispersal of native species in the studied system, with potential applications in grassland management and restoration. A better understanding of the strategies involved in seed dispersal is essential to improve knowledge about grassland vegetation regeneration and maintenance.

Estimated beef cattle performance under intensive grazing systems in Uruguay

The objective of this study was to analyze the effect of the quantity and quality of the feed offered on the performance of male beef cattle, &gt;6 months old, on intensive grazing systems in Uruguay. Two hundred and fifty-four results from different experimental trials (nexp=68) performed between 1991 and 2020 by different research institutions in Uruguay were compiled and analyzed. The experiments included feeding studies with cultivated pastures as a single nutritional source (nexp=61), as well as supplementation studies on the same type of pastures (nexp=49). Simple, quadratic, multiple linear regressions and recursive partitions were performed to synthesize the information. Quadratic relationships between forage allowance (FA) and average daily gain (ADG) were observed for the different animal categories and seasons of the year. Including other parameters such as initial body weight and supplementation with energy concentrates or silages allowed to predict the ADG of animals under a wide range of feeding alternatives. Briefly, low FA levels (≤1.75 %BW) limit animal performance to maintenance gain conditions (0.2 kg/day). To achieve adequate levels of ADG (0.6-0.7 kg/day), with a low to moderate FA (between 1.75 to 3.5 %BW), the nutritional value of pasture needs to reach at least level 3 of quality (&gt;58 %ODM, &gt;13 %CP, &lt;50 %NDF, &gt;21 %Leg and &lt;19 %DR). These daily gains can be exceeded if the FA is &gt;3.5 %BW (ADG in the range of 0.7 to 1.0 kg/day). The increased response in additional ADG (0.4-0.5 kg/day) by the effect of supplementation with energy concentrate was achieved with low FA levels (≤2.25 %BW). The prediction of additional ADG using a multiple linear regression parameter allows evaluating whether supplementation is appropriate.

Performance, carcass features, and non-carcass components of sheep grazed on Caatinga rangeland managed with different forage allowances

This study aimed to evaluate the performance, carcass features, and non-carcass components of sheep managed with different levels of forage allowance [2.0; 2.5; 3.0; 3.5 kg DM/kg body weight (BW)] in the semi-arid Caatinga rangelands of northeastern Brazil. Two trials were conducted during 2013 and 2014, with stocking periods of 39 and 84 days, respectively. The experimental site was designed as a randomized whole block with split-plot array. Animals were slaughtered at the end of the stocking season. Absolute weights of the non-carcass components, empty BW, and hot carcass weights were measured. Morphometric measurements of the whole carcasses were taken. The left-hand half of each carcass was butchered into commercial cuts. A quadratic effect was seen for forage allowance levels and intake, as well as for dry matter digestibility, total and daily weight gain, BW and carcass weight, and loin cut. The optimum level of forage allowance was 2.8 kg DM/ kg BW. The characteristics of the non-carcass components (except blood and small intestines) of the sheep remained unchanged under the different forage allowance regimes.

Forage and Weather Influence Day versus Nighttime Cow Behavior and Calf Weaning Weights on Rangeland

We determined the effects of two forage allowance levels (LOW vs. HIGH) and weather conditions on daytime and nighttime movement patterns of young rangeland-raised cows. We also investigated whether calf weaning weights (n = 42) were significantly related to postcalving movement patterns of the dam. Global positioning system data were collected over 4 years by recording 5-min interval locations of 52 crossbred cows grazing a 146-ha woodland/grassland pasture for approximately 20 days. The pasture was stocked moderately in 2004 (73 AUMs) and 2005 (78 AUMs) and lightly in 2006 (34 AUMs) and 2007 (32 AUMs). Estimated forage allowance was low in 2004 and 2005 (347 and 438 kg herbage ∙ cow−1, respectively) and high in 2006 and 2007 (1104 and 1884 kg herbage ∙ cow−1, respectively). We calculated distance traveled, path sinuosity, woodland preference, and area explored for each cow during 24 h (D + N), daytime (DAY), and nighttime (PRE dawn and POST sunset) periods. Cows in LOW traveled farther than counterparts in HIGH during D + N and DAY (P < 0.01) periods but traveled shorter or similar distances during POST (P = 0.05) and PRE (P = 0.29) nighttime periods, respectively. Cows in LOW exhibited more sinuous movement paths than cows in HIGH during DAY, PRE, and POST periods (P ≤ 0.01). Cows in LOW explored larger areas and spent more time in woodlands than counterparts in HIGH (P < 0.01). Weather factors associated with thermal comfort affected daily variation in both daytime and nighttime movement patterns of cows. A dam’s movement patterns in the weeks immediately following calving were correlated (P ≤ 0.01) with steer but not heifer calf WW. Moderate stocking rates (LOW treatment) induced behaviors that resulted in higher woodland preference and heavier steer calf WW.

Daily Forage Intake by Cattle on Natural Grassland: Response to Forage Allowance and Sward Structure

We investigated the hypothesis that not only forage allowance but also sward structure affects daily forage intake by beef heifers on natural grasslands of the Pampa Biome (southern Brazil). We used data from a long-term experiment, which has been managed by forage allowance levels since 1986. The objective was to investigate sward management targets that maximize daily forage intake. During January and December 2009, we evaluated the effect of forage allowance on forage mass, sward height and tussock frequency, and its consequences on dry matter intake (DMI). The experiment was arranged in a randomized complete block design with two replicates. Treatment was level of daily forage allowance (4, 8, 12, and 16 kg dry matter [DM] per 100 kg of animal body weight [BW]). Data were analyzed using regression, principal component analysis, and descriptive analyses from three-dimensional contour graphs with the data of sward structure, DMI, and DMI rate. Results demonstrated that DMI was positively correlated to forage allowance. However, higher levels of forage allowance can cause lower intake rates of forage and nutrients. We concluded that sward targets which promoted higher DMI and DMI rate were: daily forage allowance of ~12 kg of dry matter per 100 kg of the animal’s body weight, forage mass between 1 800 and 2 300 kg DM·ha–1, sward height between 11.5 and 13.4 cm, and tussock frequency lower than 30% of occurrence in the pastures. Within these targets, a high intake of nutrients was obtained, indicating the potential use of sward structure as a tool for managing natural grasslands in order to promote high intake of forage and nutrients by cattle.

Relationship between the Rumen Microbiome and Residual Feed Intake-Efficiency of Brahman Bulls Stocked on Bermudagrass Pastures

Residual feed intake (RFI) testing has increased selection pressure on biological efficiency in cattle. The objective of this study was to assess the association of the rumen microbiome in inefficient, positive RFI (p-RFI) and efficient, negative RFI (n-RFI) Brahman bulls grazing ‘Coastal’ bermudagrass [Cynodondactylon (L.) Pers.]under two levels of forage allowance (high and low stocking intensity). Sixteen Brahman bulls were previously fed in confinement for 70 d to determine the RFI phenotype. Bulls were then allotted 60 d stocking on bermudagrass pastures to estimate RFI using the n-alkane technique. At the conclusion of the grazing period, rumen liquid samples were collected from each bull by stomach tube to evaluate the rumen microbiome. Extraction of DNA, amplification of the V4-V6 region of the 16S rRNA gene, and 454 pyrosequencing were performed on each sample. After denoising the sequences, chimera checking, and quality trimming, 4,573 ± 1,287 sequences were generated per sample. Sequences were then assigned taxonomy from the Greengenes database using the RDP classifier. Overall, 67.5 and 22.9% of sequences were classified as Bacteroidetes and Firmicutes, respectively. Within the phylum Bacteroidetes, Prevotella was the most predominant genus and was observed in greater relative abundance in p-RFI bulls compared with n-RFI bulls (P = 0.01). In contrast, an unidentified Bacteroidales family was greater in relative abundance for n-RFI bulls than p-RFI (26.7 vs. 19.1%; P = 0.03). Ruminococcaceae was the third most abundant family in our samples, but it was not affected by RFI phenotype. No effect of stocking intensity was observed for bacterial taxa, but there was a tendency for alpha diversity and operational taxonomic unit richness to increase with lower stocking intensity. Results suggested the rumen microbiome of p-RFI Brahman bulls has greater levels of Prevotella, but the bacterial community composition was unaffected by stocking intensity.

Chemical Composition, in Vitro Digestibility and Gas Production of Brachiaria Managed Under Different Forage Allowances

The objective of this study was to evaluate the chemical composition, in vitro digestibility, gas production and fermentation kinetics of three Brachiaria cultivars: Brachiaria brizantha cv. Marandu, Brachiaria brizantha cv. Xaraes, and hybrid Brachiaria cv. Mulato, subjected to different levels of forage allowance (4, 7, 10 and 13% of the animal body weight), under rotational grazing cycles. Cultivar Xaraes presented higher contents of neutral detergent fibre, neutral detergent fibre corrected for ash and protein, acid detergent fibre and lignin, and lower production of gases in 96 h in the component leaf blade. There was a decrease of non-fibrous carbohydrates and fraction B2 and an increase in the fraction C of the carbohydrates in the components stem and leaf blade over the grazing cycles in all the cultivars. Cultivar Marandu presented higher digestibility values (in vitro organic matter digestibility and in vitro dry matter digestibility) in the components stem and leaf blade. Cultivar Mulato demanded a shorter time of colonisation, according to the calculations of fermentation kinetics. Regardless of the level of forage allowance and of the grazing cycles, the three Brachiaria cultivars were characterised by great fermentation quality due to the relations of the gas production potential and the gas production after 48 and 96 h.

Forage Allowance as a Target of Grazing Management: Implications on Grazing Time and Forage Searching

This work aimed to evaluate the following hypotheses: 1) the daily grazing time (GT) and 2) forage searching are more associated with the sward structure than with the levels of daily forage allowance (FA). To this end we proposed a model that was tested through an analysis of the sward structure, grazing time, and displacement in grazing by heifers on the natural grassland of the Pampa Biome (southern Brazil), which has been managed by FA levels since 1986. For three seasons, between January 2009 and February 2010, we evaluated the effect of FA on the main descriptors of the sward structure (herbage mass, sward height, and tussocks frequency) and the effect of these on the GT, displacement rate (DR), and daily displacement (D) in grazing. The data were analyzed with the use of regression and descriptive analyses from three-dimensional contour graphs with the data of the sward structure and GT. The DR was not associated with the FA levels or sward structure; however, the DR presented a positive linear relationship with the D and GT. The incremental change in the GT was accompanied by an increase in the D. Lastly, independently of the level of the FA and season evaluated, the lower values of GT were always associated with the following structural configuration: forage mass between 1 400 and 2 200 kg DM · ha-1, sward height between 9 and 13 cm, and tussock levels not exceeding 35%. Outside these limits, a penalty occurred in the GT and displacement patterns of the heifers. We found evidence that a better understanding of the cause–effect relationships between the sward structure and the ingestive behavior of the animals demonstrates the possibility of increasing the performance of domestic herbivores with important economic and ecological consequences. El objetivo del estudio fue evaluar las siguientes hipótesis: (i) si el tiempo de pastoreo diario (TP) y (ii) la búsqueda de forraje están más estrechamente relacionados a la estructura del pasto que a los niveles diarios de oferta de forraje (OF). Con este fin, propusimos un modelo que se puso a prueba en base al análisis de la estructura del pasto, el tiempo de pastoreo y el desplazamiento en pastoreo en terneras sobre un pastizal natural del Bioma Pampa (sur de Brasil) que, desde 1986, se ha manejado con distintos niveles de OF. En tres épocas, entre Ene/2009 y Feb/2010, se evaluó el efecto de la OF sobre los principales descriptores de la estructura del pasto (biomasa de forraje, altura y frecuencia de matas) y el efecto de éstos sobre el tiempo de pastoreo (TP), la tasa de desplazamiento (TD) y el desplazamiento diario (D). Los datos fueron analizados mediante regresión y por análisis descriptivos a partir de gráficos de contorno tridimensionales en base a los datos de estructura del pasto y TP. La TD no tuvo relación con OF ni con la estructura del pasto, pero mostró una relación lineal positiva con D. Incrementos en TP estuvieron asociados a incrementos en D. El estudio demostró la importancia de la estructura del pasto al constatar que, independientemente del nivel de OF y de la época del año evaluada, los valores más bajos de TP siempre estuvieron asociados a estructuras del pasto caracterizadas por una masa de forraje de 1 400 a 2 200 kg MS · ha-1, alturas de 9 a 13 cm y frecuencia de matas en el pastizal menores al 35%. Fuera de estos límites hubo una penalización en el TP y en el patrón de desplazamiento en pastoreo de las vaquillas. Encontramos evidencias de que el mejor entendimiento de las relaciones causa-efecto entre la estructura del pasto y el comportamiento en pastoreo harían posible incrementar el rendimiento de los herbívoros domésticos, con importantes consecuencias económicas y probablemente ecológicas.

Dynamics of sward condition and botanical composition in mixed pastures of marandugrass, forage peanut and tropical kudzu

This study was carried out to evaluate the dynamics of sward condition and botanical composition of a mixed pasture of marandugrass (Brachiaria brizantha cv. Marandu), forage peanut (Arachis pintoi cv. Mandobi) and tropical kudzu (Pueraria phaseoloides), rotationally stocked at four daily forage allowance levels (6.6, 10.3, 14.3 and 17.9% of live weight). Sward condition was characterized in each stocking cycle by measuring pre- and post-grazing sward height, forage mass and percentage of bare ground. Botanical composition (grass, forage peanut, tropical kudzu and weeds) was evaluated before each stocking period. Swards under smaller forage allowances presented lower height, forage mass and ground cover. This condition favored the growth of forage peanut, which constituted 21.1, 15.2, 8.4 and 3.8% of forage mass in the last quarter of the experimental period, from the lowest to the highest forage allowance, respectively. Tropical kudzu was sensitive to all forage allowance levels and its percentage in the botanical composition was strongly reduced along the experimental period, especially during the dry season (July to September). Forage peanut cv. Mandobi and marandugrass form a more balanced mixture when pre-grazing sward height is maintained shorter than 45 cm. Tropical kudzu is intolerant to intensive grazing management systems when associated to marandugrass.

Productivity, utilization efficiency and sward targets for mixed pastures of marandugrass, forage peanut and tropical kudzu

This study was carried out to evaluate the productivity and utilization efficiency of a mixed marandugrass (Brachiaria brizantha cv. Marandu), forage peanut (Arachis pintoi cv. Mandobi) and tropical kudzu (Pueraria phaseoloides) pasture, rotationally stocked at four daily forage allowance levels (6.6, 10.3, 14.3 and 17.9% of live weight), in order to define sward management targets for these mixtures. In each stocking cycle, dry matter (DM) accumulation rates, defoliation intensity (%), grazing depth (%) and grazed horizon (cm) were evaluated. Sward targets were defined according to the sward condition that best conciliated the grass-legume balance and the equilibrium between forage production and utilization. Pastures submitted to higher forage allowance levels showed higher productivity, but were less efficiently utilized. It was not possible to establish sward management targets for marandugrass-tropical kudzu pastures. For marandugrass-forage peanut pastures the best sward state was set with forage allowance of 10.3% of live weight. Under rotational stocking, the following sward targets were suggested for these pastures in the Western Amazon: pre-grazing height of 30-35 cm (June to September) or 45-50 cm (October to May) and post-grazing sward height of 20-25 cm (June to September) or 25-30 cm (October to May).

Animal production and canopy attributes of Cynodon pasture managed under continuous stocking with wethers at three levels of forage allowance

The objective of the present experiment was to evaluate the effect of forage allowance (3, 6 or 9 kg of green leaves dry matter (DM)/100 kg of body weight (BW)) on both animal performance and attributes of Cynodon dactylon var.dactylon canopy managed under continuous stocking by wethers. The study was carried out with 27 Polwarth wethers throughout five 28-day periods, in a completely randomized experiment, which included three paddocks per treatment and three tester animals per paddock. Forage mass varied from 2878 to 6580 kg of DM/ha and was directly related to forage allowance. Leaves proportion (mean of 23%) and leaves growth rate (mean of 25 kg of DM/ha/day) varied between experimental periods in a similar rate for all treatments. Stocking rate varied from 652 to 2428 kg of LW/ha/day and was higher for the lowest forage allowance treatment. Individual BW gain (mean of 9.7 g/day) or gain per area (mean of 406 g/ha/day) were only affected by experimental periods. Forage intake was neither affected by treatments nor by periods (mean of 1042 g of DM/day). Cynodon dactylon var. dactylon pasture may be managed under continuous stocking by grazing wethers at forage allowances varying from 3 to 9 kg of green leaves dry matter/100 kg of BW without effects on canopy attributes or animal production.

Sward canopy structure and performance of beef heifers under supplementation in Brachiaria brizantha cv. Marandu pastures maintained with three grazing intensities in a continuous stocking system

The objective of this study was to assess the sward canopy structure of Brachiaria brizantha cv. Marandu pastures maintained in three grazing intensities under continuous stocking system during the rainy season, along with the behavior and performance of grazing beef heifers supplemented with mineral salt or an energy/protein supplement. Three levels of forage allowance were assessed: 2.0, 2.5 and 3.0 kg of forage/kg of live weight, combined with two supplements (ad libitum mineral salt, and an energy/protein supplement at 0.3% of live weight/day, supplied daily). The experiment was designed as a randomized block study with two replications. The supplements did not influence the variables related to the canopy structure. Canopy height was greater at higher forage allowances during the late summer and early fall. Similarly, the stem mass was greater in pastures with higher forage allowances. Animals fed protein supplement spent less time grazing than animals supplemented with mineral salt. Stocking rate was higher in pastures with lower forage allowance levels, which increased the live weight gain per grazing area. Daily weight gain did not vary according to the forage allowance levels. The use of an energy/protein supplement did not affect the stocking rate; however, it increased individual live weight gain and live weight gain per grazing area compared with mineral salt supplementation. The use of energy/protein supplements is an efficient alternative to enhance animal performance and production under grazing systems during the rainy season

Leaf Traits as Functional Descriptors of the Intensity of Continuous Grazing in Native Grasslands in the South of Brazil

Plant functional types (PFT) have been used to describe the response of native vegetation to environmental factors (i.e., fertility) and to livestock disturbance, but rarely under conditions of continuous grazing. In this work we investigate whether the longterm response of grassland communities submitted to a gradient of continuous grazing pressure can be described with such an approach. After 15 yr of differentiation of the grazing pressure applied to native grasslands we measured leaf dry-matter content (LDMC) and specific leaf area (SLA) of Poaceae populations of the communities. A grazing pressure gradient was created by levels of daily forage allowance: 4, 8, 12, and 16 kg of dry matter per day per 100 kg of animal live weight, monitored monthly. PFTs were defined by numerical analysis, where an algorithm finds the optimal trait subset based on the agreement between matrices of species 3 traits, paddocks 3 grass biomass, and environmental variables (levels of forage allowance and soil characteristics). The results show that it is possible to describe a gradient of grazing pressure by means of LDMC and/or SLA measured only on the Poacea contributing at least 80% of the total Poaceae biomass. Four PFTs were differentiated by these leaf traits. PFTs having low LDMC and high SLA are characteristic of high intensity of use and are made up largely of stoloniferous C4 species typical of rapid resource capture strategies. Conversely, PFTs characterized by high LDMC and low SLA include species that are representative of low grazing pressure. Variations in the aggregate value of traits are due to changes in the species proportions and not to leaf-size adaptation as hypothesized. We conclude than in the absence of a gradient of fertility, plants with strategies of resource capture tend to be more represented under high grazing pressures. This situation results in a loss of functional diversity, but in particular a reduction in forage availability, which is incompatible with high animal production.

Ganho de peso de novilhas em pastagem nativa da Serra do Sudeste do RS submetida ao controle de plantas indesejáveis e intensidades de pastejo

Este trabalho teve como objetivo avaliar o efeito de métodos de controle de espécies indesejáveis e de intensidades de pastejo sobre o desempenho animal em pastagem nativa da Serra do Sudeste do Rio Grande do Sul. Foram utilizados os métodos de controle: roçada de primavera (RP), roçada de outono (RO), controle químico (Q) e um tratamento testemunha (T), todos submetidos a dois níveis de oferta de forragem, médio (8%) e alto (14%), expressos em kg de matéria seca diariamente ofertada para cada 100kg de peso vivo animal. O delineamento experimental empregado foi o de blocos completamente casualizados, num arranjo fatorial com duas repetições. A análise estatística não demonstrou interação entre os fatores estudados, bem como existência de diferença entre os métodos de controle de espécies indesejáveis para as variáveis de produção primária e secundária (P&gt;0,1). Não houve diferença de ganho médio diário entre os níveis de oferta de forragem estudados (P&gt;0,1). Animais submetidos à alta oferta de forragem apresentaram menor perda de peso por unidade de área (P&lt;0,1).

Grazing methods and stocking rates for direct-seeded alfalfa pastures: III. Economics of alternative stocking rates for alfalfa pastures.

A framework that permits estimation of economically optimal stocking rates for alternative economic parameters and alfalfa forage allowance was developed and applied to a controlled grazing experiment conducted with Holstein steers (243 kg) placed on direct-seeded alfalfa pastures in central Michigan. Responses of ADG to alternative levels of forage allowance (FA) were summarized by a quadratic function and the associated gains/hectare were calculated. The standard stocking rate (SSR; standard livestock units/ha) that maximized gain/hectare increased with FA and was greater than that which maximized ADG. Net returns to fixed resources(NRFR)/hectare were calculated for alternative SSR and economically optimal SSR were identified under various levels of herbage mass (kg/d). The SSR that maximized NRFR were between the SSR that maximized ADG and gain/hectare. Magnitude of the sale price discount for heavier calves, the slide, influenced the optimal SSR and the sensitivity of net return to SSR. The economically optimal SSR increased as the slide increased because animals stocked under higher SSR weighed less off pasture and therefore received a lower price discount.

Diet quality and diet selection of steers grazing in a rotational system at four levels of forage allowance on a rangeland

Diet quality and diet selection of steers grazing in a rotational system at four levels of forage allowance on a rangeland

Diet quality and diet selection of steers grazing in a rotational system at four levels of forage allowance on a rangeland

Diet quality and diet selection of steers grazing in a rotational system at four levels of forage allowance on a rangeland