Botanical Composition Of Diets Research Articles

Using n-alkanes to estimate herbage intake and diet composition of cattle fed with natural forages in Madagascar

Accurate estimates of feed intake are important in order to develop accurate ration formulations, for selecting livestock according to production efficiency, and for reducing environmental impact of livestock. The present study assessed the accuracy of n-alkanes to estimate individual herbage intake and diet botanical composition of cattle fed natural forages, typical to Madagascar. The effect of two different forage allowances and seasons on the herbage intake was also tested. Eight Norwegian red pie sires (232 ± 20 kg BW) were orally dosed twice daily with paper pellets containing 456.61 ± 21.64 mg of C32 alkane as external marker. Animals were housed in individual pens and fed with mixtures of five forages species typically used by farmers in the rainy season (Aristida multicaulis, Hyparrhenia rufa, Imperata cylindrical, Urochloa brizantha and Stylosanthes guyanensis) and the dry season (Chrysopogon serrulatus, Cynodon dactylon, Imperata cylindrica, Lolium multiflorum and Leersia hexandra Sw). The sires were randomly assigned to two different forage allowances: (i) ad libitum with a refusal of 5 % and (ii) 1.1 % DM of body weight (BW). The n-alkane pairs C31:C32 and C32:C33 and the ratio C32/Acid Insoluble Ash (AIA) in plants and faeces were used to estimate the herbage intake. The botanical composition of the diet was estimated using the n-alkane profile from C27 to C35 in individual plant species and faeces, by least squares optimization. The n-alkane pairs underestimated (P < 0.0001) the herbage intake by 25 % in the dry season, for both forage allowances and 26 % for animals receiving ad libitum diet, regardless of the season. In contrast, the intake estimates based on both n-alkane pairs did not differ from the measured intake for animals receiving low forage allowance during the rainy season. The C32/AIA underestimated the actual herbage intake, by 50 %, for animal consuming ad libitum diet, for both seasons (P < 0.0001). The n-alkane faecal recovery (AFR) corrections factors set affected (P < 0.01) the estimated proportions of each plant species, that comprised the diet in both seasons. The application of appropriate AFR permitted to have a better accuracy of diet botanical composition estimates. It is concluded that plant wax n-alkanes are advantageous for estimating both diet botanical composition and herbage intake in cattle. However, for improving the prediction, it is important to measure the actual AFR before the calculation.

Seasonal changes in feed intake, diet digestibility and diet composition by lactating and non‐lactating goats browsing in a semi‐arid rangeland of Argentina

AbstractWe determined the seasonal nutrient and secondary compound intake, in vivo diet digestibility (DD) and diet species composition of goats in different physiological states in a desert rangeland of Argentina. During the wet and the dry seasons, 24 mature female Creole goats (six non‐lactating, non‐pregnant and six lactating in each season) were used in a 2 × 2 factorial design. Diet botanical composition, DD and dry‐matter intake (DMI) were estimated by the combined use of visual observation, microhistological analyses of faecal samples and n‐alkane technique. Browse species dominated the goats’ diets (&gt;80%) in both seasons and physiological states, with a twofold increase in the proportion of forbs during the wet season (p &lt; 0.10). Lactating goats showed greater DMI than non‐lactating animals, and they also displayed greater intakes of some tanniferous (Mimosa ephedroides) and high‐protein (Atriplex lampa) shrubs (p &lt; 0.10). Lactating and non‐lactating goats selected diets with adequate crude protein (CP) and fibre content but insufficient energy, although lactating goats tended to increase energy and tannin content in their diets (p &lt; 0.20). Physiological state did not influence DD, but digestibility was greater (p &lt; 0.10) in the wet season, attributed to the greater protein content and lower tannin content of the diet. These results have important implications for managerial interventions on traditional goat production systems in the study area aiming at enhancing goat nutrition and welfare, as well as the sustainability of rangeland resources in the region.

414 Estimates of Botanical Composition of Diets from Analyses of Chemical Components or NIRS Among Cattle Fed Binary Mixtures of Cornstalk and Noncornstalk Residue.

414 Estimates of Botanical Composition of Diets from Analyses of Chemical Components or NIRS Among Cattle Fed Binary Mixtures of Cornstalk and Noncornstalk Residue.

The Influence of Cow Age on Botanical Composition of Diets in Mountain Riparian Areas in Eastern Oregon of the United States

&lt;p&gt;The objective of this study was to evaluate the effect of cow age on botanical composition of diets in mountain riparian areas. Treatments consisted of 30 first-calf heifers, and 30 mature cows randomly assigned to four pastures (2 pastures/treatment, average 21.5 ha) in a 2-year study with a cross-over design. Botanical composition of diets was determined in fecal samples obtained from 10 animals in each treatment (5 per pasture) on the fourth week of 35 to 42-days grazing periods using the microhistological technique. Crude protein (CP) content and &lt;em&gt;in vitro&lt;/em&gt; dry matter digestibility (IVDMD) were determined, and correction factors were calculated for 22 major plant species. In digested samples, grasses were overestimated, whereas, all forbs but northern bedstraw (&lt;em&gt;Galium boreale &lt;/em&gt;L.), were underestimated, and all shrub species were overestimated except common snowberry (&lt;em&gt;Symphoricarpos albus &lt;/em&gt;L.). Ponderosa pine (&lt;em&gt;Pinus ponderosa &lt;/em&gt;Dougl.) was highly overestimated after digestion. There was no difference between cattle age class in the total number of plant species found in the diets (&lt;em&gt;p&lt;/em&gt; &amp;gt; 0.10) averaging in 41 species. Most individual grass and grasslike species made up more than 5% of the diets, while all individual forb, shrub, and tree species were minor components, not exceeding 5%, except ponderosa pine. Western wheatgrass (&lt;em&gt;Agropyron smithii &lt;/em&gt;Rybd.) and tufted hairgrass (&lt;em&gt;Deschampsia caespitosa &lt;/em&gt;(L.) Beauv.) accounted for over 10% of the diets. Heifers consumed more (&lt;em&gt;p&lt;/em&gt; &amp;lt; 0.05) grasses and fewer (&lt;em&gt;p &lt;/em&gt;&amp;lt; 0.10) shrubs and trees compared to mature cows. The diet of heifers contained more western wheatgrass, Baltic rush (&lt;em&gt;Juncus balticus &lt;/em&gt;Willd.), and pinegrass (&lt;em&gt;Calamagrostis rubescens &lt;/em&gt;Buckl.) (&lt;em&gt;p&lt;/em&gt; &amp;lt; 0.10), but less Kentucky bluegrass (&lt;em&gt;Poa pratensis &lt;/em&gt;L.) (&lt;em&gt;p&lt;/em&gt; &amp;lt; 0.01), than the diet of mature cows. The proportion of ponderosa pine needles was higher in the diet of mature cows (&lt;em&gt;p&lt;/em&gt; &amp;lt; 0.10), than in the diet of first calf heifers. In summary, mature cows appeared to have selected a diet that contained less grasses and more shrubs and trees compared to younger cows.&lt;/p&gt;

UTILIZACIÓN DEL FORRAJE Y SELECCIÓN DE LA DIETA POR CABRAS PASTANDO EN UN MATORRAL SARCOCAULESCENTE EN EL NOROESTE DE MÉXICO

Sarcocaulecent scrubland is representative of the Sonoran Desert of Baja California Sur, Mexico. In this area 92 % of its flora is shrubs and 23 % of these are endemic species, however, the ecological impact of animal production is unknown. The objectives of this study were to determine and to com¬pare during two years the preference and use of plant species by grazing goats. Data field collections were done from June 2006 through June 2008. Botanical composition of diet and the study area data sets were used to estimate preference and similarity indices. In the studied site total plant species were 78 and goats utilized 41 throughout the study, in each collection date goats utilized 10 to 24 species. Mean similarity index was 26 % (16 to 32 %), both preference and utilization were highly variable between collection dates for each plant species. Preference by goats was not in accordance with similarity. This pattern of feeding behavior may indicate a conservative strategy of forage utiliza¬tion by goats.

Effect of the physiological state of Criollo goats on the botanical composition of their diet in NE Mendoza, Argentina

The botanical composition of the diet and species preference of grazing goats in different physiological states were evaluated in the autumn and winter seasons. The study was performed in a desert rangeland in the northeast (NE) Mendoza region in Argentina. Food availability was estimated from forage species cover. Rectal grab faecal samples were collected from goats, and the botanical composition of the goat diet was determined using a microhistological technique. Goat preferences for each species consumed were calculated based on Ivlev's index. Nutritional composition and secondary compounds of forage species were determined. Correlations between diet and availability; and between goat preference and nutritional composition of forage species were also estimated. The habitat consisted of a dominant woody stratum associated with an herb stratum primarily composed of grasses. Goats in different physiological states utilised a significantly higher proportion of woody vegetation compared to grass (p<0.01). When grass availability was high (autumn), the herb stratum was more utilised by pregnant and lactating goats than by dry goats (p<0.05). In the winter, the diet of lactating goats consisted of more Atriplex lampa compared to the diet of dry goats (p<0.05), probably due to the high crude protein content of the plant. Goats consumed forage species with highly variable total phenol and tannin contents, which did not negatively affect selection. Correlations between diet and availability were high in the winter for dry (rs=0.88, p<0.02), pregnant (rs=0.93, p<0.01) and lactating goats (rs=0.97, p<0.01) but were not significant in the autumn. A significant correlation between preference and crude protein was shown during the autumn season for pregnant and lactating goats (rs=0.6, p<0.05). Forage availability was the main factor influencing diet selection in this arid environment. When food availability was not a limiting factor, goats selected a diet that most closely matched their nutritional requirements. Physiological state modified nutrient requirements and affected diet selection in that pregnant and lactating goats selected forage species with high protein contents.

Diet Botanical Composition of Goats on Rangeland Treated with Trenbolone Acetate

Diet Botanical Composition of Goats on Rangeland Treated with Trenbolone Acetate

Animal diet botanical composition compared with pasture species composition as indicators for pasture status in the semi-arid rangeland of Sudan (South Darfur State)

ABSTRACT A study was conducted during the period 2006/08 in the semi-arid rangeland of South Darfur State, Sudan at Eldien locality (latitudes 9°-30 and 11°-45 north and longitudes 25°-30 and 27° east, ecologically in the low rainfall woodland savannah with an annual rainfall between 400-600 mm).. The objective of the study was to evaluate animal diet botanical composition in comparison with pasture species composition as indicators for pasture status in the area. Data were collected for pasture species composition (Parker loop method, 1955) and animal diet botanical composition (Van Dyne Method,1968) over two years both in early wet and late dry summer seasons. Results showed that diet botanical composition was composed of pure herbaceous plant species during rainy and early dry summer seasons and a mixture of browse and herbaceous species in the late dry summer season. Calcium in animal diet was present in a suitable concentration, whereas phosphorous was present at low concentration. Although the percent species composition of the natural pasture provides an indicator of range composition, animal diet botanical composition could be used as an indicator of the pasture status. Both parameters could be very useful in designing range management practices, such as selecting species required for reseeding deteriorated range and in identifying key species that will form a base for range management.

Diet botanical composition and rumen protozoa of sheep in Brazilian Semi-Arid area

This study aimed to determine the influence of seasonal variations on diet botanical composition and rumen protozoa of five rumen fistulated Santa Ines crossbred sheep kept in natural Caatinga vegetation pasture, Pernambuco State, Brazil. Samples were collected in July 2005 and January 2006, the respective rainy and dry seasons. Botanic composition of animal diet was determined by analysis of ruminal extrusa. The rainy season diet was composed mainly by herbaceous and grass species (88%), with Herissantia tiubae making up 51.7%. The dry season diet consisted of shrub species (67.4%), mainly Capparis yco (26.3%) and Bauhinia cheilantha (22.3%). Under such conditions variations in protozoa populations were observed, with the higher total concentration (p<0.05) during the rainy season. Populations of Entodinium genus predominated in both seasons, although decreasing (p<0.05) during the dry season, as did the Epidinium and Eremoplastron genera. The Dasytricha, Diploplastron, Eudiplodinium and Isotricha genera had the higher concentrations (p<0.05) in the dry season.

Botanical Composition of Alpaca (Lama pacos Linn.) Diet in a Central Mediterranean Range of Chile

CHILEAN JOURNAL OF AGRICULTURAL RESEARCH 68:136-145 (APRIL-JUNE 2008) A B S T R A C T The re-introduction of domestic South American camelids (alpacas and llamas) in the central zone of Chile makes it necessary to study their behaviour and adaptability. Since it is fundamental to characterize the camelid’s diet, the present work had as an objective the determination of the plant species selected by the alpacas (Lama pacos Linn.) in different phenological stages (vegetative, reproductive and dry season). The study was carried out over three years in a paddock of 2.5 ha of sparse shrubland dominated by Acacia caven (Mol.) Mol. and annual species in the herbaceous stratum, which were continually grazed by five male alpacas. The botanical composition and the forage dry matter available for grazing in the pasture was evaluated. Botanical composition of diets was estimated with the microhistological technique, using dung samples collected directly from the rectum. During the vegetative season, the most consumed plant species were annual and perennial grasses. In the reproductive season, the most important components of the diet were woody plant species, annual grasses and forbs. In the dry season, the diet was composed of a high percentage of woody plant species.

Composição botânica da dieta e protozoários do rúmen de ovinos.

Objetivou-se neste trabalho determinar a influência estacional sobre a composição botânica da dieta e nos protozoários do rúmen de cinco ovinos mestiços Santa Inês providos de fístulas ruminais e mantidos em pastagens naturais de vegetação de Caatinga, Estado de Pernambuco, Brasil. As amostras foram coletadas em julho de 2005 e janeiro de 2006, compreendendo, respectivamente, as estações chuvosa e seca. A composição botânica da dieta foi determinada através de amostras de extrusa coletadas via fístula ruminal, que após serem analisadas indicaram que durante a estação chuvosa as espécies vegetais mais comuns na dieta dos animais são herbáceas e gramíneas (88%), com Herissantia tiubae representando 51,7% do total. Na estação seca a dieta consistiu de espécies arbustivas (67,4%), comumente Capparis yco (26,3%) e Bauhinia cheilantha (22,3%). Sob tais condições, foram também verificadas variações nas populações de protozoários ruminais, os quais apresentaram maior concentração total (p

The inclusion of a daisy plant ( Chrysanthemum coronarium) in dairy sheep diet. 1: Effect on milk and cheese fatty acid composition with particular reference to C18:2 cis-9, trans-11

An experiment was carried out to evaluate the effect on milk and cheese fatty acid composition of the inclusion of Chrysanthemum coronarium L., (Asteracea) into dairy sheep diet. Plots sown either with a binary mixture consisting of Lolium rigidum Gaudin and Medicago polymorpha (LM) or a ternary mixture including the above species and C. coronarium were (LMC) grazed by groups of Sarda dairy ewes during May. The botanical composition of diet, as measured by n-alkane method, showed that 34% of LMC group diet consisted of Chrysanthemum flowers and leaves. Exposure of sheep to this non-conventional forage did not affect animal performance and milk composition (fat and casein, P > 0.05) but resulted in different milk and cheese fatty acid composition. In particular conjugated linoleic acid, vaccenic acid and linoleic acid were all higher in LMC than LM groups ( P < 0.05). The probable main reason was the higher proportion of linoleic acid in Chrysanthemum forage and hence in LMC than LM diet.

Uso de N-alcanos na estimativa da composição botânica em amostras com diferentes proporções de Brachiaria brizantha e Arachis pintoi

Este trabalho foi conduzido para se determinar a composição de n-alcanos (C24 a C36) em diferentes proporções de dietas hipotéticas de Brachiaria brizantha Stapf. cv. Marandu e Arachis pintoi Koprov &amp; Gregory. cv. Amarillo (0; 15; 30; 45; 60 e 100% de Arachis pintoi) e identificar a combinação de alcanos que permite calcular a composição botânica de dietas com o menor valor residual (real menos o estimado). As forragens foram amostradas no verão e os n-alcanos extraídos pelo método de saponificação direta, sendo identificados e quantificados por meio de análise de cromatografia gasosa. O alcano C34 foi utilizado como padrão interno. As proporções de A. pintoi nas dietas foram estimadas pela minimização do z (soma dos quadrados dos desvios) entre a proporção real dos alcanos analisados e as proporções pré-estabelecidas (tratamentos), utilizando-se a equação de Duncan et al. (1999). Observou-se que houve predomínio das cadeias carbônicas ímpares e que a concentração total de n-alcanos decresceu à medida que se aumentou a proporção de A. pintoi nos tratamentos. Estimativas acuradas da composição botânica de misturas de A. pintoi com B. brizantha foram obtidas utilizando-se os alcanos C29, C31, C33 e C35. O alcano C35 foi fundamental para a qualidade das estimativas. Os resultados indicaram o grande potencial da técnica para estudos com animais em pastejo.

Seleção de dieta por bovinos em pastagem cultivada em área de várzea

O trabalho foi realizado em uma área de 3,0ha de várzea, situada no Campus da Universidade Federal de Santa Maria, Rio Grande do Sul (Brasil), cultivada com Lolium multiflorum Lam. e Trifolium repens L, onde se destacavam, também, alguns componentes nativos. O objetivo deste trabalho foi acompanhar, de forma paralela às ações de manejo, a dinâmica da composição botânica da dieta selecionada por bovinos em pastejo, sob o efeito de tratamentos (diferentes doses de P e K) e da sazonalidade. O delineamento experimental foi o completamente casualizado com duas repetições. O método de pastejo adotado foi o contínuo, com lotação fixa e carga variável. No inverno, primavera e verão de 1999/2000, foi determinada a composição botânica da dieta pelo método de análise microhistológica de fezes, através da diferenciação da epiderme foliar de L. multiflorum Lam., T. repens L., e dos componentes nativos Paspalum urvillei Steud., Setaria geniculata (Lam.) Beauv. e Echinochloa spp. Os resultados foram comparados através de testes de aleatorização. A composição botânica da dieta não foi afetada pelos tratamentos impostos à pastagem (P=0,87), mas houve efeito das épocas de amostragem sobre a seleção (P=0,03). As espécies da flora nativa, embora prejudicadas pelo manejo imposto, foram selecionadas pelos animais em pastejo, configurando-se num importante recurso forrageiro.

Seasonal botanical and chemical composition of sheep and goat diets on a common range in eastern Africa

The botanical and chemical composition, intake and digestibility of local sheep (Ovis aries) and goat (Capra hirtus) diets were evaluated over the wet (growing) and dry (dormant) seasons. Diet botanical composition was related to the vegetation composition on the range. Commiphora riperia and Acacia tortilis were the most dominant tree species, while Duosperma kilimandscharicum and Premna hildebrandtii were the most dominant shrub species. Enteropogon macrostachyus, Cenchrus ciliaris and Chloris roxburghiana were the most abundant grass species, while Brepharis integriifolia, Commelina benghalensis and Macrotylomma axillare were the most dominant forb species. Grasses increased towards the end of the wet season and the beginning of the dry season, while the forbs decreased. Eragrostis caespitosa, Cenchrus ciliaris, Eragrostis superba, Enteropogon macrostachyus and Themeda triandra were the most dominant grass species in sheep diets during both seasons, accounting for over 82% of the diet. Acalypha fruticosa, Grewia similis and G. bicolor were the most important browse species in goat diets in both seasons, while Eragrostis caespitosa and E. superba were the most common grass species during both seasons. Overall, goat diets comprised 81% browse, 17% grass and 2% forbs during the wet season; and 82% browse, 15% grass and 3% forbs during the dry season. Whilst the goat diets had higher (P < 0.05) Crude Protein (CP) content than sheep diets during both seasons, the sheep diets were lower in lignin content than goat diets during the wet season. Overall, the goat diets were lower in Neutral Detergent Fibre (NDF) and Acid Detergent Fibre (ADF) than sheep diets during both seasons. There was no difference (P < 0.05) in digestibility between the two animal species. However, it was higher (P < 0.05) during the dry than the wet season. Although sheep and goats are commonly herded together in east African rangelands, they have differing abilities to utilise forages. These differences must be taken into consideration in grazing management decisions, and selected grazing areas should be able to cater for the forage requirements of both species.

The possible use of n-alkanes, long-chain fatty alcohols and long-chain fatty acids as markers in studies of the botanical composition of the diet of free-ranging herbivores

Few methods exist for quantitatively estimating the diet composition of free-ranging herbivores. Because their patterns differ between species, plant n-alkanes have been successfully used as faecal markers to estimate the botanical composition of simple diets, however, the reliability of this methods may decline as the number of dietary plant species increases (Dove and Mayes, 1996). The objective of this study was to examine whether additional plant-wax compounds, such as long-chain fatty alcohols (Alc) or long–chain fatty acids (Ac) could be used along with n-alkanes (Alk) to allow reliable diet composition estimates to be made in herbivores consuming complex diets.

Pasture management effects on diet composition and cattle performance on continuously stocked rhizoma peanut-mixed grass swards.

In Florida, rhizoma peanut (RP; Arachis glabrata Benth.), a tropical legume, combines the attributes of excellent nutritive value, competitive ability with tropical grasses, and high animal performance. The objective of this study was to determine the effects of spring N fertilization (0 vs 35 kg/ha) and summer stocking rate (1.5 and 2.5 bulls/ha) on herbage mass, nutritive value, herbage allowance, and diet botanical composition of grazed RP-grass swards and their interaction with growth and development of bulls (Senepol, and Brahman or Angus). The study was conducted in 1995 and 1996 at the USDA, ARS, Subtropical Agriculture Research Station in Brooksville, FL. Nitrogen was applied in April of each year, and all pastures were stocked with 1.5 bulls/ha until approximately July of each year, when stocking rate was increased on half the pastures to 2.5 bulls/ha. Herbage mass (HM, kg/ha), herbage allowance (HA, kg/kg BW), nutritive value (CP and in vitro organic matter digestibility [IVOMD]), and diet botanical composition (fecal microhistological) readings were determined. Animal measurements included total and seasonal (spring vs summer), ADG, hip height (cm), scrotal circumference (SC, cm), and plasma urea nitrogen (PUN, mg/dL). Herbage mass (3.0 +/- 0.12 Mg/ha and 3.4 +/- 0.13 Mg/ha in 1995 and 1996, respectively) was not affected by nitrogen fertilization or stocking rate but was affected by season (P < 0.05) due to increased plant growth rate associated with summer rainfall. Stocking rate did affect herbage availability, but it never fell below 3 kg/kg BW, indicating herbage availability was never limiting. Crude protein (200 to 140 g/kg) and IVOMD (650 to 540 g/kg) were not affected by treatment, but declined (P < 0.001) from spring until fall. Treatments also had no effect on diet botanical composition. Summer ADG averaged about 0.2 kg/d lower than spring ADG, due, in part, to seasonal declines in nutritive value. Because herbage allowance was never limiting, full-season ADG was not affected by stocking rate or N fertilization and averaged 0.61 +/- 0.03 and 0.60 +/- 0.02 kg/d in 1995 and 1996, respectively. There were season x breed interactions (P < 0.05) for ADG due to greater declines during the summer for Angus than for Senepol or Brahman. There were no differences in final BW, SC, BCS, hip height, or PUN due to treatments, but breed differences were noted (P < 0.05) for all measures except BCS.

Diet selection by steers using microhistological and stable carbon isotope ratio analyses.

Two methods of determining diet botanical composition, microhistological (MH), and stable carbon isotope ratio (CR) analyses were used to determine botanical composition of ingesta and fecal grab samples in steers grazing rhizoma peanut-mixed tropical grass pastures. Three pastures were used over two grazing seasons, 1992 and 1993, in Brooksville, FL. A weighted-disc double-sampling technique was used to determine forage mass and botanical composition, percentage of rhizoma peanut (Arachis glabrata), grass (Paspalum notatum and Cynodon dactlyon), and forb (primarily Chenopodium ambrosioides) on offer every 28 d throughout the grazing seasons. There was an effect of sampling date (P<.001), sampling date x pasture (P<.001), and sampling date x year (P<.001) on forage mass on offer. There was a pasture x year x sampling date interaction (P<.001) for all botanical components. In 1992 and 1993, using cannulated steers sampled every 56 d, there were interactions with year for rhizoma peanut and forb (P<.05), but not for grass with MH analysis (components: rhizoma peanut, grass, and forb). Ingesta and fecal rhizoma peanut (r = .73 and .92 for 1992 and 1993, respectively) and ingesta and fecal forb (r = .86 and .98 for 1992 and 1993, respectively) were positively correlated (P<.001). Ingesta and fecal grass were positively correlated (r = .52, P<.001), but the correlation was not as high. With the CR analysis (components: Calvin cycle [C3] plants and C4-dicarboxylic acid pathway [C4] plants), ingesta and corrected fecal (corrected for in vitro organic matter digestibility [IVOMD]) C3 plants were positively correlated (r = .62; P<.001). Diet composition of fecal grab samples from noncannulated steers, collected on the same sampling schedule as for hand-clipped pasture samples, differed at times due to the complexity of the sward (both rhizoma peanut and forb constituted a single component, C3, in the CR analysis). Based on these results, if there is a substantial contribution of forb to the diet, fecal microhistological analysis may be more informative than fecal carbon ratio analysis for estimating diet selection by cattle grazing tropical pastures.

Diets of 3 Cattle Breeds on Chihuahuan Desert Rangeland

Diet botanical composition, fecal nitrogen percent, and fecal phosphorus percent were determined seasonally during 1991 and 1992 for 3 cattle breeds (Barzona, Brangus, Beefmaster) grazing late-seral Chihuahuan Desert rangeland in southcentral New Mexico. These 3 cattle breeds are considered to be well adapted to harsh environments. Cattle breed main effect was non-significant (P > 0.05) for diet botanical composition. However, season main effects (P < 0.05) did occur for some diet botanical composition components. Total grasses in cattle diets were highest in January and lowest in June. Dropseeds (Sporobolus sp.), black grama (Bouteloua eriopoda Torr.), and threeawns (Aristida sp.) were the primary grasses consumed by cattle. Forb consumption was highest in June lowest in January. Honey mesquite (Prosopis glandulosa Torr.) consumption by cattle was highest in August and lowest in January. It was the primary shrub in cattle diets. Breed X season interactions (P < 0.05) occurred for a few diet botanical composition components, but the small magnitude of the values and lack of consistency prevented drawing definite management implications. Fecal nitrogen values showed differences (P < 0.05) among breeds in some seasons. However due to lack of consistency no definite conclusions could be drawn regarding superiority of 1 breed compared to another in diet nutritional quality. Both fecal nitrogen and phosphorus concentrations showed cattle diets to be lowest in quality in winter and highest in summer. From a practical standpoint, this study showed no definite advantage of any breed studied in diet botanical composition or in diet quality.

Protein Quality of Cottontail Rabbit Forages following Rangeland Disturbance

Seasonal changes in the botanical composition of diets and protein quality of forages consumed by cottontail rabbits (Sylvilagus floridanus) were monitored on disturbed and undisturbed upland hardwood forest-tallgrass prairies in central Oklahoma. Our primary objective was to evaluate the seasonal dynamics of levels of selected amino acid nutrients in forages required for maintenance, growth, or reproduction, and explore bow these changes respond to habitat disturbance resulting from the use of herbicides and fire. Microhistological analyses of stomach digesta indiccated that summer diets were dominated by Panicum oligosanthes Schultes, Croton spp. and Sporobolus asper (Michx.) Kunth; winter diets were dominated by Bromus spp., P. oligosanthes, and Antennaria spp. Differences in the botanical composition and quality of diets between disturbed and undisturbed habitats were of little biological significance. Changes in the concentration of essential amino acids due to plant maturity were minimal in both summer and winter. Estimated levels of nitrogen and essential amino acids in reconstructed diets (based on food habits) appeared to be low, especially for the sulfur-containing amino acids (methionine + cystine) in summer.