Dean M. Anderson

Relationship of Tarbush Leaf Surface Terpene Profile with Livestock Herbivory

Tarbush (Flourensia cernua DC.) is a Chihuahuan Desert shrub with a resinous leaf surface containing terpenes that may affect livestock herbivory. Cattle, sheep, and goats were densely stocked in paddocks containing tarbush in two consecutive years for six to nine days and defoliation of 160 plants was recorded daily. Plants were categorized as exhibiting high or low defoliation. Leaves were collected from these plants the third year for chemical analysis. A selection procedure was used to generate two variable sets closely related to defoliation category. One set contained 14 variables (dry matter, ash, α-pinene, sabinene, 3-carene, p-cymene, limonene, camphor, borneol, cis-jasmone, β-caryophyllene, α-humulene, ledene, and flourensadiol) and the other set contained 14 unidentified compounds. When subjected to multivariate analysis, each group distinguished between the two defoliation categories (P < 0.001 and P < 0.0019 for known and unknown variable sets, respectively). These data support the hypothesis that leaf surface chemistry of individual tarbush plants is related to extent of defoliation by livestock.

Virtual fencing – past, present and future

Virtual fencing is a method of controlling animals without ground-based fencing. Control occurs by altering an animal’s behaviour through one or more sensory cues administered to the animal after it has attempted to penetrate an electronically-generated boundary. This boundary can be of any geometrical shape, and though unseen by the eye, is detected by a computer system worn by the animal. The most recent autonomous programmable systems use radio frequency (RF) signals, emanating from global positioning system (GPS) satellites to generate boundaries. Algorithms within a geographic information system (GIS) within the device’s computer use the GPS and other data to determine where on the animal a cue, or cues, should be applied and for how long. The first commercial virtual fencing system was patented in 1973 for controlling domestic dogs. Virtual fencing was used for the first time to control livestock in 1987. Since then proof-of-concept research using commercial, as well as custom designed systems have demonstrated that virtual fencing can successfully hold as well as move livestock over the landscape. Commercial virtual livestock control systems do not yet exist but research continues towards this goal. Pending research needs relating to this method of animal control are discussed in light of currently available technologies.

Increasing Shrub Use by Livestock in a World with Less Grass

Abstract Much of the worlds rangeland is dominated by woody species. Competing land uses and continued encroachment of woody species into non–woody-dominated rangelands have reduced grasslands in many parts of the world. Land use conversions to fuel and feed global populations, especially the increasing number of middle class people seeking broader, meat-based diets, will certainly continue. Halting and/or reversing further encroachment of woody species into grasslands is slow, expensive, and in some cases not possible. Yet, global livestock numbers continue to increase to meet the growing demand for red meat and other livestock products. How do we reconcile a world with less grass and the concurrent increased demand for forages to feed livestock? Strategies and mechanisms are needed to safely enhance shrub use by ruminants in order to capitalize on a presently underutilized forage resource. A number of approaches are presently available (e.g., choosing appropriate species and breeds, providing dietary supplements and additives, behavior modification, genetic selection) to increase shrub consumption, and new technologies such as biochemical markers of shrub intake need to continue to be identified and developed. Such strategies could provide important means for rural communities to adapt to changing land cover and climate. Resumen La mayor parte de los pastizales del mundo están dominados por especies leñosas. El cambio de uso de suelo y la continua expansión de especies leñosas dentro de pastizales dominados por no-leñosas ha reducido los pastizales en muchas partes del mundo. La conversión de tierras para abastecer y alimentar la población global, especialmente con el aumento en el número de personas de clase media que buscan dietas basadas en carne ciertamente continuara. El vacilante y/o posible re vertimiento de la invasión de especies leñosas en los pastizales es lento, caro y en algunos casos imposible. De hecho, el número global de ganado continuara creciendo para cubrir la demanda de carne roja y otros productos derivados del ganado. ¿Cómo podemos conciliar a un mundo con menos pasto y la creciente demanda de forrajes para alimentar el ganado? Se necesitan estrategias y mecanismos que de manera segura promuevan el uso de arbustos por los rumiantes con el fin de capitalizar los recursos forrajeros subutilizados actualmente. Hay disponibilidad de puntos de vista (ejm. Seleccionar razas y especies apropiadas, proveer suplementos dietéticos y aditivos, modificar el comportamiento, selección genética) para aumentar el consumo de arbustos y nuevas tecnológicas tales como los marcadores bioquímicos en consumo de arbustos que se necesita continuar en la identificación y desarrollo de estos. Estas estratégicas pueden ofrecer importantes medios en las comunidades rurales para adaptar en la cambiante cobertura del suelo y el clima.

Relationship of tarbush leaf surface secondary chemistry to livestock herbivory.

Tarbush (Flourensia cernua DC.) is an abundant but generally unpalatable shrub native to the Chihuahuan Desert. The objective of this study was to examine the leaf surface chemistry of tarbush in relation to degree of use by ruminants. Mature tarbush leaves were collected on 2 sites during 2 periods approximately 2 weeks apart from plants exhibiting either high (> 45%) or low (< 10%) use when browsed by cattle, sheep, and goats confined to a small area (5 plants per use category for each site/period combination). A greater (P < 0.05) concentration of epicuticular wax was detected on the leaf surface of plants that were used to a lower degree (82 and 10.3% of the leaf dry matter for high- and low-use plants, respectively). Several leaf surface compounds were related to period, while site and degree of use were seldom related to individual mono- and sesquiterpenes measured in this study. Camphene and 10 unidentified compounds differed between periods (P < 0.10). Two unidentified compounds were related to site (P < 0.10) and 2 others were related to use (P < 0.10). In summary, individual leaf surface compounds on tarbush do not appear to greatly affect degree of use of tarbush by livestock, but collectively (based on epicuticular wax data), these compounds may influence the diet selected by browsing ruminants.

Characterising the spatial and temporal activities of free-ranging cows from GPS data

Electronic tracking provides a unique way to document behaviour by cows on a continuous basis. Over 2 years 17 beef cows with calves were fitted with global positioning system (GPS) devices programmed to record uncorrected GPS locations at 1-s intervals in a semi-desert rangeland. Each cow was periodically observed during daylight hours and foraging, walking and stationary (standing/lying) activity times were recorded across days and individual cows to calculate a mean travel rate for each activity. Data without observers present were collected immediately preceding and following the abrupt weaning of calves at between 223 and 234 days of age to evaluate the potential of classifying various travel rates into foraging, walking and stationary activity. The three activities were further characterised within a 24-h period based on the sun’s angle with respect to the horizon. Only data from cows whose equipment acquired ≥ 90% of the potential GPS positional data among consecutive days were analysed. Due to problems with the equipment, data from two cows in 2009 and two cows in 2011 met these criteria. The interval evaluated consisted of four 24-h periods before abrupt weaning and seven 24-h periods following weaning. Results suggested that uncorrected 1-s positional GPS data are satisfactory to classify the behaviour by free-ranging beef cows into foraging, walking and stationary activities. Furthermore, abrupt weaning caused cows to change their spatial and temporal behaviour across and within days. Overall, travel by cows increased post-weaning with subtle within-day behavioural changes. Further research will be required to fully understand the biological importance of spatio-temporal behaviour to optimise cattle and landscape management goals.

EFFECTS OF ORGANIC SOLVENTS ON USE OF TARBUSH BY SHEEP

Tarbush (Flourensia cernua DC) is a native perennial shrub prevalent in many parts of the Chihuahuan Desert. Ruminants have exhibited limited use of tarbush leaves and new leaders as a forage during the summer growing season. Efforts to increase use of tarbush by lambs through spraying with various organic solvents were unsuccessful, probably because of the highly variable response. However, complete immersion of tarbush in organic solvents (acetone and ethanol) increased (P<0.01) tarbush use by ram lambs when compared to unaltered tarbush. Data suggest that removal of secondary compounds from the leaf surface of tarbush using organic solvents enhanced acceptability of tarbush to sheep.

Diet and forage intake of cattle on desert grassland range.

C8ttlc production on desert gmssl8nd nnges in southern New Mexico b8s been low, altbougb lbnited nsnrcb sbows diet nutrition8l qu8llty of cattle is l dqu8te to meet production needs dtig most se8sons. Forrrge intake drt8 8re l8cLing for cattle on desert gmssl8nd rrmges. Five esopb8ge8Histul8ted steers were used to ev8bute diet qtulity urd bot8nierl composition on desert grssI8nd mnge in southern New Mexico. Anotber 6 steers were used to collect feces to determine intake. Cattle cb8nged their diet with se8son8l8dv8nce to nuximize diet quality. Crude protein concentmtions of cattle diets were well 8bove those needed for l8ct8tion 8nd d8ily g8in during spring 8nd summer. Diet samples were bigb in neutr81 detergent fiber (668196), suggesting low energy in the forage. Low fonp intake ~8s the nmin nutrition81 cons-t identified. Even during tbe summer growing season, org8nic nutter int8ke never exceeded 1.5% of body weigbt. We specul8te low int8kes m8y b8ve resulted from bigb summer tempentures tb8t reduced glrxing time. During tbe l8te f8ll md winter, low forrge qu8lity 8ppe8rs to explain suppressed int8ke. Protein supplement8tion in l8te f8ll8nd winter, 8nd energy supplement8tion in spring, sbouid be 8dv8nt8geous. We c8ution tbrt d8t8 on diet qu8lity without infornmtion on folrge intake mry poorly describe nutrition8l st8tus of r8nge c8ttle.

Extracts of Flourensia cernua Reduce Consumption of Alfalfa Pellets by Sheep

Effects of three extracts (hexanes, ether, and ethanol) from tarbush (Flourensia cernua) on intake of alfalfa pellets by lambs were examined. Forty-five ewe lambs were fed one of five treatments for five days (randomized complete block, three lambs per block on each treatment). Treatments were alfalfa pellets (CON) or alfalfa pellets plus ethanol carrier (CAR), hexanes extract (HEX), ether extract (ETH), or ethanol extract (ETOH). Extracts were applied to alfalfa pellets at the same concentration as in an equivalent amount of tarbush (as fed basis) in experiment 1 and at 10-fold dilutions of that concentration in experiment 2. Treatments were isolated from tarbush leaves by using a sequential extraction with hexanes, diethyl ether, and 100% ethanol. Lambs received 640 g of alfalfa pellets (dry matter basis) each morning and intake was monitored during a 20-min interval. Lambs were maintained and fed alfalfa pellets (4.7% of body weight) as one group except during this interval. In experiment 1, mean intake by lambs during the 20-min interval was 361, 393, 204, 212, and 228 g for CON, CAR, HEX, ETH, and ETOH, respectively (SEM = 28.9). All three extracts decreased intake (P < 0.001) compared to CON or CAR. Intake did not differ among the three extracts (HEX, ETH, and ETOH) or between the two controls (CON and CAR). Mean intake did not differ among treatments in experiment 2 (468, 455, 389, 381, and 431 g for CON, CAR, HEX, ETH, and ETOH, respectively; SEM = 30.5; P = 0.187). Several compounds are probably responsible for the low palatability and differential use of tarbush typically exhibited by livestock.

Preliminary results from reseeding degraded Dera Ghazi Khan rangeland to improve small ruminant production in Pakistan

Thatta Leghari rangeland in the Dera Ghazi Khan district of Pakistan covers an area of 1004 ha. Its topography is undulating, soil is calcareous and low in organic matter and supports a native standing crop of mainly unpalatable herbaceous vegetation. Due to uncontrolled grazing the range has degraded from its productive potential. Between 1992 and 1993 the native range (1004 ha) was not grazed. Then in 1992 and 1993, a 600 ha area was reseeded with two introduced grasses, Gorkha (Lasiurus sindicus) and Buffel grass (Cenchrus ciliaris). Forage production on both the reseeded and native range was measured in 1992 and 1993 at the end of the growing season during October. Weather during these 2 years reflected the long term mean conditions with respect to temperature and distribution of precipitation. The reseeded area produced 10 times (4000 kg/ha) more forage than the native range (425 kg/ha) in 1992 and more than twice the forage (1250 kg/ha vs 534 kg/ha) in 1993, a year with 37 mm less total rainfall. Proximate analysis of the forage harvested in 1993 was determined for both treatments. Buffel grass was higher in crude protein (7.8%) than Gorkha (6.2%) and chimber (5.9%; Eleusine flagellifera) a native grass. The native shrub, lana (Salsola foetida) had a higher energy value, 2.7 Mcal/kg, than all of the other species. Daily goat and sheep diets consisted of 51% and 32% shrub, respectively, with grasses comprising the remainder. Forbs composed 35% of the sheep diet whereas, shrubs (51%) dominated the goat diets on the reseeded rangeland. Liveweight gain differed (p<0.05) between goats (34 g/day) and sheep (14 g/day). These preliminary results indicate that reseeding may be an important intervention for Pakistan rangeland improvement, for improving nutrition for small ruminants. # 1999 Elsevier Science B.V. All rights reserved.

The potential of laser-induced fluorescence (LIF) spectra of sheep feces to determine diet botanical composition

Laser-induced fluorescence (LIF) peaks near 470 nm (‘blue’) and 650 nm (‘red’) from sheep feces treated with chloroform (CHCl3) displayed spectral signatures that varied with diet. Fecal samples were obtained rectally over 3 days in a replicated study consisting of four diets (treatments) fed to 16 Polypay and Polypay × Rambouillet lambs (four lambs per treatment). Basal diet consisted of tobosa (Pleuraphis mutica Buckley [formally Hilaria mutica (Buckl.) Benth.] hay with 0% (control), 10%, 20% or 30% tarbush (Flourensia cernua D.C.) added on a dry matter basis. Feces were dried at 60 °C, treated with chloroform and the extract from both crushed and intact fecal material was then excited by laser input at 355 nm. Tarbush leaves gave LIF only in the blue region of the spectrum. However, tobosa hay and all fecal pellets produced a bimodal LIF spectral distribution with a lower, broader peak feature in the blue region and a narrower well defined taller feature in the red region of the spectrum. Chloroform did not exhibit fluorescence peaks between 400 nm and 800 nm. As tarbush in the diet increased, so did the magnitude of counts in the blue region of the spectrum. The LIF redblue intensity ratios appear to be more reliable than actual counts in differentiating feces of sheep fed tobosa diets containing differing amounts of tarbush. redblue ratios decreased (P < 0.05) linearly (P < 0.005) for both crushed and intact sheep fecal pellets as the tarbushtobosa ratio in the diet increased. Inconsistencies in count amplitudes and wavelengths in either one or both regions (red or blue) of the spectrum and in redblue ratios (especially on Day 3 for crushed fecal samples) are discussed in terms of sample preparation procedures and sampling days. Our results suggest that further testing of the LIF technique is warranted using diets consisting of several species.