Marta D. Remmenga

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.

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.

Effects of ruminant digestion on germination of Lehmann love-grass seed

Lehmann lovegrass (Eragrostis lehmanniana Nees) seed (germination 96%, dormant 0%) was used in 4 experiments to study the potential of sheep as a dispersal agent. Five, 4-year-old, ruminally cannulated wethers were used to examine effects of ruminant digestion on seed recovery and germination. All wethers were ruminally evacuated, and rumens were cleansed and reinoculated with strained ruminal fluid. After a 21-day adaptation to pelleted alfalfa, 4 experiments were conducted. Experiment 1 was designed to test viability of Lehmann lovegrass seeds exposed to ruminal and postruminal digestion. Lehmann lovegrass seed (10 g) was dosed intra-ruminally via ruminal fistula, and total fecal collections made. Of the viable seed ruminally dosed, 37% germinated within 21 days after recovery. Also, 98 to 100% of the seed that germinated was recovered within 72 hours of dosing. Experiment 2 was designed to test the influence of ruminal microbial digestion on seed degradation and viability, using in sacco nylon bag techniques. In sacco dry matter disappearance increased linearly from 5.5% at 3 hours of incubation to 16% at 120 hours. Germination of seed was not greatly affected until after 72 hours of ruminal incubation. Experiment 3 was designed to examine the effect of mastication on viability of Lehmann lovegrass seeds. Seeds were mixed with seed-free Lehmann lovegrass straw in a proportion of 1 to 10 (seed to straw) and 10 g fed to each wether. Boli were recovered manually via ruminal fistula. Thirty five percent of the seed fed entered the rumen without damage due to mastication. Experiment 4 compared in vitro techniques and in sacco techniques used to estimate the effect of digestion on seed viability. In vitro incubation techniques yielded similar results as in sacco techniques. We conclude that ruminants are potential disseminating agents of Lehmann lovegrass seed.

Patterns of mating between two closely related ground crickets are not influenced by sympatry

Allonemobius fasciatus (De Geer) and A. socius (Scudder) (Orthoptera: Gryllidae) are small ground‐dwelling crickets that meet and hybridize, to a limited extent, in a mosaic contact zone stretching from New Jersey to at least as far west as Illinois. To determine whether short‐range signals such as visual cues, tactile stimulation, or pheromones are important in limiting gene flow between A. fasciatus and A. socius we carried out a study in the laboratory. A male or a female was placed in a cage with an A. fasciatus and A. socius individual of the opposite sex and the outcome, a conspecific or a heterospecific mating, was recorded. Overall, conspecific matings occurred more frequently than heterospecific matings. However, individuals from areas of sympatry were no more likely to mate with a conspecific than were individuals from areas of allopatry. Thus, the challenge posed by a related species has not resulted in a strengthening of positive assortative mating in these crickets.

Effects of varying levels of undegradable intake protein on endocrine and metabolic function of young post-partum beef cows.

Twelve Hereford x Angus heifers, 2.5 year, 492 +/- 17 kg (BCS = 5 +/- 0.5), were randomly assigned to one of three supplements, stratified by calving date and calf sex. Treatments consisted of a daily equivalent of: (1) low undegradable intake protein (UIP) (L: 908 g per cow per day; 36% CP, 108 g UIP), (2) middle UIP (M: 908 g per cow per day; 36% CP, 165 g UIP), and (3) high UIP (H: 908 g M + 243 g feather meal per cow per day; 46% CP, 335 g UIP). Cows were fed sudan grass hay (7.3% CP, as fed) daily at 2% BW (as fed). Supplement was individually fed twice weekly from Week 2 to Week 11 post-partum. Cow body weight (BW), backfat (BF) and rumpfat (RF) thicknesses decreased in all cows, (P < 0.05) yet did not differ among treatments (P > 0.10). There were no differences among treatments in calf BW (P > 0.10). Serum insulin, blood urea nitrogen (BUN), milk components and yield did not differ among treatments (P > 0.10). Area under the curve (AUC) for serum LH was greater (P = 0.07) in H versus L and M (809 versus 599 and 607 +/- 69 U, respectively). No differences were observed in FSH AUC or mean serum concentrations (P > 0.10). Uterine pH did not differ among treatments or between supplement versus non-supplement days (P > 0.10). Serum progesterone remained below I ng/ml for all cows indicating absence of return to estrus. Under the conditions of this study, BW, BF, RF, serum insulin, BUN, milk components, and yield, uterine pH and serum FSH were not affected by level of UIP. However, supplement containing high levels of UIP enhanced GnRH-induced LH release.

Evaluation of Corn Grain Yield and Water Use Efficiency Using Subsurface Drip Irrigation

ABSTRACT Agricultural production greatly benefits New Mexicos economy, yet without irrigation its semi-arid environment has limited production potential. Conserving and efficiently using irrigation water has become critical for sustainable agriculture in the arid and semi-arid southwestern United States. This study was conducted in 2002 and 2003 at the New Mexico State University Agricultural Science Center in Farmington, NM on a sandy loam soil (soil series Shiprock, Typic Haplargids coarse, loamy, mixed, calcareous, mesic family) to evaluate corn (Zea mays L.) grain yield and water use efficiency (WUE) under subsurface drip irrigation (SDI) with permanent bed culture. Drip tape was placed at 15, 20, 25, and 30 cm below the soil surface. Row-lengths of missing plants were measured to determine percent plant stand. Nutrient levels were monitored through soil and plant tissue sampling. Averaged over both years, highest plant stand, yield, and WUE were obtained from the 15- and 20-cm tape depths. Soil analysis indicated only slight changes in characteristics over the duration of the study. Plant tissue analysis indicated sufficient nutrient content. Ear heights were unaffected by tape depth. Utilization of permanent bed subsurface drip irrigation on sandy loam soil in northwestern New Mexico with tape depth of 15 to 20 cm below soil surface was the most efficient in terms of production and water use efficiency.

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.

Nitrogen Recovery from 15N-Labeled Green Manures: I. Recovery by Forage Sorghum and Soil One Season After Green Manure Incorporation

ABSTRACT This investigation was part of a project to evaluate green manure forage legumes as relay intercrops for sweet corn (Zea mays L.) and chile (Capsicum annuum L.) in north-central New Mexico. The study was carried out under irrigated conditions in 1994 on a Fruitland sandy loam (coarse-loamy, mixed, calcareous, mesic Typic Torriorthent) to evaluate the 15N recovery by forage sorghum (Sorghum bicolor [L.] Moench) and soil after the incorporation of 15N-labeled alfalfa (Medicago sativa L. ‘Nitro’) or hairy vetch (Vicia villosa Roth. ‘Madison’). Two application rates of alfalfa (2.7 or 4.0 Mg dry matter ha□1) or hairy vetch herbage (3.2 or 6.4 Mg dry matter ha□1), were incorporated into soil microplots. Additional treatments consisting of 56, 112, and 168 kg N ha□1 (as urea) were used to compare soil inorganic N concentrations with those released from the legumes. Nitrogen-15 recovery by sorghum tops was 16% of the 15N applied, in two harvests. Of this, 80% was recovered at the first harvest. In soil, 15N recoveries were 50 and 3% of the input at the 0–0.3 and 0.3–0.6 m depths, respectively. Maximum inorganic N concentrations were found 14 d after amendment application. At the end of the growing season, inorganic N concentrations in all treatments were essentially the same as the background (8 mg N kg□1). The low 15N recoveries by crop plus soil and inorganic N concentrations in soil at the end of the season suggest that about 12% and 35–58% of the N applied as green manure was lost from the system for alfalfa and hairy vetch, respectively.

Effects of cis-β-ocimene, cis-sabinene hydrate, and monoterpene and sesquiterpene mixtures on alfalfa pellet intake by lambs1

The transition of grasslands to shrub-dominated scrubland reduces livestock productivity and contributes to impoverished conditions for humans in arid and semiarid regions worldwide. Many shrubs that are increasing in dominance contain secondary compounds that deter browsing by herbivores. Knowledge concerning the effects of specific compounds in herbivore diets is limited but may provide useful insights into desertification. Flourensia cernua is a dominant shrub in the northern Chihuahuan Desert that contains an abundance of terpenes. Four experiments were conducted to determine the effects of terpenes on intake of alfalfa pellets by lambs. Two individual monoterpenes (cis-beta-ocimene and cis-sabinene hydrate) were examined in Exp. 1 and 2, and mixtures of monoterpenes (borneol, camphene, camphor, 1,8-cineole, limonene, myrcene, and alpha-pinene) and sesquiterpenes (beta-caryophyllene, caryophyllene oxide, alpha-copaene, and alpha-humulene) were examined in Exp. 3 and 4, respectively. Forty-five lambs (9 lambs/treatment) were individually fed treated alfalfa pellets for 20 min each morning for 5 d. Five treatments (0x, 0.5x, 1x, 2x, and 10x; multiples of the concentrations of the same terpenes in F. cernua) were applied to alfalfa pellets (637 g, DM basis) in an ethanol carrier. The experiments were preceded by a 10-d adaptation period of the lambs to untreated pellets. Except during the 20-min test, the lambs were maintained outdoors and fed untreated alfalfa pellets (total mean intake = 4.7% of BW, DM basis). Day x treatment interactions were detected (P < 0.04) in Exp. 1 and 4 because of a greater intake for 0x than for the other treatments on d 1 (Exp. 1) and a lower intake for the 10x treatment on d 1 and 2 (Exp. 4). A trend for decreased intake (g/kg of BW) as the concentration of the sesquiterpene mixture increased was observed in Exp. 3 (P = 0.093 for the linear contrast). Although there was a tendency for the sesquiterpene mixture to decrease intake, cis-beta-ocimene, cis-sabinene hydrate, and the monoterpene mixture did not appear to affect intake by lambs. Thus, sesquiterpenes may exert antiherbivory properties under certain conditions that may contribute to shrub dominance with extended periods of livestock foraging.

Effect of neuropeptide Y on GnRH-induced LH release from bovine anterior pituitary cell cultures derived from heifers in a follicular, luteal or ovariectomized state

Objectives were to determine if neuropeptide Y (NPY) had direct effects GnRH induced secretion of LH from the anterior pituitary gland, and if endogenous steroids modulated the effect of NPY. To accomplish these objectives, 15 Hereford heifers were assigned to one of three ovarian status groups: follicular, luteal, or ovariectomized. One animal from each of the three ovarian status groups was slaughtered on each of 5 days and anterior pituitary gland harvested. Anterior pituitary gland cells within ovarian status were equally distributed and randomly assigned to one of three cell culture treatments: no NPY or GnRH (control), 10 nM GnRH, or 100 nM NPY+10 nM GnRH. Anterior pituitary cell cultures were incubated with or without NPY for 4 h and further incubated for an additional 2 h with or without GnRH and supernatant collected for quantification of LH. Treatment of anterior pituitary cell cultures with GnRH or GnRH+NPY did not affect LH release in cultures obtained from follicular (S.E.=5%; P=0.58) or ovariectomized (S.E.=7%; P=0.22) heifers. Both GnRH and GnRH+NPY increased LH release from anterior pituitary cell cultures from heifers in the luteal phase (S.E.=14%; P < or = 0.05) compared to control cultures. Cultures from luteal phase heifers treated with GnRH did not differ from those treated with GnRH+NPY (P=0.34). These data provide evidence to suggest that effects of NPY on LH release may occur primarily at the level of the hypothalamus.