Dairy Cattle Response to a Virtual Fence When Pasture on Offer Is Restricted to the Post-grazing Residual

Pasture-based dairy systems rely on the accurate allocation of pasture to both meet livestock requirements and maintain the growth of herbage. Currently, physical fences are used to contain livestock however they can be labor-intensive to shift and maintain. Alternatively, virtual fence (VF) systems offer flexibility and real-time control of livestock location. Pre-commercial neckbands (eShepherd®, Agersens, Melbourne, VIC) emit a warning audio tone (AT) when a cow approaches a VF boundary, paired with an electrical pulse (EP) if the cow continues forward into the exclusion zone (EZ). However, the ability of VF technology to control animal location when pasture is restricted to the previous day's residual, remains unknown. Ten non-lactating Holstein-Friesian dairy cows were trained to use a VF system for 6 days before strip grazing a 1.2 ha paddock of annual ryegrass. Over 10 days the cows grazed eight pasture allocations at a pre-grazing pasture mass of 2,324 ± 81 kg DM/ha (mean ± SE) and post-grazing pasture-mass (post-grazing residual) of 1,649 ± 48 kg/DM/ha with a front VF. The allocations had a physical backing fence that included the fresh allocation and a small area of residual to cater for any GPS drift of the front VF. On each day, with the exception of days 5 and 10, the VF was moved forward, and the cows were provided a new pasture allocation. On days 5 and 10, the VF was not shifted, and cows were only offered the previous allocation's residual pasture. The location of each animal (inclusion, buffer, and exclusion zones) and number of stimuli (AT and EP) delivered were recorded. The number of stimuli delivered between the grazing and hold-off days was similar. Cows spent 89% of time within the inclusion zone (IZ), with significant peaks observed on day 5 and 10. Distance that cows traveled into the EZ reduced across time. There was also evidence of individual variation in the number of stimuli and thus time spent in each zone. Overall, the VF system was successful in containing the dairy cows during strip grazing even when only offered the previous days post-grazing residual.

Assessing direct and residual effects of cover crops on the soybean cyst nematode, Heterodera glycines

Greenhouse experiments were conducted to determine if cover crops directly decrease population densities of the soybean cyst nematode (SCN), Heterodera glycines, and/or have residual effects on reproduction of the nematode on soybean (Glycine max). Population densities of SCN were not significantly decreased by nine cover crop plants or three cover crop mixes compared to a non-planted soil control in a repeated 60-day-long greenhouse experiment. When susceptible soybeans were grown in the soils after cover crop growth, fewer SCN females formed following three annual ryegrass (Lolium multiflorum) cultivars (Bounty, King, and RootMax), the Daikon radish (Raphanus sativus var. longipinnatus) cultivar CCS779, Kodiak mustard (Brassica juncea), and a mix containing cereal rye, crimson clover (Trifolium incarnatum), plus Daikon radish (cultivars not stated) compared to following the non-planted control. In another repeated experiment, cover crops were grown for 56 days in SCN-infested soil in the greenhouse then exposed to Iowa winter conditions for 28 days to simulate winter termination of the plants. One treatment, a cover crop mix containing Bounty annual ryegrass plus Enricher Daikon radish, had a decrease in SCN population density greater than the non-planted control at the end of the experiment. Significantly fewer SCN females formed on soybeans grown following several cover crops, including the three annual ryegrass cultivars that had the suppressive residual effects in the first experiment. In summary, there were no cover crop treatments that consistently decreased SCN population densities across experiments, and only one cover crop treatment in one experiment significantly reduced SCN population densities more than a non-planted soil control. However, there was a somewhat consistent, adverse, residual effect of cover crops on reproduction of SCN on susceptible soybeans following growth of multiple cover crops.

Allelopathic Effects of Chrysanthemoides monilifera subsp. monilifera on Lolium rigidum in Wheat Field: Implications on the Reduction of Chemical Loads in Agro-Ecosystems

Weed control through allelopathic plants is a promising approach that may minimize many of negative consequences of synthetic herbicides. We have studied potential of Chrysanthemoides monilifera subsp. monilifera (boneseed) leaf extract for controlling growth of Lolium rigidum (annual ryegrass) in wheat (Triticum aestivum) fields. Both pre-and post-emergent ryegrass-control experiments were conducted in greenhouse using field soil. Treatments such as boneseed leaf extracts (5 and 10% for pre-emergent and 10 and 20% for post-emergent experiments) alone or as a mixture combined with different strength (¼ and ½ strength) of pre-emergent (boxer gold) and post-emergent (hussar OD) herbicides were applied on pre- and post-emergent ryegrass and wheat. The findings revealed that none of the boneseed leaf extracts alone or as mixture had significant inhibitory impact on pre-emergent ryegrass compared with herbicide alone. Although we observed significant inhibitory impacts on post-emergent ryegrass with boneseed leaf extracts alone (10 and 20%) compared with control, they were negligible compared to full strength herbicides. Mixtures had significant inhibitory impact on post-emergent ryegrass compared with herbicide alone with same doses and impact increased with herbicide concentration. Despite the greater impacts by higher herbicides concentration alone, findings suggest the use of mixture of ¼-strength herbicide and 10% boneseed leaf extract was able to control ryegrass successfully than the herbicide alone without adverse impacts on wheat. This study suggests that use of boneseed leaf extract mixed with lower doses of post-emergent herbicides may be effective in controlling ryegrass with concomitant reductions in expenses and ecological health risks linked with the practice of synthetic herbicides.

Insights into soil bacterial and physicochemical properties of annual ryegrass-maize rotation (ARMR) system in southern China

The popularized application of annual ryegrass—maize rotation (ARMR) in southern China has been proposed to fully utilize the farmlands and to increase forage yield and quality. Herein, one growth cycle of ARMR was conducted and soil bacteria were analyzed by 16S rRNA sequencing for control (CK), after the preceding crop (monoculture, or mixed sowing of annual ryegrass and oat) and the successive crop (maize). Our results indicated that the α-diversity of soil bacteria was changed in the ARMR system, which was related to the activity of urease and available phosphatase. The mixed sowing of annual ryegrass and oat in preceding crop could improve the yield and quality, while it was accompanied by unbalanced soil community. With the increased sowing proportion of oat to annual ryegrass, the soil pH increased while the soil available phosphatase decreased. The ARMR system was found to benefit the soil microenvironment by increasing the beneficial soil bacteria and enzyme activity or decreasing the harmful soil bacteria. Considering the soil bacteria α-diversity index and physicochemical properties comprehensively, the recommended sowing regime is the mixed sowing of M2 (22.5 kg·hm−2 annual ryegrass with 75 kg·hm−2 oat).

PSXI-18 Nitrogen fertilization management of winter pastures for stocker cattle production

Bermudagrass is often over-seeded with a cool-season annual grass for grazing purposes. In the Gulf Coast region, summer perennials will not become dormant until there are low soil and ambient temperatures. Nitrogen fertilizer is an expensive input and its split application for winter pastures is recommended. The objective of this experiment was to evaluate the time of application of N fertilizer or its substitution with red clover as a source of N. Three treatments were evaluated in 3 consecutive years (2 replicates per year) on annual ryegrass (cv. Marshall) no-tilled planted (45 kg/ha) on Tifton-85 bermudagrass: 1) Urea in late November and mid-late January; 2) Red clover planted with annual ryegrass; 3) Urea in January only. Thirty crossbred steers (203±24 kg) were blocked by BW and randomly assigned to 1 of 6 groups. Each group were continuously stocked on 1.34 ha pastures for 90 d. Forage mass, botanical composition, and nutritive value of the pastures were determined from the time of the first N application and every 15 d thereafter. There was treatment x year interaction (P = 0.03) in botanical composition. Greater proportions (P = 0.03) of bermudagrass were present on the 2-application treatment on every sampling date until d 15 of the grazing period in Year 1 and 3. This was a result of N absorbed by bermudagrass which impacted its nutritive value (P = 0.01) although not forage production (P = 0.07). In Year 2, annual ryegrass dominated the swards due to a cold artic front in early November. Steers grazing fertilized treatments had greater gains (P = 0.04), while production per ha was greater (P = 0.03) when N was applied in January than when no N was applied. Hay production (kg DM/ha) was similar (P = 0.06) among treatments. Opportunities for improved economics of production and enhanced sustainability appear to be realistic objectives with changes in fertilization strategy.

Rapid On-Farm Testing of Resistance in Lolium rigidum to Key Pre- and Post-Emergence Herbicides

Overreliance on herbicides for weed control is conducive to the evolution of herbicide resistance. Lolium rigidum (annual ryegrass) is a species that is prone to evolve resistance to a wide range of herbicide modes of action. Rapid detection of herbicide-resistant weed populations in the field can aid farmers to optimize the use of effective herbicides for their control. The feasibility and utility of a rapid 7-d agar-based assay to reliably detect L. rigidum resistant to key pre- and post-emergence herbicides including clethodim, glyphosate, pyroxasulfone and trifluralin were investigated in three phases: correlation with traditional pot-based dose-response assays, effect of seed dormancy, and stability of herbicides in agar. Easy-to-interpret results were obtained using non-dormant seeds from susceptible and resistant populations, and resistance was detected similarly as pot-based assays. However, the test is not suitable for trifluralin because of instability in agar as measured over a 10-d period, as well as freshly-harvested seeds due to primary dormancy. This study demonstrates the utility of a portable and rapid assay that allows for on-farm testing of clethodim, glyphosate, and pyroxasulfone resistance in L. rigidum, thereby aiding the identification and implementation of effective herbicide control options.

Intake and digestibility in cattle grazing temperate grass associated with legume and/or energetic supplementation

The intercrop between grasses and legumes is an alternative to maintain and increase animal production. The study was conducted to evaluate the effect of grass-legume mixtures with or without supplementations on rumen fermentation, nutrient intake, and microbial protein synthesis. Six Holstein steers fitted with ruminal cannula were kept in a double 3 × 3 Latin square design. The treatments were: 1) oat, annual ryegrass, and supplement (GS), 2) oat, annual ryegrass, and vetch (GL), 3) oat, annual ryegrass, vetch, and supplement (GLS). Supplementation of ground maize was given daily at 11 h at 1% of body weight. Total digestible nutrient intake was higher in steers fed GS and GLS. Animals on GL ingested higher concentrations of nitrogen (N) compared to animals on GS and GLS diets. Ruminal pH and ammonia concentration were higher in GL. Grass-legume mixtures and supplements showed higher concentrations of sugar, α-amino acids, and peptides. The ruminal fermentative parameters, ruminal pH, ammonia, and sugars ranged cubically across the day. Microbial protein synthesis was similar amongst the treatments. Animals exclusively consuming temperate grass produce higher ruminal pH and ammonia concentrations. Therefore, using temperate legumes in pasture systems can be included in the cattle diet in lieu of utilizing energy supplements.