Training Livestock to Eat Weeds in the Tropical Pacific and Evaluating the Effects on Meat Quality for Stronger Ranch Profits

Training Livestock to Eat Weeds in the Tropical Pacific and Evaluating the Effects on Meat Quality for Stronger Ranch Profits

Summary

The purpose of this university-ranch collaborative demonstration project is to evaluate a North American-developed approach to training livestock to eat pasture weeds in a tropical environment. Training cattle, sheep and goats to eat previously avoided pasture weeds at least briefly in a test pen has, by and large, been successful at four ranches. Larger impacts on weeds or animals remain to be seen. Most sites showed modest changes in weed and dominant species cover or density to date. Several sites have low stocking densities and weed populations are patchy. Under these conditions, it has been difficult to tell if the lack of weed patch expansion has been due to grazing pressure or simply competition with dominant pasture species.

Logistics of coordinating sampling across three islands amid scheduling conflicts with other ranch priorities proved more difficult than already anticipated. Based on the data already collected, it would appear sampling on a less frequent schedule would not result in a major loss of information pertinent to project objectives.

We propose modifying long-term monitoring from a quarterly to twice annual basis. Monitoring on this schedule will be more feasible without endangering a significant loss of data informing our objectives. We also propose modifying our original proposed activities to include at least one intensively managed trial. Impacts on weeds would be monitored by photograph until project end. Budget savings from a less intensive monitoring schedule on the long-term sites will cover any additional costs. These modifications will help better meet project objectives while remaining within budget.

Objectives/Performance Targets

Objective 1: Trained cattle, sheep and goats will consume unfamiliar foods.

Since project start, cattle have been trained and observed to eat Schizachyrium condensatum (Jurassic Kahili Ranch – Kauai; Figure 1), Sphagneticola trilobata (Rocking W Ranch – Kauai; Figure 2), Amaranthus spinosa (Haleakala Ranch – Maui) and Leonotis nepetifolia (Haleakala Ranch; Figure 3). Goats have been trained to eat Asclepias physocarpa (Haleakala Ranch) and S. trilobata (Tom’s Goats – Kauai; Figure 4) but were only observed to eat the latter. Sheep were trained and observed to eat Elephantopus mollis (Jurassic Kahili Ranch) and L. nepetifolia (Haleakala Ranch).

Objective 2: Livestock offered a free-choice diet supplement of tannins, terpenes, protein and energy will be able to consume weeds with high levels of secondary compounds.

Kapapala Ranch (Hawaii Island) – This approach, offering a supplement such as a granular from of condensed tannins that may attenuate plant secondary compounds, was considered for controlling Senna occidentalis on the ranch. However, literature reviews revealed this Senna species to be highly toxic to cattle and goats. Given the success of goats controlling the other target weeds, we decided to drop this plant from consideration. With the exception of A. physocarpa, this approach has not been necessary for any of the other weeds attempted. Principal Investigators will consult with ranch collaborators to determine if they would like to use this approach to target A. physocarpa or other weeds this year.

Objective 3: Targeted weed populations will decrease with increasing grazing pressure from trained livestock.

Pasture monitoring sites were successfully established at Kapapala Ranch (Hawaii), Jurassic Kahili Ranch (Kauai) and Rocking W Ranch (Kauai). Both Haleakala Ranch and Tom’s Goats were forced to remove trained animals from areas making long-term monitoring sites unfeasible.

Objective 4: Effects of consuming weeds on meat quality will not be detectable.

To meet this objective, we will collect and test meat samples of trained animals by the end of this year.

• Figure 2. Heifers at Rocking W Ranch eating S. trilobata during the training process.
• Figure 3. Haleakala Ranch heifer eating L. nepetifolia in the test pasture following training period.
• Figure 4. Goats eating S. trilobata in test pens at Tom’s Goats.
• Figure 1. Cattle eating S. condensatum in the test pen at Jurassic Kahili Ranch during the conditioned preference training process.

Accomplishments/Milestones

Objective 1

Haleakala Ranch – While our training efforts, as noted in the Interim Report dated February 2012, resulted in cattle successfully eating spiny amaranth, the weed areas dramatically increased in cover to nearly 100% by June 2012. Ranch managers were thus forced to take more aggressive weed management actions on that particular site. Ranch managers decided to focus on another pasture weed for training livestock to eat: Leonotis nepetifolia (common names: lion’s ears, Christmas candlestick). Starting on June 25, 18 weaned calves and 50 weaned lambs were trained with the same methodology as previously reported. Both species readily ate L. nepetifolia by the end of the training period both out of the tubs and in the test pasture. An interesting side note is that on the third day of training, three lambs ate all parts of a lone Asclepias physocarpa (balloon plant) bush in the training pasture (Figure 5). This pasture weed had not been introduced to the animals in the tubs. Ranch manager Greg Friel said he had never seen sheep or goats eat all of the plant (goats will eat the fruit only), and despite training, goats did not successfully adopt eating A. physocarpa beyond fruits. Due to severe drought, the sheep were removed from Haleakala Ranch for several months and sent to another ranch in a different region of Maui. When the sheep are reintroduced to Haleakala Ranch, monitoring plots will be established to measure any effects on L. nepetifolia and possibly A. physocarpa populations under the ranch’s regular grazing management regime.

Objective 3

Kapapala Ranch – Ranch managers identified Psidium guajava (guava) and Myrica faya (firetree, fire bush) as weeds to target with goats. Three belt transects at each of four sites (two sites per target species) were established to estimate shrub density per hectare. Data were collected separately according to size class and live or dead. Very few dead individuals were recorded over the first year of data collection. Figure 6 illustrates the stable trend in P. guajava, and Figure 7 summarizes the also stable trend in M. faya.

Rocking W Ranch – Ranch managers selected Sphagneticola trilobata (wedelia) for control with conditioned preference training of cattle. Three 50 meter long line-point transects were established at each of four sites with S. trilobata present. S. trilobata, a strongly stoloniferous and rhizomatous forb, can form dense, monotypic stands after establishment. While S. trilobata cover is currently low, the four sites were chosen to monitor the rate of increase or if it is kept in check. Figure 8 shows percent S. trilobata cover remained low compared to species dominating the site.

Jurassic Kahili Ranch – Ranch managers identified Schizachyrium condensatum (bushy beard grass) to be controlled with cattle and Elephantopus mollis (soft elephantsfoot) to be controlled with sheep. Four monitoring sites (two sites per target weed species) were established using the same line-point transect method to estimate percent cover. S. condensatum is a perennial bunchgrass of very poor forage quality and palatability to cattle and sheep that can form monotypic stands. E. mollis tends to form dense patches in sod-forming forage types. Like S. trilobata sites at Rocking W, the monitoring sites were chosen in areas with currently low cover to note any increase. Figure 9 shows both species’ cover remained low during the study period to date.

• Figure 8. Mean percent S. trilobata cover (green line) across four sites at Rocking W Ranch, Kauai. S. trilobata cover remained low relative to dominant species Panicum maximum (red line) and Paspalum conjugatum (blue line).
• Figure 9. Mean S. condensatum cover (blue lines; JKR 1 and JKR 2) and mean E. mollis cover (green lines; JKR 3 and JKR 4). Neither target weed showed an increase in cover over the year.
• Figure 5. Sheep being trained to eat L. nepetifolia voluntarily ate A. physocarpa, another problem weed at Haleakala Ranch.
• Figure 6. Mean guava density (individuals per hectare) at two sites at Kapapala Ranch, Hawaii Island. Size classes: A – individuals below 0.5 m tall, B – individuals between 0.5 – 1.0 m tall, C – individuals above 1.0 m tall. Bars indicate standard error of the mean.
• Figure 7. Mean M. faya density (individuals per hectare) at two sites at Kapapala Ranch, Hawaii Island. Size classes: A – individuals below 0.5 m tall, B – individuals between 0.5 – 1.0 m tall, C – individuals above 1.0 m tall. Bars indicate standard error of the mean.

Impacts and Contributions/Outcomes

Thus far, training cattle, sheep and goats to eat previously avoided pasture weeds at least briefly in a test pen has, by and large, been successful at four ranches. Ranchers were able to incorporate the conditioned preference training method without significantly disrupting regular grazing practices. Each collaborating ranch has so far been impressed with the success of seeing trained animals eating targeted weeds at all. Larger impacts on weeds or animals remain to be seen. Analysis of blood samples drawn before and after the trainings of Jurassic Kahili Ranch cattle, Rocking W Ranch cattle and Tom’s Goats goats revealed no alarming trends related to the training process itself.

Most sites showed modest changes in weed and dominant species cover or density to date. Targeted weeds, while noticeably present on each site, were generally recorded as having low cover or density at project start. With some exceptions, most livestock are rather extensively managed. In other words, several sites have low stocking densities and weed populations are patchy. Under these conditions, it has been difficult to tell if the lack of weed patch expansion has been due to grazing pressure or simply competition with dominant pasture species.

The originally proposed quarterly monitoring of pasture sites was informative in the first year. However, logistics of coordinating sampling across three islands amid scheduling conflicts with other ranch priorities proved more difficult than already anticipated. Based on the data already collected, it would appear sampling on a less frequent schedule would not result in a major loss of information pertinent to project objectives.

We propose monitoring the three long-term sites on a twice annual basis (once in dry season and once in wet season) until project end. Monitoring on this schedule will be more feasible without endangering a significant loss of data informing our objectives. As a strategy towards controlling weeds, we are more interested in longer term trends than dynamics within the year. We also propose modifying our original proposed activities to include at least one more intensively managed trial. In other words, we would like to attempt increasing stocking density, with temporary fencing if necessary, and/or grazing frequency on sites with target weeds. Impacts on weeds would be monitored by photograph until project end. Budget savings from a less intensive monitoring schedule on the long-term sites will cover any additional costs. These modifications will help better meet project objectives while remaining within budget. Furthermore, to meet Objective 4, intensively managing livestock trained on target weeds will help ensure they are actually eating the weeds prior to slaughter and data collection.

Collaborators: