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

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

Haleakala Ranch – Initial training efforts in October 2011 resulted in a mix of 80 steers and heifers successfully eating A. spinosus in a roughly 10 hectare infested paddock as part of a grazing rotation (Figure 2). However, the weed areas dramatically increased in cover by June 2012. Ranch managers were thus forced to take more aggressive weed management actions on that particular site. At the same time, 20 goats were trained targeting the base of A. phsyocarpa as literature indicated this part of the plant has the least amount of secondary compounds. Goats did not increase intake of A. physocarpa during or after training. Ranch managers decided to focus on L. nepetifolia instead. In June 2012, 18 weaned calves and 50 weaned lambs were trained with the same methodology as reported above. Both species readily ate L. nepetifolia by the end of the training period, both out of the tubs and in the test pasture (Figure 3). An interesting side note is that on the third day of training, three lambs completely defoliated a lone A. physocarpa bush in the training pasture (Figure 4). 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 the 2011 trainin,g goats did not successfully adopt eating A. physocarpa beyond fruits. Due to severe drought by fall 2012, the sheep were removed from Haleakala Ranch for several months and sent to another ranch in a different region of Maui. Monitoring plots thus became futile lacking any treatment.

Kapapala Ranch – Between drafting the project proposal and visiting the ranch to conduct the project in October 2011, ranch managers were able to get grazing pressure on the initial weeds of concern without specialized training. However, all classes of animals on the ranch avoided S. occidentalis, and managers were interested in targeting this weed for control with livestock. On researching this genus, we felt reported toxicity to be a concern and did not conduct the training onto this plant. We considered testing this plant for Objective 2, offering supplements to attenuate plant toxins; however, discussion between Co-PIs and ranch managers led to the conclusion that this plant posed too much risk to the welfare of the animals. Therefore, vegetation monitoring sites were established to observe goat browsing impacts on Psidium guajava L. and Morella faya (Aiton) Wilbur, which are management priorities of the ranch.

Rocking W Ranch – The principal investigator conducted the training program with nine heifers in November 2011 (Figure 5). The target weed was S. trilobata, and animals ate S. trilobata during the training and in the training pasture.

Jurassic Kahili Ranch – In December 2011, the principal investigator conducted the training program with 10 heifers to train them onto S. condensatum. They successfully ate the weed in the trial pen. Cattle were kept in a dry lot for the duration of the seven-day training with the majority of their daily diet coming from commercial feed. Unfamiliar feeds and target weeds were fed as a small supplement as described in methods. Pasture intake of S. condensatum by these cattle was difficult to observe as the ranch regularly mows this weed to delay or prevent flowering. Informal and monitoring observations did not indicate a noticeable decline in S. condensatum over the study period.

We also trained 18 adult ewes and rams onto E. mollis at the same time as the heifers but in a separate temporary training paddock set up with electric net fence. The sheep were observed to eat the flowers only before the training period. However, with the training, sheep readily ate all parts of the plant in the training paddock. Both in informal observation and in the vegetation monitoring data reported below, E. mollis appeared to decline from pastures. While this could be from an environmental or other reason, given the degree of intake in test pens there is a good possibility the decline could be from grazing pressure. Sheep stocking density is low on the ranch, so if the decline is from grazing pressure this would indicate high selectivity for E. mollis by these sheep (Figure 6). Future studies should examine this further.

Tom’s Goats, Kauai – The principal investigator trained 15 does onto S. trilobata in a pen in December 2011 (Figure 7). Goats were given a daily ration of P. maximum from the neighboring paddock where their herd mates were grazing. After the training period, the goats readily ate S. trilobata in the pen despite avoiding it in normal rotation. Unfortunately, owing to land tenure issues, these goats were removed from this site and dispersed among other herds before in-pasture use of S. trilobata could be observed.

Animal Health – Blood was collected from representative animals on three ranches before the training and within three days of eating target weeds. Blood was sent to Antech Diagnostics (Irvine, CA) for general analysis primarily for blood urea nitrogen (BUN) as an indicator of kidney or liver distress due to toxicity. None of the ten heifers at Jurassic Kahili Ranch, nine heifers at Rocking W Ranch, or ten goats from Tom’s Goats showed dramatic increased or decreased levels of concern between sampling periods.

Objective 2: Livestock offered a free choice diet supplement will be able to consume weeds with high levels of secondary compounds.

Kapapala Ranch – As noted above, this additional step in the conditioned preference training method was considered for use on S. occidentalis. However, this plant was dropped from consideration out of an abundance of caution arising from reports of acute toxicity in multiple livestock species.

Haleakala Ranch – Based on previous experience from this project, ranch managers modified the training method described above to shorten the period to three days and used grain as both an energy supplement and positive experience for the animal in eating something new. In September 2013, three heifers, 10 sheep (mixed sex), and 10 goats (mixed sex) were penned and fed grain together as part of a separate bonding project. P. americana leaves were also introduced when the animals were fed (Figure 8). The Merck Veterinary Manual lists P. americana as toxic to livestock; however, these animals had free access to pasture as well as the energy supplement and could mix their diet possibly minimizing adverse effects. Informal observation revealed that all species preferred to eat leaves when first let into the pasture containing the tree before switching to grass. All species ate old leaves, fresh leaves, and fruits with no apparent toxicity issues.

In another variant of the livestock training, in December 2013 we used straight molasses as an energy supplement and enticement for this group to eat L. nepetifolia. The above mixed group of livestock was put on a small three-acre paddock. Each afternoon for three days they were offered a supplement of L. nepetifolia drizzled with approximately a pint of molasses (Figure 9). Livestock ate most of the plants offered in the trough, and initial photo monitoring and inspection showed they ate it in the pasture without any molasses added.

The molasses approach was also used to train cattle to increase intake of D. insularis. This grass is usually left untouched by cattle in a rotational grazing system. Four hundred cows and heifers were let into a three-acre paddock heavily infested with D. insularis that had been partially sprayed with a diluted molasses mixture. After 12 hours the cattle were moved out with significant use on this grass in both sprayed and unsprayed areas (Figure 10). Increasing stock density while offering an energy supplement appears to increase intake of D. insularis in cattle. This method also increased intake of another group of 100 head in a 20-acre paddock with small patches of this grass. Cattle ate patches of both sprayed and unsprayed D. insularis where previously none would be eaten. The increased intake of unsprayed D. insularis may result from simply overcoming neophobia or this in combination with increased energy status to deal with potential plant secondary compounds.

As all other conditioned preference training sessions besides A. phsyocarpa showed marked increased intake, additional supplementation was not deemed necessary. A. physocarpa was abandoned as a management priority by ranch managers at this time as goats will eat the fruits and other weeds showed more promise for this method. A. physocarpa may be identified in future projects for increasing intake with energy or toxin attenuating supplements.

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

Kapapala Ranch – Figures 11, 12, and 13 show very little change in P. guajava and M. faya densities at the Kapapala sites. Both sites were only browsed twice during the study period owing to changes in grazing management due to unprecedented drought. Stocking density was approximately 500 adult goats on two-acres. While only grazed twice in three years, individual trees showed significant damage to bark and branches within reach of goats for duration of project period. Several M. faya bushes showed signs of limited or light browsing. Goats were moved to new paddocks every other day, so prolonging the grazing period at this density may lead to heavier use of M. faya (Figure 14). Dead individuals were also counted but, as numbers were trace, they are not reported here.

Rocking W Ranch – Ranch managers selected S. trilobata for control with conditioned preference training of cattle. S. trilobata, a strongly stoloniferous and rhizomatous forb, can form dense stands between grass tufts after establishment suppressing desirable forages. While Figure 15 shows low relative cover of S. trilobata according to line point data, the weed was present in much of the interspaces. Ranch managers were more concerned about its increase rather than its current extent (Figure 16).

Jurassic Kahili Ranch – Ranch managers identified S. condensatum to be controlled with cattle and E. mollis to be controlled with sheep. 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 17 shows both species’ cover remained low during the study period.

Tom’s Goats – Photo-monitoring plots were set up at the initial training site in December 2011. However, owing to shifting ranch priorities and difficulties with the land lease, the trained group of goats were moved and dispersed among other herds. Furthermore, ranch ownership changed in 2013, ultimately resulting in herd liquidation. Therefore, the PI could not follow long-term impacts of this conditioned training program at this ranch.

Objective 4: Effects of consuming weeds on meat quality will be detectable.

Several factors combined to make pursuit of this objective untenable. Chiefly, periodic in-field observations of trained animals by ranch managers and the PI as well as the vegetation monitoring plots showed only incidental intake of target weeds over the project period. While increasing stocking density increased weed intake, these were short and infrequent periods over the life of the animal. Therefore, the lack of treatment effect could not justify resources spent on meat chemical and flavor analysis. Furthermore, slaughterhouse practices made identification of carcasses from trained animals uncertain. In some cases, heifers originally intended for market were retained in the breeding herd.

Meat analysis and travel costs were the largest budget items for this project. The elimination of meat analysis as an objective, a less frequent vegetation monitoring protocol, and lodging provided by ranches resulted in significant cost savings to the project unanticipated at project start. These cost savings resulted in the project coming in well under budget without a loss of data in three of the four main objectives.

• Figure 8. In a rancher adapted variant of the training methodology, heifers, sheep, and goats were given a grain energy supplement from tubs over three days. On Day 3, P. americana leaves were introduced to tubs. Despite being reported as toxic, each type of livestock readily ate fresh P. americana leaves offered in the paddock containing the tree which had a browse line.
• Figure 16. Representative Rocking W Ranch monitoring transects in 2011 (top) through the end of project (bottom) showed little change in S. trilobata cover.
• Figure 11. Mean P. guajava density at Kapapala Ranch with two goat browsing periods during study. 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 12. Mean M. faya density at Kapapala Ranch with two goat browsing periods during study. 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 13. Representative photos of one M. faya transect in 2011 (top) and 2013 (bottom). We observed very little change in brush cover despite intense grazing by ~500 goats twice over the study period.
• Figure 14. Morella faya following intense grazing over 2 days. Prolonging the grazing period may lead to more intake by goats.
• Figure 2. October 2011 training round at Haleakala Ranch for A. spinosus. Clockwise from top-left: Prepping supplement feed tubs; Leftovers from Day 6 – A. spinosus mixed with wheat mill run; A. spinosus eaten in training paddock; Heifer eating A. spinosus from tub on Day 7 of training.
• Figure 5. November 2011 conditioned preference training with 9 entirely pasture raised heifers at Rocking W Ranch, Kauai. Clockwise from top-left: S. trilobata mixed with alfalfa pellets on Day 6 of training; Heifer eating S. trilobata from training tub; S. trilobata eaten in pasture.
• Figure 6. December 2011 training at Jurassic Kahili Ranch with heifers on S. condensatum and ewes and lambs on E. mollis. Clockwise from top-left: Competition for feed space on Day 5; Extensive defoliation of E. mollis in temporary training paddock; Heifers eating S. condensatum from trough in training pen. The bulk of the heifers’ diet was from conventional feed, the target weed was a supplement.
• Figure 7. December 2011 training of does at Tom’s Goats for S. trilobata. Fifteen goats were penned and fed P. maximum from the neighboring paddock used by herd mates (left). On Day 7 of the training, goats readily ate S. trilobata offered in addition to the P. maximum offered at the same time (right).
• Figure 9. In a rancher adaptation of the conditioned preference training and energy supplementation approach, L. nepetifolia was drizzled with molasses and offered in a trough for 3 days. Livestock increased intake of L. nepetifolia in observation paddocks even though they avoided it previous to the energy supplement and trough training.
• Figure 10. In another variant of this approach at Haleakala Ranch, 400 cows and heifers were given a free choice molasses energy supplement before and during rotation into a D. insularis dominated 20-acre paddock. Before grazing, a small portion of the paddock was sprayed with diluted molasses. D. insularis before grazing (top), after 8-hours of grazing (middle), and after 12-hours of grazing (bottom).
• Figure 15. Mean percent S. trilobata cover (red line) across four sites at Rocking W Ranch, Kauai. S. trilobata cover remained low relative to dominant species Panicum maximum (blue line) and Paspalum conjugatum (green line).
• Figure 17. Mean S. condensatum cover (blue lines; JKR 1 and JKR 2) and mean E. mollis cover (red lines). Neither target weed showed an increase in cover over the project period.
• Figure 3. June 2012 conditioned preference training at Haleakala Ranch of heifers and sheep. Clockwise from top-left: Training tubs situated to encourage competition and interest; Sheep eating L. nepetifolia from training tubs on Day 7 of training; L. nepetifolia eaten in the paddock; Sheep eating L. nepetifolia in paddock on Day 6; Heifer eating L. nepetifolia in paddock on Day 6.
• Figure 4. Sheep in June 2012 eating leaves of A. physocarpa despite being trained to eat L. nepetifolia this round and the failure to train goats onto this plant the previous year.