UTILIZATION OF OPUNTIA FOR FORAGE IN THE UNITED STATES OF AMERICA

Peter FELKER

INTRODUCTION

The literature on uses of opuntia in the USA is most colourful. During the Civil War (ca 1850), freighters loaded with cotton were pulled by oxen to the only safe port of export at the southern tip of Texas (Brownsville). The route passed through extensive stands of spiny opuntias. The teamsters scorched the cactus by burning with brush, and chopped or slashed it with an axe, spade or machete to feed their oxen (Griffiths, 1905). Because of the high water content of the cactus, the oxen needed to drink water only once weekly in winter, and two to three times weekly in summer.

In the early twentieth century, pressurized, backpack “white gasoline” pear burners were used in Texas to singe the spines from opuntia so that the cattle could eat it (Pluenneke, 1990). Kerosene became available in the 1930s and replaced white gasoline. In the 1950s, butane gas became available in Texas and was then used in single-backpack pear burners and in rigs with multiple hoses, supplied by large tanks in pick-up trucks.

As early as 1905, Griffiths (1905) reported that opuntia had been succesfully fed to dairy and beef cattle, oxen, sheep and pigs (extreme care being taken to remove all the spines), but not to horses. However, Argentine farmers state that when opuntia is fed to pregnant sows, they abort. Lukefarh and Ruiz (1998) recently conducted an opuntia feeding trial with rabbits and found that the Brazilian forage variety Palma Redonda had good palatability and also supported moderate weight gains.

Public opinion concerning the value of cactus for livestock varies considerably between the regions south and northwest of San Antonio, Texas. In southern Texas, opuntia is highly regarded as an emergency feed for livestock and as a mainstay for the wildlife population. North of San Antonio, where the rainfall is lower and where Opuntia lindheimeri is less abundant, cactus is less appreciated. In this region, sheep and goats begin eating first the fruits, then the cladodes without the spines being burned off. As a result, spines and glochids become lodged in their gastrointestinal tracts and bacterial infections of the lesions may follow (Merrill et al., 1980; Migaki et al., 1969).

Spineless opuntia plantations in Texas must be very well protected against herbivores such as rabbits, rats, deer and peccaries, using a 2.4-m tall netwire fence with a 5-cm mesh band at the bottom. The adoption of portable electrical fences within these exclosures could permit stock to graze only one row of a spineless opuntia plantation at one time.

While spineless opuntia plantations require fencing, the spiny types do not. However, the spines must be singed off with a flame thrower (known as a “pear burner” in Texas) before the cladodes are fed to the livestock. Thus the flame thrower is a management tool that allows the rancher to decide when and how much of this resource to use at one time.

A study in Texas measured all the water inputs to cactus and the corresponding dry matter production (Han and Felker, 1997). Of the 662 mm of rainfall input, 143 mm was lost to runoff, 214 mm was lost to soil evaporation, and 17 mm stored in the plant. The resulting 285 mm left for growth of Opuntia ellisiana resulted in 17 670 kg of dry weight/ha for a water use efficiency of 162 kg of water/kg of dry matter. This water use efficiency is greater than that measured in the field for any C3 or C4 plant and thus emphasizes the basic physiological advantage of CAM plants in arid regions. It is also significant that the fourth-year fresh weight growth of 194 200 kg/ha contained 170 000 kg/ha of water, that would greatly reduce the water needs for livestock in drought periods. At the rate of 45 kg fresh cactus per day (discussed later), this 194 200 kg/ha would be sufficient for 4 315 days (11.8 years) of feed per cow.

NUTRITIONAL PROPERTIES AND SUPPLEMENTATION REQUIREMENTS

The nutritional quality of forage cacti can be expected to exhibit considerable variation due to the age of the plant (Gregory and Felker, 1992), the season of the year (Retamal et al., 1987b) and the fertility of the soil (Gonzalez, 1989; Gathaara et al., 1989). Despite the considerable importance of opuntia to domestic stock and wildlife, there are only a few reports of the nutritional quality of opuntia in animal diets (Griffiths and Hare, 1906; Shoop et al., 1977; De Kock, 1980; Meyer and Brown, 1985; Retamal et al., 1987a). Typical values for nutritional components in these studies were found to be: moisture content, 85-90%; crude protein, 5-12%; phosphorus, 0.08-0.18%; calcium, 4.2%; potassium, 2.3%; magnesium, 1.4%; energy, 2.6 Mcal/kg; carotenoids 29 µg/100 g; and ascorbic acid, 13 mg/100 g. The in vitro digestibility values were 72% for protein, 62% for dry matter, 43% for crude fibre and 67% for organic matter.

Another significant advantage of cactus for animal feed is that it is often the only source of green forage in the dry season capable of providing vitamin A precursors. Rodríguez-Felix and Cantwell (1988) reported 29 µg of carotenoids and 13 mg of ascorbic acid per 100 g of immature cladodes to be used as vegetables for humans.

The only metabolizable energy and digestibility data for cactus are for wild opuntias in Texas and Colorado. Everitt and González (1981) found that, of all species examined, although O. lindheimeri had one of the lowest protein contents (6%), it had the highest dry matter digestibility (76%). Meyer and Brown (1985) also found that O. lindheimeri had higher digestibility throughout the year than the other plants in their south Texas study area.

Data on digestible energy and protein content of the small, low growing O. polyacantha on the ranges of Colorado may serve as a useful guide to other opuntia forage species (Shoop et al., 1977). While this opuntia was lower in crude protein (5.3%) than grassland hay (5.7%) or alfalfa hay (16.8%), its digestible energy of 2.61 Mcal/kg, compared favourably to grassland hay (2.08 Mcal/kg) or alfalfa (2.64 Mcal/kg). O. polyacantha had 85% as much neutral detergent fibre and 70% as much as acid detergent fibre as alfalfa, but it contain 55% more hemicellulose and 40% more soluble carbohydrates (Shoop et al., 1977). As might be expected due to the faster growth and less lignification, O. ficus-indica was found to have greater digestible energy values, ranging from 3.32 to 3.54 Mcal/kg (Retamal et al., 1987b).

While the amino acid profile of the opuntia stems is only useful for non-ruminant nutrition, Teles et al. (1984) found the amino acid profile of immature opuntia stems to have a biological value of 72, compared to hen egg protein of 100.

Texas rancher Bill Maltsberger has spent many years developing protein and mineral supplements for his herd of 800 Santa Gertrudis cattle on 4 000 ha of rangeland south of San Antonio. Although Maltsberger routinely supplemented cactus with cottonseed meal as a protein supplement and allowed the cattle free range, there was subtle evidence of nutritional disorders. After considerable post-mortem testing of organs for trace elements, it was found that the cattle were low in copper, molybdenum and zinc. On the basis of these analyses, Maltsberger began using the supplements shown in Tables 22 and 23. Regular vitamin E injections have been also helpful after many months on this cactus diet. When cattle were fed cactus that had had its spines burned off (as discussed later) and were supplemented with protein cubes and mineral supplements, excellent weight gain, body conformation and 90% conception rates were achieved. This supplementation also seemed to reduce the percentage of abnormalities in newborn calves.

Maltsberger (1993, pers. comm.) stressed that the mineral deficiencies in his animals were not directly caused by the cactus, but were a result of the fact that during droughts cattle often have no other source of minerals and vitamins than cactus. Thus in drought periods, when no other significant quantities of forage are available for many months, it is critical to address the issue of lack of proteins and minerals.

The protein ration in Table 22 is formulated in the form of 2-cm cubes, and only fed during drought periods when no other forage is available. The mineral supplement in Table 23 contains phosphorus and calcium in the form of meat and bone meal that is not contained in the protein supplement. This mineral supplement is made available all year round regardless of drought status.

While the feed rations have been optimized for cattle, it is reasonable to expect that these rations could be easily adapted to other ruminants such as goats, sheep and deer. There are very old reports of cactus being fed to pigs. However, well-replicated trials feeding cactus to non-ruminants like pigs have not been conducted. Lukefahr and Ciro-Ruiz (pers. comm.) have succesfully fed an opuntia strain (#1270) from Brazil (Palma Redonda) to rabbits. It is interesting that rabbits did not like the nopalito variety O. cochellinifera #1308, but they liked Brazilian forage variety #1270.

Table 22. Protein supplement for cattle during droughts.

Source: Data courtesy Bill Maltsberger, Rancher, Cotulla, Texas.

Table 23. Mineral supplement* for cattle for cactus supplementation

Note: *The mineral supplement is fed all year long.
Source: Data courtesy of Bill Maltsberger, Rancher, Cotulla, Texas.

METHODS TO INCREASE THE PROTEIN CONTENT OF CACTUS FORAGE

Fortunately, there are several techniques to increase protein content of cactus forage to minimize the cost of protein supplementation. The first method is with N and P fertilizers, since González (1989) found that crude protein in O. lindheimeri increased from 4.5% for the zero fertility treatment to 10.5% for the treatment containing 224 kg N and 112 kg P/ha. This is especially important, since this fertilization treatment raised the protein content above the requirements for dry and lactating cattle, namely 6.0 and 9.25% respectively.

Since most commercial cactus fruit orchards receive N fertilization, it is reasonable to believe that the N content of the pads from these orchards would approach the 9% protein content level. Potgieter (1997 pers. comm.) in South Africa obtained 40 ton of pads from annual pruning of cactus fruit orchards, which could be a significant source of high protein forage for livestock.

Based on the 40 kg/ha consumption of pads per animal recommended by Maltsberger (Table 24), these annual prunings would provide approximately 3 animal-years of forage per hectare.

Table 24. Daily ration for adult cow with calf

Source: Data courtesy of Bill Maltsberger, Rancher, Cotulla, Texas.

The second route to increased protein content of cactus forage is through the use of genetic selections containing higher protein. In a comparison of eight opuntia forage clones, Gregory and Felker (1992) found one Brazilian clone (#1270, i.e. cv. Palma Redonda) from CPATSA Petrolina, Brazil, that had over 11% protein content in all four age classes. In contrast, the Texas native opuntia had high protein in the youngest age class (11%), but only 5% protein in the three older age classes. Additionally, the Brazilian clone had four times the P content (i.e. 0.41%) of the native Texas clone.

Lastly, it is also possible that inoculation of cactus roots with the free living, nitrogen-fixing bacteria Azospirillum sp. could increase the protein content of the cladodes, since Rao and Venkateswarlu (1982), Caballero-Mellado (1990) and Mascarua-Esparza et al. (1988) found this bacterium could associate with opuntia roots. While these authors did not demonstrate N fixation from the Azospirillum in association with cactus roots, Mascarua-Esparza et al. (1988) did report a 34% increase in cactus root dry weight and a 63% increase in root N content with Azospirillum inoculation. Azospirillum inoculation may also help control the rotting of cladodes caused by Erwinia sp. that is often associated with new plantings, since laboratory culture studies have shown that Azospirillum inhibited the growth of both Xanthomonas and Erwinia.

PLANTING, CULTIVATION, FERTILIZATION AND CARE

The most common problem with new cactus plantings is rot of the plant material at the surface where it was cut or broken off. Cactus cladodes should either be dried in the shade for several days to allow the cut surface to “heal over,” or the new cladodes treated with lime/copper sulphate solution to control bacterial rots. The soil should be ploughed and cultivated as for any other crop. Cladodes should be planted with about 1/3 of their height below the soil surface, with the flat cladode surface facing east-west.

During the initial growth stages, the growth of cactus can be severely retarded by grass and other herbaceous vegetation. Thus it is very important to provide good weed control until the cactus is well established. Pre-emergent herbicides, such as karmex, simazine and treflan all provide good weed control at rates of 2-4 kg/ha, without harming cactus. If no pre-emergence herbicide is available, it is essential to plant the cactus in an arrangement that permits easy and frequent mechanical weed control, such as disking. If a 2.5-m wide disk unit is available for weed control, it is recommended to plant the cactus on a 1 m × 4 m row spacing to allow easy access of the disk and tractor down the rows.

In Argentina, horses are admitted to the spineless cactus plantations as they will eat most forage but not the cactus. As discussed later, after the cacti reach a height of more than 1 m, livestock can be admitted at rates of 1 cow per hectare. At this time the cattle will consume both the grass (weeding the cactus) and the cactus, thus eliminating the need for weed control in the cactus.

Even unselected stock of the common O. lindheimeri can have high productivity with fertilization. For example, González (1989) examined eight fertilization treatments on the native O. lindheimeri over a four-year period in a zone with 430 mm/yr rainfall. The dry biomass productivity in this trial increased from 7 t/ha/year to 62 t/ha/year for the maximum N and P rate, i.e. 224 kg N and 112 kg P/ha. This productivity compares very favourably with other forage species. In addition to the increased yield, the crude protein in the cladodes increased from 4.5% to 10.5%. González (1989) recommended fertilizing cactus with 224 kg/ha N every 2 years to maintain crude protein levels at about 10%, with productivity in the 50 ton/ha/year range.

THORNLESS VERSUS THORNY CACTUS FORAGE VARIETIES

There are significant advantages to both thorny and thornless cactus varieties. Thornless varieties must be fenced to prevent cattle and wildlife from totally consuming plantings less than 2 years old. In Texas, deer, javelina (wild pigs) and rabbits will completely consume new plantings. In areas where deer are abundant, it is necessary to establish 2.2-m tall fences around the thornless cactus plantings. In contrast, thorny varieties do not have to be fenced, but the spines have to be burned off with propane torches before utilization. In Texas, by purchasing propane in large truck loads (40 000 litre/truck), it has been possible to purchase propane for US$ 0.11/litre. In a good stand of native O. lindheimeri, one man, using an 8-litre propane tank and a propane torch, can burn enough cactus to feed 100-200 head of cattle per day, using 1.0 to 1.3 litre of propane/animal (Maltsberger, 1989). To avoid overcooking the cactus, only enough flame should be used to burn the spines from both sides of the plant. Maltsberger also recommended burning more cactus than is actually needed to last until the next feeding and to not overutilize the resource, by leaving at least one joint above the ground uncooked.

To reduce the cost of burning cactus bushes at random in the wild, Pluenneke (1990) described systems in which cactus were planted in rows. In some special applications, such as the need to take cactus to the penned mother cows and calves, cactus has been harvested and transported short distances to animals. Specialized hand tools have been developed to first cut the cactus at the base and then to pitch it 1 m above head height onto a wagon or truck. In Texas, this cactus was then windrowed, the spines burned off and fed into a tractor-powered ensilage chopper. In Mexico, the spines were not burned off, but merely passed through the chopper before being fed to dairy cattle (Felker, unpub. obs.).

It would seem highly advantageous to take the principles of hand harvesting and feeding hand-cut cactus to a tractor-powered ensilage chopper and adapt them to larger-scale, mechanized operations. For example, it would be useful if a self-propelled tractor or tractor-powered ensilage harvester could be modified to harvest cactus planted in rows, chop and blow it into a wagon in the field. This chopped cactus could be most useful in either dairy or beef cattle feedlot operations in arid regions. Alternatively, it might be possible to use a heavy-duty rotary disk mower conditioned to sever and windrow cactus. After drying the cactus for several weeks, it would be useful if a modified forage harvester could move down the rows, pick up the dried cactus, chop it and blow it into a wagon.

While it takes labour to burn spines from cactus, there are some useful management options that result from burning spines from cactus. Since the cattle do not eat cactus that is not burned, burning allows control over the amount of cactus that is used per day. Additionally, cattle quickly become acquainted with the sound of the propane burner and can be drawn for up to 700 m in the brush to the sound of a propane burner. This conditioning to the sound of the propane burner allows cattle to be drawn into corrals and pens.

Thornless cactus varieties offer the advantage of not having to burn off the spines, but intensive management of domestic stock and wildlife is necessary to keep the cactus resource from being overutilized. As the thornless opuntia varieties are not as cold hardy as spiny forms, such as O. lindheimeri, care must be taken in selecting suitable planting stock of spineless cactus forage varieties.

If freezing water is not a concern (minimum temperatures no lower than -5°C for a few hours), the Brazilian forage variety #1270 is specially promising as it was found to have rapid growth and nearly 10% crude protein versus 6 to 9% protein for other varieties (Gregory and Felker, 1992). A spineless variety (accession #1233), that is possibly a hybrid between the Texas native O. lindheimeri and some O. ficus-indica type, suffers only minor damage from temperatures as low as -12°C, whereas -12°C causes complete mortality to accession #1270. This accession #1233 is almost as fast growing as Brazilian clone #1270. In areas where extended temperatures of -18°C routinely occur, the only spineless type available that is cold hardy is the slow growing O. ellisiana. On a 1.2 × 1.2 m spacing, with good care, this selection will only produce 1 600 kg DM/ha the first year and 4 400 kg DM/ha the second year. However, after it reaches a leaf area index of about 1, some 11 000 kg DM/ha was produced in the third year, and 17 670 kg DM/ha in the fourth year.

Given yearly fresh weight production rates in excess of 100 000 kg/ha after a leaf area index of 2 have been achieved, and cattle consumption rates of 40 kg/day, it would appear that at a stocking rate of 1 cow/ha, livestock could never consume cactus faster than it grows. Thus it would seem possible to plant, cultivate and care for cactus until it is about 1 m in height.

COMPARISON OF CACTUS WITH HAY

Spiny or spineless cactus has been compared by farmers to “hay in the barn,” with up to 200 ton/ha of fresh weight. Several hectares of cactus can provide a considerable reserve of animal feed during drought periods. Unlike hay stored in the barn, the cactus in the fields does not deteriorate in quality with storage and there are no problems with rats eating the hay in storage. Even during drought periods in the summer or winter, cactus is green, with vitamin A and only needs to have the spines burned off or cattle admitted to the fenced area. In drought periods, cattle have to walk long distances to get water. If they are supplemented at one location by the rancher they must walk to this location every day. By consuming 40 kg of cactus per day - containing about 85% water - cattle are also consuming 35 litres of water per day, which can be beneficial in drought periods.

CONCLUSIONS

Either spiny or spineless opuntia clones, when planted in rows, fertilized and weeded, can achieve annual dry matter and fresh weight yields of 17 000 kg/ha and 170 000 kg/ha respectively, with crude protein concentrations of about 10%. When properly supplemented with protein, trace elements and critical vitamins, excellent growth and conception rates are possible. Opuntia has great potential for increasing production in average rainfall years, and to provide a critical reserve of forage for animals in severe drought years. In droughts, cactus can also provide a source of green forage and a much appreciated source of water for livestock.