CATI - Use of Kenaf As a Forage Supplement for Grazing Beef Cattle

San Joaquin Experimental Range

Research Bulletin

Use of Kenaf As a Forage Supplement for Grazing Beef Cattle
by
Randy C. Perry and Dennis E. Jones

CATI Publication #970103
© Copyright January 1997, all rights reserved

INTRODUCTION

The soils on the west side of the central San Joaquin Valley in California have problems with extremely high levels of soil salinity and a shallow water table. It has been estimated that unless a remedy is found to lower the water table and thereby reduce soil salinity, 500,000 acres of land may go out of production by the year 2040 (Westlands Water District Report, 1989). Consequently, farmers and researchers are searching for plants that can tolerate these conditions and grow in these saline soils with a shallow water table.

Plants that grow in these areas remove salt and other minerals, including selenium, from the soil, and these minerals accumulate in the plant. In order to decrease soil salinity, these plants must be harvested and removed from the area. This is the aspect that offers promise for livestock producers, because cattle grazing foothill rangeland in many central California counties are typically consuming a diet that is deficient in selenium.

Selenium deficiency can cause many reproductive disorders such as retained placenta; infertility; abortion; birth of premature, weak or dead calves; and cystic ovaries (Smart et al., 1981; McDowell et al., 1983; Pugh et al., 1985). Research conducted at the San Joaquin Experimental Range (SJER) has shown that even though blood selenium levels are well below the recognized adequate levels of 0.10 parts per million, cows have not exhibited many of the symptoms that are reported to be associated with selenium deficiency (Frost et al., 1990; Jones et al., 1991).

Starting in the late 1980s, researchers at SJER performed multiple trials evaluating the effectiveness of feeding atriplex (Atriplex canescens). This plant is highly salt tolerant and removes substantial quantities of salts and other minerals from the soil. Results of these studies indicate that blood selenium levels in cattle were moderately increased by supplemental feeding of atriplex (Frost et al., 1990; Jones et al., 1991). However, other problems existed with atriplex which prevented it from being grown in this area. Thus researchers searched for other salt tolerant plants.

Kenaf (Hibiscus cannabinus) is a plant that is moderately salt tolerant and can be grown in soils with a shallow water table. It has been shown to be effective in removing substantial amounts of salts and other minerals, including selenium, from the soil (Bhangoo and Fernandez, 1991). In addition, it appears to be a higher quality feedstuff as compared to atriplex. The protein content of kenaf is comparable to that of alfalfa (Suriyajantratong et al., 1973; Phillips et al., 1990). It is highly palatable when fed to animals in confinement (Phillips et al., 1989, 1990), and the dry matter digestibility of kenaf is comparable to that of alfalfa hay (Suriyajantratong et al., 1973; Swingle et al., 1978).

The objectives of these trials were 1) to determine the comparative feeding value of kenaf versus a typical supplement as related to their effects on performance and reproductive performance when fed to beef cows grazing annual rangeland; and 2) to determine the effects of feeding kenaf on the blood selenium content of beef cows. During a three-year period, four trials were conducted to evaluate the feed value of kenaf. Following is a summary of those four trials.

MATERIALS AND METHODS

Trial 1. During the fall of 1992, twenty-six crossbred beef cows were randomly allotted into two treatment groups. One group of cows (13 head) was supplemented with kenaf at a rate of 15 lbs./head/day, and the control cows (13 head) received oat hay at a similar rate. During the supplemental period (102 days), both groups of cows grazed pastures with similar amounts of native forage, and cows received no other supplemental feed besides the kenaf and oat hay.

At the beginning and end of the treatment or supplemental period, cows were weighed, scored for body condition (scale = 1 to 9; 1 = emaciated, 9 = obese) by two independent evaluators and blood samples were collected for determination of blood selenium content. Ten days prior to and on the first day of the breeding season (last day of the treatment period) cows were bled for determination of serum progesterone content in order to determine the number of cows cycling.

All cows were exposed to a synchronized artificial insemination period prior to being exposed to bulls during a natural breeding period of 73 days. Following the breeding season, pregnancy was determined using ultrasonography per rectum.

Trial 2. During the fall of 1993, thirty-five crossbred beef cows were randomly allotted into two treatment groups. One group of cows (15 head) was supplemented with kenaf, and the control cows (20 head) received oat hay. During the supplemental period, both groups of cows grazed pastures with similar amounts of native forage and cows received no other supplemental feed besides the kenaf and oat hay. The supplemental period was broken into three phases to compensate for depletion of native forage. During the first phase (17 days), both groups received approximately 3.5 lbs./head/day of their respective supplement. During the second phase (26 days), the two groups received approximately 7 lbs./head/day of their respective supplement. And during the final phase (35 days), both groups received approximately 10 lbs./head/day of their respective supplement.

Body condition scoring and collection of blood to determine selenium content were performed as in Trial 1. Procedures used for the collection of serum progesterone samples for determination of cyclicity were slightly different than those used in Trial 1. Five days after the start of the synchronized artificial breeding period, blood samples were collected from cows that had not yet been observed in heat and inseminated. Eight days later, a second blood sample was collected from the cows still not observed in heat or inseminated during the synchronized breeding period.

All cows were exposed to a synchronized artificial insemination period prior to being exposed to bulls during a natural breeding period of 54 days. Following the breeding season, pregnancy was determined using ultrasonography per rectum.

Trial 3. During the fall of 1994, thirty-five crossbred beef cows were randomly allotted into two treatment groups. One treatment group of cows (15 head) was supplemented with kenaf at a rate of 5.3 lbs./head/day, and the control cows (20 head) received alfalfa hay at a rate of 4.3 lbs./head/day. Although kenaf was offered at a higher rate than alfalfa, approximately 20 percent of the kenaf was not consumed, and therefore the consumption of kenaf was approximately 4.2 lbs./head/day. During the supplemental period (90 days), both groups of cows grazed pastures with similar amounts of native forage, and cows received no other supplemental feed besides the kenaf and alfalfa hay.

Body condition scoring and collection of blood to determine selenium content were performed as in Trial 1. Serum progesterone samples for determination of cyclicity were not collected but rather cyclicity at the start of the breeding season was evaluated from cows response to estrous synchronization. All cows were exposed to a synchronized artificial insemination period of 10 days prior to being exposed to bulls during a natural breeding period of 54 days. Following the breeding season, pregnancy was determined using ultrasonography per rectum.

Trial 4. Four crossbred steers were used to determine daily dry matter intake of kenaf and alfalfa hays. Both kenaf and alfalfa hays were coarsely ground prior to feeding. The trial was duplicated with each steer being switched to the other treatment resulting in a total of eight observations. During a seven-day adaptation period, feed consumption was monitored. The steers were given approximately 120 percent of this intake during the subsequent seven-day trial period to ensure ad libitum intake. Daily weights and samples of feed offered and refused were taken. After the first trial period, steers were switched to the other treatment and exposed to another seven-day adaptation and seven-day trial period. Feed samples were dried to determine dry matter intake.

RESULTS AND DISCUSSION

Consumption. In Trials 1 and 2, cows readily consumed the baled kenaf at the rates fed. However, in Trial 3, cows did not consume the kenaf at the rate offered. These differences were possibly related to very little precipitation before and during the supplemental period in Trials 1 and 2. Therefore, the only native forage that was available was dry, mature forage which is not highly palatable. However, in Trial 3, there was considerable precipitation during the supplemental period and the cows had much more fresh, green forage available. Perhaps cows did not consume all the kenaf because this lush, green, native forage was more palatable than the baled kenaf.

These observations would indicate that if kenaf is going to be used as a cattle supplement, then it must be fed to cattle not having highly palatable feedstuffs available. Otherwise, problems with palatability and consumption may be encountered.

Results from Trial 4 are presented in Table 2 and support the findings observed with the cows in the supplementation trials (Trials 1, 2 and 3). Steers consumed less kenaf as compared to alfalfa hay, regardless of whether intake was evaluated in terms of the amount they consumed or as a percent of body weight. These results contradict earlier findings (Phillips et al., 1989, 1990) which indicated that kenaf was comparable to alfalfa in terms of dry matter consumption and palatability.

Table 2. Dry Matter Intake of Kenaf and Alfalfa Hay
                                Treatment Group
Characteristic                  Kenaf   Alfalfa     Treatment Effects

Dry Matter Intake (lbs./head/day)  10.5      17.9            .0023

Intake as % of body weight         1.8%      3.0%            .0003
Body Weight. Changes in body weight are presented in Table 1. In all three trials, all cows lost a considerable amount of weight during the supplemental period. However, this was expected in as much as all cows calved after the initial weights and prior to the ending weights being recorded.

In Trial 2, control cows lost more (P=.003) weight during the supplemental period as compared to cows receiving kenaf. However, when considering weight changes in all three trials, both kenaf and the control hays were similar in terms of their effects on weight changes during the feeding period.

Table 1. Effects of Supplemental Feeding of Kenaf
                                   Treatment Group   
Characteristic                  Kenaf         Control     Treatment Effects^a

Number of head
Trial 1                          13             13
Trial 2                          15             17
Trial 3                          15             20

Weight Change^b
Trial 1                        -84 � 12      -100 � 12           NS
Trial 2                       -143 � 11      -195 � 11         .003
Trial 3                       -162 � 13      -179 � 12           NS

Initial Body Condition Score^c
Trial 1                       5.6 � .2       5.9 � .2            NS
Trial 2                       5.7 � .1       5.5 � .1            NS
Trial 3                       6.4 � .1       6.5 � .1            NS

Final Body Condition Score^c
Trial 1                       5.0 � .2       5.7 � .2          .007
Trial 2                       5.4 � .1       5.2 � .1            NS
Trial 3                       5.5 � .1       5.6 � .1            NS

Change in Body Condition Score^c
Trial 1                       -.6 � .1       -.2 � .1          .006
Trial 2                       -.3 � .1       -.3 � .1            NS
Trial 3                       -.9 � .1       -.9 � .1            NS

Initial Blood Selenium^d
Trial 1                      .029 � .002    .025 � .002          NS
Trial 2                      .028 � .003    .022 � .004          NS
Trial 3                      .036 � .004    .043 � .004          NS

Final Blood Selenium^d
Trial 1                      .078 � .005    .028 � .005       .0001
Trial 2                      .088 � .005    .031 � .006       .0001
Trial 3                      .053 � .004    .047 � .004          NS

Change in Blood Selenium^d
Trial 1                     +.049 � .005   +.004 � .005       .0001
Trial 2                     +.061 � .005   +.009 � .006       .0001
Trial 3                     +.019 � .006   +.004 � .005         .09

Cyclicity^e
Trial 1                         62%            77%               NS
Trial 2                         80%            82%               NS
Trial 3                         67%            60%               NS

^a NS = no significant differences.
^b Weight change is the change in weight from the start to the end
  of the feeding or treatment period in pounds.
^c Scale = 1 to 9 (1 = emaciated and 9 = obese).
^d Blood selenium content in ppm.
^e Cyclicity at the start of the breeding period as a percentage.
Body Condition. Initial and final body condition scores and changes in body condition during the supplemental period are presented in Table 1. Although differences were evident in Trial 1, when considering the results from all three trials, only minimal differences were observed during the supplemental period between cows receiving kenaf versus either oat or alfalfa hay. The results concerning changes in weight and body condition score would indicate that adequate levels of performance can be achieved when feeding kenaf as a supplemental feedstuff.

Blood Selenium. Initial and final blood selenium content and changes in blood selenium content during the supplemental period are presented in Table 1. In both Trials 1 and 2, blood selenium content at the end of the supplemental period and the changes in blood selenium content during the supplemental period were considerably higher (P<.0001) in cows that received kenaf as compared to cows that received oat hay. The results from Trial 3 indicated very minimal differences in blood selenium content. However, the decreased level of intake of kenaf could explain the lack of significant differences in this trial.

When considering results from all three trials, feeding kenaf can be effective in transferring selenium from the soils into the bloodstream of grazing cattle, provided that adequate levels of consumption are achieved.

Reproduction. There were no differences in cyclicity at the start of the breeding period between cows receiving kenaf versus cows receiving either oat or alfalfa hay (Table 1). Due to the lack of significant differences in weight or body condition score during the supplemental period, differences in cyclicity at the start of the breeding period would not be expected. Neither pregnancy rates nor subsequent calving dates were evaluated among the treatment groups because cows were in their respective treatment groups only until the start of the breeding period and not during the entire breeding season.

Summary. It appears that kenaf is a forage that can be fed to grazing beef cattle resulting in adequate weight gain, body condition score and reproductive performance as compared to typical forage supplements such as oat or alfalfa hay. In addition, feeding kenaf can be effective in transferring selenium from the soils into the bloodstream of the grazing cattle, provided that adequate intake levels can be achieved. However, if cattle are grazing highly palatable forages, adequate intake of kenaf may be difficult to achieve.

ACKNOWLEDGMENTS

Funding for this project was provided by the California Agricultural Technology Institute.

LITERATURE CITED

Frost, W. 1990. Atriplex tested as feed option. San Joaquin Experimental Range Newsletter, Spring, pp. 1-3.

Jones, D. and W. Frost. 1991. Atriplex as a selenium supplement. San Joaquin Experimental Range Field Day Proceedings. pp. 12-13.

McDowell, L.R., J.H. Conrad and G.L. Ellis. 1983. Mineral deficiencies, imbalances and diagnosis: Part II. Feedstuffs 19:21.

Phillips, W.A., C.R. Srinivas and T.H. Dao. 1990. The potential for using immature whole plant kenaf and tops of mature kenaf plants as a feedstuff for ruminants. Second International Kenaf Association Conference Proceedings.

Phillips, W.A., C.R. Srinivas and T.H. Dao. 1989. Nutritive value of immature whole plant kenaf and mature kenaf tops for growing ruminants. Proceedings Association Advancement of Industrial Crops. pp. 19-22.

Pugh, D.G., R.G. Elmore and T.R. Hembree. 1985. A review of the relationship between mineral nutrition and reproduction in cattle. Bovine Practitioner 20:10.

Smart, M.E., J. Gudmundson and D.A. Christensen. 1981. Trace mineral deficiencies in cattle: A review. Canadian Veterinary Journal 22:372.

Swingle, R.S., A.R. Urias, J.C. Doyle and R.L. Voigt. 1978. Chemical composition of kenaf forage and its digestibility by lambs in vitro. Journal of Animal Science 45:1347-1350.

Suriyajantratong, W., R.E. Tucker, R.E. Sigafus and G.E. Mitchell, Jr. 1973. Kenaf and rice straw for sheep. Journal of Animal Science 37:1251-1253.

Water Conservation and Drainage Reduction Programs. 1989. Westlands Water District Report. pp. 6-8.

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