**4. Nutritional quality of weeds**

Although, weeds presence in and around the cultivated fields has never been deemed desirable, but these can contribute significantly to the production of quality organic feed for dairy animals. The nutritional profile of weeds determines feasibility and scope for their inclusion in ruminant's feed. The nutritional quality of weeds encompasses digestibility, chemical composition, energy and extent of presence of anti-nutritional factors and such information can assist to determine the allowable proportion of weeds in ruminant's feed [10, 33–35].

Dry matter digestibility has direct relationship with the quality of forage. Different weeds such as Barnyard grass (*Echinochloa crusgalli*) and Jerusalem artichoke (*Helianthus tuberosus*) had significantly higher digestibility compared to many cereal forages. The comparative dry matter digestibility of many weeds and forages crops is presented in **Table 1**. Digestibility was reported to be an important indicator of any forage's quality, while Lamb-squarters (*Chenopodium album*), barn-yard-grass (*Echinochloa crus-galli*), dandelion (*Taraxacum officinale*), Jerusalem artichoke (*Helianthus tuberosus*), yellow foxtail (*Setaria glauca*), perennial sowthistle (*Sonchus arvensis*) and Canada thistle (*C. arvense*) had in-vitro dry matter digestibility equal to alfalfa (*Medicago sativa*). In addition, common ragweed (*Ambrosia artemisiifolia*) and redroot pigweed (*Amaranthus retroflexus*) had even greater in-vitro dry matter digestibility compared to alfalfa [11, 39–41]. There is dire need to determine the digestibility of local weed flora in order to find out their suitability as an alternate animal feed.

Protein (CP) is the most important nutritional quality attribute having direct impact on milk production. Testing of 102 weed species belonging to *Poacea*,

**117**

anced nutrition [11, 36, 42–44].

*Changing Climate and Advances on Weeds Utilization as Forage: Provisions, Nutritional Quality…*

**Weeds DMD (%) Forage crops DMD (%)** Barnyard grass (*Echinochloa crusgalli*) Alfalfa (*Medicago sativa*) 64–75 Canada thistle (*Cirsium arvense*) 68–74 Sorghum (*Sorghum bicolor*) 59–61 Dandelion (*Taraxacum officinale*) 78–84 Maize (*Zea mays*) 63–68 Sowthistle (*Sonchus arvensis*) 76–82 Oat (*Avena sativa*) 60–63

Quackgrass (*Elymus repens*) 58–68 Pearl millet (*Cenchrus* 

54–62 Barley (*Hordeum vulgare*) 59–64

*americanus*)

*tetragonoloba*)

81–86 Cluster bean (*Cyamopsis* 

58–60

70–79

*Asteraceae*, *Fabaceae* and *Euphorbiaceae* families commonly found in central Mexico revealed that only 25 had balanced nutritional profile. Weeds CP content depend on growth stage as matured weeds recorded lesser protein compared to harvestings done at pre-bloom stage. Asthma plant (*Eurphobia hirta*) recorded 16.7% protein content while tick weed or Asian spider-flower (*Cleomea viscose*) with 14.7% followed it, while yellow nutsedge or nut grass (*Cyperus esculentus*) and button weed (*Diodia scandens*) contained 9.8 and 7.7% CP respectively. Bluegrass (*Poa annua*) was found to have over 14% which is higher than maize, sorghum and oat, while common purslane (*Portulaca oleracea*) (8%) was also suggested to be an equally good forage weed as far as CP content is concerned. Another study suggested that weeds including bush sunflower (*Simsia amplexicaulis*), creeping false holly (*Jaltomata procumbens*) and mosquito flower weed (*Lopezia racemosa*) contained CP in the range of 6.5–16.9% and could be used solely or as supplementary feed mixed with maize straw to feed dairy cattle. Mixtures of weeds (*Commelinaceae* + *Amaranthaceae*) recorded crude protein twice than most of the roughages. Another study reported that bush sunflower (*Simsia amplexicaulis*) weed supplemented with maize straw based animal diets resulted in higher protein content successfully met dairy animals dietary needs. Similarly, climbing dayflower (*Commelina diffusa* L.) recorded appreciably higher content of protein (17.7%) which is comparable to commonly used forage crops. In addition, its rumen degradability of protein was recorded over 72% making it forage with bal-

*Dry matter digestibility of some weeds and common forage crops grown under varied agro-climatic conditions* 

Brome grass (*Bromus tectorum*) 66–76 Cowpea (*Vigna unguiculata*) 68–76 Curly dock (*Rumex crispus*) 50–58 Soybean (*Glycine max*) 70–76

Higher content of fiber increases the bulkiness of feed which results in reduced intake. The lowest crude fiber content was recorded by button weed (18.7%) and nut grass yielded the highest fiber (27%). The minimum lignin content (9.6%) of asthma plant favored its inclusion in animal feed [18]. Similarly, common dandelion (*Taraxacum officinale*) recorded significantly lower crude fiber content (15%), while Bermuda grass (*Cynodon dactylon*) gave the lowest fiber content of just over 6% [11]. In contrast, barnyard grass (*Echinochloa crusgalli*) recorded the highest neutral detergent fiber (NDF) compared to trans-pecos drymary (*Drymaria laxiflora*) [45]. It was reported that climbing dayflower (*Commelina diffusa* L.) recorded 36% and 22% NDF and acid detergent fiber (ADF) respectively and thus compares well to commonly used grasses such as sorghum-Sudan grass and napier

*DOI: http://dx.doi.org/10.5772/intechopen.91386*

Swamp smartweed/knotweed/tanwed

Jerusalem artichoke (*Helianthus* 

*tuberosus*)

*[11, 28, 33, 36–38].*

**Table 1.**

(*Polygonum amphibium*)

*Changing Climate and Advances on Weeds Utilization as Forage: Provisions, Nutritional Quality… DOI: http://dx.doi.org/10.5772/intechopen.91386*


#### **Table 1.**

*Invasive Species - Introduction Pathways, Economic Impact, and Possible Management Options*

geographical localities while making the existing weed management strategies ineffective. In addition, weeds can have superiority over crop plants by virtue of better plant architecture and incorporating nitrogen and carbon in seeds. Rag weed (*Ambrosia artemissifolia*) developed more number of branches and leaf area along with producing greater number of pollens under increased temperature. Similarly, comparatively higher production of spines by Canada thistle (*Cirsium arvense*) in

In addition, biomass production of bitter vine/American rope (*mikania mikrantha*), creeping oxeye (*Wedelia trilobata*) and Cairo morning glory (*Ipomea cairica*) was enhanced with increasing CO2 level [28]. Spurred anoda (*Anoda cristata*) gave the highest green biomass at CO2 fertilization up to 700 ppm and 32°C temperature, while barnyard grass (*Echinochloa crusgalli*) and Indian goose-grass/wire grass/ crowfoot grass (*Eleusine indica*) remained non-responsive to elevated temperature and CO2 concentration. It was concluded that elevated CO2 effectively enhanced the photosynthetic process even under water limited conditions indicating higher water use efficiency of weeds under drought stress which led to higher to biomass production. However, weeds response to elevated CO2 and temperature under well watered conditions continues to remain an unexplored aspect which demands further research to determine the physiological plasticity of different weed species [25, 26]. The temperature elevation as a result of global warming is feared to trigger weeds migration. Cogon grass *(Imperata cylindrica*) prickly acacia (*Acacia nilotica*) and witch weed (*Striga asiatica*) were reported to invade cooler areas of Europe owing to global warming, while some of the invasive weed species such as mesquite (*Prosopis juliflora*) can become more hardy and difficult to control owing to greater portioning of assimilates to roots under elevated temperature particularly under

response to elevated CO2 level was reported [10, 24–27].

agro-ecological conditions of Indo-Pak subcontinent [27, 29–32].

the allowable proportion of weeds in ruminant's feed [10, 33–35].

Although, weeds presence in and around the cultivated fields has never been deemed desirable, but these can contribute significantly to the production of quality organic feed for dairy animals. The nutritional profile of weeds determines feasibility and scope for their inclusion in ruminant's feed. The nutritional quality of weeds encompasses digestibility, chemical composition, energy and extent of presence of anti-nutritional factors and such information can assist to determine

Dry matter digestibility has direct relationship with the quality of forage. Different weeds such as Barnyard grass (*Echinochloa crusgalli*) and Jerusalem artichoke (*Helianthus tuberosus*) had significantly higher digestibility compared to many cereal forages. The comparative dry matter digestibility of many weeds and forages crops is presented in **Table 1**. Digestibility was reported to be an important indicator of any forage's quality, while Lamb-squarters (*Chenopodium album*), barn-yard-grass (*Echinochloa crus-galli*), dandelion (*Taraxacum officinale*), Jerusalem artichoke (*Helianthus tuberosus*), yellow foxtail (*Setaria glauca*), perennial sowthistle (*Sonchus arvensis*) and Canada thistle (*C. arvense*) had in-vitro dry matter digestibility equal to alfalfa (*Medicago sativa*). In addition, common ragweed (*Ambrosia artemisiifolia*) and redroot pigweed (*Amaranthus retroflexus*) had even greater in-vitro dry matter digestibility compared to alfalfa [11, 39–41]. There is dire need to determine the digestibility of local weed flora in order to find out their

Protein (CP) is the most important nutritional quality attribute having direct impact on milk production. Testing of 102 weed species belonging to *Poacea*,

**4. Nutritional quality of weeds**

suitability as an alternate animal feed.

**116**

*Dry matter digestibility of some weeds and common forage crops grown under varied agro-climatic conditions [11, 28, 33, 36–38].*

*Asteraceae*, *Fabaceae* and *Euphorbiaceae* families commonly found in central Mexico revealed that only 25 had balanced nutritional profile. Weeds CP content depend on growth stage as matured weeds recorded lesser protein compared to harvestings done at pre-bloom stage. Asthma plant (*Eurphobia hirta*) recorded 16.7% protein content while tick weed or Asian spider-flower (*Cleomea viscose*) with 14.7% followed it, while yellow nutsedge or nut grass (*Cyperus esculentus*) and button weed (*Diodia scandens*) contained 9.8 and 7.7% CP respectively. Bluegrass (*Poa annua*) was found to have over 14% which is higher than maize, sorghum and oat, while common purslane (*Portulaca oleracea*) (8%) was also suggested to be an equally good forage weed as far as CP content is concerned. Another study suggested that weeds including bush sunflower (*Simsia amplexicaulis*), creeping false holly (*Jaltomata procumbens*) and mosquito flower weed (*Lopezia racemosa*) contained CP in the range of 6.5–16.9% and could be used solely or as supplementary feed mixed with maize straw to feed dairy cattle. Mixtures of weeds (*Commelinaceae* + *Amaranthaceae*) recorded crude protein twice than most of the roughages. Another study reported that bush sunflower (*Simsia amplexicaulis*) weed supplemented with maize straw based animal diets resulted in higher protein content successfully met dairy animals dietary needs. Similarly, climbing dayflower (*Commelina diffusa* L.) recorded appreciably higher content of protein (17.7%) which is comparable to commonly used forage crops. In addition, its rumen degradability of protein was recorded over 72% making it forage with balanced nutrition [11, 36, 42–44].

Higher content of fiber increases the bulkiness of feed which results in reduced intake. The lowest crude fiber content was recorded by button weed (18.7%) and nut grass yielded the highest fiber (27%). The minimum lignin content (9.6%) of asthma plant favored its inclusion in animal feed [18]. Similarly, common dandelion (*Taraxacum officinale*) recorded significantly lower crude fiber content (15%), while Bermuda grass (*Cynodon dactylon*) gave the lowest fiber content of just over 6% [11]. In contrast, barnyard grass (*Echinochloa crusgalli*) recorded the highest neutral detergent fiber (NDF) compared to trans-pecos drymary (*Drymaria laxiflora*) [45]. It was reported that climbing dayflower (*Commelina diffusa* L.) recorded 36% and 22% NDF and acid detergent fiber (ADF) respectively and thus compares well to commonly used grasses such as sorghum-Sudan grass and napier

grass (*Pennisetum purpureum*) [9]. Similarly, spiderwort (*Tripogandra purpuracens*), a weed of South America recorded reasonably good concentration of carbohydrates which was higher compared to *Tridax coronopifolia* and was recommended to be fed to dairy animals [10, 11, 13, 19, 37, 46].

Digestibility is an important indicator of any forage's quality. Lambsquarters (*Chenopodium album*), barn-yard-grass (*Echinochloa crus-galli*), dandelion (*Taraxacum officinale*), Jerusalem artichoke (*Helianthus tuberosus*), yellow foxtail (*Setaria glauca*), perennial sowthistle (*Sonchus arvensis*) and Canada thistle (*C. arvense*) had in-vitro dry matter digestibility equal to alfalfa (*Medicago sativa*). In addition, common ragweed (*Ambrosia artemisiifolia*) and redroot pigweed (*Amaranthus retroflexus*) had even greater in-vitro dry matter digestibility compared to alfalfa. Similarly, it was reported that high protein and low fiber contents are indicative of high energy and high productive value feeds. Field bindweed (*Convolvulus arvensis* L.) and common amaranth (*Amaranthus retrofl* exus L.) recorded the highest protein (18.8 and 13.0% respectively) and the lowest fiber (14.7 and 17.6% respectively) which was comparable to alfalfa (*Medicago sativa*) hay having 16.9% protein and 27% fiber. In addition, especial emphasis was paid to palatability of weeds as high nutritional value becomes irrelevant if animals have little likelihood for the weeds species. The hay of different weeds was given to sheep to determine their palatability by using cafeteria of manger technique and biomass consumed in 15 minutes was recorded. Alfalfa had the highest palatability followed by field bindweed (*Convolvulus arvensis* L.)


#### **Table 2.**

*Nutritional quality (organic matter, crude protein CP, acid detergent fiber ADF, neutral detergent fiber NDF, fats F, total ash A) of weeds [11, 17, 21, 31, 35, 39, 41, 48, 49].*

**119**

**Table 3.**

*Changing Climate and Advances on Weeds Utilization as Forage: Provisions, Nutritional Quality…*

and common amaranth (*Amaranthus retrofl* exus L.) owing to higher protein and lesser fiber contents. Thus, it was inferred that protein and fiber content of feeds can be used as predictors of palatability and it was also concluded that weeds leaves had 2–3 times higher protein than stems and thus leafy weeds such as field bindweed (*Convolvulus arvensis* L.) recorded higher palatability [11, 45, 47]. The

Minerals in appropriate quantity are essential for dairy animals to be utilized in various metabolic processes, for boosting immunity level against diseases and reproductive health. Asthma plant (*Eurphobia hirta*) was recommended to be included in animal feed for having reasonably higher concentrations of major minerals including calcium (Ca) (13.6%), magnesium (Mg) (3.0%) and potassium (K) (2.5%), along with many trace elements such as iron (Fe) (0.7%), copper (Cu) (0.1%) and manganese (Mn) (0.1%). Common chicory (*Cichorium intybus*) was also suggested as forage weed for having a comparable mineral composition including Ca (6%), Mg (2%), Fe (0.5%) and Cu (0.06%). In addition, pink sorrel (*Oxalis debilis*) was found to be poor on animal nutrition scale for being deficient in Ca (4%), Mg (2.3%), Fe (2.4) and Zinc (Zn) (0.15) compared to other forage weeds [10, 21, 48]. Very limited information has been reported so far regarding mineral constituents of weeds which limit their utilization as a feed source for ruminants.

**Weeds Ca Mg Zn** Wild oat (*Avena fatua*) [11] 1.8 1.10 0.06 Burr clover (*Medicago polymorpha*) [11] 10.2 2.42 0.14 Morning glory (*Ipomoea purpurea*) [40] 9.0 0.63 2.99 Yellow duck (*Rumex crispus*) [11] 4.7 2.70 0.20 Cheese weed (*Malva parviflora*) [40] 19.3 1.22 4.59 Wood sorrel (*Oxalis decaphyllai*) [40] 5.1 1.43 2.76

*Mineral constituents (calcium Ca, magnesium Mg and zinc Zn) of different weeds grown under varied* 

Condensed tannins, saponins, phytate and oxalate are some of the anti-nutritional factors which reduce the nutritional quality and even impart toxicity to animal feeds. It was reported that button weed (0.029–0.052%) had the lowest tannin content, while nutsedge recorded the maximum tannin content. It was suggested that weeds having tannins 2–4% of dry matter did not pose a life threatening situation rather were found to be effective in improving protein flow towards duodenum which led to higher weight gain and reduced the parasitic infections. It was suggested that effective drying of weeds has the potential to significantly reduce the condensed tannins of weeds. Similarly, saponins which are generally produced by defense systems of weeds in response to pathogenic attacks impart a bitter taste and reduce nitrogen

nutritional quality of some weeds has been presented **Table 2**.

**Table 3** contains mineral constitution of some weeds.

**6. Anti-nutritional contents of weeds**

*agro-climatic conditions [11, 18, 22, 32, 40].*

*DOI: http://dx.doi.org/10.5772/intechopen.91386*

**5. Mineral constituents of weeds**

*Changing Climate and Advances on Weeds Utilization as Forage: Provisions, Nutritional Quality… DOI: http://dx.doi.org/10.5772/intechopen.91386*

and common amaranth (*Amaranthus retrofl* exus L.) owing to higher protein and lesser fiber contents. Thus, it was inferred that protein and fiber content of feeds can be used as predictors of palatability and it was also concluded that weeds leaves had 2–3 times higher protein than stems and thus leafy weeds such as field bindweed (*Convolvulus arvensis* L.) recorded higher palatability [11, 45, 47]. The nutritional quality of some weeds has been presented **Table 2**.
