Tropical vs. temperate forages: Nutritional composition and fiber digestibility

Risma Rizkia Nurdianti

Animal Scientists - Ph.D. Candidate at University of Hohenheim

5 min read
21/01/2025
Tropical vs. temperate forages: Nutritional composition and fiber digestibility

Tropical vs. Temperate Forages: Nutritional Value and Fiber Digestibility Explained

Summary

In this article, the author compares tropical and temperate forages, focusing on their nutritional composition and fiber digestibility. Tropical forage legumes have higher fiber concentrations and lower digestibility than their temperate counterparts. While crude protein levels are similar across regions, tropical forages generally have higher undigested fiber (uNDF240), which may reduce dry matter intake and nutrient digestibility in ruminants.

Tropical vs. temperate forages: Nutritional composition and fiber digestibility

Feeding domestic ruminants with high-quality forages is fundamental. In temperate regions, feeding ruminants with forage legumes has been known to enhance animal performance instead of feeding animals with solely low-quality forages (e.g., grasses) or concentrate diets, which can cause subacute ruminal acidosis (SARA). However, it might differ when tropical forage legumes are fed to the animals in tropical regions. A previous study mentioned that if a high inclusion of tropical forage legumes (> 40%) is supplied to the ruminant, it might lower the dry matter intake (DMI) and the apparent nutrient digestibility of animals. Forages cultivated in tropical regions contain less crude protein (CP) concentration with more fiber and lignin concentrations than those grown in temperate areas. Therefore, tropical forage legumes are expected to be a negative factor affecting the DMI of ruminants. 

Recently, undigested neutral detergent fiber (uNDF; i.e., remaining neutral detergent fiber after an infinite period of degradation by rumen microorganisms) was proposed as the most commonly used proxy of filling rumen capacity by a forage. The uNDF fraction can be assessed by long-term (240 h) in vitro fermentations (uNDF240). Thus far, studies on uNDF240 concentrations and their effects on feeding behavior, fiber digestibility, and performance in lactating cows have focused on temperate forages. In contrast, limited studies have been conducted on evaluating the fiber fraction and its degradability (i.e., uNDF and potentially digestible neutral detergent fiber (pdNDF) concentrations in tropical forages.

A previous study (Palmonari et al., 2016) reported that the uNDF240 concentration of maize silage (118 g/kg DM) is lower than that of alfalfa hay (201 g/kg DM) and grass hay (227 g/kg DM) in temperate region. Another previous study reported that uNDF240 concentration of low-quality grass hay (267 g/ kg DM) is higher than medium-quality grass hay (85 g/ kg DM) and high-quality grass hay (82 g/kg DM) from temperate regions (Nurdianti et al., 2023). Moreover, diets with high uNDF240 concentration and highly digestible alfalfa hay allowed for greater DMI, longer rumination time, and higher ruminal pH in lactating cows kept in European dairy systems, suggesting that the limiting factor for DMI is fiber digestibility and its rumen retention time (Fustini et al., 2017). Meanwhile, a recent study (Nurdianti et al., 2024) analyzed the variability in nutritional composition and fiber digestibility of forage legumes and grasses from tropical regions and compared it with forage legumes and grasses from temperate regions as described below. 

  • Nutritional composition of forages - Tropical vs. temperate forages

The CP concentrations of tropical forage legumes, tropical grasses, temperate forage legumes, and temperate grasses ranged from 149 to 251 g/kg DM, from 43 to 121 g/kg DM, from 181 to 303 g/kg DM, and from 45 to 147 g/kg DM, respectively. There is no difference in CP concentrations between tropical forage legumes and temperate forage legumes and between tropical grasses and temperate grasses. However, CP concentrations of forage legumes and grasses are different despite differences in environmental conditions, which indicates that CP concentrations are relatively similar in tropical forage legumes and temperate forage legumes.

The ash-corrected neutral detergent fiber (aNDFom) concentrations for tropical forage legumes, tropical grasses, temperate forage legumes, and temperate grasses ranged from 219 to 492 g/kg DM, from 418 to 631 g/kg DM, from 173 to 354 g/kg DM, and from 404 to 700 g/kg DM, respectively. The aNDFom concentrations of tropical forage legumes were greater than those of temperate forage legumes but much lower than those of tropical grasses and temperate grasses. Meanwhile, there is no difference in aNDFom concentration between tropical grasses and temperate grasses, which indicates that aNDFom concentration is relatively similar. Additionally, tropical forage legumes have higher acid detergent fiber (ADF) and lignin concentrations than temperate forage legumes, as well as tropical grasses and temperate grasses.

  • Fiber digestibility of forages - Tropical vs. temperate forages

The uNDF240 concentrations of tropical forage legumes, tropical grasses, temperate forage legumes, and temperate grasses ranged from 113 to 376 g/kg DM, from 125 to 308 g/kg DM, 76 to 177 g/kg DM, and from 78 to 275 g/kg DM, respectively. Meanwhile, uNDF240 proportions of tropical forage legumes, tropical grasses, temperate forage legumes, and temperate grasses ranged from 0.437 to 0.803, from 0.209 to 0.597, from 0.348 to 0.565, and from 0.209 to 0.597, respectively.

The pdNDF concentrations of tropical forage legumes, tropical grasses, temperate forage legumes, and temperate grasses ranged from 75 to 216 g/kg DM, from 107 to 473 g/kg DM, from 96 to 230 g/kg DM, and from 208 to 464 g/kg DM, respectively. Meanwhile, pdNDF proportions of tropical forage legumes, tropical grasses, temperate forage legumes, and temperate grasses ranged from 0.197 to 0.563, from 0.403 to 0.791, from 0.435 to 0.652, and 0.515 to 0.856, respectively. The pdNDF proportion (as a proxy of fiber digestibility) is low in certain tropical forage legumes, which might limit DMI if they are supplemented in ruminant diets.

Conclusion

Tropical forage legumes have higher fiber but lower digestibility compared to temperate forage legumes. This makes tropical legumes less suitable for high inclusion in ruminant diets, though they remain preferable to tropical and temperate grasses in terms of fiber concentrations.

References

Castro‐Montoya, J. & Dickhoefer, U. (2018). Effects of tropical legume silages on intake, digestibility and performance in large and small ruminants: A review. Grass and forage science73(1), 26-39.

Fustini, M., Palmonari, A., Canestrari, G., Bonfante, E., Mammi, L., Pacchioli, M. T., Sniffen, G.J.C., Grant, R.J., Cotanch, K.W., & Formigoni, A. (2017). Effect of undigested neutral detergent fiber content of alfalfa hay on lactating dairy cows: Feeding behavior, fiber digestibility, and lactation performance. Journal of Dairy Science100(6), 4475-4483.

Harper, K. J. & McNeill, D. M. (2015). The role iNDF in the regulation of feed intake and the importance of its assessment in subtropical ruminant systems (the role of iNDF in the regulation of forage intake). Agriculture5(3), 778-790.

Nurdianti, R. R., Nuryana, R. S., Handoko, A., Hernaman, I., Ramdani, D., Jayanegara, A., Dickhoefer, U. Böttger, C., & Südekum, K. H. (2023). Nutritional compositions of Katuk leaves and their supplementation to hays of different quality: an in vitro study. The Journal of Agricultural Science161(3), 428-437.

Nurdianti, R. R., Dickhoefer, U., & Castro-Montoya, J. M. (2024). Relationship between nutritional composition and fibre digestibility in tropical forages compared to temperate forages. Italian Journal of Animal Science23(1), 1839-1853.

Palmonari, A., Gallo, A., Fustini, M., Canestrari, G., Masoero, F., Sniffen, C. J., & Formigoni, A. (2016). Estimation of the indigestible fiber in different forage types. Journal of Animal Science94(1), 248-254.

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Risma Rizkia Nurdianti
Animal Scientists - Ph.D. Candidate at University of Hohenheim

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