Evaluating the potential of feedstuffs for dairy cattle in Southeast Asia

Grasses belonging to the genus Pennisetum and whole crops such as sorghum are considered to be suitable feedstuffs for higher milk yield and milk fat content. Photo: Canva

Reports show that in Southeast Asian countries, the dairy industry produces insufficient milk to meet current demand. Researchers from Wageningen University & Research determined the fermentation characteristics of commonly used feedstuffs to identify suitable ingredients for formulating dairy rations that suit the region.

Despite the genetic potential of dairy cows in Southeast Asian countries, which are mostly crossbred between Holstein Friesian and local breeds, milk yields and fat content are low. Previous studies show that, for example, Thai and Vietnamese dairy cows produce 4,000 to 4,500 kg of milk per lactation with a mean fat content of less than 4%. This is partially attributable to environmental conditions, but nutritional management strategies are also important and can help alleviate the challenges.

Information on the rumen fermentable organic matter (FOM) content of feedstuffs and the fermentation rate is essential to optimise dairy rations for milk production and composition. However, what is observed is that the FOM content of feedstuffs is not routinely assessed and is lacking in the major feeding tables in Southeast Asian countries. This lack of information prompted researchers from Wageningen University & Research to investigate 29 commonly used feedstuffs for dairy nutrition in Southeast Asia for their rumen fermentable organic matter (FOM) contents and their degradation kinetics.

29 commonly used feedstuffs

In this study, the researchers collected 29 individual feedstuffs commonly used to feed dairy cattle in Thailand and Vietnam. These were fresh grasses, preserved roughages, whole crop ingredients and single concentrates. The data on single concentrates were provided as a relative benchmark for the grasses and the other roughages as well as for future reference.

Degradation rate and VFA production of fresh grasses

Variables such as the cumulative in vitro gas production at 72 h (GP-72 h), organic matter digestibility (OMd), and total volatile fatty acid (TVFA) (Table 1) were considered to be indices of the in vivo rumen fermentable organic matter (FOM) content of the different feedstuffs. Total gas production (GP-72 h) was influenced by genus with the genera Brachiaria, Panicum, and Pennisetum producing 222, 226, and 245 mL/g OM, respectively.

The researchers concluded that “assuming that the asymptote gas production (GP) values associated with both the soluble and non-soluble fractions are the most suitable indicators of the rumen fermentable organic matter (FOM) content of the fresh grasses. King grass and VA06 grass are the most promising to increase the FOM content of dairy rations in Vietnam and Thailand.”

Volatile fatty acids (VFAs) values are used to evaluate potential milk yield and composition. It is well established that VFA, acetic acid, is an important precursor of fatty acid synthesis in the mammary gland of dairy cows, while propionic acid is an important precursor for gluconeogenesis and important in the intramammary process of lactose synthesis.

The amount of lactose produced in the mammary glands of dairy cows is the major determinant of the amount of milk produced. A high ratio between acetic acid and propionic acid will potentially result in a greater proportion of fat content in milk.

According to the researchers, FOM originating from slowly degrading roughage shifts rumen fermentation towards greater proportions of acetic acid, potentially resulting in a greater proportion of milk fat. In this study, the Pennisetum genus had the highest acetic: propionic acid ratio, suggesting a better genus to improve milk fat content. However, the researchers highlighted the fact that their results indicate that in vitro VFA fermentation values are similar between tropical grasses, especially when the grasses are all cut at a mature state.

Degradation rate and VFA production of preserved and whole-crop roughages

Across the preserved roughages and whole crops, the organic matter digestibility (OMd) and total volatile fatty acid (TVFA) values were greatest in sorghum and lowest in Pangola hay (Table 2). Preserved roughages had relatively similar values of acetic acid percentage while fairly large differences were observed for the whole crops. Sugarcane had the lowest acetic acid value and acetic: propionic (A:P) ratio, suggesting that it is the least suitable ingredient for enhancing milk fat content. As whole crops, sorghum and sunflower were considered good feed ingredients to increase milk fat content, owing to the OM digestibility, acetic acid value and acetic: propionic (A:P) ratio.

Remarks concerning single concentrate feedstuffs

Single concentrate feedstuffs caused greater gas production and organic matter digestibility than the rest of the feedstuffs and this was attributed to higher contents of soluble carbohydrates, except for rice bran which had the lowest digestibility values among all the concentrate feeds. Among the concentrate feedstuffs, rice bran had the lowest TVFA while the highest was observed in cassava peeled tuber. The highest molar proportion of acetic acid was found in green bean shells, while the highest value of propionic acid was observed for cassava waste. The single concentrate feedstuffs used were palm kernel cake, brewer’s grain, coconut meal, cassava waste, green bean shells, rice bran, corn grains and cassava peeled tuber.

This article is based on the publication: In vitro gas and methane production of some common feedstuffs used for dairy rations in Vietnam and Thailand. Animal Bioscience, Vol 37, Issue 3, 2024.