Impact of ruminal volatile fatty acids on milking performance

An intact and effective ruminal fermentation is a prerequisite for a healthy and productive dairy cow. The fermentation processes are performed by ruminal microorganisms, whose growth depends on supply with feed. Type and feed ingredients determine the composition of the ruminal microflora.While acetate is formed from fermentation of fiber, propionate and butyrate are formed from fermentation of high-digestible carbohydrates (sugar, starch). The acetate/propionate ratio should be >2.2:1.

 

As ruminants live in symbiosis with their ruminal microflora, some fermentation products are substrates used by the animal to meet its energy and nutrient demand for itself, its offspring and performance products. This also applies to volatile fatty acids (VFAs), which are produced by degradation of organic substance. Beside VFAs, ruminal gases (methane, carbon dioxide) are produced from fermentation, whereby the amount is determined by type of feed.

 

With regard to the impact of VFAs on performance, it is obvious that each adverse change in ruminal microflora and thus, fermentation, affects animal performance.

 

VFAs as end products of ruminal fermentation are sources of various syntheses (glucose for energy supply and formation of lactose in mammary gland, fatty acids for body and milk fat). Propionate is the main substrate for gluconeogenesis. Hence, it is a precursor of glucose for energy supply, but during lactation it is also used for formation of lactose. In early lactation when demand exceeds available amount of VFAs, propionate is preferably used for synthesis of lactose. In contrast, acetate and butyrate are incorporated into body fat, but are also sources of fatty acid synthesis for milk. A reduction of VFA production and/or negative change of their ratios means an impairment of these processes.

 

The consequences of an impaired fermentation and thus VFA production can be observed in the transition period in particular: decreasing feeding capacity of the rumen leads to reduced feed intake, whereby especially fiber intake is reduced which in turn negatively affects ruminal fermentation. Due to high concentrate content of the ration in early lactation, pH decreases which can result in acidosis, in turn leading to an impairment of fermentation, animal health and a depression of performance. A negative energy balance is often the consequence of an unsufficient energy supply in the transition period. Body reserves have to be mobilized resulting in metabolic disorders (e.g. subacute acidosis, ketoacidosis, milk fever, fatty liver). Furthermore, the cow is more susceptible to inflammation due to weak immune response. Negative long-term effects on the cow are possible, which can result in high economic losses for the farmer.

Most important measure to avoid negative changes in fermentation and thus, VFA production is maintaining feed intake by providing high quality and palatable feed. Furthermore, the ration should be balanced, i.e. the concentrate to fiber ratio should be adapted to nutritional and physiological needs of the cow. Further supporting measures are cow comfort and prevention of stress. To prevent milk fat depression, beside fiber content of the ration, also the physical structure of the feed and a sufficient supply of unsaturated fatty acids should be taken into account. Additionally, phytogenic feed additives can help to stabilize feed intake and to support ruminal fermentation processes.

 

Sangrovit® helps to stabilize feed intake and improve ruminal fermentation including VFA production. This is of high impact especially in phases of increased stress, e.g. the transition period and calving. Thus, Sangrovit® supplementation led to improved ruminal fermentation by higher degradation of organic substance and higher production of acetic and propionic acid. Latter means better energy supply for the cow. Isobutyric and isovaleric acid were reduced which indicates decreased protein degradation and/or more efficient microbial protein synthesis. This can additionally be confirmed by a reduction in ruminal ammonia production. With regard to performance, Sangrovit® has shown to increase milking performance up to 5% (first 120 days from calving), but also milk ingredients were improved. Thus, fat and protein % in milk increased by 3.2 and 1.2, respectively.