Dear sir,

these articles may be helpful.

Robinson, P. H., Tamminga, S., & Van Vuuren, A. M. (1987). Influence of declining level of feed intake and varying the proportion of starch in the concentrate on milk production and whole tract digestibility in dairy cows. Livestock Production Science, 17, 19-35.

Nocek, J. E., & Tamminga, S. (1991). Site of digestion of starch in the gastrointestinal tract of dairy cows and its effect on milk yield and composition. Journal of Dairy Science, 74(10), 3598-3629.

Herrera-Saldana, R., & Huber, J. T. (1989). Influence of varying protein and starch degradabilities on performance of lactating cows. Journal of Dairy Science, 72(6), 1477-1483.

 Regards

Partha

Dear Dr Swain,

     Thank you for your valuable references.

    May I know your personal opinion on this topic, as relevant to Indian context?

Regards,

sir ,

it is reported that there is a drop in milk production and milk fat synthesis on increase in the starch level in feeds. on digestibility, there was an increase in all the nutrients except that of starch.

this may be due to the feeding of concentrate and starch the molar proportions of acetate and propionate may change

Not a dairy nutritionist, but I have tried to understand this topic while reviewing strategies for reducing enteric CH4 emissions from dairy cows.  As I understand it, increasing the proportion of whole-plant maize silage (with high starch content) at the expense of other type of silage with lower starch content (e.g. grass silage) appeared to improve diet digestibility, and net energy intake leading to improved milk yield (kg milk/kg DMI) and milk protein content while reducing the enteric methane emissions intensity (g CH4/kg milk).  However, this topic appears to be a complex issue and perhaps following reviews may be useful in understanding it:

Gómez et al 2016. Starch in ruminant diets: a review. http://search.proquest.com/docview/1793542445?accountid=11233

Khan et al 2015. Nutritive value of maize silage in relation to dairy cow performance and milk quality. http://onlinelibrary.wiley.com/doi/10.1002/jsfa.6703/abstract

Knapp et al. 2014. Enteric methane in dairy cattle production: Quantifying the opportunities and impact of reducing emissions. http://www.sciencedirect.com/science/article/pii/S0022030214002896

Above the information shed by the rest of colleagues, think not only about starch content, but also forage:concentrate ratio, profile of fermentation of the forages, and effective fiber.

I will like to add that all these effects will be more pronounced in high yielders who are at risk of acidosis and feeding less starch grains like bajra sorghum could be helpful in these which can decrease risk of acidosis as well as may help to maintain normal rumen fermentation  process

Dear Dr Hujaz,

     Thank you for your answer.

     My point is not about acidosis etc. In normal Indian situation, where dairy cattle have to subsist on poor quality forages particularly in summer seasons, whether a high starchy compound feed is expected to perform better over its lower counterparts w.r.t. milk yield and composition? or a higher protein feed? (Keeping all other nutrients similar)

Regards

In my opinion we can go reverse by decreasing the starch content we can increase the overall all concentrate part in the ration which could be helpful in summer as DMI is less we can concentrate the diet and the nutrient requirements can be met 

Dr hujaz. There is a problem in increasing the density of concrntrate or energy density. As the DMI will go down this may create conditions like acidosis. Again starch is highly digestible which may make the condition still worse. In my opinion starch with highly palatable grasses will solve yhe purpose both for energy and DMI. 

That's what I am suggesting decrease the starch and increase the concentrate can be helpful 

Dear Drs Swain and Hujaz,

    We are slightly deviating the discussion from main topic.

     Particularly, if a farmer is feeding little green sorghum, ad lib. paddy/wheat straw and commercial compound feed, roughly at 40% of milk yield (suppose the milk yield is 12-15 kg/d), whether additional increase in starch level by feeding 1-2 kg maize grains/d (avoiding acidosis, as maize starch is slow rumen soluble) is expected to improve milk yield and particularly milk fat%?

Regards,

yes sir,

that was just an answer to hujaz... regarding the topic... we want some insights from you Sir.

Dear Mahesh,

Milk volume is strongly related the lactose bio synthesis; as the major osmol of the milk is lactose and its precursor is glucose, every manipulation which caused changing in glucose and glucose precursors level and also their availability for mammary epithelial cells consequently could affect milk yield and performance.

Starch is highly available for rumen microbes and before the first hour of intake it disappears completely. Some go trough microbial fermentation and some just pass the rumen. Changing VFA ratios and increase propionate as well as decrease pH is most expected effects of high starch containing diets. Propionate and passed starch mainly considered as glucose precursors.

the above mentioned is very brief and incomplete explanation of starch acting mechanism. along with this fact you must consider your eNDF, PeNDF, F/C ratio, CP level, CP source, E/N ratio and synchronization, period of study, rumen physiology such as papila length and many other parameters.

You could find many references in the internet. some of researcher also share you appreciated papers which could be useful.

Good luck