Bakery by-products as feed ingredient for lactating cows may increase milk production and lower global warming potential.

An Italian case study shows promising results for adding bakery by-products as a feed ingredient to lactating cows’ diet. 

In Italy, dairy farms experience severe crisis due to economic speculation and climate change. This is challenging the sustainability of milk production. 

“In particular, rising raw material prices, drought and the presence of mycotoxins in maize have prompted dairy farms to make changes in the feed ration composition of lactating cows”, says researcher Martina Pavesi, Research Fellow at the University of Milan in Italy.

Bakery by-products may lower global warming potential from milk production 

At the moment, Associate Professor Stefania Colombini and colleagues at the University of Milan, are evaluating case studies on different cattle farms that use some sources of by-products in their diet. So far, the most promising result was seen in a farm that changed from a standard diet to a circular one, including bakery by-products. The cows in this case study farm were fed bakery by-products (former food) in their diets as energy source. The researchers concluded that the circular diet seemed to be more sustainable, in terms of global warming potential (GWP) related to milk production. They calculated the impact both per kilogram fat and protein corrected milk and per individual daily diet, using Life Cycle Assessment approach (LCA). 

The same farm recently changed from milking parlor to automatic milking system. This will be considered and modelled into research calculations, but the researchers still believe that the bakery by-product diet has a positive outcome in terms of sustainability. 

“In Vivo trials where cows were fed a control diet or a bakery by-product diet support the findings from the case farm. The milk production of the cows who were fed bakery by-products was a little higher” says Colombini. 

She adds that they expect a positive effect on feed-food competition, since bakery by-product from bakeries and supermarkets are not useful anymore for human nutrition.

Rumination trials indicate higher rumination activity

These days the researchers are conducting rumination trials. So far it seems like rumination time activity is increased by the bakery-by products diet. 

“Automatic measures of cows chewing activity shows higher chewing activity. We are currently waiting for digestibility data to verify if the higher rumination activity also promotes higher digestibility, especially with regards to fibre fraction”, says Colombini. 

Higher digestibility will usually lower the cows’ enteric methane intensity (g/kg milk) as a result of ennached ruminal fermentation. 

Questions are raised about the access to bakery by-products in large scale, but the results so far are promising for looking at other by-products included in diets to dairy cows. 

Dialogue with farmers and case studies from other countries

Dialogue and knowledge sharing are an important part of the CircAgric-GHG project. At the beginning of January 2024, the Italian researchers will arrange workshops with private companies and farmers to explore opportunities and barriers to adopting circular practices in Italy. Case study farms will receive individual feedback on their LCA-score and get advises of how they can lower the GWP level from their farms.  

Research colleagues in the project will further explore circular practices in other countries, such as lamb production in Spain and potato production in Norway. One on CircAgric-GHG goals is to share knowledge about circular practices on and between farms, regionally, nationally and internationally. 

Master student Ruben Carminati is sieving the ration and leftovers, preparing diet for the cows with bakery by-products at the University of Milan “Angelo Menozzi” Experimental farm.
Master student Ruben Carminati is sieving the ration and leftovers, preparing diet for the cows with bakery by-products at the University of Milan “Angelo Menozzi” Experimental farm.
Bakery by-product used in trial.
Adding bakery by-products as a feed ingredient to lactating cows’ diet may increase milk production and lower global warming potential on farm level.
Weight is measured using a hypsometer to observe any changes in weight throughout the trial.
The researchers collect samples of diets, leftovers, and individual ingredients from the feeding lane. These samples are then subjected to chemical analysis in the lab and digestibility tests. Additionally, feces and urine are also collected.
Each time the cows are milked by the robot, milk samples are collected. The quality of the milk is then analyzed to observe changes, for instance in protein or lactose levels, which might occur due to changes in their diet.

Other relevant studies:

A. Kaltenegger, E. Humer, A. Stauder, and Q. Zebeli (2020) Feeding of bakery by-products in the replacement of grains enhanced milk performance, modulated blood metabolic profile, and lowered the risk of rumen acidosis in dairy cows. J. Dairy Sci. 103:10122–10135 

A. Kaltenegger, E. Humer, C. Pacífico, and Q. Zebeli (2021) Feeding dairy cows bakery by-products enhanced nutrient digestibility, but affected fecal microbial composition and pH in a dose-dependent manner. J. Dairy Sci. 104:7781–7793 

Khiaosa-ard R, Kaltenegger A, Humer E and Zebeli Q (2022). Effect of inclusion of bakery by-products in the dairy cow’s diet on milk fatty acid composition. Journal of Dairy Research 89, 236–242. 

By: Anette Tjomsland Spilling. 
Photos: University of Milan. 
Published: 10.01.24