The researchers’ hypothesis was that substituting fermented rapeseed cake (FRC) produced through solid-state fermentation (SSF) with rapeseed cake (RC) in dairy cows’ diets may increase nutrient digestibility, positively modulate ruminal fermentation, mitigate CH4 formation, and improve milk production.
The scientists involved in the study, which was published in Animal Feed Science and Technology, noted how the SSF process one of the most recommended approaches to enrich the nutritional value of agricultural by-products by degrading fiber - cellulose and lignin - and eliminating anti-nutritional factors.
According to a study by Parmar et al., 2019, incorporating SSF materials at a rate of 5–20% in both ruminant and non-ruminant diets may increase growth, production, and health status with a reduction in CH4 production.
But the effects of FRC on milk production, ruminal fermentation, and fatty acid profile, when fed to ruminants, have not been studied yet; however, the results published on other fermented by-products assessed as animal feeds seem to be promising, they said.
The study
The researchers’ objective was to evaluate the impact of FRC on mitigating CH4 production and modulating ruminal fermentation using in vitro trials, ruminal fermentation, CH4 emissions and milk production and composition using in vivo trials, and ruminal nutrient degradation kinetics using an in-situ trial.
There undertook five successive experiments, each conducted separately.
The Hohenheim gas test was initially used to evaluate RC and FRC as substrates.
Following batch fermentation, an in vitro study was performed to assess the effects of replacing RC with FRC at 28.75, 57.5, 86.25, and 115 g/kg (FRC25, FRC50, FRC75, and FRC100) in the total mixed rations (TMR).
Based on the in vitro results, the control TMR and experimental TMR (FRC100) were chosen for an in vivo assessment.
Then four ruminally cannulated cows were fed the TMR ad libitum. In the fourth experiment, 20 multiparous Polish Holstein-Friesian cows in their mid-lactation were used in a completely randomized design. The cows were fed a partial mixed ration without the RC and FRC, and the RC and FRC were supplied in a concentrate feeder at 2.65 kg/d/cow.
In the fifth experiment, in-situ ruminal degradation of RC and FRC were explored using in-sacco techniques. The potential degradation and effective degradability of the dry matter (DM), organic matter, and crude protein were significantly higher for FRC than RC, saw the team.
Conclusions
The FRC100 markedly decreased CH4 production by 12% and archaeal population without adversely affecting nutrient digestibility, found the researchers.
The molar proportion of propionate was increased, and the molar proportion of acetate and butyrate and acetate to propionate ratio were decreased by FRC100.
No significant effects on milk production or composition, except an increase in milk urea concentration, were observed in cows fed FRC100, they said.
Milk C18:2 cis-9, trans-11 concentration was greater, and n-6 to n-3 fatty acid ratio was lower for FRC100 than the control diet.
“FRC may be used in the diet of lactating cow to lower CH4 production and improve milk fatty acid profile without adversely affecting ruminal fermentation, nutrient utilization and milk production,” commented the researchers.
However, of issue is the cost of FRC. It cost 0.052 euros per kg of milk while the price of RC was only 0.016 euros.
“The price for FRC is three times higher, and it is, therefore, less likely that farmers would use FRC to mitigate CH4 under the current situation, but a large-scale production of FRC using high-throughput technology might reduce the cost in future,” they noted.
Source: Animal Feed Science and Technology
Title: Effects of crude and fermented rapeseed cake on ruminal fermentation, methane emission, and milk production in lactating dairy cows
Authors: M Gao, A Cieślak, H Huang, M Gogulski, D Petric, D Ruska, A Kumar Patra, M Szumacher-Strabel