An international team of researchers from Brazil and Canada examined the use of supplemental yerba mate (YM) in dairy cattle feed as an antioxidant. The group published its work in the journal of Animal Feed Science and Technology.
“The objective of the present study was to determine the effects of different amounts of YM in the diet on feed intake, digestibility and milk composition of dairy cows,” the researchers said. “The hypothesis was that increased YM amount in the diet improves antioxidant properties and decreases lipoperoxidation in milk when cows are fed a diet enriched with canola seed, a source of PUFA [polyunsaturated fatty acids].”
The group found that adding the supplement improved the “reducing power” in milk and might improve antioxidant activity, the researchers said. However, several elements of production and milk components were similar for all the diets.
“Our goal was to investigate the potential effects of different amounts of YM in the diet on feed intake, digestibility and milk composition of dairy cows,” they concluded. “The results found in this paper showed a promising role for YM as an antioxidant source for increasing reducing power in milk from dairy cows, without changing DM intake, milk composition and production.”
“The reducing power in milk was increased with the inclusion level of YM in the diet, thus suggesting that oxidative stability of milk can be enhanced with this feeding strategy,” they added.
Why yerba mate?
Adding ingredients with polyunsaturated fatty acids (PUFA) to the feed of dairy cattle increases the amount of those fatty acids in the milk fat and are considered “health promoting,” said the researchers. But, milk with increased PUFA levels may be more vulnerable to oxidation.
Antioxidant molecules may be added to dairy products to prevent oxidation, they said. However, supplemental antioxidants also can be added to dairy cattle feed.
Past research with flax found that lignans were transferred to the milk of cows that received a feed that included flaxseed meal, said the researchers. Cows eating 50 to 100 g/kg flaxmeal in their feed had reduced production of thiobarbituric acid reactive substances (TBARS) in their milk.
“Naturally occurring antioxidants such as polyphenols then may contribute to limit milk oxidation as they exhibit various antioxidant properties,” they said.
Yerba mate is a plant native to South America and known to produce antioxidant activity as it contains several compounds including polyphenols, they said. It has a greater concentration of polyphenols than green tea or red wine.
It also contains chlorogenic acids, which modulate gene expression of antioxidant enzymes, they said. The supplement is thought to have the ability to scavenge free radicals similar to gallic acid. And past research has reported that YM products have had a similar antioxidant as butylated hydroxytoluene – a common phenolic synthetic antioxidant.
“Altogether, these results suggest that YM could prevent oxidation in milk enriched with PUFA and provide the consumers with dairy products with improved health benefits,” the researchers said. “However, there is little information on YM supplementation to dairy cow diets.”
One previous study fed 250 g/d of dried YM leaves to lactating dairy cows and reported a significant increase in milk yield, they said.
Methods and materials
In the study, eight lactating cows were given one of four diets for a period of 21 days and then changed to another trial diet, the researchers said. The diets included a control corn silage-based diet with ground canola seed and that diet with 25, 500 or 750 g/d of supplemental YM.
“On a dry matter (DM) basis, YM contained 126 g/kg crude protein, 35 g/kg ether extract and 380 g/kg neutral detergent fiber (aNDF),” they said. “Polyphenolic profile of YM consisted of 216.33 mg/g gallic acid equivalent of chlorogenic acid, 35.49 mg/g quercetin equivalent of rutin, 6.33 mg/g gallic acid equivalent of caffeine, and 0.51 mg/g of caffeic acid.”
Milk samples were taken for analysis on day 18, and amounts of diet material, refusals and YM were collected from days 15 through 21, said the researchers. Fecal samples also were collected.
Total reducing power in milk also was established, they said.
Results
The feed supplement did not alter overall milk production or change milk protein and fat contents, the researchers said. However, increased amounts did reduce lactose, total solids and milk urea nitrogen concentration.
“Inclusion of YM had no effect on DM intake and milk production of lactating dairy cows fed a diet with 50 g/kg DM of ground canola seed,” they said.
Digestibility levels for dry mater, protein and neutral detergent fiber were similar for all of the diets, they said. The digestibility of ether extract dropped as additional YM supplementation was added.
Levels of total polyphenols, conjugated diene hydroperoxides and thiobarbituric acid reactive substances also were similar for cows getting the differing diets, said the researchers. However, reducing power was found to increase in parallel with the amount of YM supplement in the feed.
“The reducing power in milk increased with the inclusion level of YM in the diet, thus suggesting that antioxidant activity of milk can be enhanced with this feeding strategy although it was clearly insufficient to overcome the negative effects on milk fat synthesis probably caused by the high levels of fat added to diets as ground canola seed,” the researchers said.
Source: Animal Feed Science and Technology
Title: Intake, digestibility and milk production and composition of dairy cows fed different levels of Yerba Mate in the diet
DOI: doi.org/10.1016/j.anifeedsci.2017.05.019
Authors: F. Santos, L. Zeoula, G. dos Santos, L. Lima, A. Dias, M. Rufino, A. Schogor, F. De Marchi, H. Petit,