Limited diets with high DDGs inclusion support growth, nutrient digestion in dairy heifers

Use of high levels of dried distillers grains maintains growth performance and increases digestibility for dairy heifers getting limited rations, says researcher.

A team of researchers at South Dakota State University examined the use of dried distillers grains (DDGs) in limited ration diets for dairy heifers. The group published their results in the Journal of Dairy Science​​.

The work with limited rations and dairy heifers was an effort to see if the by-product could be used to increase feed efficiency and maintain growth rate, said Jill Anderson, corresponding author and assistant professor of dairy cattle and heifer nutrition at South Dakota State University.

“It provides an alternative protein source that is usually very economical to feed to cattle in general and dairy cattle,” ​she told FeedNavigator. “That’s why we started researching it to begin with and it’s proving to be a good protein source and energy source for the heifers.” ​

The goal of the study was to examine the influence on growth performance when DDGs were included as the major ingredient in a diet and to establish the effects on rumen fermentation and total-tract digestibility, said the researchers. A limited ration was used to control average daily gain (ADG).

The group hypothesized that increasing the amount of DDGs in the diet would support growth performance, and that there would be alterations in the rumen formation that could increase the gain to feed ratio and nutrient utilization as larger amounts of DDGs were added.

The researchers found that replacing up to 50% of the dry matter (DM) with DDGs maintained growth performance, body weight (BW), ADG and frame growth, they said. They also saw a linear increase in the gain: feed ratio and digestibility of DM, organic matter (OM) and crude protein (CP).

Why DDGs and limited diet?​

Anderson has been working with distillers’ dried grains and cattle diets for several years, she said.

“In some of our past research, we’ve been conservative and not gone past 20-30% distillers in the diet,” ​she said. The new test looked at including up to 50% DDGS in the diet, she added.

Additionally, the research looks at the development of dairy heifers and others work has focused on diets for beef cattle or lactating cows, said Anderson.

The project was also an effort to help provide data for producers interested in using DDGs, she said.

“We’re trying to develop some guidelines, and how does it work with different feeding scenarios so producers can make more informed decisions, and so they can make more decisions about how to include it optimally,” ​said Anderson.

Materials and methods​

In the study, 48 dairy heifers were given one of three diets for a period of 16 weeks, said the researchers. The diets were a grass hay and mineral mix supplemented with 30% DDGs with the diet fed at 2.65% of body weight (BW), 40% DDGs fed at 2.5% of BW or 50% DDGs fed at 2.35% of BW.

Body measurements including BW, withers and hip heights, heart and paunch girth, body length and hip width were noted every two days then every two weeks, they said. Body condition score (BCS) was recorded initially and every two weeks.

Samples of rumen fluid were collected twice on weeks 12 and 16 and analyzed for pH, ammonia and volatile fatty acids (VFA), they said. Fecal samples were taken on week 16 to check for total-tract digestibility.

Results​

BW, ADG, BCS and frame size were similar for all diets, said the researchers. Dry matter intake fell as the gain: feed ratio improved linearly.

In the rumen, propionate concentration increased linearly with more DDGs presence in the diet and both butyrate and the acetate to propionate ratio declined, they said. Ammonia concentration also grew linearly.

The digestibility of neutral detergent fiber (NDF) and acid detergent fiber (ADF) was similar for all they diets, they said. But digestibility of DM, OM and CP increased with higher levels of DDGs in the diet.

The results were in line with what the research team was anticipating, said Anderson. “The shift in fermentation that we saw was a little surprising, but it went hand-in-hand with what we saw in feed efficiency so it made sense,”​ she added.

In the trial diets the crude protein level increased, which led to a bump in the ammonia level in the rumen, but it wasn’t at a concerning amount, she said.

The group also had tracked the VFAs and saw an increase in propionate and a drop in acetate production, she said. That reaction is associated with improved feed efficiency and a reduction in gas production by the cow.

There are however factors to keep in mind if producers are considering implementing a limited ration system with their heifers, or planning to increase the amount of DDGs in their diets, said Anderson.

“Especially for growing heifers, [producers] can easily build in 20-30% and replace concentrate ingredients,” ​she said. “It pairs well with grass hay or lower quality corn silage.”​

However, it is important to keep watch sulfur levels, especially if the water source is high in sulfur, she said. Also, a limited ration system works best with animals of similar ages and when there is adequate bunk space for feeding.

What’s next?​

There are additional pieces of the research that are set to be published, said Anderson. As the team examined the digestibility of the feed ingredients, they also looked at the metabolic profile of the heifers and tracked their developed through lactation.

“Our next paper [is] on the metabolic profile,” ​she said. “There [also] was a small effect on puberty and heifers on the largest amount of distillers’ achieved puberty earlier.”​

It appears that adding supplemental fat to the diet can alter when heifers reach puberty, she said. But the group is still working out the implications of that interaction.