Current Progressive Dairy digital edition
Advertisement

Fresh cow nutrition is still a work in progress

John Hibma for Progressive Dairyman Published on 30 September 2016

Feeding fresh cows has been an ongoing challenge for the dairy industry for many years, especially since the national average for a single lactation is over 22,000 pounds and climbing.

That means a fresh cow has to be ready to put some serious milk in the pail just as soon as she’s taken out of the maternity pen and put into the fresh string. Cows in their third or greater lactation must be producing well over 100 pounds of milk in a matter of days after freshening and be able to sustain that level of production for several months with minimal metabolic problems.

advertisement

advertisement

While research on the late-stage dry cow or close-up nutrition abounds, much less research has been conducted on the nutritional needs of the fresh cow and formulating diets that will sustain both the health of the cow and her rumen while maintaining daily milk production in the hundreds of pounds.

The single largest challenge in formulating fresh cow diets is getting cows to consume the levels of feed necessary to sustain a high energy status that will support milk production while at the same time mitigating metabolic diseases and negative energy balance.

The most important nutrient in a fresh cow diet (after water) is calories. The most limiting nutrient in a fresh cow diet is calories. Fresh cow energy requirements increase significantly immediately after calving.

To meet the energy requirement of early lactation, nutritionists and dairy farmers must maximize the feed intake of a diet that incorporates a high energy density per pound or kilogram of feed as well as maintaining a rumen forage mat that supports microbial fermentation. In order for cows to maximize dry matter intakes, the rumen has to be in top operating condition.

Starch is needed in the diet to produce the volatile fatty acid propionate, which is a major component in the production of blood glucose. Propionate is produced during fermentation of starches in the rumen.

advertisement

Glucose production increases significantly within a week after calving. Therefore, for a cow to maintain adequate energy metabolism during the first critical weeks of lactation, all volatile fatty acid production, especially propionate, must be maximized. Nutritionists continue to debate the question of how much starch to include in a fresh cow diet to satisfy energy requirements without decreasing pH and causing ruminal acidosis.

It’s well-known there’s a fine line existing between too much starch in a rumen, contributing to various levels of acidosis and not enough starch and energy to support milk production, and keeping negative energy to a minimum.

The challenge for nutritionists is discovering a balance where the cost-effectiveness and health ramifications of an energy-dense diet with higher levels of starch don’t negatively impact the health and productivity of the cow later in lactation.

Research conducted at Cornell University and the W.H. Miner Agricultural Research Institute has concluded that there’s no easy answer to that question. The two institutions conducted studies with four different diets characterized by differing combinations of starch and fiber. The four diets were:

  • High starch – high fiber, HSHF
  • Low starch – high fiber, LSHF
  • High starch – low fiber, HSLF
  • Low starch – low fiber, LSLF

Crude protein in all diets averaged between 16.5 percent and 15.3 percent dry matter (DM), with blood meal providing part of the essential amino acids. Starch levels ranged from a high of 28.3 percent to a low of 21.5 percent DM and fiber (defined as neutral detergent fiber or NDF) ranged from 26.4 percent to 36.9 percent DM, with wheat straw being the primary feedstuff adjusting fiber levels.

For older cows, in second lactation and greater, milk production was the highest for the low-fiber diets – both with high starch and low starch. However, the feed intakes for the HSLF group was 9 pounds lower than the LSLF group while producing nearly the same amount of milk. These data suggest that something nefarious was occurring in the rumens of the HSLF group, reducing feed intakes.

advertisement

In fact, cows in this test group experienced dramatically higher rates of clinical ketosis and displaced abomasum than cows consuming the other three diets. The researchers pointed out in the study that the incidences of ketosis and displaced abomasum in the low-fiber diets were alarming enough for them to restart the trial.

Once the fiber deficiency was corrected, the trial progressed with no reported issues, with displaced abomasum and only 12 percent ketosis.

This is an indication that effective fiber levels and maintaining a proper rumen forage mat are critical to avoiding metabolic diseases in fresh cows and a crash in milk production later in the lactation, even though they may start off with impressive milk production.

When formulating diets for fresh cows, greater attention should be paid to the NDF value of the ration and not allowing the ration NDF to drop below 30 percent DM. In this study, the undigestible NDF (uNDF240hr – a new number for many of us) was consistently maintained at 0.3 percent of bodyweight for older cows and 0.2 percent of bodyweight for first-calf heifers.

To complicate the matter, first-lactation heifers showed less consistency between groups for milk production, with the highest production coming from the LSHF diet. All of the first-calf heifers produced about 30 pounds less milk than the older cows.

The study also showed that heifers were just as likely to experience ketosis and displaced abomasum as the older cows with the low-fiber diets.

Due to social interaction issues with heifers transitioning into milking herds and the fact that they eat less feed, it is advisable to keep fresh heifers segregated from older cows to minimize the potential for metabolic problems.

Worth noting is that the milk-to-feed efficiency for all animals across the entire study ranged between 1.8 and 2.0 – all respectable values. These metrics may seem acceptable but are actually misleading if and when deleterious health events sneak up later in the lactation.

There has been considerable discussion over the years as to the value of close-up diets containing moderate levels of starch that will enable the rumen to adapt to high-energy diets upon calving.

Recent research suggests that growth of rumen papillae during the close-up period is not significantly impacted by transition diets with increased starch levels. It is prudent, however, that close-up cows do receive the same feedstuffs they would be consuming after freshening in order that the appropriate types of rumen microbes will be present and ready to ferment those feeds.

Recent studies continue to support the long-held belief that starch levels in fresh cow diets exceeding 27 percent DM result in lower rumen pH for longer periods of time. Excessive starch in fresh cow diets will result in acidotic rumens and poor rumen function, including fiber fermentation and feed intakes.

A conservative target for starch in the fresh cow diet would be 25 percent of total DM. While starch is needed in the synthesis of blood glucose and the energy status of the cow, clearly there is a limit as to the amount of starch a cow can handle before her health is adversely affected.

Within the industry, the “fresh cow” diet is often a variation of the “high-cow” diet, formulated with an arbitrarily lower starch value, a small amount of straw for effective fiber and rumen-protected fat to maintain metabolizable energy.

The optimal level of starch in fresh cow diets should be formulated based upon the amount of effective fiber in the diet. Fresh cow diets should be formulated to contain high-quality forages with highly digestible NDF levels, as well as enough uNDF that will assure maximum fermentation and a strong microbial population that will keep metabolic diseases to a minimum.

Pushing the starch levels in fresh cow diets should be contingent upon the reliability and competency of dairy management to closely follow diet recommendations and a willingness to adhere to stringent dietary guidelines.  end mark

Some information for the article was taken from the 2015 Cornell Nutrition Conference Proceedings, Feeding the Fresh Cow; McCarthy, Dann & Overton.

John Hibma
  • John Hibma

  • Consulting Ruminant Nutritionist
  • South Windsor, Connecticut
  • Email John Hibma

LATEST BLOG

LATEST NEWS