 
Who saw this article? New!
Author: Dan N. Waldner - Sandra R. Strokes - Ellen R. Jordan - Michael L. Looper
Various feeding management practices impact the levels of milk fat and protein
concentration in raw milk. Feeding strategies that optimize rumen function also
maximize milk production and milk component percentages and yield. There are several
strategies that producers can use to enhance rumen function and the resulting
milk components. Producers who use records, such as those provided by DHIA (Dairy
Herd Improvement Association), can critically evaluate their nutrition and feeding
management programs.
Feed Intake: Feed provides the nutrients
that are the precursors, either directly or indirectly, of the principal milk
solids. Thus, an increase in feed intake usually results in the production of
a greater volume of milk. In general, the proportional increases in fat, protein,
and lactose yields are approximately the same as the proportional increase in
milk volume.
Milk composition changes little.
It is critical to maximize feed intake of cattle so that negative energy balance
is minimized during early lactation. As cows consume more energy than they use,
body weight is regained, losses in body condition are minimized, and cows produce
milk of normal fat and protein content. Increasing feed intake, and the resulting
overall increase in energy, can increase milk protein content by 0.2 to 0.3 percent.
High producing cows should eat 3.5 to 4.0 percent of their body weight daily as
dry matter. If a herd is consuming less than this, production of solids-corrected
milk may be limited.
Major factors that can affect feed intake include:
- Feed bunk management (keep feed bunks clean, not empty)
- Feeding frequency
- Feed sequencing
- Ration moisture between 25 and 50 percent (to optimize dry matter intake)
- Social interactions and grouping strategy of the herd
- Abrupt ration changes
- Physical facilities
- Environmental temperature.
Increased feeding frequency of low fiber, high grain diets increases milk fat
levels. The greatest increase occurs in diets ofless than 45 percent forage
and when grain is fed separately as in parlor feeding. When diets are fed as
a total mixed ration, feeding frequency becomes less important as long as the
feed remains palatable and is fed and mixed a minimum of once a day. During
hot weather, more frequent feeding helps keep feed fresh and palatable.
Forage to Concentrate Ratio: On
a DM (dry matter) basis, the minimum ratio of forage to concentrate required
to maintain normal milk fat percentage is approximately 40-to-60. This ratio
should serve only as a guide; other dietary factors influence the general effects
that a decreased ratio has upon rumen fermentation. These effects include decreased
rumen pH, increased propionic acid production and reduced fiber digestion. Obviously,
type and physical form of ingredients that contribute to the forage or concentrate
portion of this ratio must be considered.
Grain Feeding: The proper feeding
of concentrates involves maintaining proper forage-to-concentrate ratios and
nonfiber carbohydrate levels. Feeding appropriate nonfiber carbohydrate levels
can improve both milk fat and protein levels, while overfeeding leads to milk
fat depression of one unit or more and often increases milk protein percent
by 0.2 to 0.3 units.
Nonfiber carbohydrates include starch, sugars, and pectin. The percentage of
nonfiber carbohydrate is calculated as NFC = 100 - (% Protein + % NDF + % Fat
+ % Ash). Depending on the digestibility of the neutral detergent fiber (NDF)
present, nonfiber carbohydrates should range from 34 to 40 percent of the total
ration dry matter. In most instances, a nonfiber carbohydrate level between
36 to 38 percent is considered ideal. This level is typical of diets with less
than 60 percent forage. Diets with greater than 60 percent forage may be deficient
in nonfiber carbohydrates.
When feeding for component changes, limit the amount of grain consumed during
one feeding to 5 to 7 pounds to avoid rumen acidosis and off-feed problems that
result in reduced fat content of milk. Grain feeding guidelines to maximize
milk fat and protein production are provided in Table 1. Limit grain consumption
to a maximum of 30 to 35 pounds per cow daily.
Manure containing large amounts of undigested corn or with a pH less than 6.0
can indicate too much grain or an imbalance of nonfiber carbohydrates in the
diet. Fibrous byproducts such as soybean hulls can replace starchy grain and
reduce the severity of milk fat depression in rations high in nonfiber carbohydrate.
Grain Processing: The type of grain
and processing method can have a significant impact on the site and extent of
starch digestion of a particular diet and resulting milk component composition
and yield (Table 2). Generally, ground, rolled, heated, steam flaked, or pelletized
grain increases starch digestibilities and propionic acid production in the rumen.
Steam flaked corn or sorghum compared to steam rolled corn or dry rolled corn
or sorghum consistently improves milk production and milk protein yield. In six
comparisons, steam flaked corn increased milk protein percentage and yield and
decreased milk fat percentage compared to steam rolled corn. Milk fat yield remained
unchanged in these trials. Twenty-four (24) comparisons of dry rolled and steam
flaked sorghum have produced similar results. These results are attributed to
increased total tract starch digestibility, increased recycling of urea to the
intestinal tract and increased microbial protein flow to the small intestine.
Extensive use of grains, such as wheat, that consist of a rapidly fermentable
carbohydrate and overprocessing of grains can result in severe milk fat depression,
off-feed problems and reduced milk yield. It is important to match carbohydrate
and protein sources and to carefully monitor nonfiber carbohydrate levels in the
diet to ensure proper fermentation patterns and to maximize milk component content
and yield.
Ration Fiber Levels: The level of fiber feeding and the physical size of fiber
particles contribute to the effectiveness of a fiber source for stimulating
rumination (cud chewing), buffer production (salivation) and maintenance of
normal milk fat and protein composition. Feeding of finely ground forages inadequately
stimulates rumination and lowers saliva production.
The crude protein requirement for a 1,350-pound cow producing 3.6 percent milk
fat ranges from 14.0 percent of total dry matter (TDM) for 50 pounds of milk to
18.0 percent TDM for 100 pounds of milk. Depending on the stage and level of production,
the recommended level of undegradable protein ranges from 32 to 38 percent of
crude protein. Keep soluble protein between 30 to 32 percent of crude protein,
or about half of the degradable protein intake level.
It is essential to meet the cow’s requirement for both crude protein and
rumen undegradable protein to avoid a negative impact on dry matter intake and
fiber digestibility. Studies of diets containing no supplemental fat show that
each 1 percent increase in dietary protein, within the range of 9 to 17 percent,
results in a 0.02 percentage unit increase in milk protein. The additional synthesis
of protein by mammary tissue likely is linked to limiting amino acids. Table
4 summarizes the various feeding management practices and their potential impact
on milk fat and protein concentration.
Author: Dan N. Waldner - Sandra R. Strokes - Ellen R. Jordan - Michael L. Looper
Who saw this article? New!
MAKE A COMMENT ABOUT THIS ISSUE.
 
|
Technical Articles
