Intake factors in dairy cattle

Intake factors in dairy cattle

Dry matter intake is a primary determinant of final production, and increasing dry matter intake in dairy cattle is paramount to maximizing production.

*Bryan Miller is ruminant technical support manager, Americas, for BIOMIN.

ALTHOUGH the concept of feed intake is relatively simple, the factors affecting it can vary dramatically, including animal effects such genetic propensity or selection to eat, neurologic and hormonal feedbacks regarding satiety, metabolic conditions and diseases.

The feed itself can affect intake from a variety of characteristics, including moisture, taste, fat content, fiber content, etc.

Because ruminants rely on fermentation of nutrients from volatile fatty acids to microbial protein, they are at risk for disturbances from feed changes and factors affecting microbial growth.

Because dairy cattle are ruminants, they are essentially consuming feed at all times. As such, some of the satiety controls and monitors found in monogastric animals may not be effective to the same level in dairy cattle.

 

Rumen, gut effects

Does rumen fill cause satiety? In evaluating rumen fill, researchers have used inflated balloons in the rumen to simulate fill, resulting in decreased voluntary intake (Br. J. Nutr. 1993. 68:699). However, at physiological levels, this feedback mechanism is unlikely to be the sole or major reason for decreased intake.

Work with sheep has demonstrated that the duodenum has receptors that are affected by titratable acidity but not glucose or osmolality (J. Physiol. 1984. 354:497). Work in sheep has also demonstrated that infusion of propionate to the liver results in decreased intake with the feedback to the brain via nerve transmission (which is interesting when one considers that propionate is the primary gluconeogenic volatile fatty acid).

Circulating ketones such as beta-hydroxy butyrate can reduce feed intake in both monogastrics and ruminants. Produced when cows are in negative energy balance, or lack glucose, they lead to a negative spiraling down of dry matter intake.

 

Feed management

Feed formulation is the area in which management can most greatly affect dry matter intake.

Within common diets, dry matter intake can be fairly well predicted based upon the energy content of the diet and the level of milk production. They do not predict potential intake and subsequent production.

Fats and diets high in simple carbohydrates can certainly increase caloric density. However, there is a threshold before issues of absorption and acidosis limit their use.

Intake by today's dairy cattle is often restricted by the physical constraints of moving enough feed through the system. Toward this end, it is important to maximize the digestible fiber portion of the diet.

Neutral detergent fiber, as a measure of forage quality, is important in predicting forage dry matter intake. However, the digestibility and rate of digestibility are also important in predicting intake. Enzyme, chemical treatments and genetic selection for more digestible neutral detergent fiber portions have resulted in increased digestibility and subsequent intake.

For cattle to consume or continue eating new feed, the previously consumed feed contents must disappear through a combination of digestion and passage. Feed fiber utilization is maximized through good fermentative characteristics in the rumen, which include both proper pH and available nitrogen for bacterial growth.

 

Weather effects

Dairy cattle have a fairly wide thermal neutral zone, from 5 degrees C to 20 degrees C, and are generally more tolerant of cooler temperatures. It is the combination of temperature and humidity that affects the "comfort" of the cattle.

The combination of heat and humidity can decrease feed intake by 10-25% and, in extreme conditions, by as much as 55% (National Research Council dairy requirements, 2001), as shown in the Table.

Management tools to deal with heat and humidity include the use of misters, fans, reduced crowding and dietary changes to include more fats and less fiber.

 

Summary

Dry matter intake is a result of the innate ability of the dairy cow to consume feed based on her genetics, which affect gut volume, sensory and hormonal controls. Dairy producers need to maximize this potential for dry matter intake through dietary selection and providing an environment conducive to maximal feed intake.

 

Temperature and humidity combinations that can negatively affect milk production

-Temperature-

Humidity,

 degrees F

 degrees C

%

84

29

15

80

26

30

77

25

50

75

24

65

72

22

90

Source: Dr. L.E. Chase, Cornell University.

 

Feeding frequency

Presentation of feed through either new feeding or pushing up of currently offered feed has been shown to increase feeding behavior (Can. J. Anim. Sci. 1994. 74:103).

Mycotoxins

Feed intake can also be reduced by the presence of mycotoxins such as deoxynivalenol and trichothecenes (T2) in the feed. Cattle consuming fescue pasture or hay have lowered heat tolerance and subsequent dry matter intake due to the alkaloids they contain (J. Anim. Sci. 2004. 82:634).

Moisture content of diet

Generally, diets containing greater than 50% moisture have been associated with decreased intake. This reduced feed intake is related to the fermented products of such diets rather than the water content per se (J. Dairy Sci. 1990. 73:2916).

 

Volume:85 Issue:50

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