Dairy Mgt: Calf Colostrum (2)

Heifer Calves

-The future of the dairy farm

-Priority is to raise a healthy heifer for replacement

-We do this by understanding the digestive system, immune system, nutrient needs, and feed options

What are the differences between calves and mature ruminants?

Their digestive system hasn't fully developed yet

The Digestive System

-From birth to about 2 weeks of age, the calf is a monogastric

-As the calf begins to eat dry feeds, particularly grains containing readily fermentable carbohydrates, the rumen takes on a more important role.

-By 4 weeks of age, the reticulum and rumen comprise roughly 58% of the stomach, the omasum 12%, and the abomasum falls to about 30%.

-As the stomach develops more fully, the calf begins functioning as a mature ruminant. The objective of calf nutrition is to promote rumen development early in life.

Preruminant Digestion

In the young calf, some liquids can bypass the rumen and flow directly to the abomasum through the esophageal groove.

How is the esophageal groove formed?

The esophageal groove is formed when muscular folds from the reticulorumen come together, stimulated by sights and sounds calves associate with feeding and a reflexive response to swallowing.

What happens when a pre-weaned calf drinks milk?

-Any liquid (milk or water) consumed while the calf is excited by the anticipation of feeding bypasses the rumen and enters the abomasum.

-On the other hand, when the calf drinks in response to thirst, liquid enters the rumen instead of the abomasum

What happens after the calf drinks colostrum

-Within 10 minutes after milk or colostrum feeding, the liquid forms a clot in the abomasum due to enzymes (chymosin and pepsin) and hydrochloric acid acting on casein (milk protein) and fat in the milk.

-The clot or curd, will be digested slowly by stomach enzymes over a period of 12 to 18 hours.

-The fraction of milk that does not form a curd is called whey. Whey is composed of water, minerals, lactose, and other proteins (including immunoglobulins (antibodies)).

-From the small intestine, immunoglobulins can be absorbed into the calf's blood stream. Again, the newborn's limited digestive capacity aids the calf by enabling rapid absorption of the immunoglobulins that it needs.

Colostrum

-Colostrum is the first milk produced after a normal dry period, or the first milk secreted by a heifer.

-The quality, quantity, and timing (quickly) of colostrum feeding are major factors affecting calf morbidity and mortality.

-True colostrum contains twice as much dry matter and minerals and five times as much protein as whole milk. It is also higher in energy and vitamins.

-Colostrum also contains immunoglobulins.

Colostrum – Passive Immunity

-Calf is immuno-incompetent at birth = no resistance to pathogens

-In the bovine, antibodies cannot cross the placental wall and pass directly from the dam to the fetus.

-By supplying immunoglobulins (Ig) in the diet, specifically by feeding colostrum, calf is able to resist pathogens

-Ig are absorbed intact into the blood stream from the small intestine to help fight pathogens

-Absorptive ability is lost after 24 hours of life: “Gut closure”

-Passive immunity helps to protect the calf until its own immune system becomes fully functional.

Colostrum – Quality

-The primary colostrum antibodies are immunoglobulin G (IgG), immunoglobulin A (IgA), and immunoglobulin M (IgM).

-Two factors dictate colostrum quality: immunoglobulin concentration (specifically IgG) and the presence or absence of bacteria.

-In terms of IgG, good quality colostrum contains at least 50 g/L = (Brix value of ≥22% HOLSTEIN; ≥18% JERSEY).

-Bacteria counts of less than 100,000 (cfu/mL) are considered acceptable.

Colostrum – Quality measuring devices

-Brix refractometer: measures the bending of light as it passes through the sample.

-The scale in a Brix refractometer was originally designed to measure the amount of sucrose in a solution, but Brix values can be correlated to IgG.

-The colostromater estimates IgG content by measuring the specific gravity or density of colostrum, which is correlated with antibody concentration.

-The colostrometer is a hydrometer with a scale calibrated in milligrams per milliliter (mg/mL) of immunoglobulins.

Feeding rate of colostrum

Feed colostrum at 10% of body weight within 4 to 6 hours of life

Colostrum – Quantity

Since many calves will not or cannot drink this large amount at one time, an esophageal feeder may be used to feed all or part of the colostrum.

Colostrum – Quickly (Time)

-Timing of colostrum feeding is critically important for two reasons: the short-lived ability to absorb large molecules and the potential for pathogenic bacterial colonization of the intestine.

-The cells lining the intestine begin to mature shortly after birth.

-Secretion of digestive enzymes remains low (up to 12h), allowing antibodies to escape digestion and enabling maximum absorption.

-Stressed calves typically have even less time to absorb antibodies than normal calves.

-Calves born to dams that experienced heat stress before calving have also been found to absorb less IgG.

-(IgG concentrations <10 g/L when measured at 24-48 h of age)

Early bacterial inoculation of the gut 

Early bacterial inoculation of the gut creates another problem: immature intestinal cells can absorb infectious organisms as well as antibodies. If bacteria enter the bloodstream before antibodies, the calf has an extremely high risk of death.

Successful Passive Transfer (the 3 Q’s)

 Quality- IgG BRIX ≥ 22%

Quantity- 10% BBW

Quickly- within 12 hours of life (better if 6 h)

Colostrum – Storage and treatment Tip 1

Q-Tip #1: collect early

-Collect colostrum early after calving.

-Portable milkers work well.

-Keep the equipment clean and well maintained

Colostrum – Storage and treatment Tip 2

Q-Tip #2: Measure it fresh

-Although freezing does not appear to change the BRIX reading, freeze / thaw cycles may affect the IgG reading, and perhaps the relationship between BRIX and IgG

Colostrum – Storage and treatment Tip 3

Q-Tip #3 – store in single servings

-Better to use individual containers of colostrum, which would be about 2 to 4 L

-Colostrum may be frozen (at -5°F) for up to a year without significant decomposition of antibodies.

-Thaw in water below 120°F

Colostrum – Storage and treatment Tip 4

Q-Tip#4: Fridge for 1 day only

-Colostrum must be fed as soon as possible (within 1 hour) after collection or cooled to lower than 40°F to prevent bacterial growth during storage.

-Several studies have shown clearly that leaving colostrum in the refrigerator leads to increasing microbial load, fermentation of the colostrum and spoilage

Colostrum – Storage and treatment Tip 5 

Q-Tip #5: Pasteurization?

-In many cases, colostrum quality can be improved by heat treatment (pasteurization), which reduces bacterial contamination.

-When pasteurizing colostrum, heat at 140°F for 30 to 60 minutes to reduce bacteria counts without affecting colostrum IgG levels or viscosity.

-Keep the equipment clean and well maintained

Colostrum – Storage and treatment Tip 6

Colostrum supplement and replacer 

What are major factor affecting IgG concentration?

-Age of cow

-Dry cow nutrition

-Breed

-Immune status of dam

-First milking volume

-Time between calving and first milking

-Leaking milk during prepartum or birth 

-Season of year ( ex heat stress)