Monday, May 9, 2016

What Percentage of Colostrum Antibodies end up in the Blood?

Given a few facts it is possible to estimate the efficiency of absorption of antibodies by calves. Need to know the calf's weight and the volume of antibodies fed.

Quigley notes in his Calf Notes #81 that observed variation in this efficiency varies from 20 to 35 percent. That's right. Feed 100 units of antibodies and only 20 to 35 end up in the blood. Don't be surprised. It is a rough trip for antibodies from mouth to small intestine where they are transported from the intestinal wall into the blood - think of all those abomasal acids!

A recent report at the University of New Hampshire collected data from 28 calves. They found efficiency of absorption averaged 26 percent.

A study done in Florida looked at the question of heat stress on the dam precalving might effect the efficiency of absorption of antibodies by their calves.

 Ten dry cows had luxury apartments - their free stall area had fans and soakers. Ten dry cows had the standard housing - no fans, no soakers. The temperature-humidity index in both stall areas averaged 78. (Referring to the standard THI graph, 78 is in the upper end of the "moderate-heat-stress" range. That puts it relatively close to being classified as "severe heat stress.")

The heat-stress cows had higher rectal temperatures compared to cooled cows. Cooled cows had a respiration rate of 49 breaths/minute compared to 67 br/min for heat-stressed cows. Lots of huff and puff for the heat-stressed cows.

What happened to their heifer calves? They were all fed the same volume of the same quality of colostrum at about the same time after birth. The calves from heat stressed cows had an apparent efficiency  of absorption of 19 percent. In contrast the calves from cooled cows had an absorption rate of 33.6 percent. 

What do I conclude?

1. If we want high levels of circulating antibodies from colostrum in our calves we need to feed enough antibodies to allow for a high level of losses.

2. Given large variations from calf-to-calf in efficiency of absorption (mostly unpredictable) our best management strategy is to feed enough high quality colostrum shortly after birth to all our calves to get adequate immunity even among the calves with low efficiency.

On a side note, feeding a greater volume of colostrum to newborn calves can be a poor policy if the colostrum is badly contaminated with bacteria. The greater number of bacteria fed the greater the chances that the calf will either get quite sick or die. Please do not increase the volume you feed to calves (for example, increase from 2 quarts to 4 quarts) until you have confirmed that your colostrum is clean.

References: S. Tao and Others, "Effect of late-gestation maternal heat stress on growth and immune function of dairy calves." Journal of Dairy Science 95:7128-7136. K.M. Aragona and Others, "Prepartum supplementation of nicotinic acid: Effects on health of the dam, colostrum quality and acquisition of immunity in calf." Journal of Dairy Science 99:3529-3538.

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