Tuesday, January 23, 2018

Overcrowding Wins Again

Overcrowding heifers has been shown over and over again to depress rates of gain and increase variability in growth within pens. This study reported over a 9% drop in average daily gain as overstocking increased. 

In this 91-day research with 900# heifers the stocking rates were 100, 125 and 150 percent. The comparisons were made on average daily gain, within pen variations in gains, and hygiene scores.

Depending on the two rations  (one included short straw and the other included long straw) the drop in rate of gain took place at different stocking rates.

For the ration including short straw the rates of gain dropped 9.4% as stocking went up from 100 to 125% with no change between 125% and 150%. [Actual change was from 2.2#/day down to just over 2# per day] The level of variation of gain within pen went up progressively from 100 to 125 to 150 percent stocking.

For the ration including long straw the rates of gain dropped about 5% as stocking went up from 125 to 150%. The level of variation of gain within pen went up progressively from 100 to 125 to 150 percent stocking.

I did not try to do an economic comparison using the value of rate of gain vs. cost of housing. The study did not place a value on the decrease in uniformity of rates of gain as overcrowding rates went up.

Dirty legs and flanks - the rate of soiled animals went up as soon as the stocking rates in all pens was greater than 100%.

Reference: Coblentz, W. K. and Others, "Effects of straw processing and pen overstocking on the growth performance and sorting characteristics of diets offered to replacement Holstein dairy heifers." Journal of Dairy Science 101:1074-1087.


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