Accurately Estimating Shrink in Grass Cattle

By Steve Paisley, UW Extension Beef Cattle Specialist

Shrink – it’s a BIG DEAL

As grazing programs and grassfed beef become increasingly important, one of the major issues affecting transactions is trying to accurately estimate the amount of shrink in cattle being sold.

The term “shrink” refers to the animal’s reduced weight resulting from stressors associated with gathering from the pasture, standing in the pen, processing and weighing and transportation. Accurately estimating the actual amount of shrink experienced is difficult.

Most often buyer and seller agree to some amount of “pencil shrink,” or a figure applied to the overall weight of the livestock. Pencil shrink is usually an estimate of what the expected weight loss will be, hopefully divided equally between buyer and seller.      

However, as with most issues, there are many factors that can affect the total amount of shrink. While much of the research involving shrink is anecdotal, or merely observations during a larger research study, there have also been studies that specifically looked at the stressors involved with holding cattle in drylot and transporting cattle, and the resulting impacts on short term weight loss and overall health.

Types of shrink

While shrink seems to be a straightforward term, we can actually break down the weight lost into three or four areas. These include 1) urine and fecal losses, 2) respiratory losses and 3) actual tissue loss.

When stress is low, such as hauling short distances, and working cattle during cool weather, the overall amount of shrink is lower, and urine and fecal losses (referred to as “gut fill”) are the major losses, typically 60 to 70 percent of the weight loss. Longer hauls, higher temperatures and a greater amount of overall stress obviously increase the total amount of shrink, and the gut fill component becomes a smaller percentage of the weight lost. Respiratory losses, or the water lost during breathing, combined with actual tissue losses can collectively be as high as 50 percent, or half of the weight lost. This point becomes important if you are buying or receiving these cattle. Electrolytes, especially potassium, are very important to replenish, and often cattle that experience seven to nine percent shrink require one to two weeks to totally regain the lost weight.

Estimating shrink

In a recent review paper, seven studies evaluated shrink in drylot (no access to feed or water) and trucking. Cattle in the studies ranged from 570 to 1,000 pounds, and these studies suggest that most of the urine and fecal losses, or “gut fill,” is lost relatively quickly, averaging 0.75 percent/hr to 1.25 percent/hr during the first five hours of drylot or shipping. So, even the shortest hauls can result in four to five percent shrink when you combine gathering, drylot and shipping time.

After the initial five-hour period, weight loss can be variable depending on conditions, but seems to be reduced, ranging from 0.9 percent/hr to 0.11 percent/hr.  Studies looking at trucking shrink on intermediate to long hauls estimated that cattle lose 0.61 percent/100 miles. This is in addition to any initial shrink involved with gathering, processing and drylot prior to being loaded on a truck. Estimating the amount of shrink on short hauls is more difficult, as the impacts of gathering, penning, processing and handling have a larger impact than actual trucking.

When to gather

Fort Keogh/Miles City has also evaluated the importance of when cattle are gathered on final weights and amount of shrink. Their studies suggest that allowing cattle to graze for a few hours after daylight improved weights by 1.9 to 2.5 percent, and cattle experienced less shrink compared with cattle that were not allowed to graze prior to gathering. Similar results were also reported in Kansas, suggesting that it might pay to order the trucks for 9 a.m. and have another cup of coffee before gathering.
Additional factors affecting shrink

Many feeds, diets and ingredients have been used with the hope that they may reduce shrink, and most have varied to no impact on the amount of shrink.
Back when I worked in Oklahoma and Kansas, I observed many stocker producers who would often feed grain 24 to 48 hours before selling and weighing cattle, assuming the grain would sit in their rumen, much like that extra piece of cheesecake. Studies looking at pre-shipping diet indicate there are no positive impacts on shrink when grain is fed prior to weighing. However, studies looking at the subsequent health of these calves, especially lighter-weight calves, indicate that supplements fed, in some cases medicated supplements, improved overall health once they were received by the buyer. Preconditioning calves prior to shipping is certainly important to overall calf health, especially after they are received in the background yard or feedlot, but there does not appear to be any impact on shrink losses. Some work with ionophores (Bovatec and Rumensin) suggest that there is a small reduction in the amount of shrink when ionophores were part of the overall ration or supplementation program prior to shipping.

Estimating shrink can be elusive, especially because temperature, time of day, distance to gather and overall handling impact the amount of shrink. Minimizing, or at least recording, the amount of time it takes to gather cattle, the amount of time that they have been removed from feed and water, and the distance/time it takes to ship cattle are all important in estimating and negotiating shrink.

Initial weight loss, mainly due to gut fill, can be lost quickly, at 0.75 to 1.25 percent/hr. After the initial five hours of drylot or shipping, the rate drops to .9 to .1 percent/hr.  When shrink approaches seven to nine percent, cattle typically need as much as one to two weeks to completely regain shipping losses.
While shrink is very important to estimate, management of cattle before and after shipping is also important for overall health, performance and, ultimately, carcass merit.