Source: Paul Beck - Oklahoma State University Extension Beef Nutrition Specialist Apr 11, 2022
Many of the calves grazing wheat this winter were pulled off earlier in March so that a wheat crop could be harvested. However, some of the calves are just now coming off grazeout wheat and other cool-season cover or forage crops in preparation for planting cotton or summer grain crops like milo or soybeans. Price adjustments to compensate for different shrink conditions are common in the cattle industry. Stocker operators, cattle feeders, and livestock marketers are constantly searching for more information on shrinkage of cattle through the marketing channels.
Generally, the amount of shrink varies with the type of feed cattle are on before penning and transport.
Cattle consuming high moisture diets, such as wheat pasture, tend to shrink more when removed from feed than cattle fed drier diets. Wheat pasture is often 25% or less in dry matter, or over 75% water, one of the highest moisture diets, making it notorious for a high rate of shrink when cattle are removed from pasture and transported to markets or feedlots. Along with diet there are many other management factors that influence loss of bodyweight and the rate of shrinkage, these include length of time off feed and water, weather conditions, and weigh up conditions (such as handling, how far it is from the pasture to the pens and cattle disposition).
Calves on wheat at Oklahoma State University were removed from pasture and weighed, then either penned in facilities next to the pasture or were drove by foot up and down an adjacent dirt road for a total of 1.6 miles. Calves were then comingled and held in the drylot pens for 24-hours. Following the 24-hour shrink, cattle were reweighed and returned to pasture for 25 hours to determine the extent of weight recovery. When cattle were reweighed following 24-hours they shrunk over 8%. Driving cattle on foot for 1.6 miles did not increase the amount of shrink compared with simply removing them from pasture and holding them for 24-hours without feed or water. The rate of shrink is quite high, related to the very high moisture content of the wheat forage, but cattle had regained all the lost weight by 6 hours after being placed back on pasture.
Two weeks later, this same group of steers were transported on trailers for 4-hours either directly off wheat pasture or after they were given access to hay and water for 24-hours. After 4-hours of transit steers directly off wheat lost 37 pounds (5.1% shrink). Steers given access to hay before transport lost 28 pounds (3.85% shrink) over the same haul. This shows that shrink losses were about 1.18% per hour of transport, but providing access to a dry hay before transport decreases shrink, which is possibly due to slower passage rate of feed through the digestive tract and less water loss.
This research was conducted by Matt Cravey, Gerald Horn, Ken Poling, and Bobby McDaniel and is available at https://extension.okstate.edu/programs/beef-extension/research-reports/site-files/documents/1991/91-19.pdf.