A better understanding of factors affecting shrink should help buyers and sellers of cattle to arrive at a fair pencil shrink under specific marketing conditions.

Types of Shrink. There are two types of shrink. One is excretory which is the loss of urine and feces. When ambient temperatures are low (below freezing, urine and fecal output can comprise 30-35% of shrink. When temperatures are hot, urine and fecal losses account for about 15-20% of shrink. Much of this loss is replaced when cattle are again allowed to eat and drink.

The second type is loss is tissue loss. It is the loss of fluid from the cells. Tissue shrinkage occurs after holding cattle off feed and water. It also occurs when cattle are subjected to stresses such as hauling. It becomes more important than excretory shrink the longer the shipping time. Since it is actual loss of tissue weight, it is harder to replace.

Easy handling during the loading process and minimizing quick starts and stops in the hauling process can reduce shrinkage. Most of the shrinkage occurs during loading and in the first part (25 miles) of a trip. Cattle may lose half as much in 25 miles as they do in 200 miles. As the time increases, so does shrinkage, but at a slower rate than the first few miles.

Professional cattle buyers may ask for a pencil shrink on cattle weighed on the farm, on a truck or after a very short haul from the farm to the scales. Pencil shrink is a percentage deduction from the weight of the cattle. This makes the weighing condition similar to cattle that were processed through a market. Pencil shrink is usually 2 to 3 percent for feeder cattle and 3 to 4 percent for finished cattle.

Difference in shrinkage between steers and heifers is variable but heifers shrink slightly more. Finished cattle shrink more than feeder cattle in the first eight to 10 hours. Feeder cattle shrink about 2 percent more on long hauls, up to 7 or 9 percent. An overnight stand of 12 hours without feed or water can cause 4 percent shrink in cattle on lush grass or silage. The same cattle on a high grain ration may lose only 2.5 to 3 percent.

Length of Shrink Period. Cattle begin to lose body weight (BW) at the time they are moved; the greatest proportion of BW loss occurs during the early hours (h) of feed and water deprivation. Coffey et al. (4) reported that steers that were gathered at daybreak from pasture and placed in holding pens without feed or water shrank at a rate of 1.25% of BW/h during the first 2 to 2.5 h, 0.61% of BW/h during the next 2.5 to 3 h, and only 0.16% of BW/h during the next 2-h period. In that study, almost one-half of the BW loss occurred during the first 2 to 2.5 h. Therefore, shrink is generally greater early in the feed and water deprivation period and appears to range from about 0.75 to 1.25% of BW/h during the first 3 to 4 h.

Environmental Conditions. Self and Gay (11) reported a tendency for stocker calves to shrink more when shipped in the summer compared with those shipped in the fall or spring if the calves were shipped directly from the farm to the feedlot. Feedlot cattle have also been reported to have a tendency to shrink more during the summer and fall compared with those shipped during the winter and spring (6). Both fecal and urine outputs were actually lower when ambient temperature was higher. Therefore, the increased BW lost during higher ambient temperatures is a result of a greater proportion of respiratory loss, presumably at the expense of fluid from body tissue (11). It is concluded that shrink under higher ambient temperatures is therefore much more serious and also costly to the cattlemen receiving the cattle.

The composition of the BW loss and the impact of the stresses on long-term animal health and performance are as critical as the actual BW losses themselves. Cole et al. (5) reported greater nitrogen loss from both the urine and feces in transported calves compared with non-transported fasted calves.

Effect of Handling Procedures. Self and Gay (11) indicated that cattle shrank less when they were handled as quietly as possible upon removal from pasture. A typical research practice is to weigh pasture cattle on 2 consecutive d to arrive at a beginning and ending BW for studies. Cattle that are hard to remove from pasture (i.e., more excited during pasture removal) typically weigh less on the second day than cattle that are easily removed from their pasture and handled more calmly. It is believed that handling procedures that create more stress on cattle will have a negative impact on cattle BW, shrink, and recovery time.

Effect of Previous Diet. Many producers feed grain prior to shipment to help cattle retain BW and reduce shrink. However, definitive research evaluating pre-shipment diets and management has produced variable results. Based on the summary information in the article, it is questionable whether feeding concentrate prior to shipment will reduce shrink.

Effect of Preconditioning. Preconditioning has been used in an attempt to provide better quality cattle at the livestock auction through reduced sickness and subsequent medical expenses; however, a consistent reduction in shrink should not always be expected based on available data.

Effect of Feed Additives. Certain feed additives may have an impact on feed intake, fill, and mineral status, and these factors may also impact shrink. Feeding ionophores for extended periods before shipment may help reduce shrink.

Forage Effects. The time of the morning that cattle are removed from pasture before weighing can have an impact on both their BW and the amount of shrink they incur. Heitschmidt (7) reported that cows grazing native range were 2.5% heavier in late morning than in early morning. In another grazing study, steers were removed from pasture at different times of the morning during the fall (4). Steers that were allowed to graze 3 h before gathering were 1.9% heavier than those gathered at daybreak. Rate of cattle shrink throughout the day was also affected by length of morning grazing before removal from pasture (4). Steers allowed to graze for 3 h before removal from pasture shrank at a rate of 0.86%/h less during the first 2.2 to 2.6 h following removal from pasture than those steers removed as grazing began at daybreak. Cumulative rate of shrink at any length of time following pasture removal, as well as total shrink, was lowest from steers allowed to graze for 3 h before being gathered from pasture. Therefore, allowing cattle to graze for an extended period before shipping not only allows them to gain additional BW, but also reduces their rate of shrink during the early shrink period.

Dietary Manipulation of Shrink. Hutcheson et al. (8) reported a positive response to supplemental potassium in the receiving. Cattle given either an electrolyte solution or glucose solution in the drinking water before slaughter had improved meat quality traits and carcass yield compared with those given no water or water only (9). Electrolyte supplementation before slaughter also reduced urine concentrations of sodium and potassium and increased urine chloride concentration, indicating that electrolyte supplementation during this time reduced the normal response of electrolyte elimination into the urine during transportation and fasting. In another study, cattle provided an electrolyte solution during holding for slaughter retained a greater percentage of live BW as carcass weight (10). Others have reported a response to supplemental chromium (3) in receiving diets, indicating that the body may be eliminating this element during transportation as well. Therefore, it appears possible to provide animals with a diet balanced for energy, protein, and electrolytes before transport that would help reduce shrink by providing storage of essential nutrients. However, this hypothesis needs to be evaluated because the body tends to reject and eliminate nutrients provided in excess.

Literature Cited:

1. Brazle, F. K. 1992. Effect of feed additives on shipping shrinkage of yearling heifers. Rep. Prog. 651. p 82. Kansas Agric. Exp. Stn., Manhattan, KS.

2. Brazle, F. K., G. L. Kuhl, C. E. Binns, K. O. Zoellner, L. R. Corah, and R. R. Schalles. 1991. The influence of limited-creep feeding on preand post-weaning performance of springborn calves. J. Anim. Sci. 69 (Suppl. 1):76 (Abs.).

3. Chang, X., and D. N. Mowat. 1992. Supplemental chromium for stressed and growing feeder calves. J. Anim. Sci. 70:559.

4. Coffey, K. P., F. K. Brazle, J. J. Higgins, and J. L. Moyer. 1997. Effects of gathering time on weight and shrink of steers grazing smooth bromegrass pastures. Prof. Anim. Sci. 13:170.

5. Cole, N. A., W. A. Phillips, and D. P. Hutcheson. 1986. The effect of pre-fast diet and transport on nitrogen metabolism of calves. J. Anim. Sci. 62:1719.

6. Harman, B. R., M. H. Brinkman, M. P. Hoffman, and H. L. Self. 1989. Factors affecting in-transit shrink and liver abscesses in fed steers. J. Anim. Sci. 67:311.

7. Heitschmidt, R. K. 1982. Diurnal variation in weight and rates of shrink of range cows and calves. J. Range Manage. 35:717.

8. Hutcheson, D. P., N. A. Cole, and J. B. McLaren. 1984. Effects of pretransit diets and post-transit potassium levels for feeder calves. J. Anim. Sci. 58:700.

9. Schaefer, A. L., S. D. M. Jones, A. K. W. Tong, and B. A. Young. 1990. Effects of transport and electrolyte supplementation on ion concentrations, carcass yield and quality in bulls. Can. J. Anim. Sci. 70:107.

10. Schaefer, A. L., S. D. M. Jones, A. K. W. Tong, B. A. Young, N. L. Murray, and P. Lepage. 1992. Effects of post-transport electrolyte supplementation on tissue electrolytes, hematology, urine osmolality and weight loss in beef bulls. Livestock Prod. Sci. 30:333.11. Self, H. L., and N. Gay. 1972. Shrink during shipment of feeder cattle. J. Anim. Sci. 35:489.