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Effects of Gathering Time on Weight and Shrink of Steers Grazing Smooth Bromegrass Pastures1
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al. The Professional Coffey AnimaletScientist 13:170–175
Effects of Gathering Time on Weight and Shrink of Steers Grazing Smooth Bromegrass Pastures1
K. P. COFFEY2, PAS, F. K. BRAZLE3, PAS, J. J. HIGGINS4, and J. L. MOYER Kansas State University, Southeast Agricultural Research Center, Parsons, KS 67357
Abstract
purchased (P)] were allotted into eight replicates. Two replicates within each Two studies having 4 × 4 Latin source received a control mineral mixture square designs were conducted to quanand two received a mineral mixture tify the effect of different gathering times containing lasalocid (1.3 mg/g). Gatheron weight of steers grazing smooth ing times were arranged in two Latin bromegrass pastures. Initial and final squares, one for each mineral mixture. weights were measured following a 16-h Following the last assigned weighing, removal from feed and water. An steers were held in pens without feed or intensive weighing period followed 3 to 4 water and weighed at 2- to 3-h intervals d after the initial shrunk weight in which until 1500 h. Weights of KSU steers all steers were weighed either at grazing (calm disposition) were 6 kg higher at initiation (T0; 0700 h in Exp. 1 and T3 than at T0, but weights of P steers 0615 h in Exp. 2) and 1 (T1), 2 (T2), or did not differ (P<0.10) across gathering 3 (T3) h later on 4 separate d with a 2times. Steers gathered at T3 lost weight to 3-d interval between weighings. In at a slower (P<0.05) rate (percentage per Exp. 1 (September 24 to October 7, hour) during the first 2 to 3 h following 1992), 37 steers were allotted into four gathering (P<0.05) and by 1500 h replicates. Steers gathered at T3 weighed (P=0.05) than those gathered at the 7 kg more (P<0.05) than those gathered other times. Gathering time had at T0. In Exp. 2 (June 24 to July 13, significant impacts on live weight and 1993), 72 steers from two sources shrink of grazing cattle in these studies. [Kansas State University (KSU) and (Key Words: beef cattle, grazing, weight, shrink.) 1Contribution
No. 96-538-J from the Kansas Agric. Exp. Sta., Manhattan, KS 66506.
2Corresponding
Introduction Cattle typically graze during two
author. Present address: E- to four distinct periods of the day, 209 Animal Science Bldg.; Univ. of Arkansas; depending on factors such as forage Fayetteville, AR 72701. type and environmental conditions
3Kansas
State University, Southeast Area Ex- (5, 14). The early morning period is tension Office, Chanute, KS 66720. generally one of the major grazing 4Dept. of Statistics, Manhattan, KS 66506. periods (5). Heitschmidt (8) reported Reviewed by E. E. Hatfield and R. Lemenager. that cows weighed in late morning
were 2.5% heavier than those weighed in early morning because of increased fill. Therefore, allowing stocker cattle to graze during the early morning period prior to gathering them for weighing and selling should therefore increase cattle weight. Differences in forage quality may affect organic matter fill (10) and cattle shrink (3). Other factors affecting cattle shrink include length of shrink (2, 8); previous diet (9,11); and feed additives (1). Little information is available on how differences in fill resulting from delayed gathering of cattle from pasture affect shrink. This experiment was conducted to help determine the magnitude of impact that lasalocid and/or gathering cattle from pastures at different times during the early morning grazing period has on their weights and subsequent shrink.
Materials and Methods Experiment 1. Thirty-seven crossbred steer calves (373 kg avg. BW) that grazed smooth bromegrass pastures during the spring and summer months were commingled and weighed on the morning of September 24 following a 16-h removal from feed and water to determine initial shrunk weight. The steers then were allotted by weight in
Gathering Time Effects on Weight and Shrink of Steers
a random stratified manner into three groups of 9 head and one group of 10 head and placed on one of four smooth bromegrass pastures. Steers were then weighed without prior removal from pasture or water on September 28 and 30 and October 2 and 5 using a 4 × 4 Latin square design (4). On each day of weighing, each group of steers was weighed only once at either 0715 (T0), 0815 (T1), 0915 (T2), or 1015 h (T3). Also, each group of steers was weighed at a different time on each of the 4 weighing d. Grazing initiated at approximately 0700 h on each of these days, but 0715 h was as early as the animals could be observed well enough to remove them from pasture by horseback. Thus, these times were chosen to represent the approximate time of grazing initiation or 1, 2, or 3 h following the initiation of grazing. All cattle were commingled and weighed on October 7 following a 16h removal from feed and water to determine final shrunk weight. Data were analyzed statistically using SAS® (13) GLM procedures for a Latin square design. Differences among gathering times were determined using a protected t test (15). The mathematical relationship between gathering time and animal weight and differential between full weights and the average of initial and final shrunk weights was determined using SAS® (13) REG procedures. Experiment 2. Forty mixed-breed purchased steers (P) and 32 Simmental × Angus crossbred steers from the Kansas State University herd (KSU) were allotted by weight in a random stratified manner to one of eight 4-ha smooth bromegrass pastures. One steer from the P group was added to each KSU group to equalize stocking rates across all pastures. Pastures were blocked such that two pastures grazed by each cattle source had natural shade consisting of a hedge row on the entire east end, and two pastures grazed by each cattle source had no shade. Within each of those combinations, steers grazing two pastures were offered free choice access to a control mineral mixture,
and steers grazing the two remaining pastures were offered free choice access to a mineral mixture containing lasalocid. The lasalocid treatment was formulated to provide 0.7 mg lasalocid/g of mineral mixture during the initial 25 d of the study. After 25 d (June 28), mineral consumption declined dramatically, and lasalocid level was increased to 1.3 mg lasalocid/g of mineral mixture during the remainder of the study. Steers were allotted to their respective pastures on June 3, 1993 and grazed the same pasture until October 1. All steers had previously grazed smooth bromegrass for at least 30 d prior to assignment to pasture treatments. All steers were removed from pasture on the afternoon of June 24, weighed individually, and placed in pens without feed or water for a 16-h shrink. Steers were weighed again beginning at 0800 h to determine overnight shrink. Steers then were weighed directly from pasture on June 28 and 30 and July 2 and 6 at either 0600 (T0), 0700 (T1), 0800 (T2), or 0900 h (T3) in two 4 × 4 Latin square designs, one for steers receiving the control mineral mixture, and the other for steers receiving the mineral mixture with lasalocid. This design was used to ensure that each group of steers was weighed only once each day and at different times on different weighing days and that one group receiving control and one receiving lasalocid were weighed at each weighing time. Following the weighing on July 6, steers were placed in pens without feed or water and weighed at approximately 2- to 3-h intervals until 1500 h. This was done to determine how lasalocid or gathering time would affect rate of shrink. The 1500 h time was chosen to mimic a standard time of sale in eastern Kansas sale barns. Because this was done on the last day of the morning weighings, the lasalocid effect was the only main effect equally represented at all four weighing times. On July 13, steers were weighed again following a 16-h shrink. Steers were weighed at the beginning and end of
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the weighing period following a 16-h shrink to provide weights in which fill was equalized and to allow us to calculate the fill gained during the weighing period. Steer weights at the different weighing times were analyzed statistically using SAS® (13) GLM procedures for a repeated measures analysis of variance (4). Effects of cattle source, mineral treatment, shade, and their two-way interactions were considered whole-plot effects and tested using cattle source × mineral × treatment × shade as the error term. Effect of weighing day, gathering time, and the two-way interactions of gathering time with cattle source, mineral treatment, and shade were analyzed as repeated measures factors and tested with the residual error. Because the effects of shade and cattle source were not represented equally at each gathering time on the last day (July 6), rate of shrink data were analyzed within each time period of the day with the effects of mineral treatment and gathering time in the model.
Results and Discussion Experiment 1. Steer weights and the weight difference between full weight and the average of two shrunk weights were greater (P<0.05) at T3 than at T0 or T1 (Table 1). Weight difference between full weights and average shrunk weights increased linearly (P<0.05) at a rate of 2.5 kg/h during the period up to 3 h following daybreak. Heitschmidt (8) reported that weight of lactating cows averaged 11 kg or 2.5% more in late morning than in early morning. Experiment 2. Interactions of mineral treatment or shade with gathering time were not detected (P<0.10) for steer weight or weight difference between full and average shrunk weights. Therefore, these main effects were averaged across gathering times and cattle sources and are presented in Table 2. Weight and weight differential of steers offered the control mineral did not differ (P<0.05) from those of steers
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Conversely, KSU steer weights and weight differential increased linearly TABLE 1. Effect of gathering time on full weight and differential be(P<0.01) at a rate of 2.8 kg/h with tween full and shrunk weight by stocker steers grazing smooth bromedelayed gathering time, such that grass pastures, Exp. 1. steers weighed at T3 were 6 kg heavier (P<0.10) than those gathered Gathering timea and weighed at T0. Steers of known origin (KSU) weighed more (P<0.10) Item T0 T1 T2 T3 SE at T1, T2, and T3 than P steers gathered at any of the four gathering times. Weight change from shrunk (kg) weights was greater (P<0.10) for KSU Avg. shrunk wt. 373 steers than for P steers at T1 and T3. Avg. full wt. 391c 392c 395bc 398b 1.4 Difference between full and This value represents fill and the shrunk wt. d 18c 19c 22bc 25b 1.4 ability of the cattle to regain fill following a shrink. The reason for aGathering times are at daybreak (T0) or 1 (T1), 2 (T2), or 3 h (T3) after daybreak. the differential response between b,cMeans within a row with no common superscript differ significantly (P<0.05). cattle sources probably can be attribdWeight differential between full and shrunk wt. increased linearly (P<0.01; r2 = uted to cattle disposition. Purchased steers were difficult to manage and 0.36) with later gathering times by the following equation: wt. difference = 17.0 + 2.5t, where t is the time in hours following daybreak. were excitable throughout the study during weighing operations. The tendency for certain animals to become behaviorally agitated during A cattle source × gathering time offered the mineral mixture with interaction was detected (P<0.10) for handling is persistent over time (7), lasalocid, and weight and weight leading to greater stress on those full weights measured between June differential of steers provided shade animals. Stress incurred during 28 and July 6 and for weight differdid not differ (P<0.05) from those of handling can reduce productivity ence from the average shrunk steers not provided shade. During weights (Table 3). Weights of P steers and impair rumen function (6). the time when the multiple Conversely, KSU steers were calm and did not differ (P<0.10) across gatherweighings were being conducted, moved quietly through the weighing ing times, and thus, their weight average lasalocid consumption was change from shrunk weights did not facilities and, therefore, incurred approximately 150 mg per head differ (P<0.10) across gathering times. little stress during the weighing daily. operations. Although one purchased steer was added to the KSU groups, these steers walked calmly into the TABLE 2. Average full weight and difference between full and 16-h working facilities and onto the scale, shrunk weight of steers grazing smooth bromegrass pastures with or stood calmly during weighing, and without shade and offered mineral mixtures with or without lasalocid, returned calmly to pasture. This Exp. 2a. ability to stay calm and return to their normal routine following a Treatmentb Shade period of shrink and handling is the most probable reason for the inItem L C No shade Shade SE creased fill acquired during the intensive weighing period. (kg) The rate of cattle shrink throughc out the day was affected by gathering Avg. full wt. 307 308 309 306 3.5 Difference between full and time (Table 4). Steers gathered at T3 shrunk wt.d 13 15 15 13 0.5 shrank at a slower (P<0.05) rate during the first period after gathering aNo significant differences were detected (P>0.05). them from pasture than those bL = mineral containing 1.3 mg/g laslocid; C = control mineral mixture. gathered at T0, T1, or T2. Steers cMeans are averaged across two cattle sources and four gathering times. gathered at T3 shrank at a faster rate (percentage per hour) during period 2 dDifference between the average of full wt. measured at different gathering times (next 1.9 to 2.7 h) than those gathand the average of shrunk wt. measured prior to and following the wt. measured at ered at T0 and T2, but cumulative different gathering times. rate of shrink across the first three
Gathering Time Effects on Weight and Shrink of Steers
TABLE 3. Average full weight and difference between full and 16-h shrunk weight of two cattle sources grazing on smooth bromegrass pastures and gathered at different times, Exp. 2. Gathering timea Item
T0
T1
T2
T3
SE
(kg) Avg. full wt. Purchased KSUf
304e 309cd
302e 310c
306de 311bc
302e 315b
1.6
Wt. difference Purchased KSUg
12d 14cd
10d 16c
14cd 17bc
10d 21b
1.6
aGathering
times are at daybreak (T0) or 1 (T1), 2 (T2), or 3 h (T3) after daybreak. within an item with no common superscript differ significantly
b,c,d,eMeans
(P<0.10). fWeight of KSU steers increased linearly (P<0.01; r2 = 0.43) with later gathering time by the following equation: wt = 307 + 2.8t, where t is the time in hours following daybreak. gWeight difference between full and shrunk weights of KSU steers increased linearly (P<0.01; r2 = 0.49) with later gathering times by the following equation: wt. difference = 12.5 + 2.8t, where t is time in hours following daybreak.
TABLE 4. Total and rate of shrink by steers grazing on smooth bromegrass pastures and gathered at different times, Exp. 2. Gathering timea Item
Periodb
T0
T1
T2
T3
SE
Shrink, %/h Shrink, %/h Shrink, %/h Shrink, %/h Shrink, %/h Total shrink, % Total shrink, %/h
1c 2g 1 to 2h 3i 1 to 3l to 1500 hm to 1500 h
1.25d 0.61e 0.89de 0.16k 0.67d 6.2d 0.69j
1.19d 0.96d 1.08d 0.02k 0.72d 5.9de 0.71j
1.05d 0.17f 0.71ef 0.59j 0.67d 5.0e 0.67j
0.39e 0.94d 0.64f 0.15k 0.50e 3.3f 0.50k
0.108 0.070 0.042 0.083 0.026 0.28 0.033
aGathering
times are at daybreak (T0) or 1 (T1), 2 (T2), or 3 h (T3) after daybreak. are designations for times following gathering the steers from pasture. cPeriod 1 is the first 2.2 to 2.6 h following gathering from pasture, except steers gathered at T2, for which period 1 was 3.4 h. d,e,fMeans within the same row with no common superscript differ significantly (P<0.05). gPeriod 2 is the next 1.9 to 2.7 h following period 1. hCumulative rate of shrink across periods 1 and 2. iPeriod 3 is the next 1.9 to 2.2 h following period 2. j,kMeans within the same row with no common superscript differ significantly (P<0.05). lCumulative rate of shrink across the first three periods. mTotal percentage shrink is based on the weight measured immediately upon gathering steers from pasture and a weight measured at approximately 1500 h. bPeriods
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periods following pasture removal was lower (P<0.05) from steers gathered at T3 than those gathered from pasture at T0, T1, or T2. Total shrink at 1500 h was 2.9 % per head less (P<0.05) and rate of shrink was 0.19%/h less (P=0.05) for steers gathered at T3 compared with those removed at the time grazing began (T0). Heitschmidt (8) reported that lactating range cows shrank at a rate of approximately 1.2%/h during the first 3 h of shrink, then at a rate of approximately 0.35%/h for the next 21 h. Brazle (2) reported that heifers (300 kg) shrank at a rate of 1%/h for the first 5 h, then declined to a rate of 0.7%/h during the next 5 h in the summer (32 to 35 °C). In this study, steers gathered from pasture at T0 and placed in holding pens without feed or water shrank at a rate of 1.25%/h during the first 2.3 h, 0.61%/h during the next 2.7 h, and only 0.16%/h during the next 2.1-h period. Of the total 6.2% shrink during a 9-h period, almost half (48%) of the weight loss occurred during the first 2 to 2.5 h. Therefore, factors that help reduce this initial shrink, such as a 3-h delay in gathering the cattle, could have a significant impact on cattle pay weight. Rate of shrink by steers offered the control mineral mixture did not differ (P<0.10) from that of steers offered the mineral mixture containing lasalocid during any of the periods up to 1500 h (Table 5). Again, average lasalocid consumption was 150 mg per head daily during the time when the multiple weighings were being conducted. Lasalocid previously has been shown to reduce total shrink of heifers transported 483 km (2). In that study, heifers fed lasalocid in a mineral mixture prior to shipment shrank 0.5% per head less than those fed a control mineral mixture. That magnitude of shrink reduction is comparable to the 0.4% per head less cumulative shrink observed in this study. These data may have significant impact both from practical and scientific viewpoints. Cattle sold at
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Coffey et al.
TABLE 5. Total and rate of shrink by steers grazing on smooth bromegrass pastures and offered a control or lasalocid mineral mixture, Exp. 2. Treatmenta Item
Periodb
Lasalocid
Control
SE
Shrink, %/h Shrink, %/h Shrink, %/h Shrink, %/h Shrink, %/h Total shrink, % Total shrink, %/h
1c 2d 1 to 2e 3f 1 to 3g to 1500 hh to 1500 h
0.91 0.68 0.81 0.19 0.62 4.9 0.62
1.03 0.66 0.85 0.27 0.67 5.3 0.67
0.076 0.049 0.029 0.058 0.019 0.20 0.023
may result in greater variation between weighing days but should result in all cattle having similar times of grazing allowance prior to being weighed and, therefore, at least standardize the fill at a particular weighing.
Acknowledgements The authors wish to express their appreciation to Farmland Industries, Inc. for providing the commercial mineral and lasalocid and to Bob Middleton and Larry Ellis for assistance with data collection.
aNo
significant differences were detected (P<0.05) between the main effects of lasalocid (1.3 mg/g) and control mineral when averaged across gathering times. bPeriods are designations for times following gathering the steers from pasture. cPeriod 1 is the first 2.2 to 2.6 h following gathering from pasture, except steers gathered at T2, for which period 1 was 3.4 h. dPeriod 2 is the next 1.9 to 2.7 h following period 1. eCumulative rate of shrink across periods 1 and 2. fPeriod 3 is the next 1.9 to 2.2 h following period 2. gCumulative rate of shrink across the first three periods. hTotal percentage shrink is based on the weight measured immediately upon gathering steers from pasture and water and a weight measured at approximately 1500 h.
livestock auctions typically are gathered early and taken to the auction to be sold later that afternoon or evening. Cattle producers that are able to allow their calves to graze for 3-h prior to transporting them to a salebarn may benefit from not only the additional weight gain, but also from the reduced rate and total amount of shrink incurred by time of sale. In grazing experiments, it is impossible to weigh all of the cattle at one time. Gathering them all at one time would result in some animals shrinking more than others prior to being weighed. Conversely, gathering cattle in some progressive order as they are weighed allows some cattle to graze longer in the morning than others. This can lead to differences in fill and consequently bias results. Shrinking cattle before weighing does not appear to solve the problem, because length of grazing time prior to gathering the
cattle may affect rate of and total shrink and, therefore, bias weights. Heitschmidt (8) concluded that shrinking cattle prior to weighing would not standardize weights unless length of shrink and environmental conditions during shrink were similar. Phillips et al. (12) reported a dramatic impact of environmental conditions on total shrink and the relative proportion and amount of shrink that are from either urine and fecal excretions or from tissue shrink. Brown (3) reported that both type and quality of forage that cattle consume prior to an overnight shrink may affect the amount of shrink. Forage quality also may have an affect on organic matter fill (10) and, therefore, confound gains when full weights are used to determine gains. Based on this information, we feel that using full weights with cattle being weighed on 2 d in a progressive order that is reversed on the 2nd d
Literature Cited 1. Brazle, F. K. 1991. The effect of feed additives on shrinkage of calves and yearlings. J. Anim. Sci. 69(Suppl. 1):51. (Abs.). 2. Brazle, F.K. 1992. Effect of feed additives on shipping shrinkage of yearling heifers. In Cattlemen’s Day 1992. p 82. Kansas Agric. Exp. Sta. Rept. of Prog. Manhattan, KS. 3. Brown, M. A., G. E. Aiken, A. H. Brown, Jr., W. G. Jackson, and J. R. Miesner. 1993. Evaluation of overnight shrinkage in reduction of variability of weights and gains of beef cattle. Prof. Anim. Sci. 9:120. 4. Cochran, W. G., and G. M. Cox. 1957. Experimental Designs. (2nd Ed.). p 117. John Wiley and Sons, Inc., New York, NY. 5. Coffey, K. P., J. L. Moyer, F. K. Brazle, and L. W. Lomas. 1992. Amount and diurnal distribution of grazing time by stocker cattle under different tall fescue management strategies. Appl. Anim. Behav. Sci. 33:121. 6. Grandin, T. 1989. Behavioral principles of livestock handling. Prof. Anim. Sci. 5(2):1. 7. Grandin, T. 1993. Behavioral agitation during handling of cattle is persistent over time. Appl. Anim. Behav. Sci. 36:1. 8. Heitschmidt, R. K. 1982. Diurnal variation in weight and rates of shrink of range cows and calves. J. Range Manage. 35:717. 9. 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. 10. Moyer, J. L., K. P. Coffey, F. K. Brazle, and J. E. Schneider. 1995. Forage intake, diet quality, and performance of stocker cattle grazing interseeded or monocultured rye and bermudagrass. Prof. Anim. Sci. 11:67.
Gathering Time Effects on Weight and Shrink of Steers
11. Phillips, W. A., N. A. Cole, and D. P. Hutcheson. 1983. The effect of the pretransit diet on the amount and source of weight lost by beef steers during transit. J. Anim. Sci. 57(Suppl. 1):405. (Abs.). 12. Phillips, W. A., D. L. VonTungeln, and P. E. Juniewicz. 1991. Fecal and urinary output by beef steers during a 48-h fast and fast plus transit. J. Anim. Sci. 69(Suppl. 1):51. (Abs.).
13. SAS Institute. 1988. SAS/STAT® User’s Guide. SAS Inst. Inc., Cary, NC. 14. Seman, D. H., J. A. Stuedemann, D. L. Breedlove, S. R. Wilkinson, D. P. Belesky, F. N. Thompson, and F. P. Stewart. 1990. Differences in grazing behavior of steers consuming endophyte infected or noninfected tall fescue. In Proc. Int. Symp. on Acremonium/Grass
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Interactions, 5 to 7 November, 1990. p 267. S. S. Quisenberry and R. E. Joost (Ed.). Louisiana Agricultural Experiment Station, Baton Rouge, LA. 15. Snedecor, G. W., and W. G. Cochran. 1980. Statistical Methods. (7th Ed.). The Iowa State Univ. Press, Ames, IA.
al. The Professional Coffey AnimaletScientist 13:170–175
Effects of Gathering Time on Weight and Shrink of Steers Grazing Smooth Bromegrass Pastures1
K. P. COFFEY2, PAS, F. K. BRAZLE3, PAS, J. J. HIGGINS4, and J. L. MOYER Kansas State University, Southeast Agricultural Research Center, Parsons, KS 67357
Abstract
purchased (P)] were allotted into eight replicates. Two replicates within each Two studies having 4 × 4 Latin source received a control mineral mixture square designs were conducted to quanand two received a mineral mixture tify the effect of different gathering times containing lasalocid (1.3 mg/g). Gatheron weight of steers grazing smooth ing times were arranged in two Latin bromegrass pastures. Initial and final squares, one for each mineral mixture. weights were measured following a 16-h Following the last assigned weighing, removal from feed and water. An steers were held in pens without feed or intensive weighing period followed 3 to 4 water and weighed at 2- to 3-h intervals d after the initial shrunk weight in which until 1500 h. Weights of KSU steers all steers were weighed either at grazing (calm disposition) were 6 kg higher at initiation (T0; 0700 h in Exp. 1 and T3 than at T0, but weights of P steers 0615 h in Exp. 2) and 1 (T1), 2 (T2), or did not differ (P<0.10) across gathering 3 (T3) h later on 4 separate d with a 2times. Steers gathered at T3 lost weight to 3-d interval between weighings. In at a slower (P<0.05) rate (percentage per Exp. 1 (September 24 to October 7, hour) during the first 2 to 3 h following 1992), 37 steers were allotted into four gathering (P<0.05) and by 1500 h replicates. Steers gathered at T3 weighed (P=0.05) than those gathered at the 7 kg more (P<0.05) than those gathered other times. Gathering time had at T0. In Exp. 2 (June 24 to July 13, significant impacts on live weight and 1993), 72 steers from two sources shrink of grazing cattle in these studies. [Kansas State University (KSU) and (Key Words: beef cattle, grazing, weight, shrink.) 1Contribution
No. 96-538-J from the Kansas Agric. Exp. Sta., Manhattan, KS 66506.
2Corresponding
Introduction Cattle typically graze during two
author. Present address: E- to four distinct periods of the day, 209 Animal Science Bldg.; Univ. of Arkansas; depending on factors such as forage Fayetteville, AR 72701. type and environmental conditions
3Kansas
State University, Southeast Area Ex- (5, 14). The early morning period is tension Office, Chanute, KS 66720. generally one of the major grazing 4Dept. of Statistics, Manhattan, KS 66506. periods (5). Heitschmidt (8) reported Reviewed by E. E. Hatfield and R. Lemenager. that cows weighed in late morning
were 2.5% heavier than those weighed in early morning because of increased fill. Therefore, allowing stocker cattle to graze during the early morning period prior to gathering them for weighing and selling should therefore increase cattle weight. Differences in forage quality may affect organic matter fill (10) and cattle shrink (3). Other factors affecting cattle shrink include length of shrink (2, 8); previous diet (9,11); and feed additives (1). Little information is available on how differences in fill resulting from delayed gathering of cattle from pasture affect shrink. This experiment was conducted to help determine the magnitude of impact that lasalocid and/or gathering cattle from pastures at different times during the early morning grazing period has on their weights and subsequent shrink.
Materials and Methods Experiment 1. Thirty-seven crossbred steer calves (373 kg avg. BW) that grazed smooth bromegrass pastures during the spring and summer months were commingled and weighed on the morning of September 24 following a 16-h removal from feed and water to determine initial shrunk weight. The steers then were allotted by weight in
Gathering Time Effects on Weight and Shrink of Steers
a random stratified manner into three groups of 9 head and one group of 10 head and placed on one of four smooth bromegrass pastures. Steers were then weighed without prior removal from pasture or water on September 28 and 30 and October 2 and 5 using a 4 × 4 Latin square design (4). On each day of weighing, each group of steers was weighed only once at either 0715 (T0), 0815 (T1), 0915 (T2), or 1015 h (T3). Also, each group of steers was weighed at a different time on each of the 4 weighing d. Grazing initiated at approximately 0700 h on each of these days, but 0715 h was as early as the animals could be observed well enough to remove them from pasture by horseback. Thus, these times were chosen to represent the approximate time of grazing initiation or 1, 2, or 3 h following the initiation of grazing. All cattle were commingled and weighed on October 7 following a 16h removal from feed and water to determine final shrunk weight. Data were analyzed statistically using SAS® (13) GLM procedures for a Latin square design. Differences among gathering times were determined using a protected t test (15). The mathematical relationship between gathering time and animal weight and differential between full weights and the average of initial and final shrunk weights was determined using SAS® (13) REG procedures. Experiment 2. Forty mixed-breed purchased steers (P) and 32 Simmental × Angus crossbred steers from the Kansas State University herd (KSU) were allotted by weight in a random stratified manner to one of eight 4-ha smooth bromegrass pastures. One steer from the P group was added to each KSU group to equalize stocking rates across all pastures. Pastures were blocked such that two pastures grazed by each cattle source had natural shade consisting of a hedge row on the entire east end, and two pastures grazed by each cattle source had no shade. Within each of those combinations, steers grazing two pastures were offered free choice access to a control mineral mixture,
and steers grazing the two remaining pastures were offered free choice access to a mineral mixture containing lasalocid. The lasalocid treatment was formulated to provide 0.7 mg lasalocid/g of mineral mixture during the initial 25 d of the study. After 25 d (June 28), mineral consumption declined dramatically, and lasalocid level was increased to 1.3 mg lasalocid/g of mineral mixture during the remainder of the study. Steers were allotted to their respective pastures on June 3, 1993 and grazed the same pasture until October 1. All steers had previously grazed smooth bromegrass for at least 30 d prior to assignment to pasture treatments. All steers were removed from pasture on the afternoon of June 24, weighed individually, and placed in pens without feed or water for a 16-h shrink. Steers were weighed again beginning at 0800 h to determine overnight shrink. Steers then were weighed directly from pasture on June 28 and 30 and July 2 and 6 at either 0600 (T0), 0700 (T1), 0800 (T2), or 0900 h (T3) in two 4 × 4 Latin square designs, one for steers receiving the control mineral mixture, and the other for steers receiving the mineral mixture with lasalocid. This design was used to ensure that each group of steers was weighed only once each day and at different times on different weighing days and that one group receiving control and one receiving lasalocid were weighed at each weighing time. Following the weighing on July 6, steers were placed in pens without feed or water and weighed at approximately 2- to 3-h intervals until 1500 h. This was done to determine how lasalocid or gathering time would affect rate of shrink. The 1500 h time was chosen to mimic a standard time of sale in eastern Kansas sale barns. Because this was done on the last day of the morning weighings, the lasalocid effect was the only main effect equally represented at all four weighing times. On July 13, steers were weighed again following a 16-h shrink. Steers were weighed at the beginning and end of
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the weighing period following a 16-h shrink to provide weights in which fill was equalized and to allow us to calculate the fill gained during the weighing period. Steer weights at the different weighing times were analyzed statistically using SAS® (13) GLM procedures for a repeated measures analysis of variance (4). Effects of cattle source, mineral treatment, shade, and their two-way interactions were considered whole-plot effects and tested using cattle source × mineral × treatment × shade as the error term. Effect of weighing day, gathering time, and the two-way interactions of gathering time with cattle source, mineral treatment, and shade were analyzed as repeated measures factors and tested with the residual error. Because the effects of shade and cattle source were not represented equally at each gathering time on the last day (July 6), rate of shrink data were analyzed within each time period of the day with the effects of mineral treatment and gathering time in the model.
Results and Discussion Experiment 1. Steer weights and the weight difference between full weight and the average of two shrunk weights were greater (P<0.05) at T3 than at T0 or T1 (Table 1). Weight difference between full weights and average shrunk weights increased linearly (P<0.05) at a rate of 2.5 kg/h during the period up to 3 h following daybreak. Heitschmidt (8) reported that weight of lactating cows averaged 11 kg or 2.5% more in late morning than in early morning. Experiment 2. Interactions of mineral treatment or shade with gathering time were not detected (P<0.10) for steer weight or weight difference between full and average shrunk weights. Therefore, these main effects were averaged across gathering times and cattle sources and are presented in Table 2. Weight and weight differential of steers offered the control mineral did not differ (P<0.05) from those of steers
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Conversely, KSU steer weights and weight differential increased linearly TABLE 1. Effect of gathering time on full weight and differential be(P<0.01) at a rate of 2.8 kg/h with tween full and shrunk weight by stocker steers grazing smooth bromedelayed gathering time, such that grass pastures, Exp. 1. steers weighed at T3 were 6 kg heavier (P<0.10) than those gathered Gathering timea and weighed at T0. Steers of known origin (KSU) weighed more (P<0.10) Item T0 T1 T2 T3 SE at T1, T2, and T3 than P steers gathered at any of the four gathering times. Weight change from shrunk (kg) weights was greater (P<0.10) for KSU Avg. shrunk wt. 373 steers than for P steers at T1 and T3. Avg. full wt. 391c 392c 395bc 398b 1.4 Difference between full and This value represents fill and the shrunk wt. d 18c 19c 22bc 25b 1.4 ability of the cattle to regain fill following a shrink. The reason for aGathering times are at daybreak (T0) or 1 (T1), 2 (T2), or 3 h (T3) after daybreak. the differential response between b,cMeans within a row with no common superscript differ significantly (P<0.05). cattle sources probably can be attribdWeight differential between full and shrunk wt. increased linearly (P<0.01; r2 = uted to cattle disposition. Purchased steers were difficult to manage and 0.36) with later gathering times by the following equation: wt. difference = 17.0 + 2.5t, where t is the time in hours following daybreak. were excitable throughout the study during weighing operations. The tendency for certain animals to become behaviorally agitated during A cattle source × gathering time offered the mineral mixture with interaction was detected (P<0.10) for handling is persistent over time (7), lasalocid, and weight and weight leading to greater stress on those full weights measured between June differential of steers provided shade animals. Stress incurred during 28 and July 6 and for weight differdid not differ (P<0.05) from those of handling can reduce productivity ence from the average shrunk steers not provided shade. During weights (Table 3). Weights of P steers and impair rumen function (6). the time when the multiple Conversely, KSU steers were calm and did not differ (P<0.10) across gatherweighings were being conducted, moved quietly through the weighing ing times, and thus, their weight average lasalocid consumption was change from shrunk weights did not facilities and, therefore, incurred approximately 150 mg per head differ (P<0.10) across gathering times. little stress during the weighing daily. operations. Although one purchased steer was added to the KSU groups, these steers walked calmly into the TABLE 2. Average full weight and difference between full and 16-h working facilities and onto the scale, shrunk weight of steers grazing smooth bromegrass pastures with or stood calmly during weighing, and without shade and offered mineral mixtures with or without lasalocid, returned calmly to pasture. This Exp. 2a. ability to stay calm and return to their normal routine following a Treatmentb Shade period of shrink and handling is the most probable reason for the inItem L C No shade Shade SE creased fill acquired during the intensive weighing period. (kg) The rate of cattle shrink throughc out the day was affected by gathering Avg. full wt. 307 308 309 306 3.5 Difference between full and time (Table 4). Steers gathered at T3 shrunk wt.d 13 15 15 13 0.5 shrank at a slower (P<0.05) rate during the first period after gathering aNo significant differences were detected (P>0.05). them from pasture than those bL = mineral containing 1.3 mg/g laslocid; C = control mineral mixture. gathered at T0, T1, or T2. Steers cMeans are averaged across two cattle sources and four gathering times. gathered at T3 shrank at a faster rate (percentage per hour) during period 2 dDifference between the average of full wt. measured at different gathering times (next 1.9 to 2.7 h) than those gathand the average of shrunk wt. measured prior to and following the wt. measured at ered at T0 and T2, but cumulative different gathering times. rate of shrink across the first three
Gathering Time Effects on Weight and Shrink of Steers
TABLE 3. Average full weight and difference between full and 16-h shrunk weight of two cattle sources grazing on smooth bromegrass pastures and gathered at different times, Exp. 2. Gathering timea Item
T0
T1
T2
T3
SE
(kg) Avg. full wt. Purchased KSUf
304e 309cd
302e 310c
306de 311bc
302e 315b
1.6
Wt. difference Purchased KSUg
12d 14cd
10d 16c
14cd 17bc
10d 21b
1.6
aGathering
times are at daybreak (T0) or 1 (T1), 2 (T2), or 3 h (T3) after daybreak. within an item with no common superscript differ significantly
b,c,d,eMeans
(P<0.10). fWeight of KSU steers increased linearly (P<0.01; r2 = 0.43) with later gathering time by the following equation: wt = 307 + 2.8t, where t is the time in hours following daybreak. gWeight difference between full and shrunk weights of KSU steers increased linearly (P<0.01; r2 = 0.49) with later gathering times by the following equation: wt. difference = 12.5 + 2.8t, where t is time in hours following daybreak.
TABLE 4. Total and rate of shrink by steers grazing on smooth bromegrass pastures and gathered at different times, Exp. 2. Gathering timea Item
Periodb
T0
T1
T2
T3
SE
Shrink, %/h Shrink, %/h Shrink, %/h Shrink, %/h Shrink, %/h Total shrink, % Total shrink, %/h
1c 2g 1 to 2h 3i 1 to 3l to 1500 hm to 1500 h
1.25d 0.61e 0.89de 0.16k 0.67d 6.2d 0.69j
1.19d 0.96d 1.08d 0.02k 0.72d 5.9de 0.71j
1.05d 0.17f 0.71ef 0.59j 0.67d 5.0e 0.67j
0.39e 0.94d 0.64f 0.15k 0.50e 3.3f 0.50k
0.108 0.070 0.042 0.083 0.026 0.28 0.033
aGathering
times are at daybreak (T0) or 1 (T1), 2 (T2), or 3 h (T3) after daybreak. are designations for times following gathering the steers from pasture. cPeriod 1 is the first 2.2 to 2.6 h following gathering from pasture, except steers gathered at T2, for which period 1 was 3.4 h. d,e,fMeans within the same row with no common superscript differ significantly (P<0.05). gPeriod 2 is the next 1.9 to 2.7 h following period 1. hCumulative rate of shrink across periods 1 and 2. iPeriod 3 is the next 1.9 to 2.2 h following period 2. j,kMeans within the same row with no common superscript differ significantly (P<0.05). lCumulative rate of shrink across the first three periods. mTotal percentage shrink is based on the weight measured immediately upon gathering steers from pasture and a weight measured at approximately 1500 h. bPeriods
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periods following pasture removal was lower (P<0.05) from steers gathered at T3 than those gathered from pasture at T0, T1, or T2. Total shrink at 1500 h was 2.9 % per head less (P<0.05) and rate of shrink was 0.19%/h less (P=0.05) for steers gathered at T3 compared with those removed at the time grazing began (T0). Heitschmidt (8) reported that lactating range cows shrank at a rate of approximately 1.2%/h during the first 3 h of shrink, then at a rate of approximately 0.35%/h for the next 21 h. Brazle (2) reported that heifers (300 kg) shrank at a rate of 1%/h for the first 5 h, then declined to a rate of 0.7%/h during the next 5 h in the summer (32 to 35 °C). In this study, steers gathered from pasture at T0 and placed in holding pens without feed or water shrank at a rate of 1.25%/h during the first 2.3 h, 0.61%/h during the next 2.7 h, and only 0.16%/h during the next 2.1-h period. Of the total 6.2% shrink during a 9-h period, almost half (48%) of the weight loss occurred during the first 2 to 2.5 h. Therefore, factors that help reduce this initial shrink, such as a 3-h delay in gathering the cattle, could have a significant impact on cattle pay weight. Rate of shrink by steers offered the control mineral mixture did not differ (P<0.10) from that of steers offered the mineral mixture containing lasalocid during any of the periods up to 1500 h (Table 5). Again, average lasalocid consumption was 150 mg per head daily during the time when the multiple weighings were being conducted. Lasalocid previously has been shown to reduce total shrink of heifers transported 483 km (2). In that study, heifers fed lasalocid in a mineral mixture prior to shipment shrank 0.5% per head less than those fed a control mineral mixture. That magnitude of shrink reduction is comparable to the 0.4% per head less cumulative shrink observed in this study. These data may have significant impact both from practical and scientific viewpoints. Cattle sold at
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TABLE 5. Total and rate of shrink by steers grazing on smooth bromegrass pastures and offered a control or lasalocid mineral mixture, Exp. 2. Treatmenta Item
Periodb
Lasalocid
Control
SE
Shrink, %/h Shrink, %/h Shrink, %/h Shrink, %/h Shrink, %/h Total shrink, % Total shrink, %/h
1c 2d 1 to 2e 3f 1 to 3g to 1500 hh to 1500 h
0.91 0.68 0.81 0.19 0.62 4.9 0.62
1.03 0.66 0.85 0.27 0.67 5.3 0.67
0.076 0.049 0.029 0.058 0.019 0.20 0.023
may result in greater variation between weighing days but should result in all cattle having similar times of grazing allowance prior to being weighed and, therefore, at least standardize the fill at a particular weighing.
Acknowledgements The authors wish to express their appreciation to Farmland Industries, Inc. for providing the commercial mineral and lasalocid and to Bob Middleton and Larry Ellis for assistance with data collection.
aNo
significant differences were detected (P<0.05) between the main effects of lasalocid (1.3 mg/g) and control mineral when averaged across gathering times. bPeriods are designations for times following gathering the steers from pasture. cPeriod 1 is the first 2.2 to 2.6 h following gathering from pasture, except steers gathered at T2, for which period 1 was 3.4 h. dPeriod 2 is the next 1.9 to 2.7 h following period 1. eCumulative rate of shrink across periods 1 and 2. fPeriod 3 is the next 1.9 to 2.2 h following period 2. gCumulative rate of shrink across the first three periods. hTotal percentage shrink is based on the weight measured immediately upon gathering steers from pasture and water and a weight measured at approximately 1500 h.
livestock auctions typically are gathered early and taken to the auction to be sold later that afternoon or evening. Cattle producers that are able to allow their calves to graze for 3-h prior to transporting them to a salebarn may benefit from not only the additional weight gain, but also from the reduced rate and total amount of shrink incurred by time of sale. In grazing experiments, it is impossible to weigh all of the cattle at one time. Gathering them all at one time would result in some animals shrinking more than others prior to being weighed. Conversely, gathering cattle in some progressive order as they are weighed allows some cattle to graze longer in the morning than others. This can lead to differences in fill and consequently bias results. Shrinking cattle before weighing does not appear to solve the problem, because length of grazing time prior to gathering the
cattle may affect rate of and total shrink and, therefore, bias weights. Heitschmidt (8) concluded that shrinking cattle prior to weighing would not standardize weights unless length of shrink and environmental conditions during shrink were similar. Phillips et al. (12) reported a dramatic impact of environmental conditions on total shrink and the relative proportion and amount of shrink that are from either urine and fecal excretions or from tissue shrink. Brown (3) reported that both type and quality of forage that cattle consume prior to an overnight shrink may affect the amount of shrink. Forage quality also may have an affect on organic matter fill (10) and, therefore, confound gains when full weights are used to determine gains. Based on this information, we feel that using full weights with cattle being weighed on 2 d in a progressive order that is reversed on the 2nd d
Literature Cited 1. Brazle, F. K. 1991. The effect of feed additives on shrinkage of calves and yearlings. J. Anim. Sci. 69(Suppl. 1):51. (Abs.). 2. Brazle, F.K. 1992. Effect of feed additives on shipping shrinkage of yearling heifers. In Cattlemen’s Day 1992. p 82. Kansas Agric. Exp. Sta. Rept. of Prog. Manhattan, KS. 3. Brown, M. A., G. E. Aiken, A. H. Brown, Jr., W. G. Jackson, and J. R. Miesner. 1993. Evaluation of overnight shrinkage in reduction of variability of weights and gains of beef cattle. Prof. Anim. Sci. 9:120. 4. Cochran, W. G., and G. M. Cox. 1957. Experimental Designs. (2nd Ed.). p 117. John Wiley and Sons, Inc., New York, NY. 5. Coffey, K. P., J. L. Moyer, F. K. Brazle, and L. W. Lomas. 1992. Amount and diurnal distribution of grazing time by stocker cattle under different tall fescue management strategies. Appl. Anim. Behav. Sci. 33:121. 6. Grandin, T. 1989. Behavioral principles of livestock handling. Prof. Anim. Sci. 5(2):1. 7. Grandin, T. 1993. Behavioral agitation during handling of cattle is persistent over time. Appl. Anim. Behav. Sci. 36:1. 8. Heitschmidt, R. K. 1982. Diurnal variation in weight and rates of shrink of range cows and calves. J. Range Manage. 35:717. 9. 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. 10. Moyer, J. L., K. P. Coffey, F. K. Brazle, and J. E. Schneider. 1995. Forage intake, diet quality, and performance of stocker cattle grazing interseeded or monocultured rye and bermudagrass. Prof. Anim. Sci. 11:67.
Gathering Time Effects on Weight and Shrink of Steers
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Interactions, 5 to 7 November, 1990. p 267. S. S. Quisenberry and R. E. Joost (Ed.). Louisiana Agricultural Experiment Station, Baton Rouge, LA. 15. Snedecor, G. W., and W. G. Cochran. 1980. Statistical Methods. (7th Ed.). The Iowa State Univ. Press, Ames, IA.