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The relationship of feeding behavior to residual feed intake in crossbred Angus steers fed traditional and no-roughage diets¹

Division of Animal Sciences, University of Missouri, Columbia 65211

	Abstract

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION LITERATURE CITED

 
Two studies were conducted to determine the relationship of feeding behavior to a phenotypic expression of residual feed intake (RFI), a measure of efficiency. In Exp. 1, a feedlot diet containing roughage was fed (traditional). In Exp. 2, a no-roughage diet was fed. Residual feed intake, a measure of feed efficiency, was calculated for both studies. In Exp. 1, six feed-efficient (low RFI) steers and six feed-inefficient steers (high RFI) were selected from a contemporary group of 80 steers, and feeding behaviors were analyzed. In Exp. 2, nine feed-efficient and eight feed-inefficient steers were selected from a contemporary group of 40 steers. There were no differences (P > 0.13) in initial or final BW or ADG between efficient and inefficient groups in either Exp. 1 or 2. In Exp. 1, DMI and average eating bouts daily differed (P < 0.001), with efficient steers consuming less feed and eating fewer times per day. In Exp. 2, efficient steers consumed less (P < 0.001) feed, and average eating bouts daily tended (P = 0.07) to be fewer in efficient animals. Limited differences were noted in feeding behavior between groups, with inefficient steers from both studies having a more variable eating pattern throughout the day. The average daily eating rate did not differ (P > 0.20) between groups in either experiment. The average number of days comprising a feeding pattern for both efficiency groups in Exp. 1 and 2 was found to be 2 to 3 d and multiples of 2 to 3 d. In Exp. 1, the feed intake pattern of efficient and inefficient steers changed once they reached a BW of approximately 391 and 381 kg, respectively. This occurred near d 47 for the efficient steers and near d 32 for inefficient steers. In Exp. 2, the feed intake pattern of both efficient and inefficient steers changed once they reached a BW of approximately 399 kg, which occurred on d 31 for the efficient steers and on d 33 for the inefficient steers. From the measured variables, there were no differences in growth and limited differences noted in feeding behavior between efficient and inefficient groups. The results of the trials suggest increased variability of feed intake throughout the day for inefficient animals.

Key Words: beef cattle • efficiency • feeding behavior • residual feed intake

	INTRODUCTION

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION LITERATURE CITED

 
Over the past few decades, improvements have been made in growth and gain efficiency [which is the reciprocal of the efficiency of gain (G:F)] of cattle. These improvements were made possible using intense selection criteria for the improvement of growth and through the improvement of diet formulation models. Even with these improvements, there exists significant variation in the phenotypic expression of efficiency. Until recently, the task of collecting and analyzing individual feed intakes proved cumbersome and expensive, and thus most selection criterion were based on the improvement of growth, which was easier and less expensive to measure. Innovative and robust technologies, however, have not only made the collection of individual feed intakes and assessments of individual efficiencies much easier and less expensive, but they have also allowed for more expansive research in determining and understanding the variables linked to the phenotypic expression of efficiency.

There are studies that have measured feeding behavior of individual feedlot animals and its relation to measured output or growth (Sowell et al., 1998; Pritchard and Bruns, 2003; Schwartzkopf-Genswein et al., 2003), and there are studies that have indicated that intake patterns differ markedly among individuals within a pen (Gibb et al., 1998; Hickman et al., 2002; Schwartzkopf-Genswein et al., 2002). However, what is not fully known at this time is the relationship of efficiency to feeding behavior characteristics of feedlot animals consuming no-roughage diets and diets containing roughage. Therefore, the objective of this paper was to explain the relationship of feeding behavior to efficiency in steers fed traditional and no-roughage feedlot diets and to determine the potential to use behavior variables as indirect markers for the improvement of efficiency.

	MATERIALS AND METHODS

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION LITERATURE CITED

 
Feedlot Steers and Management–Growth and Behavior Study

The research protocols used in this study were approved by the University of Missouri Animal Care and Use Committee. In Exp. 1, eighty crossbred Angus steers (initial BW = 324 ± 27 kg) were randomly assigned to 1 of 8 partially covered pens upon arriving to the University of Missouri Beef Research Farm. In Exp. 2, fourty crossbred Angus steers (initial BW = 325 ± 24 kg) were randomly assigned to 1 of 4 partially covered pens. Each of the pens had the same dimensions (8 x 18 m) and were positioned in an east-to-west orientation, allowing for similar environmental conditions to be maintained between pens. Each of the pens had concrete flooring with approximately ¹/3 of each pen being covered by a sloped roof. Feed bunks were covered and protected from the elements by the roof structure.

Steers were obtained from a single herd enrolled in the MFA Health Track Beef Alliance (MFA Inc., Columbia, MO) and had been previously vaccinated and preconditioned for 45 d before arrival to the University of Missouri Beef Research Farm. No growth-promoting implants were used in either study.

Upon arrival to the University of Missouri Beef Research Farm, all animals were weighed and individually identified by inserting an electronic identification transponder button (Allflex US Inc., Dallas-Ft. Worth Airport, TX) into their right ear for the measurement of individual feed intake and feeding behavior with the GrowSafe feed intake system (GrowSafe Systems Ltd., Airdrie, Alberta, Canada).

In Exp. 1, steers were placed on a receiving diet for 14 d to allow for acclimation to the feeding system. Water and diet during this period were provided for ad libitum consumption. Steers were weighed after the receiving period and every 28 d for the next 123 d until the conclusion of the feeding behavior experiment. The experimental diet (Table 1) was formulated to meet the requirements of the animals as outlined by the NRC (2000). All ingredients were mixed and pelleted, except the whole corn, soybean hull pellets, and chopped grass hay. The resulting pellet was designated as the supplement. The pelleted supplement and the remaining feed-stuffs were mixed as a total mixed ration (TMR) using a truck-mounted paddle mixer. Steers were fed once daily at approximately 0800, and the amount provided was such that animals had TMR available to them at all times.

The experimental diet (Table 1) contained 75% whole corn and 25% TrendSetter Developer ration (MFA Inc.) until the average BW of the group reached 454 kg, at which time the experimental diet was reformulated to contain 87% whole corn and 13% TrendSetter Developer ration (Table 1). TrendSetter is a commercially available pelleted supplement that provides protein, energy, vitamins, and minerals. The TrendSetter supplement contained a feed intake limiter, which helped facilitate the removal of roughage from the diet. All feedstuffs were mixed as a TMR. Steers were fed once daily at approximately 0800, and the amount provided was such that animals had the TMR available to them at all times.

Efficiency Status

Individual animal feed intakes and feeding behaviors were collected using the GrowSafe individual animal feed intake system (model 4000E, GrowSafe Systems Ltd.). Data from Exp. 1 and 2 were analyzed using feed intake analysis software calculate intake III (version 971, GrowSafe Systems Ltd.). Each pen contained 10 animals and featured 2 feeding bunks that allowed single animal access to a feed tub. This design allowed for individual feed intake and individual animal feeding behavior data to be obtained and for each animal to serve as the experimental unit.

Individual feed intakes, initial and final BW, and ADG were used to calculate RFI. To calculate RFI, ADG and metabolic midweight (MMWT) were used to model daily feed intake using the GLM procedure (SAS Inst. Inc., Cary, NC). The model fitted was

where Y_i = expected daily feed intake of animal i; β₀ = the regression intercept; β₁ = partial regression coefficient of feed intake on ADG; and β₂ = partial regression coefficient of feed intake on MMWT. To calculate RFI, expected feed intake was subtracted from the recorded actual feed intake.

In Exp. 1, RFI values were calculated for 3 consecutive months, and 12 steers were identified as being the most efficient (n = 6) and the most inefficient (n = 6). The 6 steers with the most negative RFI values were designated as efficient, whereas the 6 steers with the most positive RFI values were designated as inefficient. In Exp. 2, RFI values were calculated for 4 consecutive months, and 17 steers were identified as being the most efficient (n = 9) and the least efficient (n = 8). Unequal efficiency group numbers were chosen in Exp. 2, due to the natural division of RFI values.

After completion of the feeding trial, the selected steers in Exp. 1 and 2 were transported to the University of Missouri Abattoir, where they were slaughtered. Due to other experimental measurements involving the steers, slaughter of the selected steers did not occur directly after completion of the trial. Hot carcass weights were measured for each steer, and the carcasses were chilled for a 24-h period at 5°C, at which time the rib eye area of each carcass was measured to the nearest 0.01 cm². Subcutaneous fat thickness at the 12th rib was determined using a USDA preliminary yield grade ruler (USDA, 1997) at an anatomical location perpendicular to the vertebral column and ³/3 of the distance caudal to the LM. To determine preliminary yield grades, the fat measurements were then adjusted by correcting for any atypical fat distribution.

Feeding Behavior

After selection of efficient and inefficient animals, feeding behavior data was analyzed for the chosen animals to determine number of eating bouts daily, time of day in which eating bouts occurred, eating rate, and feeding trial intake patterns. Number of eating bouts daily was calculated by adding the number of times that an animal entered the feed bunk with feed consumption occurring. The time of day in which eating bouts occurred was divided into 8 three-hour periods, beginning at 0000. Two eating rates (grams eaten/min) were calculated for each steer. The daily eating rate was calculated by dividing the amount of feed consumed throughout the day by the total time during the day that it took to eat the recorded intake. The period eating rates were calculated by dividing the amount of feed consumed in each 3-h period by the time it took to consume the recorded intake for that period.

Spectral analysis techniques were used to detect the existence of periodicity in a time series or to determine if cyclical feed intake patterns existed in the feeding trial daily intakes of efficient and inefficient animals. Using the finite Fourier transform, feeding trial daily intakes were decomposed into a sum of sine and cosine waves of different amplitudes and wavelengths:

where x_t = intake on d t (t = 1, 2, ..., 123); m = (n – 1)/2, and n = the number of points in the time series a₀ = 2x; a_k = the cosine coefficients; b_k = the sine coefficients; _k = 2k/n, and k = the number of data points divided by 2. From the output, 10 feeding pattern lengths or feeding periods (in days) with the best fit or greatest P-values (P = 2/(1.25 x day) were chosen and further analyzed.

Statistical Analysis

Data from Exp. 1 and 2 were statistically analyzed separately. Initial and final BW, ADG, RFI, DMI, G:F, HCW, rib eye area, fat thickness over the 12th rib, USDA yield grade, intake per day, daily eating rate, and daily feed intake variation measurements for Exp. 1 and 2 were analyzed using the GLM procedure of SAS. Individual animals served as the experimental unit. Residual feed intake category was the treatment, and treatment means were determined using the least squares means statement of SAS.

The period eating rates and the amount consumed per period for both Exp. 1 and 2 were analyzed using ANOVA as a split plot in time, as outlined by Gill and Hafs (1971) and discussed by Littell et al. (1998). All data were analyzed using the MIXED procedure of SAS. Mean differences were determined by Fisher’s LSD using the least squares means statement.

Spectral analysis using periodicity was used to determine feeding behavior daily intake patterns of differing efficiency groups. The SPECTRA procedure of SAS was utilized.

	RESULTS AND DISCUSSION

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION LITERATURE CITED

 
RFI Results

In Exp. 1, when a traditional feedlot diet was fed, grouping of animals based on RFI had stabilized after 56 d of feed intake and growth data collection, whereas 42 d of feed intake and growth data were needed in Exp. 2. Calculation of RFI from data collected after 56 d in Exp. 1 and after 42 d in Exp. 2 resulted in the same grouping of efficient and inefficient animals. The reduction from 56 to 42 d agrees with findings of Archer et al. (1999), Graham et al. (1999), and Tatham et al. (2000) that demonstrated that frequent measurement of growth could reduce the time needed for accurate RFI calculations. The measurement of growth in Exp. 2 was obtained every 21 d compared with every 28 d during Exp. 1.

Growth Study

The performance of high- and low-RFI steers is shown in Table 2. There were no differences (P > 0.13) in initial or final BW or ADG between efficient and inefficient groups in either Exp. 1 or 2. However, G:F was increased (P < 0.001) for efficient steers, and daily DMI was greater (P < 0.001) for the inefficient steers in both Exp. 1 and 2. Basarab et al. (2003) and Kolath et al. (2006) have reported similar data in which DMI was greater (P < 0.001) for the inefficient animals and G:F was increased (P < 0.001) in efficient steers, but ADG and BW of efficient and inefficient steers were not different (P > 0.80).

Carcass composition as assessed by the rib eye area, fat thickness over the 12th rib, HCW, and USDA yield grade did not differ (P > 0.10) between the efficient and inefficient groups in either Exp. 1 or 2. These data agree with previous reports from our laboratory (Kolath et al., 2006), in which carcass composition was not altered by RFI status. Basarab et al. (2003) reported that inefficient animals tended to have a slightly faster gain in empty body fat. Richardson et al. (2001) reported a 2.2% increase in protein gain by efficient steers as compared with inefficient steers.

The growth and carcass results from Exp. 1 and 2 indicate that there exists an opportunity in feedlot animals to improve efficiency without compromising growth or carcass quality of the animal, because there were no differences in measured growth and carcass variables. Arthur et al. (2001), Richardson et al. (2001), and Basarab et al. (2003) reported similar findings.

Behavior Study

Average daily eating bouts differed (P < 0.001) between efficiency groups in Exp. 1 and tended to be less in Exp. 2 (P = 0.065), with efficient animals eating fewer times per day (Table 3). The number of eating bouts daily agrees with the work of Schwartzkopf-Genswein et al. (1999) using diets that contained roughage. Average daily eating rate did not differ (P > 0.20) between efficient and inefficient groups in either Exp. 1 or 2 (Table 3).

There was no difference (P > 0.40) between the efficient and inefficient groups in the period eating rates during Exp. 1 (Table 5). In Exp. 2, during period 2 (P = 0.006), the period eating rate was greater for the efficient than for the inefficient group (Table 5). It was observed that animals exhibited faster eating rates during daylight hours or periods 3 through 7.

In both studies, significant variation existed in animal daily feed intake, but no animal within the efficient or inefficient groups was diagnosed or treated for acidosis or any other metabolic disorder. Individual daily feed intake in Exp. 1 and 2 was analyzed to determine if steers provided ad libitum access to feed would consume a constant amount of feed from day to day or if animals would develop unique feed consumption patterns over time. Figure 1 represents the daily intake of 1 steer. The range in number of days comprising each feed intake pattern was found to be similar between efficiency groups and between Exp. 1 and 2. The average number of days comprising a feeding pattern in both Exp. 1 and 2 for both efficiency groups was 2 to 3 d as well as multiples of 2 to 3 d.

View larger version (22K): [in this window] [in a new window]   Figure 1. Graph representing an intake pattern curve for 1 experimental steer.

Carter et al. (2002) concluded that feedlot cattle began accreting i.m. fat at a BW near those at which our cattle demonstrated changes in feed intake patterns, although a causal relationship between i.m. fat deposition and feeding behavior cannot be fully demonstrated. We did not observe constant daily feed intake from any animal in Exp. 1 when traditional diets were fed or in Exp. 2 when no-roughage diets were fed.

From the measured variables, there were no differences in growth and limited differences noted in feeding behavior between efficient and inefficient groups. The results of the trials did suggest increased variability of feed intake throughout the day for inefficient animals. More research on individual feeding behavior is warranted to obtain a clearer understanding of intake patterns in feedlot cattle and how it relates to efficiency status.

	Footnotes

 
¹ This research was supported in part by a USDA special programs grant (no. 2003-34450-14578).

² Corresponding author: kerleym{at}missouri.edu

Received for publication October 4, 2005. Accepted for publication August 21, 2007.

	LITERATURE CITED

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION LITERATURE CITED

 


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This Article Abstract Full Text (PDF) All Versions of this Article: jas.2005-569v1 86/1/180    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Golden, J. W. Articles by Kolath, W. H. Search for Related Content PubMed PubMed Citation Articles by Golden, J. W. Articles by Kolath, W. H.