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ANIMAL NUTRITION |
* Departament de Ciència Animal i dels Aliments, and
and
Departament de Biologia Cellular, Fisiologia i Immunologia, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
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Abstract |
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 Top Abstract INTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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0.05), longer meal length (P 0.043), and larger meal size (P 0.037) than the other 3 diets. Dietary treatment had no effect (P 
0.09) on the daily percentages of posture and behaviors. In general, heifers spent 9.97 ± 0.83% of the day eating, 2.11 ± 0.42% drinking, 25.13 ± 1.36% ruminating, 16.97 ± 1.42% in other activities such as social behavior and self-grooming, and the rest of the day (45.82 ± 2.55%) resting or doing no chewing activities. Eating, drinking, and social behaviors were performed while standing (P 0.01), whereas resting and ruminating occurred mainly while lying (P = 0.001). Eating took place mainly in the first 4 h after feeding (P = 0.001), whereas ruminating occurred mainly at night (P = 0.001). When chewing activities (eating and ruminating) were expressed per kilogram of DM or NDF from roughage intake, more time (P = 0.004) was spent chewing per kilogram of DMI for barley-based diets, and per kilogram of NDF from roughage intake for barley- (P = 0.01) and SFM- (P = 0.002) based diets. Tethered heifers fed the more fermentable and rapidly synchronized diet (barley-SFM) reduced intake and increased chewing time. With these high-concentrate diets, time spent chewing was inversely related to roughage intake.
Key Words: feeding behavior • growing cattle • high-concentrate diet
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INTRODUCTION |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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). Synchronizing the release of these nutrients may enhance ruminal fermentation and microbial protein synthesis (Herrera-Saldana et al., 1990).
High-concentrate diets promote extensive ruminal fermentation with high rates of VFA production (Allen, 1997). This high rate of VFA production, together with the low buffering capacity of ruminal digesta, increases the risk of ruminal acidosis in ruminants fed high-concentrate diets (Albright, 1993; Beauchemin and Rode, 1997). The buffering capacity of ruminal digesta is low because concentrates are easily swallowed, resulting in less mastication, and lower saliva secretion. However, recent studies with growing heifers fed high-concentrate diets have not reported signs of ruminal acidosis (Devant et al., 2000, 2001; Rotger et al., 2005).
Feeding behavior has received considerable attention in ruminant nutrition research (Beauchemin, 1991b; Dado and Allen, 1993; Nielsen, 1999). Daily intake can be achieved by various combinations of meal frequency, meal size, and feeding rate that may be determined in part by diet characteristics such as nutrient composition, physical properties, or palatability (Dado and Allen, 1993). Different feeding behavior strategies in growing heifers fed high-concentrate diets may determine the pattern of fermentation and may help prevent ruminal acidosis.
The objective of this work was to describe feeding behavior of tethered growing heifers fed high-concentrate diets with different sources of nonstructural carbohydrates (NSC) and proteins.
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MATERIALS AND METHODS |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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). To record feeding behavior data, individual feed bunks (0.9 x 0.8 m) made of stainless steel (Afora, S.A., Barcelona) were placed on a waterproof digital platform scale (HW-60KV-WP; A&D Co., Ltd., Tokyo, Japan), which was fixed to the floor and linked to a computer with a software application to download weight data (WinCP; A& D Co.). The scales had a weighing capacity of 60 kg with a minimum of 5 g.
Data Collection
The experiment began in December and consisted of 4 periods of 28 d each, comprising 14 d for diet adaptation and 14 d for data collection. The treatment diet was introduced progressively from d 1 to 3. From d 15 to 19, feed and refusal samples were collected and composited for each heifer to calculate intake. Individual feed weights were recorded continuously by the scales (at 1-min intervals) for 23.5 h/d, and each weight was classified as stable or unstable. A stable record meant that the animal was not touching the feed bunk and the weight value was readable and valid. Weight data had to meet 2 criteria to be considered as eating: the animal was touching the feed bunk (the scale recording was unstable) and the feed weight was reduced by more than 10 g compared with the previous stable recording. Thirty minutes were required to remove refusals and clean the feed bunks and the scales each day.
On d 15, 17, and 19, heifers were video-recorded simultaneously for 24 h, with continuous lighting. The recording system consisted of a camera (LTC 0500/50; Philips, Eindhoven, The Netherlands) with a focal length of 7.5 to 75 mm (LTC 3274/49; Philips) located on the ceiling approximately 3 m in front of the heifers. The recording system also included a time-lapse recorder (RT24A5T; Philips) and a black and white TV monitor (LTC 2017/50; Philips) and was protected with a plastic box to avoid dust and dirt (TC9346A; Philips).
From each 24-h video recording, the body posture and behavior of individual heifers were recorded instantaneously at 5-min intervals (time sampling). The behavioral categories used were mutually exclusive, as defined in Table 1. The presence of stereotypies defined by Redbo and Nordblad (1997) as simple repeated movements with no function in the context in which they are performed, was also recorded. Additional data on ruminal fermentation, intake, and apparent total tract digestibility were also collected and are reported in the companion article (Rotger et al., 2006).
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). Frequency was plotted as log-transformed percentages of all intervals cumulatively and backward for each intermeal interval length, and was expressed in minutes (Dado and Allen, 1993). Changes in the slope of the curve indicated a change in intrameal and intermeal intervals. The left side of the curve was adjusted to a polynomial order of 2, whereas the right side of the curve was adjusted to a regression line. The intercept between both lines represented the meal criterion (Figure 1; Labroue et al., 1994). The calculated meal criteria were used to calculate meal frequency (meals/d); meal length (min/meal) from the first eating recorded until, but not including, an intermeal interval that exceeded the criterion; meal size (g as fed/meal); and eating rate (g as fed/min).
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). Time spent eating and ruminating per kilogram of DM and NDF from roughage (NDFR) intake was calculated assuming that the activity persisted for the entire 5-min period before the observation. Total time spent chewing was calculated by adding eating and ruminating time for each heifer and period.
Statistical Analyses
Data were analyzed using the Proc Mixed procedure (Littell et al., 1996) of SAS, version 8.2 (SAS Inst. Inc., Cary, NC) for a Latin square design with a 2 x 2 factorial arrangement of treatments. The model contained the effects of protein source and NSC source, the interaction of protein x NSC source, and period as fixed effects. Heifer was considered a random effect. Effects were considered significant at P 0.05. When significant differences were detected, differences among means were tested using the Tukey multiple comparison test.
Chi-square analysis was used to assess the difference between the times spent standing or lying, and between the time spent lying on the right vs. the left side.
Meal size and the percentage of time spent in each posture and performing each behavioral activity were calculated for 4 periods after feeding (0 to 4 h, 4 to 8 h, 8 to 12 h, and 12 to 24 h) and the effect of period after feeding on each variable was tested with the same model described before, including period after feeding as a fixed effect. The effect of animal posture on behavioral activities was analyzed as the effect of period after feeding.
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RESULTS AND DISCUSSION |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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), in agreement with McCarthy et al. (1989) and Casper et al. (1994, 1999). Intake of NDFR was greater (P = 0.013) when SBM was the protein source because SBM-based diets had greater straw content.
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). Identifying which intervals are between or within meals can be problematic, because daily number and length of meals depend greatly on the selected size of meal criterion. Meal criterion estimates depend on the type of animal, the type of feed, the management system, and (mainly) by the way the meal criterion is estimated. A consistent definition of meal criterion is not available (Grant and Albright, 1995), and some criteria have been selected arbitrarily (Vasilatos and Wangsness, 1980; Cooper et al., 1999; Erickson et al., 2003). In this trial, meal criterion was estimated by individual survivorship curves for each heifer and period. DeVries et al. (2003) recommended using individual criterion when dietary treatment can affect measures based on the criterion, as was the case here. Meal criterion was longer (P 0.021) for the corn-SFM diet, which had fewer (P 0.05) meals per day of longer duration (P 0.043) and larger size (P 0.037; Table 2
). Vasilatos and Wangsness (1980) observed a negative correlation between meal size and number of meals; that is, increasing the meal size decreased the frequency of feeding in cows. The number of meals observed in our trial for all dietary treatments, except for the corn-SFM diet, matches the number of meals reported for steers fed high-concentrate diets (Gibb et al., 1998; Cooper et al., 1999; Erickson et al., 2003) and for dairy cows (Vasilatos and Wangsness, 1980), when a meal criterion of 20 min was considered. Daily intake does not equal the product of the mean number of meals per day and meal size, because the number of meals and intake per meal are inversely related and the product of their means differs from the means of their product (Table 2; Friggens et al., 1998; Tolkamp et al., 2000). Eating rate tended to be faster (P = 0.067) for barley-SFM than for corn-SFM (26.82 vs. 19.18 ± 81.24 g/ min; Table 2), possibly because of a greater number of intrameal intervals in the corn-SFM diet due to the longer duration of meal criterion.
Synchronization had no effect on daily percentages of posture and behavioral activities (Table 3), except for the time spent eating, which tended to be greater (P = 0.086) in desynchronized diets. In general, heifers spent 9.97 ± 0.83% of the day eating, 2.11 ± 0.42% drinking, 25.13 ± 1.36% ruminating, 16.97 ± 1.42% doing other activities, such as social behavior and self-grooming, and the rest of the day (45.82 ± 2.55%) resting or in nonchewing activities. Percentage of the day spent eating in this study agrees with data reported for feedlot cattle (Hicks et al., 1989), but was lower than data reported for dairy cattle (Albright, 1993). With high-concentrate diets, it is common to observe a greater percentage of time spent ruminating than eating, reflecting the greater ease of bolus formation and swallowing for grains than for forages (Beauchemin and Rode, 1997). Total time spent eating estimated by visual observation was lower than that recorded by scales (no. of meals/d x meal length), because the scales included the pauses inside a meal as time spent eating; by visual observation, eating was only recorded when heifers had their muzzle in the feed and were chewing or swallowing.
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, Wilson et al. (1999), and Mattiello et al. (2002) for calves of a similar age. Heifers mainly ate, drank, and performed other activities while standing, whereas resting and ruminating were mainly performed while lying (Table 4), in agreement with the findings of Albright (1993).
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). Normally, ruminants exhibit left-side laterality when lying (i.e., they prefer to lie on their left side; Albright, 1993). Ruminally cannulated cows markedly increase their right side laterality when lying but tend to ruminate while lying on the left, as this posture is proposed to optimize rumination (Grant et al., 1990).
Time of day had a significant effect on animal position and on behavioral activities. For all diets, more (P = 0.001) eating activity was detected in the first 4 h after feeding while heifers were standing (Tables 4 and 5), in response to daily addition of fresh feed, typical of animals offered feed once a day (Vasilatos and Wangsness, 1980; Campbell et al., 1992; DeVries et al., 2003). In all diets, meal size decreased (P < 0.001; data not shown) linearly as the time after feeding progressed (average meal size = 1,588 ± 425 g during the first 4 h after feeding and 265 ± 81 g at night, data not shown), in agreement with Tolkamp et al. (2000). This indicates that feed delivery time and change of ambient temperature and natural light with sunrise and sunset have a greater effect on eating behavior than artificial photoperiod (continuous lighting), unless heifers are in environmentally controlled chambers (Tanida et al., 1984). Ruminating was performed mainly at night (12 to 24 h after feeding) while heifers were lying (P = 0.001; Tables 4 and 5), in agreement with Beauchemin et al. (1990), Grant et al. (1990), and Campbell et al. (1992). Other activities and drinking were performed uniformly throughout the daytime, while heifers were standing (Tables 4 and 5).
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), which have lower NDFR intake (Table 2). Time spent ruminating per kilogram of DMI was greater for barley- (P = 0.001) and SBM- (P = 0.031) based diets with no interaction of NSC and protein source. Soybean meal-based diets had greater NDFR intake and more time ruminating per kilogram of DMI was necessary, but when time spent ruminating was expressed per kilogram of NDFR intake, it was greater (P = 0.002) for diets with lower NDFR intake (i.e., based on barley and SFM), with no interaction (Table 6). Total time spent chewing (eating + ruminating) per unit of DMI, as an indicator of saliva production, was greater (P = 0.004) for barley-based diets and time spent chewing per kilogram of NDFR intake was greater (P 0.002) for barley- and SFM-based diets, with no interaction. Beauchemin and Rode (1997) also observed that barley-based diets required more chewing per unit of forage intake, partly because of reduced fibrolytic activity associated with lower ruminal pH in barley- than in corn-based diets.
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for 450-kg steers fed high-concentrate barley-based diets in which time spent chewing averaged 5 to 10 h/d even when pH was lower than 5.8. In the present experiment, heifers chewed less efficiently (more chews per unit of intake); however, pH never decreased to acidotic levels (Rotger et al., 2006).
Chewing time is believed to increase linearly with increasing forage intake (Yang et al., 2001; Maekawa et al., 2002), but the time spent chewing per unit of forage intake decreases as forage intake increases (Deswysen et al., 1987; Beauchemin, 1991a; Yang et al., 2001) due to an increase in the efficiency of rumination. This increase in efficiency can be due either to an increased efficiency of particle comminution during mastication or to an increase of microbial digestion of forage (Beauchemin, 1991a), because high-forage diets may achieve ruminal conditions more adequate for cellulolysis.
The low efficiency of chewing (more chews per kg of NDFR intake) observed in ruminants fed high-concentrate diets may respond to lower fiber degradation in these diets, and may act as an adaptive mechanism to mechanically break forage particles and increase the amount of saliva added per unit of DMI (Grant, 1997). These observations suggest that the effectiveness of forage in promoting chewing increases when present in small amounts in the ration (De Boever et al., 1990; Beauchemin et al., 1994) to compensate for low ruminal pH and low cellulolytic activity of animals fed high-concentrate diets.
Among other activities (Table 7), heifers spent 3.01 ± 0.45% of the day self-grooming, 3.92 ± 1.13% performing social behaviors, 4.93 ± 1.20% licking or biting fixtures, and 4.85 ± 0.53% observing, with no effect of synchronization on this activity distribution. The frequency of these activities agrees with Redbo and Nordblad (1997) for tethered heifers, and the frequency of self-grooming agrees with Mattiello et al. (2002) for veal calves of a similar age. Observing is a common activity in tethered heifers, because they are very alert when they are waiting for feed, and listen and look toward any sound or movement (Redbo and Nordblad, 1997). Observing was performed mainly during the first 4 h after feeding (Table 5), whereas social behaviors took place mainly in the late evening (8 to 12 h after feeding; Table 5).
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) and low roughage intake (Redbo and Nordblad, 1997). However, in the present experiment with tethered heifers fed high-concentrate diets, no stereotypies were detected.
In summary, gross intake was greater for corn-based diets; this led to a longer meal criterion, lower feeding frequency, and a larger meal size for the corn-SFM diet. Synchronization had no effect on the percentage of time spent eating and ruminating; therefore, when expressed per kilogram of DMI, the diet with lower intake (barley-SFM) resulted in a longer time spent chewing per unit of intake. Barley-SFM was the most fermentable diet, because it was formulated for rapid synchronization, and was the diet with lower NDFR intake. However, heifers fed this diet reduced intake and increased chewing time as a mechanism to reduce acidosis (Rotger et al., 2006). With these high-concentrate diets, time spent chewing was inversely related to roughage intake; therefore, the fiber effectiveness increased when roughage intake was low.
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Footnotes |
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2 Corresponding author: Alfred.Ferret{at}uab.es
Received for publication June 17, 2005. Accepted for publication December 1, 2005.
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LITERATURE CITED |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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