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Archivos Latinoamericanos de Produccion Animal
Asociacion Latinoamericana de Produccion Animal
ISSN: 1022-1301 EISSN: 2075-8359
Vol. 16, Num. 4, 2008, pp. 201-209

Archivos Latinoamericanos de Produccion Animal, Vol. 16, No. 4, October-December, 2008, pp. 201-209

Original Article

Diurnal ingestive behavior of Nellore steers receiving increasing levels from supplement in pasture of Brachiaria brizantha*

Comportamiento diurno del consumo en novillos Nellore en pastos de Brachiaria brizantha y recibiendo niveles crecientes de suplemento

1 Assistant Teacher DEBI/UESB. Rua José A. Ribas Filho, 150 Morumbi - Itapetinga-BA. CEP 45700-000, Doctor Scholarship holder of FAPESB, Brazil
2 Titular Professor UEM/UESB, Researcher of the CNPq, Brazil
3 Graduating in Animal Science - UESB. Scholarship holder of Scientific Initiation of the CNPq/FAPESB, Brazil

Correspondence Address: R Rodrigues Silva, Assistant Teacher DEBI/UESB. Rua José A. Ribas Filho, 150 Morumbi - Itapetinga-BA. CEP 45700-000, Doctor Scholarship holder of FAPESB, Brazil,

Date of Submission: 13-Jun-2007
Date of Acceptance: 07-Jun-2008

Code Number: la08028


The objective of this experiment was to evaluate the diurnal ingetive behavior Nellores steers with increasing levels of energy and protein supplemention by raising in pasture of Brachiaria brizantha. The on-farm trial was developed at Boa Vista Farm in conjunction with Bahia State University, southwestern Bahia, Brazil, where forty 26-month-old Nellore steers with the initial weight of 371.0 ± 14.9 kg were previously accommodated to the experimental conditions for 14 days; they were randomly allotted in the following treatments: T 00 = mineral salt, T 03 = 0.3%, T 06 = 0.6%, and T 09 = 0.9% of energy and protein supplementation for 84 days. The animals were visually observed at 10-minute intervals for two periods of 12 hours from 6:00 am to 6:00 pm. Time for ruminating (P<0.06) had cubic effects; time for grazing (P<0.00001) and idling (P<0.00006) had quadratic effects while time for feeding had increasing linear effects (P<0.00001). The total of feed dry matter intake either in kg/animal/day or percentage (%) of the live body weight were not affected by increasing the levels of energy and protein (P>0.15). However, the total of dry forage intake and the fiber contents evaluated in neutral and acid detergent were linearly reduced (P<0.0002). Furthermore, the total time of chewing the number of bolus, and the ruminating time per bolus had cubic effects (P<0.0001); the chewing number per bolus was linearly reduced (P<0.000001); the number of grazing events (P<0.15) and the time of feeding was linearly increased (P<0.000001) although each grazing event had its average time linearly reduced (P<0.000001); the number of ruminating (P<0.02), idling events (P<0.000001), and time for each ruminating event (P<0.0002) had quadratic effects. Finally, the number of events at trough had cubic effects (P<0.000001) but the time of each idling event was not modified by the treatments (P>0.15). Therefore, it is necessary to pay special attention to the diet composition for raising beef-cattle and to the amount of feed in conjunction with both composition and ratio of pasture to concentrate because some diurnal behavior which have affected on the ingesting performan­ce of Nellore steers.

Keywords: Cattle, Ethology, Idle, Rumination, Grazing event


El objetivo de este experimento fue evaluar la ingesta diurna con niveles crecientes de suplementos de energía y proteína por novillos Nellore en pastoreo, en pastos Brachiaria brizantha. El ensayo en campo se desarrolló en la granja Boa Vista, en conjunto con la Universidad del Estado de Bahia, en el suroeste de Brasil, donde el 40 novillos Nellore de 26 meses de edad con un peso inicial de 371,0 ± 14,9 kg fueron acomodados a las condiciones experimentales por 14 días, asignados aleatoriamente en los siguientes tratamientos: T00 = sales minerales, T03 = 0,3%, T06 = 0,6%, y T09 = 0,9% de suplemento de la energía y de proteínas por 84 días. Los animales fueron observados visualmente a intervalos de 10 minutos durante dos períodos de 12 horas de 6:00 am – 6:00 pm. La hora de la rumia (P <0,06) tuvo un efecto cúbicos, el tiempo para el pastoreo (P <0,00001) y de ociocidad (P <0.00006) tuvo efectos de cuadráticos, mientras que el tiempo para la alimentación incrementos lineales (p <0,00001). El total de alimentos consumidos en materia seca en kg/animal/día o en porcentaje (%) de peso vivo no se vieron afectados por el aumento de los niveles de energía y proteína (P> 0,15). Sin embargo, el total de consumo de forraje seco y el contenido de fibra evaluado en detergente neutro yácido se redujo linealmente (P <0,0002). Además, el tiempo total de la masticación y el número de bolos, el tiempo rumiando por bolo tuvo efectos cúbicos (P <0,0001), el número de mascadas por bolo se redujo de forma lineal (p <0,000001); el número de eventos de pastoreo (P <0,15) y el tiempo de la alimentación en el valle se aumentó linealmente (P <0,000001), aunque cada caso tiene su tiempo de pastoreo promedio lineal redujo (P<0,000001), el número de rumiantes P (<0,02), al ralentí eventos (p <0,000001 ), y el tiempo para cada evento de rumiantes (P <0,0002) tuvieron efectos de segundo grado. Por último, el número de eventos en el valle tuvo efectos cúbicos (P <0,000001), pero el tiempo de cada evento al ralentí no fue modificado por los tratamientos (P> 0,15). Por lo tanto, es necesario prestar especial atención en la composición de la dieta para aumentar la carne de ganado y en la cantidad de alimento en relación con la composición y proporción de pastos para concentrarse debido a que algunos comportamiento diurno que tienen influencia en el rendimiento de la ingestión de Nellore novillos afectados.

Palabras clave: Ganado, Etología, Rumiación, pastoreo, descanso


The animal productivity is normally affected by the quality of the forage mass under intensive grazing management (Correa, 1993; Moreira et al., 2003) because the level of intake is affected by ingesting and digesting processes in conjunction with the daily demand of various nutrients (Berchielli et al., 2006). The optimization of beef-cattle production depends on the continuous supply of feed with components for attending nutritional requirements in conjunction with the forage mass of high quality along the year. Therefore, supplementing animals under adverse conditions has been a cost-effective alternative for raising beef-cattle in both cultivated and natural pastures because, in general, supplements have improved animal gains and consequently the beef productivity (Rocha, 1999).

However, medium- to high-grazing pressure in rotational stocking reduce the forage allowance and promote changes in plant architecture which significantly affects the intake and consequently the animal productivity as previously reported by Chacon and Stobbs (1976). The use of grassland systems for raising beef-cattle are also affected by many factors whose interactive effects have had strong influence on ingesting processes. These processes have significant influences on the animal growth and consequently they affect the enterprise profitability (Pardo et al., 2003). On the other hand, ruminants modify the ingesting performance for minimizing effects from the adverse quality of forages and even so they maintain appropriately the nutritional needs for production (Forbes, 1988). Furthermore, the effects are additives because the intake of supplement in conjunction with the total intake of forage mass improve the animal performan-ce; otherwise, the effects are substitutive because there is significant reduction of forage intake and no improvement in animal performance (Barbosa et al., 2001).

The previous understanding of the ingesting process has allowed the improvement of some practices for increasing beef productivity, the sanitary conditions of the herd, and for extending the animal longevity as well (Fischer et al., 2002). These practices are the location of automatic feeders and water systems which make easy to access them, the appropriate dimension of beef-cattle facilities, the accessibility to either shadows or shelter conditions to provide thermal comfort, and the regular supply of feed to animals even on pasture conditions (Albright, 1993). In addition, these behavior studies allow the understanding of how beef-cattle are able to overcome environmental effects which constantly are modifying the tropical pasture systems (Brâncio et al., 2003) and they also allow the understanding of the interaction animal versus pasture which significantly affect the feed intake and consequently the animal productivity (Erlinger et al., 1990). However, previous reports have indicated inconsistent results which describe the ingesting performance of supplemented ruminants raising on pasture conditions. For example, the feeding activities of beef-cattle in pasture conditions were modified by offering corn grain supplements (Adams, 1985) but the time when the supplement was offered had no influence on grazing and ruminating events (Barton et al., 1992). For such reasons, it has been necessary to understand the effects of supplements on the animal behavior and consequently on the productivity of beef-cattle which is raised in pasture conditions (Brâncio et al., 2003). Therefore, the objective of this trial was to study the ingesting performance of Nellore steers raising in Brachiaria brizantha pastures conditions with different levels of supplements for 84 days.

Material and Methods

An on-farm experiment was carried out from August to November, 2006 in the Beef Cattle Section of the Bela Vista Farm, Macaraní County (latitude 15º33′ S and longitude 40º24′ W), southwestern Bahia, Brazil, following the guiding principles of biomedical research with animals (Cioms, 1985). Feed samples were analyzed in the Laboratory of Food Analyses at Maringá State University, Maringá County, northwestern Paraná, Brazil, and in the Laboratory of Animal Nutrition of the Department of Rural and Animal Technology at Bahia State University-UESB, southwestern Bahia, Brazil. The on-farm experiment was established on the acreage of 52 hectares planted with Brachiaria brizantha cultivar Marandu and split into eight paddocks with 6.3 hectares which performed a pie shape with central water supply.

Forty 26-month-old Nellore steers with initial weight of 371 ± 14 kg were previously adapted to the experimental conditions for 14 days and randomly allotted in the following treatments for feeding supplements with different levels of energy and protein with 10 replications: T00 = mineral salt, T03 = 0.3%, T06 = 0.6%, and T09 = 0.9% body weight for 84 days. Each animal was an experimental unit. The pasture was evaluated each 28-day interval by taking 12 samples on 0.25 m 2 at ground level (Mcmeniman, 1997). The paddocks were deferred in May to permit a random rotational system over the experimental time when they were set stocked for 7-day periods of stay. Estimates of the residual dry biomass (RDB) were carried out in four paddocks by double sampling (Wilm et al., 1994). Sampling in this case was first carried by visual estimate and further a squared sampler was tossed 70 times; thereafter, the forage mass (kg ha -1 ) was calculated by the equation of Gardner (1986). The stockpiling forage was evaluated by the triple pairs method (Moraes et al., 1990) on four deferred paddocks. The dry biomass (DM) was calculated by TAD estimates versus the period of stay. The TAD rate was calculated by the equation of Campbell (1966) who indicated TAD J = (G i - F i - 1 )/n. In this equation TAD J is the dry biomass at time j (MS/ha/day), in kg, G i is the total average of dry biomass in the rest paddock at time i; F i - 1 is the initial average of dry matter on the resting paddocks at i-1, kg/DM/ha, and n= number of days of the period j.

The stocking rate was calculated by the equation SR = (UA t )/area in which UA t is the total of animals per ha with 450 kg of live body weight.

The forage offered (FO) was calculated by FO = {(RDB + TAD)/LW total}FNx01100 from which FO is DM/ 100 kg of LW/day, in kg; RDB is the residual dry biomass, DM/ha/day, in kg; TAD is daily stocking pilling rate, DM/ha/day, in kg; LW is live body weight, in kg/ha.

Animals after 12-hour fasting were weighted at the beginning, at the end of the experiment, and at 28-day intervals; the aim was to evaluate the daily average gains of live body weight and to calculate , in a daily basis, the supplement offered into plastic troughs at same time (10 am). The components of supplements and mineral salt are presented in the [Table - 1].

The production of feces, after 7 days of previous adapting to 10 g of chromium oxide offered at 9 am for regulating the marker flow, was further estimated for 5 days. Samples were taken on a daily basis at 9 am by collecting feces from the animal rectum; thereafter, they were stored at 10ºC before analysis by atomic absorption spectrophotometry which quantified the doses of chromium according to Williams et al. (1962). The feces production, g/day, were calculated by the following equation FP = CO/ COF in which CO is the quantity of chromium oxide offered, g/day, and COF is the concentration of chromium oxide detected in the feces, g/g DM.

The samples of forage and supplements were incubated for 144 hours into four rumen-fistulated animals. It was evaluated the internal indicator, non-digesting fibers in acid detergent (FDAi), and the re-sidual which was also considered as non-digested fibers. The dry matter intake (kg/day) was calculated by the following equation: DMI = {[(FPFNx01COF) - IS]/ COFF} + TDMI in which PF is the production of feces (kg/day); COF is the concentration of the indicator in the feces (kg/kg); IS is the concentration of indicator in the supplement (kg/day); COFF is the concentration of the indicator in the forage (kg/kg), and TDMI is the dry matter intake of supplement (kg/ day).

The content of dry matter (DM), crude protein (CP), ether extract (EE), and fibers in neutral detergent (FND) were evaluated according to Silva and Queiroz (2002). Total carbohydrates (CHOT) were determined by the equation 100 - (%CP + %EE + %Ash) (Sniffen et al., 01992) and non-fibers carbohydrates (NFCHO) were calculated by the difference CHOT minus FND. The chemical analyses of forages, supplements, RDB, SR, TAD, FO and the average daily gain (ADG) are presented in [Table - 2].

Grazing, ruminating, idling and feeding events were visually evaluated by one observer per treatment using binoculars at 10-minute intervals (Silva et al. 2006a) over two periods of 12 hours (Silva et al., 2005). Behavioral activities were assumed as mutually exclusive according to Pardo et al. (2003). The avera-ge number of chewing events per bolus (CNB), the time for ruminating each bolus (TRB), and the number of bolus diurnally ruminated (NBR) were counted by digital chronometer from which nine random data per animal was recorded according to Burger et al. (2000). The total time of chewing (TTC) was the sum of the periods for grazing and ruminating events.

Discrete periods of grazing, ruminating, idling, and feeding at trough were previously described by Silva et al. (2006b). The lifetime of each event was calculated by the daily time of each activity divided by the number of events.

Data were submitted to the analysis of variance and regression by using the SAEG software (UFV, 1997) according to the following model: Yijk = ? + Ti + eijk in which Yijk are the observation in Ti, ? is the constant, Ti are the treatment effects and eijk are the error terms. The coefficient of determination was calculated by the ratio SSR/SST and the F test, at 15%- probability were used to identify the occurrence of significant statistical models based on the coefficients of determination.

Results and Discussion

The averages of total time for grazing, ruminating, idling, feeding, the statistical models, and the coefficients of determination, respectively, are presented in [Table - 3]. At first, the total time for grazing had a quadratic performance. Accordingly, in the treatment T03 the voluntary intake was adjusted by the animals and, consequently, the total time of grazing was reduced due to higher levels ammonia produced by the intake of supplements with 5% of urea. The minimum time estimated by this equation was the total of 289 minutes achieved by 0.618% of energy and protein in the supplements. However, Pardo et al. (2003) reported relative values of diurnal grazing equal to 66.48, and 44% for 0, 0.75 and 1.5% live body weight in contrast to the present values which ranged from 58 to 41%. On the contrary, Fischer et al. (2002) found a linear reduction for increasing levels of supplements. On the other hand, Bomfim et al. (2000) observed 30-month-old animals for 12 hours (from 05:30 am to 05:30 pm) and did not find significant effects from supplements with 0.6, 0.9, 1.2 and 1.5% live body weight on the total grazing times of 386.25, 366.00, 346.25, and 315.00 minutes.

The total time of ruminating events had cubic effects (P<0.06). Accordingly, animals from treatments T00 and T06 had similar means. Evidently, animals in treatment T00 had just forage mass in the rumen which is a stimulant factor for ruminating events. Otherwise, additive effects explain the average from T06 (Barbosa et al., 2001). Animals on T03 and T09 were compelled to use less time in ruminating events due to less time on grazing which reduce the forage intake and consequently redu-ce the levels of NDFI. On the other hand, Silva et al. (2005) did not find significant effects from the levels of supplements on the total time dedicated to rumination (158.91 minutes) like Falcão et al. (1997) who reported for Holstein crossbred heifers in napier-grass (Pennisetum purpureum Sch.) pasture the total average of 153.29 minutes which was similar to the average estimated in the present experiment [Table - 3].

The total time on idling had quadratic effects (P<0.00006); consequently, animals from T03 and T09 dedicated more time to idle because the behavior activities are mutually exclusives. The maximum time estimated by this quadratic equation was the total of 282 minutes achieved by 0.643%. On the other hand, the effects reported by Silva et al. (2005) obeyed a li-near reduction due to more time spent at the trough, the same time of grazing, and, consequently, more idling at night. The present results [Table - 3] are simi-lar to the reports from Pardo et al. (2003) who detected less time on idling in animals used as control. Such a performance was due to less time in grazing and lower forage intake by those animals supplied with the highest level of supplements. Additionally, Fischer et al. (2002) reported 157 and 210 minutes for animals receiving 0 and 1% of supplements, respectively.

The total time spent on feeding at trough had cubic effects (P<0.000001); the highest level of urea in T03 was the cause of some interruption in the feed intake while the animals drank water and spent some time on idling before going back to the trough. According to this fact, the means from T03 were higher than means from T06 where the supplement intake was increased by two times. The dietary treatments T03 and T09 had higher estimates for total time than the other ones. Silva et al. (2005) reported linear increase in the time of idling due to the highest level of energy and protein in the supplements which maintained the animals more time feeding at trough. Otherwise, Pardo et al. (2003) did not find different times from animals feeding at trough with supplements 0.75 and 1.50% live body weight but they reported the occurrence of substitutive effects on idling times because there were no differences either for grazing or ruminating times.

The intake of dry matter (DM), fibers in neutral detergent (FND), fibers in acid detergent (FDA) either kg/day or percentage (%) live body weight, the statistical models, and the coefficients of determination, respectively, are presented in [Table - 4]. No effects (P>0.15) from the treatments were found for the intake of dry matter either total or the percentage of live body weight. The intake of dry matter of forage, the intake of neutral and acid detergent fibers either total quantity or percentage live body weight were linearly reduced (P<0.0002) which indicate clearly the occurrence of substitutive effects. In short, these means allow a large ethological understanding of these animals. For example, just animals on T03 had non-reductive effects caused by forage intake; consequently, animals from T06 and T09 had lower gains than expected [Table - 2] and such performance was caused by metabolic modifications affecting the intake and the digestive process. Additionally, high levels of non-structural carbohydrates are excellent growing media for those micro-organisms which are propionate producers (El-Memari Neto et al., 2003); consequently, the high production of total volatile fat acids and lactate may reduce the ruminal pH (Russel, 1998) and the high levels of these fat acids can promote some damage on the ruminal epithelium and the cellulolytic activities of micro-organisms are reduced (Orskov et al., 1971) as well as the total of dry matter and forage intake because the fiber digestibility is also reduced (Grant, 1994). The present results are corroborated by reports in which there is additive interactions before the maximum intake of supplementary energy and protein and reductive effects on total intake beyond this maximum which are normally caused by various interfaces among forage, supplement, and animal (El-Memari Neto et al., 2003).

The averages of total time of chewing and ruminating events, the number of diurnal chewing events per bolus, the quantity of bolus, the statistical models, and the coefficients of determination are in [Table - 5]. The effects were cubic for the total time of chewing TTC (P<0.0001), the number of bolus NBR (P<0.00001), and for the time ruminating each bolus (P<0.00001). At first, the highest performance achieved by animals supplemented with the dietary treatment T00 was due to the quantity of forage intake by those animals; consequently, they had more time for grazing and ruminating events, and consequently for digesting fibers; second, the additive effect from T06 was caused by metabolic interaction which promoted the forage intake while the ruminating activities were appropriately maintained. On the other hand, animals on T03 had difficulties to accommodated at 5% urea and performed different behavior during the experimental time; they dedicated more time feeding at trough, more time on idling activities, and less time on grazing and ruminating events. Certainly, interactive effects between ammonia and micro-organisms which were caused by chemical-static factors from the metabolism could have affected these ruminating activities and consequently the intake. These effects were the same which affected NBR and TRB.

The present results of TTC are in disagreement with the theory reported by Dulphy et al. (1980) who concluded that the high levels of concentrate in the total diet and the consequent increase of the starch level should promote reduction in TTC. Reviewing 32 experiments, Allen (1997) found the daily average of 667.80 minutes of TTC; consequently, considering the grazing behavior of bovines during the sunlight period, it would expect a diurnal TTC ranging from 65% to 85%. In contrast, Silva et al. (2005) did not find effects of supplements (from 0.25 to 1.00%) on TTC, NBR, and TRB which were reported as 640.0 minutes, 272 bolus, and 36 seconds per bolus, respectively. Recently, some studies suggested that the adaptability to intake high forage mass is required for an efficient grazing behavior (Silva et al., 2007).

The chewing number per bolus (CNB) at ruminating events had a decreasing linear effect (P<0.0001) in a similar way reported by Silva et al. (2005) who found 44, 44, 43, and 37 chewing per bolus with supplements of 0.25, 0.50, 0.75, and 1.00% live body weight. Despite the distinct class and genetic groups of animals, these similarities allow such a comparison in which the reduction of CNB found in the present experiment was due to the reduced NDFI intake.

The number of grazing (NGP), ruminating (NRP), idling (NIP) and feeding at trough (NPPM) events, the total time to perform all of them, the statistical models, and the coefficients of determination are presented in [Table - 6]. At first, NGP had increasing linear effects (P<0.15) unlike those reported by Silva et al. (2005) who fit a quadratic equation with the maximum of 9.68 events at 0.54% live body weight. Consequently, there was a further effect on GT which performed a decreasing linear performance (P<0.000001); in the same manner, this is another disagreement with Silva et al. (2005) who reported a quadratic equation with the maximum of 24.47 minutes at 0.53% live body weight. The reduction in GT was due to increases in NGP.

NRP (P<0.02) and NIP (P<0.000001) had a quadratic performance with maxima of 5.80 and 8.98 events at the doses of 0.42 and 0.52%, respectively. These performances were caused by additive effects from the supplements whose performance is further declining from these maxima due to ruminal metabolism which is normally modified under high levels of supplement. On the other hand, Silva et al. (2005) did not find significant effects for both traits.

The NPFM had cubic effects (P<0.000001) caused by the same reasons which affected the time dedicated to feed at trough: the level of urea in the dietary treatment T03 . On the contrary, Silva et al. (2005) reported an average of 3.03.

The TR had quadratic effects (P<0.00019) with the minimum estimated of 18.80 minutes at 0.49% while the IT was not affected (P>0.15); Silva et al. (2005) reported 10.47 minutes for TR and similar results for IT. The CMT had increasing linear effects (P<0.000001) as already reported by Silva et al. (2005) but the averages were again estimated below the range from 6.56 to 13.85 minutes each event.


The use of energy and protein in the supplements offered to Nellore steers raised in pasture conditions affected the ingesting performance due to quantity, composition and the ratio of roughage to concentrate. The individual behavior was modified by traits that affected the performance and the animal metabolism.


The authors thank to the Fundo de Desenvolvimento Científico e Tecnológico (FUNDECI) from the Banco do Nordeste do Brasil (BNB) for the financial support; to the Fundação de Amparo a Pesquisa do Estado da Bahia for the Doc-tor fellowship; to Mr. Misael Tavares Neto, the owner of Boa Vista Farm, Macaraní County, southwestern Bahia, Brazil, who offered the facilities and the animals; to the Southwestern Bahia State University and Maringá State University for technical and scientific counseling. [36]


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21.Mcmeniman, N.P. 1997. Methods of estimating intake of grazing animals. In: Reunião Anual da Sociedade Brasileira de Zootecnia, Simpósio Sobre Tópicos Especiais Em Zoo­tecnia, 34., 1997. Juiz de Fora. Anais. Juiz de Fora: Sociedade Brasileira de Zootecnia. p.131-168.  Back to cited text no. 21    
22.Moraes, A. 1990. Comparação de métodos de estimativa de taxas de crescimento em uma pastagem submetida a dife­rentes pressões de pastejo. In: Reunião Anual da Sociedade Brasileira de Zootecnia, 27., 1990, Campinas. Anais. Campinas. p.332.  Back to cited text no. 22    
23.Moreira, F.B., I.N. Prado, U. Cecato, F.Y. Wada, W.G. Nascimento and N.E. Souza. 2003. Suplementação com sal mineral proteinado, para bovinos de corte, em crescimento e teminação, mantidos em pastagem de gra­ma estrela roxa (Cynodon plectostachyrus Pilger), no inverno. R. Bras. Zootec. Viçosa. 32, 449-455  Back to cited text no. 23    
24.Ørskov, E.R. 1971. The nutrition of the early weaned lamb. 3. The effect of ad libitum intake of diets varying in protein concentration on performance and on body composition at different live weights. J. Agr. Sci. 77, 351-361  Back to cited text no. 24    
25.Pardo, R.M.P., V. Fischer, M. Balbinotti, C.B. Moreno, E.X. Ferreira, R.I. Vinhas and P.L. Monks. 2003. Comportamento ingestivo diurno de novilhos em pastejo a níveis crescentes de suplementação energética. R. Bras. Zootec. 32, 1408­-1418  Back to cited text no. 25    
26.Rocha, M.G. 1999. Suplementação a campo de bovinos de corte. In: LOBATO, J.F.P. (Ed.). Produção de bovinos de corte. Porto Alegre: PUCRS, p.77-96.  Back to cited text no. 26    
27.Russel, J.B. 1998. Estrategies that ruminal bacteria use to handle excess carbohydrate. J. Anim. Sci. 76, 1955-1963  Back to cited text no. 27    
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29.Silva, R.R., F.F. Silva, I.N. Prado, G.G.P. Carvalho, I.L. Franco, V.S. Almeida, C.P. Cardoso and M.H.S. Ribeiro. 2006b. Comportamento ingestivo de bovinos. Aspectos metodológicos. Arch. Zootec. 55, 293-296  Back to cited text no. 29    
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31.Silva, R.R., I.N. Prado, G.G.P. Carvalho, A.P. Oliveira, V.V.S. Almeida, D.R. Souza, H.A. Santana Junior and F.F. Silva. 2007. Efeito da presença do bezerro sobre o comportamento ingestivo de vacas leiteiras em pastejo de Brachiaria decumbens. Ver. Brás. Saú. e Prod. Anim. 8, 48-55  Back to cited text no. 31    
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34.Universidade Federal de Viçosa - UFV. SAEG - Sistema de análises estatísticas e genéticas. Versão 8.0. Viçosa, MG. 2000, 142p. (Manual do Usuário).  Back to cited text no. 34    
35.Willians, C.H., C.H. Williams, D.J. David and O. Iismaa. 1962. The determination of cromic oxide in faeces samples by atomic absorption spectrophotometry. J.Agr. Sci. 59, 381­-385  Back to cited text no. 35    
36.Wilm, H.G., D.F. Costello and G.E. Klipple. 1994. Estimating forage yield by the double sampling method. J. Am. Soc. Agr. 36, 194-203.  Back to cited text no. 36    

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