Applied Animal Behaviour Science 98 (2006) 315–322 www.elsevier.com/locate/applanim
Short communication
A note on eating behaviour of dairy cows at different stocking systems—diurnal rhythm and effects of ambient temperature H.Z. Taweel a,b,*, B.M. Tas a, H.J. Smit b, S. Tamminga a, A. Elgersma b,c a Animal Nutrition Group, Department of Animal Sciences, Wageningen Institute for Animal Sciences (WIAS), Wageningen University, P.O. Box 338, 6700 AH Wageningen, The Netherlands b Crop and Weed Ecology Group, Department of Plant Sciences, Wageningen University, P.O. Box 430, 6700 AK Wageningen, The Netherlands c Department of Plant Production, Faculty of Bioscience Engineering, Ghent University, Belgium
Accepted 4 October 2005 Available online 23 November 2005
Abstract This experiment was aimed at studying the diurnal rhythm of dairy cows eating behaviour at different stocking systems, and quantifying the effect of daily ambient temperature on this diurnal rhythm. In two experiments carried out in the summer of 2003 in The Netherlands, eight dairy cows were offered fresh pasture of perennial ryegrass. In the first experiment, four cows were given access to 1 ha pasture under a continuous stocking system (CSS), whereas, in the second experiment, four cows were given access to 528 m2 of a pasture daily, under a 1-day strip grazing system (SGS). In both experiments, grazing behaviour was measured repeatedly using jaw recorders. Under CSS, dairy cows had the longest meal at the evening, whereas under SGS, they had the longest meal in the afternoon. Under both systems, bite rate was maximal and chewing rate minimal during the evening bout. Dairy cows reduced their daylight eating time when maximum daily ambient temperature exceeded 25 8C. Bite rate and chewing rate were not influenced by management or ambient temperature. It appears to be possible to influence the timing and length (duration) of grazing bouts by management, mainly by changing the timing of allocating the new plot. However, it seems to be
* Corresponding author. Tel.: +31 317 483512; fax: +31 317 485572. E-mail address:
[email protected] (H.Z. Taweel). 0168-1591/$ – see front matter # 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.applanim.2005.10.010
316
H.Z. Taweel et al. / Applied Animal Behaviour Science 98 (2006) 315–322
harder to influence the daily rhythm in bite rate and chewing rate, as both appeared not be influenced by ambient temperature or management. # 2005 Elsevier B.V. All rights reserved. Keywords: Eating behaviour; Ambient temperature; Stocking system; Dairy cows
1. Introduction To satisfy its nutritional needs under the circumstances imposed by the sward, management and the environment, the grazing dairy cow maneuvers by adjusting its eating behaviour in terms of eating time, bite rate, chewing rate and intake rate. Therefore, not only the duration of eating at the three main grazing bouts during the day will be different, but also bite rate, chewing rate, and intake rate may differ as well (Taweel et al., 2004). Daily herbage intake is the sum of the amount eaten at the different grazing bouts, which in turn is determined by the duration of the bout and the intake rate during that bout. Factors of plant, animal and environmental origin have been shown to influence eating behaviour of dairy cows (Pulido and Leaver, 1995). Recently, a large amount of research was directed towards understanding and quantifying the effect of both plant and animal factors on eating behaviour of dairy cattle (Penning et al., 1991; Gibb et al., 1997, 1999). This experiment aims to study the diurnal rhythm of dairy cows eating behaviour at different stocking systems, and quantify the effect of daily ambient temperature on this diurnal rhythm.
2. Materials and methods 2.1. Experiments In two experiments carried out in the summer of 2003 in Wageningen, The Netherlands, eight Holstein-Friesian dairy cows were offered fresh pasture of perennial ryegrass (Lolium perenne L.). In the first experiment, four cows (600 20 kg BW) were given access to 1 ha pasture under a continuous stocking system (CSS), where grass availability was not limited at any time of the day during the experiment. The pasture had a standing crop of approximately 1700 kg DM/ha before the cows were turned in. The cows were in late lactation (310 21 days in milk), and produced 18.0 0.4 and 19.1 1.5 kg of milk at the start and the end of the experiment, respectively. The experiment lasted 3 weeks (from 15 June to 4 July). Grazing behaviour of each cow was measured twice a week during the last 2 weeks of the experiment using IGER jaw recorders (Rutter et al., 1997). In the second experiment, four dairy cows (580 5 kg BW) were given access to 528 m2 of a pasture daily, under a 1-day strip grazing system (SGS), in which the new plot was allocated at 12:00 h. The pasture had a standing crop of approximately 2000 kg DM/ ha, therefore the herbage allowance was above 25 kg DM/cow/day. The cows were in early lactation (83 4 days in milk) and produced 30.7 1.8 and 27.6 0.5 kg of milk at the start and end of the experiment, respectively. The experiment lasted 8 weeks (15 July to 15
H.Z. Taweel et al. / Applied Animal Behaviour Science 98 (2006) 315–322
317
September) and grazing behaviour of each cow was measured twice every other week. The cows were adapted to grazing and pasture 2 weeks before the onset of the experiment. In both experiments, water was continuously available on the field and the cows were milked twice daily at 6:00 and 16:00 h, using a mobile milking parlour that was placed at the side of the pasture. Weather data in terms of minimum, maximum and average daily (24 h) ambient temperature, precipitation, humidity, hours of sunlight, timing of sunrise and sunset, and wind speed were recorded at the Haarweg weather station, Department of Meteorology, Wageningen University, The Netherlands (see Table 1). In both experiments, during the days when grazing behaviour measurements were performed, herbage samples were collected (hand plucking) three times a day at 7:30, 14:00 and 20:00 h, to determine the quality of the grass at each bout under both systems. These herbage samples (approximately 500 g fresh herbage) were weighed immediately and stored in a freezer ( 20 8C). Later, these samples were dried, ground to pass a 1 mm sieve and analysed for dry matter (DM), organic matter (OM), crude protein (CP (N 6.25)), water-soluble carbohydrates (WSC) and neutral detergent fibre (NDF) as described by Taweel et al. (2005). 2.2. Jaw recording and analysis In the CSS experiment, jaw recorders were fitted to the cows starting at 6:30 h, just after the morning milking, and ending at 6:00 h just before the morning milking the next day. In the SGS experiment, jaw recorders were fitted to the cows at 12:00 h, immediately before moving to the new plot, and remained there until 12:00 h the next day. The recordings were analysed using the GRAZE software (Rutter, 2000). In both experiments, the day was divided into three main periods (6:00–12:00, 12:00–18:00, and 18:00–24:00 h), where the three main grazing bouts of dairy cows (morning, afternoon and evening) usually occur. The jaw recordings for each cow in each experiment were analysed for each bout. 2.3. Statistical analysis The two experiments were analysed separately. The effect of maximum daily ambient temperature on eating behaviour was investigated by regressing eating behaviour parameters (dependent variables) on temperature (independent variables) using the curve fitting procedure of SPSS and selecting the best fitting model. To study the diurnal rhythm of eating behaviour the data of each experiment was analysed as a repeated measures design, in which the grazing bout was the within subjects factor, with three levels (morning, afternoon and evening) using the repeated measures procedure of SPSS (SPSS for Windows, Rel. 12.0.1. 2003. Chicago: SPSS Inc.).
3. Results 3.1. Continuous stocking system (CSS) (experiment 1) The concentration of both DM and WSC in the herbage was highest (P < 0.01) and that of NDF was lowest in the evening (Table 2). Ambient temperature only influenced daylight
318
Date (dd/mm)
Minimum temperature (8C)
Maximum temperature (8C)
Average temperature (8C)
Sunlight (min)
Humidity (%)
Rain fall (mm)
Wind speed (m/s)
Sunrise time
Sunset time
Continuous stocking (experiment 1) 25/06 6.6 27/06 13.5 01/07 13.9 03/07 12.5
22.5 26.8 20.5 19.6
15.9 21.0 16.3 15.8
691 866 369 106
63 53 86 86
0.0 0.0 0.5 10.9
2.2 3.0 4.5 5.4
05:19 05:20 05:22 05:24
22:05 22:05 22:04 22:04
Strip grazing (experiment 2) 22/07 13.1 24/07 14.3 05/08 12.3 07/08 17.0 19/08 10.0 21/08 7.9 09/09 7.9 11/09 8.2
24.2 24.7 31.0 34.5 23.7 24.1 19.7 19.2
19.4 18.6 23.0 26.8 17.9 16.2 13.4 14.1
574 266 804 795 277 483 279 390
68 79 49 52 67 65 81 80
3.8 14.4 0.0 0.0 0.0 0.0 0.9 0.0
3.0 2.3 2.3 2.5 3.5 3.1 1.8 3.2
05:45 05:48 06:06 06:10 06:29 06:33 07:04 07:07
21:47 21:44 21:25 21:21 20:57 20:53 20:10 20:05
H.Z. Taweel et al. / Applied Animal Behaviour Science 98 (2006) 315–322
Table 1 Weather conditions and sunrise and sunset times during measurement days
H.Z. Taweel et al. / Applied Animal Behaviour Science 98 (2006) 315–322
319
Table 2 Average herbage chemical composition (g/kg DM) under two stocking systems (continuous stocking and strip grazing) Variable a
Time of day (h) 07:00
Continuous stocking DM (g/kg) 177 a WSC 135 a CP 170 NDF 446 b Strip grazing (new DM (g/kg) WSC CP NDF
S.E.M.
14:00
20:00
225 ab 168 b 153 449 b
251 b 190 c 155 428 a
plot at 12:00 h) 185 a 247 89 a 112 195 a 213 521 b 456
b b b a
274 123 198 467
b b a a
Significance of effect of Time
Linear
Quadratic
9.6 7.3 2.7 3.1
0.001 0.009 0.050 0.001
0.003 0.01 0.051 0.002
0.33 0.09 0.047 0.001
11.5 4.0 3.3 4.0
0.003 0.001 0.001 0.001
0.01 0.001 0.34 0.001
0.31 0.37 0.001 0.001
a DM is dry matter in g/kg fresh; WSC is water-soluble carbohydrates; CP is crude protein; NDF is neutral detergent fibre.
eating time (6:00–24:00 h, night grazing not included) (Fig. 1), and eating time during the afternoon bout (Fig. 2). Bite rate and chewing rate were not influenced by daily average or maximum ambient temperature. Under CSS, dairy cows grazed a longer (P < 0.05) time during the evening bout. Bite rate increased (P < 0.05) as the day progressed from 54 to 61 bites/min and the chewing rate decreased (P < 0.05) from 20 to 14 chews/min (Table 3). 3.2. Strip grazing system (SGS) (experiment 2) The concentration of DM and WSC in the herbage was highest (P < 0.01) in the evening time, whereas that of NDF was highest (P < 0.05) in the morning (Table 2). Ambient temperature influenced daylight eating time (6:00–24:00 h, night grazing not included) (Fig. 1), and eating time during the afternoon bout (Fig. 2). Bite rate and
Table 3 Eating behaviour of dairy cows managed by two systems (continuous stocking and strip grazing) Behavioura
Grazing bout (h) Morning 6–12
S.E.M.
Afternoon 12–18
Evening 18–24
151 a 56 a 15 a
182 b 61 b 14 a
Strip grazing (new plot at 12:00 h) TET (min) 103 a 221 c Bite rate 52 a 54 a Chewing rate 14 a 16 b
164 b 60 b 13 a
Continuous stocking TET (min) 146 a Bite rate 54 a Chewing rate 20 b
a
Significance of effect of Bout
Linear
Quadratic
5.0 0.7 0.4
0.003 0.01 0.001
0.006 0.004 0.002
0.11 0.82 0.006
6.3 1.1 0.4
0.001 0.05 0.02
0.001 0.004 0.40
0.001 0.52 0.011
TET is total eating time. Both bite rate and chewing rate are expressed per minute.
320
H.Z. Taweel et al. / Applied Animal Behaviour Science 98 (2006) 315–322
Fig. 1. The effect of daily maximum temperature on daylight eating time (06:00–24:00 h) under strip grazing (black circles) and continuous stocking (crosses). The best fitting model for strip grazing is indicated by the black continuous line Y = 397 + 75X 1.56X2; R2 = 0.60, P < 0.001, and the best fitting model for continuous stocking is indicated by the broken line Y = 157.9 + 45.2X 1.36X2; R2 = 0.77, P < 0.001.
Fig. 2. The effect of maximum daily ambient temperature on the afternoon eating time (12:00–18:00 h) under strip grazing (black circles) and continuous stocking (crosses). The best fitting model for strip grazing is indicated by the black continuous line Y = 283 + 46X 0.99X2; R2 = 0.76, P < 0.001, and the best fitting model for continuous stocking is indicated by the broken line Y = 411 14X + 0.1X2; R2 = 0.65; P = 0.001.
H.Z. Taweel et al. / Applied Animal Behaviour Science 98 (2006) 315–322
321
chewing rate were not influenced by temperature. Under SGS, the cows grazed a longer (P < 0.05) time during the afternoon bout compared to the other bouts of the day. Bite rate increased (P < 0.05) as the day progressed, from 52 to 60 bites/min, and chewing rate was lowest (P < 0.05) in the evening (Table 3).
4. Discussion Under both stocking systems (CSS and SGS), the concentration of DM and WSC in the herbage increased at the evening with approximately 30%. The increase in DM and WSC in the evening is believed to be related to plant physiological processes such as transpiration and photosynthesis, and to weather conditions. Under SGS, the NDF content of the grass was highest in the morning mainly due to the fact the new pasture was allocated at 12:00 h, therefore, samples taken at 7:30 h next morning represent grass from a depleted pasture. Under CSS, dairy cows had the longest meal at the evening, whereas under SGS, they had the longest meal in the afternoon. The reason why cows under SGS in the present study grazed longer in the afternoon could be related to the fact that the new plot was allocated at 12:00 h mid day. This made fresh and tall pasture available during the afternoon, and probably encouraged the cows to prolong their eating time in the afternoon. Under both stocking systems, bite rate was maximal and chewing rate minimal during the evening grazing bout. This indicates that dairy cows were trying to maximize their intake at evening time before darkness falls, by changing their jaw movements into more bites and fewer chews, regardless of the stocking system they were exposed to. This maybe related to the higher concentration of DM and WSC in the leaves in the evening. It may also be related to the lower temperature at dusk time, therefore the effect of the change in chemical composition of the grass and the effect of the change in temperature as evening approaches are confounded in this study. Under both systems dairy cows reduced their daylight (6:00–24:00 h) eating at high daily ambient temperature, from around 510 to 400 min. The reduction in daylight eating time was mainly due to a reduction in the afternoon eating time at high daily ambient temperature. When maximum daily temperature exceeds 25 8C, the animals start responding by decreasing their daylight eating time (Figs. 1 and 2). Before this threshold (25 8C) daylight eating time appears not to be reduced significantly. The range in maximum daily temperature in this study fluctuated between 19 and 38 8C (Table 1), therefore, caution should be taken when extrapolating the results to a range that is outside the temperature range of this study.
5. Conclusions Dairy cows reduce their daylight eating time when maximum daily ambient temperature exceeds 25 8C by mainly reducing their afternoon eating time. From the results it appears that one can influence the timing and length (duration) of grazing bouts by management, mainly by change the timing of allocating the new plot. However, it seems to be harder to influence the daily rhythm in bite rate and chewing rate, as both were not influenced by ambient temperature or management.
322
H.Z. Taweel et al. / Applied Animal Behaviour Science 98 (2006) 315–322
References Gibb, M.J., Huckle, C.A., Nuthall, R., Rook, A.J., 1997. Effect of sward surface height on intake and grazing behaviour by lactating Holstein-Friesian cows. Grass Forage Sci. 52, 309–321. Gibb, M.J., Huckle, C.A., Nuthall, R., Rook, A.J., 1999. The effect of physiological state (lactating or dry) and sward surface height on grazing behaviour and intake by dairy cows. Appl. Anim. Behav. Sci. 63, 269–287. Penning, P.D., Parsons, A.J., Orr, R.J., Treacher, T.T., 1991. Intake and behaviour responses by sheep to changes in sward characteristics under continuous grazing. Grass Forage Sci. 46, 15–28. Pulido, R., Leaver, J.D., 1995. Influence of initial milk yield, sward height and concentrate level on herbage intake and grazing behaviour of dairy cattle. Annales de Zootechnie 44 (Suppl.), 129. Rutter, S.M., Champion, R.A., Penning, P.D., 1997. An automatic system to record foraging behaviour in freeranging ruminants. Appl. Anim. Behav. Sci. 54, 185–195. Rutter, S.M., 2000. Graze: a program to analyse recordings of the jaw movements of ruminants. Behav. Res. Methods Instrum. Comput. 32, 86–92. Taweel, H.Z., Tas, B.M., Dijkstra, J., Tamminga, S., 2004. Intake regulation and grazing behaviour of dairy cows under continuous stocking. J. Dairy Sci. 87, 3417–3427. Taweel, H.Z., Tas, B.M., Smit, H.J., Elgersma, A., Dijkstra, J., Tamminga, S., 2005. The effect of feeding perennial ryegrass with an elevated concentration of water-soluble carbohydrates on intake, rumen function and performance of dairy cows. Anim. Feed Sci. Technol. 121, 243–256.