Grazing Behaviour Of Dairy Cows Research Articles

Development of Thresholds to Predict Grazing Behaviour of Dairy Cows from Motion Sensor Data and Application in a Pasture-Based Automatic Milking System

The monitoring and measurement of animal behaviour may be valuable for improving animal production and welfare. This study was designed to develop thresholds to predict the grazing, standing, walking, and lying behaviour of dairy cows from motion sensor (IceTag) output. The experiment included 29 lactating cows grazed in a pasture-based dairy production system with voluntary cow movement in northern Victoria, Australia. Sensors recorded motion data at 1 min intervals. A total of 5818 min of cow observations were used. Two approaches were developed using (1) the IceTag lying index and steps only and (2) the IceTag lying index, steps, and motion index for each behaviour. Grazing behaviour was best predicted by the second approach, which had a sensitivity of 92% and specificity of 60%. The thresholds were then used to predict cow behaviour during two periods. On average, across both time periods, cows spent 38% of the day grazing, 38% lying, 19% standing, and 5% walking. Predicted individual cow grazing time was positively correlated with both milk production and milking frequency. The thresholds developed were effective at predicting cow behaviours and can be applied to measure behaviour in pasture-based dairy production.

Validation of an ear tag–based accelerometer system for detecting grazing behavior of dairy cows

The objective of the study was to develop a grazing algorithm for an ear tag-based accelerometer system (Smartbow GmbH, Weibern, Austria) and to validate the grazing algorithm with data from a noseband sensor. The ear tag has an acceleration sensor, a radio chip, and temperature sensor for calibration and it can monitor rumination and detect estrus and localization. To validate the ear tag, a noseband sensor (RumiWatch, Itin and Hoch GmbH, Liestal, Switzerland) was used. The noseband sensor detects pressure and acceleration patterns, and, with a software program specific to the noseband, pressure and acceleration patterns are used to classify data into eating, ruminating, drinking, and other activities. The study was conducted at the University of Minnesota West Central Research and Outreach Center (Morris, MN) and at Teagasc Animal and Grassland Research and Innovation Centre (Moorepark, Fermoy, Co. Cork, Ireland). During May and June 2017, observational data from Minnesota and Ireland were used to develop the grazing algorithm. During September 2018, data were collected by the ear tag and noseband sensor from 12 crossbred cows in Minnesota for a total of 248 h and from 9 Holstein-Friesian cows in Ireland for a total of 248 h. A 2-sided t-test was used to compare the percentage of grazing and nongrazing time recorded by the ear tag and the noseband sensor. Pearson correlations and concordance correlation coefficients (CCC) were used to evaluate associations between the ear tag and noseband sensor. The percentage of total grazing time recorded by the ear tag and by the noseband sensor was 37.0% [95% confidence interval (CI): 32.1 to 42.0] and 40.5% (95% CI: 35.5 to 45.6), respectively, in Minnesota, and 35.4% (95% CI: 30.6 to 40.2) and 36.9% (95% CI: 32.1 to 41.8), respectively, in Ireland. The ear tag and noseband sensor agreed strongly for monitoring grazing in Minnesota (r = 0.96; 95% CI: 0.94 to 0.97, CCC = 0.95) and in Ireland (r = 0.92; 95% CI: 0.90 to 0.94, CCC = 0.92). The results suggest that there is potential for the ear tag to be used on pasture-based dairy farms to support management decision-making.

Evaluation and application potential of an accelerometer-based collar device for measuring grazing behavior of dairy cows

The commercially available collar device MooMonitor+ was evaluated with regards to accuracy and application potential for measuring grazing behavior. These automated measurements are crucial as cows feed intake behavior at pasture is an important parameter of animal performance, health and welfare as well as being an indicator of feed availability. Compared to laborious and time-consuming visual observation, the continuous and automated measurement of grazing behavior may support and improve the grazing management of dairy cows on pasture. Therefore, there were two experiments as well as a literature analysis conducted to evaluate the MooMonitor+ under grazing conditions. The first experiment compared the automated measurement of the sensor against visual observation. In a second experiment, the MooMonitor+ was compared to a noseband sensor (RumiWatch), which also allows continuous measurement of grazing behavior. The first experiment on n = 12 cows revealed that the automated sensor MooMonitor+ and visual observation were highly correlated as indicated by the Spearman’s rank correlation coefficient (rs) = 0.94 and concordance correlation coefficient (CCC) = 0.97 for grazing time. An rs-value of 0.97 and CCC = 0.98 was observed for rumination time. In a second experiment with n = 12 cows over 24-h periods, a high correlation between the MooMonitor+ and the RumiWatch was observed for grazing time as indicated by an rs-value of 0.91 and a CCC-value of 0.97. Similarly, a high correlation was observed for rumination time with an rs-value of 0.96 and a CCC-value of 0.99. While a higher level of agreement between the MooMonitor+ and both visual observation and RumiWatch was observed for rumination time compared to grazing time, the overall results showed a high level of accuracy of the collar device in measuring grazing and rumination times. Therefore, the collar device can be applied to monitor cow behavior at pasture on farms. With regards to the application potential of the collar device, it may not only be used on commercial farms but can also be applied to research questions when a data resolution of 15 min is sufficient. Thus, at farm level, the farmer can get an accurate and continuous measurement of grazing behavior of each individual cow and may then use those data for decision-making to optimize the animal management.

Grazing behaviour of dairy cows on biodiverse mountain pastures is more influenced by slope than cow breed

The aim of this study was to determine how cows with different genetic merit behave and perform when grazing biodiverse and heterogeneous mountain pastures with different slopes. Three groups of 12 cows in late lactation, each composed of four Holstein, four Montbéliarde and four Valdostana Red Pied cows, breeds of increasing presumed robustness and decreasing milk yield (MY) potential. Cows grazed without concentrate either on a low-diversity flat pasture or on two species-rich mountainous pastures having slopes of either 7° or 22°. Milk yield, BW and grazing behaviour were monitored two times in the first and once in the second grazing cycle. Cows of different breeds had similar behaviour on all pastures. The Montbéliarde cows performed close to their production potential; Holstein and Valdostana cows produced less milk than anticipated. No breed difference in terms of BW loss was found. The Valdostana cows exhibited the least selective behaviour with respect to plant species and plant growth stage. Still, all cows searched for the most palatable vegetation regardless of pasture diversity. On the steep pasture, cows optimised the trade-off between ingesting and saving energy to obtain feed. They remained longer at the lowest zone and selected forbs, whereas cows on the flatter pasture went to the upper zone to select grasses. The present study gave no evidence for a superior short-term adaptation to harsh grazing conditions through an optimised feeding behaviour of the Valdostana breed compared to Montbéliarde and Holstein cows.

Milk performance and grazing behaviour of dairy cows in response to pasture allowance

This study aimed to evaluate the effects of pasture allowances on forage production, milk yield and composition, and grazing behaviour of Holstein cows during autumn. Thirty-six Holstein cows calving in the autumn were allocated to blocks considering: calving date, bodyweight, and body score. Treatments consisted of three pasture allowances as follows: high (HA; 38.4 kg DM/cow.day), medium (MA; 30.3 kg DM/cow.day), and low (LA; 26.8 kg DM/cow.day) pasture allowances. Forage mass and forage height pre-grazing were similar (P > 0.05) for all grazing targets. Pasture-use efficiency was affected (P < 0.05) by the pasture allowance. The highest and lowest efficiency was obtained with treatments LA and HA, respectively. The neutral detergent fibre content of forage harvesting was affected (P < 0.05) by the pasture allowance, with average of 44.8, 47.0, and 49.4 to HA, MA, and LA, respectively. There was an effect of pasture allowances (P < 0.05) on the milk yield per hectare and milk yield per cow. The highest production was observed in LA (438 L/ha.day) and the lowest in HA (314 L/ha.day). The percentage of milk fat, milk protein, and milk fat (g/cow.day) did not differ (P > 0.05) among pasture allowances. There was effect (P < 0.05) of pasture allowance with higher grazing time (369 min) and lower rumination time (23.3 min) observed to HA. Pasture allowances affected (P < 0.05) the total number of bites/day and bites/min, but did not affect (P > 0.05) bite mass. The pasture managements with low (26.8 kg DM/cow.day) pasture allowances provided better conditions for milk yield per area, likely due to the better grazing efficiency. However, pasture allowance provide little measurable changes on grazing behaviour.

Effects of Herbage Allowance on Dry Matter Intake, Efficiency of Grazing,Milk Yield and Grazing Behaviour of Crossbred Holstein-Jersey Dairy Cows Grazing Alfalfa Pastures

The objectives of this study were to research the effects of herbage allowance (HA) on dry matter (DM) intake, milk yield, grazing efficiency and grazing behaviour of dairy cows grazing alfalfa (Medicago sativa L.) pastures, and to compare the estimates of herbage DM intake using either an external intake marker developed from a purified enriched lignin (LIPE®) or the animal performance method, the latter based on calculations of energy requirements.Twenty six spring calving crossbred Holstein-Jersey dairy cows (84 days in milk) were balanced and assigned to either the low HA (Lo-HA; 10.0 kg DM/cow/day) or the high HA treatment (Hi-HA; 14.5 kg DM/cow/day). Cows were offered alfalfa (Medicago sativa L.) pastures at grazing, Sorghum (Sorghum bicolor) silage (3.7 kg DM/cow/day) and concentrates (5.6 kg DM/cow/day). Herbage DM intake was estimated using the sward cutting method, the animal performance method and an indigestible intake marker (LIPE®). Decreasing herbage allowance (HA) decreased herbage DM intake by 1.1 kg cow/day (P 0.05). The cows on the Lo-HA treatment produced less milk (-4.1 kg cow/day (P <0.05) and grazed 26 min/day longer (P < 0.05) than cows at the Hi-HA. Herbage DM intake measured with LIPE® was positively correlated with estimates of herbage DM intake from the animal performance method (R= 0.65, P < 0.01).This study showed that cows at the Hi-HA treatment had greater herbage DM intake and milk yield, but had an efficiency of grazing 210 g/kg lower than cows at the Lo-HA in early lactation.

Dairy cows increase ingestive mastication and reduce ruminative chewing when grazing chicory and plantain

Although the nutritive value of chicory (Cichorium intybus L.) and plantain (Plantago lanceolata L.) has been thoroughly studied, little is known about the grazing behavior of cattle feeding on chicory and plantain swards. The objective of the present study was to assess and describe the grazing behavior of dairy cows as affected by dietary proportions of chicory and plantain fed as monocultures for part of the day. Ninety Holstein-Friesian cows (489±42kg of body weight; 4.1±0.3 body condition score, and 216±15d in milk) were randomly assigned to 15 groups (6 cows per group) and grazed according to 7 treatments: control (CTL, 3 groups), perennial ryegrass (Lolium perenne L.) dominant sward (24-h pasture strip); 3 chicory treatments comprising 20, 40, and 60% of the diet, strip-grazing a monoculture of chicory to a fixed postgrazing residual before strip-grazing a perennial ryegrass dominant sward (2 groups of cows per treatment); and 3 plantain treatments comprising 20, 40, and 60% of the diet, strip-grazing a monoculture of plantain to a fixed postgrazing residual before strip-grazing a perennial ryegrass dominant sward (2 groups of cows per treatment). Four focal animals per group were equipped with 3-dimensional motion sensors, which provided the number of steps taken at each minute of the day. These cows were also fitted with automatic jaw-movement recorders that identified bites, mastication during ingestion, chewing during rumination, and determined grazing, rumination and idling times and bouts. Daily grazing time and bouts were not affected by treatments but rumination time differed and was reduced by up to 90min when cows were allocated to chicory and plantain as 60% of their diet. Ruminative chewing was reduced in cows grazing chicory and plantain by up to 20% in cows allocated to the 60% treatments. Compared with perennial ryegrass, as the dietary proportion of chicory and plantain increased, cows spent more time idling and less time ruminating, and increased ingestive mastications 5 and 3 times for chicory and plantain, respectively. Cows allocated to chicory and plantain reduced bite rate and bites per grazing step linearly, and increased the number of mastications per bite of pasture dry matter intake while grazing pasture after having grazed chicory and plantain. These results indicate that cows grazing chicory and plantain masticate more during ingestion and reduce rumination time and chewing. They also suggest that chicory presents greater constraints to ingestion than does plantain. Thus, although chicory has been considered to have a greater nutritive value than plantain, its overall feeding value may be no greater than that of plantain.

Does pre‐grazing herbage mass really affect herbage intake and milk production of strip‐grazing dairy cows?

AbstractThe effect of pre‐grazing herbage mass (HM) on herbage intake and milk production of strip‐grazing dairy cows is usually studied at the same herbage allowance (HA). In the literature, the effect of HM seems to be affected by the cutting height above which HA is estimated. The aim of this 2 × 3 factorial study was to determine whether the effect of HM (low vs high HM) on herbage intake, milk production and grazing behaviour of dairy cows is affected by the HA estimation height (ground level vs 2·5 vs 5 cm). Two HMs were compared in three different ways: at same HA above ground level (SHA0), at same HA above 2·5 cm (SHA2) and at same HA above 5 cm (SHA5). During two consecutive years, twenty‐four Holstein‐Friesian dairy cows in mid‐lactation were assigned to one estimation height in an incomplete switchback design, with two 14‐d periods. There was an interaction between HM and estimation height for herbage intake and milk production. The effect of HM on herbage intake was positive, null and negative when HMs were compared at SHA0, SHA2 and SHA5, respectively. This study may have practical implications on future research for studying, directly or indirectly, the effect of pre‐grazing HM under strip‐ or rotational‐grazing management, and on modelling herbage intake at grazing.

Pasture intake, milk production and grazing behaviour of dairy cows grazing low-mass pastures at three daily allowances in winter

Grazing low-mass pastures is almost inevitable when extending the grazing season into late winter to reduce feed costs, cows' performance being potentially affected. An experiment was carried out to estimate the performance, pasture intake (PI) and behavioural adaptation of dairy cows when grazing low-mass pastures at LOW, MEDIUM and HIGH pasture allowances (PA), corresponding to 19, 32 and 46kg OM/cow per day above ground level, respectively. The study took place in the late winter of 2008 on good quality perennial ryegrass/white clover pastures with a mean pasture mass and a pre-grazing platemeter height of 2.3t OM/ha above ground level and 5.8cm, respectively. Each cow was supplemented with 4.4kg OM of maize silage and 2.0kg OM of cereal concentrate. Daily time at pasture was restricted to 9h between the am and pm milkings. Eighteen midlactation Holstein cows (twelve multiparous and six primiparous) were used in a 3×3 orthogonal Latin square design with three consecutive periods of 13days. On average, the cows produced 25.3kg of milk and total OM intake was 14.4kg/d. Pasture OM intake averaged 7.9kg/d and linearly increased from LOW to HIGH (+0.04kg/kg PA). Similarly, milk production per cow (+0.09kg/kg PA) and milk protein concentration (+0.04g/kg per kg increase in PA) linearly increased with increasing PA. Milk fat concentration, on the other hand, decreased by 0.10g/kg per kg increase in PA. The daily grazing time (430min) and the proportion of time spent grazing (79%) were not affected by PA. On average, pasture intake rate was low (19g OM/min) and linearly increased from 16.9g OM/min in LOW to 20.7g OM/min in HIGH. In the present study, the PI was limited even at high PA because of the cumulative effect of the low-mass pasture (low intake rate) and the restricted access time (short grazing time). Consequently, the effect of PA on PI was low. However, the milk production response to variations in PI was high because of the low energy balance recorded in all treatments.

Milking frequency and nutritional level affect grazing behaviour of dairy cows: A case study

The aim of this study was to evaluate the effect of milking frequency (MF) at two nutritional levels (NL) on grazing behaviour of dairy cows. Animals (n=48) were randomly assigned to one of four treatments from calving in a 2×2 factorial design for an entire lactation: once (OAD) or twice (TAD) a day milking at high (herbage allowance: 30.9kg dry matter/cow/day) or low (18.8kg DM/cow/day) NL. Grazing behaviour was recorded using IGER grazing behaviour recorders on three occasions at approximately 95, 157 and 208 days in milk. Data were analysed using the mixed procedure of SAS. OAD cows spent more time grazing than TAD cows (P<0.05), and had a higher number of grazing bouts (P<0.01). The initial grazing bout after morning milking was longer in TAD than OAD cows (P<0.001), and in low NL compared to high NL (P=0.01) cows. Twice daily milking disrupted grazing in the afternoon, indicated by shorter grazing bouts for these cows when initiated at 1300 (P<0.05) and 1400 (P<0.01). TAD cows initiated more grazing bouts at 1600 than OAD cows. Neither MF nor NL had an effect on time spent ruminating (P>0.05). As the grazing season progressed, cows increased the duration of the morning grazing bout, increased their bite rate, and decreased their mastication rate, probably as a result of decreasing grass quality. The additional time spent grazing after morning milking in the TAD and low NL cows likely reflects differences in hunger status between them and the OAD and high NL cows, respectively. The OAD cows had more time at pasture than the TAD cows and so were able to spend more time grazing than the TAD cows, and had less disturbance to their natural grazing pattern. This, combined with a lower milk production, could have resulted in them being less hungry. Although the behaviour of TAD cows was disturbed in the afternoon, cows were able to adapt to maintain daily grazing time budgets similar to OAD cows. This study provides valuable information about how dairy cows can adjust their grazing behaviour to cope with management strategies such as once a day milking.

Frequency distribution of sward height of kikuyu (Pennisetum clandestinum) grass pastures intensively grazed by dairy cows

Swards that are grazed continuously by cattle can become heterogeneous in structure, such that frequencies of height measurements have a skewed distribution. This structure has been best described by the double-normal, gamma and Weibull distributions rather than by the more common single-normal distribution. Limited analysis of the frequency distribution of sward height under dairy cattle grazing management is available. The current paper reports the frequency distribution of sward height under intensive dairy cow grazing of kikuyu (Pennisetum clandestinum) in a subtropical environment. Frequencies of sward height were collected during an experiment designed to investigate the effects of compressed sward height and grazing duration on grazing behaviour of dairy cows. There were two compressed sward heights (10 and 13 cm; Earle and McGowan 1979) and five grazing durations (1, 2, 4, 8 and 15 h). The frequency of height measurements taken were then fitted to four distributions – single-normal, log-normal, gamma and Weibull – to determine if treatments influenced the structure of the sward as grazing duration progressed. The frequency of sward height measurement was best described by the log-normal distribution. However, no one distribution described the frequency of height measurements consistently as grazing duration progressed, as determined by Akaike information criteria. The present analysis did not provide unequivocal evidence for either bimodal or unimodal distributions describing the height measurements for 10- and 13-cm compressed sward height treatments as grazing duration progressed.

Intake Regulation and Grazing Behavior of Dairy Cows Under Continuous Stocking

This experiment aimed at studying the behavioral strategies grazing dairy cows use to satisfy their nutritional needs as the day progresses and the possible role of rumen fill in controlling these behavioral strategies. The day was divided into 3 main periods (0600 to 1200h, 1200 to 1800h, and 1800 to 2400h), where the 3 main grazing bouts (dawn, afternoon, and dusk) of dairy cows usually occur. Four late lactating rumen-cannulated dairy cows were used in a repeated measures design; grazing bout was the within-subjects factor. Cows had access to a 1-ha grass sward under a continuous stocking system. To estimate dry matter intake, bite rate, bite mass (BM), and intake rate at the 3 grazing bouts, cows were rumen-evacuated at 0600, 1200, 1800, and 2330h, and the jaw recorders were fitted to the cows between these time points. Time spent eating by dairy cows at the dusk grazing bout was much longer than that at the other 2 grazing bouts and composed about 40% of the daily total eating time. Total grazing jaw movement (TGJM) rate was constant during the day at around 75/min. Bite rate, BM, and, hence, intake rate increased, but chewing rate decreased as the day progressed. The increase in BM was mainly due to the increase in dry matter content of the grass at dusk rather than increased bite dimensions. Therefore, it could be concluded that the main behavioral strategies dairy cows use to satisfy their nutritional needs under continuous stocking include manipulating their eating time, biting rate, and chewing rate, with little control over TGJM rate and BM. Dairy cows interrupted the first 2 grazing bouts (dawn and afternoon) long before reaching their maximal rumen capacity, indicating that rumen fill is less likely to play a significant role in signaling the termination of these 2 grazing bouts. However, rumen pool sizes were always maximal at the time when the dusk grazing bout ceased, indicating that rumen fill is more likely to play a major role in signaling the termination of the dusk grazing bout.

Milk Production and Composition, Rumen Fermentation Parameters, and Grazing Behavior of Dairy Cows Supplemented with Different Forms and Amounts of Corn Grain

The objectives were to compare milk production and composition, change in body weight and body condition score, rumen fermentation parameters and grazing patterns by cows when supplemented with different forms and amounts of corn grain. In experiment 1, 36 Holstein cows were supplemented with either 6, 6, 6, or 4kg/d of dry matter of high moisture corn, coarsely ground corn, finely ground corn, or high moisture corn in two equal daily feedings, respectively. Milk yield (30.3kg/d), milk protein (2.97%), and milk urea N (14.7mg/dl) were not different among treatments. Body weight change and body condition score change were similar (23.1kg and –0.24) for the 10-wk study. During experiment 2, four rumen cannulated cows in midlactation were supplemented with 6kg/d of dry matter from either coarsely ground corn or high moisture corn in two equal feedings after milking. After the p.m. milking, ruminal pH was measured and rumen fluid samples were collected from cows to determine ammonia N and volatile fatty acids at 0.5, 1, 2, 3, … 8h post-corn feeding during grazing. Ruminal pH values were similar for corn supplements, and, with one exception, were 6.0 or below between 5 and 8h. Ruminal ammonia-N concentrations reached a maximum at 7h also. In experiment 3, 40 cows were observed for grazing behavior every 30min for two consecutive days. Cows grazed an average of 6.4h/d, 4.1h in the afternoon and 2.3h in the morning. Milk yield, milk composition, change in body weight, and body condition were similar regardless of the type or amount of corn supplemented.

The effects of sodium and potassium fertilizers on the grazing behaviour of dairy cows

Sodium fertilizer has been observed to increase the grazing time of dairy cows kept on pastures of restricted availability, but it is unclear whether this is a behavioural response to changes in pasture composition or whether it is an indirect effect of a reduction in herbage availability caused by increased cow production and appetite. Sodium fertilizer was applied in an experiment utilising tall pasture and low stocking rates so that availability would not be restricted. Cows on the pasture with sodium fertilizer still had longer grazing times than those on pasture where no sodium fertilizer had been applied. They had more feeding bouts but bout length was reduced, and they had faster biting and walking rates while grazing. They ruminated for longer, with a faster chewing rate, and spent longer standing idle and less time lying idle. They had longer drinking bouts but a similar number of them, compared to the cows on pasture without sodium. The fixed and variable energy costs of grazing and drinking bouts were estimated, these being the energy requirements for activities that are independent and dependent of bout duration, respectively. It is proposed that for grazing bouts the low ratio of fixed costs (getting up and lying down) to variable costs (standing and walking) favoured an increase in bout number to increase the grazing time of cows grazing pasture fertilised with sodium. For drinking bouts, the high ratio of fixed costs (getting up, lying down, standing and walking to the trough) to variable costs (standing at the trough) favoured bout elongation to increase the drinking time of cows grazing pasture fertilised with sodium. A second experiment with unrestricted herbage availability between morning and afternoon milking compared the grazing response to sodium and potassium fertilizers with a control where no fertilizer was applied. Grazing time was increased most by sodium and a smaller response occurred with potassium. The proportion of herbage that was rejected by the cows decreased with sodium and to a lesser extent potassium. It is concluded that changes in herbage composition with sodium fertilizer increase feeding and drinking by the grazing dairy cow, with the increase in feeding being achieved by increased bout number but reduced bout length, and the increase in drinking being by increased bout length.

Sources of variation in the grazing behaviour of dairy cows

SUMMARYMeasurements of grazing, ruminating and idling time and number and duration of bouts of these activities were made on cows grazing a perennial ryegrass-white clover sward on a number of different occasions between 8 May and 10 July 1990 at the North Wyke Research Station, Devon, UK. Repeatabilities, calculated using the residual maximum likelihood method, were low for all measurements, the highest being for idling time. Coefficients of variation were generally lower between periods than between animals for total activity times and ruminating and idling bout duration but were higher for the number of bouts of all activities and for meal duration. Grazing time and meal duration increased significantly as the season progressed, while the number of bouts of all activities declined. Behaviour was not significantly correlated with meteorological conditions. There were no significant correlations between production traits and mean behaviour of cows across periods.

Variation in the grazing behaviour of dairy cows measured by a vibrarecorder and bite count monitor

Ten Friesian dairy cows were fitted on the neck with a Walker pedometer to evaluate the pedometer as a low-cost means of recording grazing bite number, and a Vibrarecorder for comparison and to evaluate the between-cow and between-day coefficients of variation (CV) of grazing bouts, in order to evolve an optimum recording strategy. The total number of daily bouts averaged 5.01 with a mean duration of 1.85 h, giving a total grazing time of 9.27 h per cow per day. The grazing time recorded by the Virarecorders was generally linearly related to total daily bites recorded by the pedometers, although in some cases a quadratic function was significant which was assumed to arise from variation in the biting rate at high grazing times. The between-cow CV of daily grazing time was greater than the between-day CV, but at certain times of the day, particularly at night, the between-day CV was very high. More variation occurred in grazing bout duration than bout number and the variation in total bite number tended to be greater than grazing time.

The effects of injected and surface-spread slurry on the intake and grazing behaviour of dairy cows

ABSTRACTDirect injection of slurry into soil was tested as a means of avoiding the rejection of herbage by dairy cattle when slurry is spread on the surface. British Friesian dairy cows grazed paddocks that had been injected with slurry at 25 t/ha ( = 60 kg N/ha) 9 weeks previously, had slurry spread on the surface at the same rate and time, or received 60 kg N/ha as ammonium nitrate. There was less herbage dry matter available per cow on paddocks with slurry than on the control. The cattle on the surface slurry treatment consumed approximately 30% less herbage dry matter than those on the other two treatments.Cattle on pasture with surface-spread slurry spent longer grazing, walked about more during grazing, appeared to take smaller bites of grass, engaged in competitive interactions more frequently and drank more often. Behaviour was less affected on injected paddocks. In a second experiment, paddocks which either received inorganic fertilizer throughout the season, or were injected at 25 t/ha in June and August instead of the fertilizer application, were grazed by the herd at intervals during the season. Injecting slurry had no effect on herbage intake or animal behaviour.

Milk production, milk composition, rate of milking and grazing behaviour of dairy cows grazing two tropical grass pastures under a leader and follower system

Milk production, milk composition, rate of milking and grazing behaviour were measured for lactating Jersey cows having both the first opportunity to graze (leaders) and also when offered the remaining herbage (followers) from 3-week regrowths of two nitrogen-fertilized tropical pastures, Rhodes grass (Choris gayana cv. Pioneer) and Gatton panic (Panicum maximum cv. Gatton). Twenty-four cows were used in a latin-square design with experimental periods of 14 days. Both leaders and followers were allocated 40 kg DM cow-1 day-1. Leader cows produced 8.0 kg milk cow-1 day-1 compared with 5.8 kg milk cow-1 day-1 for followers, a difference of 38 per cent. Both leader and follower cows grazing Gatton panic produced more milk than cows grazing Rhodes grass. Milk from leader cows contained a higher percentage of solids-not-fat and protein and a lower butterfat percentage indicating a higher intake of digestible nutrients. Cows showed a preference for leaf, and after easily accessible leaf was removed by leader cows the follower cows had a small bite size. Follower cows partially compensated by increasing grazing time, mainly at night. Follower cows had a longer let-down time and a longer milking time per kilogram of milk produced. Milk production was linearly related to bite size and availability and accessibility of leaf were considered to be the main factors influencing production.

THE AUTOMATIC RECORDING OF THE GRAZING BEHAVIOUR OF DAIRY COWS

ABSTRACTA technique for the automatic recording of the grazing behaviour of dairy cows was investigated, using ‘Vibracorders’ which transmit grazing movement via a pendulum and stylus to a 24 h recording chart. The total labour input was 2 h/day for 6 cows, which gave 144 h of results. In 2 months, 3312 h of recording were obtained. Total grazing time per cow in 24 h was 559 min. on a rigid rotational system of grazing and 638 min. on a system of set stocking. Grazing time was significantly and negatively related to the yield of available herbage DM. It is concluded that if the Vibracorders are sealed and fitted correctly, they are simple, reliable and accurate instruments for automatically measuring the grazing behaviour of dairy cows.

Studies on the renovation of wild Sasa-land : 1. Effects on the seed-bed preparation and fertilization in the Sasa-land during five years, in relation to the palatability and grazing behaviour of dairy cows

Studies on the renovation of wild Sasa-land : 1. Effects on the seed-bed preparation and fertilization in the Sasa-land during five years, in relation to the palatability and grazing behaviour of dairy cows