RESEARCH PLAN

Experiments in the USA will be conducted at the USDA, ARS, Subtropical Agricultural Research Station (STARS) in Brooksville, Florida. Experiments in Israel will be conducted at the Karei Deshe Experimental Range situated on rocky, basalt slopes near the junction of the Jordan River and the Lake Kinneret (Sea of Galilee). At both locations, grazing behavior studies will be imposed on existing grazing trials which are looking at the effect of stocking rate and grazing deferment in a Mediterranean climate (Israel) or cattle breed and creep grazing in a subtropical climate (USA). The HR monitoring portion of this study in Israel is currently being conducted by two of the collaborators on this study (A. Brosh and M. Gutman) as part of a 1998 BARD grant (Estimation of Energy Expenditure of Free Living and Growing Domesticated Ruminants by Heart Rate Measurement).

USA Grazing Trial

The grazing trial conducted at STARS is looking at the effect of breed (Angus or Romosinuano) and creep grazing rhizoma perennial peanut (RRP, Arachis glabrata) on the preweaning performance of calves and their dams. Additionally, the effect of creep grazing on the subsequent postweaning performance of heifer calves including age at puberty and on body weight change, body condition score, calving interval, and rebreeding percentage of their dams is being determined. Due to the relatively short time interval from the awarding of the 1999 BARD grants and the initiation of the grazing trial at STARS that year, grazing behavior information will be determined for only the latter part of the grazing period (August-September). This time will serve to familiarize personnel at STARS with equipment handling and data down loading procedures. The full grazing period (June - September) will be monitored in 2000 and 2001. A brief protocol for the grazing study and how the grazing measurements are to be incorporated is outlined below.

The main treatment consists of cows and calves grazing tropical grass alone (bahiagrass, Paspalum notatum) or tropical grass with a creep area of tropical legume (RPP) that only the calves have access to. Treatments are replicated twice. Breed (Angus or Romosinuano) will be considered a subplot. Creep grazing will start in June of each year. Calves (based on individual id numbers) will be monitored every 2 hr from sunup to sundown (0600 - 2000 hr) one day a week every other week starting 2 wk after the creep gates are opened until the calves are weaned (September).

At the start of the grazing trial in 2000, five cows of each breed on each treatment rep combination (n=20 total) will be fitted with pedometers (SRC Co., Ltd.), which will be worn throughout the grazing season. Pedometer information will be recorded for every 4-hr period for four days of each week (Monday - Thursday). These cows will also be equipped with an internal (intra reticulum), remote telemetry reader (CowTemp, Innotek, Inc.) to record internal temperature every 30 min and stored information remotely downloaded at the same time as the pedometer readings (1200 hr each day). Grazing time (9-day vibracorder) of eight cows per treatment (n=16 total, four out of the five wearing pedometers of each breed per treatment and rep combination) will be determined for the first replicate for seven consecutive days, three times during the grazing season (first week of July, August, and September). The subsequent week the grazing time of cows in the second replicate will be determined. Recordings of continuous activity of 6 min or longer will be considered sign of grazing activity. During the same time period, the eight cows will also be fitted with GPS (GPS_2000L, Lotek Engineering, Inc.) and field position, air temperature, and head position will be determined every 30 min for a 5-d period during the seven days. Additionally, the cows will be fitted with external HR monitors (ECG Dataloggers, Dansoft Ltd.) for determination of HR during the same time period. Body weight and BC score of the calves and cows and herbage mass and nutritive value of both bahiagrass and RPP pastures will be determined in June and every 28 d thereafter until weaning. Additionally, blood urea nitrogen (BUN) of cows and calves will be determined at weighing. Pregnancy status of all cows will be determined in September by rectal palpation.

Global positioning system information concerning position of fences, trees, water, etc. will be also determined for each pasture. This information as well as that based on animal movements, ambient temperature, body temperature, activity level, grazing times, etc. will be utilized in GIS software, such as ArcView, for spatial analysis and to determine correlation of the different measurements. Stepwise regression analysis will be used to determine the relative importance of various parameters measured (i.e., grazing activity, steps, body temperature, air temperature) to HR during a given time period.

Grazing trial in Israel

The proposed grazing behavior studies will be imposed on lactating beef cows assigned to an existing grazing trial (Karei Deshe Grazing Trial). In this study, stocking density and grazing deferment are being evaluated (Table 1). This grazing

study utilizes eight paddocks, in two blocks each 25.5 to 33.0 ha in size and fenced so as to include equivalent proportions of the different range habitats in each paddock (Gutman and Seligman, 1979). Throughout the experimental period, four grazing treatments are replicated twice.
 

 
Each plot in the deferred-grazing treatments (9R and 18R) will be divided into two subplots (Table 2). The first subplot will be used for early grazing (E) and the second subplot will be used for late grazing (L). In each plot where grazing will be split, the same order of grazing will be carried out during all the trial years. Grazing will be started in the early grazing subplot in late December and the herd will be moved into the late grazing subplot in March in the high stocking density treatment (9 R) and at the start of May in the moderate stocking density treatment (1.8 R).

Amounts of remaining dry herbage in each paddock will be estimated at the end of the dry season in October before the first rains of the following rainy season. Estimates are based on calibrated ocular estimates along permanent transects in the experimental paddocks; the herbage mass in 300, 25 x 25 cm quadrats in each paddock is estimated
 

 
and 30 (every tenth quadrat) will be clipped for calibration. A paddock of 2.5 ha size (?ecological plot?), protected from grazing since 1960 will be used as a control.

Every 6 to 8 weeks, cows will be weighed in the morning after approximately 18 hr without feed or water. Calving dates will be recorded, and calves will be first weighed when the whole herd will be brought to a central corral for periodic weighing or veterinary care. Cows will be tested for pregnancy by rectal palpation at weaning, and non-pregnant cows will be replaced by cows that are tested pregnant from the commercial herd.

Although pedometer readings and temperature readings will be determined throughout the trial as outlined for the USA work, vibracorder, GPS measurements, and HR will be conducted in the four critical conditions of the grazing season (Table 3). At least four head of cows will be measured at one time in a manner similar to that outlined for the USA grazing trial.