Grazing behaviour and weight change of cattle turned out to pasture in spring

Abstract

. Grazing behaviour and weight change of cattle turned out to pasture in spring. Can. J. Anim. Sci. 83: 801-808. In the first of two trials, 20 Hereford steers were allocated to two adjacent 1.6-ha pastures on 29 May 1996. Steers in one pasture were given no supplement, while those in the other received supplemental silage each day. All steers on each treatment grazed their allocated paddock continuously for 28 d. Steers on pasture were weighed and their behaviour was monitored periodically throughout the 4 wk of grazing. The dry matter (DM) availability at turnout (651 kg hd -1 ) was considered in excess to requirement, since neither availability nor sward height declined over 28 d. In spite of this, steers lost 15 kg after turnout and took 12 d to regain their initial weight. There were no treatment effects. Nutrient composition of the sward changed in accordance with advancing maturity. Percent of time observed grazing (51%) did not change over the 28-d period; however, rumination time increased from around 10 to 30%. Grazing behaviour was similar for steers on both treatments. Silage intake averaged only 1.3 kg DM hd -1 d -1 . In 1997, 28 yearling steers were used in a 2 × 2 factorial design to study the effect of turnout date to pasture [21 May (E) vs. 4 June (L)] and supplemental silage feeding on weight change, grazing behaviour, pasture productivity and forage quality over 28 d. The DM availability at turnout was 391 kg hd -1 . Available DM and sward height declined in both early and late treatments after turnout. The early group had to be removed from the trial after 16 d when sward height dropped below 4 cm. Sward quality after turnout declined only for the late group. Loss of body weight (BW) and days to regain initial BW after turnout were greater for early versus late steers. Steers ate only 0.5 kg silage DM hd -1 d -1 , but this reduced weight loss in late steers. Cattle turned out later spent less time grazing (P < 0.001 at 5 and 14 d) but no less time ruminating. Transient weight loss associated with turnout to pasture cannot be wholly explained by behavioural patterns. Other factors, such as altered ruminal conditions, must also play an important role. Can. J. Anim. Sci. 83: 801-808. Dans le premier de deux essais, le 29 mai 1996, on a placé 20 bouvillons Hereford dans deux pâturages adjacents de 1,6 ha. Seul les animaux du second pâturage ont reçu quotidiennement un supplément d'ensilage. Dans les deux cas, on a laissé les animaux brouter à satiété l'herbe de leur enclos pendant 28 jours. On a pesé et surveillé le comportement des animaux périodiquement durant les quatre semaines de paissance. La quantité de matière sèche disponible à la mise à l'herbe (651 kg par tête) dépassait les besoins des animaux, puisqu'au terme des 28 jours, ni les stocks ni la hauteur des graminées n'avaient diminué. Malgré cela, les animaux ont perdu 15 kg à la mise à l'herbe et il leur a fallu 12 jours pour retrouver leur poids original. Le temps passé à paître (51 %) n'a pas varié au cours des 28 jours, mais celui ...

The effects of turnout date to pasture on cattle weight gain

“…Jannasch et al (2002) found that earlier turnout date had inconsistent results -one year showed no significant effects, and one year showed cattle weight actually decreasing with earlier turnout date. Similarly, Charmley et al (2003) found that earlier turnout date decreased weight gain. On the other hand, Steen (2002) found the opposite -that an earlier turnout date increased weight gain.…”

“…Jannasch et al (2002) and Charmley et al (2003) measured weight gain for a fixed period of time (28 d) after entering pasture, while we and Steen (2002) measured weight gain at fixed dates. Using a fixed period of time removes the effects of differing amounts of time spent in the pasture vs. the barn, thus removing the cause of the turnout date effect.…”

“…For example, Charmley et al (2003) and Jannasch et al (2002) found that earlier turnout date decreased weight gain, while Steen (2002) found the opposite. In order to resolve these contradictions it is important to elucidate the mechanism of the effect of turnout date.…”

“…When grazing short swards animals compensate for the small bite size with increased travel and grazing time (Chacon et al 1978). Cattle grazing short swards often lose weight because they are either unable to obtain sufficient dry matter intake or expend increased energy to obtain the sufficient dry matter (Charmley and Boyd 1997). On the other hand, early turnout may increase weight gain by delaying forage senescence.…”

“…One is that cattle typically lose weight during the transition from confinement to pasture. This weight loss is often attributed to grazing efficiency, forage quality, or inadequate forage intake (Chacon et al 1978;Charmley et al 2003). Even when adequate forage is available cattle may lose weight for a brief period following turnout due to the time required for animals to adapt from confinement feeding to grazing (Charmley and Boyd 1997).…”