Timing of herbage allocation in strip grazing: Effects on grazing pattern and performance of beef heifers1

Abstract

The timing of grazing bouts (GB) determines how cattle allot time to meet their nutritional needs. Net photosynthesis and evapotranspirational losses increase herbage nonstructural carbohydrate and DM concentrations, which may lead to longer and more intense GB at dusk. Hence, linking the grazing pattern, plant phenology, and herbage allocation time emerges as an option to manipulate the GB and nutrient intake. The objectives of this work were to analyze grazing behavior and performance of beef heifers when herbage allocation was at 0700 each morning (MHA) or at 1500 each afternoon (AHA). Two pairs of experiments were conducted during the winter and spring examining behavior and performance. Measurements were grazing, rumination, and idling times during daylight hours, and their patterns, as well as bite rate, ADG, change in BCS, and daily herbage DMI. In the behavioral experiments, 8 heifers strip-grazed annual ryegrass (Lolium multiflorum Lam.). The grazing, rumination, and idling times as well as bite rate were measured and also analyzed per time of day. In the performance experiments, 48 beef heifers strip-grazed annual ryegrass in 2 groups according to treatments. Daily DMI, ADG, and changes in BCS were analyzed. The AHA increased daily idling time (P < 0.01) and decreased grazing time (P < 0.01). The AHA concentrated grazing time in the evening, when bite rate was greater (P < 0.01). The daylight rumination time varied by time of day (P < 0.01), but total daylight rumination time did not differ (P = 0.11). With AHA, rumination time and idling time were concentrated in the morning and afternoon. In the performance experiment during the winter, there was a treatment x week effect (P < 0.01) for ADG and change in BCS. Beginning in wk 4, heifers in AHA gained 150 g of BW and 0.0145 points of BCS more than those in MHA (P < 0.05) per day. In the spring, AHA increased ADG by 549 g and 0.0145 points of BCS more than those in MHA (P < 0.05) per day during the entire 6 wk. The herbage DMI (kg/d) did not differ in winter (AHA, 5.0 vs. MHA, 4.5) or spring (AHA, 5.6 vs. MHA, 5.0). These results suggest that timing of herbage allocation alters grazing, rumination, and idling patterns; AHA leads to longer and more intense GB when herbage has greater quality, which improves cattle performance.

Effect of herbage depletion on short-term foraging dynamics and diet quality of steers grazing wheat pastures1

“…As the extent of herbage depletion increased (P < 0.05), steers increased the feeding station rate, distance walked while eating, and the area covered while grazing, as well as tended (P = 0.09) to take fewer bites per feeding station. These results are consistent with the results presented by Gregorini et al (2006), who found that at the same mass, but different herbage availability and accessibility of wheat pastures, steers changed their foraging dynamic, increasing the eating step rate and reducing residence time per feeding station when accessibility decreased.…”

“…The quality of potentially consumed herbage in each grazing scenario was estimated following the methodology used by Gregorini et al (2006). In brief, 9 herbage samples were taken immediately after the grazing sessions mimicking the harvesting movements and bite depth of steers on ungrazed areas next to bitten areas.…”

Grazing Behavior and Locomotion of Young Bulls Receiving Different Nutritional Plans in a Tropical Pasture

“…Casagrande et al (2011) observed, in a tropical pasture, that less than 30% of cattle were grazing before 08:00 h, but after 09:00 h, 70% of cattle were grazing. On the other hand, Gregorini et al (2006) using Angus heifers ( Bos taurus ) in temperate pastures found longer grazing time at 07:00 h to 11:00 h than at 11:00 h to 13:00 h. These differences in grazing behavior may be due to animal adaptation, where Nellore ( Bos Indicus ) is better able to regulate body temperature in response to heat stress than cattle from a variety of B. taurus (Hansen, 2004) and they may have develop different grazing habits.…”

Effects of dietary total non-structural carbohydrates and folic acid and vitamin B12 supplement on growth and meat quality of yearling steers in a forage-based beef production system

“…These effects may be explained by the greater dry matter (DM) and total nonstructural carbohydrate (TNC) contents of grass grazed in the afternoon. Greater concentrations of TNC have also been observed in annual ryegrass (Gregorini et al 2006), timothy (Morin et al 2012a), tall fescue (Fisher et al 1999) and alfalfa (Morin et al 2012b) harvested in the afternoon compared with the morning. Dumoulin et al (1991) demonstrated that dairy calves supplemented with folic acid had a greater ADG than unsupplemented calves around weaning.…”

“…Similarly, allocation of a new pasture strip in the afternoon rather than in the morning increased milk yield of dairy cows (Orr et al 2001) and average daily gain (ADG) of beef heifers (Gregorini et al 2006). These effects may be explained by the greater dry matter (DM) and total nonstructural carbohydrate (TNC) contents of grass grazed in the afternoon.…”