Impacts of Spatial Patterns in Pasture on Animal Grazing Behavior, Intake, and Performance

Abstract

Control over the quantity and quality of food ingested by grazing ruminants in temperate pasture systems remains elusive. This is due in part to the foraging choices that animals make when grazing from communities of mixed plant species. Grazing behavior and intake interact strongly with the feed supply–demand balance, pasture composition, and grazing method. These interactions are not completely understood, even for relatively simple pasture communities such as a perennial ryegrass (Lolium perenne L.)–white clover (Trifolium repens L.) mixture. When offered a free choice between these species, ruminants exhibit a partial preference for clover compared to grass (about 0.7:0.3) and have a higher intake rate from clover but do not graze to maximize their daily intake of dry matter (DM). When monocultures of grass and clover are offered as a free choice in 50:50 area ratio, animal performance is no different than from a clover monoculture alone. Thus, all of the feeding value benefits of clover are available when only 0.5 of the grazing area is sown to clover. These observations accord with the satiety theory and imply that there are constraints to eating pure clover that animals can overcome by adding grass to their diet, provided their ability to locate and ingest each food is not seriously limited. The challenge for grassland management is to present feed to animals at pasture in ways that allow them to meet their dietary preferences, while also allowing high rates of animal production per hectare.

Effects of herbage allowance of native grasslands in purebred and crossbred beef cows: metabolic, endocrine and hepatic gene expression profiles through the gestation–lactation cycle

“…In parallel, during this period, insulin and glucose concentrations decreased. These results would reflect a period of NEB, probably as a consequence of decreased forage intake (75% to 90% of NRC energy requirements for gestation in the present study) because of reduced forage mass and height in winter (Chapman et al, 2007), along with the cows' increased energy requirements for grazing (Brosh, 2007) and gestation (Bell, 1995).…”

“…This would indicate a differential glucose homeostasis mechanism depending on G probably associated with DM and energy intake, despite the fact that both groups were grazing low HA. Greater PC mRNA at the end of the fall (−165 days) would suggest that LO-PU cows were using more lactate and amino acids (and less propionate) as gluconeogenic precursors (Drackley et al, 2001), whereas CR cows increased their use during early winter (−165 to − 45 days) when forage mass and height and thus dry matter intake (Chapman et al, 2007) decrease.…”

“…Hepatic ACADVL mRNA was increased during the NEB of winter gestation (from − 45 to − 15 days) and at +60 days during the lactation period. This may reflect the energetic demands of the maternal metabolism during gestation or milk production as forage mass and height (winter gestation) or quality (less CP, more ADF at +60 days) limited their DM and energy intake (Chapman et al, 2007). Increased hepatic ACADVL would allow hepatocytes to deal with the overflow of NEFA mobilized from the adipose tissue, increasing mitochondrial β-oxidation (Loor, 2010).…”

“…Grazing intensity of native pastures, controlled through herbage allowances (HAs), determines changes in herbage mass and height (Soares et al, 2003) that can affect energy intake (Chapman et al, 2007) and energy requirements, through modifying animal BW and production (Soares et al, 2003) and grazing activity (Brosh, 2007), impacting cows' energy balance. It has been shown that the complex system of adaptation to changes in energy balance can differ considerably between cows (Jorritsma et al, 2003), and that this variation in the cow's ability to successfully adapt to periods of NEB may have a genetic basis (Ingvartsen et al, 2003).…”

Comparison of intake and digestibility of fresh Digitaria decumbens grass fed to sheep, indoors or at pasture, at two different stages of regrowth

“…Thus, the real nutritional implications of such a trade-off between diet quality and forage intake for nutrition at pasture are unknown. Indeed, Chapman et al (2007) have highlighted the shortage of experiments to explain the nutritional basis of diet selection for temperate pastures, such as perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.) mixtures. This is especially true for tropical pastures.…”