Rotational Stocking Management Research Articles

Methane emissions and milk yields from zebu cows under integrated systems

Integrated systems are technologies that potentially increase animal production and environmental preservation, but the effect of these systems on the efficiency and methane emissions of dairy cows is still unknown. This study aimed to compare enteric methane emissions, dry matter intake and performance of grazing dairy cows in integrated systems in the Brazilian Cerrado biome, i.e., crop-livestock integration (CLI) or crop-livestock-forest integration (CLFI). Eighteen Holstein-Zebu cows were randomly assigned to the two production systems (n = 9 for each system) based on Monbasa pasture (Megathyrsus maximus cv. Mombaça; Syn. Panicum maximum) under rotational stocking management. Herbage allowance ranged from 12 to 14% body weight, and cows were supplemented with concentrated feed according to milk yield. Herbage samples were collected by simulated grazing to determine nutritional value. Milk yield was determined weekly. Herbage intake was estimated from fecal output and indigestibility of the pasture dry matter. Fecal output was estimated by the external indicator LIPE®, and dry matter digestibility was estimated by the internal indicator NDFi. Enteric methane emissions were estimated by the SF6 tracer gas technique. Data were collected in three sampling periods to characterize the rainy season, the transition from the rainy season to the dry season and the dry season. Data were analyzed in split plots, with animals within the system as the plot and seasons as the subplot. Statistical significance was considered at P < 0.05. The herbage crude protein content was 35.9% higher on average in the CLFI than in the CLI. In vitro dry matter digestibility was 16.7% lower in the CLI than in the CLFI in the rainy season. Milk yield and feed efficiency were similar between systems and seasons. The total dry matter intake in the rainy season was 34.6% higher in the CLFI than in the CLI. The energy loss, production and yield of methane were 29.8%, 35.0% and 31.3%, respectively, lower in the rainy season than in the other seasons. Enteric methane emissions, milk yield and feed efficiency were similar between the integrated CLI and CLFI systems in the Brazilian Cerrado region.

Sward structure and forage intake rate of elephant grass cv. Napier subjected to strategies of intermittent stocking management

Context Grazing management strategies affect sward structure, changing patterns of foraging and intake, and consequently animal performance. Aims The objective of this study was to evaluate the relationship between sward structure and forage intake rate by cattle grazing elephant grass (Pennisetum purpureum Schumach) cv. Napier subjected to strategies of rotational stocking management. Methods The experiment was conducted in Piracicaba, SP, Brazil, from January 2011 to April 2012. Treatments corresponded to all combinations between two post-grazing conditions (post-grazing heights of 35 and 45 cm) and two pre-grazing conditions (95% and maximum canopy light interception during regrowth; LI). The response variables evaluated at both pre- and post-grazing conditions were: (1) vertical distribution of morphological components; (2) bite rate; (3) bite mass; (4) intake rate; and (5) forage nutritive value (morphological and chemical composition of oesophageal extrusa samples). Key results Bite mass was smaller and bite rate was greater for LI95% swards at pre- and post-grazing, resulting in greater rate of forage intake. The post-grazing height targets affected the morphological and the chemical composition of the forage consumed. Conclusions In general, pastures managed with targets LI95% (pre-grazing) and 45 cm (post-grazing height) resulted in greater leaf percentage and nutritive value of the consumed forage. Implications Adequate grazing management strategies allow for high residual leaf area in pastures, ensuring rapid recovery after grazing. For grazing elephant grass cv. Napier, this corresponded to the combination between the LI95% pre-grazing target and the 45 cm post-grazing height.

Forage mass and canopy structure of Zuri and Quênia guineagrasses pasture under rotational stocking

This work evaluated the productive and structural characteristics of the BRS Zuri and BRS Quênia cultivars under rotational stocking management. The evaluations were divided into five periods according to rainfall regime (high, medium, and low rainfall) during 16 months of the years 2016-2018. Pastures were grazed when canopies intercepted 95% of incident light to stubbles corresponding to 50% of the pre-grazing height. The pre- and post-grazing heights varied as a function of cultivar, with higher values for BRS Zuri [...]

Effect of sward management on the emissions of CH4 and N2O from faeces of sheep grazing Italian ryegrass pastures

Rotatinuous stocking (RN) management is based on animal ingestive behaviour responses, where optimal pre- and post-grazing sward heights are defined to increase nutrient intake per unit of grazing time. We hypothesized that the optimal sward structure and consequently, a high herbage nutritive value in RN treatment results in a greater faecal nitrogen (N) excretion by sheep and consequently, a greater faecal greenhouse gas (GHG) emissions compared with the traditional rotational stocking (RT) management, which is based on a maximum herbage accumulation and harvest. Therefore, the aim of this study was to evaluate the effect of two grazing management strategies (RN and RT) on the amount of dry matter (DM) faecal excretion, faecal N excretion and faecal GHG (CH4 and N2O) emissions from growing sheep grazing Italian ryegrass pastures. In order to evaluate faecal production and N excretion per animal and per ha, a first experiment (1) was carried out: RT - pre and post-grazing sward heights of 25 and 5 cm, respectively and, RN - pre and post-grazing sward heights of 18 and 11 cm, respectively. A second experiment (2) was carried out to measure the CH4 and N2O fluxes from faeces, using the static chamber method. Daily DM faecal and N excretion per animal were higher (P < 0.001) in RN compared with RT treatment. However, when considered daily DM faecal and N excretion per ha, results were lower (P < 0.001) for the RN than the RT treatment. CH4 and N2O emissions from faeces were higher (P < 0.001) in RN compared with RT treatment, both per animal and per hectare. In conclusion, our study showed that the RN grazing management, based on animal behaviour, resulted in a higher daily N excretion per animal and higher CH4 and N2O emissions from faeces of sheep grazing Italian ryegrass pastures. This study contributes to improve GHG national inventories for the subtropical Brazilian climatic conditions, where estimations from CH4 and N2O emissions factors for faeces from growing sheep grazing Italian ryegrass are markedly lower than the values reported by IPCC Default Tier 1.

Effects of grazing intensity and supplementation strategies on Tifton 85 production and on sheep performance

This study evaluated the structural and production characteristics of Tifton 85 (Cynodon spp.) pastures and the performance of lambs under different residual leaf area index (rLAI) and supplementation strategies in tropical conditions. Treatments were the factorial combination of 4- rLAI (0.8; 1.4; 2.0 and 2.6) and 2-supplementation strategies with four replicates in a randomized complete block design. The study was divided into two periods in southeastern Brazil: one in the rainy season and the other in the dry season. Lambs grazed under rotational stocking management and they grazed for 4 days in each pasture while pasture regrowth period was determined by the 95% light interception requirement. In the two evaluated periods the resting period and herbage accumulation decreased linearly and herbage allowance increased linearly with increasing rLAI. The chemical composition and digestibility were affected by rLAI only in the dry season. The dietary supplementation in the rainy season promoted increase of the gain per area but in the dry season the types of supplements did not promote changes in the animals performance. In the rainy season Tifton 85 pastures in rotational stocking can be managed with rLAI between 2.0 and 2.6 with approximately 18 days of regrowth period, and in the dry season with rLAI between 1.4 and 2.0 equivalent to the pasture regrowth period from 58–65 days.

Beef cattle performance in response to Ipyporã and Marandu brachiariagrass cultivars under rotational stocking management

ABSTRACT The objective of this two-year study was to evaluate live weight gain per animal and per area and their relationships with the characteristics of BRS Ipypora (Brachiaria ruziziensis × Brachiaria brizantha) and Marandu (Brachiaria brizantha) pastures. A completely randomized block design was used with two treatments and four replicates. The grazing method was rotational stocking, with variable stocking rate. Stocking rate was adjusted twice a week during the grazing period (six or seven days) and post-grazing canopy height target [...]

Effect of sward height on the fermentability coefficient and chemical composition of Guinea grass silage

AbstractThere is a high correlation between sward height and pasture sward structure. Therefore, in tropical grasslands, taking sward height into account has been a much better strategy in rotational stocking management than considering pre‐defined days of growth. Similarly, sward height could be used to determine the moment when tropical grasses present the best ensilability parameters. This study aimed to identify the sward height at which Panicum maximum cv. Mombaça (Guinea grass) provides the highest fermentability coefficient (FC) and to define the combination of additives that best improves the chemical composition of silage. Two trials were carried out in Selvíria, MS, Brazil, from 2015 to 2016. The first year was used to identify the highest FC, and the second year was used to identify the best combination of eight additives (citrus pulp [CIP], homofermentative and heterofermentative LAB, their combinations and control). Statistical analyses were performed using SAS (p &lt; .05), and one contrast was defined as silage with CIP vs. silage without CIP. The height of 130 cm resulted in the highest FC (31.01). Silages inoculated with CIP had better quality than silages without CIP, due to the high crude protein (8.3 vs. 7.3% DM), DM recovery (98.6 vs. 93.3% DM), low pH (3.92 vs. 4.91) and NH3‐N values (2.49 vs. 14.73% total N). Sward height is a consistent parameter for determining the time of ensiling Guinea grass, and the inclusion of CIP is necessary to raise the silage quality.

Effect of residual leaf area index on spatial components of Tifton 85 pastures and ingestive behaviour of sheep

This study compared the effect of residual leaf area index (rLAI) on the spatial distribution of morphological components of Tifton 85 (Cynodon spp.) pastures and the ingestive behaviour of grazing sheep. Also, it was investigated whether any specific correlation could be found between pasture structural characteristics and sheep ingestive behaviour. Four rLAI treatments (0.8; 1.4; 2.0 and 2.6) with four replications were evaluated per period. Sheep grazed under rotational stocking management and they grazed for 4 days in each pasture while pasture regrowth period was determined by the 95% light interception requirement. Pasture structure was evaluated using inclined point-quadrat, LAI estimates, light interception and leaf : stem ratio. The 2.6 rLAI yielded the highest proportion of dead material in the lower canopy. In the post-grazing period the proportion of leaves increased with increasing rLAI, especially on the canopy surface during the rainy season. In the pre-grazing average pasture height ranged between 19 and 26 cm with dead material and stem observed up to the canopy surface in the dry season. The animals grazed longer on the last day (89.72%) compared with the first day (80.25%) in the dry season. However, they spent less time (11.45%) ruminating in the dry season compared with the rainy season (15.38%), regardless of the grazing day. Grazing time decreased and rumination time increased as rLAI increased. Sheep grazing time correlated negatively with pasture height, before and after grazing. The sheep tend to graze longer on Tifton 85 pastures when rLAI was lower and forage supply was possibly less as on the last grazing day and in the dry season.

Strategies of rotational stocking management on weight gain and productivity of heifers grazing on marandu palisade grass

Pasture management can affect plant growth and interfere with the performance of the animals or the productivity of the production system. Marandu palisade grass swards subjected to year-round grazing by crossbred heifers were evaluated. Three stocking systems were tested: 1) a grazing cycle of 28 days (T28d); 2) when the sward reached a pre-grazing height of 30 cm (T0.3m), and 3) when the sward reached a pre-grazing height of 30 cm under irrigation (T-irrig0.3m). Heifers from treatments T28d and T0.3m were supplemented with dry matter at 1% of BW during winter. Statistical was a completely randomized block split-plot design. The light interception (LI) was higher (P&lt;0.001) for T-irrig0.3m during winter. A lower leaf area index (LAI, P&lt;0.001) was found for T28d, and T0.3m during winter and for T0.3m during autumn. There was an effect of stocking systems (P=0.0055), season (P&lt;0.001) and interaction (P&lt;0.0001) on weight gain (WG), stocking rate and productivity. The lowest WG was obtained in winter for the T-irrig0.3m treatment. The mean WG was 0.45, 0.49 and 0.43 kg/day for T28d, T0.3m and T-irrig0.3m, respectively. Lower productivity (P=0.0155) was observed for T28d when compared to T0.3m and T-irrig0.3m. The productivity rates were 662.2, 741.7 and 758.3 kg WG/ha, per season for T28d, T0.3m and T-irrig0.3m,respectively.

Intake rate and nutritive value of elephant grass cv. Napier subjected to strategies of rotational stocking management

Several research papers on tropical forage grasses have demonstrated that grazing management modifies sward structure that, in turn, alters patterns of ingestive and foraging behavior of the grazing animal. For that reason it has been used to explain adjustments in intake characteristics like bite mass, bite rate, intake rate and nutritive value of the consumed herbage (Fonseca et al. 2012). Tall tussock plants like elephant grass (Pennisetum purpureum) cv. Napier display stem elongation during the vegetative state (da Silva and Carvalho 2005), causing swards to become too tall and out of reach for grazing animals, making efficient grazing management difficult, particularly when long regrowth periods are used. In that context, an increase in defoliation frequency can improve herbage intake and nutritive value (Palhano et al. 2007), by favoring leaf elongation as opposed to stem elongation and senescent material accumulation throughout successive grazing cycles. Against that background, the objective of this experiment was to evaluate the components of short-term herbage intake (intake rate, bite mass and bite rate) and nutritive value of the consumed herbage from elephant grass cv. Napier subjected to rotational stocking management defined in terms of preand post-grazing management targets.

Rotational stocking management affects the structural and nutritional characteristics of Guinea grass swards and milk productivity by crossbred dairy cows

The type of stocking system can affect sward canopy structure, changing the nutritional value of herbage and livestock production. The present study evaluated structural and nutritive features of Guinea grass (Panicum maximum Jacq. var. Tanzânia) swards and the composition and yield of milk produced by crossbred cows fed this herbage in a rotational stocking system over cycles from Spring to Autumn. Two stocking systems were tested, in which cattle were allowed to graze: (1) after grazing cycles of 30 days (T30d); or (2) when the sward reached a pre-grazing height of 70cm (T0.7m). Five grazing cycles, each consisting of a sward recovery period followed by 2 days of grazing, were evaluated in each stocking system using a completely randomized block design and repeated measures with 2 repetitions per stocking system (each composed of a set of sixteen 4000m2 paddocks grazed sequentially). Four 1m×1m sward patches were collected, constituting one sample per paddock, which was used to evaluate pre-grazing herbage mass, leaf, stem and dead matter (dry mass per area), crude protein (CP), neutral detergent fiber (NDFom), acid detergent fiber (ADFom) and hemicellulose (HEM). Cows received daily supplementation of 4kg concentrate. Stocking rate, milk production and composition were evaluated in each grazing cycle. The T30d stocking system produced higher (P=0.0014) pre-grazing height than T0.7m (0.83 vs 0.69cm), had higher (P=0.0071) light interception (94 vs 91%) and higher (P=0.0233) leaf area index (5.2 vs 4.5). In addition, T30d exhibited larger (P=0.0204) herbage mass than T0.7m (7276 vs 6187kg MS/ha), higher (P= 0.0243) leaf dry mass per area (2618 vs 2294kg/ha) and higher (P<0.0001) stocking rate (6.2 vs 5.7animal/ha). The grazing cycle affected sward composition, with T30d producing higher (P=0.0060) leaf NDFom. Milk production and composition was not affected by the stocking systems, as follows (T30dvs T0.7m): 20.12 vs 20.94kg milk production per cow/day; 31.4 vs 31.9gfat/kg, 29.9 vs 30.2gprotein/kg, 43.7 vs 44.6glactose/kg, 114.8 vs 116.5g/kg total solids and 12.85 vs 12.86mg/dL ureic nitrogen. Stocking system therefore affects the nutritive value of sward. Stocking management allowing a 30-day grazing cycle for Guinea grass sward (T30d) produces higher forage mass, supporting a higher stocking rate and thereby increasing productivity in dairy farm.

Herbage accumulation and grazing losses on Mulato grass subjected to strategies of rotational stocking management

Grazing management strategies affect not only herbage accumulation but also the efficiency of grazing. This study aimed to evaluate herbage accumulation (leaf, stem and dead material), grazing efficiency and losses of mulato grass (a Brachiaria ruziziensis × Brachiaria brizantha cv. Marandu hybrid) subjected to strategies of rotational stocking management. Treatments consisted of combinations between two post-grazing heights (15 and 20 cm) and two pre-grazing conditions (95 % and maximum canopy light interception (LI)) assigned to experimental units (1200-m² paddocks) according to a 2 × 2 factorial arrangement and a randomized complete block design, with four replications. The experiment was carried out from Jan 2008 to Mar 2009. Season of the year influenced almost all studied variables, resulting in a common pattern of response that was determined by pre- and post-grazing management targets. Herbage accumulation was greater on swards managed at 95 %, with higher accumulation of leaves and lower accumulation of stem and dead material in relation to those managed at maximum LI (99 %) during the entire experimental period. On the other hand, herbage removal by grazing was larger on swards managed at 99 % LI, which was compensated for by the smaller number of grazing cycles and larger losses due to grazing under those circumstances. Under rotational stocking, the pre-grazing LI of 95 % and post-grazing height of 20 cm resulted in efficient grazing and high producing leafy pastures, highlighting the potential of Mulato grass pastures for animal production.

Tiller population density and tillering dynamics in marandu palisade grass subjected to strategies of rotational stocking management and nitrogen fertilization

The objective of this experiment was to evaluate tiller population density and the dynamics of the tillering process in marandu palisade grass subjected to strategies of rotational stocking management and nitrogen fertilization. Treatments corresponded to combinations between two targets of pre-grazing conditions (sward surface height of 25 and 35 cm) and two rates of nitrogen application (50 and 200 kg ha-1 year-1), and were allocated to experimental units according to a 2 x 2 factorial arrangement in a randomised complete block design, with four replications. The following response variables were studied: initial (TPDi), intermediate (TPDm) and final (TPDf) tiller population density as well as the rates of tiller appearance (TAR) and death (TDR) and the tiller population stability index (SI). TPDi was similar to all treatments, with differences in tiller population density becoming more pronounced as the experiment progressed, resulting in larger TPDf on swards managed at 25 cm pre-grazing height. Tiller death was larger on swards managed at 35 cm, with differences in tiller appearance being recorded only from February 2010 onwards. Stability of tiller population was higher on swards managed at 25 cm pre-grazing height. Overall, there was no effect of nitrogen on the studied variables, and the most adequate grazing strategy corresponded to the pre-grazing height of 25 cm, regardless of the nitrogen application rate used.

An alternative rotational stocking management designed to favour butterflies in permanent grasslands

AbstractGrassland butterflies are on the decline throughout Europe. We tested an ‘alternative rotational stocking’ (ARS) strategy based on theoretical and practical aspects of grassland ecology, designed to increase butterfly diversity while also meeting farmers’ production objectives. This management strategy implies taking animals away from one subplot of the rotation during the main flowering period. Its feasibility and benefits on butterfly diversity were tested by comparing ARS with continuous stocking (CS) in plots grazed by cattle at the same stocking rate: high in 2005 and 2006 then lenient in 2007 and 2008. At the high stocking rate, butterfly abundance (21·9 vs. 8·3, P &lt; 0·01) and butterfly species richness (7·4 vs. 3·7, P &lt; 0·001) were significantly higher in ARS than in CS plots, matching the increase in pasture flowering intensity and sward structural diversity. ARS was led according to the pre‐planned schedule in 2005, but in 2006, the number of heifer grazing days in ARS was reduced by 19% because of unfavourable spring grass growth. At the lenient stocking rate, ARS was less beneficial for butterflies (abundance: 17·4 vs. 13·0, P &lt; 0·10; species richness: 5·9 vs. 5·2, P = 0·35) but would present less risk for farmers in terms of providing livestock with sufficient forage. Alternative rotational stocking thus has potential to be integrated into grassland‐based systems, but would require earlier grazing on the excluded subplot of the rotation in the event of unfavourable grass growth during spring.

Soil bulk density and biomass partitioning of Brachiaria decumbens in a silvopastoral system

Shade in silvopastoral systems improves the thermal comfort of animals, but it may also affect the pasture productivity and can contribute to soil compaction in the shaded areas due to the increase in the number of animals looking for comfort. The effect of grazing at various distances from tree rows (under the tree canopy, at 6 and at 12 m away from the trees) on the soil bulk density and on the aerial and root biomass of Brachiaria decumbens was evaluated in both the dry and the rainy seasons. The study was carried out on an Orthic Ferralsol in a randomized block design with two replications. Tree rows were composed of Eucalyptus grandis and Acacia mangium species, and the paddocks were submitted to a rotational stocking management, using Holstein (Bos taurus) × Zebu (Bos indicus) heifers. The shade intensity in the pasture decreased with an increasing distance from the tree row. Soil bulk density did not vary with the distance from the tree row, but varied seasonally, being greater in the rainy season (1.47 g cm-3) than in the dry season (1.28 g cm-3). Green forage and root mass, expressed as dry matter, were lower under the tree canopy and were greater in the rainy season. There were decreases of 22.3 and 41.4% in the aerial and root biomasses, respectively, in the tree rows. The greatest shoot/root ratio for B. decumbens under moderate and intensive shading indicates a modification in the forage biomass allocation pattern that favours the aerial development in detriment of the root system.

Ingestive behaviour, herbage intake and grazing efficiency of beef cattle steers on Tanzania guineagrass subjected to rotational stocking managements

The objective of this experiment was to evaluate the ingestive behaviour, herbage intake and grazing efficiency of beef cattle steers grazing on Panicum maximum Jacq. cv. Tanzania subjected to different rotational stocking intensities. Treatments corresponded to two post-grazing conditions (residues of 25 and 50 cm) associated with a pre-grazing condition of 95% sward canopy light interception during regrowth (LI). The grazing time increased linearly with the duration of the occupation period (475 to 630 minutes/day). On paddocks grazed down to a residue of 25 cm, the bite rate increased linearly along the occupation period, with an average of 42.5 bites/minute. On paddocks grazed down to a residue of 50 cm, the bite rate was stable and equal to 39 bites/minute. There was no difference in herbage intake between grazing intensities. However, grazing at 25 cm residue resulted in greater herbage removal (68.0 vs. 45.6%) and greater grazing efficiency (90.4 vs. 49.8%) than grazing at 50 cm residue. Post-grazing residues of Tanzania guineagrass under rotational stocking management may be set at either 25 or 50 cm, since the herbage intake was not affected within this grazing intensity range. However, herbage removal and grazing efficiency were reduced with the 50 cm post-grazing height and grazing time increased with long occupation periods.

Pasture Forages, Supplementation Rate, and Stocking Rate Effects on Dairy Cow Performance

Objectives were to evaluate effects of forage species, stocking rate, and supplementation rate on performance and physiology of grazing lactating Holstein cows under intensive rotational stocking management during summer. Eight treatments were arranged in a 2×2×2 factorial design. Animals (n=62) grazed pastures of Tifton 85 bermudagrass or Florigraze rhizoma peanut, a tropical legume. Low and high stocking rates were 7.5 and 10.0 cows/ha for bermudagrass and 5.0 and 7.5 cows/ha for rhizoma peanut. Within each forage-stocking rate combination, cows were fed supplement at 0.33 or 0.5kg of supplement (as-fed basis)/kg daily milk production. Cows grazing rhizoma peanut pastures produced more milk (16.9 vs. 15.4kg/d) but had higher rectal temperatures (39.4 vs. 39.1°C). Milk production per cow was improved at the higher stocking rate for bermudagrass but was reduced at the higher stocking rate for peanuts. Increasing supplementation rate boosted plasma glucose, milk production, and milk protein percent. Increased supplementation rate had a greater positive impact on milk production of cows grazing bermudagrass compared to rhizoma peanut (21.9 vs. 10.6% increase) due to a lower substitution of grain for forage intake. Organic matter intakes of forage, supplement, and total diet were greatest by cows grazing rhizoma peanut pastures and averaged 12.4, 6.1, and 18.5kg/d compared to 9.2, 5.4, and 14.6kg/d for cows grazing bermudagrass. Despite lower individual feed intake and performance, production per unit land area was 29% greater (112 vs. 90kg of milk/ha per d) for cows grazing bermudagrass due to the greater stocking rate possible with that forage. Only cows supplemented at the high rate and kept at the high stocking rate on bermudagrass maintained body weight. Cows on other treatments lost body weight. Tifton 85 bermudagrass appears to be an excellent summer forage for dairy cows grazing in the southeastern U.S. given its nutritive value characteristics and high yields. Optimum stocking rate may be as high as 10 cows/ha during times of peak growth of forage for low-to-moderately producing cows fed supplement. Furthermore, the positive milk production response to additional supplement when cows grazed Tifton 85 pastures (0.8kg/kg of supplement), indicates the value of providing supplement to cows grazing this moderate quality forage.

Effects of grazing sequence and condensed tannins on ingestive behaviour, herbage intake, and performance of lambs grazing Yorkshire fog pasture

A grazing experiment was conducted using Yorkshire fog (Holcus lanatus cv. Massey Basyn)/white clover (Trifolium repens cv. Grasslands Tahora) pasture to assess the grazing behaviour, diet selection, herbage intake, and performance of lambs as affected by low concentrations of condensed tannin (CT) in the grass, and grazing sequence, under rotational stocking management in summer 1994/1995, in New Zealand. Sixty spring‐born castrated male lambs were used in the experiment. Twelve lambs were slaughtered at the start of the experiment to measure carcass weight. Another 48 lambs were allocated to two groups in sets of twenty‐four to graze eight paddocks rotationally in a Leader/Follower sequence. Half of the lambs within each group were drenched with 10 g polyethylene glycol (PEG: mol. weight 3350) twice daily at 0830 and 1630 hours and the remaining lambs were drenched with water as a control. There were higher proportions of grass leaf and white clover and lower proportions of grass stem and dead material in the Leader sward than in the Follower sward, and correspondingly higher proportions of green grass and white clover and a smaller proportion of dead material in the diet samples selected from Leader swards. Leader lambs had greater intake per bite (79 versus 64 ± 3.9 mg OM per bite, P < 0.001), higher total N concentration (2.67 versus 2.35 ± 0.065%, P < 0.01) and in vitro OMD (78 versus 72 ± 0.7 %, P < 0.001) in the diet, and spent more time grazing (660 versus 620 ± 7 min, P < 0.001) than Followers, and their herbage DOM intake was significantly greater (56 versus 43 ± 0.8 g kg−1 W0.75 d−1, P < 0.001). Leader lambs had greater liveweight gain (107 versus 37 ± 5.0 g d−1, P < 0.001), greater carcass weight (15.0 versus 12.5 ± 0.2 kg, P < 0.001), and more wool growth (109 versus 80 ± 2.9 mg 100cm−2 d−1, P < 0.001) than Followers. There was no significant difference in CT concentrations between the diets selected from the Leader and Follower swards (2.59 versus 2.26 + 0.165 g kg−1 DM). Consistent increase in rumen ammonia concentration by PEG administration indicated that the low concentrations of CT in Yorkshire fog reduced the rate of protein degradation in the rumen. However, there were no significant effects of CT on herbage intake, body growth, and wool growth rate of lambs.