The herbage intake and performance of set-stocked suckler cows and calves

Groups of eight Hereford × Friesian cows and their South Devon cross calves were set stocked over a 24-week grazing season at 3·23 (low), 3·21 (medium) or 4·24 (high) cows ha^-1 together with their calves. For the first 8 weeks only two-thirds of the total area was grazed. Increasing the stocking rate from low to medium reduced daily milk yield and cow and calf liveweight gains by 1·2, 0·24 and 0·29 kg d^-1 respectively, and from medium to high by 1·2, 0·24 and 0·23 kg d^-1. The main sward factor influencing faecal output and herbage intake was the quantity of organic matter on the pastures but the digestibility of the herbage selected also exerted a significant effect on the intake of cows. Major depressions in the herbage intake of cows occurred once the average sward height fell below 7 cm. Output of calf live weight was 628, 658 and 743 kg ha^-1 for the 3 stocking rates from low to high, and for cows 246, 179 and 30 kg ha^-1. It was concluded that decisions on pasture management should be taken in relation to the cow rather than the calf on set-stocked swards.     

Concentrate supplementation of grazing dairy cows. 2. Effect of concentrate composition on herbage intake and milk production

The effect of feeding either traditional concentrates containing starch or high quality fibrous concentrates on the performance of grazing dairy cows was examined in a trial in which cows were given concentrates with either 350 g starch and sugars (kg dry matter (DM))^-1 (high-starch) or 100 g starch and sugars (kg DM)^-1 (high-fibre). The swards used consisted predominantly of perennial ryegrass and were usually aftermaths following cutting. Each area was grazed for 3 or 4 d at each grazing and a two-machine sward-cutting technique was used for estimating herbage intake.
The effect of concentrate composition on the herbage intake of grazing cows at a high daily herbage allowance of 28 kg OM above 4 cm cutting height was investigated in 1983 and 1984. With 54 kg OM d^-1 of high-starch concentrates the mean herbage intake was 11·5 kg OM d^-1 per cow while cows fed 5.3 kg d^-1 of high-fibre concentrates consumed on average 12–6 kg OM d^-1. The mean substitution rate of herbage by concentrates was reduced from 0·45 kg herbage OM (kg concentrate OM)^-1 with the high-starch concentrate to 0·21 with the high-fibre concentrates.
The effect of the treatments on milk production was studied in 1984. The cows consumed 5·5 kg OM d^-1 as concentrates and grazed at a lower herbage allowance of 19 kg OM above 4 cm cutting height. With high-fibre concentrates milk production and 4% fat-corrected milk production were 13 and 1·8 kg d^-1, respectively, higher than with the high-starch treatment. The daily live weight gain with the high-starch concentrates was 0·17 kg per cow more than with the high-fibre concentrates.     

The effect of herbage allowance on intake and performance of ewes suckling twin lambs

The effect of herbage allowance on the herbage intake and performance of ewes and their twin lambs at pasture was investigated. Daily herbage allowances of 40,80.120 and 160 g organic matter (OM) kg^-1 ewe live weight, based on herbage mass measured to ground level, were offered during the first 12 weeks of lactation.
The sheep were grazed rotationally around four paddocks of a perennial ryegrass pasture for 7-day periods and herbage mass, extended tiller length and digestibility of the herbage consumed by the animals were estimated. Herbage intake by the ewes was estimated during weeks two to twelve and live weights were recorded weekly: during the last two weeks of the experiment grazing behaviour of one ewe on each treatment was recorded continuously.
Herbage intakes by the ewes (164, 1–81, 2–42 and 268 ± 0153 kg d^-1) and live weight gains of the lambs (202, 245, 274 and 300 ± 7–3 g d^-1) increased with increasing herbage allowances. Herbage intakes by the ewes and growth rates of their lambs increased up to a herbage allowance which was over five times the amount of herbage eaten by the ewes.
As the animals reduced herbage mass and sward height, biting rates by the ewes during grazing increased by 4 (± 0·08) bites min^-1 cm^-1 and masticating rates decreased. Mastications reached a maximum of 90 (± 3·5) min^-1 at a sward surface height of 9 cm.     

The effect of herbage allowance on daily intake by Creole heifers tethered on natural Dichanthium spp. pasture

Two experiments were carried out in Guadeloupe to estimate the organic matter intake (OMI) and digestibility (OMD) of a Dichanthium spp. sward, grazed by tethered Creole heifers [mean live weight (LW) 202 ± 2·0 kg], at three daily herbage allowances. Experiment 1 examined herbage allowances of 16, 25 and 31 kg of dry matter (DM) d^–1 on a fertilized sward at 21 days of regrowth whereas, in experiment 2, lower allowances of 11, 15 and 19 kg DM d^–1 were examined on the same sward, which was unfertilized and grazed at 14 days of regrowth. In each experiment, the herbage was grazed with three groups of two heifers in a 3 × 3 Latin square design. Sward characteristics were described before grazing. OMI was calculated from total faecal output, and OMD was predicted from the crude protein (CP) content of the faeces. The amount of herbage defoliated by the heifers was also estimated on tillers selected at random.
Organic matter intakes were on average 26 g and 19 g OM kg^–1 LW, and OMD values were 0·740 and 0·665 for Experiments 1 and 2, respectively, and were not affected by allowance. In Experiment 1, the herbage quality was high [0·50 of leaf and 116 g CP kg^–1 organic matter (OM)] for a tropical forage, whereas in Experiment 2, the quality of the herbage (0·27 of leaf and 73 g CP kg^–1 OM) was lower. These differences were reflected in differences in intake and digestibility in the two experiments.
The experimental tropical Dichanthium spp. swards can have intake characteristics similar to those of a temperate sward.     

The effect of offering a brewers grains/treated straw supplement to grazing dairy cows

In a two-year study, set stocked dairy cows were offered a mixture of brewers grains and sodium hydroxide-treated straw (1:1 on a dry matter basis)for 1 h daily. The experiments lasted for 20 and 19 weeks, mean supplementary (buffer) feed dry matter intakes were 3·0 and 3·4 kg d^-1 and mean sward heights (rising plate meter) were 4·9 and 4·7 cm in 1988 and 1989 respectively. The control group received no supplementation. The buffer feed significantly increased milk yield (26·3 vs 24·6 kg d^-1 and 28·6 vs 26·3kg d^-1 in 1988 and 1989 respectively), increased liveweight gain (0·27 vs 0·13 kg d^-1 and 0·27 vs 0·17 kg d^-1) and increased effective stocking rate (5·17 vs 4·69 cows ha^-1and 5·10 vs 4·53 cows ha^-1). There were no significant effects on milk composition. The greatest responses in milk production were found in the late grazing season.     

Grass height as an indicator for supplementary feeding of continuously stocked dairy cows

Three groups of cows were continuously stocked on pasture and offered supplementary concentrates according to the herbage height measured weekly with a grass disc. Concentrates were offered when the mean herbage height fell below 9 cm for treatment A, 7 cm for treatment B and 5 cm for treatment C at a rate of 1 kg d^-1 for each 0·2-cm decline below these threshold levels. If the herbage height declined by more than 1·2 cm (8 kg concentrates d^-1) hay was offered in addition ad libitum. The stocking rates for all three treatments were 5·2, 3·2 and 3·2 cows ha^-1 for three successive 8-week periods. For treatments A, B and C the mean concentrate DM intakes were 3·2, 1·2 and 1·2 kg d^-1 (treatment A also received 0·2 kg hay DM d^-1), and the mean daily milk yields were 17·2, 16·2 and 15·2 kg respectively. The increasing level of supplementary feeding from treatment C to A also resulted in an increase in liveweight and body condition score change, and a reduction in milk fat.     

Effects of concentrate supplementation and herbage allowance on the performance of grazing suckling lambs

An experiment was conducted to examine the effect of concentrate supplementation on the performance of suckling lambs while grazing at variable levels of herbage allowance. Twenty-four ewes suckling twin lambs were allocated 55 d after lambing between four grazing treatments (two levels of herbage allowance × two levels of supplementation) in a 2×2 factorial design. The sward consisted of Tall Fescue and was grazed rotationally.
Daily herbage organic matter (OM) allowances were 57.0 (H) and 38.5 (L) g OM kg LW⁻¹ above 1·5 cm cutting height. Lambs were either supplemented (S) ad libitum with high-moisture whole maize grain or unsupplemented (U).
Supplement intake during the 60-d grazing period was 16 kg DM and 17.5 kg DM respectively for LS and HS lambs. The effect of supplementation on lamb growth rate differed significantly between allowances: at the low allowance level, supplementation increased growth rate (287 g d⁻¹ vs 226 g d⁻¹), whereas it had no effect at the high level (277 g d⁻¹ vs 276 g d⁻¹). Growth rate of unsupplemented lambs was significantly reduced at the low level of allowance compared to the high level (226 g d⁻¹ vs 276 g d⁻¹). The effect of sward height on time spent grazing by unsupplemented lambs is described during the defoliation of a plot.     

The intake and performance of cashmere goats grazing sown swards

An experiment was conducted to examine the relationships between sward surface height and the intake and liveweight gain of lactating female goats and their single kids and of 12-month-old castrated male goats continuously grazing grass pasture. Herbage intake was measured using the n -alkane marker technique. Goats grazed the experimental area from May to August at nominal sward heights of 3–4, 5–6, 7–8 and 9–10 cm. Sward heights achieved were variable but were consistently ranked in treatment order.
The herbage intake of females [57-140 g DM (kg LW^0.75)⁻¹ d⁻¹] and castrates [26-88 g DM (kg LW^0.75)⁻¹ d⁻¹] increased linearly with sward height over the range 3.2-11.0 cm. The liveweight change of females and castrates reflected the pattern of change in sward height.
The herbage intake of kids [17-41 g DM (kg LW^0·75)⁻¹ d⁻¹] was not related to sward height, but there was a consistent increase in liveweight gain with sward height from 98 to 129 g d⁻¹. The herbage intake of kids did not increase with age with means of 25–29 g DM (kg LW 0·75 d⁻¹ for kids aged 9–17 weeks.
There was evidence that all classes of goat selected green leafy material of high digestibility.     

Comparative studies of the influence of sward conditions on the ingestive behaviour of cows and sheep

Separate groups of non-lactating cows and wether sheep grazed at similar herbage allowances for two successive 5-d periods on swards that had previously been grazed frequently or infrequently with the intention of creating differences in canopy structure. Measurements were made of sward structure and composition, ingestive behaviour and diet composition. The preliminary treatments had little effect upon either sward conditions or animal behaviour.
Herbage mass was reduced from 4020 kg dry matter (DM) ha⁻¹ to 3290 kg DM ha⁻¹ on average over a 5-d grazing period as a consequence of the relatively low grazing pressure imposed. This resulted in a mean decline in intake per bite of 28%, and the changes for cattle and sheep did not differ significantly. However, there was a marked difference in the other behavioural responses of the two species; in the sheep biting rate fell and grazing time increased with declining herbage mass, particularly in the sward previously grazed infrequently, whereas the changes in the cattle were small.
Differences in the botanical composition of the herbage eaten by cattle and sheep were minor, but there was a small but consistent advantage to the sheep in the digestibility of the herbage eaten.
In the first of the two periods the variation in surface height after grazing was substantially greater for sheep-grazed than for cattle-grazed swards, indicating more patchy grazing by the sheep.
Estimates of daily herbage organic matter (OM) intake calculated from ingestive behaviour variables were high (means 38 and 32 g (kg LW) ⁻¹ for cattle and sheep respectively) and usually declined substantially over a grazing period.     

Concentrate supplementation of grazing dairy cows

Two experiments are described in which twenty-four spring-calving Dutch Friesian cows were allocated between six grazing treatments (two levels of daily herbage allowance × three levels of daily concentrate intake) in a 2 × 3 factorial design. The swards consisted predominantly of perennial ryegrass. A two-machine sward-cutting technique (with correction for herbage accumulation during grazing) was used for estimating herbage intake by cows which grazed swards for 3 or 4d. Experiment 1 was carried out for 16 weeks of the grazing season of 1981 and experiment 2 for 18 weeks in 1982.
Daily herbage OM allowances in both experiments were 16 and 24 kg per cow above 4 cm cutting height. Daily concentrate OM intake ranged from 0.8 to 5.6 kg per cow. The effect of concentrates on herbage intake differed significantly between allowances. At the low allowance level and at daily concentrate OM intakes of 0.8, 3.2 and 5.6 kg per cow daily herbage OM intake was 10.9, 10.6 and 10.4 kg per cow respectively and the mean substitution rate of herbage by concentrates was only 0.1. At the high allowance level and at daily concentrate OM intakes of 0.8, 3.2 and 5.6 kg per cow daily herbage OM intake was 14.8, 13.6 and 12.4 kg per cow respectively and mean substitution rate was 0.5 kg herbage OM (kg concentrate OM)⁻¹.     

Herbage intake and milk production by grazing dairy cows. 3. The effect of grazing severity under continuous stocking

The effects of severity of grazing on the herbage intake and milk production of continuously stocked British Friesian cows calving in February–March were examined in three experiments conducted in the years 1976–78 (experiments 1–3 respectively) using a put-and-take technique. In experiment 1 four grazing severities were imposed by maintaining swards with different herbage masses (2500, 3000, 3500, 4000 kg OM ha^-1); in experiments 2 and 3 there were two severities of grazing maintained by keeping swards canopies at constant heights of 5 and 7 cm (experiment 2) and 5 and 7·2 cm (experiment 3). Cows were reallocated to treatment every 8 weeks in experiments 1 and 2 and there were three periods, whereas they all grazed throughout a 23-week period on the same treatment in the final trial.
A decrease in the quantity of herbage on offer or in sward height reduced herbage intake and milk production in all experiments. Mean daily herbage OM intakes were 11·2, 12·2, 12·2 and 12·2 kg respectively in experiment 1, 12·2 and 13·2 kg respectively in experiment 2 and 12·2 and 152 kg respectively in experiment 3. Mean daily solids–corrected milk yields were 14·2, 15·2, 15·2 and 16·2 kg respectively in experiment 1, 14·2 and 16·2 kg respectively in experiment 2 and 12·2 and 17·2 kg respectively in experiment 3. It was apparent from the data obtained in the first two trials that grazing at a sward canopy height of 7 rather than 9 cm had little effect, but that at 5 cm there were significant depressions in both herbage intake and milk production. Milk yield was depressed to a greater extent when cows were kept on the same treatment for the whole season.     

Herbage intake and liveweight gain of bulls and steers continuously stocked at fixed sward heights during autumn and spring

Two experiments were conducted to examine the relationship between sward surface height, herbage intake and liveweight gain in beef cattle grazed on pasture. In Experiment 1, two 'animal types' (18 Charolais × Angus steers and 18 Friesian bulls) were continuously grazed for 22 days during the late autumn on replicated swards maintained at sward surface heights of 6, 10 and 15 cm. Herbage intakes, assessed from the faecal concentration of chromium delivered from an intraruminal controlled release capsule and the in vitro digestibility of hand-plucked herbage samples, were curvilinearly related to sward height (r = 0·76, p <0·0·01). Average liveweight gains were 0·02, 0·61 and 1·31 kg d^-1 ( P <0·05) and increased linearly ( r = 0·84, P <0·001) with sward height. The maintenance organic matter intakes of the steers and bulls, with initial mean (± s.e.) live weights of 225 ± 15 kg and 172 ± 15 kg respectively, were estimated to be 3·6 and 3·5 kg d^-1 respectively. In Experiment 2 (spring) 36 cattle, including 35 of those used in Experiment 1, were reallocated to sward heights of 5, 10 and 15 cm using the same design as for Experiment 1. Average liveweight gains were 0·94, 1·57 and 1·68kg d^-1 ( p 0·05) and were curvilinearly related to sward height ( r = 0·093, p <0·05). Maintenance intakes could not be reliably extimated for the cattle in Experiment 2 because few animals had liveweight gains close to zero. These trials confirm that liveweight gain in continuously grazed finishing steers and bulls increases with sward surface height to maximum of 8–10cm with spring ryegrass/white clover pastures while, in autumn, swards of 12–15cm height are required to achieve maximum performance.     

The effect of daily herbage allowance and sward characteristics upon the ingestive behaviour and herbage intake of calves under strip-grazing management

Measurements of herbage intake and ingestive behaviour were made on British Friesian calves 4–9 months old, which were strip-grazed on swards of S24 perennial ryegrass at three (Experiment A) or four (Experiment B) levels of daily herbage allowance in three (A) or four (B) 12-d periods. Herbage intake declined by approx. 18% as daily herbage allowance was reduced from 90 to 30 g DM per kg LW in both experiments, but the relationship between intake and allowance was not consistent between periods. Bite size and rate of biting were greater in calves on low than on high allowances after entry to a new strip of herbage but the positions were reversed towards the end of grazing. Reduced herbage intakes at low allowance resulted from reductions of approx. equal magnitude in bite size, rate of biting and grazing time, though not all of these effects were significant. It is suggested that these responses result from the increasing difficulty of prehending and ingesting herbage as swards are grazed down. The calves at low herbage allowances did not increase grazing time, probably because their behaviour was conditioned by anticipation of a new allowance of herbage. Bite size and daily herbage intake were greater on a spring sward than on an autumn sward, but within experiments herbage intake was not consistently related to any of the sward characteristics measured.     

Effect of stocking rate in early season on dairy cow performance and sward characteristics

A comparison was made of stocking rates of 4·7, 5·6 and 6·4 cows ha^-1 during the first 7 weeks (period 1) of the grazing season. Each group of British Friesian cows was continuously stocked on a day and a night field. In the subsequent periods 2 and 3 (each lasting 7 weeks) the three groups were maintained at the same stocking rate within periods (4·2 and 31 cows ha^-1, respectively). The differential stocking rates were achieved by the addition and removal of cows.
The stocking rates applied in period I had no significant effects on milk yield, milk composition, liveweight change or condition score, in any period. Milk production ha^-1 over the three periods totalled 12390,13 978 and 14986 kg, and the estimated utilized metabolizable energy totalled 773, 81·5 and 86·6 GJ ha^-1 for low, medium and high stocking rates, respectively.
Increased stocking rate in period I was associated with a decrease in sward height in periods 1 and 2. This led to an increase in herbage metabolizable energy, and crude protein contents, and to an increase in tiller population density. The lowest stocking rate gave greater live individual tiller weights throughout the experiment and a longer interval between defoliation of individual tillers in period 1.
The results indicate that high stocking rates in the spring are not necessarily detrimental to overall summer performance of spring calving dairy cows. However, high stocking rates in the early season ensure a high level of herbage utilization and milk output ha^-1 in that period. Although this practice leads to a reduced sward height in mid season, the sward has less rejected area, a higher tiller population density and a higher digestibility than swards stocked at a lower level.     

Some effects of herbage composition, as influenced by previous grazing management, on milk production by cows grazing on ryegrass/white clover pastures. 1. Milk production in early spring: effects of different regrowth intervals during the preceding winter period

Two experiments (1a and 1b) were carried out to examine the effects of differences in pre-grazing herbage mass and composition on milk production by cows grazing in early spring. Swards with high (5 · 1t DM ha⁻¹) or low (2 · 9 t DM ha-1) pre-grazing masses in early spring were created by either long or short periods of regrowth during the preceding winter.
The low-mass swards contained lower concentrations of grass stem and senescent material, but higher concentrations of clover, than the high-mass swards. Herbage from the low-mass swards was also more digestible.
Cows were offered common daily herbage allowances from both swards (26 and 22 kg DM cow⁻¹ in Experiments la and lb respectively). The cows grazing on the low-mass swards produced significantly greater yields of milk, milk fat and milk protein.
The results show that herbage from the lowmass swards was of higher feeding value for lactating cows in early lactation. The practical implications for milk production per cow and per hectare are discussed.     

Supplementary feeding of forage to grazing dairy cows, 3. The effect of three daytime stocking rates on the performance of cows offered grass silage overnight

Over a 24-week period, three groups of dairy cows were continuously stocked at 8, 10 or 12 cows ha^-1 between morning and afternoon milkings, and overnight were housed and offered grass silage ad libitum. Due to a prolonged drought, sward heights only averaged 4·1 cm.
The increase in daytime stocking rate led to a decline in herbage intake, and increases in silage intake. At the highest stocking rate (12 cows ha^-1), the silage intake failed to compensate for the reduced herbage intake. Consequently the total dry matter and estimated metabolizable energy intakes were lower than for the 8 and 10 cows ha^-1 treatments. Milk yields and milk composition were not significantly affected by treatment but the 12 cows ha^-1 stocking rate gave the lowest milk and milk solids yields.
The utilized metabolizable energy (UME) on the grazed swards was greatest for the 10 cows ha^-1 treatment. The sward cut to provide the silage had a UME level (GJ ha^-1) 32% greater on average than the grazed swards during the same growth period. The total areas utilized for grazing and silage production for 8, 10 and 12 cows ha^-1 were 0·240, 0·224 and 0·215 ha respectively. Fat and protein yields per unit area were greatest for the 10 cows ha^-1 group.     

Effect of long-term changes in relative resource availability on dietary preference of grazing sheep for perennial ryegrass and white clover

Three replicate paddocks, each of 0·235 ha, containing adjacent monocultures of perennial ryegrass or white clover [50:50 by ground area, 6 cm sward surface height (SSH) at start of experiment] were continuously stocked with three yearling and four mature non-lactating, non-pregnant Scottish halfbred ewes for 12 weeks. Herbage intake, grazing behaviour and dietary selection were measured on seven occasions. Clover SSH declined rapidly over the first 5 weeks then stabilized at 1·2–1·6 cm, whereas perennial ryegrass SSH rose slightly initially, then declined gradually. Animals initially included proportionately c . 0·6 white clover in their diet but, by the end of the experiment, this had fallen to 0·3. Total daily herbage intake declined over the 12 weeks from 1·8 kg dry matter (DM) day^–1 at the start to 1·0 kg DM day^–1. Total grazing time increased from 561 min day^–1 to 649 min day^–1 at the end of the experiment. The results suggest that, despite overall herbage depletion and a greater depletion of white clover than perennial ryegrass as a result of the initial partial preference for white clover, the animals traded-off a reduced total intake and an increased grazing time in an attempt to maintain their initial preferred dietary composition.     

Influence of defoliation regime on herbage production and characteristics of intake by dairy cows as affected by grazing intensity

Three contrasting defoliation regimes for dairy cows—four cuts annually, severe rotational grazing and lax rotational grazing integrated with cutting—were compared in terms of herbage production, selection and intake per cow. Lax and severe grazing were compared simultaneously and grazing intensity was characterized by means of changes in herbage mass and sward height during grazing.
Herbage growth and yield were similar under cutting, severe grazing and lax grazing/cutting (120 t organic matter (OM) ha⁻¹). Herbage quality and leaf production were highest with severe grazing, which also had a less marked seasonal pattern of growth. The herbage intake per cow was 111 kg OM d⁻¹ with severe grazing and proportionately (0-20) higher at lax grazing/ cutting. 050 of the herbage yield was harvested by cutting at lax grazing/cutting. Selectivity was described with high certainly by the nutrient content prior to defoliation and by the degree of defoliation. Models to quantify this are presented.
Grazing intensity could be described by the size and degree of utilization of the fouled area, and herbage intake was quantified by means of herbage height before and after grazing. Within the range of 80-240 mm sward height prior to grazing, height measurements led to realistic and more accurate estimates than those obtained by measuring organic matter disappearance.
Herbage utilization was depressed significantly by increasing maturity of herbage due to lower nutritive value, but in particular due to reduced green leaf content and increased reproductive development. If sward height did not exceed 250 mm at any time, good utilization by grazing could be obtained.     

The voluntary intake and in vivo digestibility of herbage harvested from indigenous hill plant communities

Voluntary intake and in vivo digestibility of herbage harvested from five indigenous communities– Agrostis-Festuca, Nardus and Molinia grasslands and Eriophorum vaginatum- and Trichophorum caespitosum -dominated varieties of blanket bog–and also from sown Lolium perenne and Trifolium repens swards were measured over two years. First growths of each sward were harvested at three stages of maturity and stored at — 20°C before feeding. Voluntary intake was measured while feeding ad libitum to 15% excess of the intake on the previous day and digestibility when feeding at 80% of voluntary intake.
There was a common positive relationship (r²= 0·86***) between intake (adjusted for year of feeding, range 72·8–16·7 g organic matter (kg LW)^0·75 d^-1) and organic matter digestibility (range 0·796–0·371), covering Lolium perenne and most of the indigenous communities. However, there were significant differences between the regressions of intake on the concentration of neutral detergent fibre for ryegrass and the indigenous communities, and also between the regressions for individual communities.
The results demonstrated the general value of organic matter digestibility as a predictor of intake potential, and the high digestibility and intake potential of immature vegetation from the grass and grass heath communities.     

Effect of herbage allowance on the efficiency of defoliation by the grazing animal

An experiment examining the relationship of daily herbage disappearance (DHD) and daily herbage allowance (DHA) is described. Cows with calves were grazed at three stocking rates on Kleingrass and Coastal Bermudagrass pastures. DHD and DHA were monitored at 14-d intervals. A significant positive linear relationship was noted between DHD and DHA ( P 0·25). Equations derived for Coastal Bermudagrass and Kleingrass were not significantly different and resulted in a combined equation Ŷ= 0·275X + 0·209 with an r² vaiue of 0·27. As DHA exceeded 6–9 kg DM per 100 kg live weight, efficiency of defoliation by the cows and calves declined.