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1.
Two systems of grazing management involving preferential treatment of high- yielding dairy cows were compared with a grazing system in which both high- and low-yielders received uniform treatment. Cows were rotationally grazed across I-day paddocks without concentrate supplementation from 23 April to 8 October 1985, with a mean stocking rate over the season of 5-4 cows ha?1. Preferential treatment of high-yielding cows was achieved either by using a leader/follower approach (LF) with high-yielding cows in the leader group, or by preferential forage feeding (PFF) where high-yielding cows were allowed access to grass silage for 1 -5 h daily and grazed alongside low-yielders. Control (C) cows grazed together as a single group. The high grazing stocking rates used on all three treatments resulted in good grass utilization with residual sward heights, assessed by a rising-plate sward stick, of 45, 50 and 48 mm for the LF, PFF and C treatments respectively. Animal performance data for the LF, PFF and C treatments respectively were: milk yield (kg d?1) 15middot;1, 15middot;6 and 14middot;7 (s.e. 0middot;78); milk fat yield (g d?1) 598, 606 and 567 (s.e. 34); milk protein yield (g d?1) 500, 519 and 480 (s.e. 31); and live weight gain (kg d?1) 0middot;12, 0middot;23 and 0middot;25 (s.e. 0·05). These results indicate that leader/follower grazing had little overall effect on animal performance when high grazing severity was imposed, with the improvement in animal performance of high-yielding cows in the leader group being offset by the reduced performance of the follower group. Buffer-feeding of high-yielding, rotationally-grazed cows with high-quality grass silage had little effect on animal performance and resulted in a decrease in the efficiency of grassland utilization. Silage appeared to substitute for herbage, with a reduction in herbage DM intake of 0middot;55 kg per kg silage DM consumed.  相似文献   

2.
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.  相似文献   

3.
An experiment was carried out during 1984 to examine the effects of three alternative grazing strategies for January/February calved British Friesian dairy eows on sward and animal production. Cows were rotationally grazed across 1 d paddocks without concentrate supplementation from 30 April to 1 October. A flexible grazing (EG) treatment involved manipulating residual herbage height, as assessed by a rising-plate sward stick, with cows initially grazing to 80 mm, reducing to 60 mm when milk yield declined below 20 kg d?1 and finally to 50 mm when milk yield declined below 15 kgd?1. Control (C) cows grazed to a constant residual herbage height of 60 mm throughout the season (a 60-inm rising-plate sward stick height is equivalent to a sward surface height of approximately 80 mm). On a further treatment a leader/follower (LF) approach was used, with cows paired for calving date and parity and within pairs allocated to either a high-(leader) or a low-yielding (follower) group, according to milk yield at turnout, with the leader group grazing 1 d ahead of the follower group. Overall stocking rates on C and LE treatments were identical but herbage allowances differed as a result of treatment effects. Animal performance data for the FG, C and LE treatments, respectively, were: milk yield (kg d?1) 14·5, 14·7 and 16·0 (s.e. 0·59); milk fat yield (g d?1) 577, 571 and 637 (s.e. 29); milk protein yield (g d?1) 528, 527 and 576 (s.e. 19); and liveweight gain (kg d?1) 0·09, 0·20 and 0·14 (s.e. 0·04). Overall, there was no benefit in animal production following lax grazing in spring even with high-yielding cows, and this approach resulted in the accumulation of stem and senescent material in the sward in mid-season. However, preferential treatment of high-yielding cows by grazing as a leader group in a leader-follower system resulted in higher milk production, particularly in late season, with an overall improvement in milk yield for the LF treatment of 9% relative to treatment C.  相似文献   

4.
An experiment was undertaken to examine the effect of supplement type on herbage intake, total dry matter (DM) intake, animal performance and nitrogen utilization with grazing dairy cows. Twenty‐four spring‐calving dairy cows were allocated to one of six treatments in a partially balanced changeover design with five periods of four weeks. The six treatments were no supplement (NONE), or supplementation with either grass silage (GS), whole‐crop wheat silage (WS), maize silage (MS), rapidly degradable concentrate (RC) or slowly degradable concentrate (SC). Cows were rotationally grazed with a mean herbage allowance of 20·5 kg DM per cow per day, measured above 4 cm. Forage supplements were offered for approximately 2 h immediately after each morning milking, with cows on NONE, RC and SC treatments returning to the grazing paddock immediately after milking. Cows on treatment MS had a significantly higher supplement DM intake than the other treatments but a significantly lower grass DM intake than the other treatments, resulting in no significant difference in total DM intake when compared with cows on treatments WS, RC and SC. Concentrate type had no significant effect on herbage intake, milk yield, milk composition or yield of milk components. The yield of milk fat and milk protein was significantly higher on treatments MS, RC and SC compared with treatments NONE, GS and WS. The results indicate that despite a relatively high substitution rate, maize silage can be a useful supplement for the grazing dairy cow.  相似文献   

5.
This experiment examined the effects of grazing severity and degree of silage restriction during early turnout of dairy cows to pasture in spring on animal performance. Forty late‐winter‐calving Holstein Friesian dairy cows were allocated to one of five treatments between 7 March and 17 April 1997. The treatments involved early turnout of cows to grass for 2 h per day at two residual sward heights and two silage allowances, plus a control treatment, in a randomized block design. Dairy cows on the control treatment remained indoors throughout the experiment and were offered grass silage ad libitum. Dairy cows on all treatments were also offered 6 kg d–1 of a concentrate on a flat‐rate basis, split equally between the morning and afternoon milkings. Offering cows access to pasture in early spring for 2 h per day resulted in increases in both milk (P < 0·001) and protein yield (P < 0·01). On average, over all grazing treatments, cows produced an additional 2·6 kg milk per day compared with the control treatment (28·5 vs. 25·9 kg d–1, s.e.m. 0·43). Furthermore, these increases in milk yield were obtained even when silage was restricted indoors (28·4 vs. 25·9 kg d–1) and cows grazed down to a residual sward height of 40 mm (28·1 vs. 25·9 kg d–1). Protein yield was higher (P < 0·01) with dairy cows grazing pasture compared with cows indoors (848 vs. 707 g d–1, s.e.m. 28·9). Silage intake was significantly (P < 0·001) reduced when cows were turned out to pasture. In conclusion, early turnout of dairy cows to pasture in spring for 2 h per day reduced silage intake and increased milk yield and protein yield relative to those fully housed and offered grass silage with a low level of concentrates.  相似文献   

6.
Matching grass supply to grazing patterns for dairy cows   总被引：2，自引：0，他引：2  
Four groups of five spring-calving Holstein–Friesian cows were given a daily grass allowance in a strip-grazing system after either morning (AM; two groups) or afternoon (PM; two groups) milking over a 10-week period. The dry-matter (DM) concentration of the grass tended to be higher after afternoon milking [AM, 178 vs. PM, 197 g DM (s.e.d. 5·32) kg–1 fresh matter], and water-soluble carbohydrate concentrations were significantly higher [AM, 175 vs. PM, 204 g kg–1 DM (s.e.d. 6·67)]. Although the total times spent grazing (AM, 461 vs. PM, 462 min day–1) were similar for both groups, cows receiving their allocation in the afternoon had a longer evening meal (>4 h duration) compared with those receiving their allocation in the morning (2–3 h), which also spent more time ruminating [AM, 454 vs. PM, 433 min day–1 (s.e.d. 1·80)]. This short-term study demonstrated how a relatively simple change in management practice in strip-grazing systems could benefit milk yield and pasture utilization. This is because the DM and water-soluble carbohydrate contents of the herbage are higher in the evening than in the morning, and this is when grazing animals concentrate much of their daily grazing activity.  相似文献   

7.
An investigation into the effect of including dried grass in the supplement given to dairy cows at pasture is reported. Supplements containing 0, 50 and 100% dried grass were used in the investigation which was carried out in two parts. In the first part 12 high-yielding cows with unrestricted access to pasture were used in an experiment with a change over design to assess the effects of feeding 5 kg/day of each supplement on milk yield and composition. In the second part 8 steers, housed in stalls and given cut herbage from the same sward as that grazed hy the cows, were used in a change over experiment to assess the effects of the three supplements on herhage and total DM intake. No significant differences in milk yield between supplements were ohtained, the mean yields being 23·9, 24·5 and 23·9 kg/day for the supplements containing 0, 50 and 100% dried grass, respectively. Milk composition was also not significantly affected by including dried grass in the supplement. In the indoor feeding trial using the steers, the addition of 3·5 kg DM from the supplement resulted in an increase in total DM intake of only 1·3 kg/day. There was no significant difference hetween supplements on herbage and total DM intake.  相似文献   

8.
A straw/concentrate mixture was offered to set-stocked dairy cows over a 24-week period. The cows were offered grazed herbage only (G), or grazed herbage with a straw/concentrate supplement offered either for 45 min after each milking (B), or overnight (P). The overnight treatment involved housing the cows between afternoon and morning milking. The straw/concentrate mixture contained 0·33 long barley straw, 0·28 barley, 0·12 soya bean meal, 0·25 molaferm and 0·02 minerals. During the first 8 weeks of the experiment an average of 2·25 kg of concentrate were fed, and from weeks 9–24, 2·0 kg of concentrate were fed.
The feeding of the straw/concentrate mixture led to a decrease in estimated herbage dry matter (DM) intake, particularly for treatment P. Estimated total DM intakes were increased throughout the experiment by offering the straw/concentrate mixture. However, total metabolizable energy (ME) intakes were only increased in mid-and late season.
Milk yield was higher in early season for treatment G; 28·1 kg d−1 compared to 26·8 kg d−1 and 25·5 kg d−1 for treatments B and P respectively. In late season the cows in treatment G had lower milk yields; 13·3 kg d−1 compared to 15·5 kg d−1 and 16·8 kg d−1 for treatments B and P respectively. Milk fat content was increased in early season in treatment P, and milk protein content tended to be reduced throughout the experiment for cows offered the straw/concentrate mixture overnight. Over the whole experiment there were no differences in yield of milk solids.  相似文献   

9.
In the UK, dairy cows are increasingly housed at night throughout the grazing season. However, there is limited information on cow performance and the impact on labour requirements when a forage supplement is offered during housing at night throughout the entire grazing season. The effects of housing at night were studied in two experiments, in which two treatments were compared. On treatment part‐grazing (PG), dairy cows were given access to grazing by day and were offered grass silage while housed at night, and, on treatment continuous grazing (CG), dairy cows were given access to grazing both by day and by night. Experiments 1 (138‐d duration) and 2 (127‐d duration) involved sixty (primiparous) and seventy‐six (primiparous and multiparous) Holstein‐Friesian dairy cows respectively. Concentrates were offered during milking at 4·0 and 3·0 kg per cow per day in Experiments 1 and 2 respectively. In Experiment 1, total milk output was significantly higher with treatment PG than treatment CG (P < 0·01) while the reverse occurred in Experiment 2 (P < 0·001). Milk protein concentration was significantly higher with treatment CG in Experiments 1 and 2 (P < 0·001). Cows on treatment CG in Experiment 2 had significantly higher body condition scores and live weights at the end of experiment than those on treatment PG (P < 0·05). Weekly labour requirements were calculated to be proportionally 0·04 lower on treatment PG than on treatment CG. When offered silage during housing at night, the response of grazing dairy cows was largely determined by the grazing conditions encountered and the quality of the forage offered.  相似文献   

10.
To allow improved prediction of daily herbage intake of dairy cows in rotational grazing systems, intake behaviour was assessed throughout the day in 24‐h paddocks. Herbage intake in 16 lactating Holstein–Friesian cows was assessed using the short‐term (1‐h) weight gain method at four predetermined natural meal times throughout the day (early morning, T1; late morning, T2; mid‐afternoon, T3; and early evening, T4). The study comprised two 4‐day experiments, each with a cross‐over design of four blocks. In both experiments, cows grazed a 24‐h paddock daily, and the effect of the immediately previous grazing experience on intake behaviour was investigated throughout the day, taking account of daily fluctuations in the short‐term physiological condition of the cows. Experiment 1 was carried out to investigate overall grazing behaviour during meals as a sward is progressively depleted during the day, with intake being assessed within the paddock and, hence, on a depleted sward. Experiment 2 similarly investigated the effect of sward depletion and physiological condition throughout the day on intake, but cows were removed to fresh, undefoliated swards during intake measurement periods; thus, intake rate was not influenced by differences in sward condition. Intake behaviour from both experiments was compared to establish the effect on herbage intake of changes in sward state and non‐sward factors. In Experiment 1, sward surface height, available herbage mass, proportion of leaf and green leaf mass declined as the day progressed. Bite mass declined with sward depletion, and mean intake rate was 1·64 kg dry matter (DM) h–1, which was significantly lower at T3 (P < 0·01) than during other meals. In Experiment 2, plot sward conditions did not change throughout the day, and intake behaviour also remained constant, with a mean intake rate of 2·11 kg DM h–1. Mean bite depth as a proportion of pregrazing extended tiller height was constant throughout the day (mean 0·32). The results show that, although cows grazed throughout the day on progressively depleted swards, indicative of rotationally grazed paddocks (Experiment 1), bite mass declined linearly and intake behaviour was variable. However, where intake was assessed on high‐quality, undefoliated swards (Experiment 2), intake behaviour was similar regardless of the time of day and the immediately previous experience. There was some indication of an interaction between the effects of the sward and the physiological condition of the animal on herbage intake.  相似文献   

11.
The objective of this study was to investigate the effects of an early (February; F) or delayed (April; A) primary spring grazing date and two stocking rates, high (H) and medium (M), on the grazing management, dry matter (DM) intake of grass herbage and milk production of spring‐calving dairy cows grazing a perennial ryegrass sward in the subsequent summer. Sixty‐four Holstein‐Friesian dairy cows (mean of 58 d in milk) were assigned to one of four grazing treatments (n = 16) which were imposed from 12 April to 3 July 2004. Cows on the early spring‐grazing treatment were grazed at 5·5 cows ha?1 (treatment FH) and 4·5 cows ha?1 (treatment FM) while cows on the late‐grazing treatment were grazed at 6·4 cows ha?1 (treatment AH) and 5·5 cows ha?1 (treatment AM). The organic matter digestibility and crude protein concentration of the grass herbage were higher on the early‐grazing treatment than on the late‐grazing treatment. The cows on the FM treatment had significantly (P < 0·001) higher milk (24·5 kg), solids‐corrected milk (22·5 kg), fat (P < 0·01, 918 g) and protein (831 g) yields than the other three treatments. Cows on the FM treatment had a higher (P < 0·001) DM intake of grass herbage by 2·3 kg DM per cow per day than cows on the AH treatment, which had a DM intake significantly lower than all other treatments (15·2 kg DM per cow per day). The results of the present study showed that grazing in early spring has a positive effect on herbage quality in subsequent grazing rotations. The study also concluded that early spring‐grazed swards stocked at a medium stocking rate (4·5 cows ha?1; FM) resulted in the highest DM intake of grass herbage and milk production.  相似文献   

12.
Over a 24-week period during the 1986 summer, three groups of January- to March-calving dairy cows were either grazed conventionally (G) or grazed between morning and afternoon milkings and housed overnight and offered grass silage (Si) or a straw/concentrate mixture (St) ad libitum. The straw/concentrate mixture contained proportionately, 0-33 long barley straw, 0·28 ground barley, 0·12 soya bean meal, 0·25 molaferm and 0·22 minerals. The metabolizable energy (ME) and crude protein (CP) contents of the silage fed in weeks 1-8 and weeks 9-24 were 9-5 and 10−6 MJ kg MD−1 and 160 and 191 g kg DM−1 respectively. The straw mix had an ME content of 10−1 MJ kg DM−1 and CP content of 134 g kg DM−1. Partial storage feeding with silage or a straw/concentrate mixture led to a decrease in estimated herbage DM intake. The feeding of the straw/concentrate mixture increased total DM intake, but the estimated total ME intake was similar for treatments G and St. The intakes (kg DM d−1) for treatments G, Si and St were respectively, herbage 11·7,6·8,4·1; total l3·5,13·6,15·0; total ME intake (MJd−1) 163, 155, 163.
Animal performance was, for treatments G, Si and St respectively: milk yield (kg d−1) 19·2, 17·5, 19·1 (s.e.d. 0-87); milk fat content (g kg−1) 36·9, 37·6, 37.1 (s.e.d. 1.22); milk protein content (g kg−1) 35·3, 32·9, 33·4 (s.e.d. 0·76).  相似文献   

13.
In a 16-week grazing experiment with six spring-calved Ayrshire cows, drinking water was available to the animals in three different ways, and the effect on milk prodnction was studied. The water was available from a water howl in the cowshed for 2.8 h/day in Treatment A, from a trough in the field for 21.2h/day in Treatment B, and from hoth sources for a total of 24 h/day in Treatment C. The cows on all treatments were grazed in individual plots of intensively-managed perennial ryegrass, stocked at the rate of 1 cow/0.22 ha (0.54 ac). The mean daily intakes of drinking water were 10.1, 15.3 and 15.5 kg (2.23, 3.37 and 3.42 gal)/cow, and the mean daily milk yields were 17.0, 17.2 and 16.8 kg (37.5, 37.9 and 37.0 lb)/cow in Treatments A, B and C, respectively; milk yields were not significantly different The herbage had an average DM content of 17.3%, and contained 19.6% crude protein and 66.5% digestible organic matter in the DM. The weight of water drunk was significantly and positively related to the DM percentage of the herbage, the air temperature and the daily hours of sunshine, and negatively related to daily rainfall. It is concluded that when dairy cows are grazing leafy herbage of high digestibility as their sole feed, the time during which drinking water is available may safely be restricted.  相似文献   

14.
The herbage intake and grazing behaviour of 4 dry cows on autumn grass receiving 2, 4, 6 or 8 kg concentrates/day, was assessed in a 4×4 Latin Square experiment. Total OM intake increased from 11±5 kg/day with 2 kg concentrates to 13±6 kg/day with 8 kg concentrates. The average supplementary effect was 0±46 kg increase in OM intake/kg OM fed as concentrates. Minutes per day spent grazing decreased from 495 with 2 kg concentrates to 359 with 8 kg. The mean decline was 22 min./kg concentrates or 28 min./kg OM in concentrates eaten. Herbage was eaten at an average rate of 47 min./kg OM.  相似文献   

15.
The effect of offering a total mixed ration of silage and concentrate (proportionately 0·44 silage) system [indoor feeding system (IF)] was compared with grazing at a high daily herbage allowance with a low level of concentrate supplementation [early grazing system (EG)] in early spring on the performance of spring‐calving dairy cows in Ireland. Sixty‐four spring‐calving Holstein–Friesian dairy cows (mean calving date, 2 February) were allocated to one of two systems between 16 February and 4 April 2004. An equal number of primiparous and multiparous cows were assigned to each system. The dairy cows on the IF system were housed for a 7‐week period and offered a diet of 10·9 kg DM cow?1 d?1 (s.d. 2·3) of concentrate, the remainder of the diet was 8·6 kg DM cow?1 d?1 (s.d. 1·9) of grass silage. The dairy cows on the EG system were offered a mean daily herbage allowance of 15·1 kg DM cow?1 d?1 (s.d. 3·7) and were supplemented with 3·0 kg DM cow?1 d?1 (s.d. 1·0) of concentrate. There was no difference in milk yield between the two systems but the cows in the EG system had a higher milk protein concentration (2·9 g kg?1) and a higher milk protein yield than in the IF system. Milk fat concentration was higher for cows in the IF than EG system (3·0 g kg?1). There was no difference in total daily dry‐matter intake between the systems, measured in week 6 of the study. Mean live weight of the cows in the IF system was greater than in the EG system. The results of the study suggest that a slightly greater performance can be achieved by a system offering a high daily herbage allowance to spring‐calving dairy cows in early lactation compared with a system offering a total mixed ration containing a high proportion of concentrate with grass silage.  相似文献   

16.
In a trial lasting 3 years at Jealott's Hill and 2 years at Ravenscroft Hall, a total of 73 January- March-calving Friesian x Holstein cows and heifers were given a diet consisting almost exclusively of ensiled and grazed ryegrass for an entire lactation to establish the level of milk production which grass alone can support. From calving to turnout in April/May (average duration 87 days), the animals were given high digestibility (DOMD = 678g kg-1 DM) ryegrass silage ad libitum. After turnout, they grazed ryegrass swards until housing in autumn. Thereafter, the cattle were given ryegrass silage of lower digestibility (DOMD = 600–620 g kg-1 DM) for the remainder of the lactation and during the dry period.
Mean silage dry matter intakes from calving to turnout were 13–2 kg day-1 at Jealott's Hill and 11·5 kg day-1 at Ravenscroft Hall. Average milk yields were 21-1 kg day-1 for cows and 16-1 kg day-1 for heifers with 39-2g fat kg-1, 29-6g protein kg-1 and 47–9 g lactose kg-1. Over the complete lactation, average milk yields were 4680 kg and 4006 kg for the cows and heifers, respectively, with 39-4 g fat kg-1, 31·4 g protein kg-1 and 46·9 g lactose kg-1. Animal health and fertility were satisfactory. The results demonstrated the value of high quality grazed and ensiled ryegrass and provided a measure of milk production from grass only.  相似文献   

17.
The milk-production potential of different sward types was measured in each of the four seasons of the year in a replicated experiment in south-west Victoria, Australia. Dairy cows were offered ad libitum allowances of a 'short-term winter' sward, based on Italian ryegrass (treatment STW), a 'long-term winter' sward, based on a winter-active tall fescue (treatment LTW), a 'long-term summer' sward, based on a summer-active tall fescue (treatment LTS) and a Control sward (perennial ryegrass) in four seasons (days in milk in parentheses): spring (November dairy cows, 124), summer (February, 227), autumn (May, 234) and winter (August, sixty-four). A 'short-term summer' sward, based on chicory and white clover (treatment STS), was also included in summer. There was a significant season × treatment interaction caused by a more gradual decline in milk yield from peak for cows grazing treatment LTS compared to the Control treatment in the transition period from spring to summer. In summer, cows grazing treatment STS produced more milk (1·41 kg fat plus protein per cow d−1) than cows grazing all other treatments (0·92 kg per cow d−1) because of the superior nutritive value of herbage of pre-grazing pasture and higher apparent dry-matter intakes. Swards based on alternative species to perennial ryegrass are capable of supporting milk production that is at least comparable over an annual cycle.  相似文献   

18.
The objective of this study was to compare the grazing efficiency of 30 perennial ryegrass varieties, differing in ploidy and heading date. Plots were grazed by lactating dairy cows and managed under a rotational grazing system with 19 grazing events occurring over two years. Pre-grazing and post-grazing compressed sward heights were measured with a rising plate meter. A mixed model was used to predict the post-grazing sward height of each variety based on year, grazing event, block and pre-grazing sward height. Residual grazed height (RGH) was derived as the difference between the actual and predicted post-grazing sward height and was used as the measure of grazing efficiency. Negative RGH values indicated that the actual herbage removed was greater than that predicted and so indicated a superior grazing efficiency. Varieties differed in their level of grazing efficiency (p < .001), with RGH values ranging from −0.38 to +0.34 cm. Tetraploid varieties exhibited significantly greater grazing efficiency performance than diploids (p < .001), with average RGH values of −0.13 and +0.13 cm respectively. A significant difference in grazing efficiency was found among recommended perennial ryegrass varieties that are not being recorded by mechanically harvested simulated grazing protocols. A variety reappraisal that included grazing efficiency could identify varieties capable of improving on-farm livestock productivity from grass.  相似文献   

19.
For three 8-week periods of the grazing season 48 spring-calving cows were continuously stocked at either a high or a low rate (average 4.9 and 4.3 cows ha−1 respectively) which declined through the season. Within each stocking rate group half the cows were allowed access to hay for 45 min after morning milking; the other half received no hay.
Total dry matter (DM) intakes were increased by offering hay, and intakes of hay were greater at the high stocking rate and during prolonged periods of inclement weather. However, there were times when, because of low herbage height and adverse weather, offering hay once daily could not prevent a decline in total DM intake. Grazing time was reduced and ruminating time increased by offering hay, but the rate of biting at pasture was unaffected. Hay DM was eaten at twice the rate of intake of herbage DM.
Offering hay increased milk yield in early season and liveweight gain in late season. The benefits of offering hay were greatest for the higher yielding cows. There were no significant effects on milk composition.
Stocking rate had only small effects on herbage height, but stocking at the higher rate tended to reduce herbage DM intake and reduced live-weight gain in late season. Levels of utilized metabolizable energy from grazed herbage were high (average 106 GJ ha−1) but were reduced by feeding hay and stocking at the lower rate.  相似文献   

20.
The study evaluated the impact of High, Moderate and Low grazing intensities throughout the grazing season, within a rotational stocking system, on the performance of high‐yielding dairy cows receiving a high level of concentrates. Sixty‐three Holstein‐Friesian dairy cows, 21 at each grazing intensity, were rotationally grazed. Average paddock size, post‐grazing sward heights and seasonal grazing stocking rates within the High, Moderate and Low grazing intensities were 0.143, 0.167 and 0.200 hectares, 5.2, 6.1 and 6.8 cm and 7.8, 6.7 and 5.6 cows ha?1 respectively. Grazing intensity had no effect on milk fat and protein content, end‐of‐study body condition score or end‐of‐study live weight although the latter tended towards significance (p = .057). Average daily milk yield per cow was higher within the Low grazing intensity (33.2 kg day?1) than High grazing intensity (30.5 kg day?1), and average daily fat‐plus‐protein yield was higher for Low and Moderate than High. Milk output per hectare was higher for the High grazing intensity than Low grazing intensity (33,544 and 26,215 kg ha?1 respectively). Grazing intensity had no effect on grazing bite number, blood metabolites or concentrations of milk fatty acids or on sward morphological components, although dead matter increased with time across all grazing intensities. Herbage utilization efficiency (above 1,600 kg DM ha?1) was 52%, 74% and 87% for Low, Moderate and High respectively. It is concluded that high‐producing dairy cows can graze at high levels of utilization when they are receiving high rates of concentrates. Although cow performance will be reduced, milk yield per ha will increase.  相似文献   

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