Effects of feeding additional pasture hay in autumn to dairy cows grazing irrigated perennial ryegrass-white clover pasture and supplemented with barley grain

2000 ◽  
Vol 40 (1) ◽  
pp. 1 ◽  
Author(s):  
W. J. Wales ◽  
D. W. Dellow ◽  
P. T. Doyle ◽  
A. R. Egan
Keyword(s):  
Perennial Ryegrass ◽  
White Clover ◽  
Milk Fat ◽  
Crude Protein ◽  
Barley Grain ◽  
Fibre Content ◽  
Neutral Detergent Fibre ◽  
Herbage Intake ◽  
Clover Pasture

Two experiments were undertaken to investigate responses by dairy cows grazing irrigated perennial pastures in autumn to supplementation with barley grain and pasture hay. Cows in late lactation were offered limited amounts of perennial ryegrass–white clover pasture at 26 kg DM/cow. day. Supplements were offered as nil or 6.0 kg DM/cow.day plus perennial pasture hay at 0, 0.5, 1.2, 2.0 or 3.0 kg DM/cow. day in a replicated experiment with 6 treatments using 36 cows (3 cows/treatment replication). The second experiment, which was conducted concurrently with experiment 1, measured aspects of rumen function and blood parameters in 3 groups of 3 rumen fistulated lactating cows grazing at the same herbage allowance and supplemented with barley (6.0 kg DM/cow. day) and 0, 1.0 or 3.0 kg DM of pasture hay daily. The in vitro DM digestibility and crude protein and neutral detergent fibre content of the barley and perennial pasture hay was 863 and 640 g/kg DM, 134 and 87 g/kg DM and 192 and 615 g/kg DM, respectively. In experiment 1, the cows from all treatments consumed herbage (mean s.d.) with an in vitro DM digestibility of 811 21.8 g/kg DM, crude protein content of 233 26.0 g/kg DM and neutral detergent fibre content of 404 39.4 g/kg DM compared with the pregrazed herbage on offer of 710, 152 and 526 g/kg DM, respectively. The mean pregrazing herbage mass of 3.75 t DM/ha in experiment 1 consisted of perennial ryegrass (580 g/kg DM), white clover (100 g/kg DM), weeds (110 g/kg DM) and dead material (210 g/kg DM). Without supplements, cows consumed 10.0 kg DM/day of this pasture with a neutral detergent fibre intake of 4.43 kg/day. The herbage grazed in experiment 2 was similar. Herbage intake did not decline to a large degree when barley was included in the diet indicating a very low substitution rate under the prevailing conditions where herbage allowance was only 26 kg DM/cow. day. Inclusion of hay progressively decreased (P<0.05) herbage intake, with substitution averaging 1.2 kg DM of herbage/kg DM of hay. Total DM intakes (15.5 kg DM/cow. day) were similar for the barley and the barley plus hay treatments up to 2.0 kg DM hay/cow. day; total DM intake was higher (P<0.05) for the 3.0 kg hay treatment. Milk production increased (P<0.05) with grain and hay supplementation, the marginal response being 0.8–1.0 kg milk/kg DM supplement, however, there was no significant difference between the 5 supplemented treatments. Supplementation with hay had no significant effect (P>0.05) on milk fat or milk protein contents which averaged 44.6 and 35.2 g/kg milk, respectively. The ratio of acetate + butyrate:propionate was 4.1:1 when cows consumed 6.0 kg barley, which was around the critical ratio of 4:1 for milk fat of 40 g/kg. Increasing the amount of hay in the diet did not alter this ratio. Because of the high levels of substitution of hay for pasture, changes in neutral detergent fibre intake were small between supplemented treatments. The rumen pH, ammonia-N concentration and volatile fatty acid concentration were relatively stable during the day because of a relatively slow rate of eating (1.5 kg DM/h) and long rumination time (about 6.8 h/day). Ruminal pH was rarely below 6.0, even when barley was given alone, suggesting that fibre digestion was not compromised. Additional fibre as supplemental hay to cows in late lactation grazing irrigated pasture did not improve milk production when the neutral detergent fibre content of the diet was above an average of 336 g/kg DM. Use of hay as a means of providing additional fibre could reduce herbage utilisation.

Effect of grain supplementation and the provision of chemical or physical fibre on marginal milk production responses of cows grazing perennial ryegrass pastures

2001 ◽  
Vol 41 (4) ◽  
pp. 465 ◽  
Author(s):  
W. J. Wales ◽  
Y. J. Williams ◽  
P. T. Doyle
Keyword(s):  
Milk Production ◽  
Perennial Ryegrass ◽  
White Clover ◽  
Milk Fat ◽  
Crude Protein ◽  
Ground Level ◽  
Large Degree ◽  
Herbage Intake ◽  
Cereal Grain

An experiment was undertaken to establish the marginal milk production response from cereal grain supplementation by dairy cows grazing irrigated perennial pastures in spring and whether the addition of a hay supplement would improve that response. Cows were offered perennial ryegrass (Lolium perenne L.)–white clover (Trifolium repensL.) pasture at allowances (measured to ground level) of 20 or 40 kg dry matter (DM)/cow.day. Additional cows offered the low allowance were also offered supplements of pasture hay as a cube or pellet (2.5 kg DM/day), cereal grain as a pellet (5.0 kg DM/day) or cereal grain plus pasture hay (7.5 kg DM/day) as a pellet (1.75:1 DM basis) or cube (1.97:1 DM basis). The 7 treatments were replicated 3 times, and 63 cows were used (3 cows/treatment). The in vitro DM digestibility, crude protein and neutral detergent fibre (NDF) concentration of the barley and perennial pasture hay were 863 and 563 g/kg DM, 131 and 92 g/kg DM, and 182 and 666 g/kg DM, respectively. Cows from all treatments consumed herbage with an in vitro DM digestibility of 833 g/kg DM, crude protein content of 214 g/kg DM and NDF concentration of 457 g/kg DM compared with the pregrazed herbage on offer of 771, 174 and 527 g/kg DM, respectively. The mean pregrazing herbage mass of 4.13 t DM/ha consisted of perennial ryegrass (507 g/kg DM), white clover (188 g/kg DM), weeds (194 g/kg DM) and dead material (111 g/kg DM). Without supplements, cows consumed 11.2 kg DM/day at the low pasture allowance and 15.6 kg DM/day at the high allowance. Herbage intake did not decline to a large degree when barley was included in the diet, where a substitution rate of 0.2 kg reduction in pasture DM/kg DM cereal grain supplement was measured. The NDF concentration of the diet consumed was lowest (P< 0.05) for the grain pellet treatment (370 g NDF/kg DM) and highest (P&lt;0.05) for the fibre pellet (493 g NDF/kg DM) and the fibre cube (507 g NDF/kg DM) treatments. Fat-corrected milk yield increased (P<0.05)) from 20.1 to 24.5 kg/cow.day when cows consumed 4.5 kg DM cereal grain/day with a marginal milk response of 1.0 kg 4% fat-corrected milk/kg DM concentrate supplement. Supplementation with grain or hay had no significant effect (P>0.05) on milk fat, protein or lactose concentrations. The cows offered the high allowance spent more (P<0.05) time grazing than those offered the low allowance, but there were no significant differences in rumination time. Cows spent more time ruminating when consuming the grain &plus; fibre cube compared with the other supplement treatments, which were lower (P<0.05) and similar. Cows offered pasture at the low allowance ruminated the least. The rumen pH was not different between treatments and averaged 5.9. The ratio of acetate plus butyrate: propionate was not different between treatments and averaged 4.3. This study has shown that feeding cereal grain to cows grazing pastures high in perennial ryegrass resulted in acceptable marginal milk responses of 1 kg milk/kg DM of cereal grain in spring because of sufficient NDF in the diet. As there was adequate NDF in the diet, further supplements with pasture hay as cubes or pellets had no effect on marginal milk responses .

Effects of season and time since defoliation on the nutritive characteristics of three irrigated perennial pasture species in northern Victoria 1. Energy, protein and fibre

1999 ◽  
Vol 39 (5) ◽  
pp. 555 ◽  
Author(s):  
C. R. Stockdale
Keyword(s):  
Perennial Ryegrass ◽  
White Clover ◽  
Crude Protein ◽  
Energy Content ◽  
Energy Concentration ◽  
Neutral Detergent Fibre ◽  
Plant Parts ◽  
Metabolisable Energy ◽  
Grazing Dairy Cows

The study reported here compared the nutritive characteristics of the 3 most common irrigated perennial pasture species grown in northern Victoria as they regrew after defoliation at various times during the year. In addition, the relative influence of changes to the proportions of morphological components and the nutritive characteristics of the individual components on the quality of whole plants was examined. The nutritive characteristics of white clover (Trifolium repens cv. Haifa), ryegrass (Lolium perenne cv. Ellet) and paspalum (Paspalum dilatatum) were examined at weekly intervals on 4 occasions during spring–autumn, 1993–94. On each occasion, pastures were defoliated with a drum mower and allowed to regrow for up to 9 weeks; defoliation dates were 24 September, 26 November, 28 January and 25 March. The variation in estimated metabolisable energy [obtained from in vitro dry matter (DM) digestibility], crude protein and detergent fibre concentrations within species was significantly (P<0.01) less than between clover and the grasses. White clover was consistently high in metabolisable energy (9.3–11.2 MJ/kg DM) and crude protein (17.7–27.7% DM), and low in neutral detergent fibre (27.8–39.8% DM) in all periods. At the other extreme, paspalum had a metabolisable energy content that peaked at 9.3 MJ/kg DM, and fell as low as 7.4 MJ/kg DM. Paspalum also had low protein (7.5–14.7% DM) and very high neutral detergent fibre (61.9–69.9% DM) concentrations. Ryegrass varied greatly in metabolisable energy concentration between the 4 periods, being high in autumn (average of 10.2 MJ/kg DM) and low in summer–autumn (average of 8.4 MJ/kg DM). Metabolisable energy apart, there were few differences in the crude protein and detergent fibre contents of ryegrass and paspalum. Perennial ryegrass is generally considered a superior feed to paspalum, but the data indicate this is not always the case under irrigation in northern Victoria. The nutritive characteristics of the plant fractions (leaf, stem, dead, inflorescence) were analysed separately to give an indication of the limits to selection by grazing cows. Differences in metabolisable energy between leaf and stem in both white clover and perennial ryegrass suggested that grazing dairy cows could consume a pasture diet which is likely to be slightly higher in energy than that in the herbage on offer. With paspalum, this is unlikely to be the case because differences in energy content between plant parts were small. However, with all species, cows should be able to consume herbage that is significantly higher in protein, and lower in detergent fibre, than that on offer because of differences in their concentrations in leaf and stem. The nutritive characteristics of morphological components of each species remained relatively constant throughout the study. Therefore, it would seem that it is the proportions of these fractions in the plant, together with severity of grazing, that will largely determine the degree of selection that can occur.

Dry matter intake and nutrient selection by lactating cows grazing irrigated pastures at different pasture allowances in summer and autumn

1998 ◽  
Vol 38 (5) ◽  
pp. 451 ◽  
Author(s):  
W. J. Wales ◽  
P. T. Doyle ◽  
D. W. Dellow
Keyword(s):  
Milk Production ◽  
Perennial Ryegrass ◽  
Crude Protein ◽  
Dry Matter ◽  
Fibre Content ◽  
Lactating Cows ◽  
Dry Matter Digestibility ◽  
Herbage Intake ◽  
Selection For

Summary. Three experiments investigating the effects of herbage allowance on the consumption of nutrients by lactating cows were conducted on irrigated perennial pastures in northern Victoria during summer and autumn. Experiment 1 was conducted in mid lactation (autumn–early winter) with perennial ryegrass [54% of dry matter (DM)]–white clover (22% of DM) pasture offered at allowances of 15, 20, 30 and 40 kg DM/cow.day. Herbage intake increased (P<0.001) from 8.0 to 14.6 kg DM/cow.day as allowance increased and this was associated with a decrease (P<0.001) in utilisation from 54 to 37%. The cows consistently selected a diet 11% higher in in vitro dry matter digestibility than that in the pasture on offer, but selection for crude protein increased (P<0.001) from 21 to 41% above that in herbage on offer as herbage allowance increased. Neutral detergent fibre content of the diet selected was lower (P<0.001) than that in herbage on offer. Along with these changes, milk production increased (P<0.001) from 9.0 to 15.5 kg/day as herbage allowance increased at a marginal response of 0.99 kg milk/kg extra DM consumed. Experiments 2 and 3 were conducted in mid lactation (summer) on pasture containing 28% paspalum, 26% weeds, 17% perennial ryegrass or 36% paspalum, 19% weeds and 24% ryegrass respectively. Pasture allowances were between 20 and 70 kg DM/cow.day. Herbage intake increased (P<0.001) from about 8 to 17 kg DM/cow.day as allowance increased in both experiments and was accompanied by a decrease (P<0.001) in utilisation from about 40 to less than 25%. In experiment 2, the cows consistently selected a diet with a similar in vitro dry matter digestibility to that of the herbage pregrazing, regardless of allowance, but selection for crude protein increased (P<0.05) from 25 to 45% above that in herbage on offer, as allowance increased. In experiment 3, the diet selected was 13% greater (P<0.001) in in vitro dry matter digestibility and 42% greater (P<0.001) in crude protein than the herbage on offer. Neutral detergent fibre content of the diet selected was lower (P<0.001) than that in herbage on offer in experiment 3, while the difference was small in experiment 2. Along with these changes, milk production increased (P<0.001) (in experiment 2, 12.3–15.0 kg/cow.day; experiment 3, 10.0–15.8 kg/cow.day) as herbage allowance increased, but the marginal responses were lower (0.28 kg milk/kg extra DM consumed in experiment 2, 0.64 kg milk/kg extra DM consumed in experiment 3) than observed in experiment 1 reflecting the differences in pasture quality.

Dry matter intake, nutrient selection and milk production of dairy cows grazing rainfed perennial pastures at different herbage allowances in spring

1999 ◽  
Vol 39 (8) ◽  
pp. 923 ◽  
Author(s):  
P. J. Moate ◽  
D. E. Dalley ◽  
J. R. Roche ◽  
C. Grainger
Keyword(s):  
Dairy Cows ◽  
Milk Production ◽  
Crude Protein ◽  
Dry Matter ◽  
Dry Matter Intake ◽  
Neutral Detergent Fibre ◽  
Dry Matter Digestibility ◽  
Herbage Intake ◽  
Selection Differentials

Summary. The effect of herbage allowance (20, 30, 40, 50, 60 and 70 kg DM/cow. day) on the consumption of nutrients from herbage and milk production by cows in early lactation, was examined. The experiment was conducted on rainfed perennial ryegrass pastures in September and October 1997 in south-eastern Victoria, Australia. The herbage on offer comprised 64% perennial ryegrass, 21% other grasses, 1% white clover, 5% weeds and 9% dead material on a dry matter (DM) basis. The average pregrazing herbage height was 13 cm, at an estimated pregrazing herbage mass of 3.6 t DM/ha. The herbage on offer was of high quality containing 11.6 MJ metabolisable energy/kg DM, 202 g crude protein/kg DM and 525 g neutral detergent fibre/kg DM. Concentrations of calcium, magnesium, sodium, potassium, phosphorus, sulfur and chloride were 4.4, 2.2, 4.4, 31.2, 3.5, 2.7 and 11.4 g/kg DM, respectively. As daily herbage allowance per cow increased, dry matter intake increased curvilinearly (P<0.01) from 11.2 to 18.7 kg DM/cow. day. This was associated with a decrease in utilisation of herbage from 54 to 26% and an increase in milk production from 25.9 to 29.1 kg/cow. day. The cows on all treatments grazed for less than 8.7 h/day. The increase in intake was achieved by an increase in the rate of herbage intake from 1.5 to 2.2 kg DM/h for herbage allowances of 20 and 70 kg/cow.day, respectively. Irrespective of herbage allowance, cows selected a diet that was approximately 10% higher in in vitro dry matter digestibility and 30% higher in crude protein than that in the herbage on offer. The neutral detergent fibre content of the herbage selected was lower (P<0.05) than that on offer. The herbage consumed contained more (P<0.05) magnesium, potassium and sulfur, the same amount of calcium and phosphorus and less (P<0.05) sodium and chloride than the herbage on offer. For rainfed perennial pastures in spring, herbage allowance is an important factor in determining voluntary feed intake and production of dairy cows. To achieve 30 L from herbage, without supplementation, high herbage allowances are required. The increase in herbage intake, with increasing herbage allowance, resulted from an increase in rate of dry matter intake and not an increase in grazing time. No relationship was evident between herbage allowance and the selection differentials for in vitro dry matter digestibility, crude protein and neutral detergent fibre. Selection differentials for rainfed perennial pastures in spring are similar to those reported for irrigated perennial pastures in northern Victoria in spring and autumn. When determining nutrient requirements it is important to consider the interaction between herbage intake and nutrient concentration in the herbage.

scholarly journals Herbage intake in Danish Jersey and Danish Holstein steers on perennial ryegrass/white clover pasture

2004 ◽  
Vol 86 (1-3) ◽  
pp. 261-267 ◽  
Author(s):  
B Nielsen ◽  
S.M Thamsborg ◽  
H.R Andersen ◽  
T Kristensen
Keyword(s):  
Perennial Ryegrass ◽  
White Clover ◽  
Herbage Intake ◽  
Clover Pasture

Performance of lambs and the incidence of staggers and heat stress on two perennial ryegrass (Lolium perenne) cultivars using a leader-follower rotational grazing management system

2001 ◽  
Vol 136 (1) ◽  
pp. 99-110 ◽  
Author(s):  
S. J. BLUETT ◽  
J. HODGSON ◽  
P. D. KEMP ◽  
T. N. BARRY
Keyword(s):  
Organic Matter ◽  
Heat Stress ◽  
Lolium Perenne ◽  
Perennial Ryegrass ◽  
Nutritive Value ◽  
Fibre Content ◽  
Serum Prolactin ◽  
Neutral Detergent Fibre ◽  
Organic Matter Digestibility

A summer lamb finishing experiment at Palmerston North, New Zealand compared the performance and health of weaned lambs grazing Aries HD or Yatsyn 1 perennial ryegrass (Lolium perenne). Aries HD ryegrass was originally selected for increased digestibility over summer and early autumn. Two groups of Romney×Suffolk lambs (15 per group) were rotationally grazed on each cultivar in a leader-follower sequence to assess both the nutritive value of the pastures and the alkaloid challenge imposed by the respective cultivar/endophyte (Neotyphodium lolii) associations. Herbage from leader pastures contained a higher content of ryegrass (600 v. 474±27·3 g/kg, P < 0·001) and a lower content of dead material (355 v. 479±34·2 g/kg, P < 0·001) than follower pastures. The in vitro organic matter digestibility coefficient of leader pastures was greater (0·62 v. 0·55±0·024, P < 0·05) and the neutral detergent fibre content lower (592 v. 631±11·4 g/kg, P < 0·005) than follower pastures. Consequently, the leader lambs had faster liveweight gains (92 v. 53±10·6 g/day, P < 0·0005) than the follower lambs. Aries HD and Yatsyn 1 cultivars were similar in sward composition, in vitro organic matter digestibility, neutral detergent fibre content and nitrogen content. Lambs grazing Aries HD had a higher herbage intake in late January than lambs grazing Yatsyn 1 pasture (0·95 v. 0·85±0·023 kg OM/day, P < 0·005). Overall, the liveweight gains of lambs grazing Aries HD and Yatsyn 1 were similar (71 v. 73±10·6 g/day, P > 0·7).Grazing sequence and cultivar did not affect the concentrations of lolitrem B and peramine from herbage cut to ground level. However, serum prolactin concentration, which can indicate ergovaline intoxication, was lower in lambs grazing follower swards (181 v. 120±18·0 ng/ml, P < 0·005). Ergovaline concentration in Aries HD herbage was about half the concentration detected in Yatsyn 1 herbage (0·25 v. 0·49±0·050 mg/kg, P < 0·001). In addition, respiration rate, which can be an indicator of heat stress, was higher in lambs grazing Yatsyn 1 than Aries HD (77 v. 74±1·1 breaths per minute, P < 0·005). All lambs on all treatments had clinical ryegrass staggers from 10 February to 9 March. Lambs were removed from the experiment on 9 March. Both grazing sequence and cultivar affected the severity of ryegrass staggers. Staggers score was highest in Yatsyn 1 followers (4·4) and lowest in Aries HD leaders (3·1). Both grazing sequence and cultivar affected the alkaloid challenge imposed on lambs, resulting in differences in staggers severity, heat stress and performance of the lambs over the summer and autumn period.

Dietary preferences of cows offered choices between white clover and 'high sugar' and 'typical' perennial ryegrass cultivars

2006 ◽  
Vol 46 (12) ◽  
pp. 1579 ◽  
Author(s):  
S. A. Francis ◽  
D. F. Chapman ◽  
P. T. Doyle ◽  
B. J. Leury
Keyword(s):  
Perennial Ryegrass ◽  
White Clover ◽  
Crude Protein ◽  
Water Soluble ◽  
Soluble Carbohydrate ◽  
Intake Rate ◽  
Neutral Detergent Fibre ◽  
Dietary Preferences ◽  
Structural Carbohydrate ◽  
Partial Preference

An experiment was conducted to compare dietary preferences of cows offered simple choices between spatially separated monocultures of perennial ryegrass cvv. AberDawn (AD) and AberElan (AE), and white clover (WC) under strip grazing. AberDawn was bred to express high water soluble carbohydrate concentrations, whereas AE has typical levels. The proposed hypotheses were that cows would exhibit a partial preference for the ryegrass cultivar with a higher concentration of non-structural carbohydrates, and that there would be an interaction between the non-structural carbohydrate concentration of the ryegrass and strength of preference for WC. Non-lactating cows were offered a pasture allowance of about 20 kg DM each day for 9 days in 3 ‘choice’ treatments: AD + WC, AE + WC and AD + AE. All pastures had similar estimated metabolisable energy contents, but AD had a higher crude protein (136 v. 118 g/kg DM) and slightly lower neutral detergent fibre (480 v. 497 g/kg DM) concentration than AE, and non-structural carbohydrate concentrations were similar in both grasses. White clover had higher crude protein (236 v. 127 g/kg DM), and lower neutral detergent fibre (317 v. 489 g/kg DM) and non-structural carbohydrate concentrations (140 v. 183 g/kg DM), and contained less dead material (60 v. 242 g/kg DM) than the grasses. AberDawn contained less (P<0.05; 578 v. 698 g/kg DM) green ryegrass than AE. Pre-grazing pasture mass (1870 v. 2010 kg DM/ha), pasture allowance (23 v. 25 kg DM/cow), and residual pasture mass (1610 v. 1710 kg DM/ha) were lower for AD than AE, and for WC were lower (P<0.05) than for both grasses. Dry matter intake, intake rate and bite size were lower (P<0.05) on AD + AE than on treatments containing WC. Cows grazing AD + AE ruminated longer (P<0.05), ruminated more (P<0.05) boli, and had more (P<0.05) ruminating chews than those on treatments including WC. The cows on AD + AE had more (P<0.05) total chews than those on AD + WC or AE + WC, but grazing time was not always significantly different between choice treatments. It is suggested that the longer ruminating times and greater number of boli processed in cows grazing only grass may reflect the slower digestion rates of ryegrass compared with clover. Cows grazing the AD + WC or AE + WC choice treatments showed a partial preference for WC, spending more (P<0.001) time grazing and consuming more (P<0.001) WC than ryegrass. Within the AD + AE choice treatment, cows spent more (P<0.05) time grazing and consumed more (P<0.05) AE than AD. Using the mean of 2 methods of estimation, the partial preferences for AD + WC, AE + WC and AD + AE were 39 : 61, 41 : 59 and 45 : 55, respectively.

The assessment of herbage legume varieties. II. In vitro digestibility, water soluble carbohydrate, crude protein and mineral content of primary growth of clover and lucerne

1966 ◽  
Vol 66 (3) ◽  
pp. 351-357 ◽  
Author(s):  
W. Ellis Davies ◽  
G. ap Griffith ◽  
A. Ellington
Keyword(s):  
White Clover ◽  
Crude Protein ◽  
Dry Matter ◽  
Red Clover ◽  
Water Soluble ◽  
Soluble Carbohydrates ◽  
Soluble Carbohydrate ◽  
In Vitro Digestibility ◽  
Primary Growth

The primary growth of eight varieties of three species–white clover (3), red clover (4) and lucerne (1)–was sampled at fortnightly intervals and the percentage dry matter, in vitro digestibility, crude protein, water soluble carbohydrates, P, Ca, K, Na and Mg were determined.Differences between species were nearly always significant and the general order of merit was white clover, red clover and lucerne. The exceptions were for dry-matter percentage where this order was reversed, and red clover had the lowest Na and highest Mg content.

Effects of feeding ryegrass of varying maturity on the metabolism and composition of lipids in the rumen of sheep

1986 ◽  
Vol 106 (3) ◽  
pp. 445-448 ◽  
Author(s):  
T. Gerson ◽  
A. John ◽  
A. S. D. King
Keyword(s):  
Fatty Acid ◽  
Lipid Metabolism ◽  
Linoleic Acid ◽  
Blood Plasma ◽  
Polyunsaturated Fatty Acid ◽  
Perennial Ryegrass ◽  
Crude Protein ◽  
Linseed Oil ◽  
Triacyl Glycerol

SummaryTwo experiments were carried out to test the effects of ryegrass maturity on rumen lipid metabolism. In the first experiment the effect of stage of maturity of perennial ryegrass on lipid metabolism in the rumen was studied with grazing sheep fitted with rumen cannulae. The pasture was either immature (13·8% crude protein), mature (8·1% crude protein) or senescent (5·5% crude protein).The ratesin vitroof triacyl glycerol lipolysis and linoleic acid (18: 2w6) hydrogenation were found to decrease with increasing age of the ryegrass.In the second experiment the sheep were dosed with emulsified linseed oil (30 g) via rumen cannulae while grazing immature or senescent ryegrass and the rumen digesta and blood plasma sampled at 0, 4 and 8 h after dosing.The proportions of linseed oil retained in the rumen were greater and blood plasma linoleic (18:2w6) and linolenic (18:3w3) acid concentrations higher when senescent ryegrass was fed.It was concluded that the rates of rumen lipolysis and hydrogenation decreased with the age of pasture and that after dosing with linseed oil the polyunsaturated fatty acid concentrations in blood plasma increased.

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