Effects of irrigating forage turnips, Brassica rapa var. rapa cv. Barkant, during different periods of vegetative growth. 2. Nutritive characteristics of leaves and roots

2011 ◽  
Vol 62 (7) ◽  
pp. 571 ◽  
Author(s):  
B. A. Rowe ◽  
J. E. Neilsen
Keyword(s):  
Dairy Cows ◽  
Brassica Rapa ◽  
Vegetative Growth ◽  
Crude Protein ◽  
Water Soluble ◽  
Cumulative Effects ◽  
Neutral Detergent Fibre ◽  
Structural Carbohydrate ◽  
Metabolisable Energy ◽  
Leaves And Roots

The effects of irrigating spring-sown forage turnips, Brassica rapa var. rapa cv. Barkant, during four discrete but consecutive periods of vegetative growth on the nutritive value of both leaves and roots of turnip was measured three times in 4 weeks in two field experiments conducted in north-west Tasmania during the 1999–2000 and 2000–01 spring and summer seasons. The harvests commenced ~10 weeks after sowing and near the maximum growth rate of the turnip. The harvests coincided with times when turnip would normally be grazed by dairy cows in mid lactation. The aim was to quantify both the effects of applying irrigation during four discrete but consecutive periods of vegetative growth and advancing maturity on metabolisable energy, neutral detergent fibre, crude protein and non-structural carbohydrate in both the leaves and roots. Irrigation applied during the four periods of vegetative growth produced relatively small and sometimes inconsistent effects on the nutritive characteristics of turnip leaf and root as the crop matured. However, their cumulative effect was to reduce both crude protein and the crude protein : non-structural carbohydrate ratio despite increasing total nitrogen uptake, and to increase leaf water-soluble carbohydrate and starch above rainfed turnip. These cumulative effects became more pronounced as the crop maturity increased from 27 to 75 days after the onset of root expansion. The cumulative effects on metabolisable energy and neutral detergent fibre were small and of no agricultural importance. Nutritive values were sufficient to meet the requirement of lactating dairy cows in mid lactation except for fibre and root crude protein.

Nitrogen fertiliser effects on nutritive characteristics of perennial ryegrass during late autumn, and mid- and late winter in western Victoria

2002 ◽  
Vol 42 (5) ◽  
pp. 541 ◽  
Author(s):  
J. L. Jacobs ◽  
F. R. McKenzie ◽  
G. A. Kearney
Keyword(s):  
Protein Content ◽  
Perennial Ryegrass ◽  
Crude Protein ◽  
Dry Matter ◽  
Water Soluble ◽  
Nitrate Content ◽  
Crude Protein Content ◽  
Nitrogen Fertiliser ◽  
Neutral Detergent Fibre ◽  
Metabolisable Energy

A study determined the effects of differing rates of nitrogen fertiliser [0 (N0), 25 (N1), 50 (N2) and 75�kg N/ha (N3)] during late autumn (T1) and mid- (T2) and late (T3) winter on the nutritive characteristics of perennial ryegrass over a 28-day period after each application. All nitrogen applications were made to pastures with a post-grazed residual mass (dry matter) of 1400 kg/ha. Changes in metabolisable energy followed similar patterns for all treatments within a given period. Metabolisable energy was highest in T1, ranging from 11.8 to 13.1 MJ/kg dry matter, followed by T2 (11.5-12.3 MJ/kg dry matter) and T3 (10.6-11.5 MJ/kg dry matter). Changes in crude protein for all treatments at each application time were similar, irrespective of rate of nitrogen application. At the commencement of treatment application times, the existing crude protein content (%DM) was highest in N3 (T1�19, T2 23, T3 22), followed by N2 (T1 18, T2 21, T3 21), N1 (T1 17, T2 20, T3 20) and N0 (T1 16, T2 17, T3 18). During both T1 and T2, neutral detergent fibre content decreased by 4 percentage units and increased by a similar amount during T3. Generally, neutral detergent fibre content (%DM) was highest during T3 (53-58%), followed by T2 (45-54%) and T1 (43-49%). Water-soluble carbohydrate content (%DM) increased during all treatment periods with the highest level observed during T1 (18-31%) followed by T2 (3-14%) and T3 (1-6%). Nitrate content (measured as nitrate-nitrogen) decreased throughout T1, primarily due to dry conditions, while during T2, levels for N3 and N2 were significantly (P<0.05) higher than for N1 and N0 following nitrogen fertiliser application. During T3, nitrate content increased for all treatments throughout the 28-day period, with highest nitrate levels being observed during T3. The effect of applied nitrogen on mineral content was variable within and across treatment periods. The study indicates that nitrogen fertiliser did not affect metabolisable (apart from N3 elevating metabolisable energy during T3), neutral detergent fibre or water-soluble carbohydrate contents of perennial ryegrass during the 28 days after nitrogen application, but increased crude protein content. Also, nitrogen fertiliser elevated nitrate content in perennial ryegrass. While the elevated nitrate content observed may result in subclinical effects, these levels are not considered fatal for dairy cows. Crude protein content was generally above 20% of dry matter throughout the study and close to 30% of dry matter for short periods during T2. Minimising the effect of excess nitrogen ingested by the grazing animal may require appropriate supplementation of low crude protein containing feeds such as cereal grains. It is argued that the effects of rain and temperature, which impact on soil nitrogen mineralisation, may have a greater influence on perennial ryegrass nitrate content than nitrogen fertiliser.

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.

Supplementation of grazing dairy cows with a brewers grains/treated straw mixture

1990 ◽  
Vol 1990 ◽  
pp. 46-46 ◽  
Author(s):  
J.D. Leaver ◽  
R.C. Campling
Keyword(s):  
Dairy Cows ◽  
Crude Protein ◽  
Dry Matter ◽  
Barley Straw ◽  
Severe Drought ◽  
Grass Silage ◽  
Metabolisable Energy ◽  
Grazing Dairy Cows ◽  
Similar Cost ◽  
Friesian Cows

Supplementary feeding of grazing dairy cows is often uneconomic, and whilst supplementation with silage (buffer feeding) can be worthwhile, this often leads to a depletion of winter forage stores. In this study, a mixture of brewers grains and treated straw was used as a supplement. Offered as a 1:1 mixture in the dry matter (DM), it is a purchased substitute for grass silage, having a similar cost, and similar metabolisable energy (ME) and crude protein (CP) contents. The high seasonality adjustments to milk price in mid-late season make supplementation potentially worthwhile.Experiments were carried out from April to September in 1988 and 1989, which had moderate and very low rainfall respectively. Each year 20 British Friesian cows which calved December to March (1988 experiment) and February-April (1989) were allocated at random to either treatment B or C. In B, the cows were offered a 1:1 mixture (DM basis) of brewers grains and NaOH treated chopped barley straw for 60 minutes after morning milking. In C, the cows received no supplement. Both groups were fed 1.0 kg/day of concentrates in the milking parlour. Due to the severe drought in 1989, concentrate feeding was increased to 5.0 kg/day for all cows during the last 4 weeks of the experiment. Also, urea-treated whole crop wheat was fed at a level of 2.5 kg DM/day during the last 7 days.

The relative importance of energy and protein in the concentrate on intake and yield of milk constituents by freisland ewes offered hay ad-libitum

1994 ◽  
Vol 1994 ◽  
pp. 207-207
Author(s):  
R.G. Wilkinson ◽  
C.M. Minter ◽  
G. Duffy ◽  
J. Celerier
Keyword(s):  
Dairy Cows ◽  
Crude Protein ◽  
Relative Importance ◽  
Dairy Sheep ◽  
Total Response ◽  
Metabolisable Energy ◽  
Forage Intake ◽  
Fat Yield ◽  
Protein Supply ◽  
To Receive

Increasing the level of concentrate fed to lactating ruminants reduces forage intake, but increases the yield of milk and milk constituents (Aston et al. 1991). However, the proportion of the total response due to additional metabolisable energy (ME) or crude protein supply (CP) is unclear. Recent work with dairy cows (Aston et al. 1992) suggests that additional ME or CP fed as concentrate reduced and slightly increased silage intake respectively. Additional CP had twice the effect on milk and three times the effect on protein yield than additional ME. However, ME and CP were equally important in determining fat yield. The objective of the trial was to investigate whether dairy sheep respond to additional ME or CP supply as concentrate in a similar way to dairy cows.Three concentrate diets were formulated to contain 13.0 MJ/kg DM ME and either 100 (A), 200 (B) or 400 (C) g/kg DM CP. After weaning (6 weeks), 24 mature Freisland ewes were housed individually, and allocated by liveweight and initial milk yield to receive concentrate DM at daily rates of 0.8 kg, providing 10.4 MJ/day ME and 160 (B) or 320 (C) g/day CP (LLP, LHP), or 1.6 kg, providing 20.8 MJ/day ME and 160 (A) or 320 (B) g/day CP (HLP, HHP). The trial lasted 8 weeks and was analysed as a 2 X 2 factorial design.

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.

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.

Effects of treatment with a gonadotrophin-releasing hormone analogue on follicle development in dairy cows fed one of two different diets

2001 ◽  
Vol 26 (2) ◽  
pp. 451-455
Author(s):  
E.C.L. Bleach ◽  
C.L. Moore ◽  
H.J. Zeale ◽  
P.G. Knight
Keyword(s):  
Dairy Cows ◽  
Luteal Phase ◽  
Cycle Length ◽  
Crude Protein ◽  
Oestrous Cycle ◽  
Follicle Development ◽  
Releasing Hormone ◽  
Ovulatory Follicle ◽  
Metabolisable Energy ◽  
Phase Length

AbstractFollicle development occurs in two or three waves during the bovine oestrous cycle. Artificially extending the duration of ovulatory follicle dominance influences pregnancy rates in cattle, as does the interval from emergence to oestrus in dairy cows undergoing spontaneous oestrous cycles. The objectives of the presented study were to determine whether the interval from ovulatory follicle emergence to oestrus might be altered by diet and/or gonadotropin-releasing hormone (GnRH) treatment. Lactating primiparous Holstein/Friesian cows (n=21) were randomly allocated to one of two diets at calving (Diet 1, n=ll, DM 480 g/kg, metabolisable energy 12.0 MJ/kg DM crude protein 178 g/kg DM, oil B 48 g/kg DM, neutral detergent fibre 318 g/kg DM and diet 2, n=10, DM 440 g/kg, metabolisable energy 12.1 MJ/kg DM, crude protein 172 g/kg DM, oil B 40 g/kg DM, neutral detergent fibre 300 g/kg DM). From 10 days after observed oestrus (oestrus 1), ovarian follicular and luteal development was monitored by daily transrectal ultrasonography until the subsequent oestrus and ovulation. A GnRH analogue was injected (i.m.; 10 μg) 12 days after oestrus 1 in 6 cows fed diet 1 and 5 cows fed diet 2. Oestrous cycle length was longer (p<0.05) in control cows fed diet 1 than those fed diet 2. Treatment with GnRH increased (p<0.005) cycle length in cows fed diet 2 but not those fed diet 1. Increases in cycle length observed were associated with longer luteal phase length. Follicular phase length was reduced (p<0.05) by GnRH treatment in cows fed diet 1. Ovulatory follicles emerged later (p<0.05) in control cows fed diet 1 than those fed diet 2. GnRH treatment delayed (p<0.01) the emergence of the ovulatory follicle in cows fed diet 2, this delay was associated with an increase (p<0.05) in the incidence of 3 follicle waves in oestrous cycles following GnRH treatment. The interval from emergence of the ovulatory follicle to the subsequent oestrus was similar among the treatment groups. We conclude that treatment with GnRH during the mid-luteal phase may delay the emergence of the ovulatory follicle. However, the response is dependent on diet fed. Where ovulatory follicle emergence is delayed, the interval from emergence to the subsequent oestrus was unaffected since oestrous cycle length is extended.

scholarly journals Grazing Preference of Dairy Cows and Pasture Productivity for Different Cultivars of Perennial Ryegrass under Contrasting Managements

Animals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 253 ◽  
Author(s):  
M. Jordana Rivero ◽  
Oscar L. Balocchi ◽  
Fabián L. Neumann ◽  
Juan A. Siebald
Keyword(s):  
Dairy Cows ◽  
Perennial Ryegrass ◽  
Crude Protein ◽  
Dry Matter ◽  
Genetic Selection ◽  
Fertilization Rate ◽  
Water Soluble ◽  
Sugar Concentration ◽  
Soluble Carbohydrates ◽  
High Sugar

The objective of this study was to evaluate the pasture performance of different cultivars of perennial ryegrass, two “high sugar” and two standard cultivars, under two contrasting agronomic managements (aimed at either decreasing or increasing water soluble carbohydrates concentration), and their effects on the grazing preference of dairy cows. Eight treatments arising from the factorial combination of four cultivars and two managements were randomly applied to 31-m2 plots in three blocks. Pasture dry matter production and growth rate were measured for one year. Three grazing assessments were performed to establish the grazing preferences of six dairy cows in spring, summer and autumn. High sugar cultivars produced less dry matter per hectare than the standard cultivars. Cows consumed more grass and harvested a greater proportion of the pasture under the agronomic management aimed at decreasing sugar concentration, i.e., with a greater nitrogen fertilization rate and under a more frequent defoliation regime, which could be explained by the greater crude protein concentration achieved under this management. The results suggest that the genetic selection for greater levels of sugars was at the expense of herbage yield, and that cows preferred to graze herbage with a greater crude protein level instead of a greater sugar concentration.

Effect of undegradable protein given for six weeks before calving on the performance of dairy cows in the subsequent lactation

1996 ◽  
Vol 1996 ◽  
pp. 85-85 ◽  
Author(s):  
R.J. Dewhurst ◽  
D.W.R. Davies ◽  
W.J. Fisher ◽  
K. Aston
Keyword(s):  
Dairy Cows ◽  
Dietary Protein ◽  
Crude Protein ◽  
Dry Period ◽  
Grass Silage ◽  
Holstein Friesian ◽  
Unrestricted Access ◽  
Metabolisable Energy ◽  
Ad Libitum ◽  
Friesian Cows

Previous studies (Moorby et al, 1994) have shown increased yields of protein and lactose in the subsequent lactation as a consequence of feeding additional undegradable dietary protein (UDP) and restricting energy intake during the dry period. This experiment was undertaken to investigate the effect of supplementary UDP in the dry period diet of Holstein-Friesian cows given unrestricted access to grass silage and 1.5 kg of barley per day.Sixty-one cows received diets based on ad libitum access to grass silage with either (a) 1.5 kg barley / day or (b) 1.0 kg barley and 0.5 kg Maize Gluten Meal / day. After calving, cows had ad libitum access to grass silage (Metabolisable Energy (ME)=11.3 MJ/kg DM; crude protein (CP)=181 g/kg DM) and received 5 kg/day of concentrates (ME=13.0 MJ/kg DM; CP=250g/kg DM).

Effects of increasing the inclusion level of Atriplex amnicola in the diet of sheep

2009 ◽  
Vol 49 (11) ◽  
pp. 1029
Author(s):  
M. B. P. Kumara Mahipala ◽  
G. L. Krebs ◽  
P. McCafferty ◽  
K. Dods
Keyword(s):  
Crude Protein ◽  
Energy Content ◽  
Gas Production ◽  
Mineral Contents ◽  
Neutral Detergent Fibre ◽  
Freeze Dried ◽  
Acid Detergent Fibre ◽  
Inclusion Level ◽  
Metabolisable Energy

The effects of increasing the level of inclusion of fresh Atriplex amnicola Paul G.Wilson foliage in an oaten chaff (Avena sativa L.) diet fed to sheep were investigated. Six experimental diets were formulated to contain varying amounts [0, 161, 362, 496, 650 and 836 g/kg diet dry matter (DM)] of A. amnicola, and these diets were fed to individually penned sheep according to a Latin square design. Feed and faecal samples were analysed for crude protein, neutral detergent fibre, acid detergent fibre, acid detergent lignin, and ash contents. Mineral contents and 24 h in vitro gas production were measured in freeze-dried feed samples. As the level of inclusion of A. amnicola increased, digestibility of DM, organic matter and neutral detergent fibre increased (P < 0.05), reaching the peak at the 496 g/kg DM inclusion level and then decreasing (P < 0.05) thereafter. Acid detergent fibre digestibility followed a similar trend, but peak digestibility was at 362 g/kg DM inclusion level. Digestibility of crude protein continued to increase (P < 0.05) with increasing inclusion of A. amnicola. Gas production (24 h) from A. amnicola was lower (P < 0.05) than that from oaten chaff (24.4 v. 45.3 mL/200 mg DM) and also had lower metabolisable energy content (in vitro ME, 6.3 v. 8.6 MJ/kg DM). As the level of inclusion of A. amnicola in the diet increased, gas production and in vitro metabolisable energy content decreased (P < 0.05). The 496 g/kg DM inclusion level provided the optimum N : energy ratio for fermentation of dietary fibre. At this level of inclusion the diet was rich in Na, Ca, P, Mg, K, S, Mn and Zn. High inclusion levels improved the crude protein value of the diet but compromised fibre digestibility.

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