Livestock Research for Rural Development 2 (1) 1990

Citation of this paper

Evaluation of the basal forage diet of village cows

A A Boodoo, R Ramjee, B Hulman, F Dolberg* and J B Rowe**

Animal Production Division, Ministry of Agriculture, Fisheries and Natural Resources, Reduit, Mauritius

*University of Arhus, Denmark;
**Department of Agriculture, Western Australia

Summary

The forage fraction (especially cane tops which were the dominant component) of the the diet of village cows was assessed by chemical analysis, in situ (nylon bag) rumen degradability and by direct observation of eating behaviour and forage selection practices by the cowkeepers. Cowkeepers discarded cane tops that had flowering heads and carefully removed mature and dry leaves. Cows began eating the cane top starting at the sheath bundle (which represented 48% by weight of the tops) and consumed only part of the green leaf blade, on either side of the midrib. The sheath bundle had less nitrogen (0.88% in DM) and dry matter (19%) than the leaf blade (1.17% N and 31% DM). The mean N content of the assorted forages was 1.6% in DM.

Dry matter degradation in the rumen was more rapid for the sheath bundle (56% loss at 24hr) than for the leaf blade (34%) and was the same as for the assorted forages (55%).

The cowkeepers offered each cow some 70 kg/d of whole cane tops (mean DM = 28%)of which the cows consumed only 55%. Comparable data for the assorted forages were 65 kg offered daily (23% DM) of which 84% was consumed. Total DM intakes were 3.8 and 4.3 kg DM per 100 kg liveweight for cane tops and assorted forages respectively.

Key words: Sugar cane tops, cattle, village cowkeepers, feed intake, rumen degradability, feed selection.

Introduction

The small cattle owners (cowkeepers) in Mauritius make a major contribution (almost 95%) to the national production of fresh milk. A pilot project (Boodoo et al 1990) was executed in two climatic areas of the island on cowkeepers' farms to demonstrate the significance of two concentrate supplements to improve milk production at the village level. In the course of this pilot project (1985 to 1987) regular visits (3 times a week) were made to the cowkeepers' farms and observations were made on management practices and animal behaviour associated with the supply and consumption of fodder. This paper summarises the data on the types of forages used and their digestibility and nitrogen content.

Sugar cane tops are by far the largest single forage source used by the cowkeepers. For this reason they have been considered in some detail in this paper.

Materials and methods

The forage fraction of the diet of the village cows was assessed in a number of ways. Notes were made on the animals' feeding behaviour, particularly with respect to selection amongst the different forage fractions. The quality of the major dietary forages was measured by chemical analysis (nitrogen, crude fibre, ether extract, ash and the minerals Ca and P) and by the rate of degradation of dry matter in nylon bags incubated in the rumen. Measurements were also made of total feed intake during the crop season when cane tops were the main component of the diet and again during the inter-crop season when mixed grasses and vegetable crop residues were the principal feed resources.

Chemical analysis and nylon bag degradability

Samples of forages were taken weekly for chemical analysis and DM degradability in nylon bags. The samples of forage were selected on the basis of the main forage species being used in the area each week. The quality of the cane tops was analysed by first separating them into two fractions. Twenty three samples of cane tops were separated into sheath bundle and leaf blade and the two fractions were analysed for dry matter, nitrogen, crude fibre and nylon bag degradability.

Friesian steers fitted with permanent rumen cannulae were used for the nylon bag work. They were fed a basal diet of mixed grasses consisting mainly of Setaria sphacelata and Ischaemum aristatum (herbe d'argent) at the rate of 20 - 25 kg/d and 1 kg/d cottonseed cake. The fodder was given in two equal portions at 09.00h and 13.00h. The steers also received 10 g common salt and 30 g calcium carbonate per day.

The fodder samples to be tested were first dried at 60C for 48 hours before being ground through a 2.5 mm sieve in a Christy and Norris mill. Four-gram samples were weighed into the nylon bags. Duplicate bags were incubated in each steer for each forage and each time interval (0, 16, 24, 48 and 72h).

Intake

Twenty seven cows from the two areas that hosted the pilot project (30% of the total number) were monitored daily for a period of 15 consecutive days and the amount of fodder offered and consumed was recorded. Fifteen of these cows were monitored during the crop season and twelve in the intercrop season.

Results

Observations on the intake of forages

The cane tops collected by the cowkeepers included no flowering ones. In addition cowkeepers carefully selected the cane tops and discarded the very mature ones. From the cane tops selected in this way, the outer older leaves and all dry ones were discarded.

The cane top consists of a bundle of leaf sheaths (sheath bundle) at the base and leaf blades at the top. The sheaths of the youngest leaves tightly enclose the youngest part of the cane stalk; this youngest part includes the growing point (meristem) of the stalk. It contains a much lower proportion of sucrose than the main portion of the mature stalk, but it is comparatively rich in monosaccharides and non-sugars (Barnes 1974).

The leaf blade and the sheath bundle are separated at the collar. The sheath is greyish in colour; it is attached to the cane stalk and completely surrounds it. The leaf blade is green in colour, grows out from the stalk and tapers to the tip. A midrib extends along the entire length of the blade.

The following features about the cows' feeding behaviour were noted during the farm visits and these observations were confirmed in numerous interviews with cowkeepers:

A complete list of the forage species and vegetable crop residues fed to the cows in the two areas is given in the Appendix. It was observed in the Vacoas area that Ischaemum aristatum (herbe d'argent) generally formed the bulk of the fodder that was given to the cows during the sugar cane inter-crop season whereas other assorted forages (singly or mixed) were given in small amounts, about 5 - 10 kg per cow.

In the Mapou area, Plantago lanceolata (herbe sagne), Digitaria didactyla (petit gazon), Stenotaphrum dimidiatum (herbe bourik) and young cane regrowths (about 50 cm high) generally formed the bulk of the fodder in the inter-crop season. Other assorted forages (singly or mixed), about 5 - 10 kg, were also given to the cows. The amounts of these assorted forages (mixed grasses, creepers, shrubs and twigs) and crop residues fed were about the same in both areas. Of the 525 cane tops that were fractionated, the sheath bundle fraction represented 48.4% (SE = "0.8) and the leaf blade fraction 51.6% (SE = "0.8) by weight of the cane top.

Chemical composition

Data on composition of the cane top fractions are given in Table 1.

Table 1: Chemical composition (%) of whole cane top and its botanical fractions (on dry matter basis). Apart from the "left overs" the fractions were prepared from one original big bundle of cane top.
  ---------- Dry Matter ---------- ---------- Crude Prot ---------- ---------- Crude Fibre ----------
  (n) Mean SE (n) Mean SE (n) Mean SE
Whole canetop (22) 28.3 1.1 (22) 6.3 0.2 (20) 32.2 0.4
Sheath bundle (23) 19.3 1.0 (24) 5.5 0.3 (22) 31.9 0.5
Leaf blade (23) 31.3 0.9 (25) 7.3 0.4 (22) 32.9 0.8
Left-over (16) 35.9 1.6 (16) 5.9 0.2 (13) 33.4 0.8

 

Table 2: Chemical composition (%) of assorted forages and crop residues (on dry matter basis)
  DM CP Ash EE CF Ca P
n 49 49 50 13 15 49 50
Mean 23.1 9.7 9.2 2.2 31.0 0.47 0.21
SE 1.0 0.5 0.4 0.2 1.2 0.46 0.04
Range              
Min 13.3 5.0 3.0 1.5 14.5 0.02 0.14
Max 40.9 14.6 14.2 4.8 37.2 2.2 1.7

 

The sheath bundle fraction has a lower dry matter and crude protein content (19.3% and 5.5% respectively) than the leaf blade (31.3% and 7.3% respectively).

The mean crude protein content of the assorted forages and crop residues (9.7%) is higher than expected indicating the care taken by the cowkeepers in selecting the forage resources. Some of the leguminous forages contained up to 14% crude protein.

Nylon bag degradability

The dry matter degradability values of the various cane top fractions and the other assorted forages are summarised in Table 3. The LSD (P = 0.05) values are also shown.

The results indicate that the sheath bundle fraction degraded much faster than the leaf blade at all the time intervals studied. On the other hand the sheath bundle fraction of cane top and the assorted forages show similar DM degradabilities for the 16 24 48 and 72 incubation periods.

The rate and extent of degradation of the sheath bundle fraction and the assorted forages (about 55% and 63% after 24 and 48 hours respectively) support the view that this is equivalent to a forage of relatively high nutritive value. The sheath bundle and the assorted forages have a potential degradability which is approximately 26% higher than that of the leaf blade.

Table 3: Mean dry matter degradability (%) of whole canetop its botanical fractions and assorted forages at various intervals in nylon bags
    ----------------------- Incubation time (h) -----------------------
  n 0 16 24 48 72
Leaf blade 18 12.0 27.0 34.3 47.0 53.4
SE   0.6 1.1 1.0 1.1 1.1
Whole canetop 18 15.5 35.4 43.6 53.7 59.4
SE   0.4 1.1 1.2 1.0 1.0
Sheath bundle 8 21.5 46.7 55.5 62.6 67.2
SE   0.7 1.5 1.3 1.1 0.8
Assorted Forages 18* 16.4 44.5 54.6 63.5 66.4
SE   0.7 1.6 5.2 1.3 1.3
LSD (P =.05)   2.2 5.2 4.7 4.2 3.8

* These 18 samples were randomly selected from an original list of 49 samples. The means of these 18 samples were almost similar to those of the original 49 samples.

 

Intake

The amount of fresh forage offered and refused the liveweight of the lactating cows and the total dry matter intake are summarised in Table 4 for the two areas.

The cowkeepers offered their cows much more than the latter could consume especially sugar cane tops which are abundant during the harvest season. The 14 - 50% extra that the cows were offered gave them plenty of opportunity to select the best components and this resulted in a very high intake (about 4 kg DM/100 kg LW) as is shown by the relationship between liveweight and total DM intake.

Discussion

The age-old practice of cowkeepers in Mauritius as far as forage feeding is concerned is a wise practice which is being scientifically documented in this work. With time the cowkeepers have developed an appreciation of forage quality. This is illustrated in the relatively high dry matter degradability of the sheath bundle fraction of cane top and other selected forages that they use. This inference is further supported by the relatively high levels of dry matter intake that have been recorded from measurements on the village cows.

Table 4: Quantity of forage offered and refused liveweight of the cows and their total DM intake for a diet consisting predominantly of (a) cane tops with some grasses and crop residues and (b) mixed grasses with some other forages
  ------------- Vacoas ------------- ------------- Mapou -------------
  Cane tops Mixed grasses Cane tops Mixed grasses
n 7 7 9 5
         
Feed offered (kg fresh/d)      
Mean 69.3 68.0 73.1 62.6
SE 4.1 4.3 1.0 4.2
         
Feed eaten (kg fresh/d)      
Mean 46.0 59.6 51.8 51.8
SE 2.5 2.1 2.0 2.0
         
Surplus feed (% of amount eaten)      
Mean 50.6 14.1 41.1 20.8
SE 7.2 2.8 5.0 3.1
         
Liveweight (kg)        
Mean 342 353 364 311
SE 21.8 13.3 11.4 16.0
         
Total intake (kg DM/d)*      
Mean 12.2 15.3 14.7 13.6
SE 1.1 0.5 0.7 0.9
         
Total intake (kg DM/100 kg Liveweight)*      
Mean 3.6 4.4 4.1 4.3
SE 0.3 0.2 0.3 0.4

* Includes concentrate

 

The level of intake observed in this study is perhaps higher than commonly found in the literature. However it has been demonstrated recently (Hovell et al 1986; Orskov et al 1985) that voluntary intake was better related to potential degradability (and degradability at 12 24 48 and 72 hours) than to in vivo digestibility and that even a small difference in the rate and extent of degradation can have large effects on intake. These results tend to be supported by the results of the present work.

In the forage evaluation part of this experiment it is clear that both the extent of degradability of dry matter and its rate of degradability are relatively good with respect to other tropical forages (Preston 1985; Hovell 1985; Orskov et al 1980). The sheath bundle fraction of cane top and the good quality of the assorted forages are clearly the basic reasons for the good milk production in the villages compared to other large scale systems of production where there is less attention to detail in selecting forages.

Acknowledgement

The authors thank the Agricultural Chemistry Division for chemical analyses: the MSIRI (Mauritius Sugar Industry Research Institute) for identifying the names of the various forages; and the Agronomy Division for statistical help. Special thanks go to the cowkeepers who cooperated with us during the visits.

References

Barnes A C 1974 The sugar cane. The world crop series. (Editor: N Polunin).

Boodoo A A Ramjee R Hulman B Dolberg F and Rowe J B 1990 Cowfeed and cottonseed cake to improve milk production at village level. LIvestock Research for Rural Development 1:

Hovell DeB F D 1985 Thoughts on roughage digestion by ruminants; A review article. The Rowett Research Institute. Annual Report of studies in Animal Nutrition and Allied Sciences. Volume 40

Hovell DeB F D Ngambi J W w Barber W P and Kyle D J 1986 The voluntary intake of hay by sheep in relation to its degradability in the rumen as measured in nylon bags. Animal Production 42:111-118

Orskov E R Hovell DeB F D and Mould F 1980 The use of the nylon bag technique for the evaluation of feedstuffs. Tropical Animal Production 5:195-213

Orskov E R Silva A T and Lufadeju E 1985 Aspects of digestion and metabolism when ruminants are given diets based on poor quality crop residues. In: Proceedings of an international workshop held in Khon Kaen Thailand. (Editors: M Wanapat and C Devendra) November 29 - December 2 1984

Preston T R 1985 Associative effects and interactions among feed ingredients (Editors:Rene Sansoucy and T R Preston) In AReport of the FAO Expert consultation on the substitution of imported concentrate feeds in animal production systems in developing countries@ Bangkok 9 - 13 September 1985 FAO

 

Appendix 1: List of assorted fodder - grasses vegetable crop residues twigs shrubs creepers and tree foliage
  Common name Botanical name Use*
Grasses      
  Setaria Setaria sphacelata 3
  Sugar cane Saccharum officiniarum 1
  Elephant Pennisetum purpureum 2
  D'Argent Ischaemum aristatum 1
  Bourik Stenotaphrum dimidiatum 1
  Fatak Panicum maximum 1
  Guatemala Tripsacum laxum 3
  Herbe bol Hydrocotyle bonariensis 3
  Herbe pogne (gandole) Basella alba 3
  Herbe bouc Agiratum conyzoides 3
  Petit Gazon Digitaria didactyla 1
  Herbe Panpatoa Thunbergia alata 3
  Herbe Queue de rat Stachytarpheta jamaicensis 3
  Lepta (gallon) Desmodium incanum 2
  Chirchiria (sergent) Achyrantes aspera 3
  Lastron Sonchus caetharticus 3
    Emilia sonchifolia  
  Doudia Rouge (Jean Robert) Euphorbia hirta 3
    Eupatoria pallescens  
  Pourpier Portaluca oleracea  
  Herbe Creole Paspalum conjugatum 1
  Basawni (bambous) Setaria barbata 3
  Mehenki Brachiaria eruciformis 1
  Phoolalki (herbe rouge) Rhynchelytrum repens 2
  (Natal red top grass)    
  Herbe Caille Tridax procumbens 3
  Herbe Duvet Paspalum paniculatum 1
  Voune Typha domingensis 3
  Makalia Dactyloctenium ctenoides 2
  Herbe Panna/Sagne (Caroline) Plantago lanceolata 1
  Sikkin (Sikia herbe Pipe Paillasse) Sporobolus capensis 1
  Rura (brede Caya) Cleome viscosa 3
  Cinq sous Boerhavia diffusa 2
  Chiendent Cynodon dactylon 1
Vegetables their residues and fruits    
  Sweet potato Ipomea batatas 2
  Banana Musa acuminata 2
  Papaye Papaya carica 2
  Pistache    
  Arachide Arachis hypogea 1
  Voehme Vigna unguiculata 2
  Embrevade Cajanus cajan 2
  Herbe Chinois (herbe Dife) Artemisia vulgaris 3
  Brede Martin Solanum nigrum 3
  Brede Malbar Amaranthus dubius vividis 3 
Shrubs and trees    
  Kandille Hibiscus spp 2
  Privet Lingustum robustum 2
  Bois d'Oiseaux petite feuille Litsea glutinosa 1
  Bois d'Oiseaux gros feuille Litsea monopetela 1
  Bois Noire Albizia lebbeck 1
  Poivre Marron Schinus terebenthifolius 3
  Benga (herbe La mare)    
  (herbe Gandia) Ludwigia octovalvis 1
  Feuille Rougevert Euphorbia cyathophora 3
  Acacia Leucaena leucocephala 1
Creepers       
  Liane Lastic Ipomoea obscura 1
  Liane Lengue Paederica fetida 1
  Liane Poc Poc Passiflora suberosa 1
  Ipeca (blanc) sauvage Cyranchum calliata 3
  Herbe Piment/Pistache Asystasia gangetica 1
  Liane Lapin Ipomoea indica 2
  Herbe Kena (Herbe aux Cochons) Commelina diffusa 1
  Liane Margoze Mikania scandens 3
  La Liane du Lait Ipomea alba 3
  Water Hyacinth Eichhornia crassipes 3
  Liane Pauline Mikania scandens 1

* Indicates how common these forages are:

1 = widely used
2 = normally used
3 = sometimes used