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Citation of this paper

Use of supplement levels of Stylosanthes scabra (Stylo) leaf meal on milk yield of Ankole cows

M Mupenzi, E Karenzi*, J Kanani* and A Lussa Birasa

Institut des Sciences Agronomiques du Rwanda (ISAR), Karama Research Station, Feeds and Feeding Research Program, P.O. Box 5016 Kigali, Rwanda
mmutimura@yahoo.co.uk
*National University of Rwanda (NUR), Faculty of Agriculture, P.O. Box 117 Butare, Rwanda

Abstract

A study was conducted in the research station of the Institut des Sciences Agronomiques du Rwanda (ISAR), Karama research station in order to evaluate the effect of the various levels of supplement of Stylosanthes scabra (Stylo) leaf meal on the milk production of the Ankole cows. Sixteen cows with average live weight of 330 kg in the same stage of lactation were selected for the experiment. Each feed ration was assigned to each treatment of 4 cows. SS0 (control) was fed on the natural pasture; other treatments: SS10, SS20 and SS30 received supplement of Stylo leaf meal at the rates of 10; 20 and 30% of dry matter (DM) corresponding to 1; 2 and 3 kg of DM respectively. The duration of the study was 2 months. Data were collected on milk yield (in liters) and on chemical feed analysis namely neutral detergent fiber (NDF), acid detergent fiber (ADF), crude proteins (CP), phosphorus (P) and calcium (Ca).

 

It has been noticed that the content of CP in Stylo was 21% and 6.1% in natural pasture. The average intake of the supplement per day was high in SS30 (2.5 kg of DM/day) followed by SS20 (1.7 kg of DM/day) and finally comes SS10 (0.7 kg of DM/day). The quantity of milk produced was significantly high (p< 0.05) in the treatment having received supplements of Stylo than in the treatments fed on natural pasture. It was noticed that the greatest milk production was obtained in the cows which received 30% (3 kg of DM) of Stylo, followed by SS20 and SS10 which received 20% and 10% of Stylo respectively. At the end of experiment, it was suggested that 3 kg of DM of Stylo was the optimal level of supplement for the milk production of 1.80 l/day of Ankole cow.

Key words: Ankole cows, milk production, Stylosanthes scabra leaf meal


Introduction

Rwandan economy is dependent on agriculture and livestock production with more than 85% of the population relying on agriculture and livestock production for livelihood (MINAGRI 2001). Rwandan rate of population growth is very high; this has put a pressure on the arable lands and pastures. These cause the reduction of cattle population which led also to the deficit of animal protein in the diet of the majority of the Rwandans. However, cattle production occupies an important place and plays a principal role in the economic and social life of the Rwandans. Furthermore, the local cattle Ankole, is the most representative cattle and most popular in Rwanda (Ndoba 2000). Cattle owners have started to improve Ankole by the introduction of the exotic blood, but their genetic potentials are not yet well-known.

 

Likewise, all cattle genetic improvement start with the Ankole breed thanks to its hardiness.  If it were subjected to better management and feeding, it could uplift its genetic potentials and its performances of reproduction which remain currently very low. The feed remains always a capital constraint for the improvement of the cattle production in Rwanda. Many livestock owners in the country use semi-intensive system. According to MINAGRI (1997) this mode of cattle production is practiced by more than 62% of the cattle keepers, except in the eastern region of the country where it is 14.3%.

 

Everywhere in the grazing land, there is dominance of grass in comparison with legumes and the animals are also offered grasses as supplement (Pennissetum purpureum, Setaria sphacelata and other grass pastures cultivated on the bund for the erosion control). Furthermore, concentrates are very expensive under the local farmer conditions, and the effectiveness of the use of legumes in the ration of the animals remains low. Under the situation it is necessary to incorporate fodder legumes in the animal feeding system for economic milk production by Rwandan farmers.  Among the factors that contribute to the milk yield, feeding occupies the key role along with pests and disease control. Relying on the natural grass feed only is insufficient for lactating and in-calf animals for high productivity. For a clear increase in the livestock production, the contribution of fodder legume in the ration is one of the solutions suggested, because of its impact on the growth and the production, and of its accessibility to the small holder farmers compared to the concentrates. This study aimed to highlight the influence of Stylosanthes scabra as supplement feed on the milk production of the Ankole cows. The objective was to contribute to the increase of milk production of Ankole cow starting with the improvement of the natural pasture by supplementation with fodder legume (Sthylosanthes scabra). It is within this frame the hypothesis that: introduction of Stylosanthes scabra as supplement of basic feed (natural pasture) significantly increases the milk production of the Ankole cows.

 

Materials and methods 

Location of study

 

The study was conducted in the research station of the ISAR-Karama located in the district of Bugesera, eastern province of Rwanda. The geographical positions are 1’300– 30° 25 East and 2° 05- 2° 30 South and an altitude of 1400 m a.s.l (Munyemana 2001). According to the classification of Koppen, the climate of Bugesera is of the Aw type 3-4 characterized by an average temperature of the coldest month higher than 18°C and a dry season of 3 to 4 months (Munyemana 2001). According to Chapelle (1978) cited by Rwicaninyoni (1987), the rainfall is frequently in lower part of 1000 mm and reached an average of 950 mm per year, which induces a rather dry climate. According to the same author, the daily temperatures generally vary between 15°C and 28°C with an average of 21.5°C. The average relative sunshine calculated in 18 years is 51.5%, the relative humidity of the air is around 73.5% and the mean velocity of the wind is of 3.68 km/h. The vegetation is marked by the abundance of xerophilous thickets in dense formation. These thickets join together a hundred species where dominate Carissa sp, Haplocoelum spp, Olea spp, of the small lawns graminaceous, especially Brachiaria which grow between the thickets. These thickets characterize the local pastures (Munyemana 2001). The area of ISAR - Karama is about 1000 ha with 300 ha for agriculture and 700 ha for grazing land and for the fodder crops like Pennisetum purpereum, Setaria sphacelata, Calliandra callothyrus, Sthylosanthes guianensis, Sthylosanhes scabra, Desmodium distortum, Mucunhas utilis.

  

Duration of the experiment

 

The duration of the study was 2 months: from August 15 at October 15, 2008. This period was covered by a dry season.

 

Experimental animals

 

Sixteen Ankole cows of the ISAR-Karama in period of lactation were selected based on their age and calving stage and similar weight (about 330 kg). They were initially subjected to a veterinary examination and verified to be healthy. The ticks were controlled by dipping tank in acaricide once per week and then the cows were assigned in 4 treatments at random and identified by ear tags. All the selected cows were in the 3rd calving and were in 1st month of lactation. In the ISAR- Karama research station milk yield of Ankole cows was estimated at 0.7 liters per day.

 

Feed

 

The basic feed was primarily made up by the natural pasture dominated by Brachiaria humidicolla, Hyparrhenia rufa and Cynodon dactylon. Apart from natural grazing, the mineral supplement was the salts mixed in the water. The supplement ration consisted of Stylosanthes scabra which was cultivated and collected in the field of forage seed multiplication of ISAR-Karama. This supplement ration was the object of the study. Prior to the experimentation 16 animals were fed on similar feed to accustom to a new environment and a new diet. During the period of experiment, each morning after milking, cows were led to the grazing land and remained there for 9 hours; the supplement ration was distributed in evening according to the level allotted to each group as it is indicated in table 1. The animals were watered during the day in herd and during the evening, the water was distributed ad libitum in a shed.


Table 1.  Experimental design

Number of treatments

Number of cows

 Feeds

SS0 (control)

4

Natural pasture (grazed voluntary by cows in the pasture)

SS10 (treatment)

4

Natural pasture +10% of Sthylosanthes Scabra DM

SS20 (treatment)

4

 Natural pasture + 20% of Sthylosanthes Scabra DM

SS30 (treatment)

4

Natural pasture + 30% of Sthylosanthes Scabra DM


For the mineral of supplement, the cows received salt mixed in water and during the experimentation, hygiene was ensured in a rigorous way.

 

Feed intake

 

To know feed intake of the various supplement rations used, the quantity of feed distributed and that refused were weighed daily and noted in a register. Thus the feed intake was obtained by making the difference between the distributed quantities of feed and that refused.

 

Milk production

 

To know the quantity of milk produced, the milking was carried out manually twice a day each morning and each evening, measured and recorded. To stimulate the letdown of the milk, calves suckled before milking and after milking for the period of the experiment. The milk consumed by calves was not measured because of lack of appropriate materials; neither did we take calf weight during the trial period.

 

Feed analysis

 

The nutrient of feed used in the experiment was analyzed to determine the quality of fodder which constituted the various levels of supplement ration and the natural pasture grazed by animals. These samples were taken randomly and were analyzed according to formula of AOAC (1990) for the dry matter (DM) using an oven at 105° C, neutral detergent fibers (NDF), acid detergent fiber (ADF), crude protein (CP), calcium was made by the atomic absorption spectrophotometer and phosphorus by colorimetry.

 

Statistical analysis

 

The relationship between feed consumed and supplement feed, milk production and supplement feed were plotted on bar charts. Box-cox plots were conducted for the two data sets. Data on milk yield was square root transformed y΄=sqrt (x+0.5) to stabilize the variances before the mixed model procedure of SAS was conducted. Means were separated with t-test of probabilities of the pair wise least square means. To estimate percent change in feeding animals with progressive concentrate at the rate of 1kg, the formula (1) was used.

Y= (C-B)/Cx 100 (1)

Where:

Y is percentage change if we fed the cow with additional B concentrate;

C= milk derived when used natural pasture; and

B milk derived when we use B (=1, 2, 3 kg) supplements.

In some of the cases that required ANOVA analyses, least significant differences (LSD) was used at p=0.05 in separating means. 

 

Results  

Feed analysis

 

Results of the pasture chemical analysis of the various samples taken in the natural pasture and the supplement ration (Stylosanthes scabra) were analyzed in a dry status. As one of the objectives of this study was to determine the content of nutritive value of Stylosanthes scabra, and that of the natural pasture, table 2 shows that the dry matter concentration of feed did not vary very much natural pasture had 96.26% of DM while Stylosanthes scabra had 96.23%.


Table 2.  Nutritive value of natural pasture and Stylosanthes scabra of Karama

Feed

DM, %

CP, %

ADF, %

NDF, %

P, %

Ca, %

CF, %

Ash, %

Natural pasture

96.26

6.1

51.8

71.3

0.12

0.5

37.5

8.35

S.scabra

96.23

21

28.8

37.9

0.24

1.21

31.95

8.88

Legend: DM: Dry Matter; ADF: Acid Detergent Fiber, CF: Crude fiber; NDF: Neutral Detergent Fiber; CP: Crude Protein; 
P:  Phosphorus,    Ca: Calcium


Stylosanthes scabra had about 3.5 times higher CP than the natural pasture that is explained by the fact that Stylosanthes scabra is a plant legume whereas the natural pasture is dominated by the grass herbs.

 

For phosphorus, the concentration varies between 0.12% DM for the natural pasture and 0.24% of DM for Stylosanthes scabra. Calcium levels concentrations were between 0.5% of DM for the natural pasture, and 1.21% of DM for Stylosanthes scabra. Finally the various concentrations in ash varied between 8.35% of DM for the natural pasture and 8.88% for Stylosanthes scabra.

 

Supplement ration consumption

 

During the experimentation, cows of SS10, SS20 and SS30 were fed supplement ration with the various rates (10, 20 and 30 % respectively) of Stylosanthes scabra and feed consumption is presented in table 3.


Table 3.  Daily supplement ration consumption

Period in

  Week  

Treatments

SS10

SS20

SS30

Kg (DM) /day

Kg (DM) /day

Kg (DM) /day

1

0.66

1.70

2.40

2

0.73

1.43

2.40

3

0.71

1.60

2.28

4

0.74

1.51

2.13

5

0.84

1.90

2.59

6

0.81

1.89

2.84

7

0.84

1.76

2.63

8

0.86

1.80

2.77

9

0.84

1.82

2.78


Thus the incorporation of Stylosanthes scabra leaf meal in the order of 10; 20 and 30% of DM in the ration led to a significant increase in feed intake (P< 0.05). Different letters indicate significantly different (p=0.05) by LSD (Figure 1).



Figure 1.  Quantity of supplement feed consumed by cows


This shows that Stylosanthes scabra, besides its considerable nutritive value, is also highly palatable to the cattle. Moreover, the incorporation of high CP feed as supplement is known to create conditions very favorable to the growth and the proliferation of the micro-organisms of the rumen which will attack and degrade the lignified elements of the ration, which increases the feed intake. The quantities of supplement offered and consumed show that the supplement was highly relished by the animals with hardly any refusals.

 

Milk production

 

Evolution of milk production

 

Mean milk outputs at various levels of Stylosanthes scabra leaf meal during the study as well as percent increase of milk production due to use of  Stylosanthes scabra have also been calculated and given on Table 4.


Table 4.  Least square means of milk yield of Ankole cows under different feed supplement

Supplementary feed, %

Milk yield/ day x, liters ±0.011

% change from Control

Control (SS0)

0.98 (0.47)

-

10

1.27 (1.10)

28.94*

20

1.40 (1.45)

42.32*

30

1.52 (1.80)

54.38*

x  Data from square root transformation. Actual means are in parenthesis.

* Significantly different (p≤0.03) by t-test of the pair wise probabilities from least square means


This table shows that the greatest output of milk was reached by the treatment which received 30% of the additional ration (54.4% higher than the control).The figure 2 shows a general progression of milk production as we increased the supplement. Lack of supplement gave very low yield throughout the nine weeks. Feeding Ankole cows with 1 kg of legume Stylosanthes scabra increased milk production by about 29% (P≤0.03).



Figure 2.  
Box-cox plot for milk distribution over feed supplement


The milk production was observed to increase with the level of supplementation.  SS0 produced 0.47 l of milk on average per week for duration of 9 weeks or 61 days because the last week lasted 5 days. It should also be realized that these cows were at the 3rd calving.

 

Analysis of the milk production

 

The analysis of milk production, ANOVA is presented on Figs 3. Distributed feed following the various levels of Stylosanthes scabra in the ration showed a significant difference (P< 0.05) for the milk production.



Figure 3.   Average milk production per feeding treatment


Indeed, the analyses carried out for the sample taken in the pasture showed that the pasture was relatively low in nutritive value with crude protein content of 6.1 % of DM.

 

Another factor which can explain the low milk production of the cows which consumed only the natural pasture can be the low digestibility of the fodder resources available, for the majority is the grasses, whereas principal herbs species composing this pasture are the grasses which are rich in CF and not very digestible lignin. Significant increase in the production in the cows which received a supplement of Stylosanthes scabra leaf meal from 10; 20 and 30%, can be explained by the quality of feed value of Stylosanthes scabra. According to the chemical analyses carried out, it has a content of crude protein of 21% of DM and a content of relatively low fiber, neutral detergent fiber 37.9% (NDF) and acid detergent fiber 28.8% of DM (ADF). Besides this difference related to the supplement ration used, other factors can also explain this low milk production of the cows which received only pasture. Again the experimentation was conducted during the dry season where almost the totality of the pasture was composed of dry grass of bad quality. The chemical analyses carried out for the natural pasture of the ISAR-Karama confirmed the low content of crude proteins and a high content of fiber.

 

The milk production of the three supplemented treatments also shows significant differences. This difference probably comes from the various feed levels which provide additional nutrients through the incremental supplement.

 

Discussion 

Feed analysis

 

It may be noted that the low content of crude protein was observed during dry period; it could have been different if wet seasons were also considered.  According to Rivière (1991) with share the degree of drying, other factors can influence the content of dry matter of feed; these are plant species, the age of the plant, the parts of the plant, the season and soil type.  Mandret (1990) confirms that the content of dry matter is low during the rainy season and increase slowly until the beginning of the dry season, and then it progresses rather quickly during the dry season to reach a level of 80 - 90% and that at the end of the dry season the cows have only fodder with high percentage of dry matter. According to Cheeke (2005) the fodder legumes are richer in protein than the grasses. The grasses  generally have a low content of proteins but which can be improved by the nitrogen fertilization if the harvest of fodder is carried out when plant is still young (Miller 1979). According to the same author, with great nitrogen fertilization, the content of CP of certain immature grass species can exceed 20% of the dry matter. Considering the fibrous components, the content of ADF of natural pasture is almost twice (51.8%) of that of Stylosanhes scabra. The same applies for NDF, (71.3%) for the pasture and 37.9% for Stylosanthes scabra. Here the high content NDF is indicative of maturity of the pasture. According to Jarrige and Peyraud (1993), the grasses are more lignified than fodder leguminous plants. Content of ADF and NDF which is presented in Stylosanthes scabra is also considerably lower than in the natural grass. Normally, the fraction of ADF is consisted of CF, the lignin and a large fraction of hemicelluloses and pectic substances. The results of the analysis of the chemical composition carried out on the natural pasture of ISAR-Karama confirm the low nutritive value of tropical grass species. The tropical grass species are known to be richer in the structural carbohydrates and low in crude protein, with a low rate of digestion of OM and DM.

 

As for Stylosanthes scabra, these Phosphorus contents and Calcium were not far from those cited by Toutain et al (1992) on Stylosanthes scabra in West Africa. The author found that Stylosanthes scabra present values equivalent to 0.29% for the Phosphorus and 1.32% of Calcium. These differences observed could be due to the various factors cited by various authors: Miller (1979) reports that the differences observed would be ascribable at the stage of maturity to harvest, the fertilization and the edaphic characteristics, the climate and the season, as to the changes which take place during the conservation and storage. For crude fiber, the concentration varied between 37.5% for the natural pasture and 31.95% for Stylosanthes scabra, these contents are almost similar. The values found do not diverge completely with those from Jarrige (1988). He found values of CF about 38% DM for the grass fodder and 35% DM for fodder legumes. Here the content of crude fiber of grass fodder remain higher than that of fodder legumes, which testifies the bad digestibility of grass fodder compared to fodder leguminous plants. The concentrations of ash as presented in table 5 do not diverge much from the value 8.14% DM for Stylosanthes scabra (Edye and Topark-Ngarm 1992).

 

Supplement ration consumption

 

The high feed intake can be due at the physiological state of the cows and their levels of production. The level of production has a clear influence in the cows with strong production which have large energy need (Rivière 1991). According to this author, the cows in lactation consume more than dried cows without considering the quantity of milk produced. The other factors influencing the feed intake; include the level of energy in the ration. If feed is sufficiently palatable to be easily consumed, the principal factor which determines their voluntary ingestion is the concentration in energy (Cheeke 2005). According to the same author, if the diet low in energy is used, the ingestion of feed is high, than that with a diet rich in energy. Ademond (1985) reports that the presence of fodder legumes in a ration increases the dry matter consumption and probably digestibility. It still affirmed that the animals receiving the highest level of supplement never refuse and present a consumption of 37.7% higher than that of the reference treatment subjected to the exclusively grass mode.

 

Another factor related to the chemical composition of the feed and which influences also the intake, is the fiber concentration. The content of acid detergent fiber (ADF) affects more ingestion than the fraction of detergent fiber neutral (NDF), which seriously does not limit ingestion Van Soest (1994), cited by Karugendo (1998). A supplement of digestible nitrogen matter can improve in a clear way the digestibility of fodder and increases the voluntary level of ingestion thus making it possible to significantly reduce the losses of weight of the animals and to even meet in certain case the needs for maintenance (Rivière 1991). The content of protein of feed also acts on their intake. According to Crowder et al (1982) quoted by Karugendo (1998), the weak ingestion observed on tropical fodder is due with low content of proteins of the mainly forage grass. Elliot and Signals (1963), and Minson et al (1976) quoted by Karugendo (1998), observed a reduction of ingestion when the content of protein went down in lower part from 70 g/kg from DM. However, the content of ADF exceeding 500-600 g/kg DM is reported to be an inhibiting limit of ingestion. The low nitrogen content of feed does not allow a sufficient proliferation of the bacteria of the rumen, resulting into fall of digestibility, and an obstruction of the rumen by not digested substances (Rivière 1991). However the age of fodder at harvest also influences the contents of the fiber in the forage which in turn makes them more resistant to digestion. According to Rutazihana (2003) more the plants age, more resist the microbial attack, but the cow needs a large and sufficient quantity of DM to maintain rumination. The fodder legumes used during the experimentation had not exceeded its state of harvest.

 

Milk production

 

Evolution of milk production

 

The peak of lactation was 0.74 l for the SS0, 1.24 l for the SS10, 1.57 l for the SS20 and finally 1.94 l for the SS30. It was observed that the milk production of the cows of these various treatments shows a higher milk production during the second and seventh week of the experiment, which does not diverge completely with the various authors. According to CPAQ (1981), the peak of lactation continues between the sixth and the eighth week after calving and finally decreases regularly. Craplet (1973) reported that the milk production increased during the first week following the calving and passes by a maximum the second and the sixth week then decreases more or less regularly until drying up. The principal factors of variation of the maximum daily milk production are: Initial production, feed, the number of milking per day as well as the interval between each milking.

 

Analysis of milk production

 

In practice the protein content which is equivalent to 16% in the ration is necessary for the majority of the cows in lactation consuming sufficient energy to satisfy the energy needs (Miller 1979). The energy expenditure of the production of milk is very important. They are a function of the secreted quantity and the composition of milk, which varies with the animal species, the breed, its aptitude and its degree of selection, and individuality (Rivière 1991). According to this author, for the same individual, this expenditure also depends on the age, the number of calving and the stage of lactation, as well as conditions of maintenance, feed and health of the animal.  Tropical fodder is in general richer in crude fiber less digestible and also lower in nutritive value. The low fiber concentration shows that Stylosanthes scabra has a considerable feed value. When the content of fiber is sufficiently low, the animals can satisfy their energy needs..

 

Indeed, the experimentation being conducted during the dry season where almost the totality of the pasture was composed of dry grass of bad quality. According to Cheeke (2005), the climatic factors are contributed to the reduction of the feed value of tropical grasses. Same author quoted by Jarrige  (1995), the high temperatures are at the environmental origin of the lignifications and the reduction of the digestibility of fodder. The daily milk production was on average of 1.12 l; 1.45 l and 1.83 l respectively for SS10, SS20 and SS30. These values approach with those obtained by Sibomana (1992) at the Station of ISAR-SONGA (from 1976 to 1982) on the cows Ankole 2.1 ± 0.1 kg per day of lactation. But Rubona happened to be in a relatively wet and cool environment. That shows that the contribution of the various levels of Stylosanthes scabra to the Ankole cows of the ISAR-Karama during lactation a positive effect on the milk production.

 

A part from the way in which we fed the cows for this period of lactation, the pre-calving feed can also intervene on the milk production. According to Uwituze (2002), the milk production depends on several factors where sufficient feed during pregnancy is important, and the quality of a feed is assessed through qualities of the required nutrients that it provides to the animal.

 

 The dairy females can be brought to a satisfactory condition, only if they are properly fed to meet the needs for growth, maintenance and pregnancy, before entering in lactation (Rivière 1991). According to this author, to maximize the milk production, two particular periods require attentive care, the last months of pregnancy and the beginning of lactation. Thus the fact that for the periods which precede the experimentation the cows fed only natural pasture, can explain the small quantity of milk. The way in which we made the milking can also justify the low milk production.

 

Conclusions

 

References 

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Received 9 January 2009; Accepted 26 January 2009; Published 1 May 2009

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