Supplementation of Grazing Dairy Cattle with Mulberry in the High Part of the Central Valley of Costa Rica

J. Benavides, I. Hernández, J. Ésquivel, J. Vasconcelos, J. González and E. Espinosa

CATIE, Turrialba, Costa Rica


Introduction

In Costa Rica, and in other tropical countries, there are many species of trees and shrubs with good forage characteristics thanks to the high nutrient of their forage and to their capacity of producing large amounts of biomass per unit area (Benavides, 1991; Reed, 1991). Due to these features, the use of their forage contributes to reduce the dependency on imported inputs to feed livestock (Romero et al., 1991).

Among woody forages, mulberry (Morus spp.) stands out, since its leaves have more than 20% crude protein (CP) and in vitro dry matter digestibility (IVDMD) between 70-80% (Benavides, 1994). Jegou et al. (1991) reported in vivo digestibility of 79% for DM and 89% for crude protein (CP). Under humid tropical conditions, with 4 harvests per year, 30 tons of DM per year, with 60% edible material, have been obtained. (Benavides et al., 1994). Oviedo (1995) stated that in association with Poró (Erythrina poeppigiana), mulberry can produce up to 7.2 tons of edible DM/ha just applying Poró's foliage as green manure.

Supplementing only with mulberry grazing dairy cows in the humid tropics, milk production did not differ significantly to that obtained with commercial concentrate supplementation (Oviedo, 1995). The objective of this experiment was to test the effect of different levels of concentrate substitution by mulberry on milk production with genetically superior cows.


Materials and Methods

The trial was conducted in a dairy farm at Coronado (San José, Costa Rica) at 1,471m above sea level, with annual mean temperature of 16.7°C and rainfall of 2,892mm (Chinchilla, 1987). Six Holstein cows with 2 or more calvings, an initial production of 18 kg of milk per day and 485kg of body weight were used. On a DM basis, the supplementation treatments were: commercial concentrate (T1); 35% mulberry and 65% concentrate (T2); and 65% mulberry and 35% concentrate (T3).

A Latin square, simple changeover, 3 x 3 design (Lucas, 1957) with 2 repetitions, was utilised. Each period lasted 21d (16 for adaptation and 5 for measurements). Supplementation was at the level of 1.3% of body weight on a DM basis at the beginning of each period.

Experimental animal grazed together with the rest of the milking cows on Kikuyo grass (Pennisetum clandestinum) which had patches of African Star grass (Cynodon nlemfuensis). Supplements offered and refused were measured individually and sampled for DM CP and in vitro DM digestibility determinations. Chromic oxide was used as marker for grazing intake estimations (Lascano, 1990). In addition to milk yield, intakes of DM and CP were measured and digestible energy (DE) calculated. Milk samples were analysed for fat, protein and total solids.


Results and Discussion

Mulberry used in this experiment had less CP compared to previous reports (Benavides, 1994; Benavides et al., 1994), who reported values over 20%. IVDMD and DE were high and comparable to reports from the same authors, 85.0 % y 3,75 Mcal/kg MS, respectively (Table 1).


Table 1.
Dry matter, crude protein, digestible energy and in vitro dry matter digestibility of feeds utilised for dairy cows.

Feed

DM (%)

CP (%)

IVDMD (%)

DE1 (Mcal/kg DM)

Kikuyo grass

23.0

8.0

65.0

2.9

Mulberry

25.4

16.1

80.0

3.5

Concentrate

91.5

17.7

85.0

3.7

1 DE = (IVDMD x 4,409)/100


The nutritional value of mulberry was better than Kikuyo grass and slightly better that the concentrate. It was also superior to other supplements traditionally used in dairies, such as sugar cane (4.9% CP; 2.9 Mcal DE/kg DM), bananas (4.8% CP; 3.1 Mcal DE/kg DM) and poultry manure (19.2% CP; 1.4 Mcal DE/kg DM) (Vargas, 1984).

Intakes of DM were adequate to animal type and production level. Although there were no significant differences among treatments, total intake declined with increasing levels of mulberry (Table 2), possible due to greater rumen fill of the bulky fresh mulberry. The intake was smaller to that reported by Oviedo (1995), of 3.8% of liveweight on DM basis when supplementing dairy cows under humid tropical conditions. Similar intakes of CP (1.9; 1.8 and 1.7 kg/d, for each substitution level, respectively) and DE (50.6; 48.0 and 44.3 Mcal/d, respectively) were observed.


Table 2.
Effect of mulberry supplementation on dry matter intake of grazing dairy cows.

Feed

Ratio Concentrate/Mulberry

100/0

60/40

25/75

 

DM, kg/animal/day

Concentrate

6.4

4.2

1.9

Mulberry

0

2.8

5.5

Kikuyo grass

9.3a

7.8ab

6.2b

Total

15.7

14.8

13.6

 

DM, % body weight

Concentrate

1.3

0.8

0.4

Mulberry

0

0.5

1.1

Kikuyo grass

1.7a

1.6ab

1.2b

Total

3.0

2.9

2.7


Despite slight decrease on intake, there were no significant differences (p < 0.05) on milk quality and yield due to supplement substitution (Table 3). Oviedo (1995) did not find significant differences on milk production and on composition when concentrate was replaced by mulberry (1.03% body weight on DM basis) in dairy cows in the humid tropics. There was no difference among treatments (p < 0.05), with Duncan test.


Table 3.
Milk yield and quality of dairy cows with different proportions of concentrate and mulberry.

Parameter

Ratio Concentrate/Mulberry

100/0

63/35

35/65

Milk, kg/animal/d

14.2

13.2

13.8

Milk protein, %

3.0

3.0

2.9

Milk fat, %

3.6

3.6

3.5

Total solids, %

12.7

12.6

12.5


Partial analysis of income and costs, considering only feeding costs, indicates a higher net income and better benefit/cost ratio per animal when mulberry replaced concentrates (Table 4).


Table 4.
Partial benefit/cost ratio per animal when supplementing with concentrate and/or mulberry on grazing dairy cows (In Costa Rican currency, colones2).

Item

Ratio Concentrate/Mulberry1

100/0

35/65

Concentrate

135,983

40,561

Cut & carry mulberry  

54,626

Manure spreading  

6,400

Depreciatión3  

6,010

Total costs

135,983

107,560

Total income

307,343

298,694

Net income

171,361

191,096

Profitability, %

56

64

1 Considering only feed costs.
2 December 1995.
3 Depreciation in 10 years the establishment cost for mulberry (Adapted from Ramos, 1996).


Conclusions and Recommendations

Substituting concentrates for mulberry in supplements for grazing dairy cows did not affect milk yield nor quality. At the same time, the use of mulberry can decrease feeding costs and the use of concentrates. It is advisable to carry out longer-term studies to establish the real potential for mulberry in complete lactations and to evaluate its effect on reproductive parameters.


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