24 - Productivity of ranch N'Dama cattle under trypanosomiasis risk

A. FERON, G.D.M. d'IETEREN, J. DURKIN, P. ITTY, O. KAKIESE, J.H.H. MAEHL, M. MULUNGO, S.M. NAGDA, R. W. PALING, M. PELO, J.M. RARIEYA, M. SHERIA, W. THORPE and J.C.M. TRAIL

Introduction
Results
N'Dama productivity in an African context
Conclusion
References

Introduction

Performance characters estimating the viability, reproduction, growth and milk-yield components of livestock production can be combined in productivity indices expressing total output and its efficiency in a single figure. Example indices are weight of weaner (and milk equivalent) produced per dam per year, or per unit weight of dam per year, or per unit metabolic weight of dam per year. By estimating the total output and its efficiency of production for specific breeds in different production environments, relative productivities can be assessed.

Within the ATLN, two current studies provide an interesting comparison of the productivity of N'Dama cattle at two levels of trypanosomiasis risk. The cattle at the two sites, which have similar agro-ecological conditions, receive the same ranch management, but at Kolo Ranch there is zero trypanosomiasis risk whereas at Mushie Ranch the risk is high. The estimates of N'Dama productivity at zero and high trypanosomiasis risk can, in turn, be compared with the productivities of N'Dama and Boran cattle estimated during long-term studies in other production situations.

Results

Productivity of N'Dama cattle at Kolo and Mushie ranches

N'Dama cow and calf viabilities parturition intervals, cow parturition and weaning weights and calf weaning weights were recorded during a three year period, January 1984 to December 1986. The management system was the same at Mushie and Kolo Ranches (Zaire) where trypanosomiasis risk was high and zero, respectively. Site details and a description of the management system have been presented by ILCA (1986) and are summarized in article 3 of these Proceedings. The performance recording followed the protocols of the ATLN (Murray et al., 1983). Results for individual performance traits and productivity indices of the N'Dama cattle at the two ranches are presented in Table 1.

Table 1. Productivity of ranch N'Dama under zero (Kolo) and high (Mushie) trypanosomiasis risk, 1984-1986.

Trait		Kolo (A)		Mushie (B)		Relative difference (%) A/B
		no.	Mean	no.	Mean
Calving interval (days)		401	426	193	493	+15.8
Calving percentage (%)			85.7		74.0	+15.8
Calf viability (%)			90.5		96.7	-6.4
Cow viability (%)			96.2		99.2	-3.0
Calf birth weight (kg)		374	22.2	405	19.9	+11.6
Calf weaning wt 8 mo (kg)		432	131	299	123	+6.5
Cow wt. postpartum (kg)		438	328	305	301	+9.0
Cow wt. at weaning (kg)		553	333	361	290	+14.8
Cow wt. change in lactation (g/d)		553	19	361	-24	-
Cow average body weight (kg)			331		296	+11.8
Cow productivitya
	Index 1 (kg)	101.6		88.0		+15.5
	Index 2 (kg)	30.7		29.7		+ 3.0
	Index 3 (kg)	147.2		138.4		+ 6.4
Herd productivityb
	Index 1 (kg)	97.7		87.4		+11.8
	Index 2 (kg)	29.6		29.6		+ 0
	Index 3 (kg)	141.6		137.3		+ 3.1

^a Index 1: Weight of 8-month weaner produced per cow per year
Index 2: Weight of 8-month weaner produced per 100 kg cow per year.
Index 3: Weight of 8-month weaner produced per 100 kg cow metabolic wt per year.
^b Cow productivity index x (cow viability %/100).

The average calving interval at Kolo was about two months (16%) shorter than at Mushie Ranch, the respective means being 426 and 493 days. The corresponding calculated calving percentages were 85.7% for Kolo and 74.0% for Mushie. Viability of pre-weaner calves and cows during the three-year study period was higher at Mushie, averaging 96.7 and 99.2%, respectively, as compared to 90.5 and 96.2% for the zero-risk site of Kolo. Viability figures for cows and calves are based on information from selection herds. The multiplication herds, which have many more cattle, are kept in much larger paddocks than selection herds, making it difficult to distinguish real deaths from those losses due to theft or uncontrolled changes from one herd to another. These results show that at the low trypanosomiasis risk site, Kolo, cow reproductive performance was superior but that cow and calf Liabilities were somewhat inferior.

Liveweight performance was better in Kolo than in Mushie for all liveweight characters presented in Table 1. The average body weight of N'Dama cows at Kolo Ranch was 331 kg, about 12% higher than in Mushie. Calf birth weights were also heavier at Kolo, 22.2 kg compared to 19.9 kg at Mushie. The cows at Kolo Ranch weaned calves with an average 8-month weight of 131 kg, 6.5% heavier than the weaners at Mushie (Table 1). The higher cow weights at Mushie may be due in part to a lack of culling and selection of the Mushie ranch population which is still being expanded.

Calving interval, calf viability and calf weaning weight were combined into a single figure (Index 1) to compare total output of N'Dama cows at the two sites (Table 1). With 102 kg weight of weaner calf produced per cow per year N'Dama, cows at Kolo were 15% more productive than the cows at Mushie, mainly due to the better reproductive performance at this zero risk site.

Production efficiency is expressed by relating total output back to the unit of cow body weight that has to be maintained (Indices 2 and 3). As the Kolo cows were heavier than the Mushie cows, their production efficiencies were only 3% (PI2) and 6% (PI3) better than those of the Mushie cows (Table 1).

The final productivity estimate was herd productivity calculated by multiplying cow productivity by cow viability (Table 1). Herd productivity was superior at the Kolo low-risk site when expressed on a per cow basis, but not when cow liveweight was included in the productivity index. Clearly trypanosomiasis risk was not a major factor affecting the productivity of N'Dama cows at these otherwise comparable ranches.

N'Dama productivity in an African context

The productivity of N'Dama cattle at Kolo and Mushie Ranches can be compared with the productivity levels of other cattle populations in Africa. An example of such a comparison is given in Table 2, using results from three other studies. The comparison is not of the relative advantage of one breed over another but rather a comparison of the productivity levels achieved in different production situations. Using the weight of weaner calf produced per 100 kg cow per year as the measure of production efficiency, it can be seen that Boran cattle raised in Kenya in the absence of trypanosomiasis attained a high level of productivity, 34.6 kg (Trail, 1985). This compares with the lower productivity at Mkwaja Ranch, 31.6 kg, where Boran were maintained under chemoprophylaxis in a high trypanosomiasis risk environment (Trail et al., 1985). Productivities of about 30 kg were also achieved by the N'Dama cattle at Kolo and Mushie. Particularly noteworthy is the performance of the N'Dama at the high risk Mushie site where no chemoprophylaxis is applied, yet productivity is only about 5% lower than that of the Boran maintained under chemoprophylaxis at Mkwaja (Table 2).

Table 2. Productivity of Boran and N'Dama cattle under ranch management at five sites In Africa.

		Kenya-Boran No trypanosomiasis risk No prophylaxis	Mkwaja-Tanzania Boran- High trypanosomiasis risk Prophylaxis	Kolo- Zaire N'Dama - No trypanosomiasis risk No prophylaxis	Mushie-Zaire N'Dama High trypanosomiasis risk No prophylaxis	West African N'Dama - Medium to high trypanosomiasis risk No prophylaxis
Reproduction
	Calving percentage	87.0	75.3	85.7	74.0	72.2
Viability
	Pre-weaner calves (%)	94.6	92.0	90.5	96.7	91.1
	Annual cow viability (%)	98.0	94.2	96.2	99.2	98.0
Birth weights
	Calf weaning weight at 8 months (kg)	174.0	133.5	131.0	123.0	90.4
	Cow mature body weight (kg)	414.0	293.0	330.5	295.5	256.0
Cow productivity
	Index 1	143.2	92.5	101.6	88.0	59.5
	Index 2	34.6	31.6	30.7	29.8	23.2
	Index 3	176.0	146.3	147.2	138.4	103.9
Herd productivity
	Index 1	140.3	87.1	97.7	87.3	58.3
	Index 2	33.9	29.8	29.6	29.6	22.7
	Index 3	172.5	137.5	141.6	137.3	101.8

Finally the last column of Table 2 presents the performance of N'Dama ranch cattle derived from an extensive survey on trypanotolerant livestock in West and Central Africa (ILCA, 1979). The productivity of these N'Dama populations was about 30% worse on average than that achieved by the N'Dama cattle exposed to high trypanosomiasis risk at Mushie Ranch, demonstrating the productive potential of this trypanotolerant breed when raised under good management conditions.

Conclusion

The similar productivities of N'Dama cattle at two ranches with contrasting trypanosomiasis risk levels, but which were otherwise comparable, confirms that at this level of risk trypanosomiasis is not a major factor affecting the productivity of this trypanotolerant breed. The productivity of the N'Dama on these Zaire ranches was comparable to that achieved by Boran cattle maintained under chemoprophylaxis in a high trypanosomiasis risk environment in Tanzania. Clearly an important study which should be carried out is a contemporary comparison of the productivities of Boran under chemoprophylaxis with N'Dama with no chemoprophylaxis in a high trypanosomiasis risk environment.

References

ILCA. 1979. Trypanotolerant Livestock in West and Central Africa: Monograph 2, International Livestock Centre for Africa, Addis Ababa.

ILCA. 1986. The ILCA/ILRAD Trypanotolerance Network: Situation Report, December 1985. Proceedings of a Network Meeting held at ILCA, Nairobi. International Livestock Centre for Africa, Addis Ababa.

Murray, M., J.C.M. Trail, D.A. Turner and Y. Wissocq. 1983. Livestock Productivity and Trypanotolerance. Network Training Manual Addis Ababa: ILCA.

Trail, J.C.M. 1985. Productivity of representative breeds of important cattle groups in Africa. In: Evaluation of Large Ruminants for the Tropics. J.W. Copland, ed. ACIAR proceedings No. 5: 101-105.

Trail, J.C.M., R. Sones, J.M.C. Jibbo, J. Durkin, D.E. Light and M. Murray. 1985. Productivity of Boron Cattle maintained by chemoprophylaxis under trypanosomiasis risk. Research Report 9, ILCA, Addis Ababa.