The productivity of Small East African sheep and goats in Malawi

J. W. Banda

University of Malawi, Bunda College of Agriculture
P. O. Box 219, Lilongwe, Malawi

Abstract
Introduction
Materials and methods
Results and discussion
References

Abstract

The total and additional biological productivity of local (LL) and Boer (BB) goats and their crosses (BL) and of the local (LL) and Dorper (DD) sheep and their crosses (DL) were estimated over two kidding seasons at the Lifidzi Goat Breeding Centre, Salima, Central Malawi.

The average 12-weeks milk production was 79.0 ( ± 2.0 kg) in goats and 54.5 ( ± 1.3 kg) in sheep. The difference was significant (P<0.001). The yields of LL (73.7 ± 2.5 kg) and BB (78.3 ± 3.8 kg) were similar, but lower (P<0.001) than those of BL does (85.1 ± 2.3 kg). LL, DL and DD ewes produced 41.4 ± 1.8, 53.5 ± 1.6 and 68.7 ± 2.1 kg milk respectively and the differences among these genotypes were significant (P<0.001).

The average daily gain (ADO) from birth to 17 weeks of age was 87.0 ( ± 3.5 g) for kids and 128.9 ( ± 2.8 g) for lambs. Milk conversion was 15.6 and 11.9 kg milk/kg liveweight gain in kids and lambs, respectively. The average mortality was 18.9 and 5.3% in kids and lambs respectively.

The total apparent biological productivity indices represented by indices I, II and III were, respectively, 16.6, 0.47 and 1.15 kg for goats. For sheep, the corresponding values were 24.9, 0.80 and 1.89 kg. Additional apparent biological productivity represented by indices IV, V and VI were 7.08, 0.204 and 0.495 kg respectively for goats and 6.13, 0.197 and 0.464 kg for sheep. These results suggest that although the two species differ in milk production, the difference in production is not substantial.

Productivité des moutons et des chèvres de l'Afrique de l'Est au Malawi

Résumé

Les productivités biologiques totale et complémentaire de chèvres de races locale (LL) et Boer (BB) et des produits de leur croisement (BL), ainsi que de moutons locaux (LL) et Dorper (DD) et des produits de leur croisement (DL) ont été déterminées sur deux saisons de mise-bas au Centre d'élevage caprin de Lifidzi à Salima (centre du Malawi).

La production de lait sur une période de 12 semaines était en moyenne de 79,0 kg ( ± 2,0 kg) chez la chèvre et de 54,5 kg ( ± 1,3 kg) chez la brebis. La différence était significative (P<0,001). Les chèvres LL et BB produisaient du lait en quantités à peu près égales (73,7 ± 2,5 kg et 78,3 ± 3,8 kg respectivement) mais inférieures aux quantités produites par les mères BL (85,1 ± 2,3 kg). Les brebis LL, DL et DD produisaient respectivement 41,4 ± 1,8, 53,5 ± 1,6 et 68,7 ± 2,1 kg de lait et les différences entre génotypes étaient significatives (P<0.001,).

Le gain moyen quotidien de la naissance a l'âge de 17 semaines était de 87,0 ( ± 3,5 g) chez les chevreaux et de 128,9 ( ± 2,8 g) chez les agneaux. Les taux de conversion étaient respectivement de 15,6 et 11,9 kg de lait/kg de poids vif La mortalité des chevreaux était en moyenne de 18,9%, celle des agneaux de 5,3%.

Les indices I, II et III, qui représentent la productivité biologique apparente totale, étaient respectivement de 16,6, 0,47 et 1,15 kg pour les chèvres et de 24,9, 0,80 et 1,89 kg pour les moutons. Les indices IV, V et VI, qui représentent la productivité biologique apparente complémentaire, étaient respectivement de 7,08, 0,204 et 0,495 kg pour les chèvres et de 6,13, 0,197 et 0, 464 kg pour les moutons. Il découle de ces résultats que les deux espèces différent sur le plan de la production de lait mais que cette différence n'est pas importante.

Introduction

From 20-60% of the variation in weaning weight of kids and lambs in the tropics and sub-tropics is accounted for by the variation in the amount of milk produced by the dams or the amount suckled by lambs and kids (Peart, 1982). Genotypes differ in this ability. Mortality prior to weaning, lambing/kidding interval, weight and milk production of the dams are major factors influencing the productivity of sheep and goats. These individual variables can be combined into indices termed either total apparent biological productivity or additional apparent biological productivity. These indices can then be used to compare the reproductive efficiency in species and/or populations which differ in mature size.

In Malawi, there is little information on the productivity of sheep and goats. The objectives of this study were to evaluate the present and potential milk production capacity of sheep and goats in Malawi and calculate and compare their apparent biological productivity.

Materials and methods

The study was carried out at the Lifidzi Goat Breeding Centre near Salima in Central Malawi at an altitude of 600 metres above sea level.

Data were collected from 11 local (LL), four Boer (BB) and 10 crossbred (BL) does end from 12 local (LL), 15 Dorper (DD) and 17 crossbred (DL) ewes in the dry season. Almost 80% of the experimental animals were used again in the subsequent rainy season. Milk yield was estimated by the suckling, handmilking and oxytocin + handmilking techniques on three different days in each of the 12 weeks after parturition. The oxytocin dose was 10 i.u. (1 ml) per animal. All these factors were arranged in a 2 x 3 x 2 x 3 factorial design.

For the dry season trials, does and ewes were mated to bucks and rams of their own genotype between December 1987 and February 1988. Milking commenced in May 1988. For the rainy season trials, the same animals were mated to a Boer buck and Dorper ram between September and October 1988. Milking started in January 1989. All animals grazed natural pastures. During milking only, animals on the trial received a concentrate mixture composed of 91% maize bran, 8% dried leucaena leaves and 1% common salt (NaCl) at a rate of 300 g per animal/day. The concentrate mixture contained 12.7% crude protein and 19.7 MJ gross energy (GE) or about 13 MJ metabolisable energy (ME)/kg dry matter (DM).

The milk yield of each animal was measured every week for the 12 weeks of lactation. On test days, kids were separated from their dams for two four-hour periods. For the suckling method, the young were weighed before and after suckling. The difference in weight was taken as the milk production during the separation period. For the hand-milking technique, animals were milked out at 1100 and 1500 h. The daily milk yield for both methods was calculated by summing up the two four-hourly yields and multiplying the results by three. The oxytocin technique (oxytocin + hand-milking) was done by milking the animals after injection of 10 i.u. of oxytocin at 1100 h. The amount of milk obtained during this single separation period was multiplied by six to obtain daily milk production.

Liveweights of the kids and lambs were taken at birth and at weekly intervals until weaning at 17 weeks. Records of litter sizes at birth and at weaning, mortalities of kids and lambs, kidding/lambing interval and dam weights were kept and used in the calculation of the biological productivity indices of the dams. The indices in the two species were calculated in two ways as indicated below:

Method 1

Index I	= Weight of weaned lamb or kid produced per dam per year (kg)
	= litter weight at 120 days (weaning age) X 365/subsequent lambing or kidding interval
Index II	= Weight of lamb or kid/liveweight of dam per year (kg)
	= Index I/dam post-partum weight (kg)
Index III	= Weight of lamb or kid produced/dam metabolic weight per year (kg)
	= Index I/dam post-partum weight 0.75

Method 2

Index IV	= Additional lamb or kid weight produced/dam per year (kg)
	= Milk yield X milk conversion rate X litter size
Index V	= Additional lamb or kid weight produced/kg liveweight of the dam
	= Index IV/dam post-partum weight (kg)
Index VI	= Additional lamb or kid weight produced/dam's metabolic weight (kg)
	= Index IV/dam post-partum weight 0.75

Dependent variables were milk yields, liveweights and ADG of kids and lambs. Fixed least-squares models described by Harvey (1977) for use on date with unequal subclass numbers were used for analysing the milk yields of dams and the liveweights and ADG of kids and lambs. No statistical analysis was conducted on the productivity indices calculated.

Results and discussion

Milk yield

The total milk production of goats was 45% higher than that of sheep (Table 1). Based on mean liveweight, goats produced 26.0 g milk/day per kg body weight or 63.0 g/day per kg^0.75. Sheep produced only 19.0 g milk/day per kg body weight or 45.0 g milk/day per kg^0.75. Economides (1986) compared Damascus goats and Chios sheep kept under the same feeding and management practices and obtained 11-42% more milk from goats than from sheep. Previous reviews and reports have compared goats, sheep and other ruminants for milk production. It has been concluded that goats produce more milk for the following reasons: better feed utilisation efficiency; higher lactation persistency; mammary tissue comprising a greater proportion of the body weight; and a more pronounced milk ejection reflex (Devendra, 1975; Morand-Fehr and Sauvant, 1978; Devendra, 1980; Devendra, 1981; Economides, 1986; Jenness, 1986; Zometa et al, 1987).

Table 1. Least squares means (kg), standard errors (se) and t-values for total milk yields of sheep and goats.

Main effect		Sheep				Goats				t-value
Sub class		No. obs.	Mean	±	se	No. obs.	Mean	±	se	Sheep vs Goats
Overall		250	54.5	1.30		163	79.0	2.00		-12.24***
Genotype
	Local	84	41.1a	1.80		65	73.7a	2.50		-10.48***
	Crosses	102	53.5b	1.60		76	85.1b	2.30		-11.28***
	Exotic	64	68.7c	2.10		22	78.3a	3.80		-2.21**

abc = means within variable groups bearing different superscripts differ significantly (P<0.05).
*** P< 0.001; ** P<0.05.
No. obs. = number of observations.

In this study, the higher initial milk yield (56.8%) and higher persistency (6.3%) in goats may have led to higher milk production than sheep. Although not measured, the size of the udders of goats in relation to their body weight as explained by Jenness (1986) may also have contributed to this difference. The absence of total feed intake data limits a discussion on the efficiency of milk production with respect to nutrition. This implies that there is a need to conduct more research in order to ascertain whether the differences could also have been partly due to feed utilisation efficiency.

The milk yields of sheep and goats used in this study are much lower than those recorded for these species in temperate, Indian and Mediterranean areas for recognised dairy, meat and general-purpose breeds. The concentration of constituents in their milk is, however, higher than that for the temperate breeds, but comparable to that for other tropical/subtropical breeds as a consequence of lower milk yield (Devendra and Burns, 1983; Gatenby, 1986).

From local to exotic sheep, there was a linear increase in milk yield while from local to exotic goats, there was a quadratic response with Boer x local crossbreds producing the highest yields, indicating 12% heterosis. Indications are that crossbreeding improves milk production in the local small ruminant species.

Weight gains and milk conversion rates

A summary of the liveweights, liveweight gains and milk conversion efficiency of kids and lambs is shown in Table 2. It is quite clear that lambs weighed more and grew faster than kids, irrespective of the stage of growth. This has been demonstrated previously (Economides, 1986; Wilson, 1986). Consequently, kids required 15.6 litres of milk for each additional kg of weight gained while lambs required only 12.0 litres.

Economides (1986) further observed that lambs consumed more solid feed and started doing so at an earlier age than kids. It is not clear whether the differences observed in the present study are due to differences in solid food intake, as no data were collected on this aspect. Generally, the results suggest that it would be more efficient to rear lambs than kids for meat production, especially during the first four weeks. However, valid conclusions can only be reached when other factors, e.g. solid feed intake, costs of treatments, mortality and reproduction are considered.

Table 2. Live weights and liveweight gains of lambs and kids from birth to six months of age (two months post-weaning) and their pre-weaning milk conversion efficiency.

		Lambs(L)			Kids(K)			t-value
		Mean	±	se	Mean	±	se	Lambs vs Kids
No. Of observations		236			152
Birth weight (kg)		3.19	0.05		2.77	0.08		4.45***
12-week weight (kg)		14.07	0.25		10.07	0.32		9.85***
17 week weight (kg)		18.52	0.32		12.99	0.41		10.63***
Gain (g/day)
	Birth-12 weeks	129.4	2.8		87.9	3.2		9.76***
	12-17 weeks	128.5	3.5		87.0	3.6		8.27***
	Overall	128.9	2.8		87.0	3.5		9.35***
Milk conversion (kg gain/litre milk)
	1-12 weeks	0.084	0.008		0.064	0.011		1.47 ns
	Weeks 1-4	0.098	0.008		0.049	0.012		1.66 **
	Weeks 5-8	0.076	0.009		0.068	0.014		0.30 ns
	Weeks 9-12	0.058	0.012		0.059	0.012		0.06 ns

*** P<0.001; ns = not significant; ** P<0.05.

Table 3. The apparent total biological productivity of sheep and goats.

Parameters		Goats	Sheep	Goat vs. Sheep (%)
Offspring weaning weight (kg)		12.99	18.52	-30.0
Litter size at weaning		1.05	0.98	7.1
Total weaning weight (kg)		12.41	18.15	-31.6
Kidding/lambing interval (days)		275.6	266.5	3.4
Darn weight (kg)		34.7	31.1	11.6
Dam weight (kg0.75)		14.3	13.2	8.4
Productivity indices (kg)
	Index I	16.4	24.9	-34.2
	Index II	0.47	0.80	-51.2
	Index III	1.15	1.89	-39.2

Dam productivity

The measurements of biological productivity as total weight of offspring at weaning per female per year (Index I), per kg dam weight per year (Index II) and per kg dam weight 0.75 per year (Index II) in both sheep and goats are given in Table 3. Productivity was highest in LL does and lowest in BB does, with that in BL does being closer to that of LL does.

The LL ewes outperformed the DL and DD ewes, with the last showing the lowest performance. The ewes were superior to does overall.

A summary of the additional apparent productivity of the two species based on milk production and milk conversion efficiency by the offspring as well as weight of the dams is presented in Table 4.

The additional productivity per female was higher in goats than in sheep. The difference was largely due to the milk yield level of the does and the larger litter size per annum (Table 4). When the metabolic body weight of the dam was considered, the difference between the two species narrowed. This was due to the lower weight of the sheep.

Thus, although the two species differ in milk production and annual litter size, the difference in overall production is not very great.

Table 4. The apparent additional biological productivity of sheep and goats based on milk conversion.

Parameters		Sheep	± se	Goats	± se	(%) Goats vs Sheep
No. of observations		236		152
Milk yield (kg)		54.5	1.3	79.0	0.2	45.0
Milk conversion rate (lambs & kids)		0.084	0.008	0.064	0.011	-23.8
Dam weight (kg)		31.1	0.2	34.7	0.3	11.6
Dam weight (kg0.75)		13.2		14.3		8.3
Litter per annum		1.34			1.40	4.5
Productivity indices (kg)
	per female	6.13			7.08	15.5
	per kg dam weight	0.197			0.204	3.6
	per kg dam weight0.75	0.464			0.495	6.7

References

Devendra C.1975. Biological efficiency of milk production in dairy goats. World Review of Animal Production 11:46-53.

Devendra C. 1980. Milk production in goats compared to buffalo and cattle in the humid tropics. Journal of Dairy Science 63:1755-1767.

Devendra C. 1981. Potential of sheep and goats in less developed countries. Journal of Animal Science 51:461-473.

Devendra C and Burns M. 1983. Goat production in the tropics. 2nd ed. Commonwealth Agricultural Bureaux, Farnham Royal, UK. pp. 64 73.

Economides S. 1986. Comparative studies of sheep and goats: milk yield and composition and growth rate of lambs and kids. Journal of Agricultural Science (Cambridge) 106:477-484.

Gatenby R M. 1986. Sheep production in the tropics and subtropics. 1st ed. Longman, London, UK. pp. 202-225.

Harvey W R. 1977. User's guide for LSML76. Mixed model least-squares maximum likelihood computer program. Ohio State University, Columbus, Ohio, US. (Mimeograph).

Jenness R. 1986. Lactational performance of various mammalian species. Symposium: Species Variation in Mammary Gland Function. Journal of Dairy Science 69:869-885.

Morand-Fehr P and Sauvant D. 1978. Nutrition and optimum performance of dairy goats. Livestock Production Science 5:203-213.

Peart J N.1982. Lactation of suckling ewes and does. In: Coop I E (ed), Sheep and goat production. World Animal Science C 1. Elsevier, Amsterdam, The Netherlands. pp. 119-134.

Wilson R T. 1986. Livestock production in Central Mali: Long-term studies on cattle and small ruminants in the agropastoral system. ILCA Research Report 14. ILCA (International Livestock Centre for Africa), Addis Ababa, Ethiopia. pp. 82-95.

Zometa C A, Cunha M G G, Shelton M, Sousa W H and Leite P R M. 1987. Comparative lactation performance on native goats and cows in semi-arid northeastern Brazil. In: Santana O P. Gabriel da Silva H and Foote W C (eds), Proceedings of the IV International Conference on Goats. Volume II. Departamento de Defusäo de Technologia-DDT, Brasilia, Brazil, 8-13 March 1987. p. 1547. (Abstract no. 346).