Pre- and post-weaning growth in Djallonké lambs

M Senou, P Tobada*, M Dahouda, C Adandédjan, V Aboki*, S Alimy**and P M Tondji**

Département de Production Animale, Faculté des Sciences Agronomiques, Campus Universitaire d’Abomey Calavi B.P. 526 Cotonou.
m_senou2002@yahoo.fr
* Département de Production Animale, Ecole Polytechnique d’Abomey Calavi, Campus Universitaire d’Abomey Calavi B.P. 526 Cotonou
** Direction de l’Elevage, Projet de développement de l’Elevage, Antenne de Bétécoucou, B.P. 2041 Cotonou

Abstract

The purpose of this study was to assess the pre- and post-weaning growth performances in Djallonké lambs. To achieve this goal, records on 1655 Djallonké lambs, which were reared from 2000 to 2005 at the Sheep Improvement Centre of Bétécoucou (CSO), were analysed using the GLM procedure. The mean estimate of the daily weight gain in the first month of the pre-weaning period (106.86g/d) was higher than that recorded in the second month of this period (61.98 g/d). The mean estimate of the pre-weaning daily weight gain (64.89 g/d) was greater than that of the post-weaning daily weight gain (50.17 g/d). The significance of non-genetic factors such as sex, year-season and type of birth of lambs, age at lambing and parity number of ewe on body weights and growth performances of lambs was also examined. 

Key words: body weights, daily weight gains, non-genetic factors

Croissance pré- et post- sevrage chez les agneaux Djallonké

Résumé

La présente étude avait pour but d’évaluer la croissance pré- et post-sevrage chez les agneaux Djallonké. Pour ce faire, les données enregistrées sur 1655 agneaux Djallonké élevés au Centre de Sélection Ovine de Bétécoucou pendant la période allant de 2000 à 2005 ont été analysées à l’aide de la procédure GLM. La moyenne estimée du gain moyen quotidien des agneaux pendant le premier mois de la  période pré-sevrage (106.86g/d) était supérieure à celle obtenue pendant le second mois de la même période (61.98 g/d). La moyenne estimée du gain moyen quotidien pré-sevrage (64.89 g/d) était supérieure à celle enregistrée chez les agneaux en phase de croissance post-sevrage (50.17 g/d). La signification des facteurs non génétiques tels que le sexe, la saison année et le type d’agnelage des agneaux ainsi que l’âge et le numéro de part des brebis sur les poids corporels à âges types et les performances de croissances, a été également étudiée. 

Mots clés: poids corporels, gains moyens quotidiens, facteurs non- génétique

Introduction

The Djallonké sheep are raised in a wide range of agro-climatic areas throughout the West and Central Africa (Wilson 1992). In Benin, they play an important role to the socio-economic well-being of a large human population in terms of nutrition, income and other intangible benefits (i.e. savings, cultural and religious purposes). In addition, they are endowed with tolerance to trypanosomiasis, resistance to parasitic diseases and hardiness to the hot humid tropics (Matthewman 1980; Bosso 2006). Therefore, most attempts to increase the productivity of sheep in West African countries focused on the Djallonké breed. Unfortunately, reference data on the pre- and post-weaning growth characteristics of this breed are rather disparate in the literature. In addition, few studies have elaborated on the non-genetic factors affecting productive traits in Djallonké sheep. The purpose of this work was firstly to provide mean estimates for pre- and post-weaning growth performances in Djallonké sheep and secondly to examine the effects of non-genetic factors such as sex and type of birth, age at first lambing and parity number, year and season of lambing on the traits under consideration. 

 

Material and methods 

Data source 

Analyses were performed on data provided by the Sheep Improvement Centre (CSO) of Bétécoucou, one of the research units of the Livestock Improvement Project (PDE) under the auspice of the Ministry of Agriculture, Livestock and Fishery (MAEP) of Benin, Africa. These data were collected on 1655 Djallonké lambs, progeny of 636 ewes, which were sired by 124 rams from year 2000 to 2005. The Frequencies of lambs born as single, twins, triplets or quadruplets throughout the observation period were 60.70%, 35.70% and 3.60% respectively. Further details on the data structure are given in Table 1.

Study area

The Sheep Improvement Centre of Bétécoucou is located in the “Zou Nord” department of central Benin, near the town of Dassa-Zoumè, between 7°45’ and 07°50’ North and 2°20’ and 2°27’ East and at 300m above see level. The climate is of soudano-guinean type with a dry season from November to March and a rainy season from April to October. The average rainfall is 1016 mm per year and the annual temperature ranges from 25°C to 30°C. The vegetation consists of wooded or shrubby savannas and grazed woodlands. Characteristic grass species of these areas are among others: Brachiaria mutica, Panicum sp, Hyparrhenia smithiana, Sorghostum bipennatum, Indigofera hirsuta, Pennisetum pedicellatum, Sporobolus pyramidalis, Andropogon gayanus.

Management and breeding

The management system of sheep reared at CSO is characterised as semi-intensive. Animals grazed from 0800h to 1730h on natural or improved pastures consisting of Panicum maximum C1, Brachiaria ruziziensis, Andropogon gayanus, Aeschynomene histrix and Cajanus cajan. Back from the pasture, they received a protein supplement of cotton seed cake of 400g and 300g for rams and ewes respectively and occasionally, on-farm by-products such as maize, rice straw and groundnut hay. Salt licks and water were provided ad libitum. Animals were housed at night and lambs were kept with their dams and remained with them until their weaning at three months of age. During the breeding period, one ram was assigned to a group of 20-25 ewes. Identity and pedigree information of animals, body weight at birth and weight measurements at monthly intervals were registered. The frequencies of lambing throughout the period of study were 19.74%, 17.46%, 17.86% and 44.94%, respectively in the early dry, the dry, the early wet and the wet season. All animals were treated against internal and external parasites. They were also vaccinated annually against “Peste des Petits Ruminants” (PPR) and brucellosis.

Data analysis and model fitting

Data on body weights (kg) at birth W0, at one (W1), two (W2), three (W3) and four month (W4) and at one year (W12) of age and average daily weight gains from birth to one month (WG_1), from one to two month (WG1_2) of age, from two month to weaning (WG2_3), from birth to weaning (WG_3), from weaning to four month (WG3_4) of age, from four month to one year (WG4_12) of age and from weaning to one year (WG3_12) of age, were analysed in this study. 

Results and discussion 

Overall means and standard deviations of the traits studied are given in Table 2.

Table 2.  Overall means of productive performances in Djallonké sheep
	Abbreviation	Unit	Sex
			male		female		Both sex
Body weight
at birth	W0	kg	1.934	0.355	1.872	0.359	1.903	0.35
at 30 days of age	W1	kg	5.386	1.275	4.920	1.261	5.141	1.285
at 60 days of age	W2	kg	7.265	1.901	6.724	1.619	6.987	1.776
at weaning (90 days of age)	W3	kg	10.299	1.889	10.058	1.589	10.174	1.143
at 120 days of age	W4	kg	12.294	2.370	11.877	2.152	12.080	2.268
at 1 year of age	W12	kg	24.053	3.562	23.901	3.614	23.971	3.581
Daily weight gain
from birth to 30 days of age	WG_1	g/d	113.426	37.849	100.958	38.543	106.864	38.598
from 30 to 60 days of age	WG1_2	g/d	62.160	35.604	61.822	32.021	61.986	33.694
from 60 to 90 days of age (weaning)	WG2_3	g/d	113.235	37.849	109.907	48.695	111.524	49.189
from birth to weaning	WG_3	g/d	67.025	37.643	62.779	36.961	64.890	37.336
from weaning to 120  days of age	WG3_4	g/d	46.331	10.894	45.548	12.088	45.968	11.437
from  120 days to 1 year of age	WG4_12	g/d	88.339	24.625	83.655	22.381	85.901	23.591
from  weaning  to 1 year of age	WG3_12	g/d	50.856	11.769	49.345	11.682	50.167	11.721

Results of the analyses of variance (AOV) are presented in Table 3 and subsequent least squares means comparison are given in Table 4 and 5 respectively for pre- and post- weaning growth traits.

The average value of 1.90 kg for W0, found in the present study, compares well with those reported by Charray (1986) and Armbruster et al (1991) in Ivory Cost (1.90 kg) and by Gbégo and Van den Broek (1992) and Gbangboche et al (2006) in Benin (1.84-1.85 kg). Slightly higher values (2.01-2.25 kg) for W0 in Djallonké lambs were found by Symoens and Hardouin (1988) and Vallerand and Branckaert (1975) in Cameroon, by Yapi-Gnaoré et al (1997) in Ivory Cost and by Bosso (2006) in The Gambia; while comparative lower values (1.44-1.75 kg) were reported for this trait by Amégée (1984) and Abassa et al (1992) in Togo, by Fall et al (1983) in Senegal, by Poivey et al (1982) in Ivory Cost and by London and Weniger (1995) in Ghana. The average weaning weight (W3) recorded in the present study (10.17 kg) is consistent with that of 10.20 kg reported by Armbruster et al (1991). Poivey et al (1982), Charray (1986), Gbégo and Van den Broek (1992) and Gbangboche et al (2006) however reported lower values (6.80-9.8kg) for W3. A much higher value (11.8 kg) for W3 was found by Symoens and Hardouin (1988) for Djallonké lambs raised under improved management conditions. W3 is an indicator for both pre-weaning growth potential of lambs and maternal aptitude of their dams. Animals recorded in the present study appear to have a greater growth potential than those involved in most of published studies on the Djallonké sheep breed, except the study of Symoens and Hardouin (1988). It should be mentioned that the study reported by the latter author was designed to assess the impact of enhanced environmental and managerial conditions (housing, feeding at higher concentrate level, mineral supplementation, health care among other factors).

The W12 obtained in the present study (23.97 kg) also surpasses those reported by Gbégo and van den Broek (1992), Fall et al (1983) and Bosso (2006) by 27%, 44% and 62% respectively.

The daily weight gain in the first month of the pre-weaning period (106.86g/d) is higher than that obtained in the second month of this period (61.98 g/d). Based on the work of Doney and Munro (1962), growth from birth to 60 days depends on the mothering ability of the dams and the postnatal environment. Results from the present study suggest however that the maternal effect on the growth performance of lambs is more pronounced in the first month than it is in the second month post partum. These results are in accordance with those reported by Poivey et al (1982). This author found a WG_1 of 92.13 g/d and a WG1_2 of 72.13 g/d. Similar results were also found by Amégée (1984) with a WG_1 of 82.76 g/d and a WG1_2 of 75.18 g/d. In the present study, the pre-weaning daily weight gain (WG_3) of 64.89 g/d is on average greater than the post-weaning daily weight gain (WG3_12) which was 50.17 g/d). Similar results were also found by Gbégo and Van den Broek (1992), Poivey et al (1982) and Gbangboche et al (2006). As mentioned by El-Fadili et al (2000), the decrease of the average daily weight gain with advancing age of lambs could be explained by the decrease of maternal effect of dams on the growth performance of their progeny.

Non-genetic factors affecting body weight and growth performance of lambs

Year - season of birth of lambs

AOV revealed the significance (p<0.001) of the combined year-season effect on body weights at birth (W0), at weaning (W3), at four month (W4) and at one year (W12) of age (Table 3). Poivey et al (1982) however found no significant effect of year of birth on W0 in Djallonké sheep. London and Weniger (1995) also found no significant effect of season of parturition on W0. The significance of year and season effects on variation in body weights and weight gains in lambs of tropical breeds is well documented in the literature (Ebangi et al 1996; London and Weniger 1996; Yapi-Gnaoré et al 1997; Gbangboche et al 2006) and may be attributed to temporal variation in environmental factors, e.g. availability and quality of feedstuff, disease challenge, temperature stress as well as managerial practice. It should be mentioned that most authors referred to above included in their model each of the effects year and season separately. In the present study, the year and season effects were combined into a single effect called year-season effect in order to accommodate to the high degree of confounding of both effects.  

Sex of lamb

As shown in Table 3, differences observed in W0, W1, W2 and W12 were not significant. As for birth weight, London and Weniger (1995) also found no significant sex effect on this trait. A significant effect of sex on W0 in Djallonké lambs was however reported by Taiwo et al (1982), Wilson (1987), Yapi-Gnaoré et al (1997) and Gbangboche et al (2006). But such a result is questionable, if the type of birth is to be considered. In other words, a single born female lamb may be heavier in birth weight than a female born to triplet. Significant effects of sex (p<0.05) were found in the current study, only on body weights from weaning (90 days) to 120 days of age (W3, W4) and for daily weight gains from 60 days of age to weaning and from weaning to 120 days of age (W2_3, WG3_4) (Table 3). These results support those of Poivey (1982), according to which, differences in body weights and daily weight gains in males and females were more pronounced after weaning. 

Type of birth

In the present study a significant effect of the type of birth was found (p<0.05) on all body weights and growth traits, except on the daily weight gains from 120 days to one year of age (WG4_12). These results are in accordance with those of Fall et al (1983), Poivey et al (1982), Amégée (1984), Armbruster et al (1991), Wilson (1987), Ebangi et al (1996) and Yapi-Gnaoré et al (1997). The inverse relationship observed in the present study between birth weight and number of lambs born per ewe (Table 3) was also recognized by Poivey et al (1982), London and Weniger (1995) and Gbangboche (2006). In the present study, single born lambs were favoured by their higher birth weight and significant faster growth rate in comparison to those from multiple births within the first 30 days of age (Table 4). From 30 to 60 days of age, the triplets and quadruplets grew significantly faster as twin born lambs. But differences between triplet or quadruplet and single born lambs regarding daily weight gain were not significant.  From 60 to 90 days and from 90 days to 120 days of age, the multiple born lambs grew significantly faster than single born lambs. But from 120 days to one year of age, there were no more significant growth differences between single and multiple born lambs (Table 4). Owing to this catching-up effect (Poivey et al, 1982), the curves of the means of estimates of body weights by age followed the same pattern for four month aged lambs, irrespective of their type of birth (Figure 1).

Age at lambing and parity number of ewe

Parity number affected significantly (p<0.05) W0 and WG2_3 (Table 3). As shown in Figure 2, the birth weights of lambs increase with increasing parity number of dams, reaching a peak and decreasing thereafter.

This observation may be associated to the maturity of the milk secretion system and aging of dams. In the present study, the positive effect of the maturity of dams on the birth weight of their progeny decline after the sixth parity (Figure 2).

The significance of ewe parity number on birth weight and growth performance of lambs was also recognized by Wilson (1987), Poivey et al (1982), London and Weniger (1995) and Ebangi et al (1996). The age of ewe affected W0 and WG2_3 in its linear and quadratic components (Table 3). A linear trend between birth weight of Djallonké lambs and body weight of dams was also found by Wilson (1987). 

Conclusion 

• Estimates of the means of the productive traits studied might support the planning, the monitoring and evaluation of breeding projects in Djallonké sheep.

  
  

• Furthermore, results from significance test of non-genetic factors suggest which of them are to be corrected for, if mixed model approaches such as BLUP are to be used for breeding value evaluation in Djallonké sheep.

Acknowledgements 

The authors are grateful to the "Projet de Développement de l’Elevage" (PDE/DE/MAEP) for providing the data used in this study and for the help and co-operation received in the course of this work.

References 

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Received 25 September 2008; Accepted 11 February 2009; Published 1 June 2009

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