Abstract
Résumé
Introduction
Materials and methods
Results and discussion
References
I.K. Odubote
Department of Animal Science
Faculty of Agriculture
Obafemi Awolowo University, Ile-Ife,
Nigeria
Six hundred and ten lambing records of the West African Dwarf sheep kept in the sheep unit of the Obafemi Awolowo University Teaching and Research Farm, Ile-Ife, Nigeria from 1981-1987 were analysed. Year of birth significantly influenced birthweight and litter birthweight (P<0.001) and type of birth (P<0.01). Males were heavier (P<0.01) than the females. Lambs delivered in the dry season were lighter (P<0.001) than their wet season counterpart. Litter composition had significant effect on birthweight (P<0.05) and litter birthweight (P<0.01).
Male:female ratio was equal while the ratio of single:twin:triplet was 68:31:1. Mean birthweight, litter birthweight and litter size at birth were 2.15 ± 0.46 kg, 4.06 ± 0.77 kg and 1.33 ± 0.41 kg, respectively. Significant correlation coefficients of-0.62 and +0.87 (P<0.001) were obtained when type of birth was correlated with birthweight and litter birthweight, respectively. Adjustment factors for the significant effects were provided.
L'analyse de six cent dix agnelages enregistrés de 1981 à 1987 sur le troupeau de moutons Djallonké élevés à la ferme expérimentale de l'Université Obafemi Awolowo d'Ile Ife (Nigéria) est rapportée ici.
L'année de la naissance eut un effet significatif sur le poids de l'agneau, celui de la portée (P<0,001), ainsi que sur le type de naissance (P<0,01). Le poids des mâles fut supérieur (P<0,01) à celui des femelles, tandis que celui des agneaux nés pendant la saison sèche était plus léger (P<0,001) que leurs homologues nés pendant la saison humide. La composition par sexe de la portée avait un effet significatif sur le poids à la naissance (P<0,05) et sur celui de ['ensemble de la portée (P<0,01).
La proportion des sexes était égale à 1, mats, sur l'ensemble de la période considérée, on a dénombré 68 naissances simples, 31 naissances gémellaires et 1 triplet. Le poids moyen à la naissance, celui de ['ensemble de la portée à la naissance et la taille moyenne de la portée furent respectivement de 2,15 ± 0,46 kg, 4,06 ± 0, 77 kg et 1,33 ± 0,41. Une corrélation significative entre le type de naissance d'une part et d'autre part, le poids à la naissance (-0,62) et le poids de l'ensemble de la portée (+0,87) a été démontrée. Des facteurs de correction vent proposés en ce qui concerne les effets significatifs.
Small ruminants have for so long taken the back seat in the livestock development programme of Nigeria. However, with current awareness and interest, it is necessary that basic information on production traits and factors that affect them should be documented. Fall et al (1982) reported that birthweight in Djallonke sheep of Senegal is significantly affected by year and season of birth, type of birth, sex and parity. There is paucity of such evaluation for the West African Dwarf (WAD) sheep in the humid tropics of Nigeria. This study was thus undertaken to evaluate the effects of these factors on lambing related parameters in WAD sheep.
The WAD sheep used in this study are adequately described by Adu and Ngere (1979). They were housed in barns measuring 22 m x 4 m on a cemented floor. The animals were grouped depending on their status: lactating, pregnant or growing. Each pen was provided with two receptacles for feeding concentrate and watering. A groove filled with water was made round each barn to prevent ant problem. The barns were cleaned daily.
The animals were put on pasture (Giant Stargrass in pure stand) at about 7.30 a.m. and returned to the barns in the afternoon. They were then fed ad libitum a supplementary diet consisting of 50% corn, 7.5% groundnut cake, 10% brewers' dry grain, 30% rice bran, 1.5% dicalcium phosphate, 0.5% Agricare and 0.5% salt.
Panicum maximum and Gliricidia sepium were also provided ad libitum in the pens. The sheep were treated for ectoparasites, drenched once every three months and given other veterinary attention when the need arose. The animals lambed all year round. Birthweights were recorded within 12 hours after birth. Stillbirth or deaths immediately after birth were disposed of after post-mortem examination. Such lambing records were discarded for this analysis. Lambs were examined for any defect at birth and to maturity.
Records of the birthweight, litter birthweight and litter size at birth were analysed for effects of year of birth, season of birth (dry season - November to March; rainy season - April to October) type of birth, litter composition and sex using the General Linear Model (SAS, 1982). Differences between means were tested by Duncan's New Multiple Range Test (Steel and Torrie, 1980). From least squares constants, weights of lamb were adjusted to the equivalent of a single, male lamb born in the wet season. Correlations between type of birth and birthweights were also computed.
The least squares means for birthweight, litter birthweight and litter size at birth are given in Table 1. The least squares constants and adjustment factors for birthweight and litter birthweight are presented in Table 2. Male:female ratio was equal while the ratio of single:twin:triplet was 68:31:1.
Significant (P<0.001) correlation coefficients of -0.62 and 0.87 were obtained when type of birth was correlated with birthweight and litter birthweight, respectively.
The overall average birthweight of 2.15±0.46 kg obtained in this present study was found to be higher than the 1.8 kg reported by ILCA (1979) for the same breed in Oyo town. Ngere and Aboagye (1981) reported a birthweight of 1.3 kg in Ghana while Ngere et al (1979) reported 1.5 kg in Ibadan. It appears that the location of the breed has an effect on the birthweight either as a result of differences in the management system practiced or the feeding regime and feedstuffs offered. Nevertheless, the WAD sheep is the smallest of the Nigerian breeds of sheep. The WAD weighed lighter at birth than the Uda and Yankasa breeds (Buvanendran et al, 1981).
The estimated average litter size at birth of 1.33+0.41 is higher than the estimates reported in the literature for indigenous Nigerian breeds (Buvanendran et al, 1981; Sackey et al, 1987 ). No case of quadruplets was observed in this study. Ngere and Aboagye (1981) observed a twinning rate of 55% in Ghana while Ademosun (1973) reported a 37% twinning rate which is slightly higher than the 31 % obtained in this study for the WAD sheep. Sackey et al (1987), on the other hand, reported 22% twinning rate in Yankasa kept at institution farms.
Table 1. Least squares means for birthweight, litter birthweight and litter size at birth (kg).
|
Class |
Birthweight |
Litter birthweight |
Litter size at birth |
||||
|
No |
Mean |
No |
Mean |
No |
Mean |
||
|
Least squares |
|
|
|
|
|
|
|
|
Overall mean |
809 |
2.15 |
193 |
4.06 |
610 |
1.33 |
|
|
|
SD |
|
0.46 |
|
0.77 |
|
0.41 |
|
Year: 1981 |
114 |
2 06c |
31 |
3.88cd |
86 |
1.39a |
|
|
|
1982 |
157 |
1.88d |
38 |
3.49e |
118 |
1.30abc |
|
|
1983 |
154 |
2 10bc |
40 |
4.23bc |
116 |
1.41a |
|
|
1984 |
127 |
2.31bc |
26 |
4.16bc |
96 |
1.24bc |
|
|
1985 |
122 |
2.35b |
33 |
4 42b |
92 |
1.37ab |
|
|
1986 |
69 |
2.46a |
13 |
4 82a |
52 |
1.28abc |
|
|
1987 |
66 |
2.11c |
12 |
3.70de. |
50 |
1.20c |
|
|
SD |
|
0.40 |
|
0.69 |
|
0.46 |
|
|
F. test |
|
(P<0.001) |
|
(P<0.001) |
|
(P<0.01) |
|
Season: Wet |
539 |
2.19a |
129 |
4.16a |
406 |
1.34a |
|
|
|
Dry |
270 |
2.09b |
64 |
3.85b |
204 |
1.32a |
|
|
SD |
|
0.43 |
|
0.76 |
|
0.21 |
|
|
F. test |
|
(P<0.001) |
|
(P<0.001) |
|
ns |
|
Type of birth: Single |
417 |
2.30a |
- |
- |
|
|
|
|
|
Twin |
374 |
2.00b |
187 |
4.01b |
|
|
|
|
Triplet |
18 |
1.88c |
6 |
5.65a |
|
|
|
|
SD |
|
0.39 |
|
0.80 |
|
|
|
|
F. test |
|
(P < 0.001) |
|
(P < 0.001) |
|
|
|
Sex: Male |
405 |
2.21a |
|
|
|
|
|
|
|
Female |
404 |
2.10b |
|
|
|
|
|
|
SD |
|
0.46 |
|
|
|
|
|
|
F. test |
|
(P<0.001) |
|
(P<0.001) |
|
|
|
Litter composition |
|
|
|
|
|
|
|
|
0 male, 2 females |
94 |
1.92b |
47 |
3.84b |
|
|
|
|
1 male, 1 female |
196 |
2.00a |
98 |
4.01a |
|
|
|
|
2 males, 0 female |
80 |
2.06a |
40 |
4 12b |
|
|
|
|
0 male, 2 females |
- |
- |
- |
- |
|
|
|
|
1 male, 2 females |
15 |
1.86b |
5 |
5.58a |
|
|
|
|
2 males, 1 female |
- |
- |
- |
- |
|
|
|
|
3 males, 0 female |
3 |
2.00a |
1 |
6.0a |
|
|
|
|
|
SD |
|
0.36 |
|
0.89 |
|
|
|
|
F. test |
|
(P<0.05) |
|
(P<0.01) |
|
|
SD = Standard deviation.
Means along the same column with different superscripts are significantly (P < 0.05) different from each other.
Table 2. Least squares constants (LSC) and additive correction factors (AFC) for birthweight and litter birthweight (kg).
|
Class |
Birth weight |
Litter birthweight |
|||
|
LSC |
ACF |
LSC |
ACF |
||
|
Sex: |
|
|
|
|
|
|
|
Male |
-0.55 |
0.00 |
|
|
|
|
Female |
+ 0.055 |
0.11 |
|
|
|
Type of birth: |
|||||
|
|
Single |
-0.24 |
0.00 |
|
|
|
|
Twin |
+0.06 |
0.30 |
+0.82 |
0.00 |
|
|
Triplet |
+0.18 |
0.42 |
-0.82 |
-1.64 |
|
Season: |
|||||
|
|
Wet |
-0.05 |
0.00 |
-0.155 |
0.00 |
|
|
Dry |
+0.05 |
0.10 |
+0.155 |
0.31 |
There was a significant year effect for all the three traits under consideration, though with no clear-cut trend. Birthweight increased throughout the duration of the study except for 1982 and 1987. The year 1987 witnessed a decline in performance for the three traits which may be as a result of the absence of supplementary diet for that year. Litter size at birth began to decline in 1986. This could be attributed to the possible effect d inbreeding since the Ife flock is closed. In addition, there has never been any conscious genetic improvement of the flock for any trait.
The effect of season was significant (P<0.01) for birthweight and litter birthweight but was not significant (P>0.05) for litter size at birth. Lambs born in the wet season were heavier than those delivered in the dry season by 0.1 kg. Similar results were obtained by Buvanendran et al (1981) and Wilson and Murayi (1988). The seasonal effect could be nutritional due to the quality of forage available to the ewe during pregnancy. This view was held by Adu and Olaloku (1979) who stated that the birthweight of lambs is significantly affected by the nutritional status of the ewe during pregnancy Osinowo et al (1989) also-observed that season of birth. Significantly influenced litter size at birth. The insignificant effect obtained in this study may be due to the tact that the dry season in the southern part of Nigeria is not as pronounced as in the northern part to warrant a high foetal mortality and/or because season in the cited reference was defined differently from the definition in this paper.
Litter size was positively correlated (+0.87) with litter birthweight but negatively correlated (-0.62) with birthweight. Birthweight dropped significantly from 2.3 kg for singles to 2.0 kg for twins and 1.88 kg for triplets. Litter birthweight, however, increased significantly from 4.01 kg for twins to 5.65 kg for triplets. Twins and triplets were thus 3.65 kg and 1.71 kg heavier than singles and thus the low birthweight for twins triplets are offset by high litter weight. These differences are quite notable and are maintained to maturity (Buvanendran et al, 1981). Though the growth rate of the WAD sheep cannot match any of the northern breeds, the higher litter size could bridge the productivity gap to a certain extent.
Ngere and Aboagye (1981) reported that type of birth affected birthweight. This was further supported by the reports of Ademosun (1973) and Ngere et al (1979) although the birthweights reported (2.5 kg and 1.5 kg) were higher and lower, respectively, than the value obtained in this study. This goes to show the high variability that exists in the WAD sheep for birthweight. Birthweight recorded in this study ranged from 2.8 kg to 1.2 kg. This provides opportunity for selection to improve birthweight.
Male lambs were found to be heavier than female lambs at birth in this study. Buvanendran et al (1981), however, did not observe any sex effect on birthweight. In the present study there were no differences between the sexes within the different types of birth. However, the presence of a male in a litter or the preponderance of males in a litter led to an increase in the litter birthweight and birthweight.
From the foregoing, multiple birth is desirable in WAD sheep because of the higher litter weight and litter size and absence of congenital malformation. It should therefore be selected for, to improve reproductive efficiency (furrier, 1969). This will necessitate adequate selection criteria and adjustment factors. Taiwo et al (1982) suggested that age of dam, sex of lamb, type of birth and season of birth need to be adjusted for. The values obtained in this study are indicative, but more studies are still required.
Improvement in management practices and system, feeding (regime and feedstuffs) and disease control are, however, imperative for sustainable increase in productivity.
Ademosun A A. 1973. The development of the livestock industry in Nigeria Ruminants. Proceedings of the Agricultural Society of Niger 10:13-20.
Adu I F and Ngere L 0. 1979. The indigenous sheep of Nigeria. World Review of Animal Production 15(3):51-62.
Adu I F and Olaloku E A. 1979. A note on nutrition during late pregnancy in West African Dwarf sheep. Animal Production 28: 123-126.
Buvanendran V, Adu I F and Oyejola B A. 1981. Breed and environmental effects on lamb production in Nigeria. Journal of Agricultural Science (Cambridge) 96:9-15.
Fall A, Diop M, Sandford J. Wissocq Y J. Durkin J and Trail J C M. 1982. Evaluation of the productivities of Djallonke sheep and N'Dama cattle at the Centre de Recherches Zootechniques, Kolda, Senegal. ILCA Research Report 3. ILCA (International Livestock Centre for Africa), Addis Ababa, Ethiopia. 70 pp.
ILCA (International Livestock Centre for Africa). 1979. Small ruminant production in the humid tropics. ILCA Systems Study 3. ILCA, Addis Ababa, Ethiopia, 122 pp.
Ngere L O and Aboagye G. 1981. Reproductive performance of the West African Dwarf and the Nungua Blackhead sheep of Ghana. Animal Production 33:249-252.
Ngere L O. Adu I F and Mani I. 1979. Report of small ruminant breeding subcommittee. NAPRI Bulletin 1. National Animal Production Research Institute, Shika, Zaria, Nigeria.
Osinowo O A, Olerunju S A A, Abubakar B Y. Buvanendran V, Onifade O S. Lakpini C A, Ekpe GA and Dennar FO. 1989. Adjustment factors for weaning weight and litter size in Yankasa sheep. Paper presented at the 14th Annual Conference of the Nigerian Society for Animal Production held at the University of Agriculture, Makurdi, Benue State, Nigeria.
Sackey A K, Okoye C I and Mohammed G S A. 1987. Prevalency of multiple birth in the Yankasa breed of sheep in Zaria. Proceedings of the 12th Annual Conference, Nigerian Society for Animal Production. Abstracts. p.19.
SAS (Software System for Data Analysis). 1982. SAS users guide: Statistics. SAS Inc., Cary, North Carolina, USA. 404 pp.
Steel R G D and Torrie J H. 1980. Principles and procedures of statistics - a biometrical approach. Second edition. McGraw-Hill Book Company, New York, USA. 633 pp.
Taiwo B B A, Ngere L O and Adelaye I O. 1982. Comparative growth performance of Nigerian dwarf sheep and its crosses with Permer, Uda and Yankassa. World Review of Animal Production 181:57-3.
Turner H N.1969. Genetic improvement of reproduction rate in sheep. Animal Breeding Abstracts 37(4):545-563.
Wilson R T and Murayi Th. 1988. Production characteristics of African long-fat-tailed sheep in Rwanda. Small Ruminant Research 1(1):3 17.
