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| Figure 1. Effect of the season on the weight of lambs born during spring and autumn |
| Livestock Research for Rural Development 27 (7) 2015 | Guide for preparation of papers | LRRD Newsletter | Citation of this paper |
Sheep farming is considered as the leading supplier of red meat in Algeria. Composed of several breeds, “Ouled Djellal” alone holds 61% share of the national sheep effective. It is known for its hardiness, adaptation to different environments, and its best growth performances.
A set of growth traits concerning 113 lambs born during spring and autumn were studied, to determine the effect of lambing season, sex of the lamb, the birth type and age of the mother. The animals maintained under a semi-intensive breeding system, and fed with dam's milk and fodder, were subject to weekly measurements of weight and average daily gain at different ages (0 to 90 days). As a result, the effect of the season was undoubtedly undeniable in extent, the best weights and average daily gains were recorded during spring,the difference between both seasons in term of average daily gains was highly significant (p < 0.01) according to z and t-test. The influence of sex on growth performances of lambs during the two seasons showed a superiority of males over females, whereas the birth type showed a superiority of singles over twins. The growth performances were highly related to the age of mothers; according to the analysis of variance (ANOVA), the differences between age groups were highly significant (p < 0.01). The highest lamb’s weights were related to mother’s age comprised between 3 to 9 years, whereas younger (< 3 years) and much older (> 9 years) ewes gave less vigorous lambs with low growth capacities. Finally, it was concluded that Ouled Djellal breed performances were very satisfactory.
Keywords: autumn, average daily gains, growth parameters, spring, weights
L’élevage ovin est considéré comme premier fournisseur de la viande rouge en Algérie. Composé de plusieurs races, Ouled Djellal détient à elle seule la part de 61% de l’effectif ovin national. Elle est réputée pour sa rusticité, son adaptation aux différents milieux et ses meilleures performances de croissance.
Un ensemble de caractéristiques de croissance concernant 113 agneaux nés durant le printemps et l’automne ont été étudiés, afin de determiner l’effet de la saison d’agnelage, du sexe de l’agneau, du type de naissance et de l’âge de la mère. Les animaux maintenus sous un système d’élevage semi-intensif et nourris avec du lait maternel et du fourrage, ont été sujets à des mesures hebdomadaires du poids et du gain moyen quotidien à differents ages (0 à 90 jours). Comme resultat, l’effet de la saison a été incontestable dans la mesure où les meilleurs poids et gains moyens quotidiens ont été enregistrés durant le printemps, la difference entre les deux saisons en terme de gain moyen quotidien a été hautement significative (p < 0.01) selon les tests z et t. L’influence du sexe sur les performances de croissance des agneaux durant les deux saisons à montré une supériorité des males par rapport aux femelles, alors que le type de naissance a montré une supériorité des simples par rapport aux doubles. D’autre part, les performances de croissance etaient hautement relatives à l’age des mères, selon l’analyse de variance les differences entre les groupes d’age etaient hautement significatives (p < 0.01), les poids les plus importants etaient relatifs à l’age des mères compris entre 3 à 9 ans, tandis que les plus jeunes (< 3 ans) et les plus vieilles (> 9 ans) brebis ont donné des agneaux moins vigoureux, avec de faibles capacités de croissance. Finalement, il a été conclu que les performances de la race Ouled Djellal ont été trés satisfaisantes.
Mots clés: automne, gains moyens quotidiens, paramètres de croissance, printemps, poids
Sheep farming has a very important place in the Algerian agriculture and economy; it holds the main position in the herd and is the leading supplier of red meat. It has been estimated at 20 million heads, among which 80% are distributed in the northern part of Algeria (Kerboua et al 2003).
Body weight and growth are important in the total productivity, especially when the meat production is the main objective; a high birth weight allows the animal to well start his career, and grow rapidly before and after weaning predisposes, to a better diseases resistance and to reach quickly puberty and maturity (Sulieman et al 1985).
These characteristics explain the importance of the Ouled Djellal breed in Algeria, accounting for 61% of the national sheep effective (Dehimi 2005). The Ouled Djellal mutton was introduced in Algeria by Beni Hilal tribes during the eleventh century. It is an entirely white sheep, with a fine tail and wool, reaching puberty at the age of 8 to 10 months, the first calving at 15 months old and the lamb’s weight at birth is about 3.50 Kg (Chellig 1992). The weaning age is around 3 months (Dekhili and Mahnane 2004),with a fatting period of 60 to 70 days, and an average daily gain of 150 to 200 g per day (Chellig 1992).
The scarcity of published data on Ouled Djellal growth performances, and the interest taken to this breed prompted us to conduct this study, whose main objective was to study the lambs’ growth, during autumn and spring, while taking into account other factors affecting growth variations such sex, birth type and age of the mother.
The study was conducted in the region of Chlef; an area located in the North-West of Algeria and covering approximately 4700 km². It corresponds to a large Neogene basin, bordered on the north by the Dahra mountains and on the South by the Ouarsenis mountains. This region is characterized by two bioclimatic zones; the semi-arid prevailing in the central and southern part, and the sub-humid in the northern part, with an average annual rainfall of 300 mm/year and a mean temperature of 7 °C during winter and 37 °C during summer (ANATA 1996). Livestock in the region of Chlef remains largely based on sheep, and farming dominates over production of meat and wool. Sheep farming is sedentary, mostly concentrated in the plains and the lower valleys.
The study took place during the period from 2010 to 2014, and involved a sample of 113 lambs of the Ouled Djellal’s breed including 51 lambs born during autumn and 62 lambs born during spring.
The animals used in this study were maintained under semi-intensive breeding system, with a feeding system based on grazing until June, and cereal stubble during summer. During food scarcity period and harsh climatic conditions, the mothers were kept in barns and fed with natural hay and wheat straw, supplemented by barley and wheat bran concentrate,minerals and vitamins. Lambs born were kept with their mothers receiving dam's milk,some fodder mixture and twice a day fresh water.
Once born, the lambs were identified with ear tags including the date of birth, the animal’s mother and an identification number.
In order to monitor the growth performances, lambs were weighed within 10 hours after birth, then a weekly weighing (weights and average daily gains) was performed between the age 0 to 90 days (from birth to weaning). Lambs’ weights were taken in the morning on an empty stomach, using a high precision balance and taking in consideration the lambing season, the sex, the birth type and the age of the mother. This latter parameter obtained following teeth examination was divided into 4 age groups: less or equal to 3 years, 3 to 6 years, 6 to 9 years and more than 9 years.
Considering the interactions between all the studied factors as negligible, the statistical analysis was performed using a trial version of XLSTAT 2014.5 (Addinsoft 2014), leading to univariate analysis (descriptive statistics and graphical analysis) and bivariate analysis (regression and determination coefficients R²). The growth performances according to seasons were compared using z and t-test. Finally, in order to test the impact of the mother’s age on lamb’s weight, an analysis of variance (ANOVA) was performed followed by Tukey and Newman-keuls means comparison tests.
Although the birth mean weight was identical during spring (3.05 kg) and autumn (3.03 kg), there was a highly significant difference in weight gain, between lambs born during the two seasons; the highest gains were recorded in spring (Figure 1). Our results indicated that lambs born during spring showed an increase in mean weight of 13.3 kg for the period from birth to the age of 90 days, whereas during the same time frame (0-90 days) the mean weight increase was 11.5 kg for lambs born during autumn. These findings were concordant with those reported by other authors (Anallaet al 1997 and Rekik et al 2008) who found that the lambing season was a highly significant factor of influence. According to these authors, the best weight increases were always related to spring. In contrary, Fernandez-Abella (1991) and Chniter et al (2011) pointed out that lambs born during the fall season were often heavier than those born in spring for some breeds. This difference in results was particularly related to the breed, the experimental conditions, the year, the herd effect, the environment, and especially the holding conditions. Also, the difference in weight evolution between lambs born during these two seasons was mostly related to favourable climatic conditions; spring was characterized by the availability of tender and abundant herbage, thus sheep tended to produce milk of better quality and in sufficient quantities, this led to a better weight gain for lambs born during this season compared to those born during autumn. Nevertheless, whatever the season the evolution of weight was highly explained by the age of lambs, with a determination coefficient of 0.99.
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| Figure 1. Effect of the season on the weight of lambs born during spring and autumn |
The average daily gain showed the incontestable effect of season, with a mean of 146g/d during spring and 125g/d during autumn, this difference was highly significant (p < 0.01) according to the z and t-test. The low coefficient of variation (= 3%) for both season reflected certain stability of the average daily gain, however a slightly decreasing tendency was recorded between the age group 0 to 30 days and the age group 30 to 90 days during the two seasons, the average daily gain decreased from 152 g/d to 139 g/d during spring, and from 132 g/d to 123 g/d during autumn. This decreasing behaviour was mostly related to the nature of diet, based exclusively on milk during the age 0 to 30 days which tend to produce a high daily gain. In contrary, the age 30 to 90 days characterized by a low milk productivity of the mother and a progressive transition to solid food, led to a slightly low daily gain. This contrast the finding of Boujenane and Kerfal (1992) who reported a low daily gain during the age 10 to 30 days due to a low milk productivity of D’man breed.
Statistically, as shown by the negative value of the regression coefficient (Figure 2), the average daily gain was negatively correlated with the age during spring and autumn with a slightly low determination coefficient around 0.68.
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| Figure 2. Effect of the season on the average daily gain (ADG) of lambs born during spring and autumn |
As shown previously, while being highly related to the age of lambs, there was a clear difference in weight evolution according to sex (Figure 3), our results showed that males were always heavier at birth and grew rapidly, this highly concurs with the observations reported by Ricordeau et al (1984); Chikhi and Boujenane (2003) and Hassen et al (2004). During spring the difference in weight according to sex increased from 0.36 kg at birth to 0.90 kg at the age of 90 days, whereas during autumn the difference was slightly low, and raised from 0.30 kg at birth to 0.60 kg at 90 days.
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| Figure 3. Effect of the sex on the weight of lambs born during spring(sp) and autumn(au) |
The average daily gain (Figure 4) was negatively related to the age group, the difference between males and females increased from 2.33 g/d at 0-30 days to 22.2 g/d at 60-90 days during spring, and from 9.20 g/d at 0-30 days to 19.0 g/d at 60-90 days during autumn. Several authors (Jurado et al 1994; Theriault 2003; Dikmen et al 2007; Rekik et al 2008 and Chemmam et al 2009) have reported that the average daily gain of males was always significantly higher than females’average daily gain for different breeds such as Merinos, Sufflolk, Dorset, Awassi and D’man. However a recent study conducted by Benchohra et al (2013) showed that Rembi lambs’ growth rate was not affected by sex during the lactation period.
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| Figure 4. Effect of the sex on the average daily gain of lambs born during spring(sp) and autumn(au) |
Overall, the difference in growth between sexes lies in conformation and metabolism; according to Benevent et al (1971) each sex evolves under the control of its own endocrine balance, which promotes a more or a less important development of organs.
Regardless the season, single birth lambs were always heavier than twin whatever the age as indicated by the mean weight of each birth type (Figure 5). The difference between spring single and twin birth, raised from 0.78 kg at birth to 1.50 kg at 90 days, whereas in autumn the difference less pronounced at birth 0.33 kg, increased to 1.38 kg at 90 days. These results were consistent with those of several authors (Afolayan et al 2006; Ekiz and Altinel 2006; Kuchtik and Dobes 2006; Merghem e tal 2011 and Yilmaz and Altin 2011).
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| Figure 5. Effect of the birth type on the weight of lambs born during spring(sp) and autumn(au) |
The difference in the average daily gain (Figure 6) between spring single and twin birth decreased from 36.7 g/d at 0-30 day to 22.2 g/d at 60-90 days, whereas the difference fell from 19.7 g/d to 15.4 g/d during autumn at the same age group. Even though the fast decrease in their average daily gain, single birth average daily gain remained higher than twin average daily gain all over the period ranging from 0 to 90 days. As shown in this study, superiority of single over double birth lambs has been reported by (Dekhili and Mahnane 2004 and Boussena et al 2013). According to Theriez (1991), the negative link between litter size and lamb growth is most of the time assigned to a reduction in the quantity of milk available per lamb.
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| Figure 6. Effect of the birth type on the average daily gain of lambs born during spring(sp) and autumn(au) |
Regardless of the season, results showed that the highest lamb’s weights were mainly related to the second age group “3 to 6 years” followed by the third group “6 to 9 years”. During spring the average lambs’ weights were 10.6 kg for the second age group and 10.2 kg for the third age group and respectively 9.99 kg and 9.24 kg during autumn (Figure 7 and 8). This finding was in agreement with those of (VanWyk et al 1993 and El Fadili 2008) who showed the significant influence of the mother's age on lamb's weight, furthermore, our results revealed that lamb’s growth was also influenced by ewes age (Figure 9 and 10).
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| Figure 7. Effect of the mother’s age on the weight of lambs during spring |
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| Figure 8. Effect of the mother’s age on the average daily gain of lambs during spring |
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| Figure 9. Effect of the mother’s age on the weight of lambs during autumn |
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| Figure 10. Effect of the mother’s age on the average daily gain of lambs during autumn |
The results of the analysis of variance showed that differences between age groups were highly significant (p < 0.01). Examination of the means (Table 1) resulted in 4 groups (A, B, C, and D) highly different (p < 0. 01) according toTukey and Newman-keuls tests.
| Table 1. Distribution of the 4 age groups of mothers | |||||
| Category | Mean | Groups | |||
| From 3 to 6 years (spring) | 140 | A | |||
| From 6 to 9 years (spring) | 135 | A | B | ||
| From 3 to 6 years (autumn) | 135 | A | B | ||
| From 6 to 9 years (autumn) | 118 | A | B | C | |
| Less or equal to 3 years (spring) | 116 | B | C | ||
| Less or equal to 3 years (autumn) | 96.4 | C | D | ||
| More than 9 years (spring) | 93.2 | D | |||
| More than 9 years (autumn) | 82.9 | D | |||
The first group A, birthing lambs with the highest weight included ewes aged from 3 to 9 years, regardless the season. Group C was mostly related to the age group less or equal to 3 years, whereas the lowest weights were always related to the age group more than 9 years. Indeed, this finding was also mentioned by Chopra and Acharya (1971) who showed that the intermediate age generally, gives birth to more vigorous lambs, whereas younger and older ewes give lighter lambs. The differences in lamb’s weight are explained by the fact that younger ewes (< 3 years) are still growing with bodies still developing, which leads them to share nutrients with their lambs, whereas ewes between 3 to 9 years have reached full growth and thus the lambs are provided with enough quantitative and qualitative nutrients. It should be also noted that the increasing growth in lambs’ weight was related to the maternal behaviour; so lambs born from mothers aged of 3 to 9 years, which have already given several births, were much better supported than those born from first furrowing mothers aged less than 3 years. Allouche et al (2011) found similar results as ours for the same breed.
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Received 13 March 2015; Accepted 19 May 2015; Published 2 July 2015