I. BEN ABDALLAH¹

A. HAMROUNI¹

M. DJEMALI¹

¹Animal Genetic and Feed Resources Lab, INAT, 43 Avenue Charles Nicole, 1082 Tunis Mahrajene, Tunisia

Abstract – The Barbarine breed with big tail still requires interest although it has been the subject of several studies given its size and distribution in different geographical areas and production systems. The objectives of this study were to: 1) Identify the main sources of variation in the different traits of breed growth, 2) Estimate the adjustment coefficients for dominant non-genetic effects, and 3) Estimate the genetic parameters of the trait traits growth in the breed. Records of a total of 191 371 lambs collected over 10 years (from 2004 to 2014) were used in this study. A linear model including the livestock sector (state or private), farm-herd-year of birth-lambing season, maternal age, and sex-mode of birth was used to identify the main sources of variation in the growth of Barbarine. Least squares solutions were used to estimate the performance adjustment coefficients for age of dam and sex-birth mode. The REML method was used for estimating heritability. The main results showed that the average performance was 4,2 ± 0,42 kg; 5,37 ± 1,32 kg; 8,29 ± 2,11 kg ; 14,04 ± 3,46 kg; 16,21 ± 3,83 kg; 127 ± 56 g/day; 187 ± 49 g/day; 165 ± 61 g/day; 134 ± 45 g/day and 135 ± 42 g/day for BW, W10, W30, W70, W90, ADG030, ADG1030, ADG3070 and ADG3090, respectively. The coefficients of determination R² varies between 36% and 48%. Sector, age of dam, sex-mode of birth, and farm-herd-year-in-season combination were found to be the major factors that significantly affect lamb growth from birth to weaning at 90 days. The phenotypic correlations between different weights were positive and ranging from 0.122 to 0.99 between ADG030-ADG3090 and W30-ADG030, respectively. The estimated heritabilities ranged for the first group from 0.09 ± 0.31 to 0.409 ± 0.64 for the weights BW, W30, W70 and W90 and from 0.14 ± 0.37 to 0.468 ± 0.68 while the second group was 0.109 ± 0.33 to 0.251 ± 0.5 and 0.124 ± 0.35 to 0.444 ± 0.66.

Keywords: sheep, Barbarine, growth, adjustment, heritability.

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Essai d’application d’une sylviculture propre aux peuplements artificiels de Pin maritime (Pinus pinaster L.) de la série forestière unique de Hamdia (Tabarka)

N. BOUSSAIDI¹

 T. MECHERGUI²

J. WAHBI¹

¹ Institut Sylvo-Pastoral de Tabarka (Laboratoire des Ressources Sylvo-Pastorales)

² Faculté des Sciences de Bizerte

Abstract – In the unique serial of Hamdia (Tabarka), maritime pine, planted since 1965, occupies in mixture with the cork oak and stone pine 393 ha. Reforestation efforts, in terms of production of lumber and industrial wood, both in quality and quantity, remain dependent on the application of appropriate silvicultural methods (pruning, thinning). The density at that time was 2500 plants per hectare and 982500 plants throughout the serial. This density decreased from one year to another until reaching 259874 according to the first inventory made in 1995 with a volume of 12398 m³ of wood. In 2016, a second inventory was carried out, where we noticed an increase in number of trees and consequently in volume which could be explained by a strong regeneration by sowing in the maquis, the enclaves and after the passage of fires and a lack of application of specific silviculture to these stands, something that we propose in this study that takes into account the social problem and able to ensure the sustainability, the preservation of the forest ecosystem and the production of wood.

Keywords: Maritime pine, pruning, thinning, inventory, silviculture, volume.

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Effet de la qualité du lait cru sur la qualité de la poudre de lait écrémé

Y. HACHANA ¹

W. AOUINI¹

L. LANOUAR¹

M. GUIDER²

¹ High Institute of Agriculture Chott-Meriem Sousse Tunisia

² Elben Industries Candia Sidi Bouali Sousse

Abstract – The aim of this work was to evaluate the impact of the physicochemical and bacteriological quality of raw milk on the quality of skimmed milk powder. Although the physicochemical characteristics of raw milk, intended for drying, comply with the required standards, they nevertheless remain very variable from one delivery to another, and caused instability in the composition of the produced skimmed milk powder from one batch to another. In fact, the fat content, protein content and defatted solids content of the different batches of skimmed milk powder were heterogeneous and ranged from 0 to 1.5g /100g, from 32.6 to 37.30g /100g and from 72 to 82g /100g respectively. Humidity content ranged from 3.07 to 4.33%. Despite that the average of bacteriological count of the raw milk delivered was very high (>2.10⁶cfu/ml), the majority of produced skimmed milk powder batches showed total bacterial count in accordance with national standards. The turbidity test revealed that 92% of the batches produced, had visible impurities less than or equal to 8 particles.

Keywords: Milk, composition, quality, transformation, drying.

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Régénération artificielle du Chêne-liège et du Chêne-zeen: effets du paillage et des abris-serres sur l’installation et la croissance des plants

T. MECHERGUI¹

N. BOUSSAIDI²

¹ Faculté des Sciences de Bizerte (Tunisie).

² Institut Sylvo-Pastoral de Tabarka, Laboratoire des Ressources Sylvo-Pastorales.

Abstract – The objective of the present study is to assess the effect of mulching and tree shelters on the establishment and early growth of cork oak (Quercus suber L.) and zeen oak (Quercus canariensis Willd.). Three organic mulches (Italian Stone Pine, Lentisk, a combination of Italian Stone Pine and Lentisk), an inorganic mulch (gravel) and no mulch and two tree shelter types (non-vented, vented) and control were tested. The experiment was set up in the reserve of barbary red deer at the M’hibeus National Forest, Northwestern Tunisia (Sejnane). Tree shelters did not have a significant effect on the seedlings survival rate for both oaks, whereas they significantly improved their height growth compared to unsheltered seedlings; average growth rate in height inside non-vented and vented tree shelters was each year significantly greater, respectively, by 7.7 and 12.5 cm for cork oak, and by 7 and 11 cm for zeen oak. Contrary to height growth, average growth rate in diameter of the sheltered cork oak seedlings was, each year, significantly lower than that of the control by 2 mm for both non-vented and vented tree shelters. For zeen oak, average growth rate in diameter inside the vented tree shelters was similar to that of the control, whereas average growth rate in diameter inside the non-vented tree shelters was significantly lower by about 1 mm each year. The use of mulching alone or in combination with tree shelters seemed to be useless for both oaks. This is because of the site fertility where the experimentation was carried out.

Keywords: Quercus suber, Quercus canariensis, mulching, tree shelters, survival rate, growth.

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