Jean-Claude Emile

In situ degradation kinetics of maize hybrid stalks

Abstract An understanding in plant factors influencing digestion kinetics could help develop maize cultivars, thus improving digestibility and consequently the production of ruminants. The stalk fraction of maize hybrids was used to study the cell wall digestion of hybrids varying from the brown midrib-3 (bm3) and their isogeneic normal (N) to normal hybrids. Cell wall constituent contents (NDF, ADF, ADL), soluble carbohydrates (SC), in vitro dry matter digestibility (IVDMD) and ruminal degradation kinetics of the dry matter (DM) and the cell wall (measured as NDF) were determined on stalk samples harvested at silage stage (30–35% DM, whole plant). Six comparative studies of in situ degradability involved 3 comparisons of the bm3 and their N isogeneic hybrids (Ex223, Ex234 and Adonis) and 3 comparisons involving 2 extreme genotypes (DK265 and Stefania): each were compared to the control genotype (Adonis). A comparison of the three sets of N and bm3 hybrids demonstrated that the mutation contained a lower concentration of the cell wall constituents. Hemicellulose rather than cellulose was generally present in lower amounts in the cell walls. Higher SC content and IVDMD were also seen in the bm3 maize. Mean effective degradabilities for both DM (64.4 versus 53.2%) and NDF (36.3 versus 29.5%) were higher ( P

Variation and covariation of silage maize digestibility estimated from digestion trials with sheep

SummaryVariation and covariation for agronomic and digestibility traits of silage maize are reported from a compilation of 22 years of experiments with standard sheep. Genotype effects of DOM and DCF were highly significant, even when genotypes were nested in earliness groups or brown-midrib hybrids discarded (Table 2). The genetic variance of crude fiber content was low, but the variance of the DCF was high. The genetic variance of DOM was about 4 times lower than genetic variance of DCF, but broad sense heritability of DOM was higher because of lower residual variance (Table 3). Genetic correlations between grain or crude fiber content and DOM had similar absolute values, 0.65, so each of these two traits was an important but not the unique determinant of silage maize quality. There was no correlation between DCF and grain or crude fiber content. Yield was not related to DOM or DCF within each group of earliness, allowing some quality improvement without agronomic drift (Table 4). Except for late hybrids, most of DOM differences between groups of earliness came from lowering of minimum value, while maximum values were similar. It was the contrary for DCF, with similar minimum values for all groups (Table 5). There was no obvious correlation between year of registration of hybrids and DOM or DCF, but extra new variation seemed obtained only for low values (Figs 1, 2; Table 6). IVDOM according to the APC process was a poor predictor of DOM, especially when brown-midrib hybrids and earliness effects were discarded; but because heritability of this trait was similar to DOM heritability, such enzymatic processes could probably be used to avoid drift towards poor DOM with hybrids bred for higher stalk strength.

Genetic variations in the digestibility in sheep of selected whole-crop cereals used as silages

Whole-plant winter cereals could be of great interest if used as silages for ruminant feeding as opposed to summer crops in that they would spare water resources or valorize low-input management. This study aimed to compare the feeding value of rye, barley, wheat (two genotypes) and triticale (six genotypes). The cereals were sown in October and harvested as silage in June. Forages were offered to Texel castrated sheep in order to evaluate the organic matter digestibility (OMd). The OMd of the wheat cultivars was higher (61.6%, P<0.05) than those of barley (57.2%) and rye (54.7%) but no different from that of triticale (60.6%). Within the triticale genotypes, OMd ranged from 54.7 to 62.3%. The presence of rough barbs should explain the relatively low intake of the cereals with the exception of wheat. Winter cereals provide good-quality forage for feeding ruminants. Wheat has a higher nutritional value than barley and rye and a wide variability for digestibility seems to exist within the triticale cultivars. Such variability in a species known for its ability to be cropped under limiting conditions should be explored in much greater depth as it could result in providing farmers with genotypes of good quality with an acceptable yield at a lower cost.

Aerobic stability of triticale silage in single culture or in mixtures with oat and/or legumes

The objective of the present study was to evaluate the aerobic stability and losses during the fermentation process of triticale silages in single crop or in mixtures with oats and/or legumes. The following crops were used for silage production: triticale (X. Triticosecale Wittimack), triticale intercropped with forage pea (Pisum arvense) and triticale intercropped with oats (Avena strigosa Schreb), forage pea and vetch (Vicia sativa). The dry matter content and its recovery did not differ among the silages. Buffer capacity was higher for tricale silage intercropped with oats, forage pea and vetch(88.67 m eq. NaOH/100 g DM) followed by triticale intercropped with forage pea (80.80 m eq. NaOH/100 g DM). Electric conductivity values were higher in the intercropped triticale silages. Triticale silage presented the lowest temperatures observed in the silos, and the silages of intercropped triticale silages presented higher heat retention and higher pH values. Silage of triticale intercropped with oats and legumes presented lower aerobic stability but it did not reduce the aerobic stability of the total feed. Dry matter recovery during storage and in stability evaluations in aerobiosis is similar among the silages.

In-vivo assessment of different breeding strategies for improving quality in tall fescue

Improving quality in tall fescue (F. arundinacea) is a major objective in forage grass breeding. However, selection based on in-vivo tests (voluntary intake or digestibility) is not possible in grasses and we have therefore to use indirect criteria. This abstract aims to compare final quality, as assessed from animal trials, of three genotypes resulting from three different breeding strategies developed in the INRA Station of Lusignan : 1) selfing within European tall fescue and mass selection for leaf flexibility (Cv ’Lubrette’), 2) hybridisation between European and Mediterranean ecotypes of tall fescue and fertility restoration by colchicineinduced polyploidization (experimental genotype ’Amphiploid’) and 3) intergeneric hybridisation at the tetraploid level between Italian ryegrass and a wild tall fescue species, F. arundinacea var. glaucescens, (experimental genotype ’Festulolium’). The Cv ’Clarine’ bred within European tall fescue and without any particular attention to quality, was used as control. Heading date was similar among the four genotypes and hold to have not interfered with quality in the comparison. The genotypes ’Clarine’, ’Lubrette’ and ’Amphiploid’ were assessed during three years (1980-1982) while the genotype ’Festulolium’