Conservation agriculture (CA) has been promoted as a strategy to cope with deterioration in soil fertility, but its adoption on smallholder farms in tropical areas remains limited. In Madagascar, livestock production is facing shortages in forage especially during the dry season. The value of cover crops used in CA as livestock feed could be an incentive to make this form of agriculture more acceptable in rural areas. To do so, farmers must find a trade-off between the use of biomass from cover crops for animal production and its maintenance on the soil to meet CA's criteria. In this study, we evaluated the impact of biomass flows (cover crops and manure) between cropping and cattle production in crop-livestock farms in the Lake Alaotra region. Surveys among crop-livestock farmers were used to calculate feed concentrate and mineral fertilizer equivalents. Our results show that on average 42, 22 and 10% of biomass production (dry matter basis) of Brachiaria spp., Stylosanthes guianensis and Vicia villosa, respectively, are used for livestock feeding. The economic benefit in feed concentrate equivalent is between €73 and €723/year per farm. The use of manure contributes, just as CA, to improve soil fertility without using external fertilizing resources. The economic benefit in mineral fertilizer equivalent is between €116 and €2365/year per farm. The integration of CA and livestock production shows, beyond the agronomic advantages, an obvious economic benefit, which is essential to secure the Malagasy agricultural systems. Moreover, this economic benefit is another argument for the dissemination of CA practices in rural areas.

Feed shortage during the dry season in the highlands of Madagascar negatively impacts the dairy cattle productivity, as well as the farmers’ income. Bamboo can produce a high quantity of biomass and could be an alternative way to increase the fodder supply for cattle. The present study aimed to assess the compositional information and the optimal rate of bamboo as fodder for dairy cattle. Leaf samples from nine bamboo species were collected to determine their chemical composition and nutritive value. A feeding experiment was also conducted using ten dairy cows, over ten weeks. Bamboo leaves were mixed with maize silage in five proportions: SIL0:BAM100, SIL25:BAM75, SIL50:BAM50, SIL75:BAM25 and SIL100:BAM0. The contents of dry matter, total ash and crude protein in the bamboo leaves were, respectively, 44.5-64.6 %, 6.68-18.5 % and 7.71-15.4 %. In the feeding trial, the dry matter intake of bamboo leaves was 1.6-7.1 kg per day, with an average of 4.8 kg per day. The dry matter apparent digestibility of bamboo leaves was 37.4-56.4 %. The milk production reached 13.6-14.4 L per cow, per day, but there was no significant difference concerning the rate of bamboo leaves in the mixed diet (p > 0.05). The introduction of bamboo leaves into the ruminants diet did not affect their milk production.

Precise techniques to estimate feed intake by ruminants is critical to enhance feed efficiency and to reduce greenhouse gas emissions and nutrient losses to the environment. Using a meta-analysis, we evaluated the accuracy of the n-alkane technique to predict feed intake in cattle and sheep, and assessed the relationships between feed intake and fecal recovery of n-alkanes. The database was composed of 28 studies, including 129 treatments (87 and 42 for cattle and sheep, respectively) and 402 animals (232 cattle and 170 sheep) fed at troughs, from published studies. Relationships between observed (in vivo measurement) and predicted feed intake by C31:C32 and C32:C33 n-alkane pairs were evaluated by regression. Meta-regression addressed the relationships between the difference in fecal recovery of n-alkane pairs and the error in intake estimation, as well as the amount and duration of C32 n-alkane dosing. Regression of observed intake on n-alkane-based estimates revealed good relationships in cattle (adjusted R² = 0.99 for C31:C32, and adjusted R² = 0.98 for C32:C33; P < 0.0001) and in sheep (adjusted R² = 0.94 for C31:C32, and adjusted R² = 0.96 for C32:C33; P < 0.0001). Fecal recovery of natural n-alkanes showed coefficient of variation about 15 and 16% for C31 and C33, respectively in cattle. In sheep, the coefficient variation was 8 and 14% for C31 and C33, respectively. The relationships between the difference of fecal recovery of n-alkane pairs and the error in feed intake estimation in cattle were characterized by an adjusted R² = 0.83 for C31:C32 (P < 0.0001) and adjusted R² = 0.93 for C32:C33 (P < 0.0001). In sheep, they were characterized by an adjusted R² = 0.69 for C31:C32 (P < 0.001) and adjusted R² = 0.76 for C32:C33 (P < 0.001). The n-alkane technique provided reliability for estimating feed intake in cattle and sheep in barn experiments. The present meta-analysis demonstrated that without correction for differences in fecal recovery of n-alkane pairs, deviation in feed intake prediction would occur. However, further research is necessary to determine the relationship between the n-alkane dosing procedure (daily amount and duration of dosing) and fecal recovery of n-alkane.

No abstract