Abstract
The objective of this research was to evaluate lamb diets with a high proportion of concentrate and various levels of physically effective neutral detergent fibre (NDF) using tropical ingredients. Four diets were formulated: D1 with 16.5% physically effective NDF (peNDF), D2 with 21.4% peNDF, D3 with 23.3% peNDF, and D4 with 24.6% peNDF. Twenty male Santa Inês lambs at four months old with an average liveweight (LW) of 18.6 ± 3.4 kg were fed for 49 days. There were no differences (P >0.05) among the diets in dry matter (DM) intake. Crude protein (CP) intake, relative to either LW or metabolic live weight (LW0.75) or LW, was greater (P ≤0.05) for D2 and D3 than for D1 or D4. Lower (P ≤0.05) NDF intake, relative to LW0.75 or LW, was lower for D1 than for the other diets. Selection indexes (SIs) were similar (P >0.05) among diets. Animals that consumed D1 had less (P ≤0.05) rumination time per bolus. Meaningful variations were not observed in performance and efficiency of finishing lambs that were related to differences in peNDF among the diets. Santa Inês lambs were able to adapt to diets with low levels of peNDF by increasing rumination time as a consequence of increased fibre consumption and greater particle size selection.
Highlights
Native Caatinga rangelands of north-eastern Brazil represent up to 90% of the feed source for sheep in that region (Costa et al, 2019)
The experimental protocol was approved by the Animal Experiment Committee of the Universidade Estadual Vale do Acaraú (Ethics Committee approval no. 031.12/2007)
Ingredients used in the diets for finishing the lambs included native pasture silage, annatto by-product, obtained from the extraction of the apocarotenoid food colouring from the seeds, soybean meal (Glycine max (L.) Merr.) obtained from oil extraction, ground maize (Zea mays L.) and limestone (Table 1)
Summary
Native Caatinga rangelands of north-eastern Brazil represent up to 90% of the feed source for sheep in that region (Costa et al, 2019). Forage potential of these semi-arid rangelands and seasonal changes in vegetation depend on climatic conditions, so quantity and quality peak for a few months of the year (Araújo Filho, 2013). Evaluating alternative diets for sheep in confinement is necessary owing to the diversity of local ingredients. These evaluations can provide recommendations for feedstuffs that could minimize costs with minimal effect on animal performance. Gallo et al (2019) found that a high-concentrate diet with 15% NDF produced better weight gain in finishing lambs than diets that were higher in fibre
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