Nutritive evaluation of ammonia treated olive tree leaves for lactating sheep

Abstract

The purpose of this study was to investigate the preservation time of fresh olive tree leaves (OTL) after treatment with ammonia (AM-OTL) solution, the improvement of its nutritive value and the effect on milk yield and milk composition of dairy ewes. The crude protein (CP) content of OTL treated with a 25% aqueous ammonia solution (5 1 per 100 kg fresh OTL) increased from 96 to 180 g kg −1 dry matter (DM) just after the bags were opened, and 164 and 155 g kg −1 DM 2 and 12 months after treatment, respectively. The non-protein nitrogen of AM-OTL was 312 g kg −1 CP compared with 100 g kg −1 CP of fresh untreated OTL (F-OTL). Results of a digestibility experiment showed that the apparent digestibility (g kg −1) of AM-OTL increased ( P < 0.05) for CP, crude fibre (CF), neutral detergent fibre and acid detergent fibre by 47.4%, 19.4%, 13.3% and 10.5% and decreased for ether extractives (EE) by 10.7% in relation to F-OTL. The nutritive value was estimated to be 4.60 and 4.81 MJ of net energy of lactation (NE L) kg −1 DM for F-OTL and AM-OTL, respectively. In the second experiment 24 dairy lactating ewes of the Karagouniko breed (55 kg of average BW) were used and divided into two equal groups, immediately after weaning of their lambs. Using a cross-over design, ewes in Group 1 were fed a diet (A) with 1.2 kg AM-OTL + 0.25 kg wheat straw+ 0.88 kg concentrates. Ewes in Group 2 were fed a diet (B) with 0.8 kg alfalfa hay +1 kg concentrates. Diet (A) caused an increase ( P < 0.05) in soluble CP and a reduction ( P < 0.05) in casein content of milk. Fatty acid composition of milk fat was affected by AM-OTL with a reduction ( P < 0.001) of short chain (C6 to C16:l) and an increase of long chain (C18, C18:1) fatty acids. The results showed that ammonia treatment preserves OTL, improves their nutritive value and allows their inclusion in ruminant diets by replacing other expensive roughages.