Feed intake, digestive aspects and growth performances of Sicilo-Sarde lambs fattened through oat, vetch and ryegrass hay in the Tunisian North West

Abstract

In the Mediterranean areas, oat hay is the most used roughage in sheep feeding. However, in some favorable regions, cultivated fodders as vetch and ryegrass can be produced and harvested green or kept as hay or silage to feed livestock. Then, this study aimed to evaluate the effect of using various types of hay (oat, vetch and ryegrass) on lamb’s feed intake, nutrient digestibility, nitrogen balance and growth performances. For that, forty-eight male Sicilo-Sarde lambs (13.1 ± 1.9 kg of body weight, 60 days of age) were conducted in individual pens and fed hay and concentrate, both ad libitum. Lambs were divided, according to body weight (BW), into 3 homogeneous groups of 16 lambs each and were randomly assigned to one of three diets that were neither isoenergetic, isoproteic nor isofibrous and where the roughage was either oat hay (OH), vetch hay (VH) or ryegrass hay (RH). Then, each group was divided into two subgroups according to supplementation type, only conventional concentrate (CC), composed by 80% barley, 17% soya and 3% mineral vitamin supplement (MVS), or conventional concentrate plus 90 g of sunflower seed (SC). At the end of the growth trial, a digestibility assay occurred and the nitrogen balance was calculated. Total higher DM intake was recorded for VH-CC, VH-SC and RH-SC with an average of 540 g, however, the rest of groups had averagely consumed 471 g of DM. The diet had significantly affected the digestibility of DM, OM, CP and NDF. The DM, CP and NDF digestibility was higher with vetch and ryegrass hay compared to that of oat hay. The amount of daily nitrogen intake, fecal, urinary and retained nitrogen are highly affected by the diets and the higher nitrogen intake was attributed to vetch hay which is a legume. The lowest fecal nitrogen losses were observed in groups receiving either vetch or ryegrass hay. Urinary excretion also varies from 2 g/d for both groups receiving oat hay, to 3.9 g/d for VH-SC group. Nitrogen retention was slightly higher for groups that did not consume sunflower seeds compared to other ones. For all groups, the nitrogen efficiency exceeds 50% and the highest proportion was observed in RH-CC group with almost 62%. The diet had significantly affected the ADG and the total weight gain. It can be concluded that the intake of vetch and ryegrass hay resulted in higher nutrient digestibility while enhancing nitrogen retention. Moreover, the addition of sunflower seeds did not alter lamb’s growth performances.