Effect of feeding level in late pregnancy and early lactation and fibre level in mid lactation on body mass, milk production and quality in Awassi ewes

Abstract

AbstractIn west Asia, it is traditional for sheep to gain body condition when low-cost native pastures are available and to mobilize reserves thus built up at other times. With diminishing shares of native pasture, crop by-products and food grains are increasing in sheep diets, and facilitate feeding for constant body condition.In a 2 × 2 × 2 factorial experiment, 48 Awassi ewes were individually fed indoors, nursed single lambs for 42 days, and were hand-milked from day 29 after lambing. Dietary treatments were imposed at different times: level of feeding (i) in the last 24 days of pregnancy (Lconstv. Lmob), (ii) in days 18 to 60 after lambing (Lconstv. Lmob), and (iii) level of fibre in days 60 to 102 after lambing (Fhighv. Flow). RationsPconst, Lconst, Flowand Fhighwere calculated to maintain body condition. Fhighprovided the calculated maximum ingestible quantity of barley straw and Flowprovided 0·08 kg barley straw per kg diet. Live weights (M) of ewes and lambs, milk yield and milk quality were recorded.WithPconst, andPmob(0·51 and 0·33 MJ metabolizable energy (ME) per kg M0.75per day), M gains were 140 and 23 g/day (P< 0·001). Lamb birth mass and subsequent maternal milk yield were not affected. WithLconstandLmob(0·81 and 0·61 MJ ME per kg M0.75 per day), M changes were -28 and -70 g/day (P< 0·001) and milk yields (calculated in part from lamb growth) were 1042 and 892 g/day (P < 0·01). Fhighand Flow(385 and 170 g acid-detergent fibre per kg dry matter) were compared in a two-period change-over design experiment. Milk yields were similar (414 and 427 g/day), milk fat concentrations were 64·8 and 72·9 g/kg (P < 0·001) and milk fat yields were 26·5 and 31·1 g/day (P < 0·001) but solids-not-fat and protein yields were not affected.There were benefits and costs in manipulating body reserves in Awassi sheep. M at lambing affects milk yield and body condition around mating is known to improve lambing rate. The existence of body reserves also allows body condition to be lost in late pregnancy and early lactation without affecting health or apparent welfare, which simplifies management of pregnant ewes, permits feeding of milk-fat-increasing high-fibre diets but the ME to maintain increased body reserves must not be ignored.