The effect of ammonia treatment on the intake of straw and hay when offered with rations of concentrates to ewes in late pregnancy

Abstract

Finnish Landrace x Dorset Horn ewes were offered 300, 600 or 900 g fresh weight per day of concentrates and forage ad libitum from day 105 of pregnancy until lambing. Spring barley straw (S) or hay (H) was offered either untreated (U) or following treatment with anhydrous ammonia in an oven (T). Organic matter digestibilities (in vitro) were 0-42, 0-58, 0-42 and 0-60 and nitrogen contents were 7-2, 18-6, 12-0 and 25 0 g/kg dry matter for US, TS, UH and TH respectively. Forage intake did not differ between ewes carrying two or more foetuses but the small number of ewes carrying one foetus ate more straw (6-8 v. 4-5 g organic matter (OM) per kg live weight) than ewes carrying two or more foetuses. Ammonia treatment increased intake; the increase was larger on straw (4-6 v. 100 g OM per kg live weight) than on hay (9-0 v. 10-7 g OM per kg live weight). Replacement rates of forage by concentrates were -0-21, +0-06, -0-48 and +0-08 kg forage per kg concentrates for treatments US, TS, UH and TH respectively; only the value for treatment UH differed significantly from zero. On most treatments forage intake decreased as pregnancy progressed and the declines were greater when treated forages were offered. Concentrate level had a large effect on most aspects of ewe performance. Ewes offered treated forage gained slightly more weight in pregnancy (138 v. 104 g/day), had a slightly smaller decrease in body condition score (-0-54 v. -0-68) between day 105 and lambing but did not have greater lamb birth weights than ewes on untreated forage.

The voluntary intake and utilization of forage-concentrate diets by ewes in late pregnancy

“…Higher live-weight gains in this study are comparable to those of Ledin (1986), Orr and Treacher (1984), Orr et al (1985). Weight lost at lambing increased, as might be expected, with litter weight (P ^ 0.001).…”

“…When concentrate was fed, the VDMI of hay was greater for lucerne hay. These results with those of Orr and Treacher (1984) and Orr et al (1985) who observed that when ewes in late pregnancy were given diets with varying When forage and concentrate with a high protein content are offered, the voluntary forage intake increases, only when the amount of protein in the forage is less than 8% of DM (Osbourn, 1967). The pasture hay in this experiment contained 9% CP which is more than the level at which Osbourn (1967) suggested that protein intake may be limiting.…”

“…Physical limitation of intake during the last week of pregnancy impedes meeting the high requirements of this physiological state (Forbes, 1970). Quality of forage and amount of concentrate can modify voluntary intake of forage depending on changes in digestibility and palatability of the diet (Bocquier et al, 1987;Orr and Treacher, 1984;Orr et al, 1985).…”

The performance of ewes offered diets containing different proportions of perennial ryegrass and white clover silage in late pregnancy

“…There has been a consistent pattern for intake to be reduced as number of foetuses carried increased throughout a series of experiments, which have quantified the intake of conserved forages and the substitution between forage and supplements by ewes in late pregnancy Orr et al, 1985). In this experiment the proportional reductions in intake were 0-98 for twins and 0-85 for multiples compared with ewes carrying singles, which were very similar to the previous studies with hays and grass silages.…”

“…After lambing, the ewes were housed in groups and given a common ration to achieve about the same level of nutrient intake as in previous experiments Orr, Treacher and Mason, 1985) to measure residual effects of the pregnancy treatments. Ewes carrying singles or twins reared their own lambs and those giving birth to three or more live lambs (designated multiples) reared their two heaviest lambs.…”