A general purpose controlled release (CR) intra-ruminal device (CRD) containing chromium sesquioxide (CrrO.) was used to measure mean daily fecal dry matter excretion (FE) For personal use only.

Four supplementation treatments to investigate wet seasons responses were imposed on eight Brahman/Shorthom cross herds totalling 870 animals of all classes (cows and calves, bulls, heifers and steers). They grazed 12,300 ha of native pasture in the Darwin district of the Northern Territory. The treatments were: (i) control (no wet season supplement), (ii) Mineral (Ultraphos - supplementation with 13 minerals during the wet season), (iii) +Protein (Ultrapro-50 - the same 13 minerals plus non-protein nitrogen (WN) and true protein over the wet season), and (iv) Strategic (strategic use of salt, mineral and hTN supplements over the early wet, mid wet and late wet seasons respectively). All treatments received an hTN plus mineral supplement (Uramol) during the dry season. Supplement intakes by the herds were measured monthly for three years. Intake of Salt, Ultraphos and Ultrapro-50 supplements averaged 43, 124 and 149 g/animal/day respectively during the three wet seasons. Losses of the molasses-based block formulations due to rain were small (7%) during the wet season. However, up to one third of each pure salt block was eroded. Intake of Uramol during the three dry seasons averaged 182 g/animal/day across all herds. No urea toxicity problems were noticed over the three years of the supplement programme, despite high intakes during the dry season. All animals consumed some supplement. However, levels of supplement intake: (i) increased with the seasonal decrease in native pasture quality, (ii) decreased with an increase in proportion of paddock burnt, (iii) varied between animal classes, with lactating cows consuming 64% more supplement than non-lactating cows in two of the three years, and (iv) varied between individuals within classes. Individual intake varied widely (from 10 to 835 glanirnallday for lactating cows) with no significant correlation between individual intake and the pregnancy rate or average daily liveweight gain.

The effects of including monensin in the diet on the dynamics of protozoa in the rumen of sheep were investigated using injections of protozoa labelled with 14 C-choline.The half time of rumen fluid was higher in sheep receiving monensin but neither the pool size nor the composition of protozoa species (mainly smaller entodiniomorph ciliates) was significantly affected.More protozoa passed out of the rumen as liquid outflow rate increased and there was a tendency for the apparent production rate of protozoa to be higher with the resulting increase in washout of protozoa.

No abstract

Experiments were undertaken to examine the comparative toxicity to sheep of ammonium sulphate and urea given as single doses and the value of ammonium sulphate fed alone or in combination with urea as a supplement to low nitrogen roughages. Ammonium sulphate dosing produced significantly lower mean blood ammonia levels than urea dosing. Fifteen grams of nitrogen as ammonium sulphate were tolerated as a single dose but the equivalent level of urea was toxic. lnappetance and ruminal stasis was noted when sheep fed a low nitrogen roughage (0.5 per cent nitrogen) received ammonium sulphate supplement as the sole non-protein nitrogen source. Ruminal stasis and inappetance may have been due to sulphide toxicity. Ammonium sulphate when used at lower levels in varying combinations with urea was well utilized as a nitrogen and sulphur source even when supplying 50 per cent of the supplemented nitrogen.