Feed, N and P utilisation of Brown Swiss heifers in comparison with Angus and Simmental suckler cows with their progeny grazing mountain pastures

Abstract. The aim of the present study was to compare intake and nutrient turnover in two major production systems on mountainous pastures, suckler beef production and rearing of heifers. Data from 4 × 6 Angus or Simmental suckler beef cows with Angus sired calves were opposed to those measured in six growing Brown Swiss heifers applying a contrast model. In each of two vegetative seasons (years A and B) animals were kept together on three mountainous pastures, P1 (1 000 m a.s.l.), P2 and P3 (both 2 000 m a.s.l.), providing either first growth (P1, P2) or re-growth herbage (P3). Intake and herbage digestibility were estimated by the double alkane indicator technique. On average of the two years, the cows together with their progeny weighed 741 kg and the heifers 374 kg. The average daily body weight gain in beef calves (1 044 g) was twice of that measured in the heifers (546 g). Body weight of the cows remained quite constant on average. Dry matter intakes were 17.0 and 8.2 kg/d, and 118 and 96 g/kg^0.75 body weight in suckler cows with progeny and heifers, respectively. On all pastures, cattle of both categories selected herbage of similar energy and protein content. Digestibilities of organic matter (73–74 %) and fibre (NDF, 69 %) were similar between categories, though differing among pastures. Nitrogen utilisation was equal in both categories (8 % of intake), but varied among pastures (11 %, 8 % and 5 % on P1, P2 and P3, respectively) and years (11 % and 6 % in years A and B) due to different herbage N contents and intakes. When related to intake, also excretion of faecal and urinary N was equal in both categories. Faecal P losses relative to weight gain were similar in both categories but differed between pastures and years. The results demonstrated unexpectedly similar nutrient use efficiencies and relative N and P losses of the two livestock system options currently common in utilising of mountainous pasture.