Untersuchungen zur Morphologie und Physiologie des perirenalen Fettgewebes beim Kalb und der Einfluß der Umgebungstemperatur auf seine Funktion1,2

Different modes of food restriction and compensatory growth in double-muscled Belgian Blue bulls: animal performance, carcass and meat characteristics

Fifty double-muscled Belgian Blue bulls were divided into five groups. The first group (control, CG) was given, on an ad libitum basis, a fattening diet based on sugar-beet pulp. In G2 and G3, fattening was interrupted 103 and 187 days, respectively after the beginning of the experiment, by approximately a 2-month period of food restriction during which the animals received a maintenance ration. The last two groups, namely G4 and G5, received for about 4 months a limited amount of the restriction diet to support growth of 0·5 and 0 kg/day, respectively, before being fattened as CG. The average daily gain was 1·48 kg/day in CG v. 1·33, 1·30, 1·43 and 1·61 kg/day during the period of ad libitum feeding in G2, G3, G4 and G5. Higher nitrogen (N) balance during compensatory growth in G2, G4 and G5 (78·8, 81·0 and 74·6 v. 53·3 g N per day in CG, P < 0·001) resulted mainly from a higher efficiency of N retention. In G3, however, compensatory growth was characterized by lower N digestibility and efficiency of N retention. Muscle proportion in the carcass was higher in G3 while fat plus connective tissue proportion was lower (P < 0·05). Muscle pH values in CG were lower than in the other groups (P < 0·01) but ether extract values were higher. The intramuscular fat of G2 and G3 was characterized by higher proportions of polyunsaturated fatty acids.

Effects on animal performance and fat composition of two fat concentrates in diets for growing-fattening bulls

Two experiments were carried out with growing-fattening bulls, offered a fattening diet based on concentrate and supplemented with soya oil or steam-flaked linseed. Soya oil (200 g/kg) was mixed with middlings (800 g/kg). Linseed (500 g/kg) and whole barley (500 g/kg) were steam flaked. The fat incorporation resulted in an increase of the ether extract content from 26·5 g/kg dry matter to about 45 g/kg. The incorporation of soya oil increased the average daily gain (P> 0·05). The saturated: unsaturated fatty acid ratio was reduced in perirenal fat due to an increase of oleic acid and a reduction of stearic acid. The inclusion of steam-treated linseed resulted in a lower slaughter weight (P< 0·05) and a shorter fattening period (P> 0·05). The fatty acid composition of perirenal fat was affected significantly: the concentrations of oleic, linoleic and linolenic acid were increased and the concentrations of myristic, palmitic and stearic acids were reduced. This resulted in a reduced saturated: unsaturated fatty acid ratio.

In a third experiment, samples of the two fat concentrates were incubated in nylon bags in the rumen. The ether extract disappearance was high with both concentrates. Furthermore, the fatty acid composition was altered to a large extent for soya oil while large proportions of unsaturated fatty acids were still present with steam-flaked linseed.

Compensatory growth in Belgian Blue bulls previously grazed at two stocking rates: animal performance and meat characteristics

A comparison was made between fattening systems with Belgian Blue bulls of the double-muscle type, in order to assess the reponse in terms of compensatory growth when the bulls were grazed at a high stocking rate. Two groups of eight bulls were grazed on Lolium perenne and Trifolium repens pasture during an initial period of 135 days (period I). One group grazed at a stocking rate of six animals per ha allowing for normal growth at pasture (NGP); the other group grazed at stocking rate of 10 animals per ha (low growth at pasture, LGP). Both groups were then finished indoors (period II) with a concentrate based on dried sugar-beet pulp. Eight control bulls were also fattened indoors on the concentrate diet during periods I and II (CG). The bulls were slaughtered according to similar finishing fattening state. Live-weight gains were 1·47, 1·10 and 0·52 kg/day (P < 0·002) during period I in CG, NGP and LGP groups respectively. Corresponding live-weight gains during period II were 1·22, 1·37 and 1·50 kg/day (P > 0·05). The LGP group had lower food conversion ratios, slaughter weights (P < 0·05) and dressing proportions (P < 0·01). The meat from the grazed bulls had lower cooking losses (P < 0·05) and tended to have lower drip losses (P > 0·05) and higher tenderness (P > 0·05). It also had a higher cholesterol (P < 0·05) content. Large differences were observed in the fatty acid composition according to fat location (subcutaneous, intermuscular or intramuscular). The proportions of mono and polyunsaturated acids were increased in the fats of the animals previously grazed (P > 0·05, P < 0·05).