Kragvoer- tot ruvoerverhoudings in volledige rantsoene vir friesbulkalwers in 'n kalfsvleisproduksiestelsel

[摘要] English: An enormous potential for increased meat production exists in South African dairy herds. Dairy producers are often in doubt regarding the profitability of a veal production system. This is probably the most important reason why dairy producers are discouraged from rearing bull calves for veal production.This study was undertaken to determine the effecrt of various concentrate to roughage ratios on pre-weaning, as well as post-weaning growth, and veal production of Friesian bull calves.Twenty-four Friesian bull calves were randomly divided into three groups at an age of two days. All calves received whole milk at a rate of 10% of their initial body mass and were weaned at an age of 30 days. Complete rations, in milled form, were offered ad lib. from six days of age, and the following differences in concentrate to roughage ratios occured between the groups: 70:30; 77,5:22,5; 85:15. Water was freely available from six days of age. Crude protein content of all three rations was 18% until 12 weeks and 14% until 20 weeks of age. All calves were slaughtered at 20 weeks of age.At 10 weeks of age, all calves were subjected to a digestibility trial for a period of seven days. Apparent digestibility of dry matter, organic matter, ether extract, nitrogen-free extract, gross energy, as well as in vitro dry matter digestibility, gradually increased with an increase in concentrate content of the ration. No significant differences (P>0,05) in digestibility of crude protein and neutral detergent fibre (NDF) were detected between groups. An increase in concentrate content of the trial rations was accompanied by a highly significant (P<0,01) decrease in crude fibre digestibility. The apparent digestible crude protein- (%) and digestible energy content (MJ/kg) for the 70%-; 77,5%- and 85% concentrate rations were 12,60 and 13,27; 12,59 and 13,63; 13,19 and 14,58 respectively.No statistically significant (P>0,05) difference with respect to body mass gain occured between treatments. Except for one period (fourth month), no significant (P>0,05) differences in feed intake occured between groups. Feed intake tended to decline during both the pre- and post-weaning periods with an increase in concentrate content of the ration. Efficiency of feed conversion to live mass improved highly significantly (P<0,01) for the post-weaning period and significantly (P<0,05) for the total period as the concentrate content of the ration increased from 70 to 85%. There were no significant (P>0,05) difference in carcass mass and grading score between treatments. Dressing persentage was significantly (P<0,05) higher for the 85%- compared to the 70%- concentrate group.Where the purchasing price of maize was taken into account, gross margin was R112,52; R124,82 and R113,79 for the 70% - ; 77,5% - and 85% - concentrate treatments respectively. Where the net producer's price of maize was applicable, gross margin was R131,66; R145,57 and R134,98 for the 70%-; 77,5%- and 85% concentrate groups respectively.It was concluded that Friesian bull calves can be reared profitably for veal production at 20 weeks of age. Even at the current high prices of feed ingredients, promising gross margins are possible for veal production from dairy herds. The most economical results in this study realized with a concentrate to roughage ratio of 77,5 to 22,5.

[发布机构] University of the Free State