No abstract

Abstract. Eight beef cattle breeds, Angus (A), Blonde d' Aquitaine (BA), Charolais (C), Czech Pied (CP), Hereford (H), Limousin (L), Piemontese (P) and Simmental (S), were analysed for the following calf traits: birth weight (BW), 210- and 365-day weight ( 210W, 365W) and average daily gains from birth to 210 days (ADG1), from 210 to 365 days (ADG2) and from birth to 365 days (ADG3). Phenotypic parameters were estimated by linear model procedures including the fixed effects of year of birth (1992–1998), herd, sex (male, female), calf number (single, twin), parity and random sire effects. Literature values of heritability estimates were used to derive genetic standard deviations and genetic range for comparison of genetic variation within and between breeds. The means of Blonde d' Aquitaine were highest for all growth traits except for BW, followed by Charolais and Simmental, then Angus, Czech Pied and Limousin with intermediate values and Piemontese and Hereford with lowest growth except for BW in Piemontese and ADG1 in Hereford. Blonde d' Aquitaine also showed high standard deviations for most growth traits except for BW, whereas for Limousin and Piemontese low standard deviations were estimated and for other breeds no consistent pattern was observed. Coefficients of variation were generally high for Hereford and low for Angus. Hypothetical frequency curves were used for comparison of genetic variation within breeds and between breeds. Comparison of extreme and average breeds showed ranges of genetic levels between 79 and 154 % of the average breed level thus indicating the large overall genetic variation for growth traits in beef cattle. Between-breed selection with immediate impact, but steady erosion by time, as well as within-breed selection with slow but steady increase and renewed variation should both be applied for optimal exploitation of genetic resources in the beef industry.

No abstract

An experiment was carried out on four dry Holstein cows fitted with rumen cannulas that were divided into two groups. The crossover design experiment was divided into 4 periods of 3 weeks. Each period consisted of a 17-day preliminary period followed by a 4-day experimental period. Cows were fed twice daily the total mixed ration based on maize silage and concentrate. Control cows (Control) received the basal diets while experimental animals (Yeast) received the basal diet supplemented with 3.0 g of live yeast (BIOSAF Sc 47, Lesaffre, France) at each feeding. During each experimental period ruminal pH and redox potential (Eh) were monitored continuously using a developed wireless probe. Further, in each experimental period five samples of ruminal fluid were taken at 6:30, 8:30, 10:30, 13:30 and 16:30 h to determine the content of volatile fatty acids, lactic acids and ammonia. On the last day of each period, blood samples were taken for determination of blood parameters and acid-base balance. Average daily dry matter intake throughout the experiment was 8.2 kg/day and was not affected by the treatment. The average ruminal pH in Control was 6.16 that was significantly lower than in Yeast, being 6.26 (P < 0.001). The diurnal pattern of ruminal pH showed a similar trend in both groups. Mean Eh in Control (-210 mV) differed significantly from Yeast (-223 mV, P < 0.001). The mean value of rH (Clark's Exponent) calculated for Control (5.33) was higher than that calculated for Yeast (5.09, P < 0.001). Total VFA concentrations were on average 40.8mM in Control and 57.2mM in Yeast (P > 0.05). Lactate and ammonia concentrations at individual sampling times and overall mean did not differ significantly between treatments (P > 0.05). Blood pH and CO 2 were not affected by the treatment.

No abstract