Heifer Groups Research Articles

The effect of multiple rapid passage on strains of Babesia divergens: A comparison of the clinical effects on juvenile and adult cattle of passaged and irradiated parasites

Two groups of 5 16–18-month-old female cattle and 2 groups of adult cows were infected with 10 4 erythrocytes containing isolates of Babesia divergens which had been rapidly passaged through splenectomized calves 6 or 15 times. Simultaneously, a further group of 5 adult cows were given 10 9 erythrocytes infected with the strain passaged 15 times but which had in addition been subjected to 30 kilorads of irradiation. The clinical reaction in both heifer groups was of a similar nature and much less severe than that produced by the same parasites in the adult cows. It was apparent that the number of rapid passages used had produced little or no reduction of virulence to adult cattle, and had much less effect on the outcome of infection than had the natural resistance of younger animals. After a prolonged incubation period the irradiated parasites also produced severe clinical disease in the cows, indicating that although almost all the B. divergens (approximately 99·99 per cent) had been inactivated by gamma irradiation, enough viable parasites had survived to initiate an infection able to overcome any resistance produced by the simultaneous inoculation of large numbers of killed parasites. We concluded that a live vaccine for B. divergens produced by passage or irradiation of infected blood is unlikely to be a viable, practical or commercial proposition for adult cattle.

The composition, fat distribution and yield of carcass beef from steers and heifers when entire, spayed, pregnant or fitted with an intravaginal device

An experiment at the Pastoral Research Institute, Hamilton, compared the carcass composition and yield of one group of 14 Hereford steers, and four groups of 14 heifers, either spayed, fitted with an intravaginal device, pregnant or entire. The animals were slaughtered at 18 or 22 months when average fat depths and carcass weights were 5.8 mm and 188.0 kg, or 7.5 mm and 219 kg, respectively. When compared at a constant carcass weight, the steers generally had heavier boneless primary cuts, with less fat than the heifers (P<0. 05). Steers also had less channel and kidney fat, subcutaneous fat, intra-muscular and inter-muscular fat and consequently less total fat than heifers (P<.05) . Differences between heifer groups were generally small and non-significant. When compared at the same age, differences between heifers and steers in carcass fatness were generally not significant (P>0. 05) but trends similar to those described above were apparent. Estimated yield of carcass beef (muscle plus saleable fat) was affected by sex, fat depth and level of fat specified in the carcass beef. When lean carcass beef (1 5% fat) was specified, steers yielded about 3.8% more than heifers at the same weight and fat depth, but when fatter carcass beef (20% fat) was specified, this difference was reduced to about 3.2%. Removal of channel and kidney fat from the carcass brought the yield of steer and heifer carcasses to within about 3.0% of each other.

EPIMYSIAL CONNECTIVE TISSUE POLYSACCHARIDES OF BOVINE SEMIMEMBRANOSUS MUSCLE AND ALTERATIONS IN THEIR TYPE WITH AGE AND SEX DIFFERENCES

ABSTRACT— Newborn veal, 11.5‐month‐old steers, 14.5‐month‐old heifers and 9 to 10.5‐year‐old cows were used to identify the polysaccharide types present in the epimysium and to determine the relationship between the amount of connective tissue polysaccharides and the amount of collagen in the epimysium. Trimmed muscle was used for tenderness evaluation by shear force. Average amounts of 332, 247, 230 and 202 mg dry polysaccharides per 100g dry, defatted epimysium were isolated from the veal, steer, heifer and cow groups, respectively. A negative correlation was obtained between age of animals and amount of isolated polysaccharides. Only 20% of the hexosamine in the dried defatted epimysium was extracted as soluble connective tissue polysaccharides. It is possible that some selective solubilization of certain polysaccharides occurred during extraction and, consequently, the extracted polysaccharides may not reflect the actual polysaccharide composition of the intact tissue. Considering this, it was found by using Dowex 1 x‐2 chromatography that an average of 42% of the total uronic acids of the veal and heifer groups was eluted with 0.5M NaCl. 17 and 19% of the cow and steer uronic acids, respectively, were eluted with 0.5M NaCl. In the veal and heifer groups, 37 and 38% of the total uronic acids were eluted with 1.5M NaCl, whereas in the cow and steer groups the amount represented 71 and 70%. The percentages of uronic acids eluted with 2.0M NaCl were 20, 11, 19 and 12% in the veal, steer, heifer and cow groups, respectively. Dermatan sulfate was found to be the main polysaccharide eluted with 1.5M NaCl for the veal, heifers and cows. It also represented an important type in the steers, although other sulfate polysaccharides seemed to be present. Cellulose polyacetate electrophoresis confirmed that hyaluronic acid and dermatan sulfate were present in the epimysium. The ratio of hexosamine to insoluble collagen in the epimysium was positively associated with muscle tenderness.