Weaner steers were fed to attain either fat score 1 or 2 by the time that they were 1 year of age. Animals at each fat score were then either slaughtered or fed ad libitum on a basal barley and hay diet containing 11% crude protein or similar diets supplemented by either urea, meat meal or sweet lupins to contain 13% crude protein in the dry matter. Those fed were slaughtered as they attained fat score 3. Compared with those starting at fat score 2, the yearlings at fat score 1 had the same daily feed intake and thus a 10% higher relative intake, grew 15% faster and required 11% less feed per kg liveweight gain. However, they required only 6% less feed per kg carcass weight gain, owing to their 1% lower dressing percentage. The diets supplemented with the three different sources of supplementary nitrogen gave similar improvements over the basal diet in intake, growth rate and efficiency, and there were no interactions between diet and fat score. It was concluded that both the National Research Council and Agricultural Research Council feeding standards underestimate the nitrogen concentration required in grain and hay diets to ensure maximum performance and efficiency by yearling cattle growing from 220 to 370 kg liveweight, and that supplements of either urea, meat meal or lupins providing an extra 2 percentage units of crude protein improve performance to a similar extent.
In each of 4 years, Shorthorn and Dairy x Shorthorn heifers were fed for moderate (55 to 101 kg) or slow (1 7 to 50 kg) growth from weaning at 7 months until joining at 15 months of age. Thereafter they grazed together on improved pasture in a 430 mm rainfall Mediterranean environment. Their performance was compared until their second calving and their calves' performance until weaning. The heifers that had grown moderately prior to their first joining had 25 to 73 kg higher average liveweight and 3 to 7 mm higher ultrasonic backfat reading during first joining, a 9% higher calving rate, 14 kg higher average liveweight but a 10% lower dystokia rate at calving, and 12 kg higher average liveweight and 1 mm higher ultrasonic backfat reading at their second joining, than those that had grown slowly. Survival of dams and calves, date of first calving, calf birth weight, second calving rate, intercalving interval and date of second calving were not significantly affected by the rate of growth prior to first joining. The effect upon dams' weight at weaning (moderate 11 kg higher than slow) was significant only at P< 0.1. Most aspects of performance differed widely amongst years, but significant year x growth interactions were only found for liveweight and condition of heifers at first joining, and for weaning weight of calf. The calves of moderately-grown heifers were of significantly lower mean weaning weight than those of the slowly-grown heifers, but only in those years when the mean mid-joining weight of the moderately grown heifers exceeded 315 kg. It is suggested that high fertility and satisfactory first calf growth are not incompatible provided that growth between the heifers' weaning and first joining is limited to that which results in a mean mid-joining liveweight not more than 20 kg higher than the target weight for 90% calving.
Liveweight responses to two levels of supplementary feeding were compared in young cattle grazing barley stubble or fed baled material in pens. Over the 58 d of the experiment, unsupplemented animals in pens lost 0.5 kg/d, those receiving the low energy-mineral supplement maintained their initial weight, and those receiving a moderate energy-mineral supplement gained 0.3 kg/d. In contrast, cattle grazing stubble did not show any liveweight response to supplementation, all three treatments gaining at 0.6-0.7 kg/d. Grazing cattle were apparently capable of selecting a diet of much higher quality than the leaf and stem material on offer. The results emphasize the need for caution in extrapolating, to the grazing animal, results obtained in pen-feeding evaluation of heterogenous materials such as crop residues.
In each of 4 years, drafts of Shorthorn and Dairy x Shorthorn heifers were run together and fed to grow either slowly or moderately from weaning at 7 months until joining for two months at 15 months of age. Thereafter they grazed together on improved pasture in a 430 mm rainfall Mediterranean environment. Their performance was compared until their second calving and their calves' performances until weaning. Year x breed type interactions were significant for most variables measured. Between their first joining and first calving, the fourth draft of Shorthorn heifers gained 59 kg less liveweight than the crossbreds, but there was little difference in liveweight gain between the breed types in the other three drafts. Survival of the fourth draft of Shorthorn dams and calves was also 32 and 42% lower than of crossbreds. Concurrently, the third draft of Shorthorns lost 21 kg more liveweight than the crossbreds between first calving and their second joining, but performed similarly or better in the other 3 years. The third draft of Shorthorns also had a 63% lower second calving rate than the crossbreds, but the previous drafts had a similar rate of second calving. The average weaning weights of the second and third drafts of Shorthorn calves were 37 and 34 kg lower, respectively, than the crossbred calves, but only 8 and 16 kg lower in the first and fourth drafts, respectively. The third draft of Shorthorn dams were 90 kg lighter at weaning than the crossbreds but the other Shorthorn drafts were only 20 to 29 kg lighter. The intercalving interval of the fourth draft of Shorthorns was 28 days longer than that of the crossbreds, but was similar to or 23 to 30 days shorter for the previous drafts. Superior performance of the crossbreds was most apparent in the year of lowest rainfall and pasture availability, during which the third draft suckled their first calves and were joined for the second time and the fourth draft calved for the first time. First calving dates of dairy crossbreds were 14 days later than those of Shorthorns if grown slowly before joining, but were similar if grown moderately. Crossbred dams suffered 11 and 25% more dystokia at first calving of the first and third drafts and 14% more if grown slowly, but not if grown moderately before their first joining. Birth weights of calves out of crossbred dams were consistently 2 kg higher than those out of Shorthorn dams. First calving rates of the two types of cattle were similar and high (about 90%).
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