The establishment and evaluation of an assessment system to accredit sonographers for measuring the carcass traits of subcutaneous fat depths and longissimus muscle area (LMA) on potential breeding animals by real-time ultrasound is described. Repeatability of operators, variation between the animal's left and right sides, and variations in technique were assessed from measurements and repeat measurements of 30 cattle by up to eight operators at three testing sessions. Accuracy of carcass data was determined by repeatability of measurements, variability between measurers, between left and right sides of the carcass, and variation due to handling and dressing procedures. Correlations with carcass data averaged .92 for rump fat, .90 for rib fat, and .87 for LMA. Residual SD averaged .81 mm, .88 mm, and 5.1 cm2. A very experienced sonographer can measure LMA only marginally less accurately than it can be measured on the carcass. In Session 3, the SE between repeat fat measurements for accredited sonographers averaged .43 mm, indicating that fat depths can be measured more accurately, but when comparing measurements from different operators, adjustments may be required for differences in technique, otherwise overall accuracy will be about the same, approximately 1 mm. Scanned rump fat measurements were consistently approximately 20% higher than on the chilled, hanging carcass 24 h after slaughter; after applying the standard correction factor of 1.17, LMA measurements were similar. Scan and carcass rib fat measurements were similar for animals with less than or equal to 10 mm of fat cover, above which carcass measurements tended to be higher.
Ultrasound measurements by trained and accredited sonographers on 9,232 Angus, Hereford, and Polled Hereford cattle at an average age of 450 d were used to estimate genetic and environmental (co)variances for weight at scanning (Wt), longissimus muscle area (LMA), longissimus muscle area adjusted to a constant weight of 400 kg (LMAawt), and fat depths at the rump and 12/13 rib sites. Estimated kilograms (ESMkg) and percentage of saleable meat yield (ESM%) were also calculated and analyzed. Subjective muscle scores, available for 2,488 animals, were also included in the analysis. Estimated heritabilities were 46% for Wt, 21% for LMA and LMAawt, 37% for rump fat, 30% for rib fat, 15% for muscle score, 44% for ESMkg, and 36% for ESM%. The two measurements, LMA and LMAawt, had high genetic (.82) and environmental (.91) correlations. The two fat depths were also highly correlated (.86 genetic; .67 environmental). Weight at scanning was moderately correlated with LMA (.45 genetic; .41 environmental). Differences between breeds could not be detected, but some variation in parameter estimates between data sets of the same breed was observed. Environmental correlations between fat depths or muscle score and Wt were approximately .3; genetic correlations were .07 to .12. Subjective muscle score had marginally higher genetic correlations with LMA than with LMAawt (.22 vs .08) but similar environmental correlations (.31 vs .27). Results show that carcass traits measured by ultrasound and predictions of meat yield have genetic variability, are moderately heritable, and that genetic progress based on genetic evaluation by mixed-model analysis can be made.
Sheep from different farms (lines) in Western Australia were mixed in 3 experiments and lot-fed for 6-7 days as if for export. A marking method to identify sheep which eat from troughs was tested and used to examine the effects of feeding treatments on the proportion of sheep which eat during lot-feeding. Paint soaked sponges attached to troughs were used to monitor whether sheep ate. Positive linear relationships between liveweight change and paint marking score (R = 0.93, 0.93 and 0.94, in the 3 experiments) suggested that the technique was a reliable indicator of feed intake. Feeding treatments imposed were period of fasting before lot feeding (experiments 2 and 3); and diet type (hay pellets, hay/pellet mix) and trough location in the feedlot (experiment 3). There were large differences between lines in the percentage of sheep not marked. Values � s.e. ranged from 1 � 1 to 79 � 3% for the 8 lines used in 3 experiments. In experiment 2, fasting for 48 h before lot-feeding resulted in more sheep (P<0.05) not marked (18 � 7 3%) than did fasting for <12 h (9 � 3%) and <24 h (8 � 2%). In experiment 3, fasting for 96 h compared with 48 h resulted in fewer sheep marked daily when fed a hay-pellet mixture (75 � 2 v. 93 � 1%; P<0.001). When fed only pellets in experiment 3, the percentages of marked sheep increased with time (days). Feeding pellets only compared with a hay-pellet mixture resulted in fewer sheep marked daily (60 � 2 v. 79 � 2%; P<0.001) and more sheep not marked (11 � 3 v. 3 � 2%; P<0.05). If troughs were located in the centre of yards instead of on the fenceline, it took 2 rather than 7 days for the daily percentage of animals marked on the pellets only diet to exceed 80%. The central location also resulted in a mean of 78 � 2% of sheep marked daily compared with 67 � 2% for fenceline troughs (P<0.001) and a mean intake higher (P<0.01) by 0.13 � 0.04 kg/wether.day. It was concluded that line of sheep, fasting, diet and trough location all had significant effects on feeding behaviour during lot feeding. Of these treatments, the greatest variation in feeding behaviour was associated with the line of sheep.
Groups of 10 Merino weaners or hoggets were offered ad libitum 1 of 5 grain mixtures: oats alone (9.1% crude protein, CP), oats mixed with lupins (CP 12 or 15%), and oats sprayed with a urea solution to increase total nitrogen to an equivalent of 12 or 15% CP. In experiment 1, each grain mixture was fed with 10% milled cereal hay to sheep in pens for 98 days; in experiment 2 the sheep grazed wheat stubble for 84 days. In experiment 1, the liveweight gains of weaners and hoggets fed the lupin or urea mixtures were greater by 53-69% and 58-120�/o, respectively, than the daily 9.4 and 54.1 g/head gained on oats alone (P< 0.05). In experiment 2, liveweight gains of sheep fed these mixtures were, with 1 exception, greater by 95-1 54% than the 69.0 and 58.3 g/head gained daily by sheep fed oats alone (P< 0.05). Addition of urea to oats at the higher level (15% CP) tended to depress intake and liveweight gain, compared with the 12% CP level, and the effect was greater among hoggets. Wool production paralleled feed intake and liveweight gain. It is concluded that the daily growth rates of 90 to 130 g/head resulting from treatment of oats with up to 1.5% urea can be similar to those from oat-lupin mixes of equivalent CP (daily 85-150 g/head).
Sheep are assembled in Australian feedlots before export and given time to adapt to the pelleted diet they will receive on board ship. In Western Australia, lupins are normally included in the diet at levels up to 30% as a source of digestible energy which is low in starch. It is also common to feed hay during assembly. We examine the use of pellets based on barley and containing either lupins or virginiamycin to overcome problems of acidosis, and the importance of hay during assembly. There were 9 dietary treatments each with 3 pens of 30 sheep. The study was conducted over 8 days simulating assembly feedlot conditions. Measurements were made of numbers of sheep visiting troughs (paint-marking technique) and accumulation of lactic acid in the rumen. 'Barley' pellets were formulated with 33% barley, 18% oats, 47% hay/straw and 2% minerals and vitamins. Replacing about half of the barley with lupins resulted in more sheep paint-marked on days 3-6 (P<0.05) and higher levels of feed intake on days 4-8 (P<0.001) than feeding pellets without lupins. The inclusion of lupins was also associated with a less pronounced drop in feed intake on day 4 than measured in sheep fed barley pellets alone. Adding virginiamycin at 40 g/t to the basal barley-based pellet also significantly increased the numbers of sheep paintmarked. Virginiamycin appeared to have a similar effect to the inclusion of lupins in terms of reducing the number of sheep which were not paint-marked. Sprinkling a small quantity of lucerne chaff onto the pellets had no effect on feeding behaviour. The use of hay in racks resulted in fewer sheep (3 v. 12%, P<0.05) not eating during the first 3 days but there was no significant effect thereafter. We concluded that the inclusion of either lupins or virginiamycin is effective in improving the adaptation to cereal-based pellets in export feedlots. The use of hay either in racks or sprinkled over the pellets appears to be of limited value.
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