R. A. Barton

Carcass characteristics of Southdown rams from high and low backfat selection lines

Abstract Carcass characteristics of Southdown rams from lines selected for high or low backfat depths (assessed ultrasonically at Position Cover the longissimus dorsi muscle at the last rib) were compared. Rams were 15-18 months old and average carcass weight was 29.5 kg fot the High-line (n = 36) and Low-line (n = 42) groups. When adjusted by covariance to the same carcass weight, animals from the High-line had higher dressing-out percentages, lighter weights of several internal organs, and shorter carcasses. At a constant side weight, the High-line sides contained 18% more dissectible fat and significantly lighter weights of muscle and bone. However, muscle to bone ratio and muscularity in terms of muscle weight per unit length were greater for the High-line group. The High-line carcasses contained a greater proportion of their weight in the rack and loin cuts. The greater weights of four dissectible fat depots in the High-line carcasses were the result of larger rather than more adipocytes. The results...

A note on liveweight gains of sheep grazing different ryegrass pastures

Abstract Three trials are described in which the liveweight gains, of sheep grazing different strains of ryegrass with and without white clover were compared. In the first trial, the pastures were: perennial ryegrass (P), perennial ryegrass plus white clover (P + C), short-rotation ryegrass (S), and short-rotation ryegrass plus white clover (S + C). The ranking of the pastures in order of decreasing liveweight gains was: S + C, P + C, Sand P. In the second trial, the pastures investigated were: Ariki ryegrass (A), Ariki rye grass plus white clover (A + C), P and S. A + C gave the greatest liveweight gain, followed by S, while A was intermediate between Sand P. The pastures in the third trial were: A, P, A + C, and Italian rye grass (I). I gave the greatest liveweight gain, followed by A + C. P and A, which were similar, gave the poorest liveweight gains, A separate comparison indicated no difference in liveweight gains between I and S.

Meat quality and muscle fibre type characteristics of Southdown Rams from high and low backfat selection lines.

Characteristics of the meat of 15-18-month Southdown rams from lines selected for high or low backfat depths (assessed ultrasonically at position C over the last rib) were compared. Half of the carcasses were electrically stimulated (ES) and within each carcass post-mortem treatments chosen to produce effects on meat tenderness were ageing periods of 1 or 15 days (Semimembranosus), early or delayed chilling (Biceps femoris), and trimming of the s.c. fat cover (Longissimus dorsi). These treatments had the expected effects on shear values, but the sizes of the effects were little affected by selection line or ES treatment. Selection line did not have any direct effects on shear values, reflectance values at several wavelengths, waterholding capacity, cooking loss or sarcomere length. The Semitendinosus muscle had a higher proportion of predominantly oxidative fibres for the high-backfat line, based on succinic dehydrogenase activity (P < 0·05), but there was no line difference in alkaline-stable ATPase activity in the same muscle. Muscle fibre diameter was similar for the two lines.

The tenderness of meat of several breeds of cattle raised under New Zealand pastoral conditions

Abstract Three experiments are reported in which the tenderness of meat from 171 steers of 6 breeds (Angus, Friesian, Jersey, Ayrshire, Galloway, and Red Poll) was measured as shear forces. Generally, differences between breeds for meat tenderness were not statistically significant, although the meat of Jersey cattle was significantly more tender than that of some other breeds in one experiment, an effect which is consistent with overseas evidence. Some significant breed effects were shown on the way in which post-mortem treatments, such as aging and pre-rigor storage temperature, affected meat tenderness. Other measurements made on the muscles of some of the steers indicated that Jersey cattle had the highest level of intramuscular fat in one experiment, but there were no appreciable differences in sarcomere length or muscle pH between breeds of cattle.

Post-parturn oestrous interval of single-suckled Angus beef cows

Abstract Some factors that may influence the interval from calving to first post-partum oestrus in 61 single-suckled Angus cows calving in the spring of 1975 were investigated. The overall least squares mean for this interval was 79.2 days. Calving date significantly (P < 0.01) influenced this interval, but the effects of management group, age of dam, sex of calf and post-calving nutritional treatments were non-significant. Milk production of the dam, as assessed by the weigh-nurse-weigh method, was correlated (P < 0.05) with post-partum interval at 20 days (r = 0.25), but not at 40 or 60 days. The mean calving interval for the herd was 367.6 days, calving interval being correlated (P < 0.05) with post-partum interval to first oestrus (r = 0.29). It was concluded that attention should be given to pre-calving nutrition, but during the first 40 days post-partum, cows can be fed to maintain their live weight without detriment to their reproductive performance.

Comparison of the carcass characteristics of steers of different breeds and pre‐weaning environments slaughtered at 30 months of age

Abstract The carcass composition (dressing‐out percentage, kidney and channel fat, fat depth at the 12th rib, eye muscle area, and trimmed fat, bone, and muscle weight) of 30‐month‐old beef‐type steers [Angus (71), Beef Shorthorn (28), Galloway (29), Hereford (15), and Red Poll (14)] and dairy‐type steers [Friesian (72), Milking Shorthorn (29), Ayrshire (30), and Jersey (29)] were studied over 5 consecutive years. Animals were selected for the trials after weaning and were grazed on pasture with occasional supplementation. The dairy‐type steers had lower dressing‐out percentages, heavier kidney and channel fat, lower fat depths at the 12thrib, and heavier bone weights than the beef‐type steers. The difference between bone weight and lean weight was the best linear function of the carcass parameters to discriminate between dairy‐type and beef‐type breeds. There were significant between‐year differences in fat variables and in eye muscle area, but not in bone weight and lean weight. There were positive rela...

Composition of lamb carcasses and cuts of the New Zealand export grades

Abstract Physical and chemical composition and carcass measurements were determined on a total of 126 lamb carcasses from nine New Zealand export grades (seven wether and seven ewe carcasses per grade). In general, carcasses of the Down (Prime Down Cross) and Prime (Prime Crossbred) grades of comparable weight were similar in composition, while carcasses of the Y (Second or F.A.Q. — fair average quality) and Alpha grades contained more lean and bone and less fat and had more protein and moisture and less chemical fat than the carcasses in the Down and Prime grades. Ash patterns were not consistent. Mean external and internal measurements showed that angular carcasses of the Y grades were longer and generally narrower in the forequarter, and had smaller and shallower ribeyes than the blockier carcasses of the Down grades.

Comparison of Friesian, Friesian‐Jersey‐cross, and Jersey steers in beef production

Abstract An account is given of the rearing in one unit of 274 Friesian, Jersey, and Friesian‐Jersey‐cross male calves and of their subsequent growth to approximately 22–23 months of age. A sample of the 10 heaviest of each breed group was selected for slaughter at 22–23 months of age. The Friesian steers in this sample were 6.8% heavier than the Jersey steers. Their heavier carcass weight and higher grades gave them a monetary advantage of

Growth and carcass characteristics of crossbred steers out of Jersey cows

NZ9.42 over the average Friesian‐Jersey‐cross carcass and an advantage of

Repeatability of weight-corrected ultrasonic fat-depth measurements made on ewes at intervals of one year

NZ32.36 over the average Jersey carcass. The proportional composition of boneless, fat‐trimmed meat, fat trimmings, and bone in the side did not differ between breed groups. However, the proportion of hindquarter boneless, fat‐trimmed meat to total meat in the side was significantly lower by 1.1% for the Jersey group and by 0.8% for the Friesian‐Jersey group compared with the Friesians. The boneless, fat‐trimmed meat production per day of age was highly significantly different at 0.12,0.09, and...