EFFECTS OF GENDER AND BREED ON CARCASS COMPOSITION AND BEEF QUALITY
I.B. Mandell1, E.A. Gullett2, J.W. Wilton1,
J. Fitzgerald3 and J.R. Morris3
Performance testing of bulls is routinely conducted in North America to determine the genetic merit of future herd sires. Post-weaning growth rate, scrotal circumference, backfat thickness, and ribeye area are measured to aid producers in developing their breeding programs such that growth performance, reproductive soundness, and carcass composition will be optimized in the future progeny of selected herd sires. While backfat finish and ribeye area are important indicators for the ability of cattle to finish and muscle to achieve Agriculture Canada's "A" grade, the ability to fatten is only a moderate indicator of palatability attributes such as tenderness, flavour, and juiciness.
Optimizing palatability attributes is the driving force to maintain consumer demand for beef. An important question to answer is how information from bulls on performance tests can be related to their steer progeny in relation to the palatability attributes of beef. The purpose of this study was to examine gender and breed effects on carcass composition and palatability attributes of beef.
Materials and Methods
Two hundred and eighty head of cattle were purchased from Ontario producers with the following requirements: 1) either purebred Hereford or at least 7/8 Simmental; 2) from designated sires such that groups of 9 half-sibs per sire could be assembled; and 3) male calves born between February 1 and May 15, 1992.
Eight Hereford and 10 Simmental sire groups were assembled to examine within breed and between breed differences in growth performance, carcass composition, and beef quality in bulls at the Arkell Bull Test Station and in steers at Ridgetown College of Agricultural Technology. Bull calves were fed a completely pelleted diet containing approximately 63% TDN and were grouped such that 2 half-sibs per sire would be slaughtered at either 4, 7 or 10 mm backfat. Steer calves were fed diets based on whole shelled corn, alfalfa silage, and corn silage containing 64-78% TDN (growing phase) and 74-80% TDN (finishing phase) with 3 half-sibs per sire for each of two dietary energy contents.
Steers were slaughtered when they achieved 7 to 10 mm backfat. The endpoints were chosen with the realization that a certain percentage of Simmental bulls would not finish at their designated endpoints. Cattle were allocated such that all sires and breeds were equally represented on each diet and endpoint combination.
Bulls were slaughtered at the University of Guelph while steers were slaughtered at a commercial abattoir. Carcasses were federally graded and the left primal rib from each carcass was dissected at the Meat Wing, University of Guelph. Ribs 9 to 11 were dissected into lean, fat, and bone to determine body composition. Ribeye roasts from ribs 9 to 11 of each animal were aged for 7 days prior to being frozen. A ribeye steak from the 12th rib of each animal was saved for chemical analyses.
Ribeye roasts were evaluated by a 10 member trained taste panel under the direction of Dr. Gullett. The taste panel evaluated the roasts for: 1) softness, the force required by the molar teeth to compress the sample; 2) initial juiciness or the amount of moisture released from the meat; 3) tenderness, the force required to chew the sample after the initial compression (determination of softness); 4) juiciness, the amount of saliva absorbed during the mastication process; 5) beef flavour, the amount of full meaty flavour; and 6) time spent chewing, time needed to chew the sample completely for swallowing. Six roasts were evaluated each day by the trained taste panel.
Results and Discussion
All cattle averaged 233 days of age at start of the trial while average weights at start of the trial were 285 kg for Hereford bulls, 334 kg for Simmental bulls, 242 kg for Hereford steers, and 275 kg for Simmental steers. The trials were terminated after 312 days on feed for bulls and 305 days on feed for steers regardless of whether cattle had achieved their targeted endpoint.
In examining the results, we do not expect to see similar values for carcass and palatability traits between bulls and steers. Our interest is whether breed differences between bulls are repeated for steers so that we can use bull data from performance testing to predict traits for steers.
Breed differences in hot carcass weight of bulls was much larger than breed differences of steers (Table 1). The large difference in carcass weights between Hereford and Simmental bulls was caused by attempting to achieve an average gradefat of 7 mm across both breeds of bulls. However, Simmental bulls only averaged 4.4 mm of gradefat vs. 7.6 mm gradefat in Herefords. The slower rate of fattening in Simmental bulls resulted in longer time on feed and heavy carcass weights as the cattle continued to grow but not fatten. In contrast, Simmental steers were able to fatten so carcass weights were heavy but not as drastic as weights in Simmental bulls. The ability of Simmental steers to fatten is substantiated by lean and fat yield data which is based on dissection of ribs 9-11 of the primal rib. Lean yield of Simmental steers was lower than that of Hereford bulls while fat yield was higher. The limited ability of Simmental bulls to fatten is substantiated by high lean and low fat yields by dissection relative to Hereford bulls and to differences between Hereford and Simmental steers. The large ribeyes for Simmental bulls reflect the breed by gender difference in the ability to put on muscle in comparison to breed differences between steers.
With the exception of initial juiciness and juiciness, the trained taste panel found sensory attributes including softness, tenderness, beef flavour, and time spent chewing to be similar among beef from Hereford bulls, Hereford steers, and Simmental steers (Table 2). The similar findings between Hereford bulls and all steers occurred despite much lower concentrations of intramuscular or marbling fat in Hereford bulls relative to steers.
In contrast, intramuscular fat concentrations were similar between bulls yet taste panel findings were drastically different. The trained taste panel found beef from Simmental bulls to be not as soft, less tender and flavourful, and needing more chewing before swallowing than all Herefords or Simmental steers.
The similarities in tenderness findings between Hereford bulls and steers is reconfirmed by similar values for Warner-Bratzler shear which is a physical measurement of tenderness. Similarly, Warner-Bratzler shear score for Simmental bulls is high, reflecting the less tender beef found by the taste panel.
For initial juiciness, the trained taste panel rated steers to be more juicy than bulls while scores for the taste panel attribute, juiciness was highest for Hereford steers vs. bulls and Simmental steers. The lower taste panel findings for Simmental bulls relative to Hereford bulls and steers across both breeds may be due to limited finish in Simmental bulls. American findings suggest that 7.6 mm of finish is needed to ensure optimal palatability of beef. Since Simmental bulls were on test for up to 305 days in this trial, additional time on feed to achieve 7 mm finish would be impractical. A higher energy diet may not be effective and may have a negative impact on the health status of future breeding bulls.
The findings in this study suggest breed differences in carcass composition and palatability attributes among bulls are not necessarily repeated in steers. In regards to palatability attributes with Simmentals, information from bulls may not accurately reflect the future performance of their steer progeny but further studies on rankings of sires is needed.
Significance to the Industry
This work demonstrates that breed differences in carcass composition and palatability attributes between bulls may not be the same as in steers. Taste panel findings with Hereford bulls show that high concentrations of intramuscular fat are not necessarily needed for tender and flavourful beef. This work also demonstrates the need for more research to ascertain both between and within breed differences in palatability attributes.
The authors are grateful for financial support from
OMAFRA Red Meat II to support this work. The authors are indebted to Chris Haworth and his staff and to Sue Buttenham for their technical expertise in carcass evaluation, physical dissections, and conduct of the trained taste panel. The assistance of the staff at the Ridgetown Beef Centre and the Arkell Bull Test Station is also greatly appreciated.
1Yield data (lean, fat, bone) based on g dissected lean, fat, bone in the 10th-12th rib per 100 g weight of the 10th-12th rib.
1Palatability attributes: Softness (0, very firm to 10, very soft) = force required to compress a sample with the molar teeth; initial juiciness (0, very little to 10, very much) = the amount of moisture released from the meat after 5 chews; tenderness (0, very tough to 10, very tender) = the force required to chew the sample using 3 additional chews after initial compression; juiciness (0, very little to 10, very much) = the overall impression of moistness perceived in the mouth after 10 chews; beef flavour (0, very weak to 10, very intense) = the amount of full meaty flavour present after 8 chews; time spent chewing (0, very short to 10, very long) = time needed to chew the sample completely for swallowing.