Meat quality of light-weight, dairy origin yearling steers
Consumers and the general public are becoming increasingly concerned about animal welfare issues. One such issue is the slaughter of surplus/unwanted “bobby calves” generated by the dairy industry. These calves, which are considered unsuitable as dairy replacements or are traditionally not reared for beef production (i.e. Jersey crosses) are considered by some a “wasted resource”.
A question frequently asked is “surely there must be a better use for these animals?”.
It is proposed that a new beef production system could be developed, which would better utilise these animals and transform them into high value beef products. The novel aspect of a ‘New Generation Beef’ finishing system is that cattle would be finished by 1 year of age.
This week we have our guest writer Sam Pike who is currently working as a Research Assistant at Massey University specialising in sheep and beef production, and nutrient management.
Objective measures of meat quality indicate that the yearling beef is lean but very tender and likely to be of high eating quality.
Processing ages of 8, 10 and 12 months resulted in minimal differences in shear force values and lean meat colour.
Beef obtained from steers slaughtered between 8 and 12 months of age could be classed and processed together under 1 category.
Currently, most cattle finished for beef production in New Zealand are not processed until between 18 and 36 months of age. A yearling system would allow a greater turnover of animals which could reduce bobby calf numbers significantly, whilst also providing an opportunity to create a higher value product from these animals.
Because dairy-origin yearling beef is a new concept in New Zealand, a pilot study was undertaken in order to understand the type of meat product that could be obtained, and if there could be some flexibility in terms of slaughter age whilst still delivering a consistent product.
Sixty Hereford x Friesian-Jersey steers were obtained at weaning (103 kg live weight) and randomly allocated to three slaughter treatment groups of 8, 10 and 12 months of age. Due to the unique size of the animals, the steers were processed through a venison plant to minimise safety and animal welfare issues.
As expected, final live weights, carcass weights and dressing-out percentages increased progressively with age. Carcass weights at 8, 10 and 12 months of age were 119 kg, 146 kg and 174 kg respectively, with dressing out percentages of 47%, 49% and 50%.
But how does the meat look and taste?
Objective meat quality attributes were measured on the striploin – the muscle more commonly known by consumers as sirloin or porterhouse steak. Ultimate pH is an important attribute as it can influence other characteristics such as tenderness, colour and juiciness.
Interestingly, ultimate pH for steers slaughtered at 8 months of age was 5.3, which is well below the normal range of 5.5 – 5.6. Steers slaughtered at 10 and 12 months of age were within the normal range. A lower pH is often associated with improved tenderness and also produces lighter coloured meat.
Meat tenderness was assessed using the Warner-Bratzler shear force method. This test measures the amount of force required to cut through a cylindrical core of cooked meat, with lower values indicating more tender meat.
The differences in shear force values between the 3 slaughter age treatments were not significant, with means ranging from 5.1 to 5.5 kgF. In comparison, peak shear force observed in a similar recent study by Coleman et al. (2016) from 24-month-old, beef-dairy prime steers averaged 9.6 kgF.
To give context to these values, shear force values above 10 kgF for beef are detectable to consumers as “tough”, while values below 8 kgF can be recognised by consumers as “tender” (Bickerstaffe et al. 2001).
It is common for beef to become less tender as cattle mature, as collagen (a structural fibre within meat) becomes less soluble and is not as easily broken down during cooking. This effect is clearly illustrated in Figure 1. The lack of differences in shear force values between 8 and 12 months of age was not expected, but, is likely a result of only a small age range being compared.
It is also worth noting that the low shear force values for the 8-, 10- and 12-month-old treatments were achieved with minimal intramuscular fat within the meat compared with beef from older animals. This suggests New Generation Beef could provide a very lean but tender product without the need for high levels of intramuscular fat, which is typically associated with premium, tender beef from older cattle.
Meat colour became darker and redder with age, as shown by a decline in lightness values (Figure 2, purple bars) and an increase in redness values (Figure 2, blue bars). This is commonly observed in age-related studies, and can be attributed to the increase in myoglobin concentration in the muscle as animals get older – the pigment responsible for the red colour of meat.
Objective measures of water holding capacity can indicate how juicy meat is likely to be. There was no clear trend for differences in water holding capacity between slaughter ages. Water holding capacity is influenced by carcass composition – particularly the relative proportions of lean muscle and fat in the meat. The meat obtained was very lean and carcass composition was likely similar between all treatments given there was only 4 months difference in age among treatments, which explains why there were minimal differences in water holding capacity among treatments.
The objective meat quality attributes measured in this study indicate that New Generation Beef is very tender and likely to be of excellent eating quality, despite being very lean.
In the future, a taste panel will subjectively assess the meat for tenderness, juiciness and flavour, to provide us with a better understanding of what eating experience New Generation Beef can offer, and which markets the product may be best suited for.
A modelling exercise has also been undertaken to assess the economic viability of the New Generation Beef system and how complimentary livestock classes could fit within a farm system.
With further research currently ongoing, New Generation Beef may one day be in a supermarket near you!
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BRIEF COMMUNICATION: Meat quality of light-weight, yearling steers of dairy origin, SJ, Pike, NM Schreurs, RE Hickson, JJ Hunt, PR Kenyon, DJ Garrick, HT Blair, and ST Morris, New Zealand Journal of Animal Science and Production, 2019, Volume 79, Palmerston North, p.156-158.