Growth and carcass characteristics of beef-cross-dairy-breed cattle : breed and sex effects : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Animal Science, Massey University, Palmerston North, New Zealand
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Date
2021
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Massey University
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Abstract
Approximately two thirds of New Zealand’s annual cattle slaughter originates from the dairy industry in the form of cull cows, bobby calves and calves retained for beef finishing. Bobby calf slaughter for pet food and veal is a system of low production efficiency, making up 41.1% of the annual cattle slaughter on a per head basis, but comprising only 4.3% of the total annual carcass weight produced in New Zealand. These underutilised surplus calves provide an opportunity to increase beef production by finishing them at either the traditional slaughter age of around 24 months, or in a novel yearling system finishing cattle before 12 months. This study aimed to investigate different factors influencing the performance of beef-cross-dairy-breed cattle through two separate experiments. The objective of the first experiment (chapter 3) was to investigate the effect of dam breed from dams with varying proportions of Friesian and Jersey genetics on growth traits and carcass characteristics of their dairy-beef progeny slaughtered between 24 and 30 months of age. The primary objective of the second experiment (chapter 4) was to investigate the effect of sex on carcass and meat quality characteristics of 11- month-old Stabilizer-Friesian-Jersey heifers and steers. The first experiment involved 142 heifers and 203 steers born in the spring of 2018 to Friesian (F), Friesian-cross (FX), Friesian-Jersey (FJ) and Jersey-cross (JX) cows. Calves were artificially reared before drafting into four management herds and were slaughtered between October 2020 and March 2021. Calves from F dams took less time to reach a set weaning weight (100kg), and had greater live weights throughout the study than those from other dam breeds. Carcass weights were greater for progeny from F dams (286kg) than those from FX (297kg), FJ (275kg) and JX (276kg) dams. Yellow fat score was greatest for progeny of JX dams (3.33) than for progeny of F (3.01), FX (3.04) and FJ (3.05) dams. The frequency of yellowness scores of ≥ 5 (on a 1-9 scale) was also greatest for progeny of JX dams (17.1% compared to 2.6%, 5.6% and 9.2% for progeny of F, FX, and FJ dams, respectively). Therefore, calves from dams with a greater proportion of Jersey genetics will have lower live and carcass weights and yellower fat than those from dams with a greater proportion of Friesian genetics. The second experiment involved 24 Stabilizer-Friesian-Jersey cattle (12 heifers and 12 steers) born in the spring of 2018 and artificially reared before finishing as one herd until slaughter at 11 months of age. The Stabilizer is a four-breed composite comprising 25% each of the Angus, Hereford, Simmental and Gelbvieh breeds. Carcass weight and dressing out was greater for steers (157kg and 48.6%) than heifers (148kg and 47.1%). Heifers had a greater muscle to bone ratio (7.76) than steers (7.09). Cooking loss was greater in heifers (37.8%) than in steers (35.6%) but all other meat quality characteristics were similar between the sexes. Therefore, meat from yearling beef-cross-dairy-breed heifers and steers could be classed as one product. Aging decreased shear force of meat (4.65kg for aged compared to 5.51kg for unaged). Unaged beef was still highly tender, suggesting that aging was unnecessary to provide tender beef.