Massey Documents by Type

Permanent URI for this communityhttps://mro.massey.ac.nz/handle/10179/294

Browse

Filters

1983 - 198912010 - 20172

Settings

Has files: YesSubject: search.filters.subject.Slaughter

Search Results

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Effect of slaughter age between 5 and 14 months on the quality of sheep meat with specific focus on collagen concentration and solubility : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Science in Animal Science at Massey University, Manawatu, New Zealand
    (Massey University, 2017) Mashele, Grace Arbogast
    In New Zealand, pasture-raised lamb is considered the highest quality sheep meat product while hogget is a downgraded product considered to be of poorer quality. The objectives of this study were to investigate the difference in meat quality between sheep slaughtered at 5, 8 and 14 months-of-age. This study also aimed to develop an assay to measure collagen concentration and solubility and to compare shear force to collagen concentration and solubility for meat from sheep slaughtered at 5, 8 and 14 months. Sixty Romney crossbreed rams born in the spring of 2015 were allocated to one of three slaughter age groups: 5-group (n=20), 8-months group (n=20) and 14-months group (n=20). The ram lambs were grazed together on perennial ryegrass-based pasture. At slaughter, the loin (Longissimus lumborum) from the left side of the carcass was excised, chilled for 24 hours and then frozen. Shear force, pH, colour, driploss, myofibrillar fragmentation index, sarcomere length, soluble collagen, insoluble collagen and total collagen were measured on the loin. Longissimus lumborum muscle from the 5-months group was darker (P=0.045) with higher pH (P<0.001) than 8 and 14-months groups. Longissimus lumborum muscle from the 14-months group was redder (P<0.001), yellower (P<0.001) with higher intramuscular fat (0.003), shorter sarcomere length (P<0.001), lower collagen concentration (P=0.020) and lower soluble collagen in percentage (P=0.007) and in g/100g fresh weight (P=0.008) than 5 and 8-months groups. The peak shear force was lower at 14 months, intermediate at 5 months and greater at 8 months (P<0.001). Longissimus lumborum muscle from the 8-months group had greater drip loss (P<0.01) than 5-months group and 14-months group. The results suggest that slaughtering sheep at 14 months could have benefits on eating quality due to an increase in intramuscular fat.
  • Thumbnail Image
    Item
    Preslaughter and slaughter factors affecting meat quality in lambs : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Veterinary Pathology and Public Health at Massey University
    (Massey University, 1983) Petersen, Gunner Vindelev
    A plug sampling technique based on a modified muscle biopsy instrument, was developed for the measurement of muscle pH without mutilation of the carcase. It was found possible to routinely obtain muscle tissue samples weighing approximately 2 g and when these were incubated for 24 hours under liquid paraffin at room temperature, followed by homogenisation in a 'Colworth Stomacher', the pH of the solution was found to be an accurate measurement of the ultimate pH of the muscle. Both the sample method and a direct probe method were found to be well suited for measuring the ultimate pH of muscles. However, the sample method had a higher degree of precision as compared to the probe method when used for measuring pre-rigor pH values. In a longitudinal survey, in which 1536 lamb carcases were examined, 85.2% of carcases were found to have ultimate pH values below 5.80. Highly significant associations were found between season (summer period) and breed (Perendales) and unsatisfactorily high values of ultimate pH. There was also a highly significant direct correlation between the duration of holding periods of lambs and the ultimate pH of meat, whereas there was a highly significant inverse correlation between wool score and ultimate pH. It was concluded that nutrition plays an important role in the development of high ultimate pH values. Studies at the meat works indicated that there is a highly significant linear relationship between the number of times lambs are washed prior to slaughter and the ultimate pH of the longissimus muscle. Subsequent resting of animals for varying periods prior to slaughter has no apparent effect on repletion of glycogen stores and may, in some cases, exacerbate the problem of high pH meat. It was also found that washing of lambs is associated with a highly significant increase in bruising of carcases and that such washing may not necessarily result in a decrease in carcase contamination. Investigations of the changes of body weights and the weights and nature of ruminoreticular contents during the preslaughter holding period indicated that the ideal time to slaughter lambs, in terms of potential carcase contamination, is 18 to 24 hours after removal from pasture. It was found that stunning by a 'head-to-leg' electrical method significantly increased the rate of pH decline compared to other methods of slaughter. A further increase in the rate of pH decline was achieved by low voltage stimulation at the time of slaughter. It was concluded that the combined effects of low voltage and high voltage stimulation can cause irreversible contraction and associated toughness in a large proportion of carcases. Studies of the occurrence of haemorrhages in carcases and organs indicated that these defects are related to the method of stunning. Although blood splash has been reported to be associated with prolonged one stage prothrombin times in lambs, no statistical association was found between this parameter and speckling. It was found that there is a two to threefold increase in arterial pressure following 'head-only' stunning whereas there was only a moderate increase in venous pressure. On the other hand, stunning by the 'head-to-back' method was followed by a decrease in arterial pressure, but venous pressure increased to levels above 50 mm Hg. Electromyographic studies indicated that there is a significant increase in the intensity of muscular activity following 'head-to-back' stunning as compared to 'head-only stunning and that there is a correlation between the increased muscular activity and the increase in venous pressure. It is concluded that these events may lead to pressure changes in the microcirculatory bed which are likely to be associated with the occurrence of haemorrhagic defects following stunning by electrical methods.
  • Thumbnail Image
    Item
    The effects of on-farm mixing of bulls on beef quality characteristics : a thesis presented in partial fulfilment of the requirements for the degree of Master of Philosophy at Massey University, Palmerston North, New Zealand
    (Massey University, 2010) McDade, Julie Louise; McDade, Julie Louise
    Some degree of stress is an inevitable part of the slaughter process for production animals. The degree of stress will vary due to a number of conditions over which there is sometimes no control. Stress levels may depend on such variables as familiarity of the animal to human contact and handling, temperament and even adverse weather conditions. Pre-slaughter handling has been identified as an area that can have adverse effects on both animal welfare and ultimately on meat quality characteristics. Published information on the association between stress and meat quality, and more specifically, pre-slaughter handling and meat quality is reviewed. The physiological response of an animal to stress is examined, and the effect of the stress response on the resultant final product is presented. A detailed summary of the role of muscle glycogen both pre- and post-slaughter is also provided. The main objective of the present study was to investigate whether on-farm mixing of bulls potentially plays a role in undermining meat quality characteristics Thirty-three Friesian bulls between 18 and 24 months of age and weighing between 550 and 600 kilograms (live weight) were commercially slaughtered in January of 2010. These bulls were originally from one of seven finishing groups. The bulls were randomly allocated into one of three treatment conditions 1) control (no mixing), 2) mixing four days prior to slaughter or 3) mixing one day prior to slaughter. Blood was collected at slaughter and analysed for non-esterified fatty acids (NEFA mmol/L), plasma lactate (mmol/L), creatine phosphokinase (CPK IU/L). A sample of the longissimus muscle was collected approximately 20 minutes after slaughter. A portion of the sample was immediately snap frozen for determination of muscle glycogen concentration. Meat pH, shear force and drip loss was measured at 24 hours, 7 days and 28 days post-slaughter. Purge loss was calculated for the 7 and 28 day samples. Colour measurements were taken on bloomed and unbloomed samples. By varying mixing times it was also hoped that the effect of recovery from mixing on-farm could start to be elucidated. It was a further objective that demonstration of an effect on meat quality could be used to encourage industry to adopt certain handling practices that could be communicated to their suppliers. A best practice model of pre- slaughter handling on-farm would be the ultimate goal. This project represents only a starting point from which further research would be needed prior to development of best practice guidelines. In the present study, concentrations of creatine phosphokinase (logCPK) in blood at slaughter for the 1 day mixed group was significantly higher (p < 0.001) when comparing the three treatment groups, which indicates that these animals were more physically active in the twenty four hour period prior to slaughter than the 4 day mixed or control animals. Mean CPK values for the 4 day mixed group were not significantly different from the control animals suggesting that by four days, the bulls had re-established a social order and physical activity had returned to a “normal” level. In terms of meat quality, the difference in CPK values is relevant when considering that at 28 days post slaughter, muscle tissue from the 1 day mixed bulls had increased shear force measurements (p < 0.05) when compared to the four day mixed and controls. CPK values and shear force data were found to be positively correlated in the present study (p < 0.001). CPK values were positively correlated with ultimate pH (p < 0.001) and negatively correlated with muscle glycogen concentration (p < 0.001). Although not statistically significant (p = 0.09), the pH after 28 days ageing for the meat from the 1 day mixed animals was also increased when compared to the other two treatment groups. Meat from five animals had a pH greater than 5.8 after 28 days ageing. Three of the five were from the one day mixed group while the other two were from the four day mixed group. The highest pH at 28 days was 6.14, and this one day mixed animal also had the highest CPK at 15,756 IU/l. Not surprisingly muscle glycogen concentration from the 1 day mixed animals was lower than for the other two groups, and the significance followed the same trend (p < 0.073). Results of the current study indicate that the chances of high-pH beef and the accompanying decrease in beef quality may be increased if bulls are mixed within 24 hours of slaughter. Based on the results more research into the effects of on-farm mixing is certainly warranted.