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Item Influence of different levels of black soldier fly larvae meal on growth performance and carcass quality of broiler chickens(Elsevier B.V., 2024-11-02) Baderuddin SH; David LS; Wester TJ; Morel PCHA study was conducted to examine the impact of two inclusion levels of Black soldier fly larvae meal (BSFLM) replacing soybean meal on growth performance, nutrient utilization, carcass characteristics and meat quality of broilers. Three experimental diets based on corn-soybean meal were developed to contain 0 (control), 6 (BSF 6) and 12% (BSF 12) BSFLMfor both starter and grower phases. Each experimental diet was randomly allotted to six replicate pens (eight birds per pen). The birds were offered starter pellets from 0 to 14 day post-hatch and grower pellets from 15 to 28 day post-hatch. The experimental diets were tested for pellet durability index (PDI). There was an interaction between diet and growth phase (P < 0.001) for pellet durability index where starter diets had always a higher PDI than the grower diets, but the difference was greater for control diet than BSF 6 and BSF 12 diets. Apparent metabolizable energy (AME) of diets and coefficients of apparent ileal digestibility (CAID) of nutrients were measured on day 28 using titanium dioxide marker ratios in the diet and excreta/ileal digesta. On day 28, the weights of live body, carcass, fat pad, breast and gizzard were recorded, and then breast meat quality (meat pH, drip loss and cooking loss) was examined. Inclusion of BSFLM of up to 12 % did not reduce live weight gain or feed intake. Live weight and carcass weight were heavier in broilers fed 12 % BSFLM than controls (P < 0.02), but were not different than those fed 6 %, while controls were not different than those fed 6 %. Breast weight (percentage live weight) was lower in birds offered 12 % BSFL than in others (P < 0.04). No differences were observed between diets for the percentage weight as carcass, fat, pad and gizzard. The AME and AMEc of diets were the highest in broilers fed 6 % BSFLM diet (P < 0.005), but there were no differences between controls and those fed 12 % BSFLM. The CAID of DM, ash and N in birds fed 6 % BSFLM were greater than (P < 0.03) birds fed 12 %, but were not different than controls, which were also not different than those fed 12 %. Broiler breast meat quality was unaffected by dietary treatments. In conclusion, BSFLM at 12 % can be used effectively as a SBM replacement in starter and grower diets, without affecting the growth performance, nutrient utilization, carcass characteristics and meat quality of broiler chickens.Item Double suckling in beef x dairy once-bred heifers : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Animal Science at Massey University, Palmerston North, New Zealand(Massey University, 1995) Noricumbo-Saenz, Jorge LuisDouble suckling beef production systems are a strategy to increase annual output of suckled beef cows. This study compared the effect of single and double suckling on the performance of dams and their calves on pasture with an average sward surface height of 11.5 cm. Thirty eight spring-calving, 2-year old Hereford x Friesian (H x F) and Hereford x Jersey (H x J) heifers mated to Angus sires were randomly allocated to either single or twin rearing treatments as they were calving. Nineteen Friesian male calves were used as foster calves for the twin rearing treatment. Individual calf 90-day weaning liveweight gain (adjusted) and liveweight gain from weaning to 11 months of age were recorded. Individual heifer liveweight changes from calving to weaning, and weaning to slaughter were recorded. Heifer productivity was estimated as kilograms of weaner calf produced per heifer present at weaning. Heifer efficiency was estimated as the ratio of heifer productivity to average liveweight of the heifer from calving to weaning. Results are presented as least square means ± standard error (LSM ± SE). Calf daily liveweight gains were 1.00±0.02, 0.90±0.03, 0.70±0.03 kg/hd (P < 0.05) for single calves, heifers' own twin reared calves and twin reared foster calves respectively. At weaning, heifers' own twin reared calves were 8.1 kg lighter than single reared calves (P < 0.05). From weaning to 11 months of age, heifers' own twin reared calves had greater daily liveweight gains (0.50 ± 0.02 kg/hd) than single reared calves (0.44±0.02 kg/hd, P < 0.01) and tended to be heavier (244.12±4.8 versus 236±5.3 kg). Double suckling did not affect heifer daily liveweight gain from calving to weaning (0.7 ± 0.05 and 0.6 ± 0.04 kg/hd for single and double suckled H x F heifers respectively, and 0.3 ± 0.06 and 0.3 ± 0.06 kg/hd for single and double suckled H x J heifers, respectively) or from weaning to slaughter (0.3 ± 0.05 and 0.3 ± 0.04 kg/hd for single and double suckled H x F heifers respectively, and 0.2 ± 0.06 and 0.3 ± 0.06 kg/hd for single and double suckled H x J heifers, respectively). Double suckled H x F and H x J heifers were 44.7 and 55.5 % more productive (P < 0.05) than single suckled H x F and H x J heifers respectively. Double suckled H x F heifers were 45.1 % more efficient than single suckled H x F heifers (P < 0.05) and double suckled H x J heifers were 58.1 % more efficient than single suckled H x J heifers. It was concluded that although twin reared calves were 8.1 kg lighter than single reared calves at weaning, twin reared calves were able to surpass these liveweight differences through compensatory liveweight gain after weaning. Therefore, heifer productivity and efficiency can be significantly enhanced through the use of foster calves in double suckling beef production systems.Item A study of the relationships between growth, carcass and meat characteristics of Angus steers : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Animal Science at Massey University(Massey University, 1982) Msechu, James Kundael KileghuaGrowth, defined as change in weight, may be considered the most important single characteristic of slaughter cattle. Fast-growing cattle may have better food conversion and reach slaughter early. The end-products in a beef production business, namely, carcass and meat, have properties which determine consumer acceptability. This study focussed attention on growth, carcass and meat characteristics in cattle. Literature was reviewed on factors that influence variability in these traits and relationships reported in the literature between some of the traits were summarised. Records on 117 Angus steers born in 1975 and 1976 (years 1 and 2) were analysed by the least squares method of fitting constants. Data included birth weight, calf milk consumption pre-weaning average daily gain (ADG), weaning weight, post-weaning ADG, yearling weight, 2-year weight, finish (30-month) weight, carcass weight, kidney and channel fat weight, eye muscle width, depth, and area, fat depth, fat trim percentage, intra-muscular fat percentage, sarcomere length, meat tenderness, muscle pH, and colour, lean percentage and bone percentage. Fixed-effects constants fitted to growth data were: herd, age of dam and peri-natal treatment (calving on pasture or sawdust pad). Covariance analysis was adopted with 3 covariates: dam autumn liveweight, calf birth weight, and milk consumption. Factors fitted to post-slaughter data were: maturity, slaughter lot and pre-slaughter fasting, with 3 covariates, carcass weight, pre-weaning ADG, and post-weaning ADG. Results were inconsistent between years. Therefore, few factors were conclusively judged to be important sources of variation in the traits studied. Herd influenced milk consumption (P<0.05) and pre-weaning ADG in year 1, and weaning and yearling weight (P<0.01) in year 2. Age of dam did not affect growth traits (P<0.10). Treatment was unimportant to pre-weaning growth in both years, but year 1 analyses suggested that it affected post-weaning ADG (P<0.01) and finish weight (P<0.05). This result may be attributed to chance. Regression on dam weight was non-significant for all growth traits. Calf birth weight was found to be an important factor as far as various growth traits in year 2 were concerned, namely, weaning weight (P<0.01), and milk consumption, pre-weaning ADG and yearling weight (P<0.05). Regression of weaning weight on birth weight approached significance (P<0.10), but birth weight was otherwise unimportant in year 1. Milk consumption influenced weaning weight (P<0.05) in year 1; approached significance for its effect on pre-weaning ADG and yearling weight in year 1, and weaning and 2-year weight in year 2 (P<0.10). Maturity did not affect post-slaughter characteristics other than eye muscle depth (P<0.05) in year 2. Slaughter lot was responsible for variation in eye muscle width (P<0.001) and dressing-out percentage (P<0.01) in year 1; dressing-out percentage and bone percentage (P<0.001) in year 2. Four-day pre-slaughter fasting affected few carcass or meat traits adjusted for carcass weight by covariance analysis. The results were inconsistent between years. In year 1, fasting affected dressing-out percentage (P<0.001) only, while in year 2 such effect was not apparent (P<0.10), but it was appreciable on other traits: eye muscle width and meat tenderness (P<0.05) and sarcomere length (P<0.001). Regression of various traits on carcass weight was significant: dressing out percentage, kidney and channel fat, fat depth, intramuscular fat percentage, fat trim percentage, eye muscle depth, eye muscle area, sarcomere length, and bone percentage in year 2; it was significant for dressing-out percentage and kidney and channel fat in year 1. Pre- and post-weaning ADG were less important covariates: the former was significant to eye muscle depth, dressing-out percentage, intra-muscular fat percentage and bone percentage in year 2, but non-significant in year 1. The latter approached significance in eye muscle area, dressing-out percentage, fat trim percentage and bone percentage in year 2 (P<0.10). Residual sums of squares were used to estimate phenotypic correlations between traits studied. Correlation coefficients between growth traits were positive and medium to high except those between early growth (pre-weaning ADG, and birth, and weaning weights) and post-weaning ADG, which were negligible. Pre-weaning ADG and weaning weight had a perfect correlation coefficient (r = 1.0) in both years. Estimates between growth and carcass traits varied widely; notable were those for post-weaning ADG, 2-year weight, and finish weight with carcass weight, which were high in both years (r = 0.86, 0.80; r = 0.80, 0.85; and r = 0.92, 0.92, respectively). Carcass traits were mostly positively correlated, with low to medium coefficients between them. Lean percentage had a strong negative correlation with fat trim percentage (r = -0.71), but bore little relationship with other traits. Correlation coefficients between carcass and meat traits were mostly positive, but low and inconsistent between years. Carcass weight was related to most fatness attributes of the carcass and meat. Most meat traits were positively correlated with each other with low and medium correlation coefficients.Item Effect of sward surface height on herbage intake and performance of finishing beef cattle : a thesis presented in partial fulfilment of the requirements for the degree of Master of Applied Science in Plant Science at Massey University(Massey University, 1998) Realini, CarolinaThis study examined the effects of sward surface height (SSH) on the herbage intake, ingestive behaviour and performance of steers finished on ryegrass (Lolium perenne) /white clover (Trifolium repens) pastures during summer. The influence of this initial treatment contrast on subsequent cattle performance under common grazing conditions during early-autumn was also studied. Twenty six month-old steers with an initial liveweight of 522 ± 7.6 kg, 14 Angus x (Hereford x Friesian) and 10 Angus x (Hereford x Jersey), were set stocked on swards maintained at SSHs of 5 and 10 cm (L vs. H) from 18 November 1996 to 4 March 1997, with 3 replicate groups of 4 animals per treatment balanced as far as possible for "breed". Six steers from each treatment balanced for "breed" were slaughtered on 4 March and carcass and meat quality characteristics compared. The remaining animals were grazed for another 5 weeks on common pastures until the final slaughter on 8 April. Over the SSH control period, the 5 and 10 target swards averaged 4.8 ± 1.36 and 10.0 ± 3.24 cm. Herbage on the H swards contained more dead material, less crude protein, lower dry matter digestibility and live:dead tiller ratio than that on the L swards. Estimates of herbage dry matter intake were higher for steers grazing at 10 cm than for those grazing at 5 cm SSH (8.0 vs. 4.8 kg DM d-1 from 2 estimates and 2 alkane pairs, P < 0.05 for each comparison). Steers were unable to increase their grazing time in response to limiting sward conditions sufficiently to compensate for lower intake rates in short swards, resulting in reduced herbage intakes. Daily liveweight gain over the summer was higher on the 10 cm than on the 5 cm SSH (1.10 ± 0.23 vs. 0.32 ± 0.21 kg d-1, P < 0.01) and carcass weight at first slaughter was significantly higher for steers on the H swards (332 ± 10.6 vs. 287 ± 7.5 kg, P < 0.05). SSH treatment did not affect other carcass or meat quality characteristics of steers. Liveweight and carcass weight gain per hectare were 71 % and 43 % greater (318 vs. 186 kg and 166 vs. 116 kg) for steers grazing at 10 cm despite the lower stocking rate (2.86 vs. 5.80 steers ha-1) maintained by the tall swards. Over the common grazing period previously restricted steers had higher intakes, greater grazing and ruminating times, lower resting time and grew faster compared to steers previously grazed at 10 cm SSH. However, none of these parameters were significantly different between the steer groups with the exception of resting time. Increased autumn growth rates by previously restricted steers did not compensate for the differences in liveweight established during summer, and significant differences in carcass weight were still evident at the end of the compensatory period between the steer groups (335 ± 9.4 vs. 297 ± 9.4 kg, P < 0.05). There were no significant differences in meat quality characteristics with the exception of meat brightness which was higher for previously restricted steers. These results suggest that maintaining a sward height of 10 cm offers advantages in terms of individual animal output and output per hectare compared with grazing at 5 cm and that compensatory growth does not seem to be an important phenomenon in heavy (over 500 kg liveweight) finishing steers.Item The significance of "navel ill" and other lesions at post-mortem inspection of bobby calves : a thesis presented in partial fulfilment (70%) of the requirements for the degree of Master of Veterinary Science, Massey University, New Zealand(Massey University, 1990) Biss, Monique ElizabethCalves slaughtered for bobby veal in New Zealand are considered a public health risk if "acute inflammation of the umbilicus" is present at slaughter, because it is believed that the consumption of veal derived from these calves may subsequently "cause food-poisoning" as a result of bacterial dissemination throughout the carcass. This belief, however, has not been fully validated. During the 1989 season, 54 calves were condemned for "navel ill" (0.465% of the total slaughtered) at Waitaki International's Feilding export slaughterhouse. Carcasses from these calves, along with 31 normal carcasses, were examined for the presence of septicaemia (Part I). The study involved the detailed gross examination of the carcass and viscera, together with microbiological examination of umbilical vein, liver and muscle, and histopathological examination of the umbilical vein, liver, and kidney. The working definition of septicaemia for the purposes of this study was the presence of large numbers of bacteria in the general circulation, involving slight or absent clinical signs and with or without gross evidence of early systemic infection in the carcass. Bacteraemia was defined as the presence of smaller numbers of bacteria in the general circulation, with or without gross evidence of localisation in the carcass. Although differing from the several definitions, particularly of septicaemia, in the literature, these were proposed as appropriate definitions in the context of the slaughterhouse. The presence or absence of septicaemia was determined on the basis of the combined gross lesions in the carcass, histopathological lesions in the liver and kidney, and microbial isolates from the liver and carcass musculature. The presence of infection extending from the umbilicus was determined by histopathological and microbiological examination of the umbilical vein near the liver. "Navel ill" could be sub-classified into three categories: (1) Umbilical vessel infection and carcass lesions indicative of systemic spread, with or without umbilical infection. (2) Umbilical vessel infection, with or without umbilical infection. (3) Umbilical infection alone. Three carcasses condemned for "navel ill" had no abnormalities of the umbilicus or umbilical vessels. Of the remaining 51 carcasses, one (2%) had gross, histological and microbiological evidence of septicaemia, and seventeen (33%) had lesions indicative of bacteraemia or septicaemia. The proportion of condemned carcasses which were bacteraemic decreased as the condemnation criteria expanded to include all three categories of "navel ill". There was a significant risk of bacteraemia in carcasses from ail sub-categories of "navel ill", except category (3), when compared with normal carcasses. Insufficient data were generated to allow assessment of the risk of septicaemia being present in carcasses from calves with "navel ill". A second study was undertaken later in the 1989 season, and involved the detailed gross examination and description of 371 calves condemned for any reason at six export slaughterhouses; five in the North Island and one in the South Island. The major disease entities found in calves of this age and resulting in carcass condemnations were "navel ill" (197 (0.50%) carcasses), pneumonia (75 (0.19%) carcasses), arthritis (31 (0.08%) carcasses, and "white spotted kidneys" (30 (0.08%) carcasses). Peritonitis, jaundice, hepatic abscesses and "fever" occurred at very low rates (< 0.03%), while other lesions occurred sporadically. The current inspection system in New Zealand requires calves with "acute inflammatory lesions" to be condemned. In this study, this requirement resulted in the condemnation of virtually all diseased calves, whether the disease was acute, chronic, generalised, localised or non-infectious in nature. There was, however, considerable variation found in the severity, age and likely pathogenesis of the lesions in each disease category. Because this "blanket" approach to disease in the bobby calf leads to unnecessary condemnation and wastage, it is suggested that more appropriate judgement criteria such as the trimming of localised infectious and traumatic lesions should be considered.Item A novel model developed for quantitative microbial risk assessment in the pork food chain : a dissertation presented in partial fullfilment [sic] of the requirements for the degree of Doctor of Philosophy at Massey University, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand(Massey University, 2007) Titus, Simone MeganFood-borne diseases contribute substantially to morbidity and mortality rates worldwide. The deleterious impact of these diseases on human health, concurrent with the associated socioeconomic cost has led to an increased demand for the production of safe food globally. Consequently, agencies such as the World Health Organization (WHO) and the Food and Agriculture Organization (FAO) have resolved to address this issue. In this vein, scientific, risk-based approaches which facilitate estimation of the probability of disease occurrence, the magnitude of the disease and efficacious control measures have been recommended for use internationally. Many pathogens have been implicated as aetiological agents of food-borne disease. The WHO has identified non-typhoidal Salmonella, Escherichia coli and thermophilic Campylobacter as zoonotic food-borne pathogens of greatest importance. These pathogens can be transmitted to humans through pork consumption. This thesis therefore proposes a suite of novel, mechanistic, semi-stochastic, quantitative, modular process risk models describing the propagation of these three pathogens from the live pig at the abattoir, to pork chops sold at retail. The model is developed for use in risk-based, quantitative microbial exposure assessments in New Zealand and can be employed to explore different intervention strategies targeted at mitigating contamination levels of these pathogens on pork chops. The models comprise multiple, coupled, differential and difference equations. These equations explicitly describe bacterial growth, inactivation, removal, cross-contamination and food partitioning occurring in continuous and discrete time in abattoirs and at retail. Distributions of pathogen numbers on the surface of carcasses, and prevalence levels are output by the models at different stages of abattoir processing and pork chop production. Both dressed pork carcases exiting abattoirs in New Zealand and pork chops at retail are predicted to contain low surface contamination levels of the pathogens under consideration, while a small percentage is estimated to be highly contaminated. Median contamination levels on dressed pork exiting the abattoir are predicted to be less than one cfu/cm2. Generally, there are large reductions in surface bacterial numbers for all three organisms from the time the live pig enters the abattoir, to sale of the pork chop at retail. The introduction of a second singeing procedure immediately postevisceration in the abattoir is predicted by our models, to be an effective mitigation strativ egy, with estimated reductions in median pathogen levels of 100%. This control measure is considered to be more effective than coverage of the anal region of the pig during evisceration. This latter mitigation strategy was predicted to result in 10% – 44% reduction of median pathogen contamination levels. At retail, pork chops are also estimated to contain low numbers of these pathogens. Therefore handling of the raw pork chop soon after purchase from retail outlets may be associated with a low risk of contracting salmonellosis, colibacillosis and campylobacteriosis. This risk can be further reduced by placing pork chops in a blast chiller for 12 hours prior to display. When this mitigation strategy was modelled the outputs indicated a 15% – 61% reduction in the maximum pathogen levels on pork chops, 44 – 100% reduction in the 10th – 90th range and 14% – 50% reduction in pathogen prevalence levels. Detailed investigation revealed the limitations of a specific modelling approach. We determined that the population-based modelling approach is not an appropriate alternative to the individual-based modelling approach when there is a large disparity in contamination levels between processed carcasses. Therefore the former technique should not be used in the presence of large heterogeneity with respect to the number of bacteria on the food unit of interest, or when bacterial populations input into the model are described with large variances. This thesis demonstrates the application of a suite of novel risk models in the pork food chain. We propose use in quantitative microbial exposure assessments. The applicability of these models is not only limited to the pork chain or to the above mentioned pathogens, but by modification of parameters, the entire model, or portions thereof can be extrapolated to other animal species undergoing similar abattoir procedures with pathogens of analogous epidemiological patterns. Finally the information provided by the models can be instrumental in assisting risk managers in their decision-making and policy development undertakings and provide guidance to effectively and strategically funnel limited resources.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 VindelevA 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.Item Nutritional, genetic and meat quality aspects of once-bred heifer beef production systems in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University(Massey University, 1994) Khadem, Ali-Akbar; Khadem, Ali-AkbarIssues related to the nutrition, management, carcass and meat quality traits, and the profitability of "Once-Bred Heifer" (OBH) beef production systems under New Zealand pastoral conditions were investigated in this research programme. Once-bred heifer beef production systems involve surplus heifers from the dairy industry which are mated to beef sire breeds at about 15 months of age and rear their calves for 3-6 months before being slaughtered at 30-32 months of age. Both the heifer dams and their progeny are thus prime meat-producing animals. The performance of once-bred v. unbred heifers and of early-weaned (EW) heifers (heifers weaned at day 84 of lactation "L84") v. normal-weaned (NW) heifers (heifers weaned at L147) were studied in the first two trials. In the third trial, Hereford x Friesian (H x F) v. Simmental x Friesian (S x F) heifers offered a restricted herbage allowance (RHA, an allowance to maintain weight) v. normal herbage allowance (NHA, an allowance to grow at 0.6-0.7 kg/d) during mid pregnancy (from pregnancy day 114, "P114", to P214) were studied in an attempt to investigate the effects of dam genotype and prior herbage allowance on the performance of heifer dams (growth rate, reproduction and carcass and meat quality traits) and their progeny (growth rate and weaning weights). A gross margin analysis was also performed to evaluate the profitability of alternative OBH beef production systems. Once-bred v. unbred Hereford x Friesian heifers consumed similar amounts of herbage organic matter (OM) during the period equivalent to late pregnancy of the former group (4.72 v. 5.15 kg OM/hd/d), but lactating heifers consumed more herbage OM than the comparable unbred group (11.36 v. 9.19 kg OM/hd/d, P < 0.05) to support the growth of their calves, as well as themselves. Unbred heifers had greater carcass weights and higher dressing-out percentages than once-bred heifers. However, the differences in other carcass and meat quality traits between the heifer groups were small, indicating that once-bred heifers are capable of producing meat comparable in quality to that of unbred and empty heifers. Higher gross margins ($5-10/Stock Unit (SU)) were calculated for once-bred v. unbred heifers. During the 10 days immediately prior to weaning, NW heifers had organic matter, dry matter and energy intakes which were slightly higher (P < 0.10) than those of EW heifers (weaned at L84). Weaning caused a slight weight loss in both early- and normal-weaned heifers for the first 30-45 days post-weaning, but liveweight (LW) was recovered after this period. During L84 - L147, EW heifers had a higher daily liveweight gain (LWG) than NW heifers (0.79 v. 0.51 kg/d, P < 0.01). Calves weaned at L84 had significantly lower daily LWG than NW calves during the period L84 - L147 (0.73 v. 1.30 kg/d, P < 0.001). This resulted in EW calves being 30 kg lighter (P < 0.001) than NW calves at the time of weaning for the latter group. Early-weaned heifers reached the target slaughter weight in March and, overall, had slightly better carcass and meat quality characteristics than those of the normal weaned group. Although similar gross margins were calculated for EW ($41.68/SU) v. NW ($42.00/SU) heifers, early weaning offers advantages to OBH beef production systems through increased flexibility of grazing management and selling times for animals. From P114 until P214, NHA heifers had significantly (P < 0.001) higher growth rates (0.72 ± 0-03 kg/d) than the RHA group (0.16 ± 0.02 kg/d). This resulted in a higher LW in NHA heifers at P214 (P < 0.001) and P270 (P < 0.01) than the RHA heifers. Gestation length, calving score, LW loss at calving and calf birth weight were not affected by dam genotype (Hereford x Friesian v. Simmental x Friesian) or prior herbage allowance. Meat quality traits were not affected by dam genotype, but it was concluded that the use of Simmental x dairy heifers in a OBH beef production system increases carcass weights of heifer dams in comparison to those of heifers derived from traditional British beef x dairy animals. However, gross margins were similar for H x F and S x F heifer groups indicating that little incentive would exist for dairy farmers to use sires of the large European breeds (e.g. Simmental) rather than Hereford sires which are commonly used to mate first-calving heifers in the dairy industry. The results are discussed in the context of the development of once-bred heifer beef production systems in New Zealand.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 LouiseSome 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.