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Item Extended-spectrum β-lactamase (ESBL) and AmpC β-lactamase (AmpC) producing Escherichia coli in dairy calves from the Canterbury region : a dissertation presented in partial fulfilment of the requirements for the degree of Master of Veterinary Studies in Veterinary Public Health at Massey University, Manawatū Campus Palmerston North, New Zealand(Massey University, 2020) Mwenifumbo, MerningAntimicrobial resistance (AMR) has become a global public health concern threatening current effective prevention and treatment options. Infections caused by antimicrobial resistance strains are costly, often harder to treat and sometimes fatal. One group of bacteria that contributes to AMR are the extended beta lactamase (ESBL) and AmpC beta lactamase (AmpC) producing E. coli. These are on the critical list of important antibiotic-resistant bacteria of human importance compiled by the World Health Organisation and are a public health concern due to their resistance to an extended range of beta lactams. The main driver for the spread of AMR is the use of antimicrobials in both human and animals. One potential spread is by the feeding of waste milk to calves. Waste milk is the milk that contains antibiotics or other drugs. Waste milk is not recommended as feed for calves due to its association with the development of antibiotic resistance bacteria. Using the culture depended methods and whole genome sequencing, this study aimed to determine the prevalence of ESBL and AmpC producing E. coli isolated from recto-anal mucosal swabs (RAMS) from waste milk fed dairy calves, and to phenotypically and genotypically characterise ESBL and AmpC producing isolates. Recto-anal mucosal swabs samples (n = 40) from waste milk fed dairy calves collected from Canterbury region, New Zealand were screened for antimicrobial resistant E. coli. Fifty-eight percent (23/40) of the calves harboured antibiotic resistant E. coli. 25% (10/40) calves were positive for AmpC producing E. coli and none of the calves were positive for ESBL producing E. coli. The highest prevalence of resistance was observed for tetracycline. PCR and Sanger sequencing revealed that all the AmpC positive E. coli were chromosomal mediated with four mutations in the promoter region of the ampC gene. Whole genome sequencing of eight isolates resistant to both tetracycline and streptomycin revealed additional resistance genes that were not tested phenotypically. Using the Clermont phylogrouping method of E. coli, the AmpC positive, the tetracycline and streptomycin resistant E. coli isolates were distributed among phylogroups B1, C and D. In conclusion, this study revealed the presence of AmpC producing E. coli and other resistance genes in E. coli isolated from waste milk fed calves. Further epidemiological studies are required to determine whether these antibiotic resistant E. coli are associated with waste milk.Item Mortality and failure of passive transfer of immunity in New Zealand dairy calves : a thesis presented in partial fulfilment of the requirements for the degree of PhD in Veterinary Science at Massey University, Manawatu, New Zealand(Massey University, 2019) Cuttance, Emma LouiseIn recent years, there has been a growing interest from consumers globally about the welfare of the animals producing their food. In New Zealand, particular attention has been paid to the treatment of calves though the help of welfare lobbyists bringing certain New Zealand farming practices into the spotlight. Unlike most of the rest of the world, in New Zealand, cattle are born outdoors and are housed only for a short period of time. This has meant that international research on mortality, colostrum management and calf health has been generally not applicable, and that we need New Zealand-based data to be able to benchmark key outcomes. We had two major objectives for this research. The first was to accurately estimate perinatal and postnatal mortality on New Zealand dairy farms and to identify potential risk factors. The second objective was to focus on one factor that is known to be strongly associated with calf mortality: the failure of the calf to take up sufficient colostral antibodies to provide protective immunity until the calf’s antibody-production system becomes fully effective (“failure of passive transfer”; FPT). The study aimed to estimate the prevalence of FPT across New Zealand dairy farms, identify potential risk factors that may be associated with that prevalence and to evaluate the effects of FPT to the end of first lactation. We found that, despite the significant differences between the New Zealand system and those of the northern hemisphere, the mortality risk of perinatal (5.7%) and postnatal calves up to weaning (4.1%), then weaning to ~27 months (2.7%) was comparable. However, our review of the previously published data highlighted that the quality of data collection, transparency in methods and validation of records in most other studies, particularly retrospective ones, was poor, limiting the validity of such comparisons. We identified substantial variation between farms in mortality risk (2.2-8.6% perinatal, 0-11% postnatal pre-weaning, 0-7.9% weaning to ~27 months), thus significant reductions in calf mortality may be achievable on many farms. One factor responsible for this variation may be farm-level prevalence of FPT which averaged at 33% and ranged from 5-84%. In intensive systems, separating calves from their dam and feeding high quality colostrum within 4-6 hours of birth reduces FPT. In contrast, our research found no effect of earlier colostrum feeding on FPT prevalence and the only significant herd level risk factors were region and herd size. This may be at least partly due to the difficulty of increasing calf pick-up to the frequency recommended for intensive farms. FPT increased mortality and morbidity and to a lesser extent decreased weight gain in the first 12 months, however showed no appreciable effect after this time.Item The value of dried buttermilk as compared with skim milk for calf rearing, and the effect of feeding at two different levels on growth to weaning under New Zealand conditions : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science, University of New Zealand(Massey University, 1949) Corbett, J. L.It is startling fact that each year in New Zealand, the digestible protein lost for human consumption through the inefficient conversion of dairy by-products into pigment, is approximately twice the total annual output of protein in lamb and cheese; and the food energy lost nearly equals the energy in these two commodities (Filmer 1944). Though a proportion of the loss is through the associated feeding of coarse grain and meat meal, and also some from whey, the great majority arises from the feeding of skim milk and buttermilk which are of immediate human nutritional significance. The case for making these high quality foods directly available for human consumption is strong, despite any repercussions on the pig industry and notwithstanding such economic considerations as secure markets. In order to do so it is obvious that the raw materials must be processed to reduce bulk and improve keeping quality for transportation. The utilisation in this way of skim milk is set back by the considerable problem of its collection from the cream supplying farms, though it may be easier where the density of these in an area is high. Since the buttermilk is produced at the dairy factory, this difficulty does not apply. [From Introduction]Item Viability of dairy-origin calves for a new beef production enterprise in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Agricultural Science at Massey University, Palmerston North, New Zealand(Massey University, 2019) Hunt, Joshua JamesThe New Zealand dairy industry produces approximately 4.2 million calves annually, of which about 30% are retained within the dairy industry, while a further 20% are utilised in the beef industry. The remainder are surplus to requirements, and the majority (1.7 million per annum) are processed in the low value bobby calf trade. This model appears sub-optimal, with an estimated opportunity cost in excess of NZD $1 billion annually, and numerous animal welfare and ethical issues. Farming surplus dairy calves in an accelerated-cycle beef production enterprise for slaughter prior to one-year of age, could generate favourable outcomes, and the current study aimed to investigate this opportunity. Experimental growth and carcass data for Hereford x Friesian-Jersey steers slaughtered at 8-, 10- and 12- months of age was obtained in a live-animal trial. Simulation models (referred to as NGB8, NGB10 and NGB12 where the figures refer to monthly ages at slaughter) utilising Microsoft EXCEL feed budgets, gross margin analysis and the OVERSEER nutrient budget model were developed from the experimental data to estimate the physical, financial, and environmental performance of accelerated-cycle beef production at each slaughter age. Results were compared to a simulated high and low performing bull- beef enterprise based on the literature, with slaughter occurring at 18- or 24-months, to determine the relative performance of accelerated-cycle beef production. The model comparators are referred to as Bull18 and Bull24. In the trial, the accelerated-cycle beef production (NGB) steers achieved slaughter weights of 252, 303 and 348 kg at 8-, 10- and 12-months of age (119, 146 and 174 kg carcass weight). The dressing out percentage was the same in the 8- and 10-month treatments (P>0.05) but increased in the 12-month treatment (P<0.001). Using the ‘prime’ beef price, NGB8 and NGB10 generated a loss, while NGB12 was profitable. To be financially competitive with Bull18 or Bull24, NGB production required a price premium of 11 – 29% above the ‘prime’ beef schedule. There was insufficient evidence to suggest NGB production had a lower nutrient loss footprint, or reduced greenhouse gas output compared to bull-beef production. Further analysis showed weaner genetic merit for growth had a positive relationship with profitability, but no interaction with environmental output under NGB production. Overall, this study demonstrated that Hereford x Friesian-Jersey steers can grow well under typical beef finishing conditions. Given that accelerated-cycle beef production’s environmental output is similar to bull-beef production, profitability is the key determinant of the concept’s viability. Although NGB production with slaughter occurring at 12-months of age was profitable under the ‘prime’ beef classification, a premium of 11 – 29% (depending on slaughter age) would be required for the proposed enterprise to be financially competitive with bull-beef production. However, research has shown the meat derived from this production system is of high quality, therefore there is potential for a price premium if suitable markets are located. Finally, the procurement of weaners with high genetic merit for growth represents an opportunity to further enhance the proposed enterprises overall performance.Item The effect of early life nutrition on rumen microbial community development and impact on lifetime performance in ruminants : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Veterinary Sciences at Massey University, Palmerston North, New Zealand(Massey University, 2019) Cristobal Carballo, OmarManipulation of the rumen microbiota in adult ruminants has been intended to improve animal performance and decrease greenhouse gas emissions, but results have only shown a short- or non-lasting effect after intervention. Changes in the ruminal microbiota during rumen development have recently shown promising results in the short-term. Therefore, the purpose of the present body of work was to determine how dietary management and chemical interventions, during rumen development, modify the ruminal microbial community composition, and whether these changes affect rumen fermentation and development, and consequently, performance in the young ruminants. The objectives of this thesis were to: (i) evaluate the impact of early weaning on rumen development and function in artificially-reared lambs; (ii) characterize the impact of early weaning in lambs on the rumen microbiota in the first 16 weeks of life and examine the relationships between rumen microbiota composition and rumen fermentation profiles, rumen development and blood metabolites; (iii) assess whether contrasting feeding regimes in the first 7 months of life lead to an imprint in the rumen microbial community structure, fermentation profiles and methane emissions in the rumen of calves; (iv) and evaluate the effect of methane inhibitors on the rumen microbial community composition, fermentation pathways, and gas emissions in calves. A series of three experiments were carried out in young ruminants separated from their mothers after colostrum intake, to address the objectives of this thesis. In experiment one, 3-5-day-old lambs were euthanized at weeks 0, 4 and 16 of rearing to investigate objectives (i) and (ii). Early weaning of lambs increased plasma hydroxybutyrate at week 4 of rearing, while dry matter intake, fermentation profiles and rumen morphology were similar between groups. Papillae morphology and muscular thickness differed between ruminal sites at 4 and 16 weeks of rearing, but not between treatments. Diversity and relative abundance of ruminal bacteria was affected by feeding management, whilst the archaea community showed few changes. Changes in the proportions of abundant bacteria genera from Bacteroidetes and Firmicutes were associated with fermentation profiles, rumen morphology and blood metabolites; however, further investigations are required to explain these associations. In experiment two, ~1-week-old calves were reared with two divergent feeding systems and different post-weaning forage quality with a common pasture diet after 7 months of age to investigate objective (iii). Consumption of pre-weaning concentrate compared to forage produced lower methane yields and greater total short chain fatty acids (SCFA) concentrations and propionate proportions; whist ruminal microbes showed greater proportions of saccharolitic bacteria and Methanobrevibacter boviskoreani, but lower hemicellulolytic and cellulolytic bacteria, and Mbb. gottschalkii. Post-weaning, high-quality forage produced greater total SCFA concentration and propionate proportions than low-quality forages, while methane yield was similar. Hemicellulolytic bacteria and Methanosphaera spp. were greater in high-quality forages, while cellulolytic bacteria and Methanomassiliicoccales spp. were greater in low-quality forages. No pre-weaning effect was observed. Finally, the consumption of a common diet after 7 months of age resulted in similar methane emissions, fermentation profiles and microbial communities. In experiment three, ~1-week-old calves fed either concentrate starter diets or starter diets plus methane inhibitors were tested to evaluate objective (iv). Inhibitor intake decreased methane yield, but increased hydrogen yield and the proportion of propionate and had no effect on dry matter intake, total SCFA concentrations or animal growth. Within the abundant bacteria, the proportions of hydrogen utilizing and producing bacteria increased and decreased, respectively. Archaea diversity and proportions were affected during the period of methane inhibitor intake. However, similar gas emissions, fermentation profiles, and microbial communities were observed between groups at 24 and 49 weeks of age. Collectively, these results showed that reducing the age at weaning and introducing the solid feed to lambs at ~1 week of life accelerated some aspects of rumen morphology and function. Dietary management and methanogen inhibitor interventions affected the composition of the ruminal microbiota and fermentation profiles during treatment, however, no permanent changes in the microbial community and resulting ruminal fermentation were observed post-treatment in young ruminants.Item Carcass characteristics and meat quality of dairy-origin steers slaughtered at eight, ten and twelve months of age : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Agricultural Science, Massey University, Palmerston North, New Zealand(Massey University, 2019) Pike, Samuel JohnApproximately 2 million surplus calves are produced annually by the New Zealand dairy industry, which are generally processed at around one week of age as “bobby” calves. Concerns surrounding animal welfare issues, due to the ethics of slaughtering calves at such a young age, pose a threat to the industry’s social licence to farm, consumer acceptability and market access. In addition, the beef sector also faces the challenge of improving production efficiency, whilst minimising environmental impacts. To address these issues, a novel yearling beef production system is proposed, that would utilise dairy-origin calves and implement a slaughter age of between eight and twelve months. The objective of this study was to compare carcass characteristics and meat quality attributes of Hereford x Friesian-Jersey steers slaughtered at eight, ten and twelve months of age, in order to understand the potential saleable meat yields and type of meat product that could be sourced from yearling dairy-origin cattle. Additionally, the study aimed to determine if postmortem ageing had an effect on meat quality attributes. Sixty Hereford x Friesian-Jersey weaner steer calves born in spring 2017 were sourced from a commercial calf rearer at three months of age (average 103±1 kg live weight). The calves were managed as a single group; however, they were randomly pre-assigned at eight months of age to one of three slaughter treatments: eight, ten and twelve months of age. Steers were grazed on herb-clover pastures and brassica crops from December 2017 to March 2018, then on ryegrass and white clover pasture until slaughter. Steers were processed in May, July and September 2018 at eight, ten and twelve months of age respectively, at Venison Packers Feilding Ltd. Growth rates of the three slaughter groups averaged 0.9 kg/day and did not differ between treatments. The final unfasted live weights prior to slaughter at eight, ten and twelve months of age were 252±6 kg, 303±4 kg and 348±5 kg respectively (P<0.001), which corresponded to carcass weights of 119±3 kg, 146±3 kg and 174±3 kg (P<0.001). Steers slaughtered at twelve months of age achieved a greater dressing-out percentage (50.0±0.2%) than steers slaughtered at eight (47.2±0.2%) and ten (47.4±0.2%) months of age (P<0.001). Rib fat depth, P8 fat depth and eye muscle area measured by ultrasound increased at each age (P<0.001). Fat depths at all three ages were below 3 mm, which is the minimum fat depth required for steers to be classified in the ‘P’ fat class designating 3-10 mm of subcutaneous fat, under the current beef carcass classification system. The muscle to bone ratio, intramuscular fat content and yellowness of carcass fat all increased progressively with slaughter age. Objective meat quality attributes were measured on the M. longissimus lumborum (striploin). The caudal half of each striploin muscle was aged for 21 days in vacuum packaging, while the cranial half was frozen immediately after boning, 24 hours postmortem. Shear force values for unaged samples at eight, ten and twelve months of age were 5.1±0.2 kgF, 5.4±0.2 kgF and 5.5±0.2 kgF respectively. Although there was no difference in shear force values, sarcomere length or drip loss between the three slaughter age treatments (P>0.05), ultimate pH and thaw loss increased with age, while cooking loss declined. Meat colour also became darker and redder as animals became older (P<0.001). Proteolytic ageing for 21 days had a positive effect on shear force values and water-holding capacity at all slaughter ages, though differences were minimal (P<0.001). Overall, the changes in carcass characteristics with age were small, likely due to there being only four months’ difference in age between treatments. However, the greater saleable meat yields and dressing-out percentages at ten and twelve months of age may be advantageous in terms of processing efficiency and profitability. Differences in objective meat quality measures between eight, ten and twelve months of age were also small, indicating that the yearling beef is very tender and of high eating quality. This suggests that the beef obtained from beef-dairy cross cattle slaughtered between eight and twelve months of age and at live weights of 250-300 kg could be processed together under one category, and that the product could justifiably be targeted at markets which offer a premium.Item The comparison of pasture and concentrates as early-weaning foods for calves : a thesis ... for the degree of Master of Agricultural Science in Animal Science(Massey University, 1974) Byford, Malcolm JamesFourteen Friesian bull calves, born May 1972, were used in an experiment to study the use of pasture compared with concentrates as an early weaning food for calves. Early-weaning was defined as the weaning of calves off a liquid diet to a solid diet by the time they were five weeks of age. The calves were housed indoors in metabolism crates, with the pasture (ryegrass/clover) being cut daily and fed to them fresh. The composition of the concentrate diet was 65% rolled barley, 14% meat meal (60% protein), 15% linseed meal, 5%molasses, and the balance minerals and vitamins. The concentrate diet was fed as a meal and to help ensure the health of the calves receiving it, 10% finely chopped hay was added. The calves were randomly allocated to the two groups (seven calves in each) on arrival, when they were about four days old. During the pre-weaning period all calves were managed similarly and fed in accordance with early-weaning practise, i.e. restricted level of milk to induce a rapid development of the intake of solid food. In order to guarantee the ingestion of pasture the level of concentrates fed was restricted. The calves were weaned off milk by five weeks of age. In the post-weaning period, from five through to eight weeks of age, one group of calves received pasture ad libitum and the other concentrate ad libitum plus a restricted level of pasture (500g wet matter/day - accounting for 8 to 10% of the total DM intake). It was concluded that pasture was inferior to concentrates in promoting live-weight gain in early-weaned calves. This occurred despite pasture and concentrates having similar DE coefficients; namely 75.16 and 74.25% respectively. The major difference was that of intake, with the calves receiving pasture having a significantly lower DE intake over the post-weaning period compared with the calves receiving concentrates. The difference in intake was probably associated with pasture having a lower bulk density than concentrates. Two possible mechanisms, gut fill and oropharyngeal, whereby this would have caused a difference in intake are discussed. Also discussed is the absolute growth rates of the calves receiving pasture in the context of the possible use of pasture as an early-weaning food for dairy replacement stock. Between eight and ten weeks the calves receiving the concentrate diet were changed to pasture alone. This caused a decrease in the performance of these calves. However, these results were confounded by a decrease in the quality of the pasture over this period. Between ten and twelve weeks all calves were receiving pasture alone ad libitum. The rearing methods were shown to have no effect on the calves intake of pasture during the twelfth week, provided allowance was made for the difference in live weight which existed between the two groups. The calves were put out to pasture when twelve weeks old and their post-experimental growth rates recorded. This period was terminated when the average age of the calves was 303 days. The results demonstrated that the mean grown rates of both groups during this period were very similar. This resulted in the live-weight difference established between the two groups when they were twelve weeks old being permanent.Item Assessment of tail docking and disbudding distress and its alleviation in calves : a thesis presented in fulfilment of the requirements for the degree of Master of Science by thesis only at Massey University(Massey University, 1994) Petrie, Natalie JeanIn this age of increasing awareness of animal welfare, the demand for scientific methods to quantify the welfare of animals maintained under different conditions and exposed to different husbandry procedures has also increased. The aim of the present study was to examine the acute distress involved in the procedures of tail docking and disbudding of Friesian dairy calves. Different methods of tail docking (rubber ring and docking iron) and disbudding (scoop and cautery), with or without the use of a local anaesthetic, have been assessed using changes in plasma cortisol concentration and some behavioural observation as indices of distress. The practical objectives were to provide advice on choice of method and on the benefits or otherwise of using local anaesthetic to alleviate the pain associated with these procedures. The innervation at the docking site of the bovine tail and the efficiency of two methods of local anaesthetic administration (epidural and ring block) in desensitising the tail were assessed. Epidural local anaesthetic was found to totally desensitise the entire tail whereas a ring block adminstration of local anaesthetic around the docking site only effectively desensitised an area immediately adjacent to the site of ring block administration. Hence, to ensure total loss of sensation in the tail, an epidural administration of the local anaesthetic was used in the tail docking experiments. Tail docking, with or without a local anaesthetic, most three to four month old Friesian dairy calves was found to be no more distressing than control handling and blood sampling using both plasma Cortisol concentration and behavioural indices of distress. However, there was a degree of between-animal variation in response - a small proportion of calves which received some treatments that were not expected to cause distress showed signs of mild distress. The reasons for these responses are unknown. Disbudding six to eight week old Friesian dairy calves with a scoop caused a marked distress response which lasted for about five and a half hours, whereas the alternative method, the cauterising iron, was only slightly more distressing than control handling and blood sampling during the first one hour after disbudding. Although administration of a local anaesthetic before scoop disbudding produced a marked reduction in plasma cortisol concentration during the first two hours after treatment there was little or no reduction in overall distress, as judged by plasma cortisol responses. However, prior administration of a local anaesthetic to calves disbudded by cautery effected a slight reduction in the distress response, decreasing it to near control levels. The practical advice on method for these husbandry practices would be for tail docking, continued use of the rubber ring if tail docking is deemed necessary at all, and for disbudding, cautery alone or with local anaesthetic, if practically viable, would be recommended.Item The effect of solid feed diet on the oral and cross-sucking behaviour of pre-weaned dairy calves : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Animal Science at Massey University, Palmerston North, New Zealand(Massey University, 2013) Hansen, ChelsieIn the dairy industry calves are most frequently artificially reared in groups, which create a greater opportunity for solid feed consumption and non-nutritive oral behaviour. This study aimed to compare the effect of differing solid feed diets on the pre- and post- weaning feed intake, growth rate and oral behaviour of calves reared artificially in groups. This experiment was a randomised block design with the treatments diets allocated at random, in blocks. The research was completed at Massey University’s dairy calf unit #4 and involved 108 Friesian and Jersey x Friesian dairy calves that were allocated to one of three treatment diets: lower forage (LF) alfalfa total mixed ration (TMR); a higher forage alfalfa (HF) TMR; and perennial ryegrass hay along with a pelleted starter (HPS). Calves were reared in 36 groups of three calves per group and monitored until 12 weeks of age. Calves fed HPS had the greatest dry matter intake (LF: 0.80 (0.012), HF: 0.95 (0.012), HPS: 1.70 (0.011) kg/DM/d), live weight at 40 d of age (LF: 60.3 (1.41), HF: 63.8 (1.41), HPS: 67.1 (1.38) kg) compared with TMRs. These calves also spent the most time eating (LF: 129.1 (0.14), HF: 163.7 (0.14), HPS: 154.1 (0.14) mins/d), and spent the least amount of time engaged in non-nutritive pen sucking (LF: 13.4 (0.16), HF: 11.2 (0.17), HPS: 10.3 (0.16) mins/d). It was concluded that, while cross-sucking was not entirely eliminated, providing perennial ryegrass hay along with a pelleted starter resulted in the least non-nutritive sucking behaviour, along with the greatest feed intake and growth rates compared with low and high forage alfalfa based total mixed rations.Item An assessment of a "controlled release" chromium device for measurement of intake in calves : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science at Massey University, New Zealand(Massey University, 1988) Kassano, Aggrey MbonekoTwelve Friesian male calves were used, in three blocks each with 4 calves, to assess the efficiency of a Controlled Release Device (CRD) designed to provide chromic oxide as a faecal marker. Animals were weighed at the start and at the end of each replicate, after initial weight measurements calves were randomly allocated to one of 4 treatments (grass only, soya and grass, powdered milk and grass and liquid milk, carbohydrate concentrate and grass). Cut pasture was offered ad libitum while supplements were restricted at fixed levels and provided 11.28 MJME (metabolisable energy) and 175 g crude protein (CP) per calf daily. After a 5-day preliminary period, two 5-day collection periods followed. The CRDs were administered by use of a 'balling gun' which introduced the device gently to the rumen. Collection of faecal and urine samples commenced 24h after administration of devices. Faecal grab samples were collected from calves (per rectum) daily at 10.00 am, 01.00 pm and 04.00 pm while a 24 h representative faecal sample was taken every morning from the total day's collection. Daily faecal total collection was subsequently bulked for a 5-day sampling period. A daily release of chromium (Cr) from CRDs was found to be 133 mg d-1 (obtained by measuring the amount of Cr 'loss' from three capsules which were regurgitated) which compares with the expected 130 mg d-1. There were no significant variations in Cr concentration between times within a day. Marked fluctuations in Cr concentration were noticed in Period 1 (first 5-days) of each block while concentration reached a more steady plateau in Period 2 of each block. Similarly there were varying Cr release rates (RR) between days however, no statistical significance was shown because of the small number of calves within treatment (n=3). The daily RR was found to be largely influenced by the amount of dry matter intake but not highly influenced by the type of ration. The amount of Cr yield (recovery rate) was not statistically different from 100%. In real terms however, Cr recovery from calves which were on the liquid milk treatment was generally low. Such a recovery was associated with the fluid nature of the diet such that it could not intimately mix with the marker. Two methods of digestion were compared for the Cr concentration assays. A significantly higher (p <0.001) Cr concentration was obtained from faecal samples which were digested using a "high" bromate (HB) compared with "low" bromate (LB) digestion. Also within duplicate variations in Cr concentration were largely eliminated by using HB. Supplementation considerably improved ration digestibility, Soya (0.77), powder milk (0.79) and liquid milk (0.83) as compared with grass only ration (0.74) there was also a favourable response in the nitrogen retention (NR) of the calves on the liquid milk diet which were superior, while the grass-fed calves performed relatively poorly. The response may be associated with high efficiency with which digestible energy (DE) from the milk supplement was utilized for liveweight gain.