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The development of a computer model for the replacement of dairy cattle in seasonally calving herds in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Master of Veterinary Studies at Massey University
(Massey University, 1998) Crabb, Helen K.
A culling model for use in seasonally calving New Zealand dairy herds (CowCHOP) was developed. The model uses information retrieved from an on farm information system (DairyWIN) as well as farmer input to calculate an economic ranking of all animals within the dairy herd. This economic ranking is used to identify those animals that are most and least desirable for retention in the herd. Culling information was obtained from current Dairy MAN user herds. This information was analysed using survival analysis to determine the current removal risks of cattle from DairyMAN herds for inclusion in the model. Additional economic information was obtained from the literature and incorporated into the CowCHOP model. To understand removal risks and rates for culling, herd demographic data was analysis from a study on reproductive performance for the 1993/94 season. The study was limited to spring calving seasonal herds, typical of the New Zealand dairy industry. The New Zealand dairy industry is reliant on a largely pasture based production system which entails that herds calve annually during the spring months with a condensed calving pattern to optimise pasture utilisation. Cows are dried off in the late autumn for a dry period prior to the onset of calving the next season. This management system results in two periods of the season where cows are at greatest risk for removal, primarily early lactation and drying off.
Behaviour of single-suckled Angus cattle from calving to weaning : 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, 1978) Aitken, Victoria Robin
The main objective of this study was the investigation of behaviours which might influence the number and/or weight of calf weaned from single-suckled Angus cows. The behaviour patterns involved were those relevant to parturition, the cow-calf bond and nursing. The effect of such factors as maternal experience, sex, and age of calf and the presence of non-lactating cows were also investigated. In addition, the liveweight of the calves was taken at birth and thereafter at regular intervals throughout the course of the study. Observations began on average 31 d (range 4 to 65 d) pre-partum and continued until 3 weeks post-weaning, c. 33 weeks after the start of the investigation and involved >900 h of field observations. Eighteen pregnancy-tested Angus cows were involved of which 14 calved. Of these,5 primiparous and 6 multiparous reared their own calf. Two calves, 1 born from a primigravid and the other born from a multigravid cow, appeared to die as the result of abnormal maternal behaviour. These maternal behaviours resulted in either physical injury to the neonate and/or refusal by the cow to allow the calf to nurse. The latter behaviour was followed by hypothermia in the calf, although adverse weather conditions probably accentuated this heat loss. Two primigravid cows rejected their calves and had to be isolated for up to 5 d and restrained before the cow would accept the calf's presence and nursing activities. A method of predicting the order and time of calving for each cow was devised. Determination of the calving order was possible in 12 of the 14 cows prior to the birth of the first calf. The use of 24 physical signs allowed prediction of calving time to within 48 h in all 14 cows. Changes in such behaviours as posture and social activity were associated with calving within the following 3 to 4 h in all except 1 cow. This animal was found to exhibit dystocia, i.e., an extended parturition of >19 h. On average the physical signs were observed before the behaviours and more cows were recorded for the presence of physical signs than for behavioural signs. However, there was wide variation in the number of signs recorded and the time they were first observed for each of the cows. No single sign could be effectively used for prediction of either calving order or the time of calving, i.e., delivery of the calf. There was a highly significant difference between the primigravid and multigravid cows in their calving time. The heifers showed a decided tendency to calve during daylight whilst equal numbers of the older cows calved during daylight as during darkness. The area chosen for calving did not appear to be random. A very highly significant number of cows calved in the same area which provided the parturient cow with visual isolation up to 20 m. The importance of such isolation and subsequent localization to a specific area on the early occurrence of nursing and primary socialization was demonstrated. Determination of onset and termination of first-stage labour on the basis of either physical or behavioural criteria was only an approximation. Overall, it was more difficult to determine the duration of the various stages of parturition using behaviours than when using physical signs, although there was a tendency for the different behavioural parameters to occur more frequently and/or at greater intensity at specific times during the process. The effect of experience on maternal behaviour was demonstrated on a number of occasions. For example, with one exception all the primiparous cows showed a significantly shorter duration of maternal grooming of the neonate than did the multiparous cows. With the exception of 1 multiparous cow, abnormal maternal behaviour was observed only from the primipara. Five of these 6 cows showed some form of agonism on first seeing the neonate. In all except 1 cow this ended several minutes after the cow had investigated the calf. Other abnormal behaviours such as orientation toward the calf during its teat-seeking activities were recorded only amongst the first calvers and on all occasions resulted in a longer time taken prior to location of the teat by the calf. On termination of the dam-offspring association at weaning the response from cows and calves was apparent in changes in their behaviour. During the following 7 d the calves showed a very high level of unity in their activities and spatial distribution. As well the form of social interaction changed and became predominantly agonistic. This resulted in rapid establishment of a social rank which appeared to decrease further agonisra and instead increased such epimeletic behaviour as grooming. Despite these changes in behaviour the liveweight of the calves did not significantly change from 11 d pre-weaning until termination of the study 21 d later. The cows reacted to weaning by increased aggregation, vocalization and walking for up to 9 d post-weaning. These changes were reflected in an apparent decrease in grazing and rumination duration. Fence damage and localized areas of severe pugging was also recorded. Nursing was investigated for the form and degree of occurrence of both maternal and filial behaviours, including cross- and non-nutritional nursing, as well as the pattern of sucking, i.e., sucking frequency, duration and time spent nursing, and the diurnal and circadian rhythms.
A study of management practices and productive performance on a sample of hill country sheep farms in north-east Wairarapa : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Farm Management at Massey University
(Massey University, 1984) Parker, W. J.
The research reported in this thesis was directed towards the analysis of the inter-relationships between management practices and productive performance on a survey group of 30 north-east Wairarapa hill country farms. The initial survey, which essentially concentrated on the period between ewe weaning and tupping, incorporated a combination of mail and personal interview techniques. In addition, sample liveweights of ewe hoggets in autumn (April 1) and of two tooth and mixed aged (MA) ewes prior to mating were obtained to describe production levels more objectively. Preliminary results and appanent opportunities for improving the management of existing production systems were presented to the survey farmers as a group. As a consequence, a follow-up mail survey directed at management practices and associated production levels during the winter and spring (post-mating to weaning) was implemented in August 1983. Sample liveweights of ewe hoggets at spring shearing and ewe and lamb weights at weaning were collected. Results were discussed with the 29 participating farmers. Descriptive statistical methods (e.g. frequencies, cross-tabulation) were initially used to describe farm physical characteristics and the management systems employed. Subsequently, multivariate techniques (regression and MANOVA) were used to estimate the relative importance of different management strategies and farm physical characteristics on system performance. The major recommendation from this study is that increased emphasis should be placed on rearing ewe lambs so that they achieve a liveweight of 35kg or more by May 1. The average April 1 ewe lamb liveweight on the survey farms in 1983 was 30.2kg (range, 18.7 - 40.0 kg). Other recommendations include mid-October or later commencement of calving, delaying ewe mating until April 1, earlier weaning of lambs and calves in dry summer areas (8-10 weeks and 12 weeks average age respectively) and increasing the winter rotation lengths of ewes. It is suggested that a large proportion of the potential level of production on hill country can be realised inexpensively through relatively small changes to existing management practices (such as those mentioned above) and associated management control of production system performance.
Production characteristics and responses to feeding by Friesian cows fat and thin at calving of high and low genetic merit : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science at Massey University
(Massey University, 1984) Ngarmsak, Supachai
A review of literature is given on herbage intake achieved by grazing lactating dairy cows. The lactating cows have higher herbage intake than non-lactating cows. Condition at calving may have an effect on herbage intake by dairy cows. The theory of response, the response to feeding both before and after calving are also reviewed. The literature is reviewed which discusses responses to feeding in Europe (where diet of the cows are mainly concentrates) and in Australia and New Zealand where dairy cows graze mainly on pasture. The evidences of improving cows quality by selection are given with special emphasis on New Zealand dairy cows. Genetic merit of a New Zealand cow for milkfat production is measured by her breeding index (BI). The main objective of the work was to study production characteristics and response to feeding in early lactation by Friesian cows, fat and thin at calving, of high and low genetic merit. Over lactation High BI cows produced more than Low BI cows. The differences between BI groups in milkfat production was in close agreement with the expected differences based on BI's. High BI cows had slightly higher herbage intake than Low BI cows but no signifcant differences were found. Low BI cows were fatter than High BI cows. No significant difference in fatty acid composition of milk between the BI groups was found. Over lactation Fat cows produced more milkfat than Thin cows. Improving 1 condition score at calving was associated with an increase of 10.5 kg milkfat. No significant differences in response to feeding in early lactation between High BI and Low BI cows nor between Fat and Thin cows were found. The response to moderate underfeeding during early lactation was mainly immediate response. The residual effects of underfeeding were small and confined to 2 weeks after returning to full feeding. Underfeeding significantly increased mole % of long chain fatty acids of milk and significantly decreased mole % of short chain fatty acids.
Effect of premating supplementation with monopropylene glycol on reproductive performance of dairy cows : a field trial : a thesis presented in partial fulfillment of the requirements for the degree of Master of Science in Animal Science at Massey University, Turitea, Palmerston North, New Zealand
(Massey University, 2005) Tuñon, Gonzalo Enrique
Low body condition score (BCS) at calving is associated with extended time to resume cycling in dairy cows. Prolonged postpartum anoestrous intervals (PPAI) are the major source of infertility in New Zealand dairy cows. Postpartum supplementation with monopropylene glycol (MPG), under controlled experimental conditions, was previously shown to reduce PPAI in heifers. This experiment tested this treatment in four large commercial dairy herds. During the 6-week period preceding the planned start of mating (PSM; Week 0), cows were drenched either once (MPGxl) or twice (MPGx2) daily with 200 ml MPG, or served as untreated controls (Con). A total of 2,122 cows were included in the analysis. Analyses were confined to the group of cows that were anoestrus at Week 6 or calved between Week - 6 and Week -4 relative to PSM (n = 684 to 714 per treatment). None of the four variables: oestrous behaviour during the treatment period, anoestrous rate one week before PSM, 3-week submission rate or 3-week pregnancy rate were affected by MPG. However, MPG did increase the 6-week and final pregnancy rates (P<0.005). with MPGxl having higher values (74.6% and 92.1%) than MPGx2 (69.1 and 88.5%) and Controls (67.7% and 88.1%), respectively. MPG-treated cows also produced more milk protein than the control-cows, by 0.01 and 0.017 kg of milk protein per day for MPGxl and MPGx2, respectively (P = 0.02), evidence of a metabolic effect of MPG. Recent studies suggest that diets that are optimal for follicle growth are not necessarily optimal for oocyte quality and subsequent embryo survival. It is hypothesised that MPGxl had positive effects on the follicle/oocyte through gonadotrophin-independent mechanisms and that MPGx2 had negative effects on the embryo. Probably the gonadotrophin-dependent effects necessary for ovulation could not be exerted in the present study because MPG was not administered for sufficient time to effect the LH surge. Both change in body condition score between Week - 6 and Week - 1, and proportion of cows that were anoestrus at Week -1, were influenced by herd, age and time of calving (P<0.05) but not by treatment (P>0.1). Treatment did not influence the proportion of anoestrous cows, treated with progesterone, which were inseminated after oestrus detection (n = 263). Change in BCS affected both milk yield and pregnancy rates, with cows that gained BCS producing less milk (P = 0.01) but showing higher 6-week pregnancy rates (P<0.05). This study highlighted that key factors influencing the percentage of anoestrus at PSM are cow age, time of calving and management of the herd.
The wintering and calving of Angus beef cows on a sawdust pad : 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, 1974) Pleasants, Anthony Bryan
A system of wintering and calving beef cows on a sawdust cattle pad was compared with the traditional method of wintering unsupplemented cows on hill country pasture. Comparisons were made over four years, beginning in 1970. Two herds of Angus beef cows were used in the experiment. One herd was originally the Massey University Stud herd, which included approximately 50 cows aged from three to ten. Three-year-old replacements were added to this herd each year. This herd was designated the Stud herd. The other herd designated the Commercial herd, was based on 67 yearling heifers bought in 1969. These cows were all of the same age, and no replacements were added. In 1969 25 cows from this herd were mated to calve at two-years-of-age. The two herds were run together as one unit during the trial, distinction only being made for the purpose of statistical analysis. The pad consists of two yards with sawdust packed on top of tile drains. A concrete apron runs along the side where the feeding racks are situated. A stand of pampas grass protects the pad from the prevailing wind. Half gates were installed, and the bottom rails of the yard were removed to allow the calves to get out and creep feed on the adjoining pasture. Three weeks before calving begins cows were allotted to the pad or the hill treatment using a table of random numbers. In 1971, 1972, 1973 a switchover design was adopted, whereby some animals alternated between the two treatments in successive years, while others wintered on the same treatments. Over 1970 the cows were confined all the time. In 1971 the cows on pad I were allowed to break feed saved pasture over a week. In 1972 and 1973 the cows and calves were removed from the pad for three and four days after birth respectively. This enabled the calf to obtain colostrum without interference, allowed the cow to build up reserves of vitamin A, helped form a bond between the calf and its mother, and enabled the calf to have the benefit of a healthier environment for the first days of its life. This practice appeared to have some merit in reducing the incidence of calf scours. While confined the cows were fed hay, barley straw, and barley meal. In 1970 some experimentation in feeding levels was necessary, and in 1971, 1972 and 1973, 4.3 kg hay, 2.3 kg barley straw and 0.6 kg of barley meal per head per day were fed. In 1972 and 1973 feeding once a day was compared with feeding the same ration once every second day. Before the cows were confined, the top three inches of sawdust was removed and the sawdust and timberwork sprayed with a 10% solution Of formalin. In 1973 the concrete apron was scraped off weekly with a tractor and blade. Milk determinations were made by the weigh-nurse-weigh method following a 16 hour separation. The cows entered the pad about the second week in July, and remained there until the end of September, when they joined their contemporaries on the hill. Generally the cows wintered on the pad lost more weight than the cows grazed on the hill, although the magnitude of the weight lost varied considerably between years. Birth weights of the calves born on the pad were generally about 2 kg below that of the calves born on the hill. However, there were no clear differences between treatments for the weaning weights. Limited information gathered on the cow milk production indicated that although milk weights of the cows on the pad were lower during confinement, handicapping the growth of their calves, there appeared to be a surge of milk production in these animals upon their release to the hill pasture, in some years. This resulted in an increased growth rate of the calves from the pad at this time. Reproductive performance of the three-year-old and mature cows as measured by thoir calving interval was unaffected by the winter treatments. The performance of the first calving two-year-old heifers from the Commercial herd in 1970 was adversely affected by the pad treatment. Birth weights and weaning weights were reduced and 26.5% of the heifers failed to rebreed the following season. Nevertheless subsequent performance demonstrated no further effect of calving at two-years-of-age under adverse conditions. There was no effect on the calf performance of feeding everyday against feeding every second day. Neither was calf performance affected by any of the switching treatments imposed between years. Differences due to the effect of sex and age of dam were similar to those reported in the literature for birth weight and weaning weight. As the four-year-old dams performed surprisingly well in this study an age-of-dam x treatment interaction was suspected. There was an indeterminate effect of sex on the milk yield of the dam. Regressions involving the age of the calf on the weight at various points revealed a strong association of growth with climatic variables. Since the period under study included stormy weather and long droughts this complicated the evaluation of calf growth data. It was concluded that the pad system of wintering and calving beef cows can be operated as a commercial system in the manner described. A discussion of pad husbandry is given, and recommendations are made.
The induction of calving using betamethasone : and the pharmacological activity of selected formulations having different rates of absorption : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University
(Massey University, 1982) MacDiarmid, Stuart Campbell
A series of experiments was undertaken in cows to study the disposition and duration of activity of selected formulations of the synthetic corticosteroid betamethasone (BM). The aim was to select a combination of formulations which would be suitable for use in a two-injection treatment regimen designed to induce premature parturition in cattle. In an initial experiment, 10 cows each received a subcutaneous injection of 20 ml of 2 mg/ml aqueous suspension of BM, 10 received 2 ml of a 20 mg/ml suspension and a further 10 cows served as saline-treated controls. The BM formulations differed only in their solids:vehicle ratio. Plasma BM, cortisol and glucose concentrations, and differential blood cell counts were studied for 3 days before, and for 19 days after, treatment. The 2 mg/ml suspension produced a markedly higher peak plasma BM concentration than the 20 mg/ml suspension. However, plasma BM levels tended to be maintained for longer by the suspension having the higher solids:vehicle ratio. The administration of BM resulted in depression of early-morning cortisol concentrations, elevation of plasma glucose levels, and elevation of circulating neutrophil numbers. The magnitude and duration of these changes was related to the solids:vehicle ratio of the injected suspensions, with the more concentrated formulation producing effects of greater duration. A second experiment involved 9 cows which were divided into 3 groups, each of which was treated at a dose rate of 0.1 mg/Kg with sodium phosphate solution or a 2 mg/ml BM suspension or a 20 mg/ml BM suspension. Over a period of several weeks each cow received its allocated formulation by each of 3 routes; intravenous, intramusuclar and subcutaneous. The bioavailability of the BM suspensions was low and the solids:vehicle ratio exerted a profound effect on the rate at which the steroid was absorbed. The disposition curves of the BM solution were similar regardless of the route of administration and the plasma half-life values of BM sodium phosphate, estimated from 3 experiments in each of 3 cows, were 5.64, 6.06 and 6.43 hours. Ten cows were included in a third experiment. They were treated by subcutaneous injection with 2 ml of a 10 mg/ml BM suspension; a preparation intended for use in the induction of calving. Mean plasma concentrations of BM and glucose were elevated above pre-treatment values for 4 days and 8 days respectively. Mean plasma cortisol levels were profoundly depressed for 2 weeks and in some individuals showed no signs of returning to normal 4 weeks after treatment. Two field trials, involving 619 and 553 cows respectively, were conducted to assess the suitability of BM formulations for the induction of premature calving in commercial dairy herds. In the first trial, the mean stage of pregnancy at which cows were treated was approximately 250 days. Cows received an initial injection of either 2 ml of a 10 mg/ml suspension of BM, 2 ml of a 15 mg/ml BM suspension or 4 ml of a 5 mg/ml suspension of dexamethasone trimethylacetate (DTMA). All cows which had not calved within 10 days of this initial treatment received a 12.5 ml dose of a 2 mg/ml suspension of BM. In comparison with those cows treated with DTMA, significantly fewer cows treated with the concentrated BM suspensions required a second corticosteroid injection. In all other respects, such as calf mortality, incidence of retained foetal membranes and maternal illnesses, the results of the treatments were not significantly different. The 10 mg/ml BM suspension was therefore deemed to be suitable for use in the induction of calving. The second field trial confirmed the suitability of the 10 mg/ml suspension as an initial treatment to induce calving. Cows which had not calved within 7 days of the initial treatment were injected with 20 mg of BM, either as a 2 mg/ml suspension or as a 2 mg/ml solution of the sodium phosphate ester. After the second steroid injection, those cows which had received the more rapidly absorbed BM solution calved sooner than those which had been treated with the 2 mg/ml suspension. The results of these studies clearly showed that the duration of activity of BM suspensions could be prolonged by increasing their solids:vehicle ratio. It was also shown that a treatment regimen consisting of an initial injection of a 10 mg/ml BM suspension, followed 7 to 10 days later by an injection of a more rapidly absorbed BM formulation, was suitable for the induction of calving as currently practised in New Zealand.
Systems, component, and modelling studies of pasture-based dairy systems in which the cows calve at different times of the year : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University, Palmerston North, New Zealand
(Massey University, 2000) García, Sergio Carlos
The New Zealand's dairy system is characterised by a concentrated calving period in late winter-early spring, which aims to synchronise cows' feed requirements with the seasonal pattern of pasture growth, but which also results in an uneven distribution of milk supply to the factories. Changing the calving season of some herds from spring into autumn could improve the overall efficiency of the dairy industry. However, pasture-based autumn-calving systems are usually perceived to be less "efficient", because of the lack of synchrony between feed supply (grazed pasture) and feed requirements. One conclusion of the literature review (Chapter 1) was to hypothesise that autumn- and spring-calving systems would perform at similar levels provided that sufficient supplementary feed was available during wintertime. This thesis integrated three experimental approaches (system, component, and modelling) in order to test the above hypothesis, and to investigate the physical performance of pasture-based dairy systems that differed in their calving dates. A 3-year system study conducted at No 1 Dairy Farm, Massey University, in which autumn, spring, and autumn/spring calving systems were compared, showed that all systems achieved similar performances and overall efficiencies (Chapter 2). A key factor for this was the greater total yields by the autumn-calved cows, due mainly to their greater yields in mid and late lactation and their longer lactations (Chapter 3). A new technique that combines the n-alkanes and 13C methods in order to quantify herbage and maize silage DM intakes by individual grazing cows which are given access to the silage as a group, was developed and validated (Chapter 4), and re-evaluated in a separate study (Chapter 5). Overall, individual cows differed considerably in their intakes of maize silage DM, but this variation was not always related to variation in milk yields. An innovative, dynamic, interactive simulator of seasonal pasture-based dairy farms (IDFS) was developed as part of this thesis (Chapter 6). The model allows computer experiments to be run, with pastures and cows managed on the basis of logical decision rules; therefore, it resembles real farm management. The user makes decisions (which paddocks are to be grazed, pre- and post-grazing herbage mass, supplement feeding, etc) continuously, and can see the impact of his/her management decisions on the graphical interface provided. Based on comparisons with actual data, it was concluded that IDFS simulates the main components of seasonal dairy farms with reasonable realism (Chapter 7), although the model is at an early stage of development and has not been completely validated. In conclusion, this thesis has 1) demonstrated that pasture-based systems with contrasting calving dates can achieve similar physical performances provided that supplementary feeds are available, and 2) developed two new tools (quantification of herbage and maize silage intakes by individual cows, and the IDFS model) that can be applied in future systems research.

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