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    A study of lactational and reproductive performances of autumn or spring calving cows in commercial winter milk supply herds : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Animal Science, Department of Animal Science, Massey University, New Zealand
    (Massey University, 1996) Changʻendo, Francis Benjamin
    Data on lactational and reproductive performances for 1993 and 1994 of dairy cows which calved in autumn or in spring on eight commercial winter milk supply farms around Palmerston North were collected. The eight commercial winter milk supply herds had a calving spread condensed into autumn and spring seasons. There were 7689 calvings recorded involving 3787 cows. The lactational parameters measured were yields of milk fat and milk protein per lactation, and days in milk (DIM) per cow. The mean milk fat production for the autumn calved cows was 206 kg/cow and 166 kg milk protein/cow (372 kg milk solids) per lactation while the spring calved cows produced 199 kg milk fat/cow and 160 kg milk protein/cow (359 kg milk solids) per lactation. The mean lactation length (DIM) for the autumn calved cows was 282 days, while the spring calved cows had a mean lactation length of 258 days (P<0.05). The mean daily milk fat yield averaged across the days in milk was 0.73 kg per cow for the autumn calved cows while the spring calved cows had a mean daily milk fat yield of 0.77 kg/cow (P<0.05). The mean values of milk production in the second and third months of lactation were 18 litres per day and 17 litres per day for the autumn calved cows while spring calved cows produced 22 litres per day during the second month of lactation and 19 litres per day during the third month of lactation respectively. The reproductive parameters measured were calving interval (CI), 4 weeks submission rates (SR), 42 day non-return rates (NNR), services per conception, 4 week calving rates and empty rates. The autumn calved cows had a longer CI than the spring calved cows; 390 days vs 372 days (P<0.05). The autumn calved cows had a lower average 4 weeks SR than the spring calved cows; 71% vs 81% (P<0.05). The autumn calved cows had a lower average 42 day NNR (conception rate) than the spring calved cows; 55% vs 64% (P<0.05). The autumn calved cows had a higher average of services per conception than the spring calved cows; 1.9 vs 1.6 (P<0.05). The autumn calved cows had a lower 4 week calving rate than the spring calved cows; 41% vs 54% (P<0.05). The autumn calved cows had a higher average empty rate than the spring calved cows; 12% vs 10% (P<0.05). These results show that cows which calved in autumn actually produced larger yields of milk fat and milk protein per lactation than those which calved in spring. However, these higher yields were achieved in longer lactations, and the autumn cows produced lower average daily yields than the spring calved cows. The lower daily yields during the second and third months of lactation by the autumn cows, indicated that these cows were on a lower level of feeding at this stage than the spring calved cows. The autumn calved cows had lower values for all aspects of reproductive performance than the spring calved cows. This difference is probably due to, at least partly, to the lower level of feeding in early lactation. These herds are relatively high producing, and therefore it can be deduced that they are generally well managed. Nevertheless the autumn calved cows were fed less well in early lactation than the spring calved cows, causing slightly poorer performances.
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    The use of oestrous cows for the pre-collection preparation of mature bulls standing at an artificial breeding centre : a thesis presented to the Victoria University of Wellington in partial fulfilment of the requirements of the degree of Master of Agricultural Science
    (Massey University, 1962) Macmillan, K. L.
    Since 1949, a marked expansion in the commercial operation of artificial breeding has taken place in New Zealand. This expansion represents an increase from 1,400 inseminated cows in 1949, to 556,000 inseminated cows in 1961. (New Zealand Dairy Prod, and Marketing Board Ann, Rept. (1962)). The principle objective of the Artificial Breeding Service is to offer farmers the use of top sires from each of the main dairy breeds in New Zealand. These sires are selected on the basis of progeny test records. The rating which each proven sire receives is calculated from the butterfat production records of a sire's daughters. The butterfat records of each daughter are corrected for are differences and compared with the age-corrected average production of the herd-mates. Bulls selected for use as A.B. sires are placed at one of the two Artificial Breeding Centres which provide a Dominion-wide coverage. Because of the seasonal nature of daily farming in New Zealand, the bulk of the demand for semen occurs during the spring mating period, and since chilled semen is the principle form of service offered, the bulls experience a peak working period of eight to twelve weeks at this tise of the year. Ths objective in development at the Centres has been to obtain maximum coverage from top sires compatible with satisfactory conception rates. In 1961, the 49-day non-return rate to first inseminations with chilled semen was 63/3% (New Zealand Dairy Production and Marketing Board Ann. Rept. (1962)).
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    A study of some factors affecting the post-partum oestrous interval in suckled angus cows : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science at Massey University
    (Massey University, 1976) Morris, Stephen Todd
    The objectives of this study were to determine the length of interval from parturition to first oestrus and investigate factors that might influence this interval. Sixty-one records were collected in 1975 from the breeding herd at Massey University's No. 3 sheep farm Tuapaka, another 207 records covering the years 1971 to 1973 and 1975 were obtained from the herd of the Whatawhata Hill Country Research Station, Ministry of Agriculture and Fisheries, Hamilton. The Massey herd consisted of Angus cows aged 4-years and older while the Whatawhats Angus herd consisted of cows aged 2-years and older. Oestrus was detected at each location by the use of chin-ball mating harnesses attached to entire or vasectomised bulls. Management of the cows followed normal New Zealand hill country practices with the exception that in the Massey herd post-calving treatments were imposed. These treatments were: (i) On the hill throughout the trial (H) (ii) Removed from the pad at birth (PB) (iii) Removed from the pad at 20 days (P20) (iv) Removed from the pad at 4O days (P4O) After calving, cows and calves were grouped into three blocks according to calf age with treatments nested within blocks. The analysis consisted of a study of the relationships between the length of the interval from calving to first oestrus and the nutritional treatments, milk production, cow liveweight changes, and calf variables. The least squares means for post-partum interval to first oestrus were 79.2 days and 74.5 days for the Massey and Whatawhata herds, respectively. The regression of calving date significantly (P<0.01) influenced the post-partum interval in the Massey herd, but the effects of block, treatment, age of dam and sex of calf were non-significant. For the Whatawhata herd, year of record (P<0.001), age of dam (P<0.01) and the regression of calving date (P<0.001) all influenced the post-partum Interval. The sire of calf at foot and sex of calf were non-significant while the regression of cow liveweight change post-calving to mating approached significance (0.05
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    Genome wide association studies for temperament in New Zealand dairy cattle : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Animal Science in Animal Breeding and Genetics at Massey University, Palmerston North, New Zealand
    (Massey University, 2012) Chan, Fei Yi
    The aim of this thesis was to identify genomic regions associated with cow temperament in New Zealand dairy cattle. The data set used was provided by the Livestock Improvement Corporation, and contains estimated breeding values (EBV) for temperament of 3140 bulls of three breeds; Holstein-Friesian (HF), Jersey (JE) and Crossbreed (XB) born between 1994 and 2006. Biallelic genotype data were also provided containing 700,000 single nucleotide polymorphism (SNP) markers. Estimated breeding values for cow temperament were adjusted (Adj-EBVtemp) for age, percentage of North American Holstein genes (NAH%), percentage of New Zealand Holstein-Friesian (HF%) and percentage of Jersey (JE%). Using PLINK, the association between individual markers and temperament was investigated. PLINK was also used to produce output with genomic corrected p-values (GC) which adjusts for inflation based on the median chi-square statistic. Suggestive and genome-wide significance thresholds were set at -log10 (1e-4) and -log10 (5e-5) respectively. From literature review, the average estimate of heritability of temperament was 0.17, and average genetic correlation with milk yield was 0.165. JE bulls had the highest average EBV for temperament (0.0352 ± 0.239) followed by XB (0.0079 ± 0.217) and HF bulls (-0.0402 ± 0.256). PLINK analysis show BTA 4 to contain genome-wide significant genomic regions across all three breeds for Adj-EBVtemp. Further investigation on individual chromosomes provided no further information on significant genomic regions affecting temperament. A closer look at many of these regions show they are in domains known as “Junk DNA”. Results suggest that although genomic selection for temperament in dairy cattle is plausible, genetic gain via direct selection for this trait will be slow and desired effects may not be immediate.
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    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.