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    Studies on the fertility and breeding management of New Zealand dairy cows : a thesis presented to Massey University as a requirement for the degree of Doctor of Science
    (Massey University, 1982) Macmillan, K. L.
    This thesis reviews an extensive research program on the fertility of dairy catt1e in New Zealand. Most of the work was completed between 1967 and 1977. It involved studying numerous basic aspects of reproductive physiology by analysing extensive amounts of data either lodged within a large centralised recording system, or produced through the participating cooperation of herd owners or inseminators. New concepts were developed and old recommendations sometimes found to be inappropriate.
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    Pasture utilization in relation to New Zealand dairy farming : a thesis presented in part fulfilment of the requirements for the Animal Husbandry section of the degree of Master of Agricultural Science at Massey University, New Zealand
    (Massey University, 1949) McArthur, Alistair Thomas Giles
    The world shortage of food is the most serious crisis which faces mankind today. It is a crisis which has no earlier precedent and one for which remedial measures will be hard to find. The problem, first mentioned by Malthus in 1798, is one of limited food resources combined with an increasing world population. The basis of food production lies in the soil mantle of the world which is limited in extent and decreases yearly both in quantity and quality through the use of bad farming practices which lead to soil erosin. The present level of human nutrition throughout the world is far from adequate. In North .America and Australasia, the average daily consumption of calories per head is above 3000 but in the Middle East it is only 2400 while in the Far East it varies between 1700 and 2100, which is well below requirements (Fawcett (1948)). Not only are these people in need of more food energy but they also require more protein, minerals and vitamins. Livestock products are, of course, rich in these 'protective' foods and the expansion of livestock production will play an important part in raising the level of nut­rition of the world's population. [From Introduction]
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    Studies of variation in the rectal temperature, pulse rate, respiration rate and skin temperature of some New Zealand Jersey cows with particular reference to summer climatic conditions : a thesis presented in partial fulfilment of the requirements for the degree Master of Agricultural Science in the University of New Zealand
    (Massey University, 1959)
    The field of research known as Environmental Physiology covers Studies on the physiological responses of animals to variations in their immediate environment and on the adaptation of animals to environment. Generally, studies with cattle in this field have been pursued either in tropical environment or, lately, in very cold climate (see series of papers by MacDonald and Bell, 1958). The use of climatic chambers, such as those described by Brody (1948) and by Findlay (1950), has enabled research workers to study the effects on animals of a wide range of climatic variables but the results have a restricted application in the field. [From Introduction]
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    Some aspects of the development of rumen function in dairy calves reared on pasture : a thesis presented at Massey College in partial fulfilment of the requirements for the degree of Master of Agricultural Science in the Victoria University of Wellington
    (Massey University, 1962) Stewart, John Alexander
    Economy in feeding the ruminant is based on taking full advantage of rumen function. At birth however the rumen is not functional and the very young animal is dependent on a diet which it can digest without aid from microbial fermentation The need for a readily assimilated diet is normally fulfilled by the mothers milk. In the case of naturally reared animals this milk may continue to provide a significant proportion of the nutrients in the diet of the young animal even when rumen function has been established and it is capable of obtaining its nutrient requirements from grazing alone. Recognition of the fact that milk is an ideal food for young animals is reflected in the extended periods of milk feeding which in the past have been characteristic of the rations fed to artificially reared dairy stock. However there may be several disadvantages in such a practice, not the least of which being the amounts of milk and labour involved. In the search for more economical methods of calf rearing, the possibility of weaning at an earlier age has been investigated. Calves have been weaned as early as 3 weeks of age (Preston 1960), and it is known that calves which are provided with high quality pasture may be weaned at about 8 weeks of age without ill effect. [From Introduction]
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    Studies of grazing behaviour by lactating cows during winter, spring and summer : a thesis presented in partial fulfillment of the requirements for the degree of Master of Applied Science in Animal Science at Massey University
    (Massey University, 1999) Watson, Lisa A
    The work outlined in this thesis was intended to study the grazing behaviour of lactating cows during winter, spring and early summer, and the effects of maize silage supplementation during winter. It also derived monthly rising plate meter equations over the period of the experiments, in order to assist with the estimation of cow intake and sward characteristics. Supplementation influenced the quantity and relative proportions of grazing, ruminating and idling times. Total grazing times were 546 vs. 615-min./day, and total rumination times 403 vs. 333-min./day for supplemented and non-supplemented cows respectively. Substitution of pasture for maize silage occurred, with reductions in grazing time averaging 26-minutes per kg DM eaten as maize silage. Rumination values per kg of total DM eaten were similar at 29-minutes (supplemented) and 27-minutes (non- supplemented). Intake rate of pasture was not affected by offering maize silage as a supplement, but grazing time was reduced. Cows preferred to graze during daylight hours, spending 47-57% of daylight hours grazing irrespective of daylength. Grazing activity peaked after milkings, and before dusk. Autumn and spring calved cows were grazed together in two experiments in the spring and summer of 1998. Stage of lactation had no effect on bite rate, bite weight, and intake rate ot herbage. Grazing times were related to metabolic requirements, and grazing behaviour was similar for cows which had calved in autumn or in spring. Times for ruminating and grazing were similar for heifers and mature cows, with similar components of day and night-time grazing. Heifers have a lower intake rate (23 vs. 27-g DM/min), and smaller bite weights (423 vs. 507-mg DM/bite) without a faster bite rate (58 vs.56-bites/min). Heifers also ruminated for longer per kg DM eaten, with similar ruminating times to mature cows (380 vs. 380-min/cow/day), despite their smaller daily pasture intake (12.9 vs. 15.3-kg DM/cow). It is suggested that the grazing behaviour of heifers is influenced by social factors, such as their dominance position in a herd. Monthly rising plate meter equations were derived between July 1998 and February 1999. When used to rank pastures for grazing order, the importance of the slope rather than the intercept was demonstrated. However when the rising plate meter was being used to compare pasture with required target values (such as average farm pasture cover, and post-grazing herbage mass), the intercept was also important, to give an accurate pasture mass value.
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    Studies on the effects of grazing regime on sward and dairy cow performance : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University
    (Massey University, 1986) Hoogendoorn, Coby Jean
    Grazed herbage is the major source of feed for dairy cows in New Zealand. The efficiency with which herbage grown is converted into animal product is thus of major concern to the dairy industry. The objectives of the present study were to assess sward response to different grazing regimes over a range of seasons, and to measure the performance, in short term trials, of cows grazing the resultant sward types over a range of herbage dry matter allowances (DA). Seasonal effects on sward structure and composition were great, with the effect of season often interacting with grazing regime imposed. Grazing regime had the greatest influence on sward characteristics in late spring. The cultivar mixture sown had a much less significant effect on sward characteristics measured. Swards grazed intensely and frequently had the lowest percentages of senescent matter, the highest values for herbage quality (DMD and N %) and optimal levels and patterns of NHA throughout the year. Intense grazint or topping (I) versus lenient grazing (L) in spring resulted in those swards maintaining high percentages of grass leaf and clover, low percentages of grass stem and senescent matter and a high herbage quality into early summer. The effect of sward type on dry matter intake (DMI) in early summer was variable, but milk and milk protein yield and sometimes milk fat yield were greater for cows grazing the I swards, at both a restricted and generous DA. When a common leaf allowance (LA) was offered, there were no significant differences in DMis or production between cows grazing the Land I swards. LA, rather than DA, was the best predictor of DMI and milk and milk protein yield over the three grazing trials conducted in early summer. Swards that had been allowed to regrow for 60 versus 120 days in autumn/winter had greater percentages of clover, lower percentages of senescent matter and a higher herbage quality in early spring, although pre-grazing total DM masses were lower. At a common nominal DA, milk, milk fat, and milk protein yields were greater on the 60 day regrowth swards despite DMis being similar. In all trials greater milk yields were attributed to greater percentages of grass leaf and clover and lower percentages of senescent matter and thus a higher herbage quality, both in the herbage consumed and on offer. Irrespective of sward type or DA on offer, the percentage of grass leaf was higher and the percentage of senescent matter lower, in the diet than that present in the herbage on offer. The results of the present study emphasize the importance of maintaining swards with a high percentage of grass leaf and clover and a minimal percentage of senescent matter. This is best achieved by maintaining an intense and frequent defoliation regime, especially during reproductive growth in spring.
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    Observations on ruminant fat metabolism with particular relation to lactation : a thesis presented in partial fulfilment of the requirements for the degree of M. Agr. Sc. of the University of New Zealand
    (Massey University, 1949) Mayhead, J W
    In that animal fat is a major economic "building block" the mechanism of its production has attracted particular study. Although observations regarding digestion of fats may be traced back as far as those of Asellius in 1622 it was in 1843 that specific investigations into body fat production were first instituted by Lawes and Gilbert. From 1900 onwards biochemical research has made its greatest advances but, in spite of the volume of literature published on the subject of fat metabolism the state of knowledge in this field may yet be in its infancy. The three main experiments to be described relate principally to the changes effected in the degree of unsaturation of milk fat from dairy cows when highly unsaturated oils are included in the daily ration. The immediate effects of short-term inanition are also investigated. Two minor experiments are described; the first concerning the tracing of ingested stained fat into the milk and depot fats of simple-stomached animals; the second relation to the keeping qualities of milk fats of varying degrees of unsaturation.
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    The effect on food intake and milk production of adding concentrate to the ration of cows fed pasture : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science at Massey University
    (Massey University, 1967) Taparia, A. L.
    It has long been appreciated that well managed leafy pasture will provide sufficient energy and protein for high milk production. However, because of seasonality of pasture production there are periods in the year when the supply of pasture is deficient. Hay and silage are used to supplement pasture during these periods of shortages on New Zealand dairy farms, but are limited in their ability to maintain high levels of milk production, particularly early in lactation. Thus recourse may have to be made to the use of concentrates to maintain milk production during periods of pasture shortage. The limited amount of experimental work conducted in New Zealand on the use of concentrates (Hancock, 1953; Wallace, 1957) indicated that their use may be worthwhile. However, information on the effects of supplementing pasture with concentrates under controlled (indoor) experimental conditions is non-existent under New Zealand conditions. Results obtained by overseas workers on the effect of concentrate feeding on milk production suggest that responses have been most erratic, especially when concentrates have been fed with pasture. In general these responses were less than would have been expected on the basis of feeding standards. Reports on supplementary feeding of dairy cows by Corbett and Boyne (1958), MacLusky (1955) and Seath et. al. (1962) suggest that the concentrated fed acted as a substitute for pasture. In all of these experiments, however, the intake of pasture was measured by indirect methods. Taking the above points into consideration two experiments were conducted. The first one was a small grazing experiment with the object of studying the effects of concentrates on milk yield and composition and to obtain experience in the problems of experimentation in a simple continuous trial using 16 Friesian cows. The other experiment involved nine Jersey cows and was mainly designed to study the effect of feeding concentrates on voluntary intake of pasture. This experiment consisted of a 3 x 3 Latin square replicated three times, with squares being run concurrently. Measurements of milk yield and milk composition were also carried out. Additional information was obtained on the rate of passage of feedstuffs with some of the cows, on digestibility of feeds with sex wethers, and rumen fermentation studies with four (extra) fistulated cows.
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    A study of the effect of the digestibility of hay on its feeding value when given to lactating cows grazing on pasture : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science, Department of Animal Science, Massey University
    (Massey University, 1990) Sangsritavong, Sunan
    Sixteen cows with an average milk yield of 20 litres per day, were randomly allocated to two treatment groups. One group was supplemented with high digestibility hay (57 .3% DMD) while the other group was supplemented with low digestibility hay (52.0% DMD). Cows in both treatments grazed on pasture during the night time and were stall-fed with either high or low digestibility hay during the day time. The pastures were predominantly of perennial ryegrass (Lolium perene). The experiment was carried out for 28 days in September 1988. The two treatment groups were given a common pasture allowance of 11-12 kgDM per cow per 12 hour period of grazing. Hay intake (fed ad libitum), pasture intake, milk yield, milk composition, liveweight and condition score were measured. Herbage intake was estimated by the sward cutting technique and was 3.85 and 4.30 kgDM per cow per day for the high and low digestibility hay groups respectively. The difference between the groups in intake was significant (P<0.05). Daily intake of high digestibility hay (8.65 kgDM per cow) was significantly (P<0.0001) greater than the consumption of low digestibility hay (6.53 kgDM per cow). The estimated values for daily metabolisable energy intake were 115 MJ per cow and 99 MJ per cow for the high digestibility and low digestibility hay groups respectively. Residual herbage mass was slightly higher (1130 v 1100 kgDM per hectare), but not significantly, when cows were supplemented by high digestibility hay. Substitution rate for the increase in hay intake was -0.45 kgDM pasture intake for an increase of 2.12 kgDM of hay intake or 0.21 kgDM pasture per one kgDM increase in hay intake. Cows fed on the high digestibility hay produced slightly more milk than those on the low digestibility hay. The difference was significant (P<0.01) in week 1 but not significant thereafter. Yields of milk constituents were also slightly increased for cows fed on the high digestibility hay. Digestibility of hay had small and insignificant effects on the concentrations of milk fat, milk protein and milk lactose. However the concentration of milk fat and milk protein were slightly higher for cows fed low digestibility hay. Cows fed high digestibility hay gained significantly more liveweight (P<0.05) and condition score (P
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    Accounting for scale effects in genetic evaluation of New Zealand dairy cattle : a thesis presented in partial fulfilment for the degree of Master of Agricultural Science in Animal Science at Massey University
    (Massey University, 1994) Lopez-Villalobos, Nicolas
    It is well known that variation in lactation yields tends to increase with average production. Failure to account for this scale effect may cause overestimation of genetic merit for sires with a majority of daughters in high-variation herds and vice-versa. The current system of sire evaluation in New Zealand overcomes this problem by expressing daughters performance as a proportion of contemporary average performance. The objectives of this study were to quantify the magnitude of scaling (heterogeneous variance), and to identify methods to stabilise the variance of milkfat yields for use in the genetic evaluation system of dairy cattle through best linear unbiased prediction (BLUP) using an animal model across breeds. Lactation records of dairy cows calving between 1986 and 1989 were obtained from the Livestock Improvement Corporation of the New Zealand Dairy Board. There were milkfat yields from 2,004,854 lactations in 83,805 contemporary groups (herdyear- age; HYA). The data were divided into three equal-sized subsets based on HYA mean; these being (kg milkfat ± sd) High (H), 172 ± 28; Medium (M), 152 ± 26; and Low (L), 139 ± 25. The methods investigated for the accounting of scaling were: adjustment by the HYA sd (SD-adjustment); scaling by the HYA mean (MEAN-correction); and natural logarithmic transformation (LOG-transformation) of milkfat yield. The overall correlation between HY A means and HYA sd's was 0.44. This value was reduced to 0.31 in SD-adjusted, -0.27 in the MEAN-corrected and -0.24 in the LOG-transformed data. Ideally, the transformed data should exhibit independence between the mean and standard deviation. Breeding values of sires were separately estimated from each data subset using a mixed model. Product-moment and rank correlations between breeding values for sires estimated from the independent subsets and with variable minimum number of daughters were in the overall comparisons (L-M, L-H and M-H) lower than expected correlations, reflecting inaccuracies in sire evaluation when scaling is ignored. Product-moment and rank correlations were similar for SD-adjustment and MEAN-correction, but LOGtransformation reduced the calculated correlations in the L-M, L-H and M-H comparisons. Estimates of the genetic correlations between production in pairs of environments were obtained from the ratio of observed to expected correlations. These estimates ranged from 0.82 to 1.01 for the linear yields. Estimates of genetic correlations were similar for SD-adjusted and MEAN-corrected data, but for LOG-transformed data these were reduced, especially in the L-H comparison which ranged from 0.77 to 0.87. Results confirm the problem of scaling on genetic evaluation of New Zealand dairy cattle. MEAN-correction and LOG-transformation methods are not appropriate because they tend to overcorrect the scaling problem. SD-adjustment is not satisfactory but seems to be more appropriate than no adjustment. An alternative method is proposed based on a Bayesian approach, which takes into account any relationship between variance and mean.