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ATP-citrate lyase (ACL) is one of the major lipogenic enzymes. It catalyzes the synthesis of acetyl-CoA from citrate in the cytosol. This is the first committed step towards the conversion of carbohydrate precursors into fatty acids. Acetyl-CoA serves as the major precursor for lipogenesis and cholestogenesis. Examination of this pathway shows that the rate of fatty acid synthesis from glucose is dependent on the activity of ACL. In rats the activity of this enzyme can be increased by feeding high carbohydrate diet and reduced to low levels by fasting. These changes are regulated at the transcriptional level. The ruminant provides a good model to study the regulation of expression of ACL. The levels of this enzyme are high in young ruminants, but fall to very low levels once a functional rumen is developed. In adult ruminants, acetyl-CoA for fatty acid synthesis is produced directly from acetate formed by microbial fermentation in the rumen and carried to the peripheral tissues. The down-regulation of this enzyme can be reversed by the administration of glucogenic precursors by a route that bypasses their fermentation to volatile fatty acids in the rumen. An understanding of the regulation of expression of ACL in the adult ruminant and a comparison with monogastric animals will provide significant new information about the regulation of the conversion of carbohydrate into fat. A probe containing exon 2 to exon 3 of the rat ACL gene was prepared. Its specificity to bovine genomic DNA was verified and the probe was then used to screen a bovine λ genomic library. A 17 kb clone was isolated. The restriction map of this clone was determined with several enzymes. A part of this clone (9490 base pairs) was sequenced and shown to consist of a 3 kb promoter region and doenstream seqence as far as intron 3 of bovine ACL. The transcription start sites were determined by 5'RACE. Several important features of this gene were discovered by computer analysis of the sequence. Two ke

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 th

Longitudinal growth experiments using rats, lambs, and heifers were analysed by establishing linear relationships between ages, live weights and body lengths in individual animals. Various analytical methods were investigated. Statistical and biological reasons forced the logarithmic transformation of weights and lengths, a three parameter logarithmic metameter was used if means and standard deviations were correlated on a two parameter logarithmic metameter. Age was transformed to give linear relationships. Changes to the experimental design and analysis of growth experiments were suggested. Effects were demonstrated in individual animals that were previously only shown for grouped data and the techniques' sensitivity produced novel findings. Rats were ovariectomised at three ages and/or treated with oestrogen and slaughtered at four ages. The rat ovary inhibited growth pre-pubertally, and the response to ovariectomy or oestrogen was negatively related to the pre-treatment growth rate. Compensatory growth occurred following weaning in rats and following birth in ruminants. Estimated initial weights explained more of the variation in subsequent growth rates than did observed weights. In rats pre-weaning growth lines diverged (compensation being negligible), birth and weaning weights being positively correlated, post-weaning growth rate was strongly negatively correlated with weaning weight. Estimated birth and final weights, and weaning and final weights, were unrelated; compensation being nearly complete. Two sets of pre-weaning lamb live weights (collected by others) were, for individual animals, linearised. Pre-weaning compensation occurred, as it did in two independent sets of weighings from monozygotic twin heifers (also collected by others). Compensatory growth, between and within sets of twin, occurred rapidly to weaning, then slowed. The efficiency of identical twins for experimentation, using these methods, was shown, as were the disadvantages of using aver

The influence of sex on muscle, fat and bone growth from birth to maturity was investigated by complete dissection of a half carcass of 18 female and 21 male Jersey cattle. In addition, the cellular growth of five muscles: mm. rhomboideus, splenius, longissimus capitis, longissimus and semitendinosus, and of three fat depots: subcutaneous, intermuscular and perirenal, was examined. Transverse sections of the five muscles were stained for myosin adenosine triphosphatase (ATPase) activity. Muscle development, especially in the forequarter, is greater in males than in females. In males, the allometric growth of the neck muscles, mm. rhomboideus, splenius and longissimus capitis, relative to total muscle weight, was in two phases with two significantly different regression slopes, which describe the growth better than a single regression equation. The second phase had a significantly higher regression coefficient. In contrast, the growth of the neck muscles in females, and the growth of mm. longissimus and semitendinosus in both males and females, could be described satisfactorily by a single regression equation. The transverse sectional area of whole muscle and the mean fibre area, which was determined in fresh frozen sections, enabled the estimation of total fibre number in each of the five muscles. Fibre number did not change significantly during growth. Males had about double the number of fibres in these neck muscles as compared with females; functional differences between sexes were reflected in the difference in number and the rate of increase in size of myosin ATPase high fibres. These results support the concept that sexual dimorphism of overall muscle growth and muscle distribution in all species, is attributable to differences in prenatal development of fibre number, which determines the potential of a muscle to grow. Differences in fat growth between sexes were due to the overall rate of fat deposition; the order of partitioning was in general similar betwee

No abstract. The following is taken from the introduction: "Ttre health and productlon of the dalry cow 1s depend.ent Opo-n--h-E_eftfcffi -tunebi€nln g o f many 1 n temaL a ted phy si o1 o gl cal processes. For many years conslderable attention has been pald to digestlon, absorptlon of nutrlents, eirculatlon of the blood, utillsatlon of netabollc products, md excretion, It ls only in recent years, however, that the irnportance of the endocrlne system has been appreciated, and there still- renalns a large amount of fundanental researcb to be carried out before a eornplete understanding of the role of hornones wllL be obtalned.,"

Domestication of animals had only to begin before it became evident to man that some shelter from heat, cold and other environmental extremes was desirable for the animals as well as himself. Down through the ages end particularly in the present century refinement of methods, materials and degree of shelter have been added. There has not been a refinement corresponding in knowledge of the environmental influence in the range between obviously harmful extremes. Narrow margins for farm profit, increasing attention to production efficiency, increasing cost of shelter, war and post-war demands for high production, have exerted increasing pressure to correct this situation. The delay in attempting to get more accurate information on objectives in environmental control has been due to the immensity of the undertaking. Consider the range of environmental variables involved. The environment to be considered includes an almost.infinite variety of combinations of temperature, radiation, humidity, air control, air movement, light, sound space, surfaces, forms, pressure, presence of other animals. and time phases. The range of possible temperatures is vast. Man and animals. occupy a relatively narrow zone. True, they are exposed to the heat of the tropics and the cold of the arctic regions but animals really live, not in the air, but inside their own skins. The active cells of the body are all beneath the skin, the most important of them a long way below the surface. In the process of evolution mammals have arrived at a certain optimal temperature for the body cells and the organism strives to preserve this temperature as closely as possible. The problem is to define the limits of this zone, to describe the mechanism by which the optimal temperature is maintained, and to give an idea of the results when temperature control fails.