@conference {89266, title = {The effect of milking frequency in early lactation on gene expression in the bovine mammary gland}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {73}, year = {2013}, month = {Jan}, pages = {45-47}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {

In ruminants, altered milking frequency influences milk production due to either an increase in the number of secretory mammary epithelial cells and/or the activity of these cells (Stelwagen 2001). Microarray studies examining the response of mammary epithelial cells to either increased (Connor et al. 2008) or decreased (Littlejohn et al. 2010) milking frequency, reportedaltered gene expression in several regulatory pathways. These changes would appear to be locally regulated within the mammary gland, as milk production is different in different glands within the same udder depending on the milking frequency of individual glands (Stelwagen 2001). Therefore, the udder lends itself well as a model system to study the effect of different milking frequencies by comparing the response in adjacent udder halves (Murney et al. 2012).

}, issn = {1176-5283}, author = {MacLean PH and Stelwagen K and Maqbool N and Oden K and Murney R and Couldrey C and Singh K} } @conference {78988, title = {The effect of milking frequency in early lactation on milk yield and milk protein gene expression in the bovine mammary gland}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {72}, year = {2012}, month = {Jan}, pages = {67-69}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {

In dairy cows, increased milking frequency (MF) has a positive effect on daily milk yield (MY), providing dietary energy intake is sufficient to maintain the increase in production (Phillips et al. 1980). Short-term increases in MF during early lactation may have both an acute effect and a carry-over effect on MY once the animals have returned to less frequent milking (Hale et al. 2003). The critical period for increased MF to generate a carry-over effect on MY is within the first three weeks of lactation and may only need to be applied for as little as 14 days ... continued

}, issn = {1176-5283}, author = {Murney R and Stelwagen K and Singh K} } @conference {78989, title = {The effect of re-milking following extended non-milking periods on lactation in dairy cows}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {72}, year = {2012}, month = {Jan}, pages = {70-72}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {In dairy cows, the cessation of milk removal for extended periods, such as drying-off, initiates the process of mammary gland involution. This results in a decline of mammary secretion and changes in secretion composition. Morphological changes in the mammary gland occur within the first week of non-milking, with extensive re-modelling by the third or fourth week. However, many alveolar structures are retained (Hurley 1989). Thus, involution may be reversible following extended non-milking periods (Noble \& Hurley 1999). Milk yield is fully restored ... continued}, issn = {1176-5283}, author = {Singh K and Swanson K and Henderson HV and Stelwagen K} } @conference {79029, title = {Host-defence related bioactive proteins in cows{\textquoteright} milk during mastitis and after drying-off}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {72}, year = {2012}, month = {Jan}, pages = {240-242}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {Besides the caseins and major whey proteins, cows{\textquoteright} milk contains a wide range of less abundant proteins that have functions associated with host defence, and are thought to play a role in protection against microbial infections (Stelwagen et al. 2009; Wheeler et al. 2007). Microarray analysis has shown that complex changes in gene expression occur in the bovine mammary gland in response to drying-off, including up-regulation of host-defence associated genes (Singh et al. 2008). The abundance of at least some proteins encoded by these genes can be altered in response to milking frequency and at different stages of the lactation cycle.}, issn = {1176-5283}, author = {Backmann EC and Hine BC and Broadhurst and Kim K and Smolenski GA and Stelwagen K and Wheeler TT} } @conference {69513, title = {Cathelicidin levels in milk from cows infected with a range of mastitis causing pathogens}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {70}, year = {2010}, month = {Jun}, pages = {243-245}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Palmerston North}, abstract = {Mastitis is an inflammatory condition of the udder that is highly prevalent in cows on New Zealand dairy farms. It results in reduced production, increased treatment costs and lower profitability (Petrovski et al.,2006). An elevated somatic cell count (SCC) in the milk, mainly due to recruitment of immune cells to the site of infection, is the most widely accepted standard for diagnosis of subclinical infection whereas bacteriological culturing is typically used for identification of the causative pathogen from clinical cases (Moyes et al.,2009; Schukken et al.,2003). At present, both tests require laboratory analysis and are not routinely performed on individual cows throughout lactation.}, issn = {1176-5283}, author = {Pryor SM and Smolenski GA and Wieleczko RJ and Broadhurst and Stelwagen K and Wheeler TT and Haigh BJ} } @conference {60942, title = {DNA methylation events associated with the suppression of milk protein gene expression during involution of the bovine mammary gland : Brief Communication}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {69}, year = {2009}, month = {Jun}, pages = {57-59}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {During lactation, prolactin activates STAT5 (Signal Transducer and Activator of Transcription), which binds to conserved DNA sequence motifs in promoters of milk protein genes to stimulate their expression (Liu et al., 1997). At drying-off, mammary involution is characterised by a rapid decrease in milk protein gene expression (Goodman \& Schanbacher, 1991), including ?S1-casein (Singh et al., 2008). The ?S1-casein promoter features... Continued }, issn = {1176-5283}, author = {Singh K and Swanson K and Couldrey C and Seyfert H-M and Stelwagen K} } @conference {60944, title = {Understanding the interaction of prolactin and leukaemia inhibitory factor signalling during the switch from lactation to involution : Brief Communication}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {69}, year = {2009}, month = {Jun}, pages = {65-67}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {The molecular mechanisms involved in involution of the bovine udder, a process which underpins lactation persistency, are poorly understood. During rodent lactation, STAT5 is activated in response to prolactin (PRL) to stimulate milk protein production (Liu et al., 1997). At the onset of involution, STAT5 is rapidly inactivated (Schmitt-Ney et al., 1992), and STAT3 is activated by leukaemia inhibitory factor (LIF) to... Continued}, issn = {1176-5283}, author = {Singh K and Vetharaniam I and Prewitz M and Dobson J and Stelwagen K} } @conference {41765, title = {Induced physical distension of rat mammary glands accelerates the onset of apoptosis and involution compared with milk accumulation alone : Brief Communication}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {67}, year = {2007}, month = {Jan}, pages = {403-406}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Wanaka}, abstract = {Extended periods of milk accumulation result in reduced milk secretion, increased apoptosis and eventually, involution of mammary glands. The subsequent change in epithelial cell shape from a cuboidal to a flattened morphology as the alveoli distend with milk may initiate changes in protein and gene expression (mechanotransduction) triggering the process of involution (Davis et al., 1999).}, issn = {1176-5283}, author = {Phyn CVC and Dobson JM and Davis SR and Stelwagen K and Singh K} } @conference {41459, title = {Decreased gene expression of integrins in epithelial cells during mammary engorgement}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {64}, year = {2004}, month = {Jan}, pages = {11-13}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {In ruminants, the molecular mechanisms regulating mammary involution and apoptosis (programmed cell death) are not well characterised, but extensive research in rodents has established that many cell types, including mammary epithelial cells, require anchorage to the extracellular matrix for survival. This anchorage is mediated via the integrins, a family of transmembrane glycoproteins that bridge intra- and extracellular compartments enabling direct communication between adaptor molecules in the cytoplasm and specific receptor motifs on the ECM proteins (Clark \& Brugge, 1995; Giancotti \& Ruoslahti, 1999; Hynes, 1992). Integrins form heterodimers between α and β subunits to produce more than 20 different receptors, and many subtypes have been identified in mammary glands (Clark \& Brugge, 1995). We have shown previously that one such integrin, β1, is reduced rapidly as a result of induced weaning in rodents, and these changes are followed by apoptosis (McMahon et al., 2004). The aim of this study was to investigate the molecular mechanisms that may regulate mammary involution in the bovine by examining cell-matrix interactions that may be involved in survival of mammary epithelial cells, ultimately to improve lactational persistency and tolerance of extended milking intervals ... }, issn = {1176-5283}, author = {Singh K and Dobson J and Stelwagen K and Prosser CG and Farr VC and Molenaar A and Davis SR} } @conference {41469, title = {Expression of the tight junction protein zonula occludens-1 during mammary engorgement}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {64}, year = {2004}, month = {Jan}, pages = {43-47}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {An increase in tight junction (TJ) permeability occurs during extended milking intervals and is associated with reduced milk secretion. This paper examines temporal changes in the expression of a major TJ protein, zonula occludens-1 (ZO-1), during mammary engorgement. Alveolar mammary tissue was collected from 52 mid-lactation dairy heifers at 0, 6, 12, 18, 24, 36 and 72 h, and at 8 d following abrupt cessation of milking (n >= 6 cows per time point). ZO-1 protein expression significantly decreased during mammary engorgement (P<0.05). Similarly, ZO-1 mRNA expression had halved by 36 h to 8 d post-milking (P<0.05). In a second trial, alveolar tissue was collected from the udder halves of late-lactation dairy cows (n = 4) that were milked unilaterally, either once-daily or twice-daily for 4 days. A 1.7-fold increase in ZO-1 mRNA expression was detected after once-daily milking, compared with twice-daily milking (P<0.05). The down-regulation of ZO-1 during mammary engorgement is consistent with increased TJ permeability. However, the up-regulation of ZO-1 mRNA expression during short-term once-daily milking suggests that TJ function is repaired as the mammary gland adjusts to the extended milking interval. In conclusion, we have identified changes in ZO-1 critical to TJ function in bovine mammary glands. }, issn = {1176-5283}, author = {Cooper CV and Stelwagen K and Singh K and Farr VC and Prosser CG and Davis SR} } @conference {41457, title = {Northern analysis of temporal and spatial variation in milk protein expression during early mammary involution in dairy cows}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {64}, year = {2004}, month = {Jan}, pages = {5-7}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {Understanding the mammary responses that occur at the cessation of milking whether natural, forced, or which occur at the end of the milking season and during the subsequent initiation of mammary involution (Holst et al., 1987; Hurley, 1989) has relevance in milk production traits such as milk yield, persistency and extended milking intervals and may suggest ways of improving milk production in later lactation (Stelwagen, 2001) (Vetharaniam et al., 2003). The proportions of secretory, support and milk storage components vary significantly between the alveolar (main milk synthesis), peripheral (a several cm thick layer of secretory tissue surrounding the main alveolar bed) and cisternal (main milk storage area adjoining the teats) compartments of the udder (Farr et al., 1996; Sordillo and Nickerson, 1988; Weber, 1977). In addition, variations in the local proportions of these components has also been observed in the main alveolar areas and dramatic variations of gene expression depending on the local mammary tissue composition have been observed (Molenaar et al., 1992). Ignorance of the effect on gene expression profiles resulting from sampling variations could lead to improper interpretation of experimental results and hence there is a need for more extensive spatial and temporal surveys to be done. }, issn = {1176-5283}, author = {Molenaar AJ and Farr VC and Oden KE and Wheeler TT and McMahon CD and Good LL and Stelwagen K and Singh K and Davis SR} } @conference {41458, title = {The use of cDNA microarrays to investigate changes in gene expression in the involuting bovine mammary gland}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {64}, year = {2004}, month = {Jan}, pages = {8-10}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {The molecular mechanisms and pathways involved in involution of the udder and which coordinate and regulate the processes of cell death and proliferation after weaning/cessation of milking in ruminants, are poorly understood. The aim of this study was to use cDNA microarray analysis to identify genes and pathways involved in involution of the bovine mammary gland. Ultimately, because this process underpins lactation traits such as persistency and mammary responses to milking frequency (Stelwagen, 2001; Vetharaniam et al., 2003), this information may allow the development of novel strategies for improving milk production especially in the later stages of lactation. Involution of the bovine mammary gland was induced by abrupt termination of milking in 48 non-pregnant Friesian dairy cows at mid-lactation (average days in milk, 92 {\textpm} 3) {\textellipsis} }, issn = {1176-5283}, author = {Singh K and Molenaar AJ and Stelwagen K and Farr VC and Good L and Swanson K and Oden K and Wheeler T and McMahon C and Henderson H and Wilson T and Hyndman D and Baird D and McCulloch A and Davis SR} } @conference {41460, title = {The use of microarrays to investigate gene regulation in the bovine mammary gland during Streptococcus uberis mastitis}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {64}, year = {2004}, month = {Jan}, pages = {14-16}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {Bovine mastitis is one of the most costly dairy-based diseases worldwide with an estimated $60 M loss to New Zealand per season. Mastitis infections are a result of bacterial or fungal pathogens becoming established in the udder, and are detected by the increase of somatic cells in the mammary gland, bacteriology data and physical signs of infection. In New Zealand, mastitis is usually a result of a gram-positive bacterial infection (Brookbanks, 1966). Of these bacteria, Streptococcus uberis is emerging as one of the most prevalent causative organism of mastitis in New Zealand (McDougall, 2002). It resides naturally in the environment making prevention of the disease difficult. Currently the main means of controlling the disease is through administering antibiotics following identification of infection. The mammary gland is protected from invasion by the activation of non-specific (innate) and specific defence mechanisms. The innate immune response is the predominant defence during the early stages of infection and is induced rapidly at the site of infection (Sordillo et al., 1997). Although the local mammary innate immune response has been widely investigated, studies have focussed on known antibacterial compounds and little is known about the novel compounds in bovine milk and how these contribute to the defence system of the mammary gland. The mechanism by which the mammary gland innate immune system is active against S. uberis is poorly understood. By developing an understanding into the way S. uberis induces an immune response in the mammary gland and the effect of infection on mammary gland metabolism we may identify components which can be utilised to either reduce the symptoms of/or prevent or cure S. uberis mastitis. }, issn = {1176-5283}, author = {Swanson KM and Henderson HV and Farr VC and Davis SR and Oden K and Stelwagen K and Molenaar A and Singh K and Prosser CG} } @conference {40980, title = {Once-Daily Milking of Dairy Cows : An Appraisal}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {58}, year = {1998}, month = {Jan}, pages = {36-40}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Once-daily milking offers the opportunity for a quantum change in the operation of the dairy farm. In particular, once-daily milking provides the major opportunity to reduce costs and increase labour productivity. New Zealand cows (particularly Jerseys) already possess an advantage in favour of once daily milking - that they produce a relatively concentrated milk and therefore have the capacity to accumulate >24 hours-worth of milk production. Nevertheless, short-term trials indicate an average production loss of 21\% for once-daily relative to twice-daily milking. Full-lactation trials suggest greater losses of 35-50\%, although the productivity of commercial farms milking once-daily throughout lactation is consistent with much smaller losses. There is evidence that cows can adapt to longer milking intervals and this coupled with increased herd size and care to maximise milk removal may restrict yield losses on the farm to less than 10\%. Apart from the production loss, other negative consequences of once-daily milking include changes in milk composition, a reduction in milk processing quality and increased somatic cell count. Further, it is not known to what degree, if any, cow comfort is compromised by once-daily milking. If it becomes possible to identify more tolerant breeds or individuals, it may be feasible to reduce milk yield losses still further and ameliorate the changes in milk composition. }, issn = {1176-5283}, author = {Davis SR and Farr VC and Stelwagen K} } @conference {40983, title = {Rates of recovery of milk yield and composition following milking intervals of varying length}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {58}, year = {1998}, month = {Jan}, pages = {47-48}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {In order to examine the rate of recovery of milk yield and composition following an extended milking interval, 20 cows were milked out with the aid of oxytocin and subjected to single intervals of either 16, 24, 32 or 40h. Cows were then milked frequently with the aid of oxytocin during the subsequent 26h. Milk secretion rate was depressed to 67 and 56\% of pre-treatment (twice-daily milking) rates by the 32 and 40h treatments, and rates of recovery were slow, extending beyond 26h post-treatment. Milk fat and protein contents did not differ significantly among treatment groups while lactose content was reduced by the 32 and 40h intervals, recovering by 26h post-treatment. It was concluded that the udder is particularly sensitive to milk accumulation beyond 24h and that this leads to impairment of the {\textquoteleft}synthetic machinery{\textquoteright} in the udder. The prolonged effect on milk lactose concentrations with the longer intervals suggests that there was a sustained change in the integrity of tight junctions between secretory cells, leading to increased permeability of the mammary gland. Rates of recovery of yield and composition were relatively slow, taking >24h in spite of enhanced rates of milk removal. }, issn = {1176-5283}, author = {Farr VC and Stelwagen K and Davis SR} } @conference {40935, title = {Removal of cisternal milk following milk accumulation for 9 hours does not increase total yield during once-daily milking}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {57}, year = {1997}, month = {Jan}, pages = {217}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Once-daily milking (ODM) of dairy cows in New Zealand results in a yield loss of 15-25\% (Carruthers V.R. et al.,(1993)). This loss is not associated with the total storage capacity of the udder, although some studies have shown that increase in the volume of milk in the cistern is associated with reduced yield loss during ODM (Knight C.H. and Dewhurst R.J. (1994)). The following experi-ment was undertaken to determine whether removal of cisternal, but not alveolar milk, at the p.m. milking, de-creased the production loss during ODM.}, issn = {1176-5283}, author = {Farr VC and Davis SR and Stelwagen K} } @conference {40780, title = {Effect of Streptococcus uberis infection on milk characteristics of individual quarters}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {56}, year = {1996}, month = {Jan}, pages = {65-67}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Composite 24 h milk samples were collected for detailed milk analysis from each quarter of ten cows known to be free of intramammary infection. Milk yield and concentration of lactose and serum albumin (BSA) were significantly higher (P<0.001), and chloride ions significantly lower (P<0.001), in hind compared with fore quarters. Four cows developed clinical intramammary infection when subsequently challenged in the left hind quarter with Streptococcus uberis. For all parameters measured, i.e. protein, lactose, somatic cell count (SCC), BSA and immunoglobulins (IgG), milk from the infected quarter differed significantly from the uninfected quarters. No effect of infection was observed in quarters adjacent to the infected quarter, except for SCC, which increased significantly (P<0.001) in the uninfected hind quarter. Milk proteolytic activity in the infected quarter increased significantly (P<0.001) due to increased conversion of plasmin to plasminogen.}, issn = {1176-5283}, author = {Lacy-Hulbert SJ and Woolford MW and Nicholas G and Stelwagen K} } @conference {40793, title = {Influence of level of feeding and stage of lactation on proteolytic activity in bovine milk}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {56}, year = {1996}, month = {Jan}, pages = {114-117}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Using a Latin square cross-over design, twelve sets of identical Friesian or Friesian x Jersey twin cows during spring (early lactation: 42 }, issn = {1176-5283}, author = {Nicholas GD and Prosser CG and Stelwagen K and Mackle TR} } @conference {40652, title = {Effect of once daily milking (ODM) on enzyme activities in the bovine mammary gland}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {55}, year = {1995}, month = {Jan}, pages = {12-13}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Maintenance diets containing two levels of energy (9.6 v. 11.5 MJME per kg DM) and two levels of protein (10.7 v.21.7 g nitrogen per kg DM) were fed to four groups, each of ten Romney (five low and five high staple tenacity) and four Drysdale yearling rams, for six weeks from mid March. Protein supplementation increased protein intake by 114\% (P<0.001). It increased clean wool growth in the treatment period (6.2 v. 10.2 g.um- 2.d-1, P<0.001), more so in Drysdales than Romneys (89 v. 46\%; P<0.001). It also increased mean fibre diameter (38.1 v. 34.3 um, P<0.001) without changing the proportion of fibre that was medullated. Responses to the nutrient supplements were similar in low and high staple tenacity Romney rams. It is concluded that during the photoperiod-induced decline in wool growth in autumn, sheep on a maintenance diet responded to the increase in dietary protein with an increase in the volume of fibre and volume of keratin produced with no net change in the proportion of fibre medullated. }, issn = {1176-5283}, author = {Farr VC and Stelwagen K and Kerr MA and Davis SR and Eichler SJ} } @conference {40650, title = {Effect of once-daily milking and bovine somatropin administration in Friesian cows on milk protease activity}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {55}, year = {1995}, month = {Jan}, pages = {7-8}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Samples of wool from Perendale hoggets born at Whatawhata Research Centre in 1989 from ewes selected for and against loose wool bulk were tested for propensity to yellow. After storage in a laboratory for two years, wool from the high bulk line was significantly more yellow than wool from low bulk line. When the greasy wool was incubated at 40 degrees and 100\% relative humidity, differences in all three tristimulus values between high and low bulk wool were significant. Tristimulus Y and Z decreased and Y minus Z increased when clean wool samples were subjected to more extreme challenges similar to those which may occur during processing. These changes did not affect the differences in colour between the selection lines. These results suggest that management changes may be required to restrict yellowing of high bulk wool during growth and storage. Simultaneous selection for reduced propensity to yellow and increased bulk may reduce the genetic progress attainable in either characteristic. }, issn = {1176-5283}, author = {Stelwagen K and Whyte JH and Zavizon B and Prosser CG and Davis SR and Farr VC and Politis I} } @conference {40651, title = {Influence of milking frequency and feeding level on plasmin activity and casein degradation in milk}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {55}, year = {1995}, month = {Jan}, pages = {9-11}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Wool samples from 28 Merino wethers, 31 Corriedale ewes, 37 Perendale ewes and 30 Coopworth ewes were examined for propensity to develop yellow discolouration in relation to the mean fibre diameter and its variability. The propensity of wool to develop yellow discolourations was estimated by two techniques, namely, an incubation technique which measures the colour developed in the wool fibre during an incubation in the laboratory, and the predictive technique described by Aitken et al., 1994. Correlations between propensity to yellow (Y-Z) and mean fibre diameter were low in the Corriedale, Perendale and Coopworth samples, but high in the Merinos. Correlations between propensity to yellow and standard deviation of fibre diameter were also low in the Corriedales, Perendales and Coopworths, but moderate in the Merinos. The correlations between Y and Z and the fibre diameter statistics following similar trends to those for Y-Z. All correlations between propensity to yellow and coefficient of variation of fibre diameter were low. Thus while the propensity to discolour during growth is positively related to fibre diameter in fine wool, no such relationship exists in medium and coarser wool. This provides a further reason for Merino breeders to produce a fine fleece type. }, issn = {1176-5283}, author = {Prosser CG and Nicholas G and Stelwagen K and Lacy-Hulbert SJ and Woolford MW and McFadden TB} } @conference {40574, title = {Effect of once daily milking and concurrent somatotropin (bST) on production and mammary tight junction permeability in cows - Brief Communication}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {54}, year = {1994}, month = {Jan}, pages = {101-102}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {No abstract supplied }, issn = {1176-5283}, author = {Stelwagen K and Davis SR and Farr VC} } @conference {40478, title = {The effect of an extended milking interval on mammary blood flow and tight junctions between mammary cells in goats}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {53}, year = {1993}, month = {Jan}, pages = {159-162}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Hereford x Friesian cows were used to compare the calf and cow performance of 66 single-calved cows (Single Cows) rearing only their own calf (Single Calf) and 45 contemporary single-calved cows (Foster Cows) rearing their own calf (Own Calf) plus a foster calf (Foster Calf). Fostering was succesful in 85\% and 95\% of attempts in 1990 and 1991, respectively. Mean weaning weight was lowest in the Foster Calf group but comparable in the Own Claf and Single Calf groups (140 vs 194 vs 202 kg, P