@conference {89234, title = {Development of ultrasound methodology to measure cow udder cistern storage capacity in the New Zealand pasture-fed context}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {73}, year = {2013}, month = {Jan}, pages = {114-116}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {

Studies have demonstrated that, for a given amount of secretory tissue, cows with a proportionally larger cistern produce more milk and are more resistant to the inhibitory effects on milk synthesis of longer milking intervals (Knight \& Dewhurst 1994; Stelwagen \& Knight 1997; Davis et al. 1998). This may be because they can store more milk before milk accumulation begins to inhibit further milk synthesis. Ayadi et al. (2003) demonstrated in a feedlot situation that cisternal volumes can be measured non-invasively using ultrasound technology. Dairy systems based on pasture, such as those in New Zealand, exhibit different challenges to the production of useful data using this technology compared to feed lot systems and the confounding effect of the variability in milking order and the subsequent variations of the intervals between subsequent milking (Molenaar et al. 2012).

}, issn = {1176-5283}, author = {Molenaar A and Leath SR and Caja G and Henderson HV and Cameron C and Challies M and Taukiri K and Chikazhe T and Kaumoana S and Lannou B and Dorleac A and Guy A and Gavin C and Singh K} } @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 {89268, title = {The effect of re-milking following extended non-milking periods on the proliferation and apoptosis of mammary gland epithelial cells in dairy cows}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {73}, year = {2013}, month = {Jan}, pages = {51-53}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {

In dairy cows, the increase in milk yield from parturition to peak lactation is attributed to an increase in the secretory activity of mammary epithelial cells (MECs) (Capuco et al. 2001). However, following peak lactation, there is a decline in milk production, which is attributed to the loss of MECs by programmed cell death or apoptosis (Capuco et al. 2001). The role of involution and the factors that regulate it in the bovine mammary gland are not well understood. Previous studies have characterised the process of involution in the bovine mammary gland by determining whether involution is reversible following an extended milk stasis. Involution was fully reversible following seven days of non-milking (Dalley \& Davis 2006), but was only partially reversible following longer non-milking intervals (Noble \& Hurley 1999; Singh et al. 2012).

}, issn = {1176-5283}, author = {Mallah GS and Dobson J and Moon S and Henderson HV and Molenaar A and Guan J and Singh K} } @conference {89267, title = {mTOR signalling in lactating bovine mammary gland}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {73}, year = {2013}, month = {Jan}, pages = {48-50}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {

The mammalian target of rapamycin (mTOR) is a protein kinase that has a well established role in the regulation of a range of cellular functions in response to hormones, growth factors and amino acids (Wang \& Proud 2011). The role of mTOR signalling in the regulation of milk protein synthesis in the mammary gland of ruminants is not well understood. Understanding this mechanism is an important step towards developing intervention strategies on farm, such as the supply of nutrients, to modulate milk protein output.

}, issn = {1176-5283}, author = {McCoard SA and Wards N and Singh K} } @conference {78990, title = {DNA methylation events in the {\'a}S1-casein-encoding gene associated with involution and re-initiation of lactation in dairy cows}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {72}, year = {2012}, month = {Jan}, pages = {73-75}, 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 Transcription5), which binds to conserved DNA sequence motifs in promoters of milk protein genes to stimulate their expression (Liu et al. 1997). Mammary gland involution induced by termination of milking is characterised by a rapid decrease in milk protein gene expression (Singh et al. 2008). Whereas milk production can be fully restored after seven days of ... continued}, issn = {1176-5283}, author = {Pryor S and Swanson K and Couldrey C and Henderson H 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 {78978, title = {Prenatal maternal effects on daughter milk production in New Zealand dairy cattle}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {72}, year = {2012}, month = {Jan}, pages = {19-22}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {

The impact of a cow{\textquoteright}s live weight and body condition score (BCS) during pregnancy on the milking performance of a resulting daughter was investigated using 4,021 Jersey and 9,329 Holstein Friesian dam-daughter pairs from the Livestock Improvement Corporation Sire Proving Scheme. Although the estimated maternal heritability of each trait in each breed was small (\< 0.02), a l kg increase in dam weight was associated with 1.19 ({\textpm} 0.25) and 0.43 ({\textpm} 0.15) litres increase in daughter milk volume, a 61 ({\textpm}11) and 15 ({\textpm}6) gram increase in fat and a 55 ({\textpm} 8) and 14 ({\textpm}5) gram increase in protein in Jersey and Holstein Friesian cows respectively. A one unit increase in BCS was associated with an increase in volume by 32 ({\textpm} 19) litres in Jerseys and a 14 ({\textpm} 14) litre decrease in Holstein Friesians. Fat increased by 1.91 ({\textpm} 0.84) kg and 0.56 ({\textpm} 0.55) kg and protein increased by 1.64 ({\textpm} 0.63) kg and 0.06 ({\textpm}0.42) kg per unit BCS in Jersey and Holstein Friesian respectively. All daughter responses are per lactation. Although small changes in the daughters milking traits were observed, the lack of significant variation in the maternal heritability indicates that the sample size of the dataset may not be sufficient to detect if prenatal maternal effects truly exist.

}, issn = {1176-5283}, author = {Gudex BW and Johnson DL and Singh K} } @conference {78987, title = {The relationship between milk synthesis and intracellular profiles of amino acids in the bovine mammary gland}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {72}, year = {2012}, month = {Jan}, pages = {63-66}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {

There is a growing body of evidence that amino acid (AA) signalling in the mammary gland may play a key role in milk production of ruminants through modulation of translational regulation (Moshel et al. 2006; Toerien \& Cant 2007). It has been postulated that the effect of nutrient signalling on elements of translational control of milk protein synthesis may contribute to the variable responses of milk protein yield observed following nutritional perturbations (Hanigan et al. 1998). Consistent with this hypothesis, we have reported that changes in the mean and variance of intracellular free AA (FAA) in the bovine mammary gland are associated with ... continued

}, issn = {1176-5283}, author = {McCoard SA and Pacheco D and Treloar BP and Wards N and Swanson K and Singh K} } @conference {79016, title = {The use of milking intervals of individual cows in assessing herd test milk production data}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {72}, year = {2012}, month = {Jan}, pages = {186-188}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {

Herd testing is a significant expense for dairy farmers but it gives important information about individual cow yields and contributes to the genetic worth status of the cows. While every effort is made to maximise the value of the tests to the farmer there are still opportunities to increase this value further. Estimations of milk yield from herd tests, whether from one or two milkings, rely on the generally held assumption that animals come in to the parlour in a similar order at each milking (DairyNZ 2011) and so the values obtained reflect a nominal 24 hour yield. ... continued

}, issn = {1176-5283}, author = {Molenaar AJ and Henderson HV and ML Burgess and Burgess WG and Johnson DL and Singh K} } @conference {75890, title = {BRIEF COMMUNICATION: Phenotypic selection of cows for lactation persistency}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {71}, year = {2011}, month = {Jan}, pages = {136-138}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Invercargill}, abstract = {Lactational persistency is the degree to which early lactation yield persists during the lactation season. Though this is a desired dairy performance trait, it has not been directly selected for in New Zealand dairy populations. In spring-calving pasture-fed cows, peak lactation is reached soon after calving and then declines by about 10\% per month (Davis et al., 2000) until the cows are... Continued}, issn = {1176-5283}, author = {Hickey SM and Singh K and Morris CA and Henderson HV and Molenaar AJ} } @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 {41781, title = {Expression of innate immune response genes in mammary epithelia following stimulation of lipopolysaccharide or Escherichia coli}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {68}, year = {2008}, month = {Jan}, pages = {31-32}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Brisbane, Australia}, abstract = {The innate immune system is essential for keeping the bovine mammary gland disease free. A number of innate immune response genes are expressed in bovine mammary epithelial cells (bMEC), suggesting it contributes to defence against pathogens (Rainard \& Riollet, 2006). These responses may play a key role in determining susceptibility to mastitis. The aim of this project was to investigate the expression in bMEC of specific innate immune genes in response to Escherichia coli ...Continued }, issn = {1176-5283}, author = {Stockum C and Haigh BJ and Meyer HHD and Bruckmaier RM and Wheeler TT and Singh 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 {41416, title = {Diurnal variation in blood plasma metabolites and insulin of lactating dairy cows grazing pasture and supplemented with a high-lipid supplement either once or twice a day}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {63}, year = {2003}, month = {Jan}, pages = {107-111}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Queenstown}, abstract = {The experiment determined the diurnal variation of a blood plasma hormone and three metabolites (insulin, glucose, NEFA and triglyceride) and how these varied with different frequencies of supplementary feeding. Twenty-four cows in early lactation (DIM 81 {\textpm} 20) were divided randomly into three treatments; grazed pasture only and pasture supplemented with 2 kg/cow/day of ruminally protected oilseed supplement (metabolisable energy 19 MJ/kg DM) either once a day after morning milking or twice a day after morning and afternoon milking. On day 12 of the experiment, 12 cows (4 cows/treatment) were jugular catheterised and commencing at 1600 h, blood sampled at 2-hourly intervals for 24 h. This protocol was repeated for the remaining 12 cows on day 13 Concentrations of the selected blood plasma hormone and metabolites varied diurnally (P<0.001). The difference between the average peak and nadir concentrations over the 24 hours were 54\%, 66\%, 224\% and 63\% for plasma insulin, glucose, NEFA and triglyceride respectively. Feeding the lipid supplement increased blood plasma NEFA (P<0.01), and triglycerides (P<0.001) but had no effect on insulin, or glucose concentrations. Frequency of supplementary feeding influenced (P<0.05) the diurnal variation of NEFA but not, insulin, glucose, or triglyceride. Concentrations of NEFA, glucose, and triglyceride were variable between 0600 h and 1000 h and stabilised between 1600 h to 2000 h. Plasma insulin concentrations were low and stable between 0400 h to 0800 h. Consideration of diurnal variation and the stability of the blood plasma components measured led to the recommendation that the best time to blood sample for insulin is between 0400 - 0800 h and for glucose, NEFA, and triglyceride, between 1600 2000h. }, issn = {1176-5283}, author = {Thomson NA and Singh K and Kay JK} } @conference {41225, title = {Dietary effects on gene expression of lipogenic enzymes in mammary gland of lactating mice}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {60}, year = {2000}, month = {Jan}, pages = {311-313}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {The effects of a fat-free or clofibrate-supplemented diet on gene expression of several lipogenic enzymes was investigated in mammary gland and liver of lactating mice. In lactating mammary gland, stearoyl CoA desaturase (SCD) mRNA expression was increased 2.1-fold (P<0.05) by feeding the fat-free diet, whereas clofibrate had no influence compared to control diet. Fatty acid synthase (FAS), acetyl CoA carboxylase (ACC), thioesterase II and lipoprotein lipase (LPL) mRNA levels in lactating mammary gland were unchanged after feeding the fat-free or clofibrate diets compared to control. In livers from lactating mice, the fat-free diet increased expression of SCD 5-fold (P<0.05) and FAS 10-fold (P<0.001) compared to control. ACC expression was unchanged by either the fat-free or clofibrate diet compared to control diet. These data show that, in lactating mammary tissue, expression of key lipogenic enzymes may be manipulated by diet, thus offering a potential means to modify milkfat composition. }, issn = {1176-5283}, author = {Singh K and Harley DG and Grigor MR and McFadden TB} } @conference {40814, title = {The calpain proteolytic system in different types of ovine skeletal muscles and relationship to meat tenderness}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {56}, year = {1996}, month = {Jan}, pages = {198-200}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {The calpain system is involved in postmortem tenderisation of meat. Muscle type also influences tenderness and aging rate. This study investigated the extent to which differences in the calpain system may account for differences in tenderness. Calpain and calpastatin activities were measured from 12 different ovine muscles. Shear force was determined on muscle aged at 15 C for 1, 2, 3 and 4 days postmortem and ultimate pH measured. Calpastatin, }, issn = {1176-5283}, author = {Singh K and Dobbie PM and Simmons NJ and Bass JJ and Thomson BC and Speck PA} } @conference {40813, title = {Differences in the post mortem kinetics of the calpain system in meat from bulls and steers}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {56}, year = {1996}, month = {Jan}, pages = {195-197}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {This experiment investigated differences in meat tenderness as defined by shear force between bulls and steers, and how these related to differences in the post mortem kinetics of the components of the calpain system. Strip loins (m. longissimus dorsi) from bulls with acceptable (pH < 5.7) ultimate pHs were compared with strip loins from prime steers. Samples were aged for 1, 3, 7, 13, 24, 48 and 72 hours at 15 C. The activities of calpastatin and (}, issn = {1176-5283}, author = {Thomson BC and Dobbie PM and Simmons NJ and Singh K and Speck PA} } @conference {40810, title = {Postmortem changes in pH and shear force in three commercial bull beef cuts}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {56}, year = {1996}, month = {Jan}, pages = {184-186}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {This experiment investigated the differences between fillet, strip loin and rump cuts obtained from carcasses of pasture-fed bulls. Four samples of each cut were collected on two different occasions and aged at 15 C for 2, 24, 48 ,72 and 120 hours. The pH of the fillet and rump cuts did not change post-slaughter. The pH of the strip loin was higher at slaughter but declined over time and by 48 hrs post-slaughter there were no differences in the pH value of the three cuts. Shear force was determined using a MIRINZ tenderometer. The fillet had the lowest shear force and the rump cut had the highest. There were no differences in the activities of the components of the calpain system at 2 hours post-slaughter. These results suggest that the differences in meat quality and particularly ultimate tenderness, between the three cuts were not due to differences in the activities of the components of the calpain system or pH }, issn = {1176-5283}, author = {Thomson BC and Dobbie PM and Singh K and Speck PA} }