@article {3672,
	title = {Implications of using an extended lactation to change from a spring-calving to an autumncalving farm system in South Taranaki},
	journal = {New Zealand Journal of Animal Science and Production},
	volume = {80},
	year = {2020},
	month = {09/2020},
	pages = {143-149},
	address = {Online},
	abstract = {Recent changes to pasture-supply curves in South Taranaki, and the availability of winter milk premiums have increased farmer
interest in changing from a spring-calving to an autumn-calving farm system. One approach to changing the season of calving
from spring to autumn is to extend the calving interval (CI) by delaying the mating period by ~8 months, so that they next calve
in autumn and undertake an extended lactation [>305 days in milk (DIM)]. A large-scale farmlet experiment was established in
South Taranaki to investigate the production and reproduction responses of cows using this approach. In June 2017, 602 springcalving
cows were allocated to two farmlets. In one farmlet (SPR) 301 cows were mated in October to maintain a 12-month CI
spring-calving pattern. In the other farmlet (AUT, n=301 cows), mating was delayed for eight months, and cows underwent an
extended lactation (mean DIM, 488; max DIM, 577) to calve next in autumn 2019. The experiment analysed two lactations for the
AUT farmlet and two and a half lactations for the SPR farmlet. Across the total experimental period, milksolids (MS) production
was similar between farmlets (1,194 vs. 1,174 kg MS/cow), however, cows in the AUT farmlet were fed more supplementary feed
[2,371 vs. 1,951 kg dry matter (DM)/cow]. The extended lactation changed the relationship between feed supply and herd demand,
which led to excessive BCS gain and ryegrass staggers for AUT farmlet cows. Further research is required to examine grazing
management during extended lactations and to assess the economic implications of this approach.

Keywords: autumn calving; spring calving; extended lactation},
	issn = {1176-5283},
	author = {Jarman JWM and Kay JK and Neal M and Donaghy DJ and Tozer P}
}
@conference {89260,
	title = {Modelling the effect of temporary once-a-day milking durinmg early lactation on dairy farm production and profitability},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {73},
	year = {2013},
	month = {Jan},
	pages = {21-25},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Hamilton},
	abstract = {<p>The DairyNZ Whole Farm Model was used to predict the effect of temporary once-a-day (OAD) milking during the calving period on milksolids (MS) production, farm profitability and herd body condition score (BCS) at dry-off. Farms from three regions and three independent seasons were modelled for: wholeseason twice-a-day (TAD) milking of all cows (Control), OAD milking of all cows for eight days immediately post-calving and TAD milking thereafter (Col OAD), OAD milking of the herd for three weeks from the planned start of calving (PSC) and TAD milking thereafter (3 wk OAD), and OAD milking of the herd for six weeks from the PSC and TAD thereafter (6 wk OAD). Model outputs indicated MS production (kg/ha) losses of 2, 1.2 and 3.7\% and profit ($/ha) losses of 6.5, 4.5 and 11.6\% for the Col OAD, 3 wk OAD and 6 wk OAD regimes, respectively. Slight improvements in dry-off BCS were predicted for the OAD milking regimes, comparedwith the control. Milking the herd OAD for three weeks from the PSC may be the prefered strategy to offer labour, lifestyle and animal health benefits with the smallest losses of MS production and farm profit.</p>
},
	issn = {1176-5283},
	author = {Khaembah EN and Rius AG and Beukes PC and Levy G and Gregorini P and Roche JR and Kay JK and Phyn CVC}
}
@conference {78998,
	title = {Maintenance energy requirements of non-lactating, pregnant dairy cows},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {72},
	year = {2012},
	month = {Jan},
	pages = {117-119},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {A number of estimates of metabolisable (ME) and net energy (NE) requirements for maintenance, activity, reproduction and productive purposes have been published (AFRC 1995; ARC 1980; CSIRO 2007; NRC 2001). The most appropriate recommendations for New Zealand systems have been compiled by Nicol \& Brookes (2007).},
	issn = {1176-5283},
	author = {Mandok KS and Greenwood SL and Kay JK and Crookenden M and Roche JR}
}
@conference {79001,
	title = {Once-daily milking during a feed deficit improves energy status in early lactating dairy cows},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {72},
	year = {2012},
	month = {Jan},
	pages = {129-133},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {The aim of this study was to determine the effect of once-daily (1X) milking during a feed deficit on energy status of grazing dairy cows. Multiparous cows (n = 120), grazing to residuals of 1,600 kg DM/ha, and milked twice-daily (2X) from calving until approximately 35 days-in-milk, were allocated to one of four treatments in a 2 x 2 factorial arrangement. Cows were adequately fed (14 kg DM/cow/d) or underfed (8 kg DM/cow/d) and milked 2X or 1X for three weeks, after which all cows were milked 2X and grazed to residuals of 1,600 kg DM/ha for 20 weeks. During the three-week treatment period, plasma concentrations of glucose, insulin and insulin-like growth factor-I (IGF-I) were less in underfed compared with adequately cows, while non-esterified fatty acids (NEFA), β-hydroxybutyrate (BHBA) and liver enzymes were greater. An interaction existed and the increase in liver enzymes with underfeeding only occurred in cows milked 1X. Cows milked 1X had greater plasma glucose, insulin and IGF-I and less NEFA and BHBA than those milked 2X. Data indicate that milking cows 1X during an acute feed deficit improves energy status.},
	issn = {1176-5283},
	author = {Kay JK and Phyn CVC and Rius AG and Morgan SR and Grala TM and Roche JR}
}
@conference {75869,
	title = {BRIEF COMMUNICATION: Effect of milking frequency and concentrate supplementation on milk production during an extended lactation in grazing dairy cows},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {71},
	year = {2011},
	month = {Jan},
	pages = {42-44},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Invercargill},
	abstract = {Extending the lactation for longer than 300 days can be used to maintain a high level of milk production, improve reproductive function, and animal welfare. Extended lactations of ~600 days in milk (DIM) in pasture-based systems could benefit the dairy industry by maintaining a relatively constant milk supply throughout the season, improving labour conditions, and reducing on-farm costs (Kolver et al., 2007). Milk production during an extended lactation is dependent... Continued},
	issn = {1176-5283},
	author = {Rius AG and Phyn CVC and Kay JK and Morgan SR and Grala TM and Roche JR}
}
@conference {75868,
	title = {Effect of milking frequency and nutrition in early lactation on milk production and body condition in grazing dairy cows},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {71},
	year = {2011},
	month = {Jan},
	pages = {37-41},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Invercargill},
	abstract = {Multiparous Holstein-Friesian cows (n = 120), grazing pasture and milked twice-daily (2X) from calving until ~35 days in milk, were allocated to one of four treatments. Treatments consisted of 2X or once-daily milking (1X), and UnRes (15 kg dry matter (DM)/cow/day) or Res (9 kg DM/cow/day) pasture intake for three weeks. Following treatment, all animals were milked 2X and offered pasture (residuals of 1,600kg DM/hectare) for 20 weeks. During the treatment period (Weeks 1-3), yields of milk, fat, protein and lactose decreased with reduced milking frequency and feeding level. Interactions existed for milk, protein and lactose yields and the decrease due to 1X milking was greater in the UnRes than Res cows. During the post-treatment periods (Weeks 4-12 and Weeks 13-23) no interactions were present. Restricted cows produced less milk, fat, protein and lactose compared with UnRes cows during Weeks 4-12, but no difference existed during Weeks 13-23. During Weeks 4-12, cows milked 1X produced less milk, fat, protein and lactose than those milked 2X and these differences remained during Weeks 13-23. During the treatment period, body condition score was less in Res than UnRes cows, however there was no effect of milking frequency on body condition score. Neither feeding level nor milking frequency altered post-partum anoestrus interval.},
	issn = {1176-5283},
	author = {Kay JK and Phyn CVC and Rius AG and Morgan SR and Grala TM and Roche JR}
}
@conference {75870,
	title = {Effect of temporary alterations to milking frequency during the early post-partum period on milk production and body condition score in grazing dairy cows},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {71},
	year = {2011},
	month = {Jan},
	pages = {45-49},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Invercargill},
	abstract = {This study investigated the immediate and long-term effects of temporary alterations to milking frequency post-partum in grazing cows. Multiparous Holstein-Friesian cows (n = 150) were assigned to one of five groups at calving: milked twice daily (2X, Control), or either once daily (1X) or thrice daily (3X) for three or six weeks, and 2X thereafter. During Weeks 1-6 post-calving, 1X for six weeks resulted in greater decreases in milk, fat, protein and lactose yields (P <0.05) relative to 2X than 1X for three weeks. Furthermore, 1X for three or six weeks reduced fat, protein and lactose yields (P <0.05), and tended to reduce milk yields (P = 0.08), for the remainder of lactation (Weeks 8-32). Body condition was greater for 1X cows at Weeks 6 and 8 (P <0.05) and tended to be greater during Weeks 8-32 (P = 0.09). Milking 3X for three or six weeks increased milk yield (P <0.05) relative to 2X during Weeks 1-6 and milk yields were numerically greater during Weeks 8-32 (P = 0.17); however, fat and protein yields were not affected. Once-daily milking for three or six weeks postcalving had lactation-long negative effects on milk production, whereas 3X increased milk yield but did not result in short- or long-term benefits in fat and protein yields.},
	issn = {1176-5283},
	author = {Phyn CVC and Kay JK and Rius AG and Morgan SR and Roach CS and Grala TM and Roche JR}
}
@conference {75861,
	title = {Temporary alterations to milking frequency, immediately post-calving, modified the expression of genes regulating milk synthesis and apoptosis in the bovine mammary gland},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {71},
	year = {2011},
	month = {Jan},
	pages = {3-8},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Invercargill},
	abstract = {Temporary changes to milking frequency during early lactation can elicit lactation-long changes in milk production. This study tested whether altered milking frequency, immediately post-calving, would affect mammary gene expression during and/or following treatment. Multiparous, grazing dairy cows (n = 150) were allocated to one of five treatments post-calving: milking thrice-daily (3X) for three or six weeks, and twice-daily (2X) thereafter; milking once-daily (1X) for three or six weeks, and 2X thereafter; or milking 2X for the entire lactation. Mammary tissue was biopsied from 12 cows per treatment at three, six and nine weeks postcalving and expression of milk synthesis and apoptosis genes measured using quantitative PCR. The milk fat, lactose and protein genes were down-regulated (P <0.05) in cows milked 1X compared with cows milked 2X. At nine weeks post-calving, cows milked 1X for three weeks had reduced mRNA levels of milk synthesis genes compared with cows milked 1X for six weeks (P <0.05). The expression of apoptosis genes was up-regulated (P <0.05) in cows milked 1X relative to 2X, during and post-treatment. There were no gene expression changes during 3X milking compared with cows milked 2X. Changes in gene expression observed in cows temporarily milked 1X reflect physiological changes consistent with longer-term reductions in milksolids yield.},
	issn = {1176-5283},
	author = {Grala TM and Phyn CVC and Kay JK and Rius AG and Littlejohn MD and Snell RG and Roche JR}
}
@conference {60938,
	title = {The effect of concentrate supplementation on milk production during an extended lactation in grazing dairy cows : Brief Communication},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {69},
	year = {2009},
	month = {Jun},
	pages = {43-45},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {Extended lactation systems where cows are milked for longer than 300 days, provide an opportunity for farmers to use the lactation potential of genetically superior cows, reduce calving and mating costs, even-out labour requirements, and/or build herd size by retaining non-pregnant cows. However, depending upon cow genetic strain and nutrition, milk production can be reduced in an extended lactation system relative to a {\textquoteright}normal{\textquoteright} lactation of 260 to 300 days (Kolver et al., 2007; Grainger et al., 2009). Winter-feeding levels are potentially important... Continued},
	issn = {1176-5283},
	author = {Phyn CVC and Kay JK and Roach CG and Kolver ES}
}
@conference {60934,
	title = {The effect of feed restriction during peak lactation on milk production parameters : Brief Communication},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {69},
	year = {2009},
	month = {Jun},
	pages = {24-26},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {Adverse weather conditions that reduce pasture growth and/or quality can place the lactating dairy cow under periods of transitory nutritional stress. Previous research that has focused on the effects of feed restrictions in a pasture-based dairy system have imposed feed deficits either pre-calving (Roche, 2007), immediately post-calving for five to six weeks (Bryant \& Trigg, 1979; Roche, 2007) or up to a 23\% restriction in dry matter intake (DMI) (Bryant \& Trigg, 1979). All experiments reported an immediate reduction in milk production; however, the longer-term effects varied depending on... Continued },
	issn = {1176-5283},
	author = {Kay JK and Phyn CVC and Williams YJ and Roche JR and Burke CR and Meier S}
}
@conference {41749,
	title = {Production and physiological indicators to select cows suitable for extended lactations},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {67},
	year = {2007},
	month = {Jan},
	pages = {315-319},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Wanaka},
	abstract = {Individual cows vary in their ability to maintain milk production for an extended lactation. Identifying production and physiological markers to indicate cows suitable for extended lactations would allow dairy farmers to make early decisions to withhold mating of individual cows or to continue milking specific nonpregnant cows through the winter months. Fifty-six genetically divergent overseas and New Zealand Holstein Friesians were allocated to three pasture-based dietary treatments (0, 3 and 6 kg concentrate DM/cow/d) and mating was withheld to target a 670-d lactation. Within each treatment there was little correlation between animal evaluation index values and milksolids (MS) production during the extended lactation period (>296 days in milk; DIM). There was a positive correlation between MS yield from the initial normal season (<296 DIM) and extended lactation MS production; and a negative correlation between body condition score (BCS) at theoretical dry off date (~296 DIM) and extended lactation MS yield. Plasma hormone and metabolite data from wk 1-10 postpartum demonstrated a positive association between nonesterified fatty acid levels and extended lactation MS production, whereas glucose,insulin, and insulin like growth factor-1 were negatively associated with extended lactation MS production. Overall, data indicate that the animal evaluation index is not a good indicator of animals suitable for extended lactation, however normal season milk production, early lactation plasmahormone and metabolite and late lactation BCS data may be useful to identify animals that will undergo a successful extended lactation.},
	issn = {1176-5283},
	author = {Kay JK and Aspin PW and Phyn CVC and Roche JR and Kolver ES}
}
@conference {41686,
	title = {Effects of conjugated linoleic acid on bioenergetics and milk production parameters in grazing dairy cows offered ad libitum or restricted pasture},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {66},
	year = {2006},
	month = {Jan},
	pages = {423-428},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Napier},
	abstract = {Conjugated linoleic acids (CLA) reduce milk fat synthesis in grazing dairy cows and often improve net energy balance (EBAL). Study objectives were to determine if CLA-induced milk fat depression (MFD) could be utilised during times of feed shortage (i.e drought) to improve bioenergetic and milk production parameters. Twelve multiparous mid-lactation rumen-fistulated Holstein cows were offered ad libitum (AL) or restricted (R) pasture and abomasally infused twice daily with 0 (0) or 50 (50) g/d CLA in a cross over design. Treatment periods lasted 10 d and were separated by a 10-d washout period. Milk and plasma samples were averaged from d 9 and 10, and EBAL was calculated from d 6-10, of the infusion periods. Pasture restriction reduced (P<0.05) the yield of milk and milk components. CLA reduced (P<0.01) milk fat yield by 45 and 46 \% in AL and R, respectively. There was no effect of CLA on milk yield nor milk lactose content or yield, however milk protein content increased (P<0.05) in both AL and R, resulting in an increased (P<0.05) protein yield of 6 and 9\% respectively. The CLA-induced changes to milk fat and protein increased (P<0.01) protein:fat ratio by approximately 2-fold in both AL and R. Calculated EBAL improved following CLA infusion (-1.84 vs. 11.22 and 1.59 vs. 13.77 MJ/cow/d for AL and R respectively; P<0.05), however CLA did not alter plasma bioenergetic markers (including insulin, non-esterified fatty acids, {\^a}-hydroxybutyrate, urea and glucose). Data indicate that during short periods of nutrient restriction, CLA may provide an alternative management tool to improve milk protein:fat ratio and calculated EBAL, however further studies are required to determine if CLA is effective at improving bioenergetic parameters during more severe nutrient restriction. },
	issn = {1176-5283},
	author = {Kay JK and Mackle TR and Bauman DE and Thomson NA and Baumgard LH}
}
@conference {41533,
	title = {Regulating milk fat synthesis: potential on-farm applications of basic science},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {65},
	year = {2005},
	month = {Jan},
	pages = {33-39},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {  This review covers results from numerous trials evaluating conjugated linoleic acid (CLA) effects on milk fat  synthesis and its potential as an on-farm management tool to improve dairy cow performance. Supplemental CLA reduces  milk fat synthesis in numerous animal models, and in grazing dairy cows can improve energy balance as well as increase  milk and milk protein yield.  Mammary lipid metabolism effects are thus far specific to  trans-10,  cis-12 CLA, and we  demonstrated trans-10, cis-12 CLA reduces mRNA expression of enzymes required for de novo fatty acid synthesis, fatty  acid uptake and intracellular transport, and triglyceride formation. The amount of CLA required to reduce milk fat synthesis  in lactating cows has little or no effect on circulating basal bioenergetic metabolites and hormones or stimulated responses  to homeostatic signals.  We hypothesized CLA can be utilized to stimulate milk fat depression when milk synthesis and  other physiological processes are limited by energy availability, as is the case in early lactation, during heat stress and  occasionally in pasture based dairying. Our research focuses on identifying the mechanisms of action and potential use of  CLA as an on-farm management tool to increase farm profit via increased milk production, improved reproduction and  decreased metabolic disorders.},
	issn = {1176-5283},
	author = {Baumgard LH and Kay JK and Moore CE and Roche JR and Vanbaale MJ and Rhoads RP}
}
@conference {41510,
	title = {Effect of precalving feeding level on the milk production of grazing dairy cows},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {64},
	year = {2004},
	month = {Jan},
	pages = {227-231},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Hamilton},
	abstract = {Fifty-two multiparous dairy cows were allocated to four treatments with an apparent daily intake of 5.8, 8.9, 10.0 or 11.2 kg dry matter (DM)/cow/day of pasture for 27{\textpm}9.6 days precalving. This equated to 1.3, 2.0. 2.3 and 2.6\% of liveweight (not including the conceptus weight; LW). Following calving, all cows were fed generously on pasture. Daily milk yields were recorded postcalving and fat, protein and lactose concentrations determined on 2 days each week for 5 weeks. Blood was sampled 17 days precalving, on the day of calving and on days 1, 2, 3, 4, 7, 14, 28 and 35 postcalving. Precalving plasma concentrations of insulin-like growth factor-1 (IGF-1) increased (P<0.05) quadratically with increasing pasture intake. Concentrations of growth hormone declined (P<0.05) linearly and concentrations of non- esterified fatty acids declined (P<0.001) quadratically with increasing DM intake. Plasma concentrations of these metabolites postcalving showed no effect of precalving feeding. Level of feeding precalving did not affect milk yield or the yield of fat, protein or lactose in milk, but postcalving DM intake was negatively (P<0.1) related to precalving DMI. These results indicate that 0.93 MJ metabolisable energy/kg LW0.75 was required in the final three weeks of gestation to maintain cow energy balance. },
	issn = {1176-5283},
	author = {Roche JR and Kay JK and Kolver ES and Aspin PW and Lee J and Sugar B and Napper AR}
}
@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 {41398,
	title = {Predicting Delta9-desaturase activity and the association with conjugated linoleic acid (CLA) concentration in bovine milk},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {63},
	year = {2003},
	month = {Jan},
	pages = {25-30},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Queenstown},
	abstract = {The major source of cis-9, trans-11 conjugated linoleic acid (CLA) in bovine milk is from the post-ruminal conversion of trans-11 C18:1 (TVA) by D9-desaturase. Activity of D9-desaturase is predicted from the product/substrate ratios of fatty acids dependant on the enzyme. Data from three experiments was investigated. Cows selected for having soft or hard milk fat were fed ruminally protected oilseed in spring 1999, and autumn 2000 or crushed full-fat rapeseed in autumn 2001. Cows with harder milk fat had higher concentration of milk fat (P<0.001), and lower concentrations (P<0.001) of TVA and CLA. Feeding ruminally protected oilseed in spring had no effect on milk fat, TVA or CLA concentrations but in autumn increased (P<0.001) milk fat concentration. Feeding crushed rapeseed depressed (P<0.001) TVA and CLA concentrations. Ratios of fatty acid pairs dependent on D9-desaturase (C10:1/C10:0, C16:1/C16:0 cis-9 C18:1/C18:0 and CLA/TVA) were lower in milk from cows with harder milk fat and the C12:1/C12:0, C14:1/C14:0 ratios were similar for soft and hard milk fat cows. Feeding ruminally protected oilseed decreased (P<0.001) all ratios except for C12:1/C12:0 in autumn 2000. Feeding rapeseed had no effect on the product/substraight ratios except the cis-9 C18:1/C18:0 ratio. None of these ratios were associated with milk fat CLA concentrations in spring however in autumn C14:1/C14:0 and C16:1/C16:0 were positively associated (P<0.05). Significant associations (P<0.001) between the milk fat cis-D9 C18:1/C18:0 ratio and CLA concentration and between TVA and CLA concentrations were also evident. This suggests that milk fat CLA concentrations may be influenced more by the availability of TVA than by the variation in the activity of D9-desaturase. },
	issn = {1176-5283},
	author = {Thomson NA and Chand A and Kay JK}
}
@conference {41359,
	title = {Concentrations of conjugated linoleic acid in milk from cows grazing pasture of fed a total mixed ration for an entire lactation},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {62},
	year = {2002},
	month = {Jan},
	pages = {240-241},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Palmerston North},
	abstract = {<p>Conjugated linoleic acid (CLA) is a collective term for the range of conjugated isomers of linoleic acid (C182). These fatty acids occur naturally in milkfat and have proven anticarcinogenic properties in laboratory rodents (Ip et al., 1999). Additionally, the various isomers have other reputed benefits for human health such as enhanced bone mineralisation, antidiabetic effects, reduced atherosclerosis and immune system modulation (Whigham et al., 2000). Such potential benefits for human health have focussed international research on enhancing concentrations of CLA in milk and dairy products. Overseas data show that one way to increase the concentrations of CLA in milk is to change the diet of cows from a typical total mixed ration (TMR) to pasture (Kelly et al., 1998; White et al., 2001). This points to a potential competitive advantage for the New Zealand dairy industry, in which pasture is already almost the sole source of feed. Despite this there are no data confirming the beneficial effects of pasture for enhancing CLA under New Zealand grazing conditions. The experiment described here used an existing experiment to compare the concentrations of CLA in milk from cows fed TMR or grazing pasture for an entire lactation under New Zealand conditions.</p>},
	issn = {1176-5283},
	author = {Audlist MJ and Kay JK and Thomson NA and Napper AR and Kolver ES}
}
@conference {41302,
	title = {Endogenous synthesis and enhancement of conjugated linolieic acid in pasture-fed dairy cows},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {62},
	year = {2002},
	month = {Jan},
	pages = {12-15},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Palmerston North},
	abstract = {The primary conjugated linoleic acid (CLA) isomer in milkfat, cis-9, trans-11 CLA, is a proven anticarcinogen in rodents and can be derived directly from ruminal biohydrogenation of linoleic acid. The major fatty acid in pasture, however, is alpha-linolenic acid; the biohydrogenation of which does not produce cis-9, trans-11 CLA as an intermediate. Therefore, in grazing cows, cis-9, trans-11 CLA must be produced by other sources, possibly via D9-desaturation of trans-11 vaccenic acid (TVA), a biohydrogenation product of both alpha-linolenic acid and linoleic acid. Studies were conducted to i) determine the importance of endogenous synthesis of cis-9, trans-11 CLA in pasture-fed cows and ii) increase the level of cis-9, trans-11 CLA. The first study involved abomasal infusion of sterculic oil (SO) to inhibit the activity of the D9-desaturase enzyme. Abomasal infusion of SO decreased the concentration of cis-9, trans-11 CLA in milk fat by 71\% (P<0.01; 3.6 c.f. 12.1 {\textpm} 0.15 mg/g fatty acid). The presence of cis-9, C 1 0:1, cis-9, C12:1 and cis-9, C14:1 in the milk fat of cows following SO treatment indicated D 9-desaturase was not completely inhibited. Using the changes in these fatty acids to evaluate the extent of D9-desaturase inhibition with SO treatment, an estimated 87-100\% of cis-9, trans-11 CLA in milk fat was of endogenous origin. In the second study, sunflower oil at 4\% DMI/cow/day invoked a 38\% increase (P<0.01) in milk fat TVA (61.3 c.f. 44.4 {\textpm} 0.51 mg/g fatty acid) and a subsequent 28\% increase (P<0.01) in cis-9, trans-11 CLA concentrations compared to control (28.5 c.f. 22.3 {\textpm} 0.19 mg/g fatty acid). Results demonstrate that endogenous synthesis is the major source of cis-9, trans-11 CLA in pasture-fed dairy cows and levels can be enhanced by increasing the supply of the ruminally-derived precursor, TVA. },
	issn = {1176-5283},
	author = {Kay JK and Mackle TR and Auldist MJ and Thomson NA and Bauman DE}
}
@conference {41324,
	title = {On-farm management to modify milkfat composition - a review of experiments undertaken at Dexcel to produce a spreadable butter directly from the cow},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {62},
	year = {2002},
	month = {Jan},
	pages = {100-103},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Palmerston North},
	abstract = {For many years it has been known from overseas studies that the composition and physical characteristics of milkfat are influenced by diet. The feeding of oilseeds had been shown to reduce the concentration in milkfat of short- and medium-chain-length fatty acids and to increase the concentration of long-chain unsaturated fatty acids. It was also reported that these changes resulted in softer milkfat and butter with improved spreadability at low temperatures. With this knowledge, a six-year collaborative research programme between the New Zealand Dairy Research Institute and Dexcel was undertaken to investigate the economic feasibility of producing a spreadable butter directly from the cow. The programme investigated the influence of each component in pastoral dairying that may possibly influence milkfat composition. These were: pasture, (location, defoliation interval, and species effects) on pasture lipid composition, grazed pasture effects (species and grazing rotation), supplementary feed effects (ruminally and non-ruminally protected oilseeds),   frequency   of   feeding,   and   milking   management.   Following   the   study   of   each   component   the   various components will be combined to develop a total farm management system to achieve the programme{\textquoteright}s goals. The goal of producing a spreadable butter directly from the cow has been achieved, but the programme has yet to develop a profitable farm system to produce the product under existing returns for milksolids.},
	issn = {1176-5283},
	author = {Thomson NA and Auldist MJ and Kay JK and MacGibbon AKH and Murphy JJ}
}
@conference {41289,
	title = {Effect of stage of lactation on the efficiency of Jersey and Friesian cows at converting pasture to milk production or liveweight gain},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {61},
	year = {2001},
	month = {Jan},
	pages = {213-216},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {A study comparing Jersey (J) and Friesian (F) cows in early (EL), mid (ML) and late (LL) lactation and offered either ad libitumpasture (P) or restricted pasture allowance + a concentrate (PC) was conducted. Breeds were grazed at a similar live weight (LWT)/ha (1340 and 1850 kg LWT/ha for P and PC respectively). F cows produced 10\% more MS/cow/day than J cows. DM intake (DMI) on P was 13.6 kg DM/cow/day for F and 11.3 kg DM/cow/day for J cows but if expressed at constant LWT, J consumed more than F cows (30.3 versus 28.0 + 0.8 g DMI/kg LWT). During EL, J cows gained less live weight than F cows but in LL the reverse occurred. An interaction between breed and stage of lactation also occurred for the conversion efficiency of pasture DM to milkfat, protein, casein and MS. For the yield of milkfat, protein and casein J cows in EL were more efficient than F cows but in LL no breed effect on the conversion efficiency of pasture to these components occurred. The difference between breeds in partitioning feed to milk solids and liveweight gain at different stages of lactation suggests different management opportunities for each breed to more efficiently convert pasture to MS.},
	issn = {1176-5283},
	author = {Thomson NA and Kay JK and Bryant MO}
}
