@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 {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 {41243,
	title = {Lipolytic response of New Zealand and overseas Holstein-Friesian dairy cows challenged with epinephrine},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {61},
	year = {2001},
	month = {Jan},
	pages = {48-51},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {Sixteen New Zealand Holstein-Friesians (NZ HF) and 15 overseas HF (OS HF) grazing pasture or fed a total mixed ration (TMR) were subjected to an epinephrine challenge during early lactation. A genotype x diet interaction trend (P=0.10) was observed; when grazing, OS HF displayed the greatest glycerol response, with the reverse occurring on TMR. No genotype or diet differences were observed for the glycerol or non-esterified fatty acid response. Dairy cows of both genotypes fed TMR produced a glucose response 31\% greater than both genotypes grazing pasture. These preliminary results suggest that genotype x diet-induced differences in the rate of lipolysis may occur in Holstein-Friesians during early lactation. These differences may be a function of small differences in energy balance. Feeding TMR was associated with a greater glucogenic response to epinephrine, which probably resulted from greater hepatic reserves of glycogen or simply a greater energy demand by the mammary gland. },
	issn = {1176-5283},
	author = {Kolver ES and Roche JR and de Veth MJ and Mackle TR}
}
@conference {41223,
	title = {Endocrine control of milk protein production in well-fed dairy cows},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {60},
	year = {2000},
	month = {Jan},
	pages = {303-306},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Hamilton},
	abstract = {A hyperinsulinemic-euglycemic clamp was used to investigate the effect of insulin on milk protein synthesis in wellfed Holstein cows (n=4) with or without additional amino acids. Cows were fed a dry total mixed ration diet formulated to exceed requirements for metabolizable energy and protein. During abomasal water infusion, the insulin clamp increased milk protein yields by 15\% (+128 g/d; P<0.01); when combined with abomasal infusion of casein plus branched-chain amino acids, milk protein yield was increased by 25\% (+213 g/d; P<0.01). Concentrations of casein and whey proteins in milk were increased by insulin clamp treatments, with little change in their relative proportions. Providing amino acids without the insulin clamp had no effect on any production variables. Results confirm the important regulatory role of the endocrine system in milk protein synthesis and demonstrate the potential to produce milk protein is not fully expressed.},
	issn = {1176-5283},
	author = {Mackle TR and Dwyer DA and Bauman DE}
}
@conference {40986,
	title = {The value of monozygotic twins in milk composition experiments.},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {58},
	year = {1998},
	month = {Jan},
	pages = {55},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Monozygotic (identical) twins have for many years been used to increase the statistical power of experiments in a range of scientific disciplines (Dick and Whittle,1951). In dairy cows, variation within identical twinsets for a given biological parameter is usually substantially less than the variation between unrelated cows or between fraternal twinsets (Hancock 1953; Brumby and Hancock, 1956). Thus the number of identical twins required in an experiment is often considerably less than the number of unrelated cows necessary to achieve the same statistical precision. The experiments described here were conducted to quantify the twin efficiency values of a range of milk composition parameters.},
	issn = {1176-5283},
	author = {Auldist MJ and Mackle TR and Hooper RJ and Henderson HV}
}
@conference {40830,
	title = {Effect of calving liveweight on milk yield and composition and daily dry matter intake in Friesian and Jersey heifers},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {56},
	year = {1996},
	month = {Jan},
	pages = {260-262},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Milk yield and composition were measured weekly throughout  lactation, and daily dry matter intake (DMI) on 7 occasions, for Friesian  (n=16) and Jersey (n=16) heifers calving at either high (H) or low (L)  liveweights. During the 8 weeks pre-partum, heifers were fed to achieve  calving liveweights of 404 (H Friesian), 354 (L Friesian), 334 (H Jersey) and  277 (L Jersey) kg. All heifers were fully fed on pasture as one group for the  whole of lactation. Calving liveweight had no effect on average DMI over the season. Average  DMI was higher for Friesians than Jerseys while average liveweight- corrected DMI was slightly greater for Jersey than Friesians. Average daily  milk yields and yields of lactose were lower for L than H heifers. Solids- corrected milk yields and yields of milkfat and protein were unaffected by  calving liveweight, but milkfat \% and protein \% were higher for L than H  heifers. The Friesians had higher milk yields, and yields of protein and  lactose, but lower milkfat \% and protein \% than Jerseys. No effect of restricted feeding during late pregnancy in heifers was  demonstrated on milk solids production in the subsequent lactation.},
	issn = {1176-5283},
	author = {Mackle TR and Parr CR and Stakelum GK and Bryant AM and Macmillan KL and Auldist MJ}
}
@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 {40675,
	title = {Early lactation response of dairy cows to pasture under two different nitrogen fertiliser regimes},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {55},
	year = {1995},
	month = {Jan},
	pages = {82-84},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Near-infrared (1100-2500 nm) reflectance spectra were measured on   128 beef ribeye samples using a scanning monochromometer and calibrated   against standard laboratory analysis to develop a rapid method for measuring   intramuscular fat of beef.    A pilot run was conducted on 38 frozen ribeye samples, ranging in fat   content from 94 to 325g/kg dry weight, to evaluate sample preparation   methods (frozen slices, thawed slices, coarse mince. After scanning of   subsamples, fat content of the sample was then measured using Soxhlet   extraction. Standard error of calibration (SEC) was 9g/kg dry weight for   spectra collected from minced samples compared to 25g/kg for frozen slices   and 15g/kg for thawed slices.    A second set of 90 frozen ribeye samples (fat content range 56-305 g/kg dry   weight) was used to test and improve this calibration, using 3 subsamples of   minced beef per sample. The ability of the initial calibration equation to   predict fat content of these samples was poor. A more robust calibration was   then attempted by pooling the data from the two sets. The SEC of this   extended set was 16 g/kg dry weight (10\% of the sample set mean) and the   multiple R2 of calibration was 0.92. The standard error of prediction for  new samples was estimated from internal cross-validation runs as 19 g/kg.   Prediction of fat content of an independent validation set of 24 samples had a   standard error of 20 g/kg dry weight. Analysis of the calibration results   suggested that a major source of error in the calibration was hererogeneity   between subsamples, with the standard deviation of prediction of different   subsamples from the same ribeye being larger than the standard error of cross   validation.    These results indicate that Near-Infrared reflectance spectroscopy may   provide a rapid objective method for estimating intramuscular fat of beef.   },
	issn = {1176-5283},
	author = {Mackle TR and Parr CR and Bryant AM}
}
