@conference {3672,
	title = {Field investigation of the iodine status of farms in the North Island of New Zealand},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {77},
	year = {2017},
	month = {06/2017},
	pages = {77-81},
	address = {Rotorua},
	abstract = {Over a 10-year period 104 farms in the North Island were attended on a consultancy basis, and of these, 29 farms were identified as having clinical signs associated with iodine deficiency (high peri-natal calf mortality, poor conception rate and/or low pregnancy rate). Mean pasture iodine concentrations (n=24) were 0.28 mg/kg (SD=0.16) ({\textquoteleft}adequate{\textquoteright} range: 0.40-0.80 mg/kg). Mean animal plasma inorganic iodine (PII) concentrations (n=17) were 40.6 μg/L (SD=16.28) ({\textquoteleft}inadequate{\textquoteright} range <45 μg/L). Marginally low iodine status (20-45 μg/L) was present in 13.5\% of farms (14 of 104). The overall average deficit for the farms with low pasture iodine (n=19) was calculated to be 3.0 mg iodine per cow per day. Corrective treatment was computed for each farm and made pri-marily through weekly addition of iodine to the drinking water. Following iodine supplementation, mean animal PII was 60.8 μg/L (SD=19.50), a 50\% increase over initial values. For individual cattle, there was a significant reduction in the proportion (73.5\% to 23.5\%) whose PII was marginally low (P=0.001). Clinical responses in livestock were monitored, and on the iodine supplemented farms there was some evidence for a reduction in peri-natal calf mortality and an increase in conception rates, but the amount of data was limited. Iodine supplementation was seen to contribute to an overall increase in pregnancy rates on ten farms (from 79.4\% to 91.1\%). It is concluded that iodine deficiency is common in North Island pasture-based livestock farms, that it is responsive to dietary supplementation, and that supplementation may be associated with improved reproductive performance.},
	issn = {1176-5283},
	author = {Anderson PD and McGhie DON and Parkinson TJ}
}
@conference {41988,
	title = {Iodine deficiency in dairy cattle},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {67},
	year = {2007},
	month = {Jan},
	pages = {248-254},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Wanaka},
	abstract = {Clinical signs of iodine deficiency (e.g. non-visible oestrus, low first service conception rate, stillbirths), plus low (<45 nmol/L) serum thyroxine (T4) concentrations were observed in dairy cows from 12 farms in the Manawatu. Goitre, as determined by diffuse thyroid hyperplasia,plus significantly (p<0.05) increased thyroid size, weight and thyroid:bodyweight ratio, was found in 16\% (6 of 38) of stillborn calves from these farms. Goitre was present in calves from 42\% (5 of 12) of the herds. One of these farms was chosen to investigate temporal changes in concentrations of the thyroid hormones, thyroxine (T4) and tri-iodothyronine (T3), as an indicator of iodine status, and to attempt to determine the optimum time for sampling. Blood samples were collected from a cohort of animals from the herd (20 representative animals from 400 cows) 8 times over a 12 month period, for measurement of total serum iodine (TSI), T3 and T4 concentrations in both individual cows and pooled (10 cows) samples. T4 was maximal in June (58.6 nmol/L) and lowest (39.2 nmol/L) in October (P<0.05). Between November and Augusts meanTSI varied (NS) from 31 {\textpm} 9 to 47 {\textpm} 9 {\textmu}g/L, but was significantly (P<0.01) higher in October (91 {\textpm} 16 {\textmu}g/L). T4 concentrations were(P<0.05) related (r = 0.35) to TSI between November and August (7/8 blood samplings), but were widely divergent (r = 0.08) in October. Concentrations of T3 were unrelated to TSI (r= 0.07). In pooled samples, concentrations of TSI, but not T3 or T4, were closely related to the mean concentrations in individual animals. An iodine-response study was also carried out on the same herd. Half the herd (200 of 400) were given (6 mL i/m) iodised oil (Flexidine, Bomac) before mating and before calving. The pregnancy rate in anoestrous cows treated with iodine was 13.9\% higher than in untreated cows. It was concluded that T4 (individual animals) or TSI (pools of 10 cows) give equivalent information about the iodine status of a herd, except in the post calving period. However, the reference range needs to be validated by further response trials.},
	issn = {1176-5283},
	author = {Anderson PD and Dalir-Naghadeh B and Parkinson TJ}
}
