Season of birth is associated with first-lactation milk yield in Holstein Friesian cattle.

The aim of the present research was to assess factors associated with first-lactation milk yield in dairy heifers, including maternal and environmental factors, factors related to the development of the heifer and factors related to its offspring such as gender of the calf. In addition, the potential underlying mechanism, in particular metabolic adaptations, was further explored. Data on body growth, reproduction and milk yield of 74 Holstein Friesian heifers on three herds in Flanders (Belgium) were collected. At birth, body measurements of the heifers were recorded and blood samples were taken (in order) to determine basal glucose and insulin concentrations. Body measurements were assessed every 3 months until first calving, and gender and weight of their first calf were recorded. Information on fertility and milk yield of the heifer and its dam were collected from the herd databases. Daily temperature and photoperiod were recorded from the database of the Belgian Royal Meteorological Institute. Linear mixed models were run with herd as a random factor, to account for differences in herd management. Heifers grew 867±80.7 g/day during their first year of life and were inseminated at 14.8±1.34 months. First calving took place at 24.5±1.93 months, at a weight of 642±61.5 kg and heifers produced 8506±1064 kg energy corrected milk during their first 305-day lactation. Regression models revealed that none of the maternal factors such as milk yield and parity, nor the growth of the heifer during the 1st year of life were associated with milk yield during first lactation. Age, and to a lesser extent BW at first parturition were positively associated with first-lactation milk yield. In addition, the season of birth, but not calving, had a significant influence on milk yield, with winter-born heifers producing less than heifers born in any other season. The lower yielding winter-born heifers had higher insulin concentrations at birth, whereas glucose concentrations were similar, the latter being suggestive for lower insulin sensitivity of the peripheral tissues. Furthermore, environmental temperature at the end of gestation was negatively correlated with neonatal insulin concentrations. In conclusion, results of the present study suggest heifers born during the hotter months are born with a higher peripheral insulin sensitivity, finally leading to a higher first-lactation milk yield.

Effects of long term iodized table salt consumption on serum T3, T4 and TSH in an iodine deficient area of Bangladesh.

The effect of iodized and non-iodized table salt in goiter hyper-endemic area on the thyroid gland and its hormones T3, T4 and Thyroid Stimulating Hormone (TSH) were studied in two hundred subjects from the Center for Nuclear Medicine and Ultrasound, Mymensingh. Iodized and non-iodized salt users were called study and control groups respectively. The mean concentration of T3 were 2.38 nmol/L and 2.22 nmol/L & T4 concentration were 128.67 and 123.72 nmol/L in the study and control group respectively. The mean TSH concentration was 1.52 mIU/L and 1.62 mIU/L in study and control group. The data indicated that continuous and long term use of iodized salt increased both T3, T4 and decreased TSH in such a limit which was not statistically deferent at P< 0.05 level as compared to the control group. There was no significant change in occurrence of (hypo and hyper thyroidism or iodinated salt induced thyrotoxicosis) adverse effect, following iodine supplementation. The study shows that, mandatory mass iodination of table salt consumption in a hyper-endemic iodine deficient area is safe and does not cause any side effect. We suggest close regular monitoring of T3, T4, and TSH and further evaluation by specifically designed studies for any probable link between iodine induced hypo or hyperthyroidism and mass iodination of table salt consumption.