DIFFERENT NUTRITION OF CALVES IN RELATION TO THE LEVELS OF THYROID-HORMONES AND SOME BIOCHEMICAL INDEXES

The aim of this experiment was to determine the effects of different n utrition on the levels of thyroid hormones and biochemical indexes in blood plasma after the calves were introduced from a maternity barn in to novel conditions. The study was conducted with 10 Holstein-Friesian female calves. At the age of 10 days the calves were randomly divided into two groups of 5 animals and brought from a maternity barn into a n individual housing in the hutches. After the weaning at the age of 9 weeks the calves were kept in a loose housing system with bedding. Un til 10 days of age calves were fed the same amount of colostrum and na tive milk. After moving to individual hutch, the first group of animal s was again fed native milk and second one were fed by commercial star ter milk replacer Lactavit diluted 1 : 9. Both groups were fed the sam e volume of milk liquid at 6 a.m. and 5 p.m. Nutrient composition of n ative milk in 1 kg of the origin mass were 125 g DM, 20 g PDIN and 1,7 0 MJ NEL and for Lactavit 958 g DM, 211 g PDIN and 8,78 MJ NEL. The in take of concentrates and alphalpha hay during the experimental period was ad libitum. The body weights were measured at 2nd, 5th, 7th, 9th a nd 17th week of age. The blood was sampled by a puncture of vena jugul aris into the tubes with heparin four hours after morning feeding at 1 st, 2nd, 3rd, 4th, 5th, 6th, 7th, 8th, 9th, 10th, 11th, 12th and 17th week of age. In blood plasma we observed the concentrations of thyroid hormones (thyroxine T4 and triiodothyronine T3 - ADICO, Praha), gluco se, total proteins and amino nitrogen (Bio-Lachema test, Brno). The bo dy weight at the age of 7 and 9 weeks and growth rate at the age of 7 weeks were significantly higher in calves fed native milk (Tab. I). Af ter change of housing at the age of 10 days the average concentrations of thyroid hormones increased in the group of native milk fed animals (Fig. 1). In this group we have found significantly increasing the T4 levels over time from 2nd on 3rd weeks of age (from 63.94 +/- 28.30 n mol/l to 80.10 +/- 20.10 nmol/l; P < 0.01). In the group of calves fed milk replacer we observed decreasing of thyroid hormones after change of housing and feeding compared with values of previous period (Fig. 1). In this group of animals the increase of thyroid levels started at the age of 4 or 5 weeks. We have found significantly higher average l evels of thyroid hormones in group of calves fed native milk during pe riod of different milk nutrition (Tab. II). After calf weaning at the age of 9 weeks the thyroid hormone concentrations decreased in calves of first group at 10 weeks of age (T3 from 2.53 +/- 0.35 nmol/l to 1.2 7 +/- 0.38 nmol/l, P < 0.01; T4 from 108.09 +/- 24.78 nmol/l to 60.44 +/- 20.35 nmol/l, P < 0.05). The same effects but not significant were observed after weaning also in the second group (T3 from 2.21 +/- 0.5 7 nmol/l to 1.23 +/- 0,77 nmol/l; T4 from 77.96 +/- 13.94 nmol/l to 45 .32 +/- 21.59 nmol/l). The average levels of glucose and amino nitroge n between groups during were not influenced by milk nutrition (Tab. II , Fig. 2). We found significant decrease in a glucose concentration in both groups after the weaning of calves (6.05 +/- 1.08 nmol/l to 4.29 +/- 0.33 mmol/l, P < 0.05 - native milk; 5,28 +/- 0.61 nmol/l to 3,99 +/- 0,42 mmol/l, P < 0.05 - milk replacer). The levels of total prote ins between the groups during different nutrition were significantly d istinguished (P < 0.01). We found positive effects of nutrient availab ility during changes of housing of very young calves on growth intensi ty, body weight and thyroid hormone concentrations. Higher nutrients i ntake by animal fed native milk result in better adaptation of calves fed native milk to the stress of housing change. The decreased levels of thyroid hormones longer time after the change of housing found in t he group of calves fed milk replacer are caused probably by lower inta ke of nutrients. It can be discussed, whether nutrition by milk replac er after the transport of very young calves to new housing conditions provide enough energy needed for finishing of the development of the r egulatory mechanisms and for their successful adaptation to the new ho using conditions, climate.