INFLUENCE OF THE INTENSITY OF FORMATION ON LIVE WEIGHT OF HEIFERS AND MILK PRODUCTIVITY OF COWS
Authors: Polupan Yu. P. , Siriak V. A. 
Published: May 2019

It is known that the intensity of the formation of repair heifers in some way correlates with the weight gain and their future milk productivity, but contradictory conclusions about the direction and strength of this correlation need to be further studied, this idea was chosen as an aim of our research.
This study was conducted on breeding farm «Terezyne». Data included 861 animals of Holstein, Ukrainian black and white and red and white dairy breeds.
The age dynamics of the body weight of repair heifers is estimated from birth to the age of 18 months at an interval of three months, the average daily gain is estimated in three months intervals (0–3, 3–6, 6–9, 9–12, 12–15, 15–18) and half-yearly intervals (0–6, 6–12, 12–18). Intensity of formation was evaluated according to Yu. K. Svechin (1979; 1985).
It is established that the value of the index of formation depends on the duration and age of the comparable periods. The higher value of the index acquires in comparison of periods 0–6 and 12–18, 0–6 and 6–12, 0–3 and 9–12 months, the lowest – 6–9 and 9–12. Coefficients of variation for different variants of calculating the index of formation vary in the range from 6.7 to 46.2%, which determines the sufficient possibilities for selection.
Growing of heifers was carried out at a rather high level. Their daily average gain decreased from 740 g (the first three months after birth) to 519 g (15–18 months). The firstborns had an advantage over the standard of Holstein breed in the milk yield, milk fat and milk protein by 53.7–60.1%, Ukrainian black and white dairy breed − 190–198.1%, Ukrainian red and white dairy breed − by 200.9–204.8%.
Due to the correlation analysis, a statistically significant result of correlated variability was found in the most of the studied variants of the index of formation with a body weight of heifers at the age of 18 months, 305 days milk yield of firstborns and the calving interval between the first and second calving. When comparing of periods 0–3 and 3–6, 0–3 and 6–9, 0–3 and 9–12 and 6–12 and 12–18 months, the correlation coefficients have a higher level of statistical probabilities. When comparing of the second and third half-year periods of postnatal development these correlations have a reliable inverse direction.
The inverse correlation between the intensity of formation of body weight and the milk yield of firstborn was noted. Emphasis should be placed on the decrease of the values of the correlation coefficients to the unreliable level in the case of comparing two periods either before or after the intensive maturing of heifers (0–3 and 3–6, 6–9 and 9–12, 6–12 and 12–18 months). The highest statistically significant inverse correlation with the milk yield of firstborns was defined in the cases of comparison of semi-annual periods at the age of 0–6 and 12–18 and 0–6 and 6–12 months and three-month periods − at the age of 3–6 and 9–12 and 0–3 and 9–12 months. There was not find correlation between the intensity of formation of heifers body weight and the calving interval between the first and second calving. Correlation coefficients were low (less than 5%), multidimensional and in all cases insignificant.
In all studied variants, heifers with the fast formation of body weight had significantly higher average daily gain from birth to three and six months and it was lower in the age from nine to fifteen months. The revealed tendency has led to the maximum increasing of advantage of these animals over heifers of the same age with a slow formation of body weight at the age of three (by 1.6–11.4 kg or 1.5–11.6%) and six (by 9.8–17.5 kg or 5.9–9.8%) months with the next decrease of intergroup difference and its practical leveling to insignificant level at the age of 18 months.
By milk yield, milk fat and milk protein of firstborns the significant advantage was marked for in animals with a slow decline in relative growth rate. The most significant this advantage was at the age of 3–6 and 9–12 months (respectively 402; 15.3 and 13.4 kg or 6.4; 6.5 and 6.5%), 0–6 and 12–18 months (381; 13.9 and 12.6 kg or 6.1; 5.9 and 6.1%) and 0–6 and 6–12 months (321; 12.1 and 10.4 kg or 5.1; 5.1 and 5.0%). Thus, taking into account the maximum correlation and the most effective advantage over milk productivity of firstborns, it has been found that the most effective is the selection of heifers with a slow formation of body weight at the ages of 3–6 and 9–12 months.
On the base of one-factor dispersion analysis it was found a significant influence (over 20%) of the father's origin on the variability of most tested indexes of formation at the age of 0–3 and 9–12, 3–6 and 9–12, 0–6 and 12–18 and 0–6 and 6–12 months. The significant influence of father's origin demonstrates the potential effectiveness of the bulls’ selection on a certain characteristics of their daughters.
Conclusions. 1. Heifers with a fast formation of body weight have significantly higher average daily gain from birth to six months and lower average daily gain at the age from nine to fifteen months, which results in the maximum increasing of the advantage of these animals over the heifers of the same age with a slow formation of body weight at age three (by 1.6–11.4 kg or 1.5–11.6%) and six (by 9.8–17.5 kg or 5.9–9.8%) months (P < 0,001).

For the milk yield, fat content and protein content of firstborns a significant advantage, on the contrary, had the animals with a slow formation of body weight. The most significant this advantage was in comparison of relative gains of body weight at the age of 3–6 and 9–12; 0–6 and 12–18; 0–6 and 6–12 months (5.0–6.5%, P< 0.001).
Any tendencies of changes of fat content and protein content, depending on the intensity of the body weight formation of repair heifers and a significant correlation between the formation of live weight and calving interval between the first and second calving was not found.
A high significant level of inheritance (up to 26.3%) gives grounds to expect sufficient results of selection in increasing of milk yield of firstborns by indirect predictive constitutional indicator of the intensity of body weight formation.