Importance of Growth Rates
Official statistics (LIC/DairyNZ 2012-13) show that the average Holstein Friesian is not achieving mature weight until it is a 6 year old. With over 80 kg of growth in the first season, this means that the young cow is having to partition energy towards growth when this energy should be used for milking.
The chart below shows the milk production from an average sized herd. The purple dots denote the number of animals in each lactation, so for the first calvers (2 year olds) there are 70 of them. The blue cross above shows their average milk yield if they milk for a full lactation of 305 days.
The green bars above and below show the range of yields.
The best heifers in this herd would have achieved around 350 kgMS, whilst the worst only around 210 kgMS.
The highest yielding group are the sixth calvers (8 year olds), but again the range is large between the best and worst.
The orange line denotes the financial breakeven point so animals included are below the line are not contributing directly to the business profit.
Part of the answer lies in ensuring that heifers are well grown before they reach the milking herd. The financial cost of not getting heifers at >90% of mature weight is high. Investing more in young stock can result in some healthy returns.
It is important to provide the growing heifer with a balanced supply of minerals and vitamins to support her through her first two years of life. For the growing animal it is important to consistently grow the frame, the muscles and the fat at the right time to ensure she enters the herd in prime condition.
The major minerals of magnesium, phosphorous, calcium and sodium are necessities as well as trace elements of copper, selenium, manganese, cobalt, zinc and iodine and Vitamins A, D3 and E.