Dairy Business & Technology Advisor, Teagasc, Limerick
Replacement heifers born in 2013 are going to be the first heifers to be milked in a quota free environment. Now is the time to act to maximise the number of heifers that enter the parlour in 2015.
Poor fertility in replacement heifers is often due to heifers being underweight at mating start date (MSD). A recent study, carried out in Teagasc, Moorepark, gathered bodyweight (BW) information at MSD from over 870 Holstein-Friesian heifers on 48 farms across the country. The effect of BW on lactation performance and survivability during their first three lactations was examined. Only fifty five percent of heifers that were <290kg at MSD were cycling, while almost 80 per cent of heifers over 317kg were cycling and had a mean calving date 16 days earlier than the lighter heifers. However, it was found that the mean calving date of heifer’s ≥343 kg at MSD had slipped to March 29 by their third lactation, eight days later than heifers that weighed between 317kg and 342kg at MSD. It was also found that a significantly higher proportion of heifers that weighed 317-342kg at MSD survived to second and third lactation.
Target Daily Gains
Heifers should be 90 per cent of their mature BW at calving, which for a 600kg cow is 550kg, and the target weight for these heifers at MSD is 60 per cent of calving weight, which in this case is 330kg. If we assume an average calving date of February 20 for these calves and a birth bodyweight of 45kg, then these calves have 425 days to gain 285kg of liveweight before mating on April 20 the following year. This works out at 0.67kg/day for every day of this period or 20kg per month. This is easily achieved at grass, but not so easy indoors on silage.
Many farmers tend to over-estimate the average daily gain (ADG) that these heifers can gain indoors on silage and this often leads to underweight heifers at turnout.
On a silage only diet, a weight gain of only 0.3kg/day can be expected over the winter from a 70 per cent DMD (Dry Matter Digestibility) silage. Typically, silage and 1.5-2kg concentrate/day will result in a weight gain of almost 0.5 kg/day. To compensate for this lower ADG, heifers have to gain >0.75kg/day while at grass. Table 1, illustrates the importance of a substantial grazing period before MSD. At this stage farmers should have identified a paddock or two on which to turn out heifers (especially light heifers) at the end of February/early March. It should also be noted that where mature cow weights are lower than 600kg then lower heifer weights than those shown in table 1 may be acceptable.
What should the protein percentage of the ration for my heifers be?
Unless heifers are well ahead of the targets set out in Table 1, then some supplementation will be required while indoors on silage. One of the most common questions asked by farmers is “what should the protein percentage of the ration for my heifers be?” This question can only be answered correctly if the protein percentage of the silage that is being supplemented is known. Silage analyses cost €30-40 and yet it is amazing the number of farmers that do not carry out this simple task annually. One extra heifer in the parlour in 2015 would pay for almost 40 silage analyses.
Table 2 illustrates the protein level of the ration required depending on the protein level of the silage being supplemented. For example, if your silage is 10 per cent protein you will need to supplement with either 2kg of an 18 per cent ration or with 3kg of a 16 per cent ration.
Compensatory growth is when animals that have been nutritionally restricted increase their growth rate and maintain it for long enough to catch up completely to their contemporaries that have been unrestricted. Frequently, farmers depend on compensatory growth following the first winter for higher weight gains in early spring and the attainment of target weight. However, from two years of studies completed at Teagasc Moorepark it was found that compensatory growth did not occur until late summer when the breeding season was over. Therefore, the concept of compensatory growth cannot be relied upon to ensure heifers achieve target weight.
So, what are the first steps a farmer should undertake this winter to ensure as many heifers as possible hit their target weights at MSD? The first step is to establish the weights of your heifers. Some farmers and some discussion have invested in their own scales, but these are still the minority. ICBF now offer a weighing service to all farmers. To weigh 30 heifers will cost approximately €100, but like the silage analyses, if it means getting one extra heifer in the parlour, it is well worth the cost.
What can I do about light heifers now?
So you’ve gone to the bother of weighing your heifers and you find out that 25 per cent of them are weighing 200kg on average on November 1. This means these light heifers now have 170 days to gain 130kg or 0.76kg ADG. Is it possible for these heifers to hit 330kg on April 20 next? Yes it is, but they need preferential treatment to achieve this. Firstly, ensure all parasite control is up to date. Then separate lighter weanlings into a separate management group. Teagasc Grange has shown that lighter weanlings respond better to meal feeding than heavier weanlings. A 200kg weanlings will eat 2.3 per cent of its bodyweight which is about 4.5kg dry matter. To avoid stomach upsets, no more than 50 per cent of the weanling diet should consist of concentrates (when supplementing silage). Also heavy meal feeding of weanlings can result in heifers laying down excessive fat in their udders. Therefore, feed 2.5kg meal fresh weight (2.2kg Dry Matter) from housing until January 1, then ease back to 2kg meal until turnout. Aim to turnout this lighter bunch in mid/late February. Other factors such as clean water, appropriate ventilation, feed space, parasite control etc are also important if heifers are to hit target weights.
- Light heifers can still be in the parlour in 2015, but only if you act now and put a system in place to ensure this happens. Below I have summarised this system into four simple steps;
- Supplement; and,
- Early turnout.