HEIFERMAX

In a previous post I explained the difference between genotype and phenotype. Many of the high producing Holstein cows in Australia have the genetic potential to produce as much as 15,000 litres/lactation. Their phenotype, or the actual amount they produce per lactation, is influenced by many interacting factors.

These influences include colostrum status; early life health and growth rates; diet & growth rates in the pre-pubertal and pre-calving periods; stress levels; social position in the herd; lactating and dry cow rations; climate etc. These interacting, external factors might exert such an influence on the animals’ genetic potential that they only produce 8,000ℓ/lactation. Indeed, producing to their genetic potential may not be the most economical choice and the farmer might deliberately manipulate the cows’ environment so that they cannot reach their 15,000ℓ/lactation potential. Several of the factors which affect phenotype for milk production can be manipulated without long term detriment to the animal. Colostrum status and early life health and growth rates of neonatal heifers are not in this category. 

Negative welfare and productivity consequences of restricted feeding

 “Early adaptations to a nutritional stress or stimulus permanently change the physiology and metabolism of the organism and continue to be expressed even in the absence of the stimulus/stress that initiated them…” (Patel and Srinivasan, 2002)

If one applies the statement above to the consequences of feeding of neonatal dairy heifers, it supports the questioning of whether or not the current Australian calf feeding recommendations are achieving the goal of raising heifers capable of reaching their genetic potential for milk production when they enter the herd. The fact that 30 to 50% of Australian heifers do not survive to their second lactation suggests that some aspects of our current rearing recommendations are not effective and should be reviewed. One of the management areas responsible for this high rate of loss is early life health and growth rates.

Since the 1950’s when early weaning began to be encouraged, the biological, and therefore welfare, needs of dairy heifers have been ignored in the global dairy industry’s quest for ways to increase profitability. No other system of rearing young animals for any form of future production restricts milk intake to force early weaning. In the young of other species growth, health, nutrition and future productivity have been demonstrated to be closely inter-related but until recently this was an unresearched area of dairy production. Successful commercial producers of beef cattle, pigs, prime lambs and thoroughbred foals ensure that their young stock have access to unlimited feed (usually in the form of unrestricted suckling coupled with high quality pasture or concentrates) for at least the first few weeks of life. Producers know that this management approach results in minimal morbidity and mortality rates, optimal performance in later life and capitalises on the high feed conversion rates in young animals.

In addition to the serious economic consequence of reduced lifetime milk production, limit feeding heifers has been demonstrated to result in poor weight gains, higher morbidity & mortality rates and compromised welfare status.

Calves fed restricted volumes of milk have demonstrated behaviours indicative of chronic hunger. These include reduced play behaviour in calves, increased vocalisation, disrupted sleep patterns and an increased number of unrewarded visits to automatic feeders. All these are indicators of negative calf welfare.

Globally, the dairy industry has to be pro-active in meeting the changing expectations of consumers who are increasingly demanding that their food is produced by industries with high animal welfare standards. To establish an impeccable welfare reputation, the industry needs be able to demonstrate that it has made positive changes to ensure that all facets of calf welfare will stand up to scrutiny.

Research

Over the last two decades, scientists, aware of the fact that dairy calves are the only intentionally limit fed neonates and that the long term results have been sub-optimal, have researched:-

·         whether standard calf nutrition programs which limit liquid feed to 10% of birth weight contribute to high morbidity and mortality rates;

·         whether these restricted feeding programmes fail to provide sufficient nutrients for adequate development of the immune system;

·         whether an increased nutrient intake during the first few weeks of life would improve growth and immune system maturation and function;

·         what, if any, effect limited feeding regimes have on lifetime productivity;

·         whether there are other interacting factors in early life management which affect lifetime productivity;

·         whether calves can be “programmed” for later production.

Growth linked to passive transfer

The results of the many trials in this area now show that adequate passive transfer combined with high levels of nutrients in the first few weeks of life can enable heifers to reach their genetic potential for milk production. Scientists now believe that certain factors in colostrum can, when combined with adequate nutrition, metabolically programme heifers to produce more milk than their peers who have either failure of passive transfer and/or restricted nutrient intake.

The biological needs of heifers can more closely be met by “accelerated” or “intensified” feeding programmes. In fact, these would be more correctly referred to as natural or welfare friendly feeding programmes, as they are much closer to the biologically normal diet a calf would consume in its natural state. The concept of “accelerated” feeding is not new; reports from 200 years ago state that the leading European dairy farmers were feeding their calves 8ℓ milk/day and achieving growth rates of ≈ 0.9kg/day.

The ability to derive benefits from a high nutrient intake in the first few weeks of life is dependent on adequate colostrum levels. One study investigated the benefits of high feeding rates in calves with either adequate passive transfer (>10g/ℓ IgG) or inadequate passive transfer (<10g/ℓ). Calves from each group were fed either a conventional, limit fed amount of CMR or an “intensified” level. The results showed little difference in weight gains between the two feeding regimes in the poor passive transfer group but there was a significant weight difference in the group of calves with adequate passive transfer.

Benefits of feeding more milk

There are many benefits of feeding more milk than is currently recommended in Australia. Even if dairy farmers decide that having cows which produce to their genetic potential is not economical, a high standard of neo-natal calf care will result in cows which convert feed more efficiently; i.e. produce the same quantity of milk for less feed.

Calves fed “high” levels of liquid feed have been demonstrated to be healthier, to have higher weight gains, better feed conversion rates and to exhibit more natural behaviours (which is an indicator of welfare status) than their limit fed peers.

Many years ago a large research herd began feeding its heifers high levels of nutrients, with the aim of doubling the calves’ birth weight by weaning. The lactation data from those heifers have been analyzed and factors affecting early life performance and later milk yield have been evaluated. This work and many other studies have shown that, in calves with adequate passive transfer, increased average daily gain (ADG) prior to weaning can result in a significant increase in lifetime milk production. An average of the results of 7 studies in which calves were fed ≥50% more nutrients than conventional feeding levels shows an increase in milk production of just under 800ℓ/lactation.

The benefits of increasing nutrient intake, growth rates and feed conversion efficiency (FCE) are:-

·         lowered cost per kg BW gain due to the high FCE in very young animals;

·         increased milk production;

·         potentially increased retention time in the herd;

·         increased feed efficiency throughout life;

·         reduced age at first calving or increased BW at first calving;

·         more high quality heifers for herd expansion or domestic or international sale.

How much milk?

A recent review of the influence milk feeding rates have on starter intake, weaning and later production levels concludes that calves can safely consume milk at ≈ 20% of body weight (40kg calf=8ℓ/day, 60kg calf=12ℓ), and greater milk consumption supports greater BW gain, improved feed efficiency, reduced incidence of disease, and greater opportunity to express natural behaviours, which in combination suggest improved welfare.

Even in the first few days of life, when traditionally calves lose weight, a higher level of nutrients can result in weight gain. In one trial newborn calves which were fed at ≈ 6ℓ/day gained >0.4kg/day while calves fed the more conventional 3ℓ/day lost >0.4kg/day over the first three days of life.

Calves given ad lib access to milk will drink >6ℓ milk/day even from day 1; this amount rises rapidly to 12-15ℓ/day. Limit fed calves (4ℓ/day) in one trial made 3.5 times as many visits to the automatic feeder than their ad lib fed peers. Unrewarded visits are a sign of hunger; therefore calves fed limited amounts of milk but ad lib access to grain are telling us that their welfare is compromised.

There is no question that if calves have access to high volumes of milk, starter intake is suppressed, with one trial showing ad lib fed calves ate 250g starter/day compared to their limit fed peers who ate ≈ 2.5kgs. The interesting fact is that despite a starter intake significantly less than the limit fed calves, the ad lib fed calves were 10 kgs heavier at 8 weeks of age, even though all calves were weaned at 5 weeks. This would suggest that there was very little, if any, post-weaning slump in the ad-lib fed calves.

Growth factors in milk may have other benefits such as enhancing the growth and maturation of the gastro-intestinal tract, but more research is required to understand the role of these factors.

Management plays a key role in the success or failure of accelerated feeding programmes. My own experience suggests that if things are done well, there are few downsides. As an example, several years ago I took over rearing heifer calves on a large dairy. Prior to my arrival the calf manager had been hauling out 4 -8 dead calves per day. I implemented a good colostrum programme and started feeding as much milk as calves wanted, twice a day. About 320 calves were born while I was there and of those only one was ever sick. Scours was not a problem and although there was not the capacity to weigh calves, they were visibly growing very fast. The age at which the calves started to eat grain was a little delayed but rearing costs were low because there were no veterinary expenses.

I would not advocate that all farmers go out and double the amount of milk they feed to their calves. On farms where management is sub-optimal, feeding more milk would just result in more calves with scours. If calf management is good, I suggest talking to your nutritional advisor about how to implement an accelerated feeding programme.