Improve heifer growth by focusing on rumen

9 April 1999

Pre-calving care crucial to high milk production

Managing heifers and dry

cows better can help

improve milk production,

according to one US-based

dairy vet and nutritionist.

Rebecca Austin reports

THREE weeks pre and post-calving is the most important time to look after cows. It is over this period radical metabolic changes take place so cows must be fed correctly to ensure optimum calf growth, milk production and fertility, says Blaine Ellison, a vet and dairy nutrition consultant based in Wisconsin, USA.

Dr Ellison told a conference organised by Volac International near Bristol that a well managed dry cow herd is able to produce an extra 500kg-900kg of milk in the following lactation.

To ensure rapid growth in the last week of pregnancy the calf grows at a temperature which is a degree higher than the cows body. As a result, the cow requires 60% of its energy for heat production.

Unborn calves can only synthesise glucose and amino acids from their mothers blood stream. They cannot manage fats but use 46% glucose, 72% amino acids and 12% of the acetate in the cows blood.

When insufficient amino acids are available, the placenta increases in size, enabling it to process more blood, but the larger the placenta the more likely it is to be retained. Also, if the amount of amino acids available for absorption from a cows intake is too low she can develop ketosis and fatty liver.

"At the same time as the calfs nutrient requirements are increasing late in pregnancy, the cow is experiencing a 20% drop in dry matter intake during the last two weeks," said Dr Ellison.

"What you must remember is that a cow cannot eat more the day after she calves than the day before. It is therefore imperative to feed efficiently three weeks pre-calving, rather than just trying to get the cows to eat more after calving."

The key to this is condition score, he said. "There are not as many fat cows over here as in the US even though the genetics are just the same. Make sure your cows are at condition score 3.5 at drying off. Then they will not just be eating to survive.

"Once the score drops below three the cow will mobilise her own body protein to survive. This means she will have limited energy for breeding, fighting disease and milk production. And remember, it takes 60 days to produce an egg. At calving the cow is at her most stressed so if you can minimise that she is more likely to produce a healthy egg and hold to service."

Grass-based diets may be cheap but once digested this forage produces acetate which is unable to change the rumens environment in preparation for optimum milk production. Ideally, offer dry cows a good level of starch three weeks pre-calving. Nearer to calving cows require 10% less protein and energy than fed during lactation.

"The rumen papillae contract during the initial drying off period on a high forage diet," said Dr Ellison. "Although it is important the papillae get a chance to rest and renew they need to be adapted again to have the optimum absorptive area for the more concentrated diet they will be offered two weeks post-calving. In total it takes the papillae six weeks to mature so ensure 30% to 40% of this work is done pre-calving."

Calcium is also a vital part of the diet over this period. If blood calcium levels are low this is reflected in feed intake. Rectifying this will ensure a healthy population of bacterial flora in the rumen and hence a healthy cow. "A urine pH test below six suggests calcium deficiency. This test is like taking the cows temperature because if it is correct all systems in the body are working successfully," said Dr Ellison.

&#8226 Group cows and heifers together 21 days pre-calving.

&#8226 Provide adequate trough space – 0.6m/cow (2ft/cow).

&#8226 Keep feed troughs clean and fresh.

&#8226 Provide unlimited access to clean, fresh water.

&#8226 Exercise is important – allow adequate space.

&#8226 Cow comfort is crucial – straw yard, straw or mattress cubicles are recommended.

&#8226 Use individual maternity stalls when calving is imminent.

Improve heifer growth by focusing on rumen

Producers keen to ensure optimum heifer growth should concentrate on optimising the environment for the rumens flora.

By doing that it is possible to change the character of cow growth and hence increase height and length in the adult by 20%, said US specialist Blaine Ellison.

"The objective is volumetric growth," he said. "By changing the shape of the body and increasing the cows frame and spring of rib it is possible to change the shape of the rumen."

For example, a cow which is an inch taller than its peer will have an increased frame and 160 litres (35 gal) more body capacity at calving. Of that, 22% will be rumen which, in turn, allows for 22.7 litres (5 gal) more feed intake, leading to increased milk production. By second lactation there will be a 772kg (1700lb) milk production advantage.

Previously, cows were finished like beef animals so were heavier rather than stretchier. Dr Ellison said a shorter frame meant fewer secretion cells in the udder which restricted performance. Increasing the cows height to an optimum of 1.27m (50in) also enabled her to calve 60-90 days earlier.

He suggested weaning stock when they have been eating 1kg of hard food a day for at least three days. "It is not possible to make a cow bigger, but you can accelerate that growth at the right times.

"By definition a cow has reached mature size at 16 months. Weaning to breeding is the best time to grow your cow – especially when you realise that once she is 12-months-old rapid growth of her pelvic bones has shut down," he said. &#42

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