Dairy Notes September 2010

During the dry period, a cow’s appetite will drop to 9-11kg dry matter (DM) per day.  This is not a problem as their energy requirement is relatively low at 90-100 MJ per day.  However, after calving energy requirement increases rapidly to over 250 MJ for a cow yielding 35 litres – intakes of over 20kg DM would be needed.  Until their intakes rise to this level, cows will have to milk off their backs.  If they lose too much weight in early lactation, this can lead to health and fertility problems.

To ensure cows achieve high intakes as soon as possible after calving, two areas of dry cow management need particular attention:

Condition Score is an indication of the amount of energy reserves stored by the cow. Managing cows to obtain the desired condition score at key stages of lactation is a major benefit to herd health, productivity and fertility.   Aim to dry cows off in roughly the same condition (CS 3) which they are expected to calve down in. Condition should be maintained or slightly improved during the dry period.

Condition score 3 – the target condition for cows at drying off.

It is more efficient to restore body condition during late lactation than during the dry period.  Monthly condition scoring of the herd will allow thin cows (CS <2.5) to be identified four to six weeks before drying off.  Feed levels can be increased by 2-4kg above milk yield requirements during this period to allow the animals to put on the necessary condition before drying off.  Where feasible these animals should be offered a 14-15 percent crude protein concentrate to encourage them to partition the extra energy intake to weight gain rather than just increasing yield.

Identify cows needing to put on condition in late lactation.

Drying cows off in target condition (CS 3) will ease management as there will be no need to run several groups (thin, fit and fat).  If cows are not at CS 3 at drying off, they should be managed accordingly. Fit and fat cows (>CS 2.5) should be put on a high fibre or restricted intake diet (straw/good quality silage or poor quality silage or stocked tightly at grass, that is, 10-12 cows per hectare) during the first two to three weeks of the dry period.

Thinner cows need to gain condition during the dry period. These animals should be fed on good grass or good quality silage to gain condition. Increasing the length of the dry period will give extra time for these cows to put on condition. Thin cows can be dried off for eight weeks rather than the usual six weeks, while first lactation heifers can be given ten weeks rather than the normal eight weeks.

Drying off to four weeks pre-calving

– as long as cows are in CS 3, bulky forages such as grazing and silage will meet their energy requirements and keep the rumen expanded.

Four weeks pre-calving

- pre-calver feeding of dry cows during the final month of pregnancy is routine practice in the Greenmount herd.  The cows are offered 1-2kg of a pre-calver designed to provide 250-300g of digestible undegradable protein (DUP) per day.

Seven days pre-calving

- it is essential to condition the rumen for high intake potential prior to the start of the next lactation. The structure of the rumen wall and microbial flora changes with the cow’s diet and must be prepared for the lactation ration.

At Greenmount cows are moved to a straw-bedded court five to seven days before calving. Here the cows are fed the same silage as the early lactation milking herd and offered small quantities (1-2kg) of the lactation concentrate. The aim is to minimise nutritional stress by allowing a gradual transition onto the lactating diet to achieve peak intake as early as possible during lactation.