Heifer rearing myths

Published 5 April 10

It's a commonly held belief that heifers which calve too young will not stand up to the rigours of milk production in the dairy herd.

But their age really isn't the question, according to independent nutritionist, Pete Kelly.

"The aim should be to get heifers into the herd young, which does not mean getting them into the herd small," he says.

Attention should be firmly focused on optimising growth rates throughout the rearing period, so ensuring that heifers are mature and well-grown by the time of calving - and this should ideally be at 24 months.

"Talk about growing heifers too fast has turned out to be nonsense," insisted Mr Kelly, speaking at the DairyCo meetings. "There's no evidence that rapid weight gain reduces the development of cells in the udder - which is a commonly held misconception that's prevailed in the past.

"Trials have shown that there is no problem growing Holstein heifers at 1kg/day, for at least part of the rearing period."

And although recognising that younger heifers may give a little less milk in their first lactation, he said they should peak far later - as secretory tissue continued to develop after calving - give far greater lifetime milk production, and have fewer lifelong problems.

Early growth

The objective of achieving good growth rates should begin from day one, when a plentiful intake of quality colostrum is the essential first step. This means ensuring colostrum is consumed within the first six hours of life, and getting at least four litres into the calf within 24 hours.

"If the first feed is a good one, the immunity the calf gets from the colostrum is so much better," he said. "So use a bottle or stomach tube if the calf hasn't sucked within 15 minutes."

Recommending the bottle over the tube, he observed that the feeding process was more natural for the calf and directed the milk straight to its abomasum, which is where it was required, rather than via a tube, which had more risk of being mis-directed.

"But colostrum can provide antibodies for six weeks," added Mr Kelly, observing that although these antibodies could not be absorbed through the gut wall and into the bloodstream after 24 hours, they still had a role in digestive health, which was important in the fight against enteric pathogens such as Rotavirus.

Once the calf has moved on to milk powder, a further misconception - that too much milk would cause it to scour - was discussed.

"Too much milk can make calves loose but it won't make them scour - this is caused by infection," said Mr Kelly.

Suggesting that typical calf rearing systems were often 'starving the calf', he added: "The only animal whose feed we restrict is the calf."

Observing that a calf typically consumed 10 percent of its bodyweight (which for a 45kg calf meant 4.5 litres of liquid), and a 10 percent concentration of powder (totalling 450g of powder per day for a calf of the same size), he said this was insufficient.

Increasing this to 12.5 percent of bodyweight (around six litres) and a 15 percent concentration of powder would 'allow for the maximum growth rate when the calf is biologically most efficient' and increase its powder consumption to 825g.

This would make a miniscule difference to the overall heifer rearing costs, which totalled between £900 and £1200, depending on age at calving.

In fact, the feed conversion efficiency of the calf should be exploited at this young age, when higher feed intakes could dramatically increase growth rates, while a lack of growth at an early stage could not be compensated for later.

A coarse mix rather than pellets for calves aged up to 12 weeks was said to be preferable, as this would result in higher intakes and better rumen development.

"If you can get a good calf at three months old you are almost home and dry," said Mr Kelly.

Weaning to puberty

After weaning, rapid growth should continue to be the target, 'provided the heifers are not getting fat'.

"Frame growth is critical at this time as around 75 to 80 percent of it occurs before the animal is 12 months old," he said.

"This is why you should always feed concentrates to heifers at grass," he added. "If there's plenty of grass, this may be as little as 0.5kg/day but it's an important management tool, so worth continuing and you can easily increase the feed rate during spells of bad weather.

"Even if you feed 1kg/day of concentrates though the summer, it's hardly going to cost you more than £25/head - again that's nothing in terms of the overall rearing cost."

Feeding at service

Just before service, energy intake should be stepped up which could be through additional forage such as maize silage, concentrates or good quality grazing.

"Continuing this for two to three weeks before service and around six weeks after will improve conception rates," said Mr Kelly, "although once she is pregnant, you'll need to carefully watch the heifer's condition."

Suggesting her size and suitability for bulling could most quickly and easily be assessed by measuring the heifer at the withers with a stick or a 'line on the wall', he said that a table of targets - available for a variety of breeds in the DairyCo feeding+ folder - should be used as a reference (see table 1).

Table 1: Heifer height and weight targets for the main dairy breeds

 

Holstein

Friesian

Jersey

Age

(months)

Weight

(kg)

Withers height

(cm)

Weight

(kg)

Withers height

(cm)

Weight

(kg)

Withers height

(cm)

2

76

87

72

84

55

78

4

127

96

120

93

95

89

6

180

104

162

100

130

94

12

340

124

285

118

220

109

15

420

129

350

122

265

114

18

490

133

405

130

305

119

21

545

137

470

132

355

120

24 (pre calving)

636

140

535

134

395

122

24 (post calving)

568

140

485

134

350

122

 

Excess condition - which was far more likely to occur in older heifers - would increase calving problems; reduce feed intake after calving; increase fatty liver and ketosis; and reduce subsequent fertility.

"Even in older heifers you don't want to have more than a condition score 3," he said. "And this means no wrinkles of fat at the top of the tail."

The optimum age at first calving he said was 'as young as possible provided they can reach the right size', which, for most British herds, should be around two years.

"But if they are on an extensive system or are grazing rough pasture, this may be a little older, but it should certainly be by 27 months, or perhaps 28 or 29 under organic systems if inputs are restricted."  

 

Box

Heifer rearing key points

  • Calve early to minimise rearing cost and increase yield per year of life.
  • Grow heifers as fast as possible without getting them fat.
  • Consider improving calf feeding while on milk.
  • Monitor withers height and body condition.

 

 

Panel:

The economics of two year calving

The economic arguments for two year calving were put by Chris Coxon from DairyCo, who said that the cost to a farm of replacement heifers was mainly driven by age at first calving and culling rate.

Failure to control both of these factors led some farmers to rear heifers for as long as they milked them, placing a heavy financial burden on the farm.

Both factors also affected the number of youngstock needed on the farm, which could be 50 percent more with just small differences in age at first calving and replacement rate. This is seen in the difference between a 23 percent replacement rate and 24 month calving (48 animals needed) and a 29 percent replacement rate and 28 month calving (71 animals needed) (see table 2).

Table 2: Number of youngstock required for a milking herd of 100 head

 

Herd replacement rate (%)

(5% calf mortality)

Age at first calving (months)

17

20

23

26

29

32

35

22

33

39

44

50

56

62

67

24

36

42

48

55

61

67

74

26

39

46

52

59

66

73

80

28

42

49

56

64

71

78

86

30

45

53

60

68

76

84

92

 

 

"Rearing costs to the point of calving will also vary from farm to farm, but tend to average around £900 for 25 month calving and £950 for 28 month calving - and this is before overhead costs such as buildings and machinery are taken into account," said Mr Coxon. "Then this has to be multiplied up to account for the number of youngstock needed as replacements."

The two factors of replacement rate and age at first calving also had a significant bearing on the amount of milk produced per cow per year of life, which was an important performance indicator, and varied between 3243 litres in the worst performing herds and 8014 litres in the best.

Added to this was compelling production and fertility data from recent DairyCo research into reducing heifer wastage in the dairy herd, which highlighted a wide range of performance figures, according to age at first calving (see table 3).

Table 3: Heifer production and fertility performance at a range of calving ages

Calving age (months)

22-23

24-25

26-28

32-36

Pre-calving weight (kg)

591

621

625

769

Calving Assistance (%)

17%

17%

27%

67%

Weight loss post calving (kg)

32

26

6

59

Cows still alive at 5 years (%)

86%

62%

41%

33%

Total 5 year milk yield (kg)

25,031

20,395

16,671

8,029

Time in milk during first 5 years (%)

48%

42%

38%

18%

 

To ensure a herd was not slipping into the poorer performing categories, Mr Coxon said performance should be closely monitored, targets should be set, and costs should be known.

The DairyCo heifer rearing calculator which assesses the costs for an individual herd is available free of charge through the DairyCo website at www.dairyco.org.uk or can be sent on CD by calling 02476 478695.