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Enhanced Feeding Program Research

Numerous studies, back as far as 1968, have examined the effects of feeding increased rates of milk or milk replacer to young calves. Recent developments in this area of heifer rearing have led to enhanced feeding programs. Conventional calf feeding offers milk replacer, of 18-22% protein and 15-22% fat, at approximately 500g/d. This can support approx. 400g/d live-weight gain (LWG). For dairy replacement heifers of high genetic potential, this is not sufficient to meet optimum growth potential. Recent studies have explored the responses to feeding a higher level of milk replacer (energy intake) with a change in milk replacer composition (protein concentration and energy source). While energy intake is the main driver of bodyweight gain, protein intake can influence both BWG and its composition. The strategy of lower intakes has typically been a management decision, not necessarily geared to growth potential. The new ‘enhanced’ growth program supports higher rates of feeding that are closer to ad lib feeding systems and thus could be more ‘biologically normal growth’. This growth is aimed at skeleton and muscle, resulting in tall heifers compared to fat heifers. Increasing the feeding rate of a milk replacer with adequate protein has pronounced effects on growth rate and feed efficiency. Barlett et al, Univ. of Illinois J.Dairy Sci. Vol.85, suppl. 1

Feed intake—–> 10%BW (conventional) 14%BW (Enhanced) 18%BW (ad lib)
MR intake kgDM/d 0.65 0.99 1.28
Av.gain g/d 360 700 1030
Gain: feed 0.55 0.71 0.81
Urea in plasma mg/dl 11.6 8.9 8.3

Using a 4,565 Mcal/kg milk replacer of 25% CP/ 17%fat with no calf starter for 5 week period Tikofsky et al., 2001– Body composition can be altered by the source of energy. High lactose/low fat concentrations in milk replacer favours lower fat deposition. Hill et al (2001) Substitution rate of milk replacer for dry starter feed is lower for high protein/low fat/high lactose milk replacers compared with conventional milk replacers. Cornell researchers concluded that, with higher protein levels, a minimum 15% fat could be adequate to maintain lean growth. However, allowances must be made for cold environment conditions. Too low a fat level reduces the stimulatory effect of fat on pancreatic enzyme secretion, so that protein digestion may be impaired. NRC 2001 – major change is to provide the foundation to think of calves as we have of older animals, in that nutrient requirements are not static but depend on desired rate of gain, body size and environment. The new NRC considers the approach that calf nutrition is dynamic, just as for older cattle. In other words, the product-orientated ‘one size fits all’ mentality of calf raising, (i.e. a single milk replacer formulation or feeding regime is assumed adequate for all calves) gives way to calculating requirements for growth and health and then designing diets to meet those requirements. Drackley (2001) 26% CP milk replacer maximized growth rate with minimal fat deposition. Research showed that whilst energy intake is the main driver of BWG, protein intake could influence both BWG and the composition of BWG. Drackley, (2000) identified three possible long-term effects of calf growth and development: milk production potential, metabolic imprinting and health and immune status. 18a Whole milk (Holstein) contains 29-30% fat and 25-26% protein on a dry solids basis. Diaz et al. (2001) -Using a 30% CP milk replacer showed, that as feeding level increased from 14 to 26 g milk replacer DM/kg bodyweight/day, bodyweight gain and fat content of gain increased but with no reduction in protein content of BW. 18b With the enhanced feeding program, the milk replacer is designed to meet the correct nutrient balance for high growth rates and intakes in heifers, resulting in taller and well-proportioned heifers that can enter the milk herd earlier and have a higher milk production potential. Foldager et al, 1997, 48th EAAP Annual Meeting. Calf Milk Intake and Lactation Yield (Post weaning growth: 0.55 to 0.65kg/d to calving)

Conventional Enhanced Maternal
Gain (g/d) (0-42d) 650 960 850
Calving weight (kg) 496 491 509
Energy corrected milk kg/d 25.5 27.1 27.3
305d difference (kg) 488 549

The concept is to feed heifers to attain a pre-selected or target weight at a given age to achieve optimum first lactation performance while controlling the costs of rearing replacements. Gaining benefit from enhanced early nutrition requires integration with the entire heifer-rearing program.

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