Systems of management of beef cows in the hills and uplands seek to make use of the cow's ability to utilise body tissue to maintain production during periods of undernutrition in winter and to replenish body reserves from relatively inexpensive summer grazing.
In spring-calving cows, the periods of winter undernutrition occur during late pregnancy and the early months of lactation. On upland farms, cows with adequate body reserves (condition score 3.5) at the beginning of winter, fed less than 50 MJ ME per day during the final 3 months of gestation and 70 MJ ME per day during the first 2 months of lactation, will lose about 1.5 units of body condition but such a regime will not necessarily result in biologically significant production penalties. Fertilised ryegrass swards maintained at 8 cm sward surface height during the grazing season will support levels of milk production of around 11 kg per day, calf growth rates of the order of 1.2 kg per day and allow full recovery of cow body weight and condition. In hill herds, the magnitude of losses in weight and condition over winter must be restricted to the extent of the recovery which the quality of summer grazing will support.
Similar considerations apply in autumn-calving herds, where the greater part or all of lactation coincides with the period of winter feeding. Cows calving at a body condition score of 3.0 can be fed 75 MJ ME per day from before to one month after mating without prejudicing reproductive performance, and 60-65 MJ ME per day from then until turnout. Where good quality pasture is available, milk production will increase from around 5 to more than 9 kg per day following turnout, calf performance will be enhanced by delaying weaning and cows will recover in full the weight and condition lost during winter. In the hill situation, calves may require to be weaned at turnout if full cow recovery is to be achieved.
Studies on the nutrition of the weaned suckled calf indicate that a policy of feeding weaned calves inexpensively during winter to gain between 0.3 and 0.5 kg per day may constitute a viable alternative to the traditional practice of selling calves in the autumn. Such animals will achieve significantly higher growth rates at pasture in the following summer than calves fed more generously and gaining weight more rapidly during winter.
On some hill farms where opportunities for the conservation of winter fodder are limited but where there is plentiful summer grazing, a system of June calving followed by a short lactation, and in which calves are only very moderately fed over winter, merits consideration.
The areas in which further research is most urgently required to effect significant improvements in efficiency are those concerned with the relationship between nutrition and reproductive efficiency and the induction of twinning in cows.