Breeders in Southern Queensland and New England
Maximising weaning rates is key to profitability. Managing nutrition prior to and during gestation, as well as during lactation will improve fertility. Cows have around 80 days in which to become pregnant if they are to calve again within 12 months.
If too much body condition is lost in the time between pregnancy and weaning, cows will take longer to start cycling again after calving. In late pregnancy and when feeding a calf, a cow’s nutritional demands are greatly increased, particularly for energy, protein and phosphorus. However the presence of a large calf makes it difficult for the cow to consume enough pasture to meet these requirements. This problem is exacerbated if cows are consuming maturing or dry pasture.
Lactating cows need to consume 35% more on a live-weight basis than non-pregnant, dry cows. If milk production is limited by poor nutrition, this can have a negative impact on the growth rate of the calf. A severe growth restriction of calves prior to 250kg liveweight can have long term negative impacts on future growth, development and production capacity.
Live weight and body condition are two of the key determinants influencing the onset of puberty and conception rates in heifers.
The greatest demand for phosphorus is in the last three months of pregnancy and during lactation. Reserves of calcium and phosphorus can be built during periods of positive weight gain and used during times of peak demand; without supplementation first calf cows raised on low phosphorus soils will have inadequate reserves, which will reduce milk production and delay breeding.