Research data and practical experience, from New Zealand and around the world, has shown that youngstock rearers have the opportunity to positively influence lifetime productivity of calves, kids and lambs, simply by feeding them well in the first eight weeks of life.
For many years calf rearing systems have focused primarily on developing the rumen of the young calf so that by the time the calf is weaned it is able to effectively utilise pasture and other forages, and in many cases maximising rumen development has been interpreted as minimising the amount of milk consumed by the calf to ensure high intakes of starch-based feed needed to help drive the development of rumen papillae.
Effect of early life nutrition on mammary gland and mammary parenchyma weight at 54 days of age
While important, this focus on rumen development has unfortunately distracted us from developing other key organs essential for improved animal health and welfare and optimised lifetime productivity.
To understand how early life nutrition may impact lifetime productivity in dairy heifers, researchers at Cornell University investigated the effect of increased milk feeding on the development of key organs, including the mammary gland, in the first 8 weeks of a calf’s life.
These researchers fed calves that weighed 39 kg at birth an average of 600 g per day (control) or 1300 g per day (enhanced) of milk replacer and found that calves fed the higher levels of milk replacer gained 820 g per day compared to control calves which only gained 390 g per day.
The researchers also reported a significant difference in the weight of the whole mammary gland and amount of mammary parenchyma (or milk-producing tissue) present at 54 days of age, with calves on the enhanced feeding programme having six times the parenchyma tissue of those calves fed the control treatment.
Similar results also reported in New Zealand where calves were fed either 4 L or 8 L of whole milk from 10 to 73 days of age and were weaned gradually by 84 days of age.
In addition to increased mammary parenchyma the researchers also reported other benefits relevant to both heifer or hogget replacements and those animals reared for meat. These include:
- enhanced preweaning growth with no negative effect on post-weaning growth on pasture and earlier development of the immune system supporting a more effective immune response.
The relationship between body weight at 3, 6, 9, 12, 15, 18 and 21 months of age and energy corrected milk yield in first lacatation Holstein-Friesian-Jersey crossbred dairy heifers
An extensive review of rearing and production data from more than 140,000 spring-born heifers from over 1,300 herds in New Zealand reinforces these findings with researchers reporting a strong positive correlation between first lactation milk production and body weight between 3 and 21 months of age regardless of breed.
Importantly these researchers also showed a strong positive correlation between body weight during rearing and milk production through to third lactation, with this increased productivity combined with improved cow survival all contributing to improved farm profitability.
Improved early life nutrition has also been shown to have positive benefits for beef animals, with a separate study in New Zealand where researchers fed one group of dairy beef calves a low milk allowance of 4 L per calf per day with weaning at 7 weeks of age and a second group a high milk allowance of 8 L per calf per day with weaning at 12 weeks of age, and at 12 weeks of age the calves fed the high milk allowance were 6.9 kg heavier than the calves fed the low milk allowance and the impact of this increase in growth was sustained until 19 months of age.
In addition, those calves on the high milk allowances reached slaughter weight sooner and had higher marbling scores, with steaks showing less cook loss and better colour stability.
It is clear that the effects of early life nutrition have a positive impact on the lifetime productivity of an animal; supporting increased first lactation milk, fat and protein production in dairy replacements (calves, kids or lambs) and lean tissue development and feed efficiency in those animals reared for meat production.
References
Soberon and Van Amburgh, 2017. Effects of preweaning nutrient intake in the developing mammary parenchymal tissue. Journal of Dairy Science, 100, 6.
Khan et al., 2022. Growth performance, antibody response and mammary gland development in New Zealand dairy replacement bovine heifers fed high or low amounts of unpasteurized whole milk. Journal of Animal Science, 100, 10.
Handcock et al., 2018. Positive relationships between body weight of dairy heifers and their first lactation and accumulated three-parity lactation production. Journal of Dairy Science, 102, 5.
Burggraaf et al., 2020. Effect of rearing diet and early post-weaning pasture quality on the life-time growth, meat quality, carcass traits and environmental impact of dairy-beef cattle. Livestock Science, 239, 10431.