In cattle, puberty is ascertained by liveweight or body size, rather than a fixed age. Increasing the plane of nutrition in young cattle is aimed at reaching puberty, or rather a set body weight/size, while the animal is still relatively young (12 to 20 months of age). With the tendency to join heifers while they are still young, the demands of reproductive processes and pregnancy are added to those for growth. With this in mind, there are important factors to consider when assessing the nutrient requirements for maiden and first calf heifers.
Firstly, reproductive processes are often not the only productive stage the heifer is regulating. Females being joined at a young age, whom often are only half of their mature body weight, are still actively growing while being expected to conceive and grow a calf. She is then be expected to be in calf again 2-3 months following her first calving, whilst producing large quantities of milk. Secondly, nutritional requirements vary at different stages of pregnancy. Protein for example is required in smaller amounts for foetal development at the beginning stages of pregnancy versus the later stages where protein levels for foetal development dramatically increase.
The success of conception rates in maiden and first calf heifers are significantly improved with an increase in body weight at joining (figure 1). In order to reach the targeted body weight for joining, the implementation of improved nutrition is a dependent factor. Maintaining a certain standard of nutrition is also crucial when striving for first calf heifers to cycle and re-conceive following their first calving. This is impending on their body condition at calving with consideration of their lactation status. Success in reaching a set joining body weight, conception and re-conception rates, with consideration of the production status of young heifers with their growth and lactation during these productive processes, infers that undernutrition or a limiting nutrient can severely impede on any of these processes being achieved. Timing of all management practices such as weaning, joining and calving is crucial in order to be able to plan at what time of year each practice should be occurring to achieve the best outcome (e.g., calving in the wet seasons) and at what point should nutritional support be provided to maintain the projected target/s (e.g., supplements during dry seasons).
The body condition at calving has the biggest effect on subsequent re-conception rates in first calf heifers (figure 2). Cows need to have greater body reserves to re-initiate cycling. The quantity and quality of pasture and nutrients can be limiting throughout the dry seasons of different regions of Australia.
Figure 2: Effect of body weight on re-conception rates in lactating first calf heifers (Schatz, 2011).
Heifers in a poorer body condition during lactation, increases the amount of time it takes to cycle again. When body stores of fat in a heifer are inadequate, the hormones required to initiate cycles cannot be secreted, thus extending the time it takes for cycling to resume. In addition to limiting fat stores, a deficiency in a specific nutrient can also interfere with the synthesis of hormones involved in reproduction. The lack of production of the luteinising hormone whose role is in the maturation and release of oocytes (the process of ovulation), due to a low plane of nutrition reduces the frequency this hormone is release, resulting in their heifer not cycling.
With heifers experiencing these limitations during pregnancy and leading up to calving, providing supplementation will be beneficial to increase their body condition prior to calving to thus increase the chances of re-conception. Attempting to improve body condition after calving is highly unlikely as much of the energy obtained from feed and body reserves goes into lactation. This does not imply that supplementing after calving is not necessary, as regions experiencing large deficits in pasture and nutrients should continue to supplement to ensure a source of energy (carbohydrates) and protein (urea) is being provided to producing mothers.
Every mineral has a role in maintaining the proper functioning of productive processes in cattle. For producers to have the knowledge and understanding of what elements are deficient in their area, enables the implementation of preventative methods for the projected nutritional deficiencies during specific seasons or known deficient pastures. One of the most commonly deficient elements, with a critical role in the efficient functioning of cattle is Phosphorus. Deficiencies in this element can impact on an animal’s bone formation, feed intake, milk yield, growth, liveweight gains, oestrus cycles and fertility. Supplementation of Phosphorus during deficient seasons or pastures can prevent the development of mineral deficiencies with their consequential syndromes. uPRO ORANGE and uPRO GREEN are two soluble supplements designed by DIT AgTech that provide important elements in bovine nutrition. These elements include protein, urea, phosphorus and sulphur. The concentration of these constituents between the two supplements varies slightly to enable the administration of the most appropriate product for a producers situation.
References
McDonald, P., Edwards, R. A., Greenhalgh, J. F., Morgan, C. A., Sinclair, L. A., & Wilkinson, R. G. (2011). Animal Nutrition Seventh Edition . Harlow : Pearson.
Savage, D. (2005). Nutritional influences on beef breeding performance . Sydney: Meat and Livestock Australia Limited .
Schatz, T. (2010). Understanding and improving heifer fertility in the Northern Territory . Sydney: Meat and Livestock Australia Limited .
Schatz, T. (2011). Industry initiatives to improve young breeder performance in the Northern Territory . Sydney : Meat and Livestock Australia Limited .
