Analysis of lactating cows in commercial Austrian dairy farms: interrelationships between different efficiency and production traits, body condition score and energy balance

This study examines the relationship between efficiency, energy balance and related traits like milk yield, feed intake (DMI), body weight and body condition score (BCS). Data was derived in the project ‘Efficient Cow’ to develop efficiency traits for Austrian cattle breeding (6105 cows, 161 farms, one-year data collection). The following efficiency traits were considered: body weight efficiency as ratio between energy corrected milk (ECM) to metabolic body weight, feed efficiency (kg ECM per kg DMI) and energy efficiency expressed as ratio between energy in milk to energy intake. The higher the proportion of Red Holstein (RH) in Fleckvieh (FV), the more (efficiently) milk was produced, but also at the expenses of body fat reserves. The negative energy state of Holstein Friesian (HF) and the FV groups with highest RH proportion lasted approximately twice as long as of the least efficient Brown Swiss. All genotypes regained lost body tissue during whole lactation. The high yielding groups required a higher concentrate proportion in late lactation to regain body condition. In early lactation, high efficiency was accompanied by the loss of body weight and BCS. Body condition stagnated longer on the lowest level and was more conform to energy balance than body weight. In conclusion, high efficiency required an increasing partitioning of nutrients to milk yield inclusive mobilisation. Breeding for higher efficiency would exacerbate catabolic state including problems with health and fertility. This highlights the necessity of a broader definition of efficiency in cattle breeding involving parameters like BCS, health and fertility traits. HIGHLIGHTS In early lactation, high efficiency co-occurs with loss of body weight and body condition score Breeding for higher efficiency exacerbates body tissue mobilisation and negative energy balance A broader definition of efficiency involving parameters like body condition score, health and fertility traits is necessary in cattle breeding