Improving the production efficiency of dairy systems
14 May 2021
By Lucy Ross
Take home message: Dairy cow performance is highly influential and requires a multifactorial approach, combining both genetic and environmental factors, to optimise productivity.
Improving the production efficiency of dairy systems offers economic and environmental incentives to industry. There is growing popularity towards using genomic selection to improve feed intakes and efficiency; cows that require less dry matter than predicted for a given production output are regarded as more efficient. Genomic selection has increased milk production, but at the cost of poor fertility and health. Using a multifaceted approach, this study aimed to determine the effect of genotype, feeding system, parity, and time of year on key performance data.
The study collected data from 245 lactating Holstein-Friesian dairy cows, managed in an all-year-round calving, continually-housed system, during the 31 day period of July 2017 (n=119) and January 2018 (n=146). Cows were ranked, based on their sire’s predicted transmitting ability for kg milk fat plus kg crude protein, as high ‘Select’ (S) or average ‘Control’ (C) genetic merit, and fed a diet of either Standard Energy (SE) or High Energy (HE), resulting in a 2 x 2 factorial experiment (SEC, SES, HEC and HES). Cow performance data (dry matter intake, milk yield, live weight, body condition and locomotion) were analysed according to genotype (C and S), feeding system (SE or HE), the interaction between genotype and feeding system (GxF), parity (1, 2, 3 and ≥4) and month (July 2017 and January 2018)
Cows of high genetic merit had significantly greater dry matter intakes than those of average genetic merit and, as expected, produced greater yields as selection based on high yield potential will simultaneously increase dry matter intake. These cows could allocate a greater proportion of energy towards milk production, however, at the expense of tissue deposition, which resulted in lower body condition scores. Conversely, milk yield was more influenced by feeding system wherein cows fed a HE diet produced the greatest yields. This suggests that ration composition is of topmost importance when evaluating cow performance in terms of production. Cows of poorer locomotion were found to be of higher parity and yield. This was thought to be due to the increased demand on the body from greater milk yields and lower body condition, seen in mature cows. There was a correlation between GxF and locomotion however, since there was no effect of genotype, it was suggested that environmental factors, including ration composition, influenced the incidence of lameness. Lastly, due to the sizeable breadth of this study and its limitations, time of year was not discussed extensively but was thought to have little effect due to the moderate conditions of all-year-round housing.
To conclude, this study found that genetic merit had the greatest influence on dry matter intake whereas feeding system was more influential on milk yield. Ultimately, considering all factors is key in optimising cow performance.
This study was carried out by Inga Barnett, an Applied Animal Science undergraduate at SRUC and The University of Glasgow. She comments, “Now that I have completed my undergraduate degree, I hope to find an opportunity within the agriculture sector to apply and develop my knowledge gained through university study”. Inga is interested in ruminant nutrition and livestock production, and would like to specialise in these areas.
Lucy Ross, PhD student, University of Nottingham
Lucy Ross has been a member of the BSAS Early Careers Council for two years. She is in the final year of her PhD at Nottingham, researching heifer rearing and whole-farm feed efficiency in UK dairy systems.