Fatty Acid Composition of Dairy Milk: A Case Study Comparing Once- and Twice-a-Day Milking of Pasture-Fed Cows at Different Stages of Lactation

Abstract

In this case study, we compared the gross composition and fatty acid (FA) composition of milk from cows milked once a day (OAD) and twice a day (TAD) at different stages of lactation in real farm conditions with no control on feed. Seventy-two cows from a OAD milking herd and 181 cows from a TAD milking herd were sampled in early, mid and late lactation. Calibration equations were developed to enable the prediction of proportions of individual FAs using mid-infrared (MIR) spectroscopy. Cows milked OAD produced 25% lower daily milk yield (MY) compared to cows milked TAD. Percentages of fat and protein were 21% and 9% higher in cows milked OAD compared to cows milked TAD, respectively. The proportion of saturated fatty acids (SFA) (molecules with unbranched hydrocarbon chains and all single bonds) was significantly lower, while the proportions of de novo synthesised FAs from C8:0 to C14:0 were significantly higher, in cows milked OAD compared to cows milked TAD. OAD milking improved the energy balance of cows, which led to higher proportions of de novo synthesised FAs and lower proportions of long-chain fatty acids (16:0 and above). The proportion of SFA was significantly higher in mid lactation (ML) compared to early lactation (EL) and late lactation (LL) in cows milked OAD and TAD. In EL, the proportions of C4:0 to C12:0 FAs in cows milked OAD were significantly higher compared to the cows milked TAD due to the improved energy status of cows milked OAD. Understanding the proportions of individual FAs in cows milked OAD and TAD will enable further studies on milk fat characteristics and on butter hardness and coagulation properties of milk.

Association of Single Nucleotide Polymorphism in the DGAT1 Gene with the Fatty Acid Composition of Cows Milked Once and Twice a Day

“…Similarly, the proportions of de novo synthesis fatty acids, mainly C6:0–C14:0, were higher, and proportions of long-chain fatty acids were lower in cows milked OAD for all three genotypes compared to cows milked TAD. Similar results were reported by Sanjayaranj et al [ 39 ] in the previous work comparing fatty acid composition between cows milked OAD and TAD.…”

The impacts of milking frequency on nutrient composition and functional characteristics of Cheddar cheese

“…No significant differences in free fatty acid (FFA) profile were observed between OAD and TAD cheese at 180 days of maturation (Table 5). This result provides an interesting comparison with work already completed on FFAs and milking frequency, (Sanjayaranj et al 2022).…”

“…Most notably, Sanjayaranj et al (2022) observed differences in saturated fatty acid and de novo synthesised fatty acids between OAD and TAD, but it is essential to recognise that animal diet was not controlled within that work; indeed animal diet has already been shown to impact FFA profile in dairy products (O'Callaghan et al 2017). Within the experimental design for this research OAD and TAD, animals were all grazed on perennial ryegrass pastures and offered diets of similar quality to control this potentially confounding variable (Murphy et al 2023).…”

“…Positive animal health impacts have also been observed with OAD practises. Fertility and reproductive health have been reported as being positively impacted by OAD milking (Dalley et al 2007;O'Brien et al 2009), and animals milked OAD have shown better body condition scores (Sanjayaranj et al 2022).…”

“…The greatest known impact is on fat and protein contents, and these have repeatedly been shown to increase in percentage terms with OAD strategies (R emond et al 2004;Boyle et al 2005;O'Brien et al 2009), but, not sufficiently to compensate for, and be explained by, the lower overall milk volume (Clark et al 2006). Some investigations have suggested that fat and protein profiles are not altered with milking frequency (Bobe et al 2007), but other research has found lower saturated fatty acids within milk obtained from cows milked OAD (Sanjayaranj et al 2022). Such compositional changes can impact dairy product quality (Stelwagen et al 2013).…”