The effects of parity and lactation stage on milk composition and methane production in Holstein–Friesian cows

Background Dairy animals produce milk, a critical food component for food security worldwide; however, the processes leading to this high‐quality food can lead to nutritional and environmental consequences. The determination of enteric methane production in semi‐intensive dairy animals is difficult; hence, no invasive methods can be informative. Aim(s) The study aimed to determine the effects of parity and lactation stage on dry matter intake (DMI), milk yield, milk quality parameters (butter fat, protein, total solids (TS), solid not fat (SNF) and lactose) and methane production from Holstein dairy cows. Methods Eighteen cows were assigned in a two parity (first and second calvers P1, and mature cows P2) by three lactation stages (early lactation (EL), mid‐lactation (ML) and late‐lactation (LL) factorial arrangement in a complete randomised design (CRD)). Correlations among milk components were determined, while proxy methods were used to predict enteric methane production. Milk samples were collected twice per day during morning (0600 h) and afternoon (1400 h) milking and were analysed using a milk analyser. Major Findings The DMI was affected ( P < 0.05) by lactation stage and parity. The stage of lactation affected ( P < 0.05) milk fat content and total milk solids, while parity had no effect ( P > 0.05). The fat content of the milk was higher ( P < 0.05) in ML and LL than in EL. Negative correlations ( P < 0.05) were observed between butter fat and protein, lactose and SNF, and TS with lactose and SNF. Positive and significant correlations ( P < 0.05) were observed between DMI and milk yield, protein and SNF, protein and lactose, fat and TS, and lactose and SNF. Parity and stage of lactation influenced ( P < 0.05) enteric methane production, which ranged from 134.37 to 202.43 MJ/day. Implications This study showed that different lactation stages affect milk yield and milk components, while parity only affects milk quality; both affect enteric methane production.