Effect of dietary palmitic acid supplementation and milking frequency: 2. Butter manufacture and properties.

Dietary palmitic acid (PA) supplementation promotes fat yield, whereas increased milking frequency (MF) enhances milk yield. Such practices can be useful at the farm level, but their effects on milk processing remain to be determined. The objective of this study was to evaluate the effects of dietary PA supplementation and increased MF from 2 times to 3 times daily on butter manufacture and properties. In a duplicated 4 × 4 Latin square design, with a 2 × 2 factorial arrangement of treatments, 8 Holstein cows received a diet with or without PA (2% or 0%, on a DM basis) and were milked 2 times or 3 times daily. For each period, after 18 d of treatment adaptation, milk was collected from each cow for 2 d, and pooled by treatment before butter manufacture. Milk free fatty acids (FA) concentration and casein micelle size were similar between treatments, as well as cream fat globule diameter and butter yield. There was a significant interaction between PA and MF on churning time. With the nonsupplemented diets, 3 times daily milking increased churning time, and with 2 times daily milking, PA supplementation also increased churning time. Butter FA composition was mostly affected by PA, whereas MF had a limited effect. Total 16 C FA concentration in butter was increased with dietary PA at the expense of short-chain FA (6-14 C) and, to a lesser extent, long-chain FA (≥18 C). Dietary PA increased butter hardness at 20°C, whereas this effect was limited to a tendency when measured at 4°C. Resistance to spreadability increased with PA at both 4°C and 20°C. Overall, the effects of PA on butter texture were less pronounced at 4°C than at 20°C. Milking frequency had no effect on butter texture. Butter melting point was greater with PA and was positively correlated with the concentration in 16:0 and the spreadability index (cis-9 18:1/16:0). The solid fat content of butter was similar between PA and non-PA treatments at 5, 8, and 20°C. However, from 30°C, the solid fat content was higher with the PA diet. The spreadability index was correlated with butter hardness, and to a greater extent, with butter spreadability. This work underscores how dairy farm management influences the technological properties of milk, with potential implications for butter manufacturing and quality.