Grazing season and forage type influence goat milk composition and rennet coagulation properties

Two different types of pasture (cultivated and rangeland) and 2 different hay qualities (high and low quality) were examined for their effects on goat milk composition and rennet coagulation properties. Furthermore, the effect of dietary treatments in both the early and late grazing season was studied. As lactation stage is known to influence milk composition, the goats in the early and late grazing season were in the same lactation stage at the start of the experiment. The milk composition was influenced both by dietary treatment and season. Milk from goats on pasture was superior to those on hay by containing a higher content of protein and casein, and the goats on cultivated pasture had the highest milk yield. Casein composition was significantly influenced by forage treatment. Goats grazing on cultivated pasture had higher contents of αs1-casein and also of κ-casein compared with the other treatments, whereas goats grazing on rangeland had the highest content of β-casein. Factors such as milk yield, casein micelle size, αs2-casein, and calcium content were reduced in late compared with early season. More favorable rennet coagulation properties were achieved in milk from the early grazing season, with shorter firming time and higher curd firmness compared with milk from the late grazing season, but the firming time and curd firmness were not prominently influenced by forage treatment. The content of αs2-casein and calcium in the milk affected the firming time and the curd firmness positively. The influence of season and forage treatment on especially milk yield, casein content, and rennet coagulation properties is of economic importance for both the dairy industry and goat milk farmers

Feeding a concentrate rich in rapeseed oil improves fatty acid composition and flavor in Norwegian goat milk

Impaired quality due to a high content of free fatty acids (FFA) and off-flavors has caused challenges in the development of Norwegian goat milk products. The present study aimed to examine the effect of lipid-supplemented concentrates on milk fat content, fatty acid composition, FFA, lipoprotein lipase activity, sensory properties, and size of milk fat globules of goat milk. Thirty goats assigned to 3 experimental groups were fed different concentrates from 60 d in milk (DIM) until late lactation (230 DIM). The diets were (1) control concentrate (no added fat); (2) control concentrate with 8% (added on air-dry basis) hydrogenated palm oil enriched with palmitic acid (POFA); and (3) control concentrate with 8% (added on air-dry basis) rapeseed oil (RSO). The POFA group produced milk with the highest fat content, and fat content was positively correlated with the mean size of milk fat globules. Goats in the RSO group had a higher content of long-chain and unsaturated fatty acids, whereas milk from goats in the POFA group had a higher content of palmitic and palmitoleic acids (C16:0 and C16:1 cis). The control group produced milk with a higher content of short-, medium-, odd-, and branched-chain fatty acids compared with the 2 other groups. The content of FFA in milk was low in early and late lactation and peaked in mid lactation (90 DIM). A high content of FFA was correlated with poor sensory properties (tart/rancid flavor). The RSO group produced milk with lower content of FFA and off-flavors in mid lactation and a higher proportion of unsaturated fatty acids. Therefore, replacement of palm oil with rapeseed oil as a lipid source in dairy goat feed would be favorable