Milk characteristics and cheese yield of Holsteins and 3-breed rotational (ProCross) crossbred cows

Interest in crossbreeding of dairy cattle has grown in commercial dairy farm to improve the fertility, health and longevity respect to purebred Holstein (HO). Conversely, information on milk properties important for rennet behaviour, such as the size of fat globule and casein micelle, and on cheese yield properties of milk from crossbred (CROSS) cows are sparse. The aim of the present study (University of Padova, BIRD188213) was to investigate the effects of 3 breed rotational cross breeding (ProCross) of Holstein (HO) with sires of Viking Red in first (F1: VR×HO), Montbéliarde in second (F2: MO×F1), HO in third (F3: HO×F2) and again VR in fourth generation (F4: VR×F3) on milk characteristics and cheese yield (CY). Evening milk samples (n=102, 2,000 ml/cow) were collected from multiparous HO (n=33) and CROSS (n=69: 17 F1, 18 F2, 17 F3, 17 F4) cows reared in a commercial farm located in Northern Italy. Individual milk samples were assessed for milk composition, fat globule and casein micelle size and processed through a laboratory model-cheese manufacturing procedure to determine CY. Data were analysed using a linear mixed model including the random effect of date of sampling (5 dates) and the fixed effect of breed combination. Compared to HO, CROSS cows yielded 10% less milk, but showed increased protein and casein content (+3% and +6%, respectively) and lower SCS (2.53 vs 3.35). Milk from CROSS cows showed smaller average casein micelle size (131.0 vs 133.4 nm, P<0.01), and smaller volume-surface average diameter (d3,2: 3.23 vs 3.41 μm, P=0.02) and volume-weighted average diameter (d4,3: 3.76 vs 3.93 μm, P=0.10) of fat globules than HO cows. CY averaged 17.7% and was comparable for milk from HO and CROSS cows, likewise the proportion of solids and water in the curd and the recovery of nutrients from milk to curd. In conclusion, when compared to that from HO, milk from CROSS cows showed some advantages for milk quality and fat globule and casein micelle size, without alteration of CY. The trial is in progress to increase cow sample size.