Kid suckling versus artificial rearing: Effects in Damascus goat milk production parameters and the mammary gland...

This study investigates the effect of mixed systems (suckling and machine milking) vs artificial rearing (only machine milking), on milk production, milk composition and the transcriptome of the mammary epithelium in Damascus goats. Thirty goats, in their first lactation period, were allocated into 2 experimental groups: artificial rearing (AR) and mixed rearing (MR). In the AR group, kids were separated from their mothers immediately after birth, whereas in the MR group, the goats suckled their kids until weaning (49 ± 3 d postpartum) while all goats were mechanically milked twice daily throughout the milking period. Commercial milk yield and milk fat, protein, lactose and total solid contents were recorded and milk fatty acid (FA) profile was analyzed. On the 42nd day postpartum, mammary epithelial biopsies were taken from 6 goats per experimental group for transcriptomic analysis by 3'mRNA sequencing. The results showed that while commercial milk yield before weaning was higher (P <0.05) in the AR (116.58L) compared with the MR group (73.16L), total commercial milk yield for the whole lactation period did not differ significantly between AR (351.3L) and MR groups (312.2L). Milk contents did not differ between groups (P >0.05) but total protein, lactose, solid nonfat yields were higher (P <0.05) in the AR group. Analysis of the FA profile revealed lower saturated, higher unsaturated and monosaturated FA contents in the MR group (P <0.05), while no differences were observed in the polyunsaturated FA content. The transcriptomic analysis revealed 9 differentially expressed (DE) genes (RBM8A, Clusterin, PPDPF, LOC108635834, BLMH, PINK1, PIM1, OSBPL7, and SMU1) and 12 genes showing a trend for DE. The genes which were differentially regulated in response to kid suckling are involved in developmental processes, RNA metabolism, nutrient and lipid transport and tissue regeneration. In conclusion, this study showed that kid suckling in Damascus goats does not adversely affect commercial milk production or milk composition, while it yields commercial milk with a nutritionally more favorable fatty acid profile. Furthermore, this is the first transcriptomic study addressing concurrent suckling and machine milking effects in mammary physiology in ruminants.