Effect of parity on milk yield, composition, somatic cell count, rennetingparameters and bacteria counts of Comisana ewes

Twenty-four Comisana ewes, with no history of mastitis, were included in th is study, with eight ewes each in parities 1, 2 and 3, Groups were separate ly penned on straw litter and ewes were individually checked for yield, com position, renneting properties and bacteriological characteristics of milk from January, when separated from their lambs (50 +/- 3 days after lambing) , to May, Samples with more than 3.5 x 10(5) somatic cells/ml were cultured for mastitis related pathogens. Milli yield was not significantly affected by parity. The P3 ewes had significantly higher milk protein, casein and f at contents compared to the P1 and P2 ewes. The P3 ewes also had improved r enneting ability of milk as compared to the P1 ewes. Quality of milli decre ased with lower lactations. The milk of PI ewes had significantly greater a mounts of mesophilic bacteria than the P2 and P3 ewes, as well as higher co ncentrations of psychrotrophs and total coliforms in their milk with respec t to the P3 ewes. Somatic cell counts in milk and the prevalence of subclin ical mastitis were not changed by parity, although mastitis infection set i n progressively earlier as the number of lactations decreased. These result s suggest that ewes in first or second lactation have a less favourable mil k secretion status in relation to mastitis than ewes with a higher number o f lactations. Milk yield and quality of younger ewes may be improved by off ering feed rations that take into account this reduced capacity to mobilise body reserves, Also, most scrupulous control of sanitation of housing, equ ipment and personnel is necessary. (C) 2000 Elsevier Science B.V. All right s reserved.