Investigation into aspects of milk quality and mastitis in sheep : A thesis submitted in partial fulfilment of the requirements for Masters at Lincoln University

Abstract

Associations among udder characteristics, milk yield, milk somatic cell counts, lamb growth and prevalence of mastitis were evaluated in 121 twin-suckled crossbred non-dairy ewes at four, eight and twelve weeks after parturition. Milk production per four hours decreased with time, being 1.09 ± 0.04 litres at week four of lactation, 0.68 ± 0.02 litres at week eight and 0.48 ± 0.01 litres at week twelve, and with respective mean somatic cell counts (SCC) of 0.32 x 106 cells mL-1, 0.39 x 106 cells mL-1 and 0.28 x 106 cells mL-1. Incidence of mastitis was 12.7%, 9.8% and 8.9% for weeks 4, 8 and 12, respectively. Of the 20 individuals that displayed SCC indicative of mastitis, only five had elevated SCC at more than one sampling time and none were positive for Staphylococcus aureus. However, S. aureus was present in 1% of the 474 milk samples analysed but only at weeks 4 and 8. There was inconsistent association between SCC and visual scores for udder depth, udder distention, degree of separation or teat placement (P>0.05 for all). Milk volume and weight of lamb was greater (P<0.05) for ewes with an udder depth of score 3 compared with score 4 with no other associations evident (P>0.05). The incidence of subclinical mastitis was low but present in this flock with the udder characteristics assessed being poor indicators of either mastitis or milk production, and there was no impact on lamb growth.