Effect of somatic cell count and lactation stage on sheep milk quality

Abstract

In order to evaluate the effects of mammary health status and lactation phase on the qualitative parameters of ovine<br />milk, 213 individual milk samples were repeatedly collected from 40 primiparous Sarda ewes on a monthly basis. Yield,<br />physico-chemical characteristics, casein fractions quantitative distribution, somatic cell count (SCC), cheese making properties<br />and plasmin-plasminogen activity were determined on each sample. Repeated individual milk SCC were used as a<br />marker of udder health status, allowing the definition of three classes: &ldquo;Healthy&rdquo; (H), &ldquo;Infected&rdquo; (I) or &ldquo;Doubtful&rdquo; (D).<br />Samples were grouped into 4 classes of days in milk (DIM). To evaluate the influence of mammary health status and<br />phase of lactation, a mixed model was performed using the ewe as random effect. Milk physico-chemical parameters were<br />influenced both by the udder health status and by lactation phase. In particular, the udder health status adversely affected<br />&alpha;s1 and &beta;1-casein fractions (P<0.01) and curd firmness (P<0.05). Samples reactive to rennet were 92.73%, 70.65%<br />and 64.60% in &ldquo;H&rdquo;, &ldquo;D&rdquo; and &ldquo;I,&rdquo; respectively. Lactation phase influenced the overall milk composition and technological<br />characteristics. Plasmin activity was higher in the &ldquo;I&rdquo; group than in the others (16.1 vs 11.8 and 11.2 U/ml; P<0.01) and<br />it significantly (P<0.01) increased during lactation. In conclusion, both mastitis and mammary involution are proven to<br />exert a detrimental effect on milk quality since they enhance its endogenous proteolytic activity

Seasonal Variation of Chemical Composition, Fatty Acid Profile, and Sensory Properties of a Mountain Pecorino Cheese

“…Due to the market demand for young lambs at Christmas [34,35], in both flocks most of the ewes lambed in autumn, and only primiparous and a small percentage of pluriparous animals (about 20%) lambed at the end of winter. Thus, the observed increments of milk components may be due to the concentration effect related to the lower yield at the end of lactation [16,36]. Moreover, also the progressive deterioration of the ewe udder health in late lactation can increase SCC in ewe milk [37,38].…”

Sustainability of Sheep and Goat Production Systems

“…Lactation is thus often shortened given that dairy factories stop collecting milk from farms since it is produced in smaller amounts and its coagulating behavior is deteriorated. Indeed, a number of events can occur in summer, which have a deleterious effect on coagulating properties of sheep milk and, namely, (1) the use of fat and nitrogen reserves to supply energy through gluconeogenesis at the expense of the mammary gland (Amaral-Phillips et al 1993), (2) a plasma mineral imbalance, especially due to a reduction in sodium, potassium, calcium, and phosphorus and to an increase in chloride concentrations (Kume et al 1987), (3) an increased milk pH, due to high amounts of CO 2 dissipated via the panting (Habeeb et al 1992), (4) an increased plasmin (PL) activity, the main endogenous proteinase in milk (Bianchi et al 2004), (5) an increased bacterial load in milk, due to enhanced multiplication and growth of microorganisms in the litter (Sevi et al 2001a). A worsening in milk coagulating behavior in ewes reared in pens without shading areas and receiving feed during the warmest part of the day has been observed (Sevi et al 2001a).…”

The Sustainability of Agro-Food and Natural Resource Systems in the Mediterranean Basin

“…Indeed, a number of events can occur in summer, which have a deleterious effect on coagulating properties of sheep milk and, namely, (1) the use of fat and nitrogen reserves to supply energy through gluconeogenesis at the expense of the mammary gland (Amaral-Phillips et al 1993), (2) a plasma mineral imbalance, especially due to a reduction in sodium, potassium, calcium, and phosphorus and to an increase in chloride concentrations (Kume et al 1987), (3) an increased milk pH, due to high amounts of CO 2 dissipated via the panting (Habeeb et al 1992), (4) an increased plasmin (PL) activity, the main endogenous proteinase in milk (Bianchi et al 2004), (5) an increased bacterial load in milk, due to enhanced multiplication and growth of microorganisms in the litter (Sevi et al 2001a). Lactation is thus often shortened given that dairy factories stop collecting milk from farms since it is produced in smaller amounts and its coagulating behavior is deteriorated.…”