No abstract

There is little information about the effect of the stress on Somatic Cell Count (SCC) and milk yield and composition in goats. A total of 40 goats in their 4 th month of lactation were assigned to two groups: stress (STR) and untreated (CON). Goats of STR were exposed to acute stress (visual and auditory stimulus from a barking dog for 20 minutes on day 0). After the stress, average values of plasma cortisol were higher in STR than CON (P < 0.001); likewise, in STR group cortisol was lower in parity 1+2 goats than parity ≥ 3 goats (P < 0.05). Stress caused a considerable increase in SCC in parity ≥ 3 goats (P < 0.05), but not in parity 1+2 goats. On average, this increase of SCC was 6-fold compared to values prior to the stress, and it was observed in both healthy and infected mammary glands. This increase was transient, as SCC returned to normal values after 1 to 3 days. On day 1, stressed goats of parity ≥ 3 produced 11% less milk compared with day 0 and, regarding milk composition, only lactose showed a significant drop. Stressed parity 1+2 goats showed no changes in SCC and milk yield and composition. We conclude that, in goats, stress is a non-infectious factor 2 that can interfere in the use of SCC as an indirect method of intramammary infection (IMI) detection or, in bulk tank milk, as a commercial milk quality parameter.

The aim of this work was to evaluate the effect of intramammary infection (IMI) on the endogenous proteolysis of milk. Four control checks were carried out in the half-udder milk of 10 ewes that acquired unilateral subclinical mastitis. Two of these checks were conducted before the infection was established and 2 after. Ten healthy ewes were tested as a control group. The presence of a subclinical IMI involved an increase of the products of casein hydrolysis, the proteose-peptone (p-p) fraction and minor (m) caseins, and a decrease of β-casein. As a result, a significant increase in the proteolysis index (PI), calculated as the ratio of m-casein to the sum of caseins (α + β + κ), took place. α-Casein and κ-casein were not significantly affected by IMI. Correlations confirmed the scenario: log(10) of somatic cell count (SCC) was positively correlated with p-p content and negatively with β-casein, whereas log(10) SCC was not correlated with α-casein or κ-casein. On the other hand, p-p content was positively correlated with m-casein and PI and negatively with β-casein, but no correlation was detected between p-p content and α- or κ-casein. Furthermore, between casein fractions, m-casein was only significantly correlated with β-casein. These results suggest that use of indices of proteolysis of caseins such as p-p, m-casein, and PI, could be applied together with SCC to evaluate the cheese-making quality of milk.

JDR4151 proof to ECN(BTSCC>1000000) (Ariznabarreta, 1999 Materials and Methods 89Experimental design

No abstract