Effects of lactation stage, parity, β-lactoglobulin genotype and milk SCC on whey protein composition in Sarda dairy ewes

Abstract

In 90 Sarda dairy ewes the effects of lactation stage, parity, β-lactoglobulin genotypes, and somatic cell count (SCC) on the milk content of total protein (TP), casein (CN), whey protein (WP) and its fractions α-lactalbumin (ALA), β-lactoglobulin (BLG), serum albumin (SA), immunoglobulin (IG) and lactoferrin (LF) were analysed using a linear mixed model. Mean values of variables (g/l) were: TP (54.0), CN (43.0), WP (11.0), BLG (4.78), ALA (1.37), SA (0.61), IG (3.83) and LF (0.28). The lactation stage significantly affected all the variables analysed. TP, CN and WP concentrations tended to increase throughout lactation, with the increase of WP being more pronounced than the corresponding variation in CN. There was no definite trend in BLG content, whereas ALA concentration decreased as lactation progressed. The parity affected almost all variables studied. WP concentration differed significantly only between the second and fourth parity (10.45 vs 11.44 g/l). BLG and SA concentrations were significantly lower in the youngest ewes. The BLG genotype affected milk yield, but no effects were observed on the components of the milk. The SCC influenced almost all variables studied. The TP concentration was significantly higher in milk with SCC >1,000,000 (55.0 g/l) than in milk with lower SCC (53.4 g/l). This was mainly due to the increase of WP (12.52 and 10.24 g/l in milk with SCC above and below 1,000,000/ml respectively), especially in those WP fractions originating from blood. TP (54,0), CN (43,0), WP (11,0), BLG (4,8), ALA (1,4), SA (0,61), IG (3,83) e LF (0,28

Effects of intramammary infection on whey proteinograms of sheep during lactation

“…A significant increase (P<0.0001) in β-lactoglobulin concentration was observed in infected glands compared to that in healthy ones (Table 1, Fig.4), which is in agreement with the results of Nudda et al (2003), who observed significant increases in β-lactoglobulin in the whey of sheep with mastitis with somatic cell counts higher than 1.000.000. These results differ from that reported in other studies involving ruminants.…”

“…Similar results have been reported by Nudda et al (2003), who observed a two-fold increase in lactoferrin concentrations in whey samples from sheep with somatic cell counts above one million. Sant'ana (2004) also reported a two-fold increase in lactoferrin concentration in cows with mastitis, and Raimondo et al (2011) reported a significant increase in lactoferrin concentration in goats with mastitis, highlighting the precociousness of its appearance compared to that of other whey proteins.…”

“…Although not statistically significant (P>0.1252), these results showed an elevated α-lactalbumin concentration in infected glands, thus supporting the findings of Sant'ana (2004), who used whey samples from cows. Nudda et al (2003) also observed a significant increase in this protein fraction in relation to an increase in somatic cell counts in sheep with mastitis. However, these results contradict the observations of Raimondo et al (2011), who observed a decrease in α-lactalbumin values in cases of mastitis in goats, and also those by Bortree et al (1962), Schalm et al (1971), Harmon et al (1976), andProsser &McLaren (1997), who described an association between a decrease in α-lactalbumin and a decrease in lactose in mastitis cases.…”

“…For example Sant'ana (2004) did not observe significant changes in the whey proteinogram of cows with mastitis, whereas Raimondo et al (2011) observed a decrease in β-lactoglobulin in goats with mastitis. The increase in β-lactoglobulin in infected sheep mammary glands may be attributable to its actual concentration rather than to increased production because less milk is generally produced during mastitis (Nudda et al 2003).…”

Milk yield and composition in line 05 dairy ewes as related to somatic cell counts

“…Numerous authors have shown that a high level of somatic cells in ewe milk is connected with a higher protein percentage compared with the protein content in low SCC milk (Nudda et al, 2003;Albenzio et al, 2004;Bianchi et al, 2004). However, other authors reported low protein contents in milk with a high SCC (Jaeggi et al, 2003).…”