1. Loss in milk yield and related composition changes resulting from different levels of somatic cell count in Valle del Belice dairy sheep
A. M. Sutera, M.Tolone, S. Mastrangelo, M. T. Sardina, B. Portolano
Dipartimento Scienze Agrarie e Forestali, Università degli Studi di Palermo, Palermo, Italy
Introduction
In particular for F%: 5.75% for SCC≤500x103 and 6.05% for SCC>2,000x103; for P%: 7.43% for SCC≤500x103 and 7.64% for SCC>2,000x103. The Figures 2, 3, 4 showed that MY (g), F (%) and P (%), for SCC1 were statistically different for MY (g), F (%) and P (%), of each SCC class.
Mammary infections cause high somatic cell count (SCC) and severe damage to udder tissue and result in important losses of milk yield and quality, curd and cheese yields in dairy ewes. The aim of this study was to determine the effect of different levels of SCC on milk yield and composition in Valle del Belice dairy sheep.
Table 1: Least square means (LSM) for test day MY (g), F (%) and P (%), according to different class of SCC
SCC class
MY (g) LSM ± SE
F (%) LSM ± SE
P (%) LSM± SE 1
± 20.10*
7.43 ± 0.04*
5.75 ± 0.02* 2
± 22.09*
7.59 ± 0.05*
5.86 ± 0.03* 3
± 24.65*
7.59 ± 0.06*
5.93 ± 0.03* 4
± 29.53*
7.64 ± 0.06*
6.00 ± 0.03* 5
± 21.43*
7.64 ± 0.05*
6.05 ± 0.02* a b
Fig. 1: a) Valle del Belice sheep breed; b) udder infected with mastitis
*p<0.01
Materials and methods
Test-day records of milk yield (MY), fat % (F%), protein % (P%), and SCC were collected following an A4 recording scheme between 1994 and 2006 in 15 Valle del Belice flocks.
Original data consisted of 92,261 observations on 6,763 ewes. After editing we had 17,060 observations on 2,418 ewes.
Five different classes of SCC were arbitrarily defined (1: SCC≤500×103; 2: 500×103<SCC≤1,000×103; 3: 1,000×103<SCC≤1,500×103; 4: 1,500×103<SCC≤ 2,000×103; 5: SCC>2,000×103).
A linear model as factorial design of fixed effects was used with the GLM procedure of S.A.S. statistical software. The following model was used:
y= FK+OP+AOP+STG+SCC+DIM+e
where: y was the measured response variable (MY, F% or P%); FK was the effect of flock (15 levels); OP was the effect of parity class (4 levels); AOP (covariate) was the age of lambing; STG was the season of lambing (3 levels); DIM was the class of days in milk (5 levels) and e was the random error.
Fig. 2: MY comparison for SCC class
Fig. 3: F% comparison for SCC class
Fig. 4: P% comparison for SCC class
Conclusion
These experimental results together with data present in literature, demonstrated that it is necessary to implement a program aimed to reduce the SCC in ewe’s milk, with the aim of improving the quality of ewe milk and dairy products. Moreover, these results could be used to quantify the economic loss due to an increase in SCC that is crucial to estimate the economic value for SCC trait in Valle del Belice dairy sheep, and although focused in a specific sheep breed, they could be widely applied.
Results
All fixed effects included in the model were significant (P<0.001). The estimated losses in MY according to the level of SCC used were approximately 20%, (903g for SCC≤500x103 and 726g for SCC>2,000x103). However we had an increase of 4.9% and 2.7% on F% and P%, respectively (Table 1).
21st ASPA Congress, Milan – Italy, 9-12 June 2015