Effect of subclinical intrammamay infection on milk quality in dairy sheep: I. Fresh-soft cheese produced from milk of uninfected and infected glands and from their blendsSmall Ruminant Research


Rovai Maristela, Rusek Natalia, Caja Gerardo, Saldo Jordi, Leitner Gabriel
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Small Ruminant Research 125 (2015) 127–136

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Small Ruminant Research jou r n al homep age : w w w . elsev ier .com/ locate /smal l rumres

Effect of subclinical intrammamay infection on milk quality in dairy sheep: I. Fresh-soft cheese produced from milk of uninfec

Rovai Ma

Leitner G a Grup de Rece b CERPTA-Plan

Spain c National Mas a r t i c l

Article history:

Received 28 Ja

Received in re

Accepted 25 F

Available onlin


Subclinical ma



Milk composit

Clotting param ∗ Correspon

E-mail add 1 Current a http://dx.doi.o 0921-4488/© ted and infected glands and from their blends ristelaa,1, Rusek Nataliaa, Caja Gerardoa, Saldo Jordib, abriel c,∗ rca en Remugants (G2R), Facultat de Veterinària, Universitat Autònoma de Barcelona (UAB), Bellaterra, Barcelona, Spain ta de Tecnologia dels Aliments, Facultat de Veterinària, Universitat Autònoma de Barcelona (UAB), Bellaterra, Barcelona, titis Reference Center, Kimron Veterinary Institute, P.O. Box 12, Bet Dagan 50250, Israel e i n f o nuary 2015 vised form 25 February 2015 ebruary 2015 e 5 March 2015 stitis ion eters a b s t r a c t

Subclinical intramammary infection (IMI) is associated with a decrease in milk yield and changes in milk composition. The effects of IMI on fresh-soft cheese yield and quality were evaluated by: (i) the effect on the composition and coagulation properties; (ii) the effect of three levels of coagulating enzyme and three temperatures in the presence and absence of added CaCl2 on milk coagulation properties (milk from uninfected and infected halves and a blend of 50:50); (iii) the effect the milk source: uninfected, infected halves and a blend of 50:50 and 75:25 (uninfected:infected) on the production of small cheese blocks. Somatic cell count was significantly higher in infected glands of both Manchega and Lacaune dairy sheep breeds. In milk from infected glands, 25–30% of the milk did not coagulate. Rennet clotting time (RCT) of milk from infected glands was doubled and curd firmness (CF) was much lower in comparison to samples taken from the contra-lateral uninfected glands.

Addition of Ca and temperature levels did not influence RCT in any of the milk combinations, while CF was significantly higher in milk from uninfected glands and 50:50 blends and also was higher as temperature increased. Enzyme concentration significantly influenced RCT and CF in milk from both uninfected and in the 50:50 blends but not in the milk from infected glands. IMI affected significantly milk syneresis, which was slower in the infected and in the 50:50 blends. The changes in syneresis were reflected in higher moisture in the curd of milk sampled from infected glands. The contents of fat, protein and dry matter in the cheese were significantly lower in the 50:50 blends compared to uninfected milk, whereas the contents of these organic components in the 75:25 blends were in-between. The distance required to penetrate the cheese before crushing was significantly deeper in cheese made from a 50:50 blend than that of cheese made from uninfected milk and 75:25 blend, which indicated that IMI modified cheese structure into softer and more elastic texture. The study also indicated that during storage of the milk before processing, milk quality (lower pH, increased

RCT and decreased CF) from 50:50 blends deteriorated faster in comparison to uninfected milk. © 2015 Elsevier B.V. All rights reserved. ding author. Tel.: +972 3 9681745; fax: +972 3 9681692. ress: leitnerg@moag.gov.il (L. Gabriel). ddress: Department of Dairy Science, College of Agriculture and Biological Science, South Dakota State University, Brookings, SD 57007, USA. rg/10.1016/j.smallrumres.2015.02.019 2015 Elsevier B.V. All rights reserved. 128 R. Maristela et al. / Small Ruminant Research 125 (2015) 127–136 1. Introduction

Cheese is the essence of dairy sheep farming. The quantity and quality of cheese play a key role for success in selling the coagulation ity are nece any impair and/or qual

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In order nical masti in quantity well as onuse of a h et al., 2004a et al., 2006 tified the n yield even mals. The h for creating neutralizes the variation between animals and experimental factors from masking effects. On the contrary, the conventional whole-udder model would require a data set of hundreds of animals to account for the large and signt ind ureme iversit ental porte ot to , 2004 ent p during uality of Stre ilk co ty of spec ent pa m, ca sociat ylococ ; Chan other from in mod mplica olysis b our k lation as a po produ e obje tity, m nfluen se mak ic sub . terials nimals a e study i de Gra celona ( uman Ex al and a total of

Lacaun ay post ing to b a half-u with va ilking. T ed. For d and t rom all roviding (MING ilk samp oss NIR ine con n (TP), a ell et al n, preseproduct at good price. Attaining proper rennet properties, curd firmness and syneresis abilssary to achieve desired cheese quality. Thus, ment which causes a decrease in milk yield ity can have detrimental effects on the industry. fundamental causes of such damage is intrainfection (IMI) by different bacteria species (Le t al., 2011). Under prevailing farm conditions, r of clinical udder infection events is low. The on cause of clinical mastitis are Gram negaa, which in most cases destroy the milk gland nd Berthelot, 2003). If the animals survive, proecreases while the quality of milk is sustained uninfected glands are milked. The occurrence al infections in dairy sheep farms is high, ranen 10% and 60% (Leitner et al., 2003; Contreras ). While it is generally accepted that the ecoct of IMI, both on the individual and whole dairy ificant, its quantitative impact on cheese yield remains vague and controversial (Klei et al., mer et al., 2015). Hence, the effects of subclimost cases are ignored as long as the animal ofitable while only milk yield decreases. Howntries where a payment criterion is based on ank somatic cell count (BMSCC), the presence el infection, which usually is associated with