Genetic Parameters of Milk Coagulation Properties and Their Relationships with Milk Yield and Quality Traits in Italian Holstein Cows

Abstract

Milk coagulation properties (MCP) are an important aspect in assessing cheese-making ability. Several studies showed that favorable conditions of milk reactivity with rennet, curd formation rate, and curd strength, as well as curd syneresis, have a positive effect on the entire cheese-making process and subsequently on the ripening of cheese. Moreover, MCP were found to be heritable, but little scientific literature is available about their genetic aspects. The aims of this study were to estimate heritability of MCP and genetic correlations among MCP and milk production and quality traits. A total of 1,071 Italian Holstein cows (progeny of 54 sires) reared in 34 herds in Northern Italy were sampled from January to July 2004. Individual milk samples were collected during the morning milking and analyzed for coagulation time (RCT), curd firmness (a30), pH, titratable acidity, fat, protein, and casein contents, and somatic cell count. About 10% of individual milk samples did not coagulate in 31 min, so they were removed from the analyses. Estimates of heritability for RCT and a30 were 0.25 +/- 0.04 and 0.15 +/- 0.03, respectively. Estimates of genetic correlations between MCP traits and milk production traits were negligible except for a30 with protein and casein contents (0.44 +/- 0.10 and 0.53 +/- 0.09, respectively). Estimates of genetic correlations between MCP traits and somatic cell score were strong and favorable, as well as those between MCP and pH and titratable acidity. Selecting for high casein content, milk acidity, and low somatic cell count might be an indirect way to improve MCP without reducing milk yield and quality traits.

Heritability and repeatability of milk coagulation properties predicted by mid-infrared spectroscopy during routine data recording, and their relationships with milk yield and quality traits

“…Mean (32.00 kg/day) and variation (CV of 27.5%) for MY of Holstein-Friesian from the present study are consistent with values (32.30 kg/day and 31%, respectively) reported by Cassandro et al (2008) in an Italian study conducted on the same breed. Values of FP and PP are slightly lower than findings of Cassandro et al (2008), with 3.73% v. 3.89% for FP and 3.37% v. 3.45% for PP, respectively, whereas CP is Cassandro et al (2008), who reported 16.9 min for RCT and 32.0 mm for a 30 measured by the computerized renneting meter.…”

“…However, the variability was quite similar as the CV were 18.4 (v. 27%) and 39.6 (v. 35%) for RCT and a 30 , respectively. Average pH predicted by MIRS, showed a lower mean value (6.62 v. 6.67) compared with that of Cassandro et al (2008) measured with a pH-meter. Average values for MCP and milk composition are worse than those of Cecchinato et al (2009) in Italian Brown Swiss, who reported means of 15.0 min for RCT and 41.7 mm for a 30 evaluated using the computerized renneting meter, and by Bonfatti et al (2011) in Italian Simmental, who reported RCT and a 30 of 16.51 min and 29.08 mm, respectively, using the same mechanical device.…”

“…Values of FP and PP are slightly lower than findings of Cassandro et al (2008), with 3.73% v. 3.89% for FP and 3.37% v. 3.45% for PP, respectively, whereas CP is Cassandro et al (2008), who reported 16.9 min for RCT and 32.0 mm for a 30 measured by the computerized renneting meter. However, the variability was quite similar as the CV were 18.4 (v. 27%) and 39.6 (v. 35%) for RCT and a 30 , respectively.…”

“…In addition, the possibility of improving MCP through selective breeding has been demonstrated in several studies, involving different dairy cattle populations in different countries. Additive genetic variation has been estimated in papers focusing on cow individual measures of MCP and heritabilities for RCT and a 30 were found to be moderate (Ikonen et al, 2004;Cassandro et al, 2008;Vallas et al, 2010). In addition, cow repeatabilities were moderate to high (Tyrisevä et al, 2003;Vallas et al, 2010).…”

“…The most used instruments to measure MCP are the computerized renneting meter (Ikonen et al, 2004;Cassandro et al, 2008), the Formagraph (Tyrisevä et al, 2003;CipolatGotet et al, 2012) and the Optigraph (Vallas et al, 2010). Unfortunately these methodologies are not applicable at population level, and thus they are not useful for breeding purposes.…”