Milk yield, quality, and coagulation properties of 6 breeds of goats: Environmental and individual variability

Abstract

Goat milk and cheese production is continuously increasing and milk composition and coagulation properties (MCP) are useful tools to predict cheesemaking aptitude. The present study was planned to investigate the extension of lactodynamographic analysis up to 60 min in goat milk, to measure the farm and individual factors, and to investigate differences among 6 goat breeds. Daily milk yield (dMY) was recorded and milk samples collected from 1,272 goats reared in 35 farms. Goats were of 6 different breeds: Saanen and Camosciata delle Alpi for the Alpine type, and Murciano-Granadina, Maltese, Sarda, and Sarda Primitiva for the Mediterranean type. Milk composition (fat, protein, lactose, pH; somatic cell score; logarithmic bacterial count) and MCP [rennet coagulation time (RCT, min), curd-firming time (k, min), curd firmness at 30, 45, and 60 min after rennet addition (a, a, and a, mm)] were recorded, and daily fat and protein yield (dFPY g/d) was calculated as the sum of fat and protein concentration multiplied by the dMY. Data were analyzed using different statistical models to measure the effects of farm, parity stage of lactation and breed; lastly, the direct and the indirect effect of breed were quantified by comparing the variance of breed from models with or without the inclusion of linear regression of fat, protein, lactose, pH, bacterial, somatic cell counts, and dMY. Orthogonal contrasts were performed to compare least squares means. Almost all traits exhibited high variability, with coefficients of variation between 32 (for RCT) and 63% (for a). The proportion of variance regarding dMY, dFPY, and milk composition due to the farm was moderate, whereas for MCP it was low, except for a, at 69%. Parity affected both yield and quality traits of milk, with least squares means of dMY and dFPY showing an increase and RCT and curd firmness traits a decrease from the first to the last parity class. All milk quality traits, excluding fat, were affected by the stage of lactation; RCT and k decreased rapidly and a was higher from the first to the last part of lactation. Alpine breeds showed the highest dMY and dFPY but Mediterranean the best percentage of protein, fat, and lactose and a shorter k and a greater a. Among the Mediterranean goats, Murciano-Granadina goats had the highest milk yield, fat, and protein contents, whereas Maltese, Sarda, and Sarda Primitiva were characterized by much more favorable technological properties in terms of k, a, and a. In conclusion, as both the farm and individual factors highly influenced milk composition and MCP traits, improvements of these traits should be based both on modifying management and individual goat factors. As expected, several differences were attributable to the breed effect, with the best milk production for the Alpines and milk quality and coagulation for the Mediterranean goats.

Non-parametric analysis of the effects of αS1-casein genotype and parturition non-genetic factors on milk yield and composition in Murciano-Granadina goats

“…Our sample presents a between-farm variability that ranges from 17.8% to 20.6% for fat and milk yield, respectively. A similar effect power of farms on the yield and quality of the milk of 6 breeds of goats has been reported to range from around 20% to 45% (Vacca et al 2018). As reported by Nolan and Heinzen (2017), as the sample size increases, a normal distribution of scores will more closely resemble a normal curve, hence reducing the effects of violating the normality assumption.…”

Effect of composition on coagulation, curd firming, and syneresis of goat milk

“…The effects of animal factors (DIM, parity, and breed) and farm were included in the statistical model to correct the estimation for the effect of milk composition on coagulation, curd firming, and syneresis processes. In the present study, these are reported only in the results because they have been discussed in depth in previous studies on the same data set (Vacca et al, 2018a;Pazzola et al, 2018). Briefly, DIM affected almost all coagulation traits.…”

“…A total of 1,272 goats belonging to 6 breeds, reared in 35 farms distributed over the island of Sardinia (Italy) were sampled once for milk composition. Details of farm characteristics and description of the breeds are reported by Vacca et al (2018a).…”

“…In Sardinia, those strategies have led to a general decrease of fat and protein contents in milk (Vacca et al, 2016). Because large differences are detectable among goat breeds in terms of milk composition (Vacca et al, 2018a) and cheese-making efficiency (Vacca et al, 2018b), new knowledge about the effect of goat milk composition on the renneting properties could provide useful information for farmers and dairy plants.…”

Hycole Doe Milk Properties and Kit Growth

“…The milk pH is a popular indirect indicator of mastitis [21,22]. The physiochemical quality of milk from different goat breeds was analyzed by Vacca et al [32]. They found that the mean pH measured 6.72, but it varied from 6.67 to 6.76 between breeds.…”