Variation in Milk Yield, Contents and Incomes According to Somatic Cell Count in a Large Dairy Goat Population

Francisco Javier

doi:10.4172/2329-888x.1000145

Abstract

Between 2009 and 2014, 758,382 monthly test-day records were obtained from 65,056 Murciano-Granadina goats in 132 Spanish dairy flocks. Variables measured were somatic cell count (SCC), milk yield and fat and protein percentages; means were 5.78log10 cells/ml, 2.04 L/day, 5.37% and 3.67%, respectively. Significant effects of year, herd test date, season, parity, month of lactation, litter size and covariables milk yield, fat and protein contents were evidenced on SCC. The regression slopes were negative for milk yield an d positive for fat and protein content, thus pointing out that high SCC in milk were associated with low milk yield and high contents. A second ANOVA was built to evaluate the evolution of test-day variables as SCC level increased within lactation. The percentages estimated in losses of milk yield for SCC levels 1 million cells/ml, 2 million cells/ml, 3 million cells/ml and >7 million cells/ml were 11.4%, 19.5%, 24.2% and 35.7%, respectively. Milk contents gains were also quantified. Milk incomes per goat and day (according to current payment system) revealed important economic losses (from 9.5% to 31.6%) for abovementioned SCC levels. Results emphasize the importance of SCC as a limiting factor for milk incomes in dairy goats.

Highlights

Subclinical mastitis is a common problem in dairy herds and somatic cell count (SCC) has been widely used in ruminant species as an indirect and inexpensive diagnostic method of udder health status
Coefficients of variation was highest for milk yield and lowest for log SCC, and fat content evidenced a higher variability than protein content, as expected
The important percentage losses estimated from test day milk yield for Murciano-Granadina goats, as SCC level increased, were similar than those reported by Baudry et al [7] in 254 dairy goats flocks in France (7.9 to 16.9%) when milk yield of 3 SCC levels (< 750 x 103 cells/ml; between 750 x 103 and 1750 x 103 cells/ml; and >1750 x 103 cells/ml) were compared

Summary

Introduction

Subclinical mastitis is a common problem in dairy herds and somatic cell count (SCC) has been widely used in ruminant species as an indirect and inexpensive diagnostic method of udder health status. Barrón-Bravo et al [6] in a study using only information from first lactation for Alpine, Saanen and Nubian goats estimated losses in test day milk yield ranged from 0.5 to 29.1% according to different SCC levels. Baudry et al [7] in French dairy goat flocks found losses in milk yield ranged from 7.9% and 16.9% when a low SCC level was compared with other two high SCC levels. Koop et al [11] show that milk yield losses caused by subclinical udder infections are limited in goats and that SCC cannot be used to estimate the magnitude of these losses. A dilution effect seems to play an important role in the negative association between SCC and milk yield [11,13]

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Conclusion