Milking-to-Milking Variability for Milk Yield, Fat and Protein Percentage, and Somatic Cell Count

Abstract

The main objectives were to analyze milking-to-milking variability in milk yield, fat and protein percentages, and somatic cell count (SCC). Additional objectives were to investigate the factors that affect variation in milk fat percentage and to study the seasonal variations in milk, fat, and protein yields and SCC. A total of 16 farms (14 milked 2x and 2 milked 3x) across Canada participated in a 5-d milk-sampling study, with 27,328 milk samples collected and analyzed for fat and protein yields and SCC. Descriptive statistics for both 2x and 3x herds for milk yield and fat and protein percentages followed a typical pattern throughout lactation, and the somatic cell linear scores were higher in early lactation for first-lactation cows (4.7 vs. 3.8) but were higher at the end of lactation for cows in second lactation or greater (5.1 vs. 4.9). The 2x herds had higher milk yields in the morning (approximately 17 vs. approximately 14 kg), whereas the 3x herds had the lowest milk yields in the morning, and yields peaked at the evening milking (approximately 9 vs. approximately 11.2 kg). A herd management questionnaire was distributed to participating producers to investigate the relationship between management variables and variations in milk fat percentage over the 5-d sampling period. Data from the questionnaire determined that milking period had a significant effect on milk fat in 2x herds, with fat percentage 1.11% lower in the morning compared with the evening milking period. Seasonal differences in milk, fat, and protein yields were investigated in 910 cows on 3 farms, with 5,517 fat and 5,534 protein samples. The seasonal differences in fat yield [summer = 1.02 +/- 1.05 kg/d (SEM); winter = 1.19 +/- 1.05 kg/d] and protein yield (summer = 0.85 +/- 1.05 kg/d; winter = 0.96 +/- 1.05 kg/d) were significant only for first lactation. Understanding the variability in milk yield, fat and protein percentages, and SCC is important when making management decisions and in milk-recording programs.

Gene expression of six major milk proteins in primary bovine mammary epithelial cells isolated from milk during the first twenty weeks of lactation

“…As a result, although only morning milk yield which is higher than evening milk yields (Quist et al, 2008) was evaluated, the estimated shape of lactation curves during the first 20 weeks of lactation were consistent with those reported by numerous previous studies (e.g. Wood, 1969;Walsh et al, 2007).…”

The Season Effect on the Milk Fatty Acid Profile of Oulmes Breed Cattle in Moroccan Oulmes Zone

“…Nevertheless, cow feeding can be an important way to improvethe dietary qualities of milk fat.The aim of this workwas to investigate the diet of dairy cows and the fatty acid profiles of the produced milk during different seasons knowing that seasonal fluctuations are quantitatively significant and due mainly to changes in diet (Quist et al, 2008).…”

Short communication: Bovine milk sampling efficiency for pregnancy-associated glycoproteins (PAG) detection test

“…Milk samples collected during morning milking have a lower fat content compared with samples collected in the evening milking (Reis et al, 2007;Quist et al, 2008;Forsback et al, 2010;Pavel & Gavan, 2011). Differences in the protein levels, which do not change significantly depending on time of milking, were obtained (Quist et al, 2008;Løvendahl & Chagunda, 2011;Pavel & Gavan, 2011). As to specific PAG levels, no studies have assessed the effect of the time of day that milking is carried on these levels.…”

“…However, the representativeness of the milk sample subjected to laboratory analysis can be influenced by the way it is collected, especially with regard to the time of day it is obtained and the possible carryover in the milking systems before the collection of the sample (Løven-dahl & Bjerring, 2006;Quist et al, 2008;Pavel & Gavan, 2011). Milk samples collected during morning milking have a lower fat content compared with samples collected in the evening milking (Reis et al, 2007;Quist et al, 2008;Forsback et al, 2010;Pavel & Gavan, 2011).…”