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

Helen K Da Silva,Paulo F Machado,Tatiane B Coitinho,Pedro H R Cerqueira,Laerte D Cassoli,José C F Pantoja

doi:10.5424/sjar/2016144-9923

Abstract

Two experiments were conducted to verify whether the time of day at which a milk sample is collected and the possible carryover in the milking system may affect pregnancy-associated glycoproteins (PAG) levels and, consequently, the pregnancy test results in dairy cows. In experiment one, we evaluated the effect of time of day at which the milk sample is collected from 51 cows. In experiment two, which evaluated the possible occurrence of carryover in the milk meter milking system, milk samples from 94 cows belonging to two different farms were used. The samples were subjected to pregnancy test using ELISA methodology to measure PAG concentrations and to classify the samples as positive (pregnant), negative (nonpregnant), or suspicious (recheck). We found that the time of milking did not affect the PAG levels. As to the occurrence of carryover in the milk meter, the PAG levels of the samples collected from Farm-2 were heavily influenced by a carryover effect compared with the samples from Farm-1. Thus, milk samples submitted to a pregnancy test can be collected during the morning or the evening milking. When the sample is collected from the milk meters, periodic equipment maintenance should be noted, including whether the milk meter is totally drained between different animals’ milking and equipment cleaning between milking is performed correctly to minimize the occurrence of carryover, thereby avoiding the effect on PAG levels and, consequently, the pregnancy test results. Therefore, a single milk sample can be used for both milk quality tests and pregnancy test.

Highlights

The early and accurate detection of the reproductive status is an indispensable tool in optimizing the productive and reproductive processes essentials in dairy herds, as the profitability of this activity mainly influences milk yield and, the reproductive rates of these animals (Whitlock & Maxwell, 2008; Green et al, 2009; Lawson et al, 2014)
Two experiments were conducted to verify whether the time of day at which a milk sample is collected and the possible carryover in the milking system may affect pregnancy-associated glycoproteins (PAG) levels and, the pregnancy test results in dairy cows
The first experiment was conducted to evaluate the effect of collection time of the milk sample on PAG levels and, on the results of the pregnancy test

Summary

Introduction

The early and accurate detection of the reproductive status is an indispensable tool in optimizing the productive and reproductive processes essentials in dairy herds, as the profitability of this activity mainly influences milk yield and, the reproductive rates of these animals (Whitlock & Maxwell, 2008; Green et al, 2009; Lawson et al, 2014). The commonly used techniques for detecting the reproductive status of cows involve rectal palpation and transrectal ultrasonography (Silva et al, 2007; Whitlock & Maxwell, 2008; Lawson et al, 2014) The application of these techniques requires trained and qualified professionals to ensure proper execution (Han et al, 2012). 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 (Løvendahl & Bjerring, 2006; Quist et al, 2008; 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

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