© 2006 Japanese Society of Animal Science Animal Science Journal (2006) 77, 532–537 doi: 10.1111/j.1740-0929.2006.00382.x Blackwell Publishing AsiaMelbourne, AustraliaASJAnimal Science Journal1344-3941© 2006 Japanese Society of Animal ScienceOctober 2006775532537Original Article PERSISTENCY IN GOATSA. PALA and T. SAVAΣ Correspondence: Akin Pala, Department of Animal Science, Canakkale Onsekiz Mart University, Canakkale, Turkey. (Email: akin@comu.edu.tr) Received 11 November 2005; accepted for publication 28 February 2006. ORIGINAL ARTICLE Relationships between daily, morning, evening and peak yield and persistency in Turkish Saanen goats Akin PALA and Türker SAVA Department of Animal Science, Canakkale Onsekiz Mart University, Canakkale, Turkey ABSTRACT A matrix of persistency values is given instead of one value of persistency or persistency values based on succeeding test days. Overall, the persistency matrix of morning milk had higher values than the persistency matrix of evening milk. As the distance between the test days increased, the correlations dramatically decreased. The effects of morning milk yield b = 0.23 (P < 0.01) on standard deviation of morning and evening milk yield and on peak the milk yield was higher com- pared to the evening daily milk yield b = 0.03 (P = 0.05) and the total daily milk yield 0.10 (P < 0.01). Increased persistency means that the lactation curve may be flatter. Since the peak value of morning milk (1597 mL) was lower than evening milk (1799 mL), and morning milk was more persistent than evening milk, morning milk can be said to contribute more to the flatness of the lactation curve. Overall, the morning milk volume (938 mL) was larger than the evening milk volume (835 mL). A 3D plot of peak milk versus morning and evening milk yield indicated that increasing the evening milk yield increases the peak yield while the morning milk yield holds the peak value lower and the curve stable. Key words: evening milk, morning milk, peak value, persistency, Turkish Saanen goats. S ¸ INTRODUCTION Increased persistency of lactation may result in great benefits for the dairyman and flattening the declining portion of the lactation curve promotes more efficient lactation (Capuco et al. 2003). This may be achieved by a lactation curve with a lower peak value. Lactation curves with lower peaks may be more persistent and the overall milk yield may be larger in more persistent lactations. Research (Canadian Dairy Network 2004) has shown that higher persistency is mainly due to later and lower peak yields. However, Calus et al. (2005) reported a high correlation of 0.84 between persistency and peak milk yield. Norman et al. (1999) noted that majority of the US cows on test are enrolled in an AM–PM plan in which the intervals between tests have increased. As persis- tency increases, the number of tests required decreases (Pala & Sava 2005). Accounting for covariances among test day milk yields in dairy cows, Ali and Schaeffer (1987) sug- gested a regression model to describe the curve of the s ¸ lactation and demonstrated the advantage of this over other models, including the model by Wood (1967). Based on this work, Ptak and Schaeffer (1993) used single test day records as repeated measurements and suggested factors to model the curve of the lactation. The compound symmetry covariance structure, which has constant variance and constant covariance, results in a single estimate of persistency (Pala & Sava 2005). More complicated covariance structures such as unstructured, autoregressive or ante-dependence covariance require more data to converge but they also require fewer assumptions and the results are more reliable. Persistencies of morning, evening and total daily milk yields were calculated using a first order auto- regressive moving-average covariance structure. The s ¸