Predicting lactation yields in dairy buffaloes by interpolation and multiple trait prediction

Abstract

Milk recording systems for dairy buffaloes in the Philippines suffer from missing or irregular fat and protein test intervals; hence a suitable method to predict lactation yield is needed. The test interval method was compared with methods that incorporate information on standard lactation curves using Wilmink's (Wil) or Wood's (Wood) function. The latter two methods were also evaluated using a multiple trait procedure with covariances between milk, fat and protein yields, MTP-Wil and MTP-Wood, for 305D yield prediction. For this purpose, 1700 lactation records of dairy buffaloes from seven herds located in the north and south of the Philippines were used. All lactations have daily milk yields and most also have monthly fat and protein test day yields. Accuracy of predicting 305D milk, fat and protein yields were evaluated using ≥9 test day yields (≥9TD) of complete lactations, part lactation of varying lengths and lactations with missing tests with varying intervals between tests. The five methods were compared based on mean squared error and correlation between the predicted and true 305D yield. Prediction of 305D milk and protein yields was equally precise among the five methods when ≥9 test day yields were used. In general, MTP-Wil had slightly better precision compared with TIM and Wil methods in extending part lactations to 305D yields for all 3 traits. The use of Wood's function to model the lactation curve resulted in large prediction error when extending yields to 305D from short lactations. The methods, MTP-Wil and MTP-Wood, which utilize information on covariances between traits had slightly better performance and are able to handle missing tests and longer intervals between tests better than other methods. Fat and protein 305D yields can be predicted using a single test with almost similar accuracy using ≥9TD yields provided that complete milk test day information is available. Overall, MTP-Wil performed better than the other methods and is more applicable in situations where missing tests or irregular test intervals are frequently encountered in milk recording system.