Influence of Season and Year of Calving , and Parity Order on the Lactation Performance of Kenana × Friesian Crossbred Dairy Cows Reared under Intensive System

Abstract

Two experiments were carried out to investigate the effects of season of calving, year of calving and parity order of Kenana × Friesian crossbreed cows on milk yield and lactation curve components using the model (y=an b .e -cn ). The evaluation of the udder measurements of crossbreed dairy cows in the Sudan was also aimed. The study was carried out in Kafori Military Corporation Farm for Animal Production. The first experiments concerned with milk production performance (total milk yield, lactation length, persistency index) and lactation curve components which include: initial milk yield, rate of increase to the peak yield, rate of decrease from the peak yield, the peak yield of week, the peak yield and the persistency of lactation curve. The data were extracted from the farm records of the period between 2000 to 2006 years. The records were arranged according to season of calving into summer season (March to June), wet season (July to October) and winter season (November to February). The data were also classified in to 7 year groups (one year for each group). The records were also grouped into their parity order (group) parities. The second experiment concerned with the investigation of the correlation between total milk yield and udder measurements. Cows of the farm were classified according to their number of parties (1-8 parities). The cows were also grouped in to three lactations stage groups: early lactation stage, mid lactation stage and late lactation stage. The milk yield and udder measurements were taken before and after each milking (morning and evening milkings). The parameters of udder measurement were: udder circumference, udder length, udder width, fore udder depth, hind udder depth and udder capacity. The data for the first experiment were test by 3 way analysis of variance to examine the significant of effects of year and season of calving and the cow’s parity order on the milking performance traits and the lactation curve xicomponents. The data of the second experiment were tested also by (3 way analysis) of variance to test the significance of effects of cows' parity order, the stage of lactation and time of milking on the udder measurements and milk yield. The regressions of milk yield on the different udder measurements were also tested. The mean total yield of the crossbred Kenana X Frisian was 5078.47 ± 1366.24 kg, lactation of 27% coefficient of variation. The lactation length was 389.22 ± 42.81 days of 11% coefficient of variation, the weekly peak milk yield was 151.31 ± 42.12 kg/week of 28% coefficient of variation and the persistency was 61.25 ± 9.26% of 15% coefficient of variation. The results also revealed that season and year of calving and parity order had no significant effect on all of the studied lactation performance traits and the lactation curve components except the total milk yield that was observed to increase significantly with parity order and the persistency of the lactation curve that was significantly low in the 8 th parity order. Experiment two results showed that the udder measurements were significantly higher before the morning milking than before the noon time milking. The early stage of lactation showed the highest udder measurements whereas the lowest ones were observed at the late stage of lactation groups. All of the studied udder measurements were found to increase significantly with parity order of the cows. The study concluded that the managerial system practiced in the farm relief the cow productivity from the seasonal stress; however the annual changes in these systems as well as the age of cows should be considered when evaluating the milking performance of these crossbred cows. The study also concluded that when evaluating the udder shape and measurements factors such as period between milkings, stage of lactation and cows' age should be put into consideration. It is worth mentioning that the length of the udder before milking is the most udder measurement variable with milk yields. Therefore it can be used with good xiiaccuracy to predict milk yield. Addition of other measurement into multiple regression or use udder capacity may not add more precise prediction.