Effects of different feeding systems and sources of grain on lactation characteristics and milk components in dairy cattle

The objective of this study was to evaluate the effect of two different feeding systems and of four different energy sources (Grain diet) on lactation characteristics and milk composition of dairy cattle. A total of 8,808,798 test-day records from 566,736 Holstein cows in 5,183 different herds, and 416,883 test-day records from 26,973 Ayrshire cows in 652 different herds covering a period of five years were obtained from the Quebec dairy herd improvement agency (Valacta). In addition to test-day records, information on lactation, animal status, feed composition and feeding systems was also available. For both Ayrshire and Holstein cows the fixed effect of Feeding System*DIMB (Blocks of 15 days in milk) was a significant effect in predictive models of daily milk, milk-fat, protein, and lactose yields and on milk urea nitrogen (MUN) concentration. Cows served a diet prepared with a Total Mixed Ration (TMR) compared to cows served a diet in a Traditional way tended to have higher peak milk yields and appeared to have a stronger persistency after peak milk yield. TMR-fed cows also showed a tendency for higher milk-fat, protein, and lactose yields and lower MUN concentrations than Traditionally-fed ones. Significantly higher milk yields (peak to 135 days in milk) and higher milk-fat and protein yields (peak to mid-lactation) were found in TMR-fed cows compared to Traditionally-fed ones in 3rd parity Holsteins. Both milk-fat and protein-yield lactation curves of TMR-fed cows displayed a different pattern than Traditionally-fed cows. The fixed effect of the Grain diet*DIMB was found to be a significant effect in predictive models of milk and milk-protein yields of both Ayrshire and Holstein. It was also found to be a significant effect in predictive model of MUN concentration but only in 2nd parity Ayrshire. The effect was non-significant in predictive models of both milk-fat or lactose yields. A tendency for higher milk and milk-protein yields, and lower MUN values was seen when cows received Corn Grain or High Moisture Corn compared to Barley or Commercial Concentrate but no significant differences were observed. It was concluded that a tendency for higher milk and components yields can be observed when cows are fed with a TMR compared to a Traditional system