Changes in milk production in relation to changes in feeding and management practices in dairy herd improvement association herds.

All Holstein herds of over 20 cows which had automated data processed dairy herd improvement association (DHIA) records from Cornell laboratory for two consecutive years from 1960 to 1964 were used to determine production, feeding, and management changes. The average number of herds for the four 2-yr comparisons was 2,688, 60% in New York and the remainder in neighboring states. Results in the two locations agreed. The yearly changes and standard deviations of changes per cow for the New York herds were milk production, + 157 ± 400 kg; grain feeding, + 88 ± 241 kg; succulent forage, + 0.13 ± 1.76 metric ton; dry forage, -0.04 ± 0.50 metric ton; net energy from pasture, -0.60 ± 6.]0%; herd size, + 1.8 ± 5.65 cows; days in milk, + 0.24 ± 2.93%. Only two factors were closely correlated with change in milk production -change in grain fed and change in per cent days in milk. Multiple regression analysis, using the six factors above, indicated that a change of I kg in grain feeding resulted in a change of 0.84 kg of milk and a 1% change in days in milk gave a change of 45 kg of milk. The objective of this study was to determine the relationship of changes in DHIA production and changes in feeding, particularly the amounts of concentrates and forages fed. For the past several years there has been increased emphasis on feeding more grain to lactating cows. Excellent reviews (2, 4-6) have indicated a favorable but variable response to more liberal grain feeding. One of the earlier, extensive ~npnt-output studies, that of Jensen et al. (3) with only moderate levels of production, found that at the lowest level of concentrate feeding one additional kilogram of concentrate resulted ~n a 1.7 kg increase in FCM, whereas at the highest level only a 0.6 kg increase resulted. These Received for publication Ju]y 27, 1965. same trends have, in general, been reported by the more recent work with higher producing cows and higher levels o£ feeding. A major reason explaining why the requirement is increased at high levels o£ feed intake has been reported by Reid et al. (7) and supported by Brown (1). Their explanation is that, as the level of feeding increases, the digestibility of the diet decreases. The point of optimum level o£ grain feeding is where the last increment of grain fed still makes a profit in terms of milk production. Experimental Procedure Data for this study included all Holstein herds of 20 or more cows having automated data processing of their records for two or more consecutive years during the five test years ending April, 1960, to April, 1964. New York herds and out-of-state (O.O.S.) herds processed in the Cornell laboratory were analyzed separately. As shown in Table 1, the number of New York herds ranged from 890 to 2,133 and the number of O.O.S. herds from 669 to 1,482. A second phase of this study was to examine the year-after-year ehanges that dairymen make in grain feeding or in milk production. This analysis used data from all herds on test all five of the years. The herds were grouped according to the changes they made during the initiM year; then the changes made in each subsequent year were calculated. Results and Discussion Table 1 shows the number of herds, average production, and feed intakes for each comparison of two consecutive years. Average changes made from one year to the next are given in Table 2. The change in milk production from Table 2 for 1960 to 1961~ when added to the average production given in Table 1 for 1960, does not give the average production for 1961 in Table 1. The same is true of the other factors. For example, the 890 New York herds produced 5,330 kg of milk in 1960 (Table 1). They increased their production 147 kg (Table 2)so that their production in 196] was 5,477 kg. For the ]961-1962 comparison there were 1~377 herds which started out with an average pro-