Varying energy levels for lactating cows under tropical conditions
2001
Trung, L.T. | Ordoveza, A.L.
The experiment consisted of two trials. In each trial, nine lactating cows (Holstein x Red Sindhi) were used in a completely randomized design, to study the effects of varying dietary energy body weight maintenance, milk production, milk composition, feed efficiency, physiological responses, and income over feed costs. Feeding period was divided into standardization (two weeks), preliminary (two weeks), and comparison (twelve weeks) periods. Three different rations were given to the three respective groups of cows, supplying 20 percent below the US National Research Council (USNRC) energy requirements (Ration A); 100 percent National Research Council (NRC) energy requirements (Ration B); 30 percent above the NRC energy requirements (Ration C). Protein intakes were maintained at a constant level for the three groups. Changes in weight expressed as percentage of initial body weight were -6.47 percent, -3.58 percent, and -0.92 percent for cows on rations A, B, and C, respectively. Differences between treatment means were significant (P0.05). Adjusted daily 4 percent fat-corrected milk (FCM) production of the cows on rations A, B, and C was 4.58, 5.10, and 6. 90 kg, respectively. This was found to be significantly (P0.01) greater in favor of cows on ration C than those on other treatments. The differences in terms of milk fat content and total solids were not significant. However, the means for protein and solids-non fat contents of the cows on ration C were significantly higher than the values obtained on the other two rations (P0.05). No significant differences were found in feed efficiency (kg total digestible nutrients (TDN)/kg FCM), body temperature, and pulse rate. Animals on rations B and C had higher (P0.01) respiratory rate than those on ration A. Income over feed costs was significantly greater in favor of C over A (P0.01) and B (P0.05). It would appear that, under conditions of this study, energy requirements of the stall-fed lactating cows are far above the USNRC standard. However, to draw a valid conclusion as far as energy and protein requirement for dairy cattle are concerned, further experimentation is needed to support the findings above.
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