The effects of stocking rate and level of supplementation with concentrate on cows grazing intensively managed tropical pastures were measured with four treatments: grazing alone at 2.5 head per ha per year (T1); grazing plus concentrate at the rate of 1 kg per 2 kg of milk irrespective of daily yield (T2); grazing plus concentrates at the rate of 1 kg per 2 kg above 10 kg daily (T3); and grazing at 5 head per ha plus concentrates at the same level as cows in T2 (T4). All three supplemented groups (T2, T3 and T4) produced significantly greater yields of milk and fat. Average milk yields (kg, M.E. basis) were 3450, 5568, 4709 and 5462 for cows on T1, T2, T3 and T4, respectively. Cows on the higher level of supplement (T2 and T4) gained significantly more weight over the lactation period than cows on T1 and T3. The effect of the supplement appears to be greatest during the early part of lactation when physiological limitations on the consumption of pasture prevent sufficient nutrient intake to supply demand. Cows on T2 produced only 105 kg more milk than cows on T4, while the expected difference, based on increased pasture availability, was over 455 kg. The reduced difference in level of production is postulated as an effect of excessive pasture growth on both intake and diet selection. While milk production was highest for cows receiving the high levels of supplement (T2 and T4), expected return per lactation in income over the cost of supplements, lime and fertilizer were greatest for T3 (medium supplement). Expected returns on a per ha basis were greatest for T4 with 5 cows per ha. Results indicate that where land costs are high, most efficient use of pasture and concentrate resources may be reached by grazing at the rate of 5 head per ha and supplementing with concentrate at 1 kg per 2 kg of milk.

Records of milk yield, fat percent, body weight, reproduction and health of 506 calvings of 362 cows were used for estimating the efficiency of utilization of tropical grass pastures by lactating cows fed on grazing alone or grazing with various types of supplement. There were seven feeding systems: grazing alone (T1); grazing plus supplement with ground maize (T2); with molasses (T3); with concentrate (T5); or with urea-molasses (T6), at the rate of 1.0 kg per 2.0 kg milk in excess of 10 kg of milk per day and of 2.5 cows per ha; or grazing plus concentrate feeding of 1.0 kg per 2.0 kg milk irrespective of milk yield at a stocking rate either of 2.5 cows (T4) or 5-0 cows (T7) per ha. All supplement systems had significantly higher yields of milk, fat and fat-corrected milk than grazing alone. Level of fat percent paralleled dependence on intake of forage. Supplement also extended days in milk. System of feeding was significant for body weight gain, time to reach peak milk yield, the level of peak yield, persistency of milk yield, days open, time from first breeding to conception, and calving interval. High levels of supplement (T4, T7) increased weight gains, time to reach peak yield, and persistency, but lowered breeding efficiency. On medium levels (T3, T5, T6), the efficiency (Meal/kg dry matter) of utilization of supplement for milk production was satisfactory, but unsatisfactory on high supplement levels (T4, T7). Supplements as high or higher than those in the grass treatments supplemented with non-protein nitrogen (urea-molasses) or crude protein (concentrate) gave a more efficient utilization than either maize or molasses. During the first 150 days of lactation, cows on grazing alone averaged 14.3 kg pasture grass dry matter intake per day, or 2.9% of body weight. Cows on low supplement (T2, T3, T5, T6) averaged 24 to 29% less; and cows on high supplement, nearly 60% less intake. Type of supplement had little influence on pasture grass dry matter (PGDM) intake. When the genetic potential for milk yield of cows exceeds 3,000 kg, supplementary feeding appears economically feasible. Even under the high levels of nitrogen fertilization employed, there was a rise in average milk yield with intakes of protein from the supplementary feed. Supplementary feeding with tropical grass pastures caused a high rate of substitution; hence, the efficiency of use of PGDM is lowered unless stocking rate is carefully adjusted.

Forty-eight lactating Holstein cows were randomly distributed on four treatments at the Gurabo Substation: T8 , grazing; T9 , grazing + 2.3 kg per day of dehydrated, whole-plant maize (Zea mays) pellets; T10, grazing+ 2.3 kg per day of Stargrass (Cynodon nlemfuensis) hay; and T11, drylot feeding of Stargrass hay + 4.5 kg per day of pelleted maize, to evaluate preserved fOrages in terms of variations in pasture quality. Grazing was at the rate of five cows per ha. Cows in all groups received concentrates at the rate of one unit of concentrate to two units of milk. The cows started on the treatments at 45 days postpartum. Analysis by covariance showed significant treatment effects in milk yield with pretrial production as the covariate. The adjusted means for daily milk yield over an 8-week period were 23.2, 23.8, 23.1 and 23.1 kg for T8, T9, T10 and T11, respectively. Treatment effects were not significant for either fat percent or body weight gain. Cows fed hay, pellets and concentrates (T11) equaled those on grazing plus concentrates (T8) in milk yield, but cows on grazing supplemented with concentrates and pelleted forages (T9) were significantly higher in milk yield. Cows on grazing supplemented with hay and concentrates (T10) were significantly lower in milk yield. The study showed that good quality pelleted forages may be used effectively in combination with pasture of hay. However, tropical grasses, cut at 45 to 55 days of age and artificially dried, have limitations in nutritive value and palatability for use in conjunction with good quality pastures.

Voluntary intake and apparent digestibility of an artificially dried tropical grass, Cynodon nlemfuensis variety nlemfuensis. was evaluated utilizing Holstein bull calves. Two regrowth ages of grass hays, 30 and 45 days, were fed to two groups of four calves each: 16 and 24 weeks old. The grass hays were analyzed for dry matter and crude protein and for fiber fractions according to Goering and Van Soest. There were no significant differences between means for voluntary intake (g/kg body weight (BW)/day) of the chemical constituents for the four calf-hay groups. However, the trend was for higher intake by the 24-week old calves fed the 30-day hay than by the other three groups. Among the 16- week old calves, there was a higher voluntary intake by those consuming the 45-day hay despite the slightly higher nutritive value of the 30-day hay. When the data were pooled across calf ages, voluntary intake of 30-day hays was greater than for the 45-day ones, although only differences in crude protein intake were significant (P < .05). Pooled across hay ages, voluntary intake by the 24-week old calves was significantly greater (P < .05) than by the 16-week old calves for dry matter and neutral-detergent fiber only, indicating that hay intake was related to reticulo-ruminal capacity. Differences in apparent digestibility were significant (P < .05) only for crude protein with the 24-week old calves fed the 30-day hay, having a greater coefficient of digestibility than the 16- and 24-week old calves fed the 45-day hay. Crude protein digestibility of the 30-day hays (pooled across calf ages) was significantly greater (P < .05) than that of the 45-day hays. Although not significant for all constituents, the values were higher for the 30-day hay than for the 45-day hay (pooled across calf ages) and for the 24- week old calves than for the 16-week old calves (pooled across hay ages).

THE FEEDING OF DAIRY CALVES WITH PANGOLA AND STAR GRASS HAYS