TY - JOUR AU - Randel, Paul F. PY - 1990/07/01 Y2 - 2024/03/28 TI - Supplemental concentrates with four levels of crude protein for grazing Dairy Cows JF - The Journal of Agriculture of the University of Puerto Rico JA - JAUPR VL - 74 IS - 3 SE - Articles DO - 10.46429/jaupr.v74i3.6661 UR - https://revistas.upr.edu/index.php/jaupr/article/view/6661 SP - 281-292 AB - <p>Four treatments (T<sub>1</sub> through T<sub>4</sub>), based on pelleted concentrates varying in as fed crude protein (CP) contents (10.8, 12.2, 13.4, and 15.3%, respectively), but theoretically isocaloric (1.67-1.70 Mcal net energy/kg), were compared for efficacy as pasture supplements. Eighteen multiparous cows began the experiment individually not later than 8 weeks postpartum. Five were assigned to T<sub>1</sub> and T<sub>3</sub> and four to T<sub>2</sub> and T<sub>4</sub>. Daily concentrate allowances were according to milk production, but 4.5 kg was set as the arbitrary minimum. Nocturnal rotational grazing was in 12 0.5-ha paddocks of little fertilized, heterogeneous, gramineous swards, which fluctuated in quality from adequate to marginal during 11 1/2 months of experimentation. Cows assigned to the four treatments in order produced 21.3 ± 3.0, 22.5 ± 4.4, 20.3 ± 2.5, and 20.4 ± 4.5 kg of milk daily during the 5 days before commencing the experiment, and 14.4 ± 1.2, 16.8 ± 3.9, 15.2 ± 2.4 and 14.2 ± 2.4 kg during the 32 weeks of experimentation. Although treatments did not differ significantly (P&gt;.05) over-all, T<sub>1</sub> dropped in daily production by 2.7 kg during the initial 4-week interval and persistency decreased in high-producing cows; T<sub>2</sub>&nbsp;also caused a large early decline in production, but superior persistency thereafter. Mean milk fat percentages were 2.78 ± .49, 2.68 ± .44, 2.88 ± .33, and 3.17 ± .37 for 7, through T<sub>4</sub>. Early depression of milk fat was probably due to high concentrate and inadequate fiber intakes. Concentrate intake ranged from 5.82 kg in T<sub>4&nbsp;</sub>to 7.1 0 kg in T<sub>2</sub>&nbsp;over 32 weeks; milk/concentrate ratio ranged from 2.33 in T<sub>3</sub>&nbsp;to 2.45 in T<sub>4</sub>. Only in T<sub>1</sub> was appreciable liveweight (20 kg) temporarily lost early in the experiment. Concentrates containing 13 to 14% CP can be tentatively recommended as supplements to pastures of adequate quality, when fed to meet energy requirements of cows producing up to at least 20 kg of milk daily.</p> ER -