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Nutritional Evaluation of Permanent Pastures during the Summer Months with Lactating Cows¹

Dairy Science Department, Louisiana Agricultural Experiment Station, Baton Rouge

ABSTRACT

The lignin, crude protein, and gross energy contents of herbage, digestibility of herbage, the pasture quantity and quality scores, and milk production were used to evaluate permanent pastures during the entire growing season from April to September.

Cows received permanent pasture as the sole source of forage, plus a concentrate allowance based on individual production. A positive control group of cows fed an optimum diet of good-quality alfalfa hay and grain indicated normal decline in production as lactation progressed.

Very low significant correlations were obtained between the measure of milk production and pasture quality score and crude protein in herbage. Only 3.7 to 4.9% of the variations in milk production was due to regression on the independent variables.

The digestibility of pasture herbage was higher during the early part of the growing season (April to May), followed by significant decline (P < .01) during mid-summer (June to July), and then a slight increase in the later part of August.

Highly significant positive correlations were obtained between quality score and crude protein, quality score and gross energy, and between crude protein and gross energy; whereas, those between quality score and mean daily temperature, and quality score and lignin were negative at P < .01. These variables were highly correlated with herbage digestibility.

¹ The data are from a thesis presented by the senior author to the graduate faculty of Louisiana State University in partial fulfillment of the requirements for the Ph.D. degree.

² Present address: Dairy Training and Research Institute, Forage Husbandry Division, College, Laguna, Philippines.

³ Present address: Middle Tennessee State College, Murfreesboro, Tennessee.