Effect of level and frequency of maize supplementation on the utilization of low-quality grass hay by beef cows

Abstract

Twelve Hereford cows and four ruminally cannulated Hereford × Angus heifers were used in four simultaneous 4 × 4 Latin squares to evaluate the effect of level and frequency of maize supplementation on the digestibility and intake of low-quality grass hay. Maize supplements were fed at two levels (1.4 or 2.0 kg day −1) and two frequencies (daily or twice the daily amount on alternate days) in a 2 × 2 factorial arrangement of treatments for a 56-day trial. Grass hay (5.0% crude protein, 46.2% acid detergent fiber) was coarsely chopped (5-cm screen) and offered free choice. Interactions between level and frequency of maize supplementation were not significant ( P > 0.10). Increasing maize supplementation from 1.4 to 2.0 kg day −1 decreased ( P < 0.01) hay organic matter (OM) intake, and digestibility of hay OM and all fiber constituents. Supplementation frequency did not affect ( P < 0.59) hay OM intake. Alternate day supplementation, however, tended to decrease digestibilities of total ( P < 0.20) and hay ( P < 0.23) OM which lowered ( P < 0.03) digestible OM intake by an average of 222 g day −1. For heifers fed 4.1 kg on alternate days, ruminal pH was lowest (< 6.25 for 12 h) on feeding days, but highest on non-feeding days. Ruminal ammonia concentrations peaked at 3 h post-supplementation, but remained < 1.0 mg dl −1 until the subsequent feeding. Thus, low ruminal ammonia concentrations of cows supplemented on alternate days may have limited the favorable effects of increased ruminal pH on cellulolytic activity. Decreased ( P < 0.13) total volatile fatty acid concentrations coupled with lower digestible OM intake implies that cows fed maize supplements on alternate days utilized their diet less efficiently. Consequently, beef cattle producers should attempt to feed small quantities of maize supplements on a daily basis.