Review: Sugar beets as a substitute for grain for lactating dairy cattle

Dairy cows are customarily given grains and highly digestible byproduct ingredients as additions to forage to support milk production. In many parts of the world growing seasons are short, and the grain crops that can be grown may not provide adequate yields. Sugar beets, on the other hand are relatively hardy, and dry matter yields surpass the yields of most grain crops. There are however, perceptions that beets may not be suitable as a feed ingredient due to the fact that the storage form of carbohydrate is sugar rather than starch. With little analytical support, sugar has been rejected in many feeding programs with the view that sugar reduces rumen pH, fiber digestion and microbial yield. This review explores available facts revolving around these concerns. Information regarding the feeding of sugar beets is provided and the use of sugar beets as a partial replacement for grain is proposed.

Effects of increasing rates of molasses supplementation and forage quality on the productivity of steers

This study consisted of several experiments that investigated the feed intakes, and growth rates of steers fed low-quality Angleton grass (Dichanthium aristatum) supplemented with urea and sulfur (dry matter (DM) digestibility, 45%) and medium-quality Rhodes grass (Chloris gayana) (DM digestibility, 58%) when fed either alone or with molasses mixtures (MM, molasses plus nitrogen and phosphorus). Some digestion characteristics of the basal forage diets were also measured. Addition of MM at 1.2 times calculated maintenance energy requirements (M) was associated with about a four-fold increase in microbial crude protein production and a 42% decrease in neutral detergent fibre digestibility. In the first growth experiment, MM at 0M, 0.45M, 0.90M and 1.35M was offered and mostly consumed before forage was offered ad libitum. The initial mean weight of the steers was 240 kg. Consumed MM comprised 0%, 21%, 38% and 50% of the total DM intake for Angleton grass and 0%, 19%, 33% and 41% for Rhodes grass. The corresponding mean liveweight (LW) gains were 0.06, 0.31, 0.73 and 0.83 kg/day for steers fed Angleton grass and 0.61, 0.90, 1.02 and 1.13 kg/day for steers fed Rhodes grass. In a second experiment, MM was offered to steers (initially 370 kg) at the same time as forage. Offered MM comprised 0, 0.40, 0.80 and 1.20M of the calculated metabolisable energy (ME) requirements for maintenance. Consumed MM comprised 0%, 20%, 36% and 48% of the total DM intake for Angleton grass diets and 0%, 18%, 28% and 32% for Rhodes grass diets. The corresponding mean LW gains were –0.09, 0.36, 0.58 and 0.70 kg/day for Angleton grass diets and 0.63, 0.67, 0.80 and 0.94 kg/day for Rhodes grass diets. The method of presentation of the MM had only minor effects on the amounts and proportions of forage and the MM consumed and on the LW gains of the steers, expressed as g/kg0.75 LW per day to allow for differences in initial LW between experiments. Using modifications to the scheme of SCA (1990) to predict maintenance energy requirements, a value for efficiency of use of ME for growth was calculated from growth rates of steers fed Rhodes grass. When MM with an assumed content of 11 MJ ME/ kg DM was added to the forage diets, the calculated ME content of forage decreased with increased MM content, consistent with depression of fibre digestion. The relationships for the separate experiments indicated that at 50% MM in the diet, the magnitudes of the depression in the calculated ME content of the forages were 20–37% for Rhodes grass and 18–33% for Angleton grass.

Effect of varying the proportion of molasses in the diet on intake, digestion and microbial protein production by steers

The present experiment was conducted to determine the efficiency of microbial protein production in the rumen and intake by cattle fed high-molasses diets. Intake and microbial crude protein (MCP) production were measured along with the concentration of rumen ammonia-nitrogen (N) and volatile fatty acids (VFA), pH and the rate of digestion of roughage in the rumen. Eight Brahman crossbred steers weighing 211 ± 19.3 (± s.d.) kg were used in a double 4 × 4 Latin square design. Steers were allocated to one of four total mixed rations: control (pangola hay only), 25M (25% molasses/urea mix + 75% hay), 50M (50% molasses/urea + 50% hay), and 75M (75% molasses/urea + 25% hay). The production and efficiency of production of MCP (EMCP) of the diet increased quadratically as the level of molasses in the diet increased. The EMCP from the molasses/urea mix was estimated as 166 g MCP/kg digestible organic matter (DOM), a relatively high value. Intake of dry matter (DM) and DOM increased quadratically, reaching a peak when molasses was ~50% (as fed) of the ration. Digestibility of DM increased quadratically and that of neutral detergent fibre decreased linearly with increasing level of molasses in the diet. Molasses inclusion in the diet had no effect on rumen pH, ammonia and VFA concentration in the rumen fluid, plasma urea-N, urine pH or ruminal fractional outflow rate of ytterbium-labelled particles and Cr-EDTA. It was concluded that a diet with a high level of molasses (>50%) and supplemented with adequate N had high EMCP, and that low MCP production was not a factor limiting intake or performance of cattle consuming high-molasses diets.