EFFECT ON FEED INTAKE, MILK PRODUCTION AND MILK COMPOSITION OF HOLSTEIN COWS BY REPLACING MAIZE GRAIN WITH WHEAT IN TOTAL MIXED RATIONS.

Discipline: Nutrition/feeding;

The majority of dairy farmers in the Swartland region of the Western Cape feed total mixed rations (TMRs) to lactating dairy cows. Roughages used in the TMRs include lucerne hay (LH), oat hay (OH) and various cereal crops that are conserved as silage, wheat straw or wheat straw treated with ammonia. Combinations of these roughages are often fed. The energy in TMRs is provided by including grains such as maize, barley, wheat and cereal crop by-products such as wheat middlings. However, maize remains the primary source. 

Wheat, a winter cereal, is the main grain crop in the Western Cape. Seasonal summer droughts in the maize-producing areas can cause maize shortages for dairy farmers there, forcing them to rely on imported maize. The cost of home-produced wheat grain could be lower than maize grain, largely owing to high transportation costs associated with importing maize grain to the Western Cape. Thus, it would make economic sense to rather use wheat grain. However, it is not commonly used. The aim of this study, therefore, was to determine the effect of wheat grain replacing maize grain in TMRs on feed intake and milk yield parameters of lactating Holstein cows using different roughages, that is, LH, OH and a 50 : 50 combination of LH and OH.

Three feeding trials were conducted using different roughages, namely lucerne hay (LH), oat hay (OH) and a 50 : 50 mixture of LH and OH. For each trial, five TMRs were formulated in which the maize to wheat grain ratios were 100 : 0, 75 : 25, 50 : 50, 25 : 75 and 0 : 100 to contain at least 170 g crude protein (CP)/kg and 11.1 MJ ME/kg dry matter. In each experiment, 10 randomly selected Holstein cows were fed the five diets according to a double 5 x 5 Latin square experimental design.

In the trial using LH as roughage source, dry matter (DM) intake declined with increasing wheat percentage, so did fat percentage of milk, and therefore fat yield was lower in the treatment containing only wheat as an energy source. In the trial using a 50 : 50 mixture of LH and OH as roughage source, the fat content of milk increased with increasing levels of wheat in the diet. No differences were observed in any of the other milk parameters such as protein, lactose and MUN, by increasing the wheat inclusion levels in the diets. Milk yields, however, tended to be higher with the OH diets than with the LH diets, with the 50 : 50 combinations in-between. Thus, the differences observed were due to roughage source and not due to wheat vs maize and therefore it can be concluded that maize can be successfully replaced by wheat in TMRs in the Swartland.

Reference: 

Muller, C.J.C., Botha, J.A., Calitz, F. & Lehmann, M., 2014. Effect on feed intake, milk production and milk composition of Holstein cows by replacing maize grain with wheat in total mixed rations. SA J. Anim. Sci. 44, 271-279.