In starter feeds, high-quality soy protein makes the difference in the rumen

By Nicolas Anglade, Category Manager Ruminants, Hamlet Protein

The choice of proteins in the formulation of calf starter feeds is essential to initiate digestive function through ruminal fermentation in the right way.

1. What makes the rumen fully functional?

The distribution of solid feed is what allows the young calf that starts its life as a strict monogastric to evolve in a few weeks to a definitive status of ruminant animal. The initial phase, which couples the spectacular growth of the rumen with its launch in operation, is essential for the rest of the young ruminant's productive career. The choice of dry feed will have an impact on the rumen flora and its functioning, but also on the capacity of the rumen wall through the papillae structure to absorb ammonia and volatile fatty acids. Weaning, which marks the end of the distribution of liquid milk feed, is a point of passage that must be secured. The feeding strategy is essential to make the transition from the milk-fed phase to the post-weaning phase successful. And in this critical transition, the choice of protein source used in starter feed counts for a lot.

2. Why protein quality matters in starter feed?

The young rumen's ability to ferment the dry and fibrous ration will evolve rapidly before and after weaning. Therefore, the initial phase of fermentation must respect, as is the case in adults, a good balance between fermentable and available energy and nitrogenous matter (mostly protein).

However, we know that in the first weeks of the calf's life, due to the immaturity of the rumen, a significant amount of solid feed will escape the fermentation phase and bypass this voluminous pre-stomach without degradation. This peculiarity of the young ruminant implies that precautions must be taken. When choosing the ingredients that make up the first age feed, it is necessary to avoid or reduce the presence of ingredients potentially carrying mycotoxins or anti-nutritional factors (ANF’s) which damages to the intestine and immunity are known and documented.

One of the most universal choices when it comes to feeding protein is the use of soybean meal (SBM). It is a convenient and palatable ingredient, classically used as a protein provider in starter feeds for calves. Soybean meal is also known to be used in the monogastric feed but when it is for young piglets or birds, its inclusion is limited, and safer proteins are substituted.

Soybean ANF’s (like trypsin inhibitors, galacto-oligosaccharides, and allergen proteins) damage young ruminant digestion and gut health, and thus performance. Rumen fermentation might solve part of the problem, but the bypass fraction will carry intact ANF’s fractions to the intestine.

At Hamlet Protein, the enzymatic treatment of SBM makes it possible to considerably reduce the ANF level which makes it safe to use in feed for young animals.

3. How can the right protein choice make a difference?

For more than 30 years, Hamlet Protein has been offering concentrated soy protein to the market to secure the feed of young animals. Through a biotechnological process of enzymatic hydrolysis, soy protein is concentrated and freed of anti-nutritional factors harmful to the intestinal functioning of young ruminants.

Trials conducted at the University of Illinois in 2020 have provided a better understanding of what happens in the rumen of young calves during the 2nd month of their lives when we substitute an enzymatically treated soy protein (HP 300) for conventional soybean meal. These trials confirmed that a significant portion of the dry feed, in the order of 42 to 51 % by-passed the rumen. In addition, we were able to observe a significant and beneficial increase in microbial proteins and an equally significant decrease in the excretion of non-protein nitrogen from the rumen (figures 1A and 1B). It was also interesting to observe that, downstream of the rumen, protein digestibility in the intestine is improved when HP 300 is substituted for soybean meal (TID of 79% vs 69%). Finally, the fecal score tendency is better (1.44 vs 1.78). This is proof that soy that bypasses the rumen makes it loaded with the anti-nutritional factors that it naturally carries, which degrades the intestinal health of the young ruminant.

Figure 1 A) Duodenal flow of NPN (g/kg DMI) and B) efficiency of microbial synthesis (microbial N, g/kg CP) as measured at the duodenum of calves fed calf starters with soybean meal (SBM) or HP 300 as main protein source. a,b indicate significant differences (p<0.05).

The data of this trial were published in a peer-reviewed journal: Ansia, I., Stein, H.H., Brøkner, C., Hayes, A., Drackley, J.K. 2021. Nutrient digestibility and endogenous protein losses in the foregut and small intestine of weaned dairy calves fed calf starters with conventional or enzyme-treated soybean meal. Journal of Dairy Science. 104.

4. Market drivers and outlook

When we look at the market for feeding calves before weaning, we see that the attention of the farmer, but also of his environment, is mainly focused on liquid feed and calf milk replacer choice. Starter dry feed tends to fly under the radar. And that is a shame because the starter feed is an essential point of improvement for a successful weaning transition.

We have seen in many trials that growth performance and weaning weight are an important stepping point for the rest of the young animal's career, whether it is a heifer for milk production or a male for fattening.

In a compilation study (8 trials in universities and commercial farms between 2014 and 2019; n=743 calves; figure 2), we compared the results obtained by fully changing conventional soybean meal with HP 300 in the starter feed offered ad libitum from the first day of the trial to 2 weeks after weaning. We observed that, on average, we gain 4.9 kilograms at weaning, i.e., about 6 days of growth with an average daily gain increased by 69 grams. Feed efficiency was also improved with an average feed conversion ratio improved by 0.15 point compared to the batch of calves that received starter feed with conventional soybean meal, as ingestion of dry feed is not significantly impacted.

Figure 2 Body weight (BW), average daily gain (ADG) and feed conversion rate (FCR) change (+/-) when substituting soybean meal (SBM) in calf starter feed (CSF) with HP 300. Compilation study based on 8 trials in comparable situations (5 in commercial farms and 3 in research center). HP 300 inclusion rate: 14-24%.

When we were able to observe the growth monitoring of these animals over a longer period after the initial treatment, we found that the difference in initial growth persisted over time. If we take the case of dairy heifers, we know that heifer live weight is essential to trigger the reproduction phase and therefore the age at first calving. Gaining days of growth in the initial phase allows, by translation, to advance the age at first calving. These days of growth gained thus become profitable days of milk production that ensure a very good return on the investment done initially in formulating the starter feed with a clean and efficient source of protein like HP 300.

The initiation of fermentation functions is an important step in the start-up phase of the ruminant. The choice of protein provided by starter feeds is clearly underestimated but has a major impact on the initiation of rumination and calves’ gut health. Regarding the full life of the ruminant and the total feed intake, this little and short investment can have important impacts on productivity and health of dairy and beef herds.