Dietary supplementation is an established strategy for improving performance across a variety of parameters in livestock. However, its effect on reproduction in ruminants is less known. A recent study looked at using live yeast as a means of improving the breeding performance of milking cows.
Agriculture, and particularly farming of ruminants, is facing serious challenges in terms of the environment, animal welfare and economic viability. Such considerations must guide strategic and technical choices, including the optimisation of diet to help improve and manage production. Production and quality in ruminants are partly determined by ruminal fermentation and feeding its rumen microflora. However, while microbial digestion does take place naturally in the rumen, it is possible to improve its efficiency by improving rumen fibrolysis and microbial synthesis. By carefully choosing the quality and quantity of feed, it is possible to adapt the diet to the animals’ needs and to production objectives.
In Europe, live yeasts, as probiotics, fall within the regulatory scope of feed additives. This beneficial microscopic fungus, employed for many years in the baking, brewing and wine industries, has also made its mark in human and animal nutrition and health. They are usually marketed in viable form and have high levels of living cells (>109 CFU/g). By stabilising the ruminal pH in animals fed on diets with a high energy content, which can cause ruminal acidosis, live yeast is known to improve feed efficiency. Daily live yeast intake can impact animal performance such as improving body weight and average daily gain (ADG) in beef cattle. In dairy cows, probiotic yeasts, in particular Saccharomyces cerevisiae, are used widely. Studies have examined their effect on digestion, metabolism and performance and is shown to increase milk production by an average of 1.2 kg/cow/day (2006; Desnoyers et al., 2009). In addition, Salvati et al. (2015) demonstrated the beneficial effects of live yeast in controlling an animal’s homeothermy and maintenance of milk production under heat stress conditions. However, little research has been carried out on the effect of yeast supplementation on the reproductive performance of dairy cows, even though efficient utilisation of energy and protein from feed is a determining factor in improving reproduction in high-producing dairy cows. Moreover, although there is a consensus on the nutritional effects of live yeast on milk production, the consequences on breeding performance is unclear. Chapaux et al. (2004) argue that an increase in milk production has been accompanied by a decrease in fertility, the first perhaps being the cause of the second. This recent field study shows the impact of supplementation with probiotic yeast (Saccharomyces cerevisiae Sc47-CNCM I-4407) on reproductive performance in dairy cows (Julien et al. 2017)
15 dairy farms were selected for the study. Situated in the Hauts-de-France region of France, most of these farms were already using artificial insemination (AI). Inclusion criteria included a minimum of 40 dairy cows (at least 47 first AI’s or 76 AI’s in total over 1 year) that had not used probiotics in the 2 milking years preceding the study. Cows received probiotic supplementation (5 g/cow/day) with yeast (Actisaf®, Saccharomyces cerevisiae Sc 47-CNCM I-4407, 1.1010 CFU/g, Phileo Lesaffre Animal Care) by means of a nutritional feed (Rimiflor+, 50 g/head/d, Société Difagri) included in the daily ration. The study was conducted over 13 months: a 4-week period of adaptation to the product (the effect of probiotic yeast generally appears in animals after 3 weeks from initiation), followed by a one-year observation period (1 Oct 2016 to 30 Sep 2017).
Each farm was monitored by an insemination technician twice a month and twice during the trial. Measures included number of cows and delivery quantities to ensure the correct distribution in terms of quality and quantity of product. A report on the composition of each ration was established along with an average ration over the study period. All interventions (prophylaxis, hoof trimming, etc.) and changes in farm practices (buildings, milking, monitoring, etc.) were recorded. Although the feeding system was not a selection criterion, most were generally intensive livestock farms using corn silage (77% of total forage DM on average), beet pulp included as a feed concentrate (18% of total feed concentrate DM) and a little grass forage (hay, grazing, grass silage). An AI was considered to have resulted in a pregnancy and was recorded as a pregnant or fertile AI (AIf) if it resulted in calving within 270-296 days. Alternatively, if no calving was observed over this period, then it was considered an AIf (successful conception) if the female was declared pregnant by ultrasound (from 30 days post-insemination) and confirmed pregnant by palpation at more than 90 days post-insemination.
The analysis was based on 2,421 Holstein females inseminated with a total of 4,230 doses of conventional Holstein semen at 14 farms (data from one farm were removed due to a change in management of herd reproduction) over 3 successive milking cycles (Figure 1), i.e. 2 reference years and 1 year of observation in which cows received supplementation with probiotic yeast. There were no specific rules on how the cows should be bred after calving, so data processing took into account the variability of inter-herd practices.
The improved performance of animals receiving live yeast may be explained by their ability to use feed more effectively. Regarding fibre degradation, Marden et al. (2008) reported that yeast probiotic Sc 47supplementation in dairy cows with digestive disorders, such as subclinical ruminal acidosis, significantly increased total fibre digestibility from 30% to 42%. An improvement in the redox (oxidation-reduction potential) values in the rumen is observed in high-producing dairy cows receiving an acidogenic diet supplemented with live yeast (Marden et al., 2008). According to Pinloche et al. (2013), improvement in rumen redox values is linked to activity of rumen bacteria. The improvement in rumen reducing conditions is thought to promote the activity of anaerobic bacteria such as fibrolytic and lactate-utilising bacteria, leading to fibre becoming more digestible (Marden, 2007). In addition, Jiang et al. (2017) confirmed several rumen bacterial groups respond to live yeast supplementation, underlining a link between rumen microbial composition and animal performance.
Julien et al. (2017) demonstrated the success rate at the first AI is generally better in dairy cows receiving a high dose (10.1010 to 20.1010 CFU/cow/day) of probiotic yeast (strain Sc 47) in the 6 weeks around calving time. Better feed efficiency and hence a lower energy deficit when beginning lactation may improve reproductive function. Production and reproduction compete for the animal’s energy intake (Courtheix, 2016), so use of feed additives may help control environmental parameters, including food efficiency, to maximise the animal’s genetic potential.
In this new study, no major changes were observed in the reproductive parameters of primiparous cows, although there was a decrease in the percentage of AI’s above parity 3, which was also seen in multiparous cows. It may be that a difference between the periods studied was due to the smaller number of primiparous cows compared to those that were multiparous. But more likely is that yeast probiotics has a stronger effect on reproductive performance in multiparous cows, due to higher milk production, higher energy demand and higher risk of negative energy balance. These same trends are observed in terms of milk performance (Figure 4). On the other hand, there is an improvement in the AI success rate in multiparous cows of 34 to 38% on average and this improvement is linked with an increase in the success rate of the first AI (31 to 36% on average (Figure 2)). As a result, the number of inseminations required to achieve pregnancy was significantly lower when cows were receiving probiotic yeast compared to the reference period: an average of 3.1 to 2.7 inseminations (Figure 3).
At this stage, it is difficult to give the main reason for this improvement (the general condition of the animal or a direct effect of the probiotic yeast). Nevertheless, Allbrahim et al. (2010) demonstrated that the pre-ovulatory oestradiol peak and size of the first ovulatory follicle in early-lactation dairy cows tended to increase following supplementation with Saccharomyces cerevisiae probiotic yeast. Therefore, both direct and indirect effects on breeding performance are possible. In addition, the supplementation with yeast probiotic Sc 47 of multiparous animals coincided with a tendency for better fat and protein production: 2 246 and 2 360 g/d (Figure 4), and numerically higher milk production of 1.5kg of milk per cow and day, which rules out the possibility of the productive function being less demanding on the animal in favour of reproductive function.
In conclusion, this field study confirms the beneficial effects of optimising the feed of dairy cows to improve their reproductive performance. Use of daily supplementation with the live yeast used in this study at 14 farms over a year resulted in a significant improvement of 4 points on average in the success rate of AI and of 5 points in the success rate of first AI in multiparous dairy cows. The number of inseminations required to obtain a pregnancy was reduced from 3.1 in the reference period to 2.7 in the probiotic yeast supplementation period. In parallel, the fat and protein yield by these same animals tended to improve between the 2 periods, demonstrating that it is possible to combine milk performance and maintenance of an effective reproductive system.
References are available on request.