Dr. Alfredo J. Escribano
Head of Business Development
1. FERTILITY, THE ONSET OF PRODUCTIVITY AND PROFITABILITY
Reproduction is a prerequisite of milk production. Despite this is a basic concept, practical (at farm level) feeding management does not reflect the same. Therefore, dairymen should devote special and additional effort towards getting cows pregnant.
However, declines in fertility have been noted and reflect associations with intensification of production and higher levels of milk production (Butler, 2000; Lucy, 2001; Lean et al., 2008; Thatcher et al., 2011; Rodney et al., 2015).
Transition period (approximately 3 weeks before to 3 weeks after calving) is critical for reproduction due to NEB and the numerous metabolic processes (stress) that this provokes, thus increasing incidence of anestrus, reducing steroidogenic capacity of the corpus luteum, and altering patterns of follicular development.
Furthermore, these negative effects goes beyond the transition period and NEB, because of the long developmental lifespan of the ovarian follicle (Lucy et al., 1991).
However, due to this, adequate nutritional management during this period must embrace metabolic health and reproduction performance. In this sense, DeGaris et al. (2010) found that the risk of pregnancy increased by approximately 30% in cattle exposed to transition diets for 20 d compared with cattle not exposed.
2.WHY FATS ARE USEFUL?
Inclusion of fats in the diet during this transition period has improved reproductive performance and reduced the incidence of metabolic diseases (Thatcher et al., 2006; De Veth et al., 2009; Naik, 2013; Rodney et al., 2015; Rodney et al., 2018).
In the early 1997, Staples & Thatcher summarized 19 studies on the effect of fat inclusion into lactating dairy cow diets within the first 30 days postpartum. In over half of the studies supplemental fat resulted in dramatic improvements in the conception/pregnancy rates. One year later, Garg and Mehta (1998) found that bypass fat feeding reduced the average period for conception after calving (118 vs 92, days). Later, Naik et al. (2009) reported that bypass fat inclusion in crossbred cows diets reduced the required number of artificial inseminations per conception (1.4 vs 1.2).
Similar results, were reported in Angus and Hereford cows which consumed a supplement which contained 125 g of Ca-LCFA from palm oil (Espinoza et al., 1995), in Chinampas (Bos taurus) cows consuming Ca-LCFA from palm oil or beef tallow (Espinoza-Villavicencio et al., 2010); this is particularly important since cholesterol is the main precursor for progesterone synthesis in the corpus luteum as well as of other steroid hormones at the follicular level (Childs et al., 2008c).
Lucy et al. (1991, 1993), replaced corn with Ca-LCFA from palm oil in the ration of dairy cows at calving, and increased the number of medium size follicles (6-9 mm) and of follicles greater than 15 mm within 25 days postpartum. Furthermore, the diameter of the greatest follicle was superior in cows fed Ca-LCFA from palm oil.
Recently, Rodney et al. (2015, 2018) addressed the effect of dietary fat on fertility of dairy cattle. In 2015, explored the effects of including fats in the transition diet on the risk of pregnancy to service (proportion pregnant) and calving to pregnancy interval. Reproductive variables evaluated were risk of pregnancy (proportion pregnant), primarily to first service, and calving to pregnancy interval. Production variables examined were milk yield, milk composition, and body weight. These authors found that a 27% overall increase in pregnancy to service was observed. Moreover, a strong indication of a reduction in calving to pregnancy interval was also identified, which was consistent across studies, supporting a conclusion that, overall, the inclusion of fats does improve fertility.
The period of supplementation has influence of the effect. Thus, Tyagi et al. (2009) found that bypass fat supplementation during pre-partum period improved different parameters: calf weight (24.94 vs 27.95, kg), calving percent (88.88 vs 100); decreased the incidences of still birth (1 vs 0), premature birth (1 vs 0) and retention of foetal membranes (4 vs 1) in high yielding cross bred cows.
Nowadays, current dairy cows’ need for energy during transition. However, there are limitation factors that difficultate that cows take from diet all energy they need. As a consequence of the abovementioned physiological facts, cows enter Negative Energy Balance (NEB), which has tremendous effects on farms’ profitability, since it reduces milk production, increases the number of days open and thus compromises cows’ fertility.
Fats improved energy balance (von Soosten et al., 2012), then reducing the severity of NEB and its consequences and shortening the return to post-partum ovarian cycling. Also, the increase in progesterone secretion from improved energy balance improves fertility.
2.2. ROLE OF FATTY ACIDS
Recent understandings of the role of fats in metabolism open new opportunities for improving production, health, and reproduction in cattle (Herrera-Camacho et al., 2011; Rodney et al., 2015). Essential fatty acids, notably linoleic (omega-6) and linolenic (omega-3) acids have direct effects on physiological processes such as cellular membrane integrity, hormonal pathways, and immune function. Clearly, they are important to uterine health, and that is accompanied by earlier ovulations postpartum and more cycles during the voluntary waiting period. These events lead to improved fertility earlier in the postpartum interval, because they reduce services per conception and days open.
Growing evidence indicates that the design and delivery of supplemental fatty acids to the lower gut (primarily linoleic acid, EPA and DHA) may target reproductive tissues to improve reproductive function and fertility. Improvement in embryo survival may be associated with suppression of uterine prostaglandin secretion via linoleic acid or other longer chain unsaturated fatty acids. Although not discussed in this paper, changes in follicular dynamics can be affected by fat supplementation and may lead to a more fertile ovulation. This improvement may be due to alterations in metabolic hormones like IGF-I and growth hormone or hormonal clearance (Staples et al., 2015).
Increase linoleic acid may provide increase PGF2α and stimulate return to ovarian cycling and improve follicular recruitment. Fatty acids also allows modifying lipoprotein composition, which can increase progesterone secretion.
PUFAs supplied 21 days before parturition contribute to a faster recovery of the uterus and to improve cow fertility (Ambrose & Kastelic, 2003).
There is no abundant and precise information about daily requirement of essential fatty acids (18:2+18:3 and Omega-3) in ruminants. However, there is an important amount of scientific studies that are useful as they assess the effect of feed materials containing these fatty acids. For example, recommendation for linseed inclusion to diet (for improving reproduction performance or modifying milk FA) is up to 10% of DM (Petit et al., 2010). Again, the period of supplementation is important. Regarding omegas, Omega-6 sources are mainly recommended from parturition until 60 DIM, while Omega-3 are effective from first service.
Supplementation of Ca-LCFA in the diet has positive effect on reproductive performance of dairy cows (such as increased pregnancy rate and reduced open days; Sklan et al., 1991), which is further dependent up on the specific fatty acids profile of the Ca salt (Naik, 2013). The addition of LCFA to feed, in moderate quantities (2–3% dry matter, DM) during early postpartum of dairy cows, increases milk yield and improves cow reproduction, with a positive response on conception rate of up to 17% (Staples et al., 1998; Thatcher and Staples, 2000).
Feedstuffs stimulatory to reproduction included calcium soaps of long chain fatty acids (CaLCFA) (n = 6), fish meal (n = 4), and tallow (n = 1). Besides improved conception rate, one large study (n = 443 from five herds in Wisconsin) reported other positive benefits (Scott et al., 1995). A greater proportion of cows fed CaLCFA showed stronger signs of estrus (71.4 vs. 65.6% exhibited standing heat), had cycling ovaries (75.4 vs. 69.5% as determined by rectal palpation done every 2 to 4 weeks), and required less exogenous PGF2α to induce estrus (43.7 vs. 55.7%). McNamara et al. (2003) observed that supplementing cows with 0.35–0.5 kg Ca LCFA per cow per day improved fertility at first insemination of lactating cows.
3. CONCLUSIONS AND STEPS FURTHER AT FARM LEVEL
Supplementation of bypass and inert fats give additional benefits to those coming from “fats” as such, due to their effects on different aspects, such as cows fertility. Nutritional fats management must go beyond the concept of NEB so that nutritionists take into consideration fats benefitial effects on cows’ fertility. In this sense, different amounts and ratio of fatty acids must be formulated in dairy cattle rations.
In our previous article titled "Past, present and future of the feed industry- 2" information is given about "Past ve present and future of the feed industry".