The transition period is the most delicate in dairy goats management, but diagnostic aids are not available yet. At the date, precise and functional nutrition is the only effective strategy to optimally face peripartum and transition periods. An accurate analysis of the real needs is mandatory to reach the goal.
Nutritional needs of dairy goats mainly include energy and protein requirements: how can we develop an effective nutritional strategy?
The most recent indications about small ruminants’ nutritional needs are included in the NRC (2007). About goats, information is referred to the NRC of 1981 and some relevant papers published in early 2000. Anyway, the research on this topic is poor and there are many difficulties linked to the zootechnical management of this species:
- There is a large variability connected to biotype and genotype (there are a lot of autochthonous biotypes extremely different from each other). Even if some authors (Nashalai et al., 2004) state that there is little variation in animal needs, it is clear how huge biodiversity is in this species.
- Goats farming is still considered a niche reality. The consumption of goat milk and cheese, while increasing, still counts very small numbers.
- Management is extremely various: there are farms very similar to these for bovines, while others are extremely essential and located in marginal areas.
For these reasons, the evaluation of real animal needs includes variables hard to be determined but very important to be accurate (i.e., thermoregulation, movement in more or less steep pastures, high probability of multiple births). About the fetuses, it is possible to determine the right number, but the accuracy of the diagnosis is inversely proportional to the time of gestation and is not always possible to increase the number of examinations.
To apply nutritional requirements in practice, it is important to take into account that peripartum problems mainly derive from an energetic unbalance.
First of all: a goat is not a tenth of a cow, except for its body weight. Talking about nutritional needs, we must take into account the metabolic weight ((body weight)0,75). In this case, a goat of about 70 kg has a tenth of the body weight of a cow of 700 kg, but the metabolic weight is 0.18 (the cow is equal to 5.5 goats). About the energy need for maintenance, according to Salah et al. (2014), the ratio is 0.15 (the cow is equal to 6.6 goats, more or less). We can do this exercise even for the other needs, with similar results. Specifically, the higher number of variables (temperature, physical activity, etc), the more similar the cow/goat ratio. That means that a goat is not a small cow.
During peripartum, the energy requirement is composed of: metabolic energy (ME), the energy requirement for pregnancy (MEp), and energy for growth (MEg) (this last one is for nulliparous goats). While there are numbers of sources to refer to about ME (NRC, 2007; Nsahlai et al., 2004), MEp, MEg, and the energy for lactation are not easily determinable.
The MEp is calculated for the last 2 months of pregnancy (or the dry period). NRC (1981) suggests an increase of about 0.318 MJ for the metabolic weight during the last 2 months of pregnancy and an additional 20% in twin pregnancy. Sahlu et al. (2004) revised requirements taking into account fetal growth, the efficiency index related to the newborns’ weight, and twinning, starting from the 90th day of pregnancy and with 10-day intervals (Koong et al., 1975; NRC, 2001; ARC, 1980).
Lactation requirements are determined starting from the metabolic needs (MJ/kg of milk) corrected at 4% of fat, through a complex data elaboration in the bibliography (Nsahlai et al., 20004).
Just as an example, a goat during the last month of pregnancy with two kids (average weight 3.5 kg/kid) has the same energy requirements as a goat producing 2 liters of milk with 3.5% of fat, and the 75% as a goat with average milk production of 3 liters.
On these bases, the end of pregnancy is similar to lactation as energy requirements. However, there is an important aspect often forgotten: lactation starts at parturition, but galactogenesis begins earlier. Weight and volume of the udder increase starting from day 120 of pregnancy with the peak at lambing (Lerias et al., 2014). This growth and the galactogenesis take both nutrients and energy
It would be correct to consider that in the last weeks of gestation the MEp overlaps that for lactation. Dairy cows receive a customized precision feeding provided in the delivery room. A similar feeding in goats, due to the seasonal fertility, can satisfy only a little part of the group and it is necessary to optimize the whole production process to avoid that the feed formulation is not just a purely theoretical exercise.
The last point to be considered is the dry matter intake (DMI), which is extremely important in goats’ peripartum. The fairest calculation is that of the minimum DMI related to the energy concentration of the feed (not just the absolute DMI related to the animal physiological status). DMI is inversely proportional to the energy concentration of the feed. Luo et al. (2004) developed models to determine the DMI starting from a huge database in literature. Sahlu et al. (2004) indicated DM requirements in relation to the energy concentration of 4 diets. The intake of a low energy diet (7 MJ/kg) is 60-70% higher than the one of a highly energetic one (13 MJ/kg). This is an important difference between goats and cow nutrition. Dairy cow feed has more or less always the same energy concentration, while it is different for dairy goats, depending on the quality of the ingredients. During the last 3 weeks of pregnancy, this aspect is extremely important: lipomobilization is inversely proportional to DMI. The intake is even lower in the case of twin pregnancies, due to the reduced abdominal capacity.
During this period it is important to maximize the intake but also to formulate diets with high energy. The second and third crops are the best forage sources. As a source of concentrates, a mix of different cereals allows the splitting of rumen fermentability. It can be useful also the addition of a moderate amount of fractionated hydrogenated fats and the use of simple carbohydrates and molecules with 3 carbon ions (i.e. propylene glycol). The use of feed additives such as vitamins and essential amino acids with lipotrophic activity can be useful during this phase, with very active lipid metabolism.
In conclusion, the peripartum is an extremely critical period for dairy goats. Precise and functional nutrition is not always appliable. Balanced diets are not enough, it is important to take into account nutrients and real animal needs. The goat is a very delicate animal, but exceptionally versatile, so much so that it can even eliminate the need to kid every year through the application of the zootechnical practice of extended lactation. At a time when animal welfare is imperative, implementing extended lactation goes precisely in this direction, as well as producing undisputed economic benefits for the company that deserves specific further study.For more information: marketing@vetagro.comOriginal article here.More info about goats here (Italian)