Both pregnancy and lactation are unique situations which place huge demands on the bitch’s
body and therefore a good quality, complete and balanced, highly digestible diet must be fed to best meet these needs.
During the first half of pregnancy, there is not a big increase in foetal growth and the bitch therefore only requires a slightly higher energy intake during this time. After this however, the energy required will increase dramatically and a pregnant bitch will require 40-60 % more energy by the time she is whelping than before pregnancy (Ackerman 1999; Agar 2001; Wortinger 2007). One problem often seen with this large increase in energy requirements is that because the pups are taking up more and more space in utero, it is difficult for the bitch to consume sufficient food, highlighting the importance of a high quality, palatable, energy dense diet. Therefore, feeding diets containing significant amounts of carbohydrate during late pregnancy and lactation should definitely be avoided, due to the resulting decrease in energy density. Another strategy during this time is to feed the bitch frequent small meals, so that she can still meet her own, and the foetus’ requirements.
Lactation places even greater demands on the bitch’s body than pregnancy, since she has to satisfy her own maintenance needs and be able to make enough good quality milk for her growing puppies (Ackerman 1999; Buffington et al. 2004; Wortinger 2007). The bitch’s peak
energy requirement occurs when the pups are three to four weeks old, during which time she will require two to four times the calories needed when she was pregnant (or three to four times her own maintenance requirements) (Ackerman 1999; Agar 2001). Because of these enormous demands, ad libitum feeding is the preferred method of feeding during this time.
Once the pups are introduced to solid food, their demand for the bitch’s milk begins to
decrease, and once the pups are fully weaned at approximately six weeks of age, the bitch’s
energy requirements are reduced to approximately 50 % above maintenance requirements. By the time the pups are approximately eight weeks of age the energy requirement of the bitch has returned to pre-pregnancy (maintenance) levels (Ackerman 1999).
It has been reported that the only obligate requirement for carbohydrate in dogs is during pregnancy and lactation (Guilford 1993), however this is an area of debate in the literature. All animals have a metabolic requirement for glucose but this can be supplied through endogenous synthesis during growth and maintenance, provided there is sufficient fat and protein in the diet to provide the necessary precursors, or directly from dietary carbohydrate sources (Greco 2008). Therefore, if there is enough protein and fat in the diet there may not be a need for carbohydrate in the diet during pregnancy and lactation either.
During gestation, the bitch’s need for glucose increases because glucose is the major energy source for fetal development, and similarly during lactation extra glucose is required for the synthesis of lactose in the milk. One early study in dogs showed that bitches fed a carbohydrate free diet throughout gestation became hypoglycaemic, hypoalanemic and ketotic toward the end of pregnancy, with only 63 % of pups born alive and the mortality of these
pups shortly after birth was high (Romsos et al. 1981). However, a subsequent experiment
found a carbohydrate free diet did not affect the duration of gestation, litter size or pup weight or mortality (Blaza and Burger 1989). The different outcomes of these two studies were believed to relate to the higher protein levels of the diets fed in the second trial. The higher protein levels were thought to have given the bitches enough gluconeogenic amino acids to maintain plasma glucose levels and maintain pup viability. Based on these studies, it appears
even during pregnancy and lactation, provided there is sufficient protein in the diet (NRC 2006).
Along with the increased requirements for energy during pregnancy and lactation the requirements for other nutrients is similarly high (Agar 2001). Of most importance is water, which must be available at all times. Dietary fat requirements are thought to be greater than that for maintenance, however as previously mentioned in section 1.5.2 studies that precisely establish the requirement for total fat have not been carried out (NRC 2006). For this reason the NRC (2006) has set the recommended allowance for dietary fat for pregnancy and lactation as 8.5 % on a DM basis or 18 % on a ME basis.
Protein and amino acid requirements for this particular life stage have also not been well defined for dogs, but generally it is assumed that the crude protein requirement for growth would be sufficient to meet the needs of pregnant and lactating dogs (NRC 2006). The
recommended allowance for growth set by the NRC (2006) is 200 g kg-1 of a diet containing
4.0 kcal ME g-1.
In terms of micronutrient requirements, the NRC (2006) has also recommended various levels for pregnant and lactating bitches. Two of the most important of these are calcium and phosphorous. The recommended allowances for calcium during the last three weeks of pregnancy and for a 22 kg lactating bitch with eight puppies (assuming a bioavailability of 40 %) are 160 mg kg BW-1 d-1 and 360 mg kg BW-1 d-1, respectively (NRC, 2006). However, to ensure adequate calcium intake for lactating bitches of all breeds, the recommended allowance is 380 mg kg BW-1 d-1 (NRC 2006). Phosphorous allowances during the last five weeks of pregnancy also for a 22 kg lactating bitch with eight puppies are 133 mg kg BW-1 d-1 and 145 to 290 mg kg BW-1 d-1 (NRC 2006).