Effect of Essential Unsaturated Fatty Acids in Fish Oil on Litters and Composition of Milk of Rabbit Does

The aim of the study was to determine the degree to which a 3% fish oil supplementation in female rabbit diets affected the quantitative composition of fatty acids in milk, litter size, litter weight, and birth-to-weaning mortality of young rabbits in three successive litters. Twenty New Zealand White female rabbits of the foundation stock and all their offspring were investigated. Animals were assigned to two feeding groups: group I, fed a pelleted basal diet with standard components; group II, fed a pelleted diet with 3% fish oil. The fish oil was a byproduct of fish (herring, sprat, silver carp, mackerel, cod) meal production and contained 2.9% of C18:3n-3, 7.4% of C20:5n-3 (EPA), 12.6% of C22:6n-3 (DHA) and 0.8% of C22:5n-3 (DPA). Fat milk increased from 18.4 to 22.2% in female rabbits receiving 3% fish oil compared to the control group. In the milk fat of female rabbits, there were highly significant differences between the control and experimental groups in the level of polyunsaturated fatty acids of the n-3 series (n-3 PUFA) and saturated fatty acids (SFA). The fish oil supplementation reduced the level of short-chain fatty acids in milk (C8:0-C10) and increased the level of long-chain fatty acids (C16:1–C22:6). Milk was characterized by a higher concentration of EPA and DHA. Fat supplemented diets increased kit weight at birth, 21 days and 35 days of age (P<0.01) in the three reproductive cycles. In the experimental group, there was a higher percentage of reared rabbits in all the litters analysed. The high mortality of young rabbits among primiparous rabbits was due to relatively low milk production, which increased with parity. The bacteriological tests of the rabbits with diarrhoea symptoms showed that the main causes of mortality were the proliferation of conditionally pathogenic Escherichia coli, responsible for enteritis and the presence of Streptococci, which are relatively or conditionally pathogenic bacteria. There were no significant differences between the milk production of female rabbits from groups I and II, which shows that the fish oil supplementation had no effect on this parameter. Milk yield was significantly affected by litter size. For this reason, the lower mortality of young rabbits may result from the higher fat content of milk rather than from the higher milk yield.