Effect of levels of starch, fiber, and lactose on digestion and growth performance of early-weaned rabbits

Abstract

The effect of source of carbohydrate on gut histology, digestion efficiency, and growth performance in early-weaned (25 d) rabbits at the starter period (25 to 39 d) was investigated. Six diets were factorially arranged to study the effect of partial substitution of starch (0, 25, or 50%) by lactose at two levels of fiber (30 or 36% NDF). Diets were formulated to meet or exceed essential nutrient requirements of growing rabbits. A feeding trial was conducted to measure the effect of treatments on growth performance in 252 rabbits that were fed the experimental diets in the starter period and thereafter received a common feed until 60 d of age. Fecal apparent digestibility was determined at 35 d of age in nine animals per diet. The four diets with extreme lactose content were used to determine ileal apparent digestibility of starch and lactose (nine replicates per diet), weights of stomach and cecum, stomach pH, cecal fermentation traits, amylase and disaccharidase activities (10 animals per diet), and jejunal morphology (six animals per diet). Weaning increased (P < 0.001) amylase activity by 59% but decreased (P < 0.001) maltase, sucrase, and lactase activities by 30, 48, and 72%, in parallel with a reduction of villus height by 19%. Dietary NDF level did not affect either jejunal morphology or sucrase and lactase activities but increased amylase (P = 0.05) and maltase (P < 0.001) activities by 22 and 92%, respectively. Substitution of starch by lactose had no effect on jejunal morphology or enzymatic activity. Ileal lactose and starch digestibility were not affected by dietary NDF or lactose level and averaged 73.8 and 90.8%, respectively. Substitution of starch by fiber and lactose affected ileal flux of starch plus lactose (by -0.5 and +1.7 g/d) and cecal pH (by +2.1 and -2.8%, respectively). Fecal NDF digestibility was relatively low (23.1% on average) and was not affected by treatments, whereas that of lactose and starch was almost complete. An increase of dietary NDF level led to an impairment of ADG and feed efficiency in the starter (P < 0.002) and in the overall (P < 0.03) fattening period. Substitution of starch by lactose linearly decreased (P < 0.001) feed efficiency in the starter period and linearly increased (P < 0.001) diarrhea incidence in the fattening period. The results indicate that digestive capability of early-weaned rabbits is limited and should be taken into account to establish optimal levels and sources of carbohydrates in the starter diet.

An early stimulation of solid feed intake slightly influences the morphological gut maturation in the rabbit

“…On the contrary to the present results, Guttierez et al [9] observed shorter jejunal villi and deeper crypts on day 35 in rabbits weaned at 25 days compared with suckling rabbits. In other animal species, weaning seems more stressful for the small intestinal mucosa as compared to rabbits.…”

“…Some studies report an increased villous length and width with age [6,7] and a change in shape: from finger-like, villi become tongue and leaf-shaped [8]. But, to our knowledge, the potential influence of dietary factors on the development of the digestive mucosa has only been partially investigated [9].…”

Adaptability of the digestive function according to age at weaning in the rabbit: I. Effect on feed intake and digestive functionality

“…For instance, low levels of amylase activity in the young rabbit would be responsible for its low ability to digest starch. However, it has been shown that 35-day-old rabbits weaned for 10 days presented a higher amylolytic activity than still-suckling rabbits of the same age (Gutié rrez et al, 2002), which would mean a certain capability to adapt to nutritional changes. But this adaptative response was associated with a decrease in mucosal maltase activity, an enzyme also implicated in the digestion of starch.…”

Effect of different weaning ages (21, 28 or 35 days) on production, growth and certain parameters of the digestive tract in rabbits

“…The effects of different diets at early weaning (at ,26 days of age) have been studied by many authors. For instance, Gutierrez et al (2002) showed the effect of starch, fibre and lactose levels on digestion and growth, whereas Cesari et al (2007) studied the relationship between nutritive value of the diet and weaning age. The data of Feugier et al (2006), who investigated the fibre and protein requirement of early weaned rabbits, suggested that the detrimental effect of early weaning was not compensated for by a diet better meeting the young rabbits' nutrient requirements.…”