Abstract
Simple SummaryYoung ruminants possess an undeveloped rumen when first born. Encouraging good rumen development in early life is vital for young ruminants as they transition to a solid feed diet, to ensure optimum growth post-weaning. This study aimed to investigate the effect of three different rearing regimens on rumen development in lambs reared artificially. Weaning of lambs at 42 d of age improved rumen fluid n-butyric content and also resulted in a thicker rumen dorsal wall. Feeding lambs pellets with low fibre and weaning them early increased rumen fluid n-valeric content. Papillae width, density, and rumen wall muscle thickness were affected by rearing treatment. Empty rumen weight, rumen volume, papillae development, and rumen fluid iso-butyric and iso-valeric content had positive associations with dry matter intake and nutrient intakes from solid feed. The majority of volatile fatty acids in the rumen fluid had a positive association with papillae height on the rumen dorsal wall. These results suggest that lamb diet and age at weaning influenced rumen function and physical development. Further studies examining how rumen microbial composition and rumen gene expression are influenced by rearing regimens are required.The objective of this study was to examine the effect of three different rearing regimens on rumen development in lambs reared artificially. Romney ram lambs were randomly allocated to one of three treatments: commercial milk replacer fed to 57 d of age and high fibre concentrate pellets (HFP57); commercial milk replacer, high fibre concentrate pellets, and early weaning from milk replacer at 42 d of age (HFP42); high protein milk replacer from 2–16 d of age followed by commercial milk replacer, low fibre concentrate pellets, and early weaning from milk replacer at 42 d of age (LFP42). Lambs were slaughtered at 57 d of age. Volatile fatty acid content in rumen fluid at slaughter was analysed and rumen tissue samples were collected for histological examination. The rumen n-butyric content was greater (p < 0.05) in both LFP42 and HFP42 treatment lambs compared to HFP57 lambs. The n-valeric content was greater (p < 0.05) in LFP42 lambs compared to both HFP57 and HFP42 treatment lambs. Thickness of the rumen dorsal wall determined by ultrasound scanning at 49 d was greater (p < 0.05) in both HFP42 and LFP42 lambs compared to HFP57 lambs. There was an interaction (p < 0.05) between treatment and site of rumen tissue sampling on papillae width, density, and rumen muscular layer thickness. Collectively, early weaning and the provision of a low fibre pellet leads to improved rumen function and physical development.
Highlights
At birth, the rumen is anatomically and physiologically underdeveloped in lambs [1].The development of the pre-stomach in a young ruminant undergoes three phases: the nonruminant phase, the transition phase, and the ruminant phase [2]
The three rearing treatments were (i) commercial milk replacer fed to 57 d of age plus high fibre concentrate pellets (HFP57, n = 9); (ii): commercial milk replacer, high fibre concentrate pellets, and weaning from milk replacer at 42 d of age (HFP42, n = 9); (iii) high protein milk replacer from 2–16 d of age, followed by commercial milk replacer, low fibre concentrate pellets, and weaning from milk replacer at 42 d of age (LFP42, n = 9)
The n-butyric content of rumen fluid at slaughter was greater (p < 0.05) in both LFP42 and HFP42 treatment lambs compared to HFP57 lambs, which did not differ (p > 0.05, Table 3)
Summary
The rumen is anatomically and physiologically underdeveloped in lambs [1].The development of the pre-stomach in a young ruminant undergoes three phases: the nonruminant phase (birth to 3 weeks), the transition phase (from non-ruminant to ruminant stage), and the ruminant phase [2]. Unrestricted feeding, or a higher quantity of milk replacer feeding, reduces starter solid feed intake of calves [5,6] This can delay rumen development and reduce performance during the transition period to a pasture-based diet. Solid feed intake results in earlier establishment of rumen fermentation capacity [8] and greater utilisation of nutrients from solid feed [6]. This helps facilitate a smoother transition from the non-ruminant to ruminant stage, with less impact on post-weaning growth in young ruminants [9]
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