Utilization of cactus cladodes as a replacement for berseem clover: Effect on nutrient intake, rumen fermentation, blood metabolites, and milk yield, composition and fatty acid profile in the diets of dairy goats

The inclusion of alternative fodder in livestock diets can improve the production and quality of products, particularly milk. This experiment aimed to investigate the effect of replacing berseem clover (BC) (Trifolium alexandrinum L.) with cactus cladodes (CC) (Opuntia ficus-indica) at inclusion levels of 0, 150, and 300 g/ kg on a dry matter (DM) basis in the diets of dairy goats on nutrient intake, rumen fermentation, blood metabolites, and milk yield, composition, and fatty acid profile. Twenty-one pregnant Damascus goats (56.6 ± 0.55 kg of body weight (BW)), were randomly allocated into three experimental groups 30 days before their expected kidding date and continued for 90 days after parturition during the lactation period. Results indicated that as the proportion of CC in the diet increased, there was a linear increase (P < 0.01) in non-fiber carbohydrates intake, whereas the intakes of neutral detergent fiber and acid detergent fiber decreased linearly (P < 0.05). Ruminal levels of total volatile fatty acids increased linearly (P = 0.004), along with acetate (P = 0.022) and butyrate (P = 0.002), whereas ruminal pH (P = 0.048) and ammonia-N concentration (P = 0.001) decreased linearly with a higher proportion of CC. Additionally, there was a linear increase in triglyceride (P = 0.050) and cholesterol (P = 0.025), while blood urea levels decreased linearly (P < 0.01) and quadratically (P = 0.015) with a higher proportion of CC. The yields of milk (P = 0.016), fat-corrected milk (P = 0.005), fat (P = 0.012), protein (P = 0.030), lactose (P = 0.011), total solids (P = 0.042), and milk fat concentration (P = 0.014) all increased linearly with higher proportions of CC. Furthermore, final BW (P = 0.026) and average daily gain (P = 0.037) of kids increased linearly with a higher proportion of CC. The concentrations of fatty acids in milk, including C6:0 (P = 0.037), C14:0 (P = 0.003), C14:1n-5 (P = 0.001), C16:1n-7 (P = 0.010), C18:1n-9c (P = 0.046), C18:3n-3 (P = 0.001), and C20:5n-3 (P = 0.013), increased linearly with higher CC levels. In contrast, concentration of C18:0 (P = 0.010), C20:4n-6 (P = 0.044), total content of saturated fatty acids (SFA) (P = 0.012), SFA/MUFA ratio (P = 0.021), and n-6/n-3 ratio (P = 0.009) decreased linearly, while the total content of monounsaturated fatty acids (MUFA) (P = 0.038), polyunsaturated fatty acids (PUFA) (P = 0.013), and n-3 (P = 0.001) increased linearly in milk as the levels of CC increased. It can be concluded that the use of CC forage as an alternative to BC forage, enhanced rumen fermentation, and improved the productive performance of lactating dairy goats. Moreover, it enhanced the quality of the milk produced, especially its content of PUFAs and omega-3 fatty acids.