Fontes alternativas de alimentos para vacas em lactação

Abstract

In order to evaluate alternative feeds for the production of milk in the semiarid region, considering the lack of work and the opportunity to use the sugarcane bagasse as exclusive bulk for lactating cows and the replacement of sugar cane by cactus cladodes (orelha de elefante mexicana), it was aimed at first evaluated the sugarcane bagasse as roughage for lactating dairy cows under intake, digestibility, ingestive behavior, milk yield, milk composition and microbial protein synthesis. Ten girolando cows at ±25.6 kg of body weight and at 30.7 days in milk were distributed into two contemporaneous 5x5 Latin square. Five experimental periods of 21 days were adopted (14 first day of diets adaptations and the last 7 days for data and samples collections). Experimental diets consisted of four different levels of sugarcane bagasse (45, 50, 55 and 60%) and one control diet commonly adopted in the region, based on spineless cactus (25% sugarcane bagasse), formulated to meet 12 kg/d milk yield.The dry matter (DM), organic matter (OM), and total digestible nutrients intakes and DM and OM digestibilities observed for 45% and 50% bagasse inclusion were similar to control diet, while that 55% and 60% bagasse inclusion were lower. Cows fed control diet, and bagasse diets of 45%, and 50% levels had the nutritional requirements attended, that guaranteed 12 kg/d of milk yield. The crude protein intake and digestibility of cows fed 45%, 50%, and 55% of bagasse inclusion were similar to control diet. The neutral detergent fiber (NDF) intake and digestibility differ for all bagasse diets related to control diet, while the non-fiber carbohydrates intake and digestibility for cows fed 45% of bagasse were similar for control diet. The intakes and digestibilities of nutrients decreased linearly in function of bagasse inclusion; NDF and indigestible NDF intakes did not vary. The ruminating time, feeding and rumination efficiency, microbial protein synthesis and milk yield decreased linearly with sugarcane bagasse inclusion. Sugarcane bagasse decreases milk production; however, its inclusion level in between 45% to 50% associated to concentrate could replace diets based on spineless cactus for crossbred dairy cow's producing 12 kg/d of milk. At the second moment, At the second moment, it was aimed to evaluated the intake of nutrients and total digestible nutrients (TDN), milk yield (MY), milk yield corrected to 3.5% of fat (MYFC), fatty acids (FA) profile and milk fat nutrition quality indexes of Holstein cows fed cactus [Opuntia Stricta (Haw.) Haw] cladodes replacing sugarcane. Ten multiparous Girolando cows with milk yield of 20.93± 3.10 kg/day were allocated in a 5x5 Latin square design. It was adopted five 21 days experimental periods. The experimental diets tested were, a control diet based on sorghum-IPA-SF15 silage and four different replacement levels of sugarcane for cactus cladodes (0, 17.2; 34.4 e 51.6%). The intakes of dry matter (DM), neutral detergent fiber (NDF) and TDN, and MYFC were higher with replacement in relation to control diet. The replacement levels promoted a quadratic response for intakes of DM and TDN, MY and MYFC. The saturated FA of short and medium chain was higher for replacement than control diet. The lauric (C12: 0), myristic (C14: 0) and palmitic (C16:0) acids were higher in diets with sugarcane and cactus cladodes. The sum of conjugated linoleic acids (CLA) was higher with the control diet. According to the cactus inclusion there was a linear reduction in CLA levels. The control diet provided lower atherogenicity (AI) and thrombogenicity (TI) indexes and a lower ratio between ω6-ω3 and hypo: hypercholesterolemic (h/H). The AI increased linearly according to cactus increased and while the h/H ratio decreased. Diets containing sugar cane and forage palm elephant ear favor the consumption of DM and nutrients and, consequently, higher milk production. Sorghum silage provides better nutritional quality of cow's milk fat, presenting them as a characteristic to be beneficial to human health and meeting consumer market demand trend. The partial replacement of sugar cane by cactus cladodes provides a lower nutritional value milk fat quality.