Juan Edrei Sánchez-Torres

Heat stress represents a major challenge in rabbit production in tropical regions, where high temperature–humidity index (THI) values compromise thermal homeostasis and animal welfare. This study evaluated the effect of providing cool drinking water as a heat stress mitigation strategy on growth performance, carcass traits, water intake, and physiological responses in growing New Zealand White rabbits. Sixteen male rabbits were assigned to receive either drinking water at ambient temperature (33.9 ± 1.5 °C) or cooled water (16.7 ± 1.8 °C) supplied during periods of highest thermal load (10:00–17:00 h) over a four-week experimental period. Ambient temperature and relative humidity were monitored to calculate THI, and body temperatures were recorded during morning and afternoon periods. Average daily gain, carcass traits, and water intake were not affected by drinking water temperature (p > 0.05). However, the feed-to-gain ratio over the overall experimental period was higher in rabbits receiving cooled water (p = 0.03). In contrast, rectal temperature during the afternoon was significantly reduced in rabbits receiving cooled water, as reflected by a significant water × period interaction (p = 0.03), representing a 0.62% reduction compared with rabbits receiving normal drinking water, particularly during periods of greater thermal challenge, whereas ear and body surface temperatures were mainly influenced by the experimental period (p < 0.01). These results indicate that moderate cooling of drinking water elicits measurable physiological responses associated with short-term thermoregulatory adjustment, without improving growth performance. Providing cool drinking water represents a practical strategy to support thermoregulation under heat stress conditions in rabbit production systems in tropical climates.

The objective was to evaluate the effect of the inclusion of avocado waste (AW) in the diet of rabbits on lipid composition, color, and lipid and protein oxidative stability in the meat of growing rabbits. For this purpose, 80 male rabbits (New Zealand × California) with an average initial weight of 945 ± 47 g were fed for 28 days, being randomly distributed to one of the four experimental treatments (T) (T1: 0%, T2: 4.32%, T3: 8.39%, and T4: 12.25% of waste avocado inclusion, respectively). A decrease (p < 0.05) in the amount of saturated fatty acids was observed in the meat of rabbits fed 8.39% and 12.25% AW, a lower (p < 0.05) concentration of malondialdehyde (mg MDA/kg) in the meat of rabbits fed the AW, and a lower (p < 0.05) concentration of dinitrophenylhydrazine (DNPH) in the treatments with 4.32 and 8.39% AW. The results suggest that the addition of AW in rabbit diets increases the content of n-3 polyunsaturated fatty acids and protects the meat from the products of lipid and protein oxidation, decreasing discoloration and delaying oxidation, generating a final product with a longer shelf life.

Background: The consumption per capita of rabbit meat in Mexico is limited (120g) due to the lack of information among consumers about the nutritional quality of rabbit meat, and at the same time, to the appearance of color, since they prefer a redder meat with more intramuscular fat. Objective: To evaluate the effect of the addition of Zinc-Methionine (Zn-Met), marigold flower pigment (FC) and two slaughter ages (MS) on carcass characteristics and meat quality in rabbits. Methodology: A total of two hundred 40-day-old rabbits (New Zealand X California, 1124±48 g initial live weight) were randomly assigned to one of 4 experimental diets and two fattening periods (68 and 82 days of age), using a completely randomized experimental design with a 2 x 2 x 2 factorial design. The control diet contained no additives, the second diet contained 200mg/kg-1 Zinc Methionine (Zn-Met), the third diet contained 80 mg/kg-1 marigold flower pigment (FC) and the fourth diet (Zn-Met*FC) contained both additives (200mg/kg-1 Zn-Met and 80 mg/kg-1 FC). The color, pH, meat-bone-to-dissectible fat ratio, water loss by cooking, shear strength and nutritional quality of rabbit meat were measured in the Longissimus thoracis et lumborum (LTL) muscle. Results: In meat color, L* values showed interactions (P < 0.05) between Zn-Met*EM and FC*EM; interaction was observed for carcass bone weight (g) (P < 0.05) between Zn-Met*FC, finding higher values (P < 0.05) in rabbits slaughtered at 82 d of age (g and %). With respect to the amount of dissectible adipose content of the carcass (g and %), there was interaction between Zn-Met*EM (P<0.05), with the highest values found in rabbits killed at 82 d (P<0.05). On the other hand, there was interaction in crude protein content (g/100g-1) (P<0.05) between Zn-Met,*FC*EM; while in moisture content and ethereal extract (g/100g-1) there was a difference (P<0.05) between animals slaughtered at different ages. MS increased the saturated fatty acid (SFA) content, while in the monounsaturated fatty acid (MUFA) content there was an interaction between Zn-Met*MS (P<0.05), with rabbits killed at 82 d of age presenting the highest values (P<0.05). Implications: The addition of Zn-Met modifies the fatty acid profile of meat in cattle and sheep, while the FC pigment modifies the color of poultry meat; however, the addition of these additives has not been studied in rabbits. Conclusion: The inclusion of Zn-Met, FC at two ages at slaughter modifies meat color and nutritional composition of rabbit meat.

The inclusion of triticale in rabbit diets can negatively affect production parameters due to the presence of arabinoxylans that increase the viscosity of intestinal contents, making digestion and absorption of nutrients difficult. Therefore, the addition of the enzyme xylanase can improve intestinal morphology and the digestive process. This study aimed to conduct histological and histochemical evaluations of the small intestine and caecal appendix in growing-finishing rabbits fed diets containing 14% triticale supplemented with varying levels of xylanase. The rabbits had an initial average live weight of 822 g and reached a final weight of 2097 g. For this purpose, forty 35-d-old male rabbits crossbred New Zealand × California were used. Rabbits were housed in individual cages and randomly divided into four experimental treatments (xylanase at doses of 0, 4000, 8000 and 12 000 xylanase units (XU)/kg of dry matter). At the end of the experimental period, rabbits were slaughtered at seventy days of age and samples were taken from the duodenum, jejunum, ileum and caecal appendix. Samples were stained using the standard Haematoxylin-Eosin (HE) technique for the histological evaluation and Alcian Blue (PAS) for the histochemical evaluation. The addition of xylanase linearly increased the height of villi in the duodenum, jejunum and ileum, while villi width was linearly reduced in jejunum and increased in ileum. Crypt depth was linearly reduced by xylanase dose in duodenum, while the response was linear and quadratic in jejunum and ileum. The villi height to crypt depth ratio was linearly increased by the xylanase dose in the duodenum and jejunum, although the effect was quadratic in the ileum. The dome height of the caecal appendix increased linearly with the addition of xylanase. Epithelial mucus count was linearly reduced by xylanase dose in the base of the duodenum, jejunum and caecal appendix, although this linear reduction was only observed in the villi of the jejunum and in the caecal appendix. In conclusion, the addition of xylanase positively affected the histological and histochemical characteristics of the small intestine and caecal appendix, so its use could improve digestive and productive performance in rabbits.

Cereals such as triticale may contain high levels of xylans and arabinoxylans, limiting its use in diets since they act as anti-nutritional factors. The objective was to evaluate the effects of the enzyme xylanase included in triticale-based diets on productive performance, digestibility, carcass traits and meat quality in growing-finishing rabbits. Eighty rabbits (New Zealand X California breed), 35 days old, with an average initial live weight of 821 ± 26 g, were used. Twenty animals for treatment were used in each one of the fourth experimental treatments: 0, 4000, 8000 and 12,000 XU/kg of xylanase inclusion (XilaBlend 6X). The rabbits were fed ad libitum and fecal excretion was collected on days 7, 14, 21, 28 and 35 of the experimental period. At the end of the experimental period, the rabbits were slaughtered and carcass characteristics and meat quality were measured. A higher (P < 0.05) live weight was observed in rabbits fed diets with the addition of xylanase enzyme on days 4 and 7 of the experimental period. On the other hand, in the average total tract digestibility of organic matter, no significant difference was observed, similar to what occurred in the carcass traits and nutritional quality of the meat. The inclusion of 8000 XU/kg of xylanase enzyme provided the best values of apparent digestibility of total tract protein and dry matter on the finished stage of rabbits.

Cereals such as triticale may contain high levels of xylans and arabinoxylans, limiting its use in diets since they act as anti-nutritional factors. The objective was to evaluate the effects of the enzyme xylanase included in triticale-based diets on productive performance, digestibility, carcass traits and meat quality in growing-finishing rabbits. Eighty rabbits (New Zealand X California breed), 35 days old, with an average initial live weight of 821 ± 26 g, were used. Twenty animals for treatment were used in each one of the fourth experimental treatments: 0, 4000, 8000 and 12000 XU/kg of xylanase inclusion (XilaBlend 6X). The rabbits were fed ad libitum and fecal excretion was collected on days 7, 14, 21, 28 and 35 of the experimental period. At the end of the experimental period, the rabbits were slaughtered and carcass characteristics and meat quality were measured. A higher (P < 0.05) live weight was observed in rabbits fed diets with the addition of xylanase enzyme on days 4 and 7 of the experimental period. On the other hand, in the average total tract digestibility of organic matter, no significant difference (P > 0.05) was observed, similar to what occurred in the carcass traits and nutritional quality of the meat (P > 0.05). The inclusion of 8000 XU/kg of xylanase enzyme provided the best values of apparent digestibility of total tract protein and dry matter on the finished stage of rabbits.

Zilpaterol hydrochloride (ZH) redistributes ingested energy and improves feed efficiency by increasing muscle mass and reducing fat in sheep and cattle carcasses in fattening; however, by increasing lipolysis and reducing intramuscular fat (IMF), it can affect meat quality in terms of the attributes of tenderness, juiciness, taste and color; in contrast, Zn methionine (ZM), due to its lipogenic effect, can improve meat marbling without affecting production efficiency. In the current study, 36 male Suffolk sheep were used (25 ± 0.58 kg live weight, LW) to evaluate the supply of ZH and ZM on growth, carcass traits, meat quality, fatty acid content and expression of genes which regulate the deposition of fatty acids (FA) in IMF. A completely randomized design was used, with factorial arrangement of 2 × 2 ZH (0 and 0.2 mg kg⁻¹ LW) and ZM (0 and 80 mg Zn kg⁻¹ dry matter, DM). The results showed that ZH increased (p < 0.05) carcass yield, compactness index and chop eye area and decreased greasing (p < 0.02). The content of ether extract in meat increased (p < 0.05) in sheep with ZM plus ZH, and in sheep with ZM (p < 0.01). ZH (p < 0.05) reduced (p < 0.02) the meat’s color index L*, a*, b*, C* and H*. The content in IMF of stearic (C18:0) and arachidic (C20:0) FA was reduced (p ≤ 0.05) by the effect of ZH, but the palmitoleic (C16:1), eicosatetraenoic (C20:4n6) and conjugated linoleic FA were increased (p ≤ 0.05) by the effect of ZH. ZM increased (p ≤ 0.05) palmitoleic (C16:1) and conjugated linoleic FA; the ZH interaction with ZM increased (p ≤ 0.05) linoleic (C18:2 c 9 c 12), linolenic (C18:3 c 9c12c15) and eicosatetraenoic (C20:4n6) FA. The ZH interaction with ZM influenced (p ≤ 0.05) the total saturated fatty acids (SFA), unsaturated fatty acids (UFA) and polyunsaturated fatty acids (PFA). ZH increased (p ≤ 0.05) the relative expression of mRNA from the enzymes lipoprotein lipase (LPL), hormone-sensitive lipase (HSL), glycerol -3-phosphate acyltransferase (GPAT1) and diglyceride acyltransferase (DGAT1). ZM increased (p ≤ 0.05) the relative expression of mRNA from the enzyme gene acetyl-CoA carboxylase (ACC) and HSL, monoglyceride lipase (MGL). The ZM interaction with ZH increased (p ≤ 0.05) the relative expression of mRNA genes of the enzymes HSL and ACC. It was concluded that ZH improved feed conversion (FC), increased yield and reduced fat in carcasses; ZM increased IMF in Longissimus dorsi. ZH and ZM influenced the FA composition, reduced the SFA and increased the UFA and PFA; both additives also influenced the relative mRNA expression of genes involved in fatty acid metabolism.

The objective of this paper was to evaluate the effect of four levels (0%, 4.32%, 8.39% or 12.25%) of avocado waste (AW) included in the diets on productive performance, carcass characteristics and meat nutritional quality of fattening rabbits. For that, one hundred and twenty male rabbits (New Zealand × California; 945 ± 47 g initial body weight) were fed over 28 days, randomly distributed to one of the four treatments (T) (T1 = 0, T2 = 4.32, T3 = 8.39 and T4 = 12.25% AW as fed). The chemical and fatty acids profiles were evaluated in the Longissimus thoracis et lumborum (LTL) muscle. The rabbits fed with 8.39% of AW reported the best productive parameters (p < 0.05), the greater (p < 0.05) dissectible adipose tissue and higher polyunsaturated fatty acids (PUFAs) n-3 content (p < 0.05) than control meat. It is concluded that the inclusion of AW in the growing–finishing rabbit’s diet can modify the nutritional quality of the meat, reducing the n-6/n-3 ratio and the thrombogenic index.

The objective was to evaluate the addition of xylanase on the productive performance and histological aspects of the small intestine and cecal appendix of rabbits fed diets containing triticale. 120 rabbits were randomly distributed to one of the four treatments differentiating them from the inclusion of xylanase (0, 4000, 8000 y 12000 XU/kg, respectively), the animals were weighed weekly and at the end of the experimental period, the rabbits were slaughtered taking samples of the duodenum, jejunum and cecal appendix to perform the technique of staining with Hematoxylin-Eosin (HE). An analysis of variance was performed using the GLM procedure of SAS (2002) and Tukey’s test. The addition of xylanase enzyme increased (pp<0.05) the areas of intestinal villi of the duodenum, jejunum and cecal appendix.

Meat is an excellent medium for bacterial growth due to its high water and nutrient content. The nitrogenous compounds (NC) are derived through decarboxylation of amino acids due to microbial enzymes. The objective of this study was to evaluate the concentration of 3 NC and the proliferation of some microorganisms in rabbit meat with three treatments (T) , classified by three types of packaging for 21 days (d) in rabbit meat stored cold. The meat samples were obtained of the Longissimus thoracis et lumborum muscle. Each sample was divided and two groups were formed. The first group was used to measure the physicochemical characteristics of the meat, and the second group was used to quantify NC and bacterial isolation. The pH in the meat decreased from 0 to 21 d in the three T. The brightness (L*) decreased (P<0.05), while the variables a* and b* increased (P0.05). Putrescine (PU) increased (P<0.05) from 7 to 21 d in the Control-Plastic (CP) and Semi-permeable plastic film (SP) groups vs. Vacuum packing (VP). The Enterobacteriaceae remained constant throughout the experimental period in the three T, compared to the aerobic mesophilic, which was higher (P<0.05) until 21 d of the evaluation in CP and SP. The type of packaging and cooling time influenced the concentration of NC. The VP had the lowest level of PU and mesophilic bacteria until 21 d of storage.