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Twenty Pelibuey 3-4 month old and 23.7±3.3 kg body weight male lambs were used in a randomised design to study the effects of daily oral administration of Salix babylonica (SB) extract on dry matter (DM), water intake, average daily gain (ADG), and feed efficiency for 72 days. Animals were divided into four groups fed the same total mixed ration with different doses of SB: 0 (Control), 20 (SB20), 40 (SB40) and 60 (SB60) mL/lamb/d. In vitro gas production (GP) of the same diet fed to lambs as a substrate was measured with different doses of SB (0, 0.3, 0.7, 1.0 mL/g DM). Daily administration of SB to lambs had no effects (P=0.05) on growth performance and DMI (linear effect, P=0.2805; quadratic effect, P=0.3747). Both low and moderate doses of SB (SB40>SB20) tended to increase (linear effect, P=0.4010; quadratic effect, P=0.9166) ADG. The asymptotic GP quadratically increased (P<0.001) with decreased GP rate and with increasing SB extract doses. In vitro GP increased (P<0.05) with advancing of incubation time in all SB doses. During the first 24 h of incubation, 0.3 mL SB/g DM had the highest GP, whereas 1.0 mL SB/g DM quadratically increased (P<0.001) GP. The low dose of SB extract increased ME (linear effect, P=0.024) and short chain fatty acids (SCFA) (linear effect, P=0.023). However, the highest dose quadratically decreased (P=0.02) DM degradability. In conclusion, administration of SB extract at 40 mL/lamb/d tended to increase DM intake, improve daily weight gain in growing lambs with increasing asymptotic in vitro ruminal GP and SB dose.

The objective of this study was to evaluate sexual behaviour and semen quality of St. Croix ram lambs bred in a semi-desert region. In Experiment 1, 24 yearling rams were assigned to two groups: T1 with 12 males confined for 11 months; T2 with 12 males confined individually for the same period of time. In Experiment 2, 20 four-month-old ram lambs were assigned to two groups of 10 animals each. In each experiment, sexual behaviour and semen quality were evaluated every 2 weeks over 11 months. In Experiment 1, rams that were individually confined showed better sexual activity than lambs confined together (P<0.05), whereas in Experiment 2 ram lambs confined individually only showed shorter time to first mount with ejaculation (P<0.05). In experiment 1, sperm with better progressive motility (P<0.05) was recorded per yearling ram confined individually (63.4±0.2%) in comparison with rams confined together (51.60.1%). In Experiment 2, ram lambs confined together showed better semen quality (P < 0.05). In both trials, an effect of the season was observed on both sexual behaviour and semen quality (P<0.05). In conclusion, this study of St. Croix males showed different sexual behaviours according to age and type of enclosure.

Agrosilvopastoral systems that integrate crops, pastures, trees and shrubs are seen as a way forward to meet future needs for food, feed, fuel, and other products, as well as for providing environmental and social benefits. Cattle production systems in the tropical and subtropical areas of Mexico have a dual-purpose (milk and beef) objective in agrosilvopastoral systems that need to improve the production of goods, as well as non-productive outputs like environmental services, enhancing their sustainability. The aim of this study was to characterise the socioeconomic, and productive characteristics of dual purpose farms based on agrosilvopastoral systems (ASPS), in a subtropical region in the southern highlands of central Mexico, to contribute in the understanding of how these ASPS operate and their differences. Forty-seven farmers answered a semi-structured questionnaire to identify aspects of farm management, structure, and land use; as well as technical and economic aspects. Information was analysed using factorial analysis of principal components, in order to reduce information, and subsequently cluster analysis that included nine variables resulting into four groups of farms differentiated by structure, size, management and productive orientation. Productive orientation of the farms was from the activity from which farms obtained most of their incomes. The four groups were beef production oriented (BPO) 46.81%, milk production oriented (MPO) 23.40%, pure breed weaned calves (PBWC) 17.02%, and traditional dual-purpose (TDP) 12.77%. Characterization of agrosilvopastoral farms identified main differences and characteristics, as well as the presence and use of trees and shrubs by farmers and cattle.

The objective of this study was to determine the effect of the weaning method on lamb stress, body weight, sexual behavior, and semen quality of Saint Croix male lambs. The present study was carried out during the late spring and summer of 2018 in the northeast of Mexico. Sixty male lambs born as twins or triplets (3.2 ± 0.6 kg birth weight) and weaned at 60 d of age (19.21 ± 1.8 kg weaning weight) were divided into two weaning methods: complete separation from the dams (CS; the lambs were moved to a pen that was at 500 m of distance from the dams) and separation with contact from the dams (SCD); the lambs were physically separated by a steel mesh that prevented the lambs from having the possibility of sucking milk from their mothers, but they maintained permanent visual and auditory contact. Cortisol levels were determined 3 d before and 7 d after weaning. Lambs were evaluated as 3-month-old lambs for sexual behavior and semen quality for 9 weeks. The effects of the weaning method (M), week (W), and the interaction M × W were significant on body weight and cortisol levels (P<0.001). The SCD lambs had higher cortisol levels at 3, 5, and 7 d after weaning than CS lambs (P<0.001). The CS lambs had higher body weight during the first 4 weeks after weaning than SCD lambs (P<0.001). The weaning method had no effect on scrotal circumference, sexual behavior, and semen quality traits, except for progressive sperm motility, being better for the lambs that were completely separated (P<0.05). The results from this study show that complete separation of lambs and ewes at weaning is an effective method to reduce lamb stress and improve lamb growth after weaning, but it did not have long-term effects on sexual behavior and semen quality of Saint Croix male lambs.

The South-Central region of Mexico has experienced a sizeable introduction of purebred horses for recreational aims. A study was designed to assess effective population sizes and genetic diversity and to verify the genetic integrity of four horse breeds. Using a 12-microsatellite panel, Quarter Horse, Azteca, Thoroughbred and Creole (CRL) horses were sampled and analysed for diversity and genetic structure. Genetic diversity parameters showed high numbers of heterozygous horses but small effective population sizes in all breeds. Population structure results suggested some degree of admixture of CRL with the other reference breeds. The highly informative microsatellite panel allowed the verification of diversity in introduced horse populations and the confirmation of small effective population sizes, which suggests a risk for future breed integrity.

Pelibuey sheep is the main breed in the tropical and subtropical regions of Mexico, and high demand of sheep meat has favored the finishing of lambs in feedlots with diets containing high levels of grains. The objective of this study was to evaluate the effects of exogenous enzymes (EE) and application method on nutrient intake and digestibility and performance of growing Pelibuey lambs. Treatments were based on comparison of two different methods of adding an enzyme product (sprayed on the total mixed ration or applied orally to the lambs) versus control treatment (no added enzyme). Twenty-one Pelibuey lambs, weighing 15.7 kg (SD = 1.8 kg) initial body weight, were individually housed in shaded pens and assigned randomly to one of the three enzyme treatments. At the end of study (lasting for 45 days), three lambs from each treatment were randomly selected and adapted to a pants and harness designed for fecal collection to measure nutrient digestibilities. Total body gain and average daily gain were affected (P < 0.05) by supplemental EE. The application method of EE had significant (P < 0.05) effect on FCE and FCR, but no effects were observed on nutrient intake. Supplemental EE did improve (P < 0.05) the digestibilities of dry matter, organic matter, neutral and acid detergent fiber, but no differences were observed in crude protein digestibility. The application method of EE had significant (P < 0.05) effect on the digestibility of acid detergent fiber. Supplemental EE can improve body weight gain and nutrient digestibilities without affecting nutrient intake in Pelibuey lambs, but the results of feed conversion efficiency and acid detergent fiber digestibility depend on the application method used of the EE

The objective of this study was to evaluate the effects of three fibrolytic enzyme products (cellulase (CEL), xylanase (XYL) and a 1:1 mixture of CEL and XYL (MIX)) at three dose levels (0, 1 and 3 μL/0.5 g DM) on the in vitro fermentation of a diet for growing lambs. Bottles were incubated for 96 h at 39 °C. A mathematical model was used to estimate the parameters describing the gas production (GP) curve (b, c and L). Dry matter degradability (DMD) and fibre (NDFD and ADFD) degradability were determined at the end of the incubation period. Metabolisable energy (ME) and short chain fatty acids (SCFA) were calculated at 24 h of incubation. The asymptotic GP (parameter b) was affected (p < 0.02) by enzyme product and dose level, with a significant linear response (p < 0.05). Dose level affected ME and SCFA with a significant linear (p < 0.05) and quadratic (p < 0.01) response. The interaction between enzyme product and dose level was significant (p < 0.05) for cumulative GP up to 72 and 96 h of incubation, pH, ADFD and DMD. The results suggest that application of exogenous cellulases has the potential to alter asymptotic GP and degradability of ADF and DM of a diet for growing lambs, but most of the results depend on the interaction between enzyme product and dose level. Future studies are required to determine the ideal combination between enzyme product and dose level for optimal degradation of ruminant feeds.

The aim of this study was to determine the semen quality, sexual behaviour and testosterone (T) levels in Saint Croix rams under semi-desert climate conditions. Sixteen rams (70.6 ± 12.5 kg; 24.1 ± 0.3 months old) were randomly divided into a grazing group (GG, n = 8) and a supplemented group (supplemented individually with 1 kg.d −1 of concentrate (156 g CP.kg −1 DM and 2.5 Mcal EM.kg −1 DM). SG, n = 8). Each group grazed on buffel, grass. Every two weeks, semen was collected, and sexual behaviour traits were evaluated. SG rams had greater body weight (P < 0.0001) and greater semen quality than the GG rams. SG rams had greater values for reaction time and lateral approaches than GG rams (P < 0.0001). No interaction was found between treatment and month for T concentration (P < 0.05); the SG rams had greater values during most of the months, but GG rams had greater values during September. Month had a significant effect on T concentration (P < 0.05) with the highest values in autumn. It can be concluded that Saint Croix rams are able to adapt to adverse environmental conditions and that supplementary feed prior to the mating season improves ram sexual behaviour.

Forty-five Pelibuey sheep were experimentally infested with nematodes to evaluate the effect of three free condensed tannin (FCT) levels of Lysiloma acapulcensis on fecal egg counts (FECs), packed cell volumes (PCV), ocular mucosa colors (OMC), average daily gain (ADG), and adult nematode count. Five treatments were used: 12.5, 25.0, and 37.5 mg of FCT kg −1 of body weight (BW); sterile water (control); and ivermectine (0.22 mg kg −1 of BW) as chemical group. The data were processed through repeated measurement analysis. Even though the three FCT doses decreased ( P  < 0.05) the FEC, the highest reduction was obtained with 37.5 mg kg −1 of BW. No differences were observed in PCV and OMC. Higher ADG ( P  < 0.05) was observed with 37.5 mg kg −1 of BW of FCT. The count of adult nematodes (females and males) in the higher dose of FCT was similar to chemical treatment. Dose of 37.5 mg kg −1 of BW decreased the parasite infection and improved the lamb performance. Therefore, this dose could be used as a nutraceutic product in sheep production.

Micromineral elements have a fundamental participation in the processes of organogenesis and fetal development. The objective of this study was to assess the effect of selenium (Se) injection in pregnant female rabbits, during organogenesis or rapid fetal growth, on the productive performance of their progeny. An experiment was carried out with 30 New Zealand female rabbits, with an average age of 6 months. At the end of mating (day 0), using a randomized complete design, the female rabbits were distributed into three experimental groups, which were assigned to the following treatments: Control, female rabbits were injected intramuscularly (IM) with 0.5 ml of saline on days 13 and 23 of gestation; Early administration, female rabbits that were injected IM with Se (0.10 mg/kg BW) on day 13 of gestation (organogenesis) and 0.5 ml of saline on day 23 of gestation; and Late administration, female rabbits that were injected IM with 0.5 ml of saline on day 13 of gestation and Se (0.10 mg/kg BW) on day 23 of gestation (rapid fetal growth). No differences were found on kindling performance of dams and pre-weaning growth of rabbit offspring. However, an injection of Se to pregnant rabbits affected the growth and development of their progeny, with the treatment leading to changes in the yield of some carcass traits (forelimb weight and forelimb muscle weight) and weights of some organs (liver, lungs, and spleen). The Se treatment (both early and late) also resulted in lower concentrations of glucose, triglycerides, and cholesterol when compared to the control group. These effects were different when Se injection was performed during organogenesis or rapid fetal development. The results from this study suggest that there are beneficial effects of gestational Se injection of rabbit dams on important productive traits of their progeny.