I.V Nsahlai

Reproductive performance of South African indigenous goats inoculated with DHP-degrading rumen bacteria and maintained on Leucaena leucocephala/grass mixture and natural pasture.

This study examined the reproductive performance of dihydroxy pyridone (DHP)-inoculated South African indigenous (SAIG) female goats maintained on two dietary treatments: (i) Leucaena leucocephala/grass mixture and (ii) natural pasture prior to conception, and during gestation. Leucaena leucocephala/grass mixture was nutritionally superior (crude protein and mineral elements) than the natural pasture. The average daily gain, products of pregnancy and foetal development in gravid goats raised on leucaena/grass mixture were significantly (P<0.03, P<0.009 and P<0.005, respectively) higher than those raised on natural pasture. Conception rate of goats fed natural pasture was higher than the band fed Leucaena leucocephala/grass mixture. Leucaena/grass mixture fed goats had kids that were heavier at birth than their counterparts on natural pasture. Pre-weaning kid mortality over the period of study was significantly (P<0.01) higher in the Leucaena leucocephala/grass mixture treatment. Colostrum from kidded goats fed leucaena was viscous and difficult to sample. The absence of mimosine toxicity symptoms suggests a possibility of safe use of leucaena as a feed resource to DHP-inoculated SAIG.

Feed intake and dietary preferences of sheep and goats offered hay and legume-tree pods in South Africa

Two experiments were designed to investigate the effect of legume tree-pods and ensiling on the intake and relative palatability of six feeds by goats and sheep. In the first experiment, the feeds offered were pasture hay (Themeda triandra), alfalfa (Medicago sativa), pods of Acacia sieberiana, Acacia nilotica and Leucaena leucocephala. In the second, silage from the pods of A. sieberiana was included as the sixth feed in order to examine the effect of ensiling on intake and palatability since this process was devised as a means of detoxifying cyanogenic glocosides known to be present in the leaves and pods of this species. Intake (Ti) and relative palatability (Pi) were determined using 3 goats and 3 sheep in each experiment. Since the feeds had different dry matter contents, intake was expressed as a ratio of the quantity offered (Ti/Ai). Using the hay offered (A1) and intake (T1), as standard, relative palatability indices were calculated as Pi = (Ti/Ai)/(T1/A1) where i represented the other feeds. In experiment 1, goats consumed more hay than alfalfa or pods. Sheep consumed more leucaena than all the other feeds. In experiment 2, the intake of all feeds except nilotica increased over time. Hay and leucaena had the highest Pi for goats and sheep, respectively, in experiment 1. In experiment 2, silage from pods of A. sieberiana had the highest Pi while the ranking for goats remained unchanged. The nilotica meal had the lowest Pi in both experiments. Pi was affected (p > 0.0001) only by feed type in experiment 1 but in experiment 2, feed type, animal species and weight significantly (p > 0.01) affected Pi. The results show that the pods of L. leucocephala and A. nilotica were the most and least preferred by goats and sheep, respectively, and that ensiling significantly improved the intake and palatability of the pods of A. sieberiana. However, some feeds that are least preferred in times of abundance and variety could be relished during periods of scarcity and severe feed shortages, based on animal survival instinct.

Field activities and blood profile of pregnant South African indigenous goats after receiving dihydroxy pyridone-degrading rumen bacteria and grazing Leucaena leucocephala-grass or natural pastures

Twenty-four multiparous female South African indigenous goats were used. Once a week during the 2nd (weeks 8, 11 and 14) and 3rd (weeks 18, 19 and 20) trimesters, between 08.00 and 15.00 h, four females per treatment were randomly selected and observed every 1 min for time spent grazing, browsing, ruminating and idling. Blood samples were taken once a week during the 2nd (weeks 8, 11 and 14) and 3rd (weeks 18, 19, 20 and 21) trimesters for measurements of some mineral elements and protein metabolites. Goats on natural pasture (NP) grazed 54.8 min (P < 0.001) more and browsed 53 min (P < 0.001) less than goats on Leucaena leucocephala-grass pasture (LGP) during the 2nd trimester. During the 3rd trimester, goats on NP treatments grazed and idled more (24.7 min, P = 0.004; 15.8 min, P = 0.044, respectively) but ruminated less (-24.1 min, P < 0.001) than LGP goats. Time allotted to each field activity by the goats on both treatments within trimester seemed to be dependent on forage species composition while activity between trimesters was possibly influenced by seasons, plant type, herbage quantity, environment and quality, and changes in stage of gestation of the goats. Blood Mg level on NP was higher (P = 0.051) than on LGP during the 2nd trimester while blood Cu and albumin contents on LGP were significantly higher (P = 0.029 and 0.022, respectively) than on NP during the 3rd trimester. Furthermore, blood concentrations of the haematological parameters (except serum protein) on both treatments were within the normal range for goats in the tropics and subtropics and perhaps explain the absence of mineral and nutrient deficiency symptoms. The absence of visible symptoms of mineral deficiency and mimosine toxicity in LGP goats can be attributed to the transfer of DHP-degrading rumen bacteria. The bacteria effectively detoxified mimosine and its metabolites, thereby overcoming chelating tendency of mimosine and its metabolites. Mimosine-susceptible pregnant SAIG can be safely grazed on LGP once their rumen is completely colonized by the DHP-degrading rumen bacteria (Synergistes jonesii).

The effects of Leucaena leucocephala on semen quality, fertility and reproductive performance of dihydroxy pyridone-adapted South African Nguni goats

The effects of feeding Leucaena leucocephala on semen quality and fertility were examined using four dihydroxy pyridone (DHP)-adapted (21.0, 26.5, 27.0 and 31.0 kg) and four DHP-unadapted (28.0, 31.0, 40.0 and 44.0 kg) South African indigenous Nguni bucks (mature male goats). The DHP-adapted bucks were assigned to air-dried Leucaena leucocephala forage (LL; Leucaena group) while the unadapted ones were maintained on a cereal-based concentrate diet (C; concentrate group) containing 122 g crude protein (CP)/kg over an 84-day period. Buck semen samples were collected on days 0 and 77 of the study. On the last day of the study (day 84), bucks in the Leucaena group were divided into two equal subgroups; a subgroup was assigned to Leucaena leucocephala-grass pasture (LGP) with ten does (mature female goats) while the second subgroup was assigned to natural pasture (NP) with nine does. Similarly, the two concentrate subgroups were separately assigned to mate nine and ten does on LGP and NP plots, respectively. The proportions of normal semen on both groups were not significantly different. However, semen quality on LL treatment increased significantly (P = 0.004) between days 0 and 77 and probably explains the significant (P < 0.01) difference between the fertility rates of bucks on both treatments. There was no evidence that feeding LL was detrimental to semen quality and fertility of bucks and to conception among females mated by the bucks fed the forage; perhaps due to the fact that the bucks had adapted to DHP as a result of the DHP-degrading rumen bacteria (Synergistes jonesii) that were transferred to them by the does. Synergistes jonesii is known to be capable of detoxifying mimosine and its toxic metabolites to innocuous compounds.

Seasonal variation in forage quality and mimosine contents of two varieties of Leucaena leucocephala

Seasonal variation in forage quality and mimosine contents of two varieties (cultivars Cunningham and Spectra) of Leucaena leucocepha/a were evaluated. Cultivar (cv.) Cunningham was available throughout summer, autumn, winter and spring seasons while cv. Spectra was available during summer, winter and spring seasons. Differences in crude protein (CP) and mimosine contents of young Cunningham and Spectra leaves were not significant. Also, difference in mimosine contents of mature leaves of both cultivars were not significantly different. But mean CP content of mature Spectra leaves was significantly higher (24.9 vs 18.7%, p = 0.023) than that of leaves of mature Cunningham. Mean P content of young Spectra leaves was significantly higher (1.6 vs 2.10gkg−1, p = 0.046) than that of young Cunningham leaves but mean Cu content of young Cunningham leaves was higher (10.5 vs 9.0mgkg−1, p = 0.06) than that of young Spectra leaves. Mature leaves of cv. Spectra also had higher P content (2.3 vs 1.6gkg−1, p = 0.06), but lower Ca (20.8 vs 30.5gkg−1, p = 0.06) and Mg (5.6 vs 7.6gkg−1, p = 0.06) contents than those of mature Cunningham leaves, Apart from CP, fat and mimosine, other analysed constituents increased with plant maturity.